NGC 2240

NGC 2240 is an open cluster in the constellation Auriga. It was discovered by William Herschel on January 3, 1786, and is located about 5.1 thousand light-years away.


Nu Fornacis

Nu Fornacis, Latinized from ν Fornacis, is a single, variable star in the southern constellation of Fornax. It is blue-white in hue and faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.69. This body is located approximately 370 light years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +18.5 km/s. It is a candidate member of the Pisces-Eridanus stellar stream, which suggests an age of 120 million years or less.
This object is an Ap star with a stellar classification of B9.5IIIspSi matching a late B-type giant star. The 'Si' suffix indicates an abundance anomaly of silicon. It is an Alpha2 Canum Venaticorum variable that ranges from magnitude 4.68 down to 4.73 with a period of 1.89 days – the same as its rotational period. It is 3.65 times as massive and 245 times as luminous as the Sun, with 3.44 times the Sun's diameter.


DY Pegasi

DY Pegasi, abbreviated DY Peg, is a binary star system in the northern constellation of Pegasus. It is a well-studied SX Phoenicis variable star with a brightness that ranges from an apparent visual magnitude of 9.95 down to 10.62 with a period of . This system is much too faint to be seen with the naked eye, but can be viewed with large binoculars or a telescope. Based on its high space motion and low abundances of heavier elements, it is a population II star system.
Observation history.
The variability of this star was first reported by Otto Morgenroth in 1934, and the first light curves of its photometric behavior were constructed by A. V. Soloviev in 1938. This curve showed a rapid increase of 0.7 in magnitude followed by a slower decline. It was found to be an intrinsic variable with an "ultra-short" period of 105 minutes. The 'b-v' color index of the star was found to vary with each cycle, corresponding to a change in spectral type from A7 at maximum to F1 at minimum. Direct observation of spectra showed a variation from A3 to A9. Evidence was found of small variations in the light curve between each cycle.
By 1972, it was widely regarded as a dwarf cepheid; a Delta Scuti variable. However, some astronomers classed it as a short-period RRs Lyrae variable. Photometric observations of DY Peg in 1975 by E. H. Geyer and M. Hoffman showed non-periodic changes to the light curve that suggested an overtone pulsation. A frequency analysis of observations made by A. Masani and P. Broglia in 1953 strengthened the evidence that DY Peg is a double mode cepheid, showing a fundamental pulsation and a weaker first overtone with a period ratio of 0.764. By 1982, similarities with SX Phoenicis had been found, with both showing comparable drifts in their beat periods. Application of the Baade-Wesselink method provided a preliminary distance estimate to DY Peg of .
In 2003, J. N. Fu and C. Sterken suggested that much of the long-term trend in variability period changes could be explained by a highly-eccentric orbital model, although it was not deemed a complete solution since some small residuals remained from the period 1930–1950. They computed a preliminary orbital period of with an eccentricity of . L.-J. Li and S.-B. Qian in 2010 found a mass estimate of the secondary in the range of 0.028 to , which suggests the companion may be a brown dwarf.
Properties.
A 2020 analysis of data collected by the AAVSO found three independent frequencies in the variability of the visible component. The primary and secondary modes are radial pulsations with 13.71249 and 17.7000 cycles per day, respectively, while a newly discovered non-radial mode has a frequency of 18.138 cycles per day. Consistent with being a population II star, it has a low metallicity. The stellar class ranges from A3 to F1 over each cycle, and the radius of the star varies by 3.5%. To explain certain discrepant properties of the system, H.-F. Xue and J.-S. Niu proposed that the primary may be accreting mass from an orbiting dust disk. This is conjectured to be leftover material from a white dwarf companion as it passed through the asymptotic giant branch.
DY Pegasi has been classified as a SX Phoenicis variable on the basis of its low metallicity. However, a 2014 study by S. Barcza and J. M. Benkő found a much higher general abundance of heavy elements with [M/H] = dex, approaching solar in composition. (This notation indicates the base-10 logarithm of the ratio of "metals" 'M' to hydrogen 'H', compared to the same abundances in the Sun. A value of 0.0 is solar.) They proposed that this may instead be a high amplitude Delta Scuti variable. The short period of this variable rules it out as an RR Lyrae variable.
The properties of DY Pegasi are uncertain due to the presence of an unknown companion, but it appears to lie close to the main sequence at the red (cool) edge of the instability strip. However, it has also been treated as a possible RR Lyrae variable which would be a horizontal branch star. As an old low-metallicity SX Phoenicis variable, it is very similar to blue stragglers, which are formed from stellar mergers or mass transfer in binary systems.


Rho Cassiopeiae

Rho Cassiopeiae (; ρ Cas, ρ Cassiopeiae) is a yellow hypergiant star in the constellation Cassiopeia. It is about from Earth, yet can still be seen by the naked eye as it is over 300,000 times brighter than the Sun. On average it has an absolute magnitude of −9.5, making it visually one of the most luminous stars known. Its diameter measures between 400 and 500 times that of the Sun, approximately 627,000,000 kilometers, or about twice the size of the Earth's orbit.
Rho Cassiopeiae is a single star, and is categorized as a semiregular variable. As a yellow hypergiant, it is one of the rarest types of stars. Only a few dozen are known in the Milky Way, but it is not the only one in its constellation which also contains V509 Cassiopeiae.
Observation.
The Bayer designation for this star was established in 1603 as part of the "Uranometria", a star catalog produced by Johann Bayer. The star catalog by John Flamsteed published in 1712, which orders the stars in each constellation by their right ascension, gave this star the Flamsteed designation 7 Cassiopeiae.
Rho Cas was first described as variable in 1901. It was classified only as "pec." with a small but definite range of variation. Its nature continued to be unclear during the deep visual minimum in 1946, although it was presumed to be related to the detection of an expanding shell around the star. The spectrum developed lower excitation features described as typical of an M star rather than the previous F8 class. The nature of Rho Cas was eventually clarified as a massive luminous unstable star, pulsating and losing mass, and occasionally becoming obscured by strong bouts of mass loss.
Rho Cas usually has an apparent magnitude near 4.5, but in 1946 it unexpectedly dimmed to 6th magnitude and cooled by over 3,000 Kelvin, before returning to its previous brightness. A similar eruption was recorded in 1893, suggesting that it undergoes these eruptions approximately once every 50 years. This happened again in 2000–2001, when it was observed by the William Herschel Telescope.
In 2013, a shell ejection produced dramatic spectral changes and a drop of about half a magnitude at visual wavelengths. Weak emission lines of metals and doubled H-α absorption lines were detected in late 2014, and unusual tripled absorption lines in 2017. The brightness peaked at magnitude 4.3 before fading to 5th magnitude. In 2018 it brightened again to magnitude 4.2.
The original Hipparcos parallax publication estimated Rho Cas at around 0.28 mas, which would have corresponded to a distance around 10,000 light years and would have made Rho Cas among the farthest stars visible to the naked eye. However, more recent publications estimate Rho Cas with a much larger parallax, corresponding to a much shorter distance.
Properties.
Rho Cassiopeiae is one of the most luminous yellow stars known. It is close to the Eddington luminosity limit and normally loses mass at around /yr, hundreds of millions of times the rate of the solar wind. Much of the time it has a temperature over 7,000 K, a radius around , and pulsates irregularly producing small changes in brightness. Approximately every 50 years it undergoes a larger outburst and blows off a substantial fraction of its atmosphere, causing the temperature to drop around 1,500 K and the brightness to drop by up to 1.5 magnitudes. In 2000–2001 the mass loss rate jumped to /yr, ejecting in total approximately 3% of a solar mass or 10,000 Earth masses. The luminosity remains roughly constant during the outbursts at , but the radiation output shifts towards the infra red.
Surface abundances of most heavy elements on Rho Cas are enhanced relative to the Sun, but carbon and oxygen are depleted. This is expected for a massive star where hydrogen fusion takes place predominantly via the CNO cycle. In addition to the expected helium and nitrogen convected to the surface, sodium is strongly enhanced, indicating that the star had experienced a dredge-up while in a red supergiant stage. Therefore, it is expected that Rho Cas is now evolving towards hotter temperatures. It is currently core helium burning through the triple alpha process.
 The relatively low mass and high luminosity of a post-red supergiant star is a source of instability, pushing it close to the Eddington Limit. However, yellow hypergiants lie in a temperature range where opacity variations in zones of partial ionisation of hydrogen and helium cause pulsations, similar to the cause of Cepheid variable pulsations. In hypergiants, these pulsations are generally irregular and small, but combined with the overall instability of the outer layers of the star they can result in larger outbursts. This may all be part of an evolutionary trend towards hotter temperatures through the loss of the star's atmosphere.
Naming.
ρ Cassiopeiae is a member of the Chinese constellation "Flying Serpent" (), in the Encampment mansion. In order, the 22 member stars are α and 4 Lacertae, π2 and π1 Cygni, stars 5 and 6, HD 206267, 13 and ε Cephei, β Lacertae, σ, ρ, τ, and AR Cassiopeiae, 9 Lacertae, 3, 7, 8, λ, ψ, κ, and ι Andromedae. Consequently, the Chinese name for ρ Cassiopeiae is (, )


Gamma Leonis

Gamma Leonis (γ Leonis, abbreviated Gamma Leo, γ Leo), also named Algieba , is a binary star system in the constellation of Leo. In 2009, a planetary companion around the primary was announced.
Nomenclature.
"γ Leonis" (Latinised to "Gamma Leonis") is the star's Bayer designation. The A and B components of the binary are often referred to as γ1 Leonis and γ2 Leonis respectively.
It also bore the traditional name "Algieba" or "Al Gieba", which originated from the Arabic "الجبهة" "Al-Jabhah", meaning 'the forehead' (despite this meaning, the star actually appears in the mane of Leo). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Algieba" for this star.
The star's traditional Latin name was "Juba". It is known as 軒轅十二 (the Twelfth Star of Xuanyuan) in Chinese (Xuanyuan is the name of the Yellow Emperor).
Algieba, along with Zeta Leonis, Regulus, Mu Leonis, Epsilon Leonis and Eta Leonis have collectively been called "the Sickle", which is an asterism that marks the head of Leo.
Stellar system.
The bright binary system in Leo with orange-red and yellow or greenish-yellow components is visible through a modest telescope under good atmospheric conditions. To the naked eye, the Algieba system shines at mid-second magnitude, but a telescope easily splits the pair. The brighter component has an apparent magnitude of +2.28 and is of spectral class K1-IIIbCN-0.5. The giant K star has a surface temperature of 4,470 K, a luminosity 180 times that of the Sun, and a diameter 23 times that of the Sun. The companion star has an apparent magnitude of +3.51 and belongs to the spectral class G7IIICN-I. The giant G star has a temperature of 4,980 K, a luminosity of 50 times that of the Sun, and a diameter 10 times that of the Sun. With angular separation of just over 4", the two stars are at least 170 AU apart (four times the distance between the Sun and Pluto), and have an orbital period of over 500 years. Because the orbital period is so long, only a fraction of the full path has been observed since discovery.
Both stars are almost certainly true giants, meaning that they have stopped fusing hydrogen to helium in their cores and have expanded to great proportions. Although there has been too little observation of their orbit to calculate their masses, comparison with evolutionary calculations suggests that each are about double the mass of the Sun. Originating from the same interstellar cloud some two billion years ago, the stars have iron contents about a third that of the Sun. It is hard to tell how far along they might be in their life cycle. They both may be fusing helium in their cores, or they could be giants in development, with quiet helium cores that are waiting to fire up. The chemical composition at the surface, which is influenced by age, suggests the former.
Variability.
γ Leonis is a suspected variable star, with a visual magnitude range of 1.84 to 2.03. It is not known which of the two components is variable. In 1959, the star was mistakenly published as an eclipsing binary due to a typographical error when referring to Y Leonis.
Planetary system.
On November 6, 2009, the discovery of a planetary companion around primary star γ1 Leonis (γ Leonis A) was announced. The radial velocity measurements suggest two additional periodicities of 8.5 and 1340 days. The former is likely due to stellar pulsation, whereas the latter could be indicative of the presence of an additional planetary companion with 2.14 Jupiter masses, moderate eccentricity (e=0.13) and located at 2.6 Astronomical Units away from the giant star. Nevertheless, the nature of such a signal is still unclear and further investigations are needed to confirm or rule out an additional substellar companion.


Kepler-20g

Kepler-20g is a non-transiting exoplanet orbiting Kepler-20. Its radius is about twice that of Earth, with a minimum mass Earth masses. Kepler-20g was announced on 24 August 2016.


P Eridani

p Eridani is a binary star system in the constellation of Eridanus (the River) whose distance from the Sun is approximately 26 light-years based upon parallax. It was found to be a double star in December 1825 by James Dunlop in Australia at his home at Paramatta, now spelt Parramatta. It is visible to the naked eye as a dim, orange-hued star. The system is moving further from the Earth with a heliocentric radial velocity of +23 km/s.
This system consists of a pair of near identical K-type main-sequence stars with stellar classifications of K2V. Component A has visual magnitude 5.87, while component B is magnitude 5.76. They orbit each other with a period of 475.2 years, an eccentricity of 0.53, and a semimajor axis of .
Naming.
The name "p Eridani", according to "Nature", p. 589 (19 April 1883) has been:
""... occasionally miscalled "6 Eridani", which would imply that it was one of Flamsteed's stars. Flamsteed, it is true has a star which he calls "6 Eridani". The designated letter 'p' was attached to a star by Lacaille in the catalogue at the end of his Coelum Australe Stelliferum. The number '6' is merely borrowed from Bode.""
The use of Bode numbers was commonly used in the early 19th century, but this antiquated system has now fallen into disuse for more than a century.


3 Centauri

3 Centauri is a triple star system in the southern constellation of Centaurus, located approximately 300 light years from the Sun. It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.32. As of 2017, the two visible components had an angular separation of along a position angle of 106°. The system has the Bayer designation k Centauri; "3 Centauri" is the Flamsteed designation. It is a suspected eclipsing binary with a variable star designation V983 Centauri.
The brighter member, designated component A, is a magnitude 4.52 chemically peculiar star of the helium-weak (CP4) variety, and has a stellar classification of B5 III-IVp. The spectrum of the star displays overabundances of elements such as nitrogen, phosphorus, manganese, iron, and nickel, while carbon, oxygen, magnesium, aluminium, sulfur, and chlorine appear underabundant relative to the Sun. Weak emission line features are also visible.
The magnitude 5.97 secondary, component B, is a single-lined spectroscopic binary star system with an orbital period of 17.4 days and an eccentricity of 0.21. The pair have an angular separation of . The visible component is a B-type main-sequence star with a class of B8 V.


Eta Virginis

Eta Virginis (η Virginis, abbreviated Eta Vir, η Vir) is a triple star system in the zodiac constellation of Virgo. From parallax measurements taken during the Hipparcos mission it is about from the Sun. It has a combined apparent visual magnitude of 3.89, bright enough to be seen with the naked eye in dark skies.
The system consists of a binary pair designated Eta Virginis A together with a third companion, Eta Virginis B. A's two components are themselves designated Eta Virginis Aa (officially named Zaniah , the traditional name of the system) and Ab.
Nomenclature.
"η Virginis" (Latinised to "Eta Virginis") is the system's Bayer designation. The designations of the two constituents as "Eta Virginis A" and those of "A's"components - "Eta Virginis Aa" and "Ab" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
It bore the traditional name "Zaniah" , derived from the Arabic زاوية "zāwiyah" "corner", the same source as "Zavijava" (Beta Virginis). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Zaniah" for the component Eta Virginis Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Thanih al Aoua", which was translated into Latin as "Secunda Latratoris", meaning "the second barker". This star, along with Beta Virginis (Zavijava), Gamma Virginis (Porrima), Delta Virginis (Minelauva) and Epsilon Virginis (Vindemiatrix), were "Al ʽAwwāʼ", "the Barker".
In Chinese, (), meaning "Left Wall of Supreme Palace Enclosure", refers to an asterism consisting of Eta Virginis, Gamma Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices. Consequently, the Chinese name for Eta Virginis itself is (, .), representing (), meaning "The Left Law Administrator". 左執法 (Zuǒzhífǎ), spelled "Tso Chih Fa" by R.H. Allen, means "the Left-hand Maintainer of Law"
Properties.
Eta Virginis looks single, but lunar occultations have shown it to be a very close triple star system consisting of two stars 0.6 AU apart, assuming a distance of 91 parsecs, with a third slightly more distant star. The inner pair is a spectroscopic binary that completes an orbit in 72 days. The inclination of this orbit was determined through interferometer observations to be 45.5°, allowing the masses of the two stars to be estimated. The primary star, Eta Virginis Aa, has a mass about 2.5 times the Sun's mass, while the secondary, Eta Virginis Ab, has 1.9 solar masses. The faint tertiary star, Eta Virginis B, orbits the inner group in a wider orbit over a period of 13.1 years.
Eta Virginis is 1.97 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. On October 12, 272 BC the ancient Greek astronomer Timocharis observed a conjunction of the star with Venus. The last occultation by a planet took place on September 27, 1843, also by Venus, which will occult it again on November 19, 2445.
Two degrees north-following of Eta Virginis is SS Virginis, a typical Cool Carbon Star and one of the most red colored stars in the equatorial sky.


HD 80230

HD 80230 is a single star in the southern constellation of Carina, near the northern constellation border with Vela. It has the Bayer designation "g Carinae", while "HD 80230" is the star's identifier in the "Henry Draper catalogue". This is a suspected variable star with a brightness that has been measured varying from magnitude 4.31 down to 4.35, both of which is bright enough for the star to be visible to the naked eye. The distance to this object is approximately 490 light years based on parallax, but it is drifting closer to the Sun with a radial velocity of −5 km/s.
This object is an aging red giant, currently on the asymptotic giant branch, with a stellar classification of M0.5IIIa. It is a mild barium star, showing trace enhancement of s-process elements in its spectrum. The star has 2.2 times the mass of the Sun and has expanded to 75 times the Sun's radius. It is radiating 1,172 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,904 K.


24 Persei

24 Persei is a star in the northern constellation of Perseus, located around 337 light years from the Sun. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.94. The object is moving closer to the Earth with a heliocentric radial velocity of −37 km/s.
This is an aging giant star with a stellar classification of K2 III, which indicates it has exhausted the hydrogen at its core and evolved away from the main sequence. It has 1.59 times the mass of the Sun and has expanded to about 24 times the Sun's radius. The star is radiating 185 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,391 K.


Gamma Hydrae

Gamma Hydrae (γ Hya, γ Hydrae) is a star in the equatorial constellation of Hydra. It has an apparent visual magnitude of 3.0, placing it second in brightness among the members of this generally faint constellation. Based upon parallax measurements made during the Hipparcos mission, this star is at a distance of around from Earth.
The stellar spectrum matches a stellar classification of G8 III, with the luminosity class of III indicating it has evolved into a giant star after exhausting the supply of hydrogen at its core. It has nearly three times the mass of the Sun and 16 times the Sun's radius. The star is radiating 115 times the Sun's luminosity from its outer atmosphere at an effective temperature of 5,019 K. This heat gives it the yellow glow of a K-type star. Despite having reached an advanced stage in its evolution, it is considerably younger than the Sun with an age of around 372 million years. This is because higher mass stars consume their nuclear fuel at a more rapid rate.
In culture.
γ Hya appears on the flag of Brazil, symbolising the state of Acre.


NGC 6400

NGC 6400 is an open cluster located in the constellation Scorpius. It is designated as II2m in the galaxy morphological classification scheme and was discovered by the Scottish astronomer James Dunlop on 13 May 1826. It is at a distance of 3,097 light years away from earth.<ref name="NASA/IPAC"></ref>


NGC 7047

NGC 7047 is an intermediate spiral galaxy located about 270 million light-years away in the constellation of Aquarius. NGC 7047 is also classified as a LINER-type galaxy. NGC 7047 has an estimated diameter of 127,350 light years. It was discovered by French astronomer Édouard Stephan on August 20, 1873. In 2009 a supernova was found in NGC 7047.
On January 1, 2009 a type II supernova designated as PTEo9cjq was discovered in NGC 7047.


LS 2883


Hen 2-47

Hen 2-47 is a young planetary nebula that lies about 6600 light years away from Earth in the southern constellation of Carina, the keel.
Hen 2-47 contains six lobes of gas and dust that suggest that the central star of the nebula ejected material at least three times in three different directions. During each ejection, the star fired off a narrow pair jets of gas pointed in opposite directions, eventually giving the nebula the shape it has at present.


V394 Aurigae

V394 Aurigae is a semi-regular variable star in the constellation Auriga. It varies between magnitudes 6.01 and 6.11. Located around 730 light-years distant, it shines with a luminosity approximately 1075 times that of the Sun and has a surface temperature of 3589 K.


NGC 3486

NGC 3486 is an intermediate barred spiral galaxy located about 27.4 million light years away in the constellation of Leo Minor. It has a morphological classification of SAB(r)c, which indicates it is a weakly barred spiral with an inner ring and loosely wound arms. This is a borderline, low-luminosity Seyfert galaxy with an active nucleus. However, no radio or X-ray emission has been detected from the core, and it may only have a small supermassive black hole with less than a million times the mass of the Sun.


Iota Lyrae

ι Lyrae, Latinised as Iota Lyrae, is a binary star in the northern constellation of Lyra. It is visible to the naked eye as a dim, blue-white hued star with an apparent visual magnitude that fluctuates around 5.22. This object is located approximately 950 light years distant from the Sun based on parallax, but is drifting nearer with a radial velocity of −26 km/s.
This is a wide binary system with a computed orbital period of 217 years and an eccentricity of 0.6. The primary component has a stellar classification of B6IV, matching a B-type subgiant star. It is a Be star, displaying emission lines in its spectrum, and is spinning rapidly with a projected rotational velocity of 224 km/s. The star ranges in brightness from magnitude 5.20 down to 5.27. It has five times the mass of the Sun and is radiating 1,349 times the Sun's luminosity from its photosphere at an effective temperature of 13,428 K.


NGC 6496

NGC 6496 is a globular cluster which is in the direction of the bulge and putative members of this subgroup, based on observations collected with the WFPC2 on board the Hubble Space Telescope. NGC 6496 was originally believed to be a member of the disc system of GC, but scientists questioned this classification. It was instead suggested that NGC 6496, together with two other clusters, NGC 6624 and NGC 6637, could be halo clusters with strongly inclined orbits. NGC 6496 lies in the Southern sky at RA=17:59:03.68 and Dec=-44:15:57.4.
The first CMD presented of NGC 6496 had photometry reaching 2 mag below the horizontal branch, disclosing for the first time the usual red arm of the metal-rich clusters. The extinction towards NGC 6496 is uncertain, with estimates ranging between E(B-V) = 0.09 and E(B-V) = 0.24.
The cluster has a relatively metal-rich composition of [Fe/H] = –0.46 dex and is of an open, uncroweded nature. Few attempts were made to find variable stars in NGC 6496. In one of the studies, thirteen variable stars were detected by Dr. Moe Abbas and Dr. Andrew Layden from Bowling Green State University.


Pi Geminorum

π Geminorum (Latinised as Pi Geminorum, abbreviated to π Gem or pi Gem) is a star located in the constellation Gemini, to the north of Castor. With an apparent visual magnitude of 5.14, it is faintly visible to the naked eye on a dark night. Based upon an annual parallax|shift of 4.93 mas, Pi Geminorum is located roughly 660 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.033 due to interstellar dust.
This is an evolved red giant star with a stellar classification of M1 IIIa. The measured angular diameter of this star is . At the estimated distance of this star, this yields a physical size of about 56 times the radius of the Sun. It is radiating roughly a thousand times the luminosity of the Sun from its outer atmosphere at an effective temperature of 3,900 K.
Unexpectedly for a red giant, Pi Geminorum was found to be an X-ray source during the ROSAT all-sky survey. The most likely source for this emission is an 11.4 magnitude companion star located at an angular separation of 21 arcseconds along a position angle of 214°. This star is suspected to be an astrometric companion of the primary component.
References.
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Beta Reticuli

Beta Reticuli (Beta Ret, β Reticuli, β Ret) is binary star system in southern constellation of Reticulum. It is visible to the naked eye with an apparent visual magnitude of +3.84. Based upon an annual parallax shift of 33.49 mas, it is located some 97 light years from the Sun.
This is a single-lined spectroscopic binary with an orbital period of 5.25 years and an eccentricity of 0.33. The primary, component A, is an evolved K-type giant star with a stellar classification of K0 IVSB:. It is between 5 and 6 billion years old, with 1.2 times the mass of the Sun and 9.3 times the Sun's radius. The companion, component B, is most likely a red dwarf with a classification in the range M0–M4.
During the mid-20th century, the Dutch-American astronomer Willem Jacob Luyten proposed that the G3V star HD 24293 formed a third component of this system, based upon similar proper motions. However, this was subsequently ruled out based on more accurate measurements, since their actual distances, radial velocities, and proper motions do not match.
Beta Reticuli is moving through the Galaxy at a speed of 69.2 km/s relative to the Sun. Its projected Galactic orbit carries it between 10,100 and 24,200 light years from the center of the Galaxy. Beta Reticuli came closest to the Sun 319,000 years ago when it had brightened to magnitude 2.98 from a distance of 67 light years.
Naming.
In Chinese caused by adaptation of the European southern hemisphere constellations into the Chinese system, (), meaning "Snake's Head", refers to an asterism consisting of β Reticuli and α Hydri. Consequently, β Reticuli itself is known as (, .)


HAT-P-9

HAT-P-9 is a magnitude 12 F star approximately 1500 light years away in the constellation Auriga. A search for a binary companion star using adaptive optics at the MMT Observatory was negative.
The star HAT-P-9 is named Tevel. The name was selected in the NameExoWorlds campaign by Israel, during the 100th anniversary of the IAU. The Hebrew word תֵבֵל "tevel" means "World" or "Universe".
Planetary system.
An exoplanet orbiting the star, HAT-P-9b, was discovered by the transit method on June 26, 2008.


53 Cancri

53 Cancri is a variable star in the zodiac constellation Cancer, located around 960 light years from the Sun. It has the variable star designation BO Cancri; "53 Cancri" is the Flamsteed designation. This object is a challenge to view with the naked eye, having an apparent visual magnitude around 6. It is around 960 light years away.
The star is moving further away from the Earth with a heliocentric radial velocity of +14 km/s. 53 Cancri is an aging red giant on the asymptotic giant branch and has a stellar classification of M3 III. It has expanded to 87 times the radius of the Sun, and its bolometric luminosity is over a thousand times higher than the Sun's at an effective temperature of .
53 Cancri is a semiregular variable that varies between magnitude 5.9 and 6.4 with a period of 27 days. There is a suspected second period of 270 days.


Lambda Capricorni

Lambda Capricorni, Latinized from λ Capricorni, is a solitary star in the southern constellation of Capricornus. It is faintly visible to the naked eye with an apparent visual magnitude of +5.56. Based upon an annual parallax shift of 11.58 mas as seen from the Earth, the star is located about 282 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.11 due to interstellar dust.
This is a white-hued A-type main sequence star with a stellar classification of A1 V. It is a magnetic Ap star, indicating the spectrum displays chemically peculiar features. The star has an estimated 2.50 times the mass of the Sun and about 2.2 times the Sun's radius. It is 155 million years old and is spinning rapidly with a projected rotational velocity of 192.5 km/s. Lambda Capricorni is radiating 45 times the Sun's luminosity from its photosphere at an effective temperature of 10,674 K.


Eta Draconis

Eta Draconis (η Draconis, abbreviated Eta Dra, η Dra) is a binary star in the northern circumpolar constellation of Draco. Despite having an apparent visual magnitude of only +2.73, it is the second-brightest star in this generally faint constellation. Based upon parallax measurements collected during the Hipparcos mission, this star is located at a distance of about from the Sun.
The two components are designated Eta Draconis A (also named Athebyne ) and B.
Nomenclature.
"η Draconis" (Latinised to "Eta Draconis") is the system's Bayer designation. The designations of the two components as "Eta Draconis A" and "B" derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Eta Draconis, together with Zeta Draconis, bore the traditional Arabic name الذئبين "al-dhiʼbayn", "the (two) wolves" (the Duo Lupi), lying in wait for the camel's foal, the little star Al Rubaʽ, protected by the Mother Camels.
In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Athebyne" (a rendering of "adh-dhiʼbayn") for the component Eta Draconis A on 5 September 2017. It approved the name "Aldhibah" (the female wolf) for Zeta Draconis A on the same date. Both are now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "Left Wall of Purple Forbidden Enclosure", refers to an asterism consisting of Eta Draconis, Iota Draconis, Theta Draconis, Zeta Draconis, Upsilon Draconis, 73 Draconis, Gamma Cephei and 23 Cassiopeiae. Consequently, the Chinese name for Eta Draconis itself is (, ), representing (), meaning "The Second Premier". Possibly, 少宰 (Shàozǎi) is westernized into "Hea Tsae" by R.H. Allen with meaning "the Lowest Steward" but it was for Theta Draconis.
Properties.
Eta Draconis A is a star with 2.55 times the mass of the Sun. The spectrum matches a stellar classification of G8 III, with the luminosity class III indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core. It reached this stage in only 550 million years because higher mass stars such as this consume the supply of hydrogen more rapidly than the Sun. The measured angular diameter of this star, after correction for limb darkening, is . At the estimated distance of Eta Draconis, this yields a physical size of about 11 times the radius of the Sun. From its extended envelope, it is radiating around 60 times the luminosity of the Sun at an effective temperature of 5,055 K, giving it the yellow glow of a G-type star.
Eta Draconis B is located at an angular separation of 5.1 arcseconds from the primary. This is an 8.8 magnitude K-type main sequence star with a stellar classification of K2 V. At the estimated distance of this star system, the two stars are separated by a physical distance of at least 140 AU and require at least a millennium to complete an orbit.
References.
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Omega Ophiuchi

Omega Ophiuchi, which is Latinized from ω Ophiuchi, is a single, variable star in the equatorial constellation of Ophiuchus, located just to the north of the ecliptic near the western constellation border with Scorpius. It is a white-hued star that is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.45. Parallax measurements indicate it lies at a distance of about 168.6 light years from the Sun. It is drifting further away with a radial velocity of +2.5 km/s.
This object is an Ap star with a stellar classification of ApSrEuCr, displaying strong abundance anomalies of the elements strontium, europium, and chromium. Abt and Morrell (1995) found a class of , showing further an A-type main-sequence star with a Ca II line (single-ionized calcium) having both sharp and broad components. It is an Alpha2 Canum Venaticorum variable, with its brightness ranging from magnitude 4.44 down to 4.51 over a period of 2.99 days. A strong magnetic field has been measured on the surface.
Omega Ophiuchi is around 860 million years old with a projected rotational velocity of 32.2 km/s and a rotation period of 2.3 days. It has 2.3 times the mass of the Sun and 3.0 times the Sun's radius. The star is radiating 35 times the luminosity of the Sun from its photosphere at an effective temperature of 8,150 K. It is a source of X-ray emission.


V533 Carinae

V533 Carinae (V533 Car, y Car, y Carinae) is a white A-type supergiant variable star with a mean apparent magnitude of +4.59 in the constellation Carina. It is over 10,000 light years from Earth.
Location.
V533 Carinae is found near the Carina Nebula on the edge of the constellation Carina towards Crux. It is a member of Collinder 240, a sparse open cluster sometimes considered to be a portion of the richer nearby cluster NGC 3572. Together with the small clusters Hogg 10 and 11, they are all part of the Carina OB2 stellar association.
V533 Carinae is the brightest star in the region. The other bright stars in NGC 3572 are hot young stars such as HD 97166 and all the clusters in the region are only a few million years old.
V533 Carinae is classified as a double star with the companion being a magnitude 11.5 star 21.7 arc-seconds away.
Variability.
V533 Carinae was one of many small amplitude variable stars detected from an analysis of Hipparcos photometry. It was granted its variable star designation in 1999 as a batch of 2,675 new variables. It is classified as an Alpha Cygni type variable and its brightness varies from magnitude +4.69 to +4.75 as measured on the Hipparcos photometric scale. A period of 1.58499 days and an average visual amplitude of 0.0146 magnitudes are quoted although the variations are not strictly regular.
Properties.
V533 Carinae is a bright supergiant with a luminosity around 100,000 times that of the sun. The temperature is over 8,000 K and the radius around . Its equatorial rotation is more than 15 times faster than the sun's.
Prior to 1971, it was always classified with an early or mid F-type spectral type, but since then has always been given a mid or late A class.


Nu Capricorni

Nu Capricorni (ν Capricorni, abbreviated Nu Cap, ν Cap) is a binary star in the southern constellation of Capricornus.
Attributes.
The star system is 6.6 degrees north of the ecliptic and so is within the margin of occultations of few if any planets but is well within that of the Moon The celestial latitude of either of the Alpha Capricorni main stars is about 6.93 degrees by comparison. The system is calculated to be 253 light-years from the Sun; it has a great proper motion.
The two components are designated Nu Capricorni A (formally named Alshat , the traditional name for the system) and B.
Nomenclature.
"ν Capricorni" (Latinised to "Nu Capricorni") is the system's Bayer designation. The designations of the two components as "Nu Capricorni A" and "B" derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
The system bore the traditional name "Alshat", from the Arabic الشاة "aš-šā[t]", meaning 'the sheep' that was to be slaughtered by the adjacent Beta¹ Capricorni (Dabih). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Alshat" for the component Nu Capricorni A on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
Properties.
The primary member, Nu Capricorni A, is a blue-white hued B-type main sequence or subgiant star with an apparent magnitude of +4.77. Its companion, Nu Capricorni B, is a magnitude 11.8 star at an angular separation of 54.1 arcseconds from the primary. Gaia Data Release 2 shows the companion to be much further away from Earth.


HE 2359-2844

HE 2359-2844 is a subdwarf located approximately 800 light years away in the constellation Sculptor, with a surface temperature of approximately . Along with stars HE 1256-2738 and LS IV-14 116, HE 2359-2844 forms a new group of star called heavy metal subdwarfs.
HE 2359-2844 contains very high levels of lead - 10,000 times more than the Sun. It also contains 10,000 times more yttrium and zirconium than the Sun. It is suggested that there is a lead layer above the star that is thick and that contains 100 billion tonnes of lead. Dr. Naslim Neelamkodan explained that "the heavy-metal stars are a crucial link between bright red giants, stars thirty or forty times the size of the Sun, and faint blue subdwarfs, stars one fifth the size, but seven times hotter and seventy times brighter than the Sun."


Beta Pyxidis

Beta Pyxidis (Beta Pyx, β Pyxidis, β Pyx) is a double star located in the southern constellation Pyxis. It has an apparent visual magnitude of 3.954, making it the second brightest star in that faint constellation.
Based upon parallax measurements, the star is an estimated 420 light-years (128 parsecs) from the Earth. The spectrum matches a bright giant or supergiant star of stellar classification G7Ib-II. The interferometer-measured angular diameter of this star is . At its estimated distance, this yields a physical size of about 28 times the radius of the Sun. The effective temperature of the star's outer envelope is about 5,400 K, giving it the characteristic yellow hue of a G-type star.
Beta Pyxidis has an unusually high rate of spin for an evolved star of this type, showing a projected rotational velocity of 11.8 km/s. One possible explanation is that it may have engulfed a nearby giant planet, such as a hot Jupiter.
In 2010, the star was among a survey of massive, lower effective temperature supergiants in an attempt to detect a magnetic field. This star may have a longitudinal magnetic field with a strength of less than a Gauss. It is a young disk star system with space velocity components, = . There is a magnitude 12.5 optical companion, located at an angular separation of 12.7 arcseconds and a position angle of 118° as of the year 1943.
Naming.
In Chinese, (), meaning "Celestial Dog", refers to an asterism consisting of β Pyxidis, e Velorum, f Velorum, α Pyxidis, γ Pyxidis and δ Pyxidis. Consequently, β Pyxidis itself is known as (, .)
References.
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57 Cygni

57 Cygni is a close binary star system in the constellation Cygnus, located about 530 light years from Earth. It is visible to the naked eye as a blue-white hued star with a baseline apparent visual magnitude of 4.80. The pair have a magnitude difference of 0.34. This system is moving closer to the Earth with a heliocentric radial velocity of −21 km/s.
This is a double-lined spectroscopic binary with an orbital period of 2.85 days and an eccentricity of 0.15. They show a steady change in their longitude of periastron, showing an apsidal period of . The system does not form an eclipsing binary, having the orbital inclination of around 48°. Both components are B-type main-sequence stars with a stellar classification of B5 V.


Kepler-67

Kepler-67 is a star in the open cluster NGC 6811 in the constellation Cygnus. It has slightly less mass than the Sun and has one confirmed planet, slightly smaller than Neptune, announced in 2013.


NGC 2467

 NGC 2467, nicknamed the "Skull and Crossbones Nebula," is a star-forming region whose appearance has occasionally also been likened to that of a colorful mandrill. It includes areas where large clouds of hydrogen gas incubate new stars. This region was one of the areas featured in the book "" by Terence Dickinson.
Discussion.
NGC 2467 had long been considered to be the nucleus of the Puppis I association. However, NGC 2467 does not represent a distinct open cluster; rather, it represents a superimposition of several stellar groups along the same approximate line of sight that have distinctly different distances and distinctly different radial velocities. One of these is a young and very distant group beyond Puppis OB2, while another, nearer group with later type stars lies at a similar distance as Puppis OB1.
The region is dominated by a massive young star, HD 64315 (annotated in Commons, below and left of center), of spectral type O6. Two stellar clusters also exist in the area, Haffner 19 (H19, annotated) and Haffner 18 (H18, annotated). H19 is a compact cluster containing a Strömgren sphere which is ionized by a hot B0 V type star. H18 contains a very young star, FM3060a (annotated), that has just come into existence and still surrounded by its birth cocoon of gas. The age of H19 is estimated to be 2 Myr, while the age H18 is somewhat controversial, some considering it to be as young as only 1 Myr. The field contains other early-type stars such as HD 64568 (annotated, upper right) whose relationship with the clusters is unclear.
The H II region of NGC 2467 has been the target of various investigations to elucidate the process of star formation. Unresolved questions include understanding the degree to which the stars already formed in such regions, especially the massive O or B stars, can affect the future formation of stars in the region: Do these pre-existing stars trigger the formation of others? One such investigation was conducted using the Spitzer Space Telescope, which discovered 45 young stellar objects (YSOs), or protostars, in the region during its "cold" mission, "i.e." before its supply of liquid helium ran out. The YSO's are mostly along the edge of the HII region. The concentrated distribution of these objects spatially correlated with the ionization fronts provides evidence for triggered star formation. The newly forming ptotostars are concentrated in areas where the shock front driven in advance of the ionization front compresses the molecular gas.
It has been estimated that H19, H18, and the S311 nebula (in which lies HD 64315) are about 6.4 kpc (20900 ly), 5.9 kpc (19200 ly), and 6.3 kpc (20500 ly) away, placing them in the Perseus Arm of the Milky Way. A significant discrepancy has existed between the distances to these features estimated kinematically "versus" distances estimated photometrically. Regardless of these discrepancies, H19 and H18 may be considered to be a binary cluster.


NGC 366

NGC 366 is an open cluster located in the constellation Cassiopeia. It was discovered on October 27, 1829 by John Herschel. It was described by Dreyer as a "cluster, small."


Lambda Pegasi

Lambda Pegasi (λ Peg, λ Pegasi) is a fourth-magnitude star in the constellation Pegasus.
λ Pegasi is a yellow giant with stellar classification G8II-III. With a mass of and radius that is , the star boasts a bolometric luminosity that is roughly . Its apparent magnitude was calibrated in 1983 at 3.96, yielding an absolute magnitude of -1.45. Parallax calculations place the star at a distance of roughly 112 parsecs from Earth, or 365 ± 10 light years away, about three times the distance of its line-of-sight double μ Pegasi.
In the constellation, Lambda and Mu lie to the southwest of Beta Pegasi, the nearest bright star.


Mu2 Octantis

Mu2 Octantis (μ2 Oct) is a binary star system of two G-type main-sequence stars. It shares the designation μ with μ1 Octantis, from which it is separated by 50 arcminutes.
The primary star (A) is HD 196067, whose data is in the starbox. The secondary star (B) is HD 196068 (HIP 102128, LTT 8160), another G-type main-sequence star with an apparent magnitude of 7.18. Its effective temperature 5997 K, and its mass is . The two are gravitationally bound and separated at 17 arcseconds in our sky, corresponding to 740 astronomical units (AU). The binary semimajor axis is 932 AU.
Planetary system.
From 1998 to 2012, the system was observed using the CORALIE instrument, at the ESO's La Silla Observatory.
In 2012, a long-period, wide-orbiting planet was deduced by radial velocity around HD 196067. This was published in November. The planet has been pulled to an eccentric orbit by the B star HD 196068.


Gliese 784

Gliese 784 is a single red dwarf star of spectral type M0V, located in constellation Telescopium, 20.1 light-years from Earth. It is much younger than Sun at 0.85 billion years.
History of observations.
Gliese 784 is known at least from 1900, when it was included in "Cordoba Durchmusterung (CD)" catalogue by John M. Thome. The corresponding designation is CD -45 13677.
Planetary System.
In June 2019 one planet candidate were reported in orbit around Gliese 784. Since 2020, the star is suspected to be surrounded by the disk of cold dust, but the signal may be also due to the background extragalactic source.


Mu Normae

μ Normae, Latinised as Mu Normae, is a blue supergiant star of spectral type O9.7 Iab, located in the constellation of Norma.
It shines as bright as 339,000 suns and is weighs 40 solar masses. It varies in visual magnitude between 4.87 and 4.98, and is suspected of being an Alpha Cygni variable, which are named after Deneb.
It is in the same direction and at the same distance as the faint open cluster NGC 6169, although it is brighter than the combined magnitude of all the other stars in the cluster. It was considered the prototype of the μ Normae class of open clusters by Collinder.


83 Leonis

83 Leonis, abbreviated 83 Leo, is a binary star system approximately 59 light-years away in the constellation of Leo (the Lion). The primary star of the system is a cool orange subgiant star, while the secondary star is an orange dwarf star. The two stars are separated by at least 515 astronomical units from each other. Both stars are presumed to be cooler than the Sun.
In 2005, an extrasolar planet was confirmed to be orbiting the secondary star within the system.
In 2010, the second planet was discovered.
Stellar system.
The primary component, 83 Leonis A, is a 6th magnitude star. It is not visible to the unaided eye, but easily visible with small binoculars. The star is classified as a subgiant, meaning that it has ceased fusing hydrogen in its core and started to evolve towards red gianthood.
The secondary component, 83 Leonis B, is an 8th magnitude orange dwarf, somewhat less massive (0.88 MSun), smaller and cooler than the Sun. It is visible only with binoculars or better equipment. Components A and B share common proper motion, which confirms them as a physical pair. The projected separation between the stars is 515 AU, but the true separation may be much higher.
There is yet another, magnitude 14.4 component listed in the Washington Double Star Catalog. However, this star is moving into a different direction and is therefore not a true member of the 83 Leonis system.
Planetary system.
Planet 83 Leonis Bb was discovered in Jan 2005 by the California and Carnegie Planet Search team, who use the radial velocity method to detect planets. The planet's minimum mass is less than half of the mass of Saturn. It orbits very close to the star, completing one orbit in about 17 days.
In 2010, the second planet 83 Leonis Bc was discovered, and discovery retracted in 2016.


75 Cancri

75 Cancri (abbreviated to 75 Cnc) is a binary star in the constellation of Cancer. The system is located about 102 light-years (31 parsecs) away, based on its stellar properties.
75 Cancri is a spectroscopic binary, which means the two stellar components are too close to be resolved, but periodic Doppler shifts in their spectra indicate orbital motion. In this case, light from both stars can be detected, and it is a double-lined spectroscopic binary. The orbital period of the system is 19.41 days, and the eccentricity of the system is 0.19494, implying a slightly elliptical orbit. The primary has a mass of , and is a G-type main-sequence star or subgiant. The secondary is less massive, at .


27 Arietis

27 Arietis is a binary star system in the northern constellation of Aries. "27 Arietis" is the Flamsteed designation. It is a dim, yellow-hued star that is close to the lower limit of what can be viewed with the naked eye, having an apparent visual magnitude is 6.21. The annual parallax shift of corresponds to a physical distance of approximately from Earth. It is advancing closer to the Earth with a heliocentric radial velocity of −122.7 km/s, and may come as close as in around 643,000 years.
This appears to be a single-lined spectroscopic binary system with an orbital period of 130.7 days and an eccentricity of 0.366. It has an ""a" sin "i"" value of , where "a" is the semimajor axis and "i" is the inclination to the line of sight from the Earth. This value provides a lower bound on the actual semimajor axis. The visible component has a stellar classification of , displaying mixed spectral traits of an evolved subgiant and a giant star, with a strong underabundance of iron. The CN bands of this star are very weak.


Gamma Canis Minoris

Gamma Canis Minoris (γ Canis Minoris) is a binary star system in the equatorial constellation Canis Minor. Its orange colour is obvious when seen through binoculars. The system is visible to the naked eye with a combined apparent visual magnitude of +4.33. Based upon an annual parallax shift of 10.25 mas as seen from Earth, this system is located about 320 light years from the Sun.
This spectroscopic binary star system has an orbital period of 389.31 days, a semimajor axis of 1.48 AU, and an eccentricity of 0.2586. Their variable radial velocity was discovered by H. M. Reese in 1902 at Lick Observatory. Both components are evolved, K-type giant stars, most likely on their first ascent along the red giant branch. The primary, component A, has a stellar classification of K4 III while the secondary, component B, may be K1: III.


List of stars in Telescopium

This is the list of notable stars in the constellation Telescopium, sorted by decreasing brightness.


Zeta Ophiuchi

Zeta Ophiuchi (ζ Oph, ζ Ophiuchi) is a star located in the constellation of Ophiuchus. It has an apparent visual magnitude of 2.57, making it the third-brightest star in the constellation. Parallax measurements give an estimated distance of roughly from the Earth.
Properties.
ζ Ophiuchi is an enormous star with more than 19 times the Sun's mass and eight times its radius. The stellar classification of this star is O9.5 V, with the luminosity class of V indicating that it is generating energy in its core by the nuclear fusion of hydrogen. This energy is being emitted from the outer envelope at an effective temperature of 34,000K, giving the star the blue hue of an O-type star. It is rotating rapidly and may be close to the velocity at which it would begin to break up. The projected rotational velocity may be as high as and it may be rotating at a rate of once per day.
This is a young star with an age of only three million years. Its luminosity is varying in a periodic manner similar to that of a Beta Cephei variable. This periodicity has a dozen or more frequencies ranging between 1–10 cycles per day. In 1979, examination of the spectrum of this star found "moving bumps" in its helium line profiles. This feature has since been found in other stars, which have come to be called ζ Oph stars. These spectral properties are likely the result of non-radial pulsations.
This star is roughly halfway through the initial phase of its stellar evolution and will, within the next few million years, expand into a red supergiant star wider than the orbit of Jupiter before ending its life in a supernova explosion, leaving behind a neutron star or pulsar. From the Earth, a significant fraction of the light from this star is absorbed by interstellar dust, particularly at the blue end of the spectrum. In fact, were it not for this dust, ζ Ophiuchi would shine several times brighter and be among the very brightest stars visible.
X-ray emissions have been detected from Zeta Ophiuchi that vary periodically. The net X-ray flux is estimated at 1.2 × 1024 W. In the energy range of 0.5–10 keV, this flux varies by about 20% over a period of 0.77 days. This behavior may be the result of a magnetic field in the star. The measured average strength of the longitudinal field is about .
ζ Ophiuchi is moving through space with a peculiar velocity of 30 km s−1. Based upon the age and direction of motion of this star, it is a member of the Upper Scorpius sub-group of the Scorpius-Centaurus Association of stars that share a common origin and space velocity. Such runaway stars may be ejected by dynamic interactions between three or four stars. However, in this case the star may be a former component of a binary star system in which the more massive primary was destroyed in a Type II supernova explosion. The pulsar PSR B1929+10 may be the leftover remnant of this supernova, as it too was ejected from the association with a velocity vector that fits the scenario.
Due to the high space velocity of Zeta Ophiuchi, in combination with high intrinsic brightness and its current location in a dust-rich area of the galaxy, the star is creating a bow-shock in the direction of motion. This shock has been made visible via NASA's Wide-field Infrared Survey Explorer. The formation of this bow shock can be explained by a mass loss rate of about times the mass of the Sun per year, which equals the mass of the Sun every nine million years.
Traditional names.
ζ Ophiuchi was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of "al-Nasaqān" "the Two Lines", along with α Serpentis (Unukalhai), δ Ser (Qin, Tsin), ε Ser (Ba, Pa), δ Ophiuchi (Yed Prior), ε Oph (Yed Posterior) and γ Oph (Tsung Ching).
According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "al-Nasaq al-Yamānī" or Nasak Yamani was the title for two stars :δ Serpentis as "Nasak Yamani I" and ε Ser as "Nasak Yamani II" (exclude this star, α Ser, δ Ophiuchi, ε Oph and γ Oph)
In Chinese, (), meaning "Right Wall of Heavenly Market Enclosure", refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of ζ Ophiuchi, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, α Serpentis, δ Serpentis, ε Serpentis, δ Ophiuchi and ε Ophiuchi. Consequently, the Chinese name for ζ Ophiuchi itself is (, ), represent the state Han (韓), together with 35 Capricorni in "Twelve States" (asterism).


HD 224693

HD 224693 is a star in the equatorial constellation of Cetus, and is positioned near the western constellation border with Aquarius. It can be viewed with a small telescope but is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.23. Based on parallax measurements, the object is located at a distance of approximately 306 light years from the Sun. It is drifting further away with a radial velocity of 1.5 km/s.
The star HD 224693 is named Axólotl. The name was selected in the NameExoWorlds campaign by Mexico, during the 100th anniversary of the IAU. Axólotl means water animal in the native Nahuatl language, which is an amphibious species from the basin of Mexico.
This is an ordinary G-type main-sequence star with a stellar classification of G2V. However, in 2006, Johnson and associates assigned it a class of G2 IV, suggesting it is instead an evolving subgiant star. It is about three billion years old and chromospherically quiet, with a projected rotational velocity of 4.2 km/s. The star is metal rich, showing a higher abundance of elements other than hydrogen and helium when compared to the Sun. It has 1.3 times the mass of the Sun and 1.8 times the Sun's radius. The star is radiating 3.78 times the luminosity of the Sun from its photosphere at an effective temperature of 5,971 K.
In 2006, an extrasolar planet was discovered orbiting HD 224693 by the Keck telescope using radial velocity measurements. A preliminary search for transits using photometric data from Fairborn Observatory was inconclusive because data around the predicted time of transit was too sparse to rule out possible transits.


Eta Orionis

Eta Orionis (η Orionis) is a multiple star in the constellation Orion. It lies a little to the west of Orion's belt between Delta Orionis and Rigel, being closer to Delta Orionis than to Rigel. It lies at a distance of around 1,000 light years from Earth and is part of the Orion OB1 association.
System.
Eta Orionis is listed in multiple star catalogues as having two companions: a bright component B less than 2" away; and a faint component C nearly 2' away. The two are estimated to orbit every 1.8 thousand years.
The primary star, Eta Orionis A, is itself a spectroscopic triple star, known from multiple spectral lines with varying radial velocities. The most distant component Ac, has been resolved using speckle interferometry, at a separation of about 0.04" It orbits the other two in 9.4 years. The two closest stars, Aa and Ab, are separated by only about a tenth of an astronomical unit and orbit in just under eight days.
The system lies within the Orion OB1 association, a group of massive stars that includes most of the bright stars of Orion. It is assigned to the oldest and closest part of the association, known as OB1a.
Variability.
Eta Orionis drops in brightness every four days from a combined apparent magnitude of 3.31 to about magnitude 3.6. This is due to eclipses between the two closest components, Aa and Ab. The primary and secondary eclipses are very similar, 0.24 and 0.23 magnitudes deep respectively.
It has also been suggested that component Ab is intrinsically variable with a period of 0.3 days and a very small amplitude. This star has unusual variable spectral lines and lies with the β Cephei variable instability strip. However, it is now thought that the variable component is either B and Ac, possibly due to an unseen companion or rotational modulation. The actual period is 0.432 days and the 0.3-day period was an alias.


Pi Persei

π Persei, Latinized as Pi Persei, is a single star in the northern constellation of Perseus. It has the traditional name Gorgonea Secunda , the second of three Gorgons in the mythology of the hero Perseus. This star has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.7. It is located at a distance of approximately 303 light years from the Sun based on parallax, and is moving further away with a radial velocity of +14 km/s.
This object is an A-type main-sequence star with a stellar classification of A2Vn, where the 'n' suffix indicates broad (nebulous) lines due to rapid rotation. It is spinning with a projected rotational velocity of 186 km/s, which is creating an equatorial bulge that is 6% wider than the polar radius. The star is 272 million years old with double the mass of the Sun. It has 4.8 times the Sun's radius and is radiating 170 times the luminosity of the Sun from its photosphere at an effective temperature of 9,290 K.


Xi Coronae Borealis

Xi Coronae Borealis (ξ CrB) is a binary star system in the northern constellation of Corona Borealis. It is visible to the naked eye with a combined apparent visual magnitude of 4.85. Based upon an annual parallax shift of 17.78 mas as seen from the Earth, it is located about 183 light years from the Sun.
As of 2009, the pair had an angular separation of 91 mas along a position angle of 139.4°. The brighter member, component Aa, is an evolved K-type giant star with a stellar classification of K0 III. It is a red clump star that is generating energy by helium fusion at its core. The star has an estimated 2.36 times the mass of the Sun and has expanded to 8 times the Sun's radius. It is radiating 36 times the solar luminosity from its photosphere at an effective temperature of 4,853 K.


QX Normae

QX Normae is an active low mass X ray binary in the constellation Norma. It is composed of a neutron star and a star smaller and cooler than the Sun. The X-ray component, known as 4U 1608–52, was discovered in the early 1970s, while the visual component, QX Normae, was discovered in 1977. By analysing the interstellar extinction between Earth and the system, Güver and colleagues calculated the most likely distance to be 5.8 kpc (19,000 light-years), and the neutron star's mass to be 1.74 ± 0.14 times that of the Sun and radius to be a mere 9.3 ± 1.0 km.


Epsilon Mensae

Epsilon Mensae is a single star about away in the faint constellation Mensa. It has an apparent magnitude of 5.5, making it visible with the naked eye under good skies. With a radial velocity of 10.82 km/s, it is drifting away from the Solar System, and is currently located 454 light years away based on parallax.
Properties.
This is a K2/3 giant that has exhausted hydrogen at its core. This means that the spectrum of Epsilon Mensae is intermediate between a K2 and K3 star. It is about 1.2 times the mass of the Sun, but has expanded to 23 times the girth. It is radiating 170 times the Sun's luminosity, and has an effective temperature of .


NGC 2300

NGC 2300 is a lenticular galaxy in the constellation Cepheus. It was discovered in 1871 by French astronomer Alphonse Borrelly using an 18 cm telescope.


X Cancri

X Cancri is a variable star in the northern constellation of Cancer. It has a red hue and is visible to the naked eye at peak magnitude, fluctuating around an apparent visual magnitude of 6.28. The distance to this object is approximately 2,900 light years based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s. It lies very close to the ecliptic and so is subject to lunar occultations.
This object is carbon staran aging red giant star on the asymptotic giant branch that has a higher abundance of carbon than oxygen in its atmosphereand is one of the brightest carbon stars in the sky. It has a carbon star spectral classification of C-N4.5 C25.5 MS3. The first C indicates that it is a carbon star, and the N5 that it is a fairly cool strongly red AGB star. The C2 index indicates the strength of the Swan bands on a scale of one to eight, which shows the relative abundance of carbon vs oxygen. The MS index, not to be confused with an MS spectral class, indicates the strength of the SiC2 bands on a scale of one to seven. These bands are thought to be very sensitive to temperature.
This is a semiregular variable star of subtype SRb that ranges in brightness from visual magnitude 5.52 down to 7.5 with a period of 193 days. Fourier analysis has shown that the star also pulsates with periods of 350 and 1,870 days.
The angular diameter of X Cancri has been measured using both lunar occultations and very long baseline interferometry, both methods giving a diameter around .


NGC 2547

NGC 2547 is a southern open cluster in Vela, discovered by Nicolas Louis de Lacaille in 1751 from South Africa. The star cluster is young with an age of 20-30 million years.
Observations with the Spitzer Space Telescope showed a shell around the B3 III/IV-type star HD 68478. This could be a sign of recent mass loss in this star.
A study using Gaia DR2 data showed that NGC 2547 formed about 30 million years ago together with a new discovered star cluster, called [BBJ2018] 6. The star cluster NGC 2547 has a similar age compared with Trumpler 10, NGC 2451B, Collinder 135 and Collinder 140. It was suggested that all these clusters formed in a single event of triggered star formation.
NGC 2547 shows evidence for mass segregation down to 3 .
Cluster members with debris disks.
Observations with the Spitzer Space Telescope have shown that ≤1% of the stars in NGC 2547 have infrared excess in 8.0 μm and 30-45% of the B- to F-type stars have infrared excess at 24 μm.
The system 2MASS J08090250-4858172, also called ID8 is located in NGC 2547 and showed substantial brightening of the debris disk at a wavelength of 3 to 5 micrometers, followed by a decay over a year. This was interpreted as a violent impact on a planetary body in this system.
NGC 2547 contains nine M-dwarfs with 24 μm excess. These could be debris disks and the material could be orbiting close to the snow line of these stars, indicating that planet-formation is underway in these systems. Later it was suggested that these M-dwarfs might contain Peter Pan Disks. 2MASS 08093547-4913033, which is one of the M-dwarfs with a debris disk in NGC 2547 was observed with the Spitzer Infrared Spectrograph. In this system the first detection of silicate was made from a debris disk around an M-type star.


UW Canis Majoris

UW Canis Majoris is a star in the constellation Canis Major. It is classified as a Beta Lyrae eclipsing contact binary and given the variable star designation UW Canis Majoris. Its brightness varies from magnitude +4.84 to +5.33 with a period of 4.39 days. Bode had initially labelled it as Tau2 Canis Majoris, but this designation had been dropped by Gould and subsequent authors.
UW Canis Majoris A is a rare blue supergiant of spectral type O7.5-8 Iab. The precise characteristics of the system are still uncertain, in part because the spectral signature of the secondary is very hard to disentangle from the spectrum of the primary and the surrounding envelope of stellar wind. A detailed spectral study by Gies et al. found that the primary had a diameter 13 times that of the Sun, while its secondary companion is a slightly cooler, less evolved and less luminous supergiant of spectral type O9.7Ib that is 10 times the Sun's diameter. According to this study, the brighter star is the more luminous, its luminosity 200,000 times that of the Sun as opposed to the secondary's 63,000 times. However the secondary is the more massive star at 19 Solar masses to the primary's 16.
However, a more recent photometric analysis finds several configurations of mass and luminosity ratios that match the observed data.
Parallax measurements showed it to be approximately 3000 light years from Earth, but this is unexpectedly close for a star of its spectral type and brightness. Recent more accurate Hipparcos parallax data gives an even closer result around 2000 light years. It is thought to be a distant member of NGC 2362 which would place it about 5000 light years and more closely match its expected luminosity. The contradiction between the different distance results is still a subject of research.


PGC 39058

PGC 39058 is a dwarf galaxy located 14 million light-years away in the constellation Draco. The galaxy is faint and obscured by HD 106381, a star in the foreground making it difficult to observe.


NGC 860

NGC 860 is an elliptical galaxy located in the constellation Triangulum.
It is about 410 million light-years from the Milky Way. It was discovered by the French astronomer Édouard Stephan in 1871.


Omega Cassiopeiae

Omega Cassiopeiae (ω Cassiopeiae) is a binary star system in the northern constellation of Cassiopeia. It has a combined apparent visual magnitude of +4.99, which means it is a faint star but visible to the naked eye. Based upon an annual parallax shift of 4.65 mas as seen from Earth, this system is located roughly 700 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.16 due to interstellar dust.
This is a single-lined spectroscopic binary star system with an orbital period of 69.92 days and an eccentricity of 0.30. The visible component has the spectrum of an evolved, B-type giant star with a stellar classification of B8 III. It is a helium-weak star, a type of chemically peculiar star that displays abnormally weak absorption lines of helium for a star of its temperature. Omega Cassiopeiae has an estimated 4.7 times the mass of the Sun and is radiating 488 times the Sun's luminosity from its photosphere at an effective temperature of around 12,737 K.


HD 223229

HD 223229 is a suspected variable star in the northern constellation of Andromeda. It is a double star consisting of a magnitude 6.11 primary and a magnitude 8.73 companion. The pair have an angular separation of 0.80″ along a position angle of 250°, as of 2009. The primary is a B-type subgiant star with a stellar classification of B3IV. It has an estimated 6.3 times the mass of the Sun, with an effective temperature of 17,900 K.


30 Cygni

30 Cygni is a class A5III (white giant) star in the constellation Cygnus. Its apparent magnitude is 4.83 and it is approximately 610 light years away based on parallax.
The Bayer letter ο (omicron) has been variously applied to two or three of the stars 30, 31, and 32 Cygni. 30 Cygni has sometimes been designated as ο1 Cygni with the other two stars being ο2 and ο3 respectively. For clarity, it is preferred to use the Flamsteed designation 30 Cygni rather than one of the Bayer designations.
30 Cygni is about six arc-minutes from 31 Cygni A and seven arc-minutes from 31 Cygni B. That pair is known as ο1 Cygni, while ο2 Cygni is a degree away. Both ο1 and ο2 are 4th magnitude stars.


HR 858

HR 858 is a star with a planetary system located 104 light years from the Sun in the southern constellation of Fornax. It has a yellow-white hue and is visible to the naked eye but is a challenge to see with an apparent visual magnitude of 6.4. The star is drifting further away with a radial velocity of 10 km/s. It has an absolute magnitude of +3.82.
This object is a slightly-evolved F-type main-sequence star with a stellar classification of F6V, which indicates it is generating energy through core hydrogen fusion. It is roughly two billion years old and is spinning with a projected rotational velocity of 8.3 km/s. The star has 1.1 times the mass of the Sun and 1.3 times the Sun's radius. It is radiating 2.3 times the luminosity of the Sun from its photosphere at an effective temperature of 6,201 K.
There is a faint co-moving stellar companion, designated component B, at an angular separation of . This corresponds to a projected separation of . It is most likely a red dwarf star.
In May 2019, it was announced to have at least 3 exoplanets as observed by transit method of the Transiting Exoplanet Survey Satellite. All three are orbiting close to the host star and appear to be super-Earths, about twice the size of the Earth. Components 'b' and 'c' may be in a 3:5 mean motion resonance.


45 Draconis

45 Draconis is a single star located in the northern circumpolar constellation of Draco, around 3,500 light years from the Earth. "45 Draconis" is the Flamsteed designation, while it has the Bayer designation of d Draconis. This object is visible to the naked eye as a faint, yellow-white hued star with an apparent visual magnitude of 4.78. Radial velocity measurements indicate it is moving closer to the Sun at the rate of −12.5 km/s.
Lyubimkov et al. (2012) assigned this star a stellar classification of F7Ib, matching an F-type supergiant. It is approximately 33 million years old with 8.2 times the mass of the Sun and about 62 times the Sun's radius. The star is radiating 5,450 times the Sun's luminosity from its photosphere at an effective temperature of 6,151 K.


NGC 820

NGC 820 is a spiral galaxy located in the constellation Aries about 210 million light-years from the Milky Way. It was discovered by British astronomer John Herschel in 1828.


Well (Chinese constellation)

The Well mansion (井宿, pinyin: Jǐng Xiù ; Japanese: chichiri-boshi) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the southern mansions of the Vermilion Bird.


HD 49674

HD 49674 is an 8th magnitude G-type main-sequence star (spectral type G5V) located approximately 144 light years away in the constellation of Auriga. It has a very similar mass to our Sun. It is orbited by a recently discovered planet.
HD 49674, and its planetary system, was chosen as part of the 2019 NameExoWorlds campaign organised by the International Astronomical Union, which assigned each country a star and planet to be named. HD 49674 was assigned to Belgium. The winning proposal named the star Nervia and the planet Eburonia, both after prominent Belgic tribes, the Nervii and Eburones respectively.
Planetary system.
At the time of discovery of the planet HD 49674 b in 2002, it was the least massive planet known, very close to the boundary between sub-Jupiter mass and Neptune-mass at 0.1 MJ. This planet orbits very close to the star.


T Leporis

T Leporis (T Lep / HD 32803 / HIP 23636) is a variable star in the constellation of Lepus, the Hare. It is located half a degree from ε Leporis in the sky; its distance is approximately 1,100 light years from the Solar System. It has the spectral type M6ev, and is a Mira variable — as is R Leporis, in the same constellation — whose apparent magnitude varies between +7.40 and +14.30 with a period of 368.13 days.
The annual parallax of T Leporis was measured by the Hipparcos mission, but the results were hopelessly imprecise. The parallax from Gaia Data Release 2 is more accurate and yields a distance of . The distance has also been measured using very-long-baseline interferometry and found to be .
Mira variables are some of the major sources of molecules and dust in the Universe. With each pulsation, T Leporis expels matter into space, each year losing an amount equivalent to the mass of Earth. Images of T Leporis obtained with the Very Large Telescope interferometer of the European Southern Observatory (ESO) have revealed a shell of gas and dust surrounding the star, whose diameter is some 100 times larger than that of the Sun. Given the great distance at which this class of stars lie, its apparent angular diameter — despite its enormous size — is no more than a millionth of the solar apparent angular diameter.


Kappa Coronae Borealis b

Kappa Coronae Borealis b is an extrasolar planet approximately 98 light-years away in the constellation of Corona Borealis. This planet was discovered by Johnson et al., who used the radial velocity method to detect wobbling of the star caused by a planet move around by its tug of gravity. It was first discovered in September 2007 and was published in November.
The planet is 1.8 Jupiter masses, or 570 Earth masses, although only the minimum mass is known since the inclination is not known. It orbits at a distance of 2.7 astronomical units, or 400 gigameters, and takes 1,208 days, or 3.307 years, to orbit around Kappa Coronae Borealis.


Wreath Nebula

The Wreath Nebula (also known as Barnard 3 or IRAS Ring G159.6-18.5 is an emission nebula and H II region with a radius of about 22 light-years, located about 1,000 light-years away within our Milky Way in the Perseus molecular cloud complex, near the boundary with the constellation of Taurus. Interstellar clouds like these are stellar nurseries, places where baby stars are being born.
The green ring is made of tiny particles of warm dust whose composition is very similar to smog found here on Earth. The red cloud in the middle is probably made of dust that is more metallic and cooler than the surrounding regions. The bright star in the middle of the red cloud, called HD 278942, is so luminous that it is likely what is causing most of the surrounding ring to glow. In fact its powerful stellar winds are what cleared out the surrounding warm dust and created the ring-shaped feature in the first place. The bright greenish-yellow region left of center is similar to the ring, though more dense. The bluish-white stars scattered throughout are stars located both in front of, and behind, the nebula.
Regions similar to this nebula are found near the band of the Milky Way in the night sky. The "wreath" is slightly off this band, near the boundary between the constellations of Perseus and Taurus, but at a relatively close distance of only about 1,000 light-years, the cloud is a still part of our Milky Way.
The colors used in this image represent specific wavelengths of infrared light. Blue and cyan (blue-green) represent light emitted at wavelengths of 3.4 and 4.6 microns, which is predominantly from stars. Green and red represent light from 12 and 22 microns, respectively, which is mostly emitted by dust.


P Leonis

The Bayer designation p Leonis (p Leo) is shared by five star systems in the constellation Leo:
Not to be confused with:


Kepler-78

Kepler-78 (formerly known as KIC 8435766) is a 12th magnitude star in the constellation Cygnus. Initially classified as an eclipsing binary with orbital period 0.710015 days, it was later re-classified as the single star with significant interaction between star magnetosphere and close-in planet. Radius of the star is of about 74% of the Sun, and an effective temperature of about 5100 K.
Planetary system.
Kepler-78 planetary system is composed by one planet called Kepler-78b, a planet slightly bigger than Earth with an extremely close orbit to the parent star. The orbital period of this planet is about 8.5 hours because of its proximity to its star. While it has a similar density to the Earth (at 5.57 g/cm3, its surface temperature is about 1300 to 1500 K.
References.
G-type main-sequence stars


NGC 5653

NGC 5653 is an unbarred spiral galaxy in the constellation Boötes. It was discovered on March 13, 1785 by John Herschel and subsequently placed in the New General Catalogue.


R Corvi

R Corvi (R Crv) is a Mira variable star in the constellation Corvus, which ranges from a magnitude of 6.7 to 14.4 with a period of approximately 317 days. In the sky it appears close to Gamma Corvi and can be seen in the same binocular field. Extrapolating its luminosity from its period of 317 days yields a distance of 810 parsecs.


NGC 6520

NGC 6520 is an open cluster in the constellation Sagittarius, superimposed upon the Large Sagittarius Star Cloud. It is magnitude 9.0, diameter 5 arc minutes and class G. It has about 25 stars of magnitude 9 to 12. The dark nebula Barnard 86 lies near its western edge.


HD 42936

HD 42936 is a binary star composed of an orange (K-type) main-sequence star and an L-type dwarf star just massive enough to burn hydrogen, located approximately 153 light-years away in the constellation of Mensa, taking its primary name from its Henry Draper Catalogue designation.
History and nomenclature.
The designation "HD 42936" is from the Henry Draper Catalogue, which is based on spectral classifications made between 1911 and 1915 by Annie Jump Cannon and her co-workers, and was published between 1918 and 1924.
Characteristics.
As a primary component of HD 42936 is K-type star, HD 42936 emits orange-tinted light.
Planetary system.
In 2019, an analysis carried out by a team of astronomers led by astronomer John R. Barnes of the Dispersed Matter Planet Project (DMPP) confirmed the existence of a super-Earth in orbit around HD 42936 A (DMPP-3).


NGC 5034

NGC 5034 is a spiral galaxy in the constellation of Ursa Minor. NGC 5034 is its New General Catalogue designation. It is located about 401 million light-years (123 Mpc) from the Sun. It was discovered on April 7, 1793, by William Herschel.
External links.


Theta Sagittae

Theta Sagittae (θ Sagittae) is a double star in the northern constellation of Sagitta. With a combined apparent visual magnitude of +6, it is near the limit of stars that can be seen with the naked eye. According to the Bortle scale the star is visible in dark suburban/rural skies. Based upon an annual parallax shift of as seen from Earth, it is located roughly from the Sun.
The binary pair consists of two stars separated by . The primary, component A, is an F-type main sequence star with a stellar classification of F3V. This star is about two billion years old with 52% more mass than the Sun. It forms a double star with a magnitude 8.85 companion, which is located at an angular separation of along a position angle of 331.1°, as of 2011. The star is sometimes described as a triple star, with a 7th magnitude companion away. This is an unrelated giant star much further away than the close pair. A fainter star separated by nearly was also listed as a companion by Struve, again just an accidental optical association.


NGC 6723

NGC 6723 is a globular cluster in the constellation Sagittarius. Its magnitude is given as between 6 and 6.8, and its diameter is between 7 and 11 arcminutes. It is a class VII cluster with stars of magnitude 14 and dimmer. It is near the border of Sagittarius and Corona Australis.
Unlike common globular clusters, NGC 6723 has an enhanced metallicity and a large fraction of younger stars, with primordial stars accounting for only 0.363 % of the total.


Xi Cephei

Xi Cephei (ξ Cephei, abbreviated Xi Cep, ξ Cep) is a multiple star system in the constellation of Cepheus. It is approximately 86 light-years from Earth.
It consists of two binary stars, designated Xi Cephei A and B, together with a more distant companion, Xi Cephei C. A's two components are themselves designated Xi Cephei Aa (officially named Kurhah , the traditional name of the system) and Ab.
Nomenclature.
"ξ Cephei" (Latinised to "Xi Cephei") is the system's Bayer designation. The designations of the three constituents as "ξ Cephei A", "B" and "C", and those of "A's" components - "ξ Cephei Aa" and "Ab" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
Xi Cephei bore the traditional names "Kurhah", "Alkirdah" or "Al Kirduh", the name coming from Qazvini who gave "Al Ḳurḥaḥ" ("القرحة" "al-qurhah"), an Arabic word Ideler translated as a white spot, or blaze, in the face of a horse. Allen indicates that Ideler felt this was not a proper name for a star, and suggested the name "Al Ḳirdah" (ألقردة "al qírada" "the Ape"). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Kurhah" for the component Xi Cephei Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "Celestial Hook", refers to an asterism consisting of Xi Cephei, 4 Cephei, HD 194298, Eta Cephei, Theta Cephei, Alpha Cephei, 26 Cephei, Iota Cephei and Omicron Cephei. Consequently, the Chinese name for Xi Cephei itself is (, ).
Properties.
Xi Cephei A is a double-lined spectroscopic binary system with an orbital period of 810.9 days and an eccentricity of 0.46. The primary, component Aa, is a chemically peculiar Am star, a probable subgiant with an apparent magnitude of +4.29. Eight arcseconds away, Xi Cephei B is another spectroscopic binary. Xi Cephei C is a 13th magnitude star nearly two arcminutes away.


C Centauri

The Bayer designations c Centauri and C Centauri are distinct.
The designation c Centauri is shared by two star systems in the constellation Centaurus:
The designation C Centauri is shared by three star systems:


29 Vulpeculae

29 Vulpeculae is a suspected astrometric binary star system in the northern constellation Vulpecula. It is visible to the naked eye as a faint, white-hued point of light with an apparent visual magnitude of 4.82. The system lies approximately 209 light years away from the Sun based on parallax, and is a member of the IC 2391 supercluster. It is moving closer to the Earth with a heliocentric radial velocity of −17 km/s.
Radial velocity measurements from High Accuracy Radial Velocity Planet Searcher with an amplitude of 4 km/s indicate that it is a spectroscopic binary of unknown period. The visible component is an A-type main-sequence star with a stellar classification of A0V, and has some slight abundance anomalies that resemble a weak Am star. It is catalogued as a shell star, showing spectral features of a cooler circumstellar jacket of gas, and may be a proto-shell star. The star is an estimated 254 million years old with a relatively low projected rotational velocity of 52 km/s. It has 2.67 times the mass of the Sun and is radiating 71 times the Sun's luminosity from its photosphere at an effective temperature of 10,507 K.


53 Virginis

53 Virginis is a single, yellow-white hued star in the zodiac constellation of Virgo. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.04. Based upon an annual parallax shift of , it is located 111 light years away. The star is moving closer to the Sun with a heliocentric radial velocity of −12.7 km/s. It has a relatively high rate of proper motion, traversing the celestial sphere at the rate of along a position angle of 162.2°.
Gray et al. (2006) assigned this star a stellar classification of F5.5 V, matching an ordinary F-type main-sequence star. Older studies, such as Malaroda (1975) or Eggen (1955), listed a class of F5 III-IV or F6 III-IV, suggesting a more evolved condition. It is spinning with a projected rotational velocity of 13.5 km/s and appears to be undergoing differential rotation. The star is nearly three billion years old, with 1.21 times the mass of the Sun and about three times the Sun's radius. It is radiating over nine times the Sun's luminosity from its photosphere at an effective temperature of around 6,346 K.
The star has three visual companions, the nearest being a magnitude 12.5 star located at an angular separation of along a position angle of 1°, as of 2000.


D Cancri

The Bayer designation d Cancri is shared by two star systems in the constellation Cancer:
See also.
δ Cancri


NGC 588

NGC 588 is a diffuse nebula located in the outskirts of the galaxy Messier 33, within the Triangulum constellation. It was discovered October 2 1861 by the German-Danish astronomer Heinrich d'Arrest.


NGC 386

NGC 386 is an elliptical galaxy located in the constellation Pisces. It was discovered on November 4, 1850 by Bindon Stoney. It was described by Dreyer as "considerably faint, small, round." Along with galaxies NGC 375, NGC 379, NGC 382, NGC 383, NGC 384, NGC 385, NGC 387 and NGC 388, NGC 386 forms a galaxy cluster called Arp 331.


Kappa Coronae Australis

The Bayer designation κ Coronae Australis (Kappa Coronae Australis) is shared by two stars in the constellation Corona Australis:
It was found to be a double star by English astronomer John Herschel in 1836. The pair have an angular separation of along a position angle of 359°.


65 Arietis

65 Arietis is a star in the northern constellation of Aries, located near Tau Arietis. "65 Arietis", abbreviated '65 Ari', is the Flamsteed designation. It has an apparent visual magnitude of 6.07, which, according to the Bortle Dark-Sky Scale, means it is faintly visible to the naked eye when viewed from dark suburban skies. Based upon an annual parallax shift of , it is approximately distant from the Sun. The star is moving closer to the Earth with a heliocentric radial velocity of around −6 km/s.
This is an ordinary A-type main sequence star with a stellar classification of A1 V. It has about 2.45 times the mass of the Sun and shines with 40 times the Sun's luminosity. This energy is being radiated into outer space at an effective temperature of 10.300 K, giving it the white-hued glow of an A-type star. It is roughly 23% of the way through its lifetime on the main sequence of core hydrogen burning stars.


Eta Microscopii

η Microscopii, Latinised as Eta Microscopii, is a solitary star in the constellation Microscopium. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.53. The star is located around 910 light-years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +22 km/s.
This is an aging giant star with a stellar classification of K3 III, indicating that it has exhausted the supply of hydrogen at its core then cooled and expanded. At present it has around 47 times the girth of the Sun. The star is radiating 735 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,365 K.
Multiple star catalogues list two optical companions. Two arc-minutes away, the 8th magnitude HD 200733 is a main sequence star much closer to Earth than η Microscopii. A 14th-magnitude star one arc-minute from η Microscopii is a background object.


NGC 3539

NGC 3539 is a lenticular galaxy in the constellation Ursa Major. It was discovered in April 1831 by John Herschel. It is a member of the galaxy cluster Abell 1185.


HD 86226

HD 86226 is a G type yellowish white star found in the constellation of Hydra.
A survey in 2015 has ruled out the existence of any stellar companions at projected distances above 12 astronomical units.
Planetary system.
Due to the periodic spectrum shifts when it had when placed under a Doppler test, 13 Magellan Doppler Velocity observations were made of an object found near the star. The object discovered in 2010 had a Keplerian orbit, was declared an exoplanet and dubbed HD 86226 b.
A hot Super-Earth planet called HD 86226 c was also discovered in 2020.


WASP-56

WASP-56 is a sun-like star of spectral type G6 in the constellation of Coma Berenices. It has an apparent magnitude of 11.48. Observations at the Calar Alto Observatory using the lucky imaging technique detected a candidate companion star located 3.4 arc seconds away, however it is not known if this is an actual binary companion or an optical double.
Planetary system.
It has a planet that was discovered by transit photometry in 2011 by the SuperWASP program. Fourteen transits were observed over three watching seasons, each lasting 214 minutes and reducing the stars' brightness by 14 millimagnitudes. The planet has around 0.6 times the mass of Jupiter and an orbital period of 4.6 days. The planet possibly has a large core of heavy metals.


NGC 277

NGC 277 is a lenticular galaxy in the constellation Cetus. It was discovered on October 8, 1864 by Heinrich d'Arrest.


NGC 6229

NGC 6229 is a globular cluster located in the constellation Hercules. It is designated as GC(v)B in the galaxy morphological classification scheme and was discovered by the British astronomer William Herschel on 12 May 1787. NGC 6229 is located at about 100,000 light years away from earth.<ref name="NASA/IPAC"></ref><ref name="NGC/IC"></ref>
It is an intermediate-metallicity globular cluster with two distinct generations of stars, and may be the remnant core of a spheroidal dwarf galaxy.


NGC 2683

NGC 2683 is a field spiral galaxy in the northern constellation of Lynx. It was nicknamed the "UFO Galaxy" by the Astronaut Memorial Planetarium and Observatory. It was discovered by the astronomer William Herschel on February 5, 1788.
It is viewed nearly edge-on from Earth's location in space and is located about 30 million light-years away, although previous estimates also give distances between 16 and 25 million light-years.
NGC 2683 is receding from Earth at , and from the Galactic Center at .
Visibility.
The reddened light from the center of the galaxy appears yellowish due to the intervening gas and dust located within the outer arms of NGC 2683. Its apparent magnitude is 10.6 making it not visible to the human eye without the aid of a small telescope.
Characteristics.
While usually considered an unbarred spiral galaxy, recent research suggests it may in fact be a barred spiral galaxy; its bar is hard to see due to its high inclination.
Further support for the presence of a bar stems from the X-shaped structure seen near its centre, which is thought to be associated with a buckling instability of a stellar bar.
It is also both smaller and less luminous than the Milky Way with very little neutral hydrogen or molecular hydrogen and a low luminosity in the infrared, which suggests a currently low rate of star formation.
NGC 2683 is rich in globular clusters, hosting about 300 of them, twice the number found in the Milky Way. Due to its vast distance and complexity (due to the association of globular clusters bound to it), NGC 2638's mass has not been calculated as accurately as it could be. Otherwise its volume and vector motions are reasonably well known and characterized.
Several satellite galaxies are known in the vicinity of NGC 2683. The largest is KK 69, with a Holmberg diameter of 12,000 light-years (3.7 kiloparsecs). It is a dwarf transitional galaxy, with properties intermediate between those of dwarf irregular galaxies and dwarf spheroidal galaxies. Another is KK 70, which is about half the diameter of KK 69. Two additional dwarf galaxies are assumed to be satellites: they are N2683dw1 and N2683dw2, which are dwarf irregular and dwarf spheroidal galaxies, respectively.


Frosty Leo Nebula

The Frosty Leo Nebula is a protoplanetary nebula (PPN) located roughly at 10,000 light-years away from Earth in the direction of the constellation Leo. It is a spectral bipolar nebula. Its central star is of optical spectral type K7II, by itself called "Frosty Leo". It is unusual in that it has an extremely deep absorption feature at 3.1 µm and is unusually located at more than 900 pc above the plane of our galaxy. Further, as of 1990, it has the only known PPN circumstellar outflow in which crystalline ice dominates the long-wavelength emission spectrum and the only known PPN with point-reflection-symmetric deviations from axial symmetry.
Characteristics.
The Frosty Leo Nebula has two lobes that are separated by 2″ between which is an almost edge-on dust ring. It also has two relatively faint but prominent compact nebulosities, or "ansae", separated by ~23″ along the polar axis of the PPN. The PPN as a whole has an hourglass like shape. It has an inclination angle of 15° relative to the plane of the sky. Its molecular envelope is expanding at a rate of ~25 km/s.
Observation history.
This PPN was first noticed in the IRAS survey due to its exceptionally cold IRAS color temperatures. It also has a uniquely sharp maximum at 60-μM.
Point symmetry.
It is the first bipolar PPN known to have point reflection symmetry (all others being axially symmetric). Point symmetry is a fairly common trait of planetary nebulae as found in NGC 2022, NGC 2371-2, NGC 6309, Cat's Eye Nebula, NGC 6563, Dumbbell Nebula, Saturn Nebula, A24, and Hb5. postulate that point symmetry is either due to the bipolar outflow being directed by a precessing disc or a precessing common envelope binary.
Naming.
 dubbed IRAS 09371+1212 as the "Frosty Leo Nebula" because of their interpretation of the object's extremely unusual far infrared spectrum that water is largely depleted in its gaseous state by ice condensation into grains and for its location in the Leo constellation. Their interpretation was subsequently verified in 1988 by three independent papers. further observed in the band between 35 and 65 μM that very cold (<50 K) silicate dust grains, abundantly coated with crystalline ice, are responsible for the 60-μM excess.