Sigma Draconis

Sigma Draconis (σ Draconis, abbreviated Sig Dra, σ Dra), also named Alsafi , is a 4.7-magnitude star located at a distance of 18.8 light-years from the Sun in the constellation of Draco.
Name.
"σ Draconis" (Latinised to "Sigma Draconis") is the star's Bayer designation, established in 1603 as part of the "Uranometria", a star catalogue produced by German celestial cartographer Johann Bayer.
It bore the traditional name "Alsafi", derived from the Arabic "Athāfi", itself erroneously transcribed from the Arabic plural "Athāfiyy", by which the nomads designated the tripods of their open-air kitchens. It was the name of an association of this star, Tau Draconis and Upsilon Draconis. According to a 1971 NASA memorandum, "Athāfi" or "Alsafi" were the title for three stars: Sigma Draconis as "Alsafi", Tau Draconis as "Athāfi I" and Upsilon Draconis as "Athāfi II". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Alsafi" for Sigma Draconis on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "Celestial Kitchen", refers to an asterism consisting of Sigma Draconis, Delta Draconis, Epsilon Draconis, Rho Draconis, 64 Draconis (see ) and Pi Draconis. Consequently, the Chinese name for Sigma Draconis itself is (, .)
Properties.
Sigma Draconis is a main sequence dwarf which has long served as a K0 V spectral standard star. Its classification as K0 V defines one of the anchor points of the Morgan–Keenan system that have remained unchanged since the original 1943 MKK Atlas. However, some modern spectroscopy gives it as designation of G9 V.
The radius of Sigma Draconis has been directly measured using interferometry with the CHARA array, which yields a result of 77.6% of the Sun's radius. It has 85% of the Sun's mass, but the luminosity of this star is only 41% that of the Sun. The projected rotation rate ("v" sin "i") is relatively low at 1.4 km/s. It is considered a slightly metal-poor star, meaning that it has a lower proportion of elements with masses greater than helium when compared to the Sun.
The temperature, luminosity and surface activity appear to vary slightly in a manner very similar to the sunspot cycle, although the full length of the cycle has not yet been determined (as of 1992). The total variability is among the lowest of all stars that have been measured by the Hipparcos spacecraft.
Sigma Draconis has a high proper motion, advancing across the celestial sphere at a rate of 1.835 arc seconds per year. The star made its perihelion passage about 46,725 years ago, when it came within . The components of Sigma Draconis's space velocity are U=+36, V=+40 and W=-10 km/s. This gives the star an unusually large orbital eccentricity about the Milky Way galaxy of 0.30 (compared to 0.06 for the Sun.) The mean galactocentric distance for the orbit is 10.3 kiloparsecs (about 34,000 light-years).
As of 2013, no Jupiter-size or larger companion had been detected about the star and there was no indication of excess infrared radiation that would be evidence of circumstellar matter (such as a debris disk).
Planet search.
Between 2004 and 2013, extensive radial velocity measurements were gathered on Sigma Draconis using the High Resolution Echelle Spectrometer on the Keck Observatory. The Keck/HIRES data indicated a possible period of about 300 days and a likely alias period of 2800 days. Adding data taken with the Automated Planet Finder at the Lick Observatory strengthened and narrowed the 300-day period while reducing the significance of the 2800-day period. The combined analysis suggests there may be a Uranus-mass planet on a 308-day orbit, though the authors do not yet consider the discovery to be publishable as they have not yet attempted to rule out other non-planetary explanations for the velocity variations.


List of stars in Hydra

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


NGC 6027c

NGC 6027c is a barred spiral galaxy that is part of Seyfert's Sextet, a compact group of galaxies, which is located in the constellation Serpens.


Kepler-4

Kepler-4 is a sunlike star located about 1610 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets. Kepler-4b, a Neptune-sized planet that orbits extremely close to its star, was discovered in its orbit and made public by the Kepler team on January 4, 2010. Kepler-4b was the first discovery by the Kepler satellite, and its confirmation helped to demonstrate the spacecraft's effectiveness.
Nomenclature and history.
Kepler-4 is named for the Kepler spacecraft, a NASA telescope tasked with finding Earth-like planets that transit their stars as seen from Earth. As the previous three planets that Kepler confirmed had already been confirmed by others, Kepler-4 and its planet were the first to be discovered by the Kepler team. The star and its system were announced in Washington, D.C. at the 215th meeting of the American Astronomical Society on January 4, 2010, along with Kepler-5, Kepler-6, Kepler-7, and Kepler-8. Of the presented planets, Kepler-4b was the smallest, around the size of planet Neptune. The discovery of Kepler-4b and the other planets presented at the AAS meeting helped to confirm that the Kepler spacecraft was indeed functional.
The Harlan J. Smith Telescope at McDonald Observatory in Fort Davis, Texas was used by astronomers from the University of Texas at Austin to follow up on Kepler's discoveries and confirm them. Telescopes in Hawaii, California, Arizona, and the Canary Islands were also used to confirm the findings.
Characteristics.
Kepler-4 is a G0-type star, which is similar to the Sun, except slightly brighter. The star is 1.117 Msun and 1.555 Rsun, or 111% the mass of and 155% the radius of the Sun. With a metallicity of .09 (± 0.10) [Fe/H], Kepler-4 is more metal-rich than the Sun, a figure that is important in that metal-rich stars tend to have orbiting planets more often than metal-poor stars. Kepler-4 is also about 6.7 billion years old. In comparison, the Sun is 4.6 billion years old. In addition, Kepler-4 has an effective temperature of 5781 (± 76) K, which is almost identical, within the errors, to that of the Sun, which is 5778 K.
As seen from Earth, Kepler-4 has an apparent magnitude of 12.7. It is, as a result, not visible with the naked eye.
Planetary system.
Kepler-4b's discovery was announced on January 4, 2010. It is the size of planet Neptune, at 0.077 MJ (7% the mass of Jupiter) and 0.357 RJ (36% the radius of Jupiter). The planet orbits its star every 3.213 days at 0.045 AU from the star. This distance compares to planet Mercury, which is 0.39 AU from the Sun. Kepler-4's eccentricity was assumed to be 0, however a subsequent independent reanalysis of the discovery data found a value of 0.25 ± 0.12. Likewise, the temperature of the planet is assumed to be 1650 K, far hotter than Jupiter's, which is assumed to be 124 K (not considering its internal heat and atmosphere).
A search for transit-timing variations in all 17 quarters of Kepler data did not detect any evidence of additional planets.


72 Cygni

72 Cygni is a star in the northern constellation of Cygnus, located 299 light years from the Sun and a member of the Hercules stream. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.87. 72 Cyg is moving closer to the Earth with a heliocentric radial velocity of −68 km/s. It has a relatively high proper motion, traversing the celestial sphere at the rate of per year.
This is an aging giant star with a stellar classification of , where the suffix notation indicates a mild underabundance of iron in the spectrum. It has 1.7 times the mass of the Sun but has expanded to 14 times the Sun's radius. The star is radiating 69 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,640 K.
72 Cygni has a wide companion at an angular separation of , corresponding to a projected separation of . This star has a J band (infrared) magnitude of and a class of M5.


88 Leonis

88 Leonis is a wide binary star system in the equatorial constellation of Leo, the lion. The system is near the lower limit of visibility to the naked eye with an apparent visual magnitude of 6.27. It is located at a distance of 77 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −4.8 km/s. It has a relatively high proper motion, traversing the celestial sphere at the rate of 0.379 arc seconds per annum.
The primary member of the system, component A, is a yellow-white hued F-type main-sequence star with a stellar classification of F9.5V. It is an estimated 5.7 billion years old and is spinning with a rotation period of 14.3 days. The star has a short magnetic activity cycle that averages around 3.5 years. A second cycle appears to vary over time, lasting 13.7 years at the start of observations then decreasing to 8.6 years over a span of 34 years of measurement. The star has 1.06 times the mass of the Sun and 1.10 times the Sun's radius. It is radiating 1.47 times the luminosity of the Sun from its photosphere at an effective temperature of 6,060 K.
The secondary, component B, is a magnitude 9.22 star at an angular separation of from the primary along a position angle of 326°. It has a class of G5 and 74% of the Sun's mass. The pair share a common proper motion through space with a projected separation of .


K Centauri

K Centauri is a possible binary star in the southern constellation of Centaurus. It has a white hue and is bright enough to be visible to the naked eye, having an apparent visual magnitude of +5.04.
K Centauri is located at a distance of approximately 410 light years from the Sun based on parallax, and it has an absolute magnitude of −0.91. This is an ordinary A-type main-sequence star with a stellar classification of A1V. It is spinning rapidly with a projected rotational velocity of 220 km/s, which is giving it a pronounced equatorial bulge that is 25% larger than the polar radius.
Analysis of Hipparcos and Gaia astrometry suggests that the relatively large margins of error in the calculated parallax may be due to orbital motion caused by an unseen companion. The companion would be an object orbiting at about .


NGC 7772

NGC 7772 is collection of stars in the constellation Pegasus that were thought to be an open cluster. The stars were first recorded on 7 October 1825 by the British astronomer John Herschel. Gaia data shows stars in the area are unrelated


HD 92845

HD 92845 is a star in double system in the constellation Antlia. Located around 1228 light-years distant, it shines with a luminosity approximately 162 times that of the Sun and has a surface temperature of 8893 K.


70 Cancri

70 Cancri is a star in the zodiac constellation of Cancer, located around 580 light years from the Sun. It is a challenge to view with the naked eye even under good seeing conditions, having an apparent visual magnitude of 6.7. The star is moving closer to the Earth with a heliocentric radial velocity of -21 km/s, and is expected to come to within in around nine million years. It is an A-type main-sequence star with a stellar classification of A1V. The object has a radius of about and is radiating 76 times the Sun's luminosity from its photosphere at an effective temperature of 8,887 K.


89 Virginis

89 Virginis is a single star in the zodiac constellation of Virgo, located 234 light years from the Sun. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 4.959. The star is moving closer to the Earth with a heliocentric radial velocity of −39 km/s.
This is an evolved giant star with a stellar classification of K0 III, having exhausted the hydrogen at its core and expanded away from the main sequence. It is a red clump star, which indicates it is generating energy through helium fusion at its core. This object is 3.4 billion years old with 1.7 times the mass of the Sun and 12 times the Sun's radius. It is radiating 69 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4706 K.


Chi Cygni

Chi Cygni (Latinised from χ Cygni) is a Mira variable star in the constellation Cygnus, and also an S-type star. It is around 500 light years away.
χ Cygni is an asymptotic giant branch star, a very cool and luminous red giant nearing the end of its life. It was discovered to be a variable star in 1686 and its apparent visual magnitude varies from as bright as 3.3 to as faint as 14.2.
History.
Flamsteed recorded that his star 17 Cygni was Bayer's χ Cygni. It is assumed that χ was not visible at that time, but there is no further information and the discrepancy was not noticed until 1816. Bayer had recorded χ Cygni as a 4th magnitude star, presumably near maximum brightness.
The astronomer Gottfried Kirch discovered the variability of χ Cygni in 1686. While researching that area of the sky for observations of Nova Vulpeculae, he noted that the star marked as χ in Bayer's Uranometria atlas was missing. He continued to monitor the area and on October 19, 1686 he recorded it at 5th magnitude.
Kirch regarded χ Cyg as a regular variable with a period of 404.5 days, but it was quickly noted that both the period and amplitude varied considerably from cycle to cycle. Thomas Dick, LL.D, writes:
The star was then observed only sporadically until the 19th century. A continuous sequence of observations were made by Argelander and Schmidt from 1845 to 1884. These were the first series of observations showing the minima of the light variations. Since the start of the 20th century, it has been monitored closely by multiple observers.
The earliest spectra of χ Cygni could only be taken near maximum light. They show weak absorption lines, with bright emission lines superimposed, and it was typically classified as around M6e at maximum brightness. After the S class was introduced, χ Cygni was considered intermediate between class M and class S, for example either S5e or M6-M8e. Later more sensitive spectra near minimum gave spectral types as late as M10 or S10,1e. Under the revised classification system for S stars, designed to better reflect the gradation between M stars and carbon stars, χ Cygni at normal maximum was classified as S6 Zr2 Ti6 or S6+/1e, considered equivalent to MS6+. Spectral types at different phases of variation ranged from S6/1e to S9/1-e although no measurements were taken at minimum brightness.
SiO masers were detected from χ Cygni in 1975. H2O emission from χ Cygni's atmosphere was detected in 2010, but H2O masers have not been found.
Variability.
χ Cygni shows one of the largest variations in apparent magnitude of any pulsating variable star. The observed extremes are 3.3 and 14.2 respectively, a variation of more than 10,000-fold in brightness. The mean maximum brightness is about magnitude 4.8, and the mean minimum is around magnitude 13.4. The shape of the light curve is fairly consistent from cycle to cycle, with the rise being steeper than the fall. There is a "bump" approximately halfway from minimum to maximum, where the brightness increase temporarily slows before rising very quickly to maximum. The faster rise and bump are common features in the light curves of Mira variables with periods longer than 300 days. The rise time is 41–45% of the fall time.
Both the maximum and minimum magnitude varies considerably from cycle to cycle: maxima may be brighter than magnitude 4.0 or fainter than 6.0, and minima fainter than magnitude 14.0 or brighter than magnitude 11.0. The maximum of 2015 may have been the faintest ever observed, barely reaching magnitude 6.5, while less than 10 years earlier the 2006 maximum was the brightest for over a century at magnitude 3.8. Some of the supposed brightest minima may simply be due to incomplete observational coverage. Longterm BAA and AAVSO data show minima consistently between about magnitude 13 and 14 throughout the 20th century.
The period from maximum to maximum or minimum to minimum is not consistent, and can vary by up to 40 days either side of the mean. The mean period depends on the period of observations used, but is generally taken to be 408.7 days. There is some evidence that the mean period has increased by about 4 days over the last three centuries. Period variations on shorter timescales appear to be random rather than cyclical, although it is possible that the secular period increase is not linear. The period change is only significant when calculated using the maxima and not when using the minima which are only available for more recent cycles.
The spectral type is observed to vary during the brightness changes, from S6 to S10. The earliest spectral types are found at maximum brightness. After maximum, the strength of the emission lines starts to increase. Towards minimum, emission becomes very strong and many unusual forbidden and molecular lines appear.
The diameter of χ Cygni can be measured directly using interferometry. Observations show that the diameter varies from around 19 mas to 26 mas. The size changes are almost in phase with the brightness and spectral type. The smallest size is observed at phase 0.94, which is 30 days before the maximum.
Distance.
The annual parallax of χ Cygni has been calculated at 5.53 mas in the new reduction of Hipparcos satellite data, which corresponds to a distance of 590 light years. The parallax is only about a quarter of the angular diameter of the star. The statistical margin of error is about 20%.
The distance can also be derived by comparing changes in the angular diameter with the measured radial velocity in the atmosphere. This gives a parallax of 5.9 mas with a similar accuracy to the direct measurement, corresponding to a distance of 550 light years.
Older studies generally derived smaller distances such as 345, 370, or 430 lights years. The original parallax calculated from Hipparcos measurements was 9.43 mas, indicating a distance of 346 light years.
Comparing the apparent magnitude of χ Cygni with an absolute magnitude calculated from the period-luminosity relationship gives a distance compatible with the latest parallax values.
Properties.
χ Cygni is much larger and cooler than the sun, so large that it is thousands of times more luminous despite the low temperature. It pulsates, with both the radius and temperature varying over approximately 409 days. The temperature varies from about 2,400 K to about 2,700 K and the radius varies from about to . These pulsations cause the luminosity of the star to vary from about to , but they cause the visual brightness to vary by over 10 magnitudes. The huge visual magnitude range is created by a shift of electromagnetic radiation from the infrared as the temperature increases, and by formation at cool temperatures of molecules that absorb visual light. An alternate calculation gives the star a cooler temperature of 2,000 K, a luminosity of , and a correspondingly larger radius of .
The visual magnitude of the star is closely correlated with the changes in the spectral type and temperature. The radius is almost anti-correlated with the temperature. The minimum radius occurs approximately 30 days before the maximum temperature. The bolometric luminosity variation is primarily driven by the change in the size of the star, with the maximum luminosity occurring about 57 days before the maximum radius and lowest temperature are reached. The luminosity varies over a quarter of a cycle behind the visual brightness, meaning the star is fainter at maximum luminosity than at minimum luminosity.
The mass of isolated stars is difficult to determine accurately. In the case of χ Cygni, its pulsations offer a way to directly measure the gravitation acceleration of layers in the atmosphere. The mass measured in this way is . Applying an empirical relation for Mira stars to χ Cygni gives a mass of . χ Cygni is losing mass at a rate of nearly each year through a stellar wind at 8.5 km/s.
χ Cygni is usually classified as an S-type star because of the bands of zirconium oxide and titanium oxide in its spectrum. Compared to other S stars, the ZrO bands are weak and bands from VO are visible, so that the spectrum is sometimes described as MS, intermediate between a normal M spectrum and the S type. It also shows spectral lines from s-process elements such as technetium, produced naturally in AGB stars such as Mira variables. S stars are an intermediate phase between M class stars which have atmospheres with more oxygen than carbon, and carbon stars which have more carbon in their atmospheres. The carbon is moved into the atmosphere by third dredge-ups which occur with thermal pulses. S stars have C/O ratios between about 0.95 and 1.05. The C/O ratio in χ Cygni's atmosphere is 0.95, consistent with its status as a borderline S/MS star.
χ Cygni is the first Mira star to have a magnetic field detected. It is believed that the very weak magnetic field normally found in AGB stars is amplified by the shock wave during the pulsations of the star's atmosphere.
Evolution.
χ Cygni is a luminous and variable red giant on the asymptotic giant branch (AGB). This means it has exhausted its core helium, but is not massive enough to start burning heavier elements and is currently fusing hydrogen and helium in concentric shells. Specifically it is on the thermally pulsing portion of the AGB (TP-AGB) which occurs when the helium shell is close to the hydrogen shell and undergoes periodic flashes as it stops fusion for a time and new material accumulates from the hydrogen-burning shell.
AGB stars become more luminous, larger, and cooler as they lose mass and the internal shells move closer to the surface. Mass loss increases as the mass decreases, the luminosity increases, and more fusion products are dredged up to the surface. They "ascend" the AGB until the mass loss becomes so extreme that they start to increase in temperature and enter the post-AGB phase, eventually to become a white dwarf.
The evolution of a Mira variable should cause its period to increase, assuming it stays with the unstable region of pulsations. However, this secular trend is interrupted by the thermal pulses. These thermal pulses occur tens of thousands of years apart, but are theorised to produce rapid period changes over less than a thousand years following the pulse. The period changes detected for χ Cygni are suggestive of the end of that rapid change from a thermal pulse. The period changes between pulses are too slow to be detected with current observations.
Thermal pulses on the TP-AGB produce progressively more dramatic changes until the end of the AGB phase. Each pulse causes internal instability which triggers convection from the surface towards the hydrogen shell. When this convection zone becomes deep enough, it moves fusion products from the shell to the surface. This is known as the third dredge-up although there can be several third dredge-ups. The appearance of these fusion products at the surface is responsible for the change of an M star to an S star, and ultimately to a carbon star.
The initial mass and age of an AGB star are difficult to derive accurately. Intermediate mass stars lose relatively little mass, less than 10%, up to the start of the AGB, but have strong mass loss on the AGB, especially the TP-AGB. Stars with very different initial masses can show very similar properties on the AGB. A star initially with will take around 400 million years to reach the AGB, then around 6 million years to reach the TP-AGB, and spend one million years in the TP-AGB phase. It will lose around before the TP-AGB and on the TP-AGB. The carbon-oxygen core of will go on to become a white dwarf and the remaining envelope will be shed to possibly become a planetary nebula.


Beta Lupi

Beta Lupi (β Lupi, β Lup), or Kekouan , is a star in the southern constellation of Lupus. It has an apparent visual magnitude of 2.7, making it readily visible to the naked eye. Based upon parallax measurements, this star is located at a distance of about from Earth.
Properties.
The stellar classification of B2 III indicates this is a giant star. The effective temperature of the star's outer envelope is 24,090 K, giving it the blue-white hue of a B-type star. With an age of around 25 million years, it is near the end of its hydrogen phase, where hydrogen is fused into the element helium, and transferring into a red supergiant star. At about 8.8 solar masses, it may have enough mass to end its life as a Type II supernova, but there is the possibility of Beta Lupi becoming a white dwarf.
This is a multi-period Beta Cephei variable with a dominant oscillation period of 0.232 days. It is a proper motion member of the Upper-Centaurus Lupus sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. Beta Lupi has a high proper motion of more than 50 mas per year, suggesting a significant transverse velocity.
It lies close to the supernova remnant SN 1006.
Name.
In Chinese, (), meaning "Imperial Guards", refers to an asterism consisting of β Lupi, γ Lupi, δ Lupi, κ Centauri, λ Lupi, ε Lupi, μ Lup, π Lupi, ο Lupi and α Lupi. Consequently, the Chinese name for β Lupi itself is (, .). From the French rendering of this Chinese name derives the traditional European name Kekouan ("Ke Kwan").


HD 63744

HD 63744 is a class K0III (orange giant) star in the constellation Puppis. Its apparent magnitude is 4.71 and it is approximately 232 light years away based on parallax.


Dhanishta

Dhanishtha (Devanagari: धनिष्ठा), (), (Malayalam: അവിട്ടം), (Telugu: ధనిష్ఠ) and (Kannada: ಧನಿಷ್ಠಾ) is the twenty-third nakshatra in Hindu astronomy, corresponding to α to δ Delphini. It is also known as Avittam in Malayalam and Tamil. In Jyotiṣa, Dhanishta is ruled by Mangala (the planet Mars).
Dhanishta is classified as a movable nakshatra, meaning that, under electional astrological beliefs, it is best to begin activities like travel when the moon is in Dhanishta. This is based on the Panchanga reading only (which is also known as a calendar to track the suitable day for doing or starting anything good).
The deities which preside over Dhanishta are the Ashta Vasus: Agni, Prithvi, Vāyu, Varuna, Dyaus, Surya, Chandramas and Dhruva. The powers bestowed by the Ashta Vasus comes under the domain of Lord Nataraja who is the main supreme deity of this nakshatra. The animal associated to this nakshatra is a male lion and it is symbolized as "A Lion which is resting majestically after a Lion's share" but has been misinterpreted as a lioness, the animal associated for Purva Bhadrapada nakshatra. The symbol that is most commonly used to represent Dhanishta is the drum known as the Udukai in Tamil and Damaru in Sanskrit.
It is the birth star of a great Tamil Siddhar Tirumular and also the birth star of Bhishma, a great hero in the Mahabharata epic.
Traditional Hindu given names are determined by which pada (quarter) of a nakshatra the Ascendant/Lagna was in at the time of birth. In the case of Dhanista, the given name would begin with the following syllables:


Eta Pegasi

Eta Pegasi (η Pegasi, abbreviated Eta Peg, η Peg), formally named Matar , is a binary star in the constellation of Pegasus. The apparent visual magnitude of this star is +2.95, making it the fifth-brightest member of Pegasus. Based upon parallax measurements, the distance to this star is about from the Sun.
Nomenclature.
"η Pegasi" (Latinised to "Eta Pegasi") is the star's Bayer designation.
It bore the traditional name "Matar", derived from the Arabic سعد المطر "Al Saʽd al Maṭar", meaning "lucky star of rain". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Matar" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
In Chinese, (), meaning "Resting Palace", refers to an asterism consisting η Pegasi, λ Pegasi, μ Pegasi, ο Pegasi, τ Pegasi and ν Pegasi. Consequently, η Pegasi itself is known as (), "the Fourth Star of Resting Palace".
Namesake.
USS Matar (AK-119) was a United States Navy Crater class cargo ship named after the star.
Properties.
The Eta Pegasi system consists of a pair of stars in a binary orbit with a period of 813 days and an eccentricity of 0.183. The primary component is a bright giant star with a stellar classification of G2 II and about three and a half times the mass of the Sun. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of more than 24 times the radius of the Sun. It is radiating 331 times the luminosity of the Sun from its expanded outer envelope at an effective temperature of 4,970 K. The rotation rate of the star slowed as it expanded, so it has a projected rotational velocity of 1.7 km s−1 with an estimated rotation period of 818 days.
The secondary component is an F-type main sequence star with a classification of F0 V. The secondary star is 3.56 magnitudes fainter that the primary star at 700 nm. There are also 2 class G stars further away that may or may not be physically related to the main pair.


Upsilon Andromedae d

Upsilon Andromedae d (υ Andromedae d, abbreviated Upsilon And d, υ And d), formally named Majriti , is a super-Jupiter exoplanet orbiting within the habitable zone of the Sun-like star Upsilon Andromedae A, approximately 44 light-years (13.5 parsecs, or nearly km) away from Earth in the constellation of Andromeda. Its discovery made it the first multiplanetary system to be discovered around a main sequence star, and the first such system known in a multiple star system. The exoplanet was found by using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object.
Name.
In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Majriti for this planet. The winning name was submitted by the Vega Astronomy Club of Morocco, honoring the 10th century scientist Maslama al-Majriti.
Characteristics.
Mass, radius and temperature.
Upsilon Andromedae d is a super-Jupiter, an exoplanet that has a mass larger than that of the planet Jupiter. It has a temperature of . It has a mass of 10.25 and a likely radius of around 1.02 based on its mass.
Host star.
The planet orbits a (F-type) star named Upsilon Andromedae A. The star has a mass of 1.27 and a radius of around 1.48 . It has a temperature of 6074 K and is 3.12 billion years old. In comparison, the Sun is about 4.6 billion years old and has a temperature of 5778 K. The star is slightly metal-rich, with a metallicity ([Fe/H]) of 0.09, or about 123% of the solar amount. Its luminosity () is 3.57 times that of the Sun.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 4.09. Therefore, Upsilon Andromedae can be seen with the naked eye.
Orbit.
Upsilon Andromedae d orbits its star nearly every 3.5 years (about 1,276 days) in an eccentric orbit, more eccentric than that of any of the known planets in the Solar System. To explain the planet's orbital eccentricity, some have proposed a close encounter with a now-lost outer planet of Upsilon Andromedae A. The encounter would have moved planet "d" into an eccentric orbit closer to the star and ejected the outer planet.
Habitability.
Upsilon Andromedae d lies in the habitable zone of Upsilon Andromedae A as defined both by the ability for an Earthlike world to retain liquid water at its surface and based on the amount of ultraviolet radiation received from the star.
For a stable orbit the ratio between the moon's orbital period "P"s around its primary and that of the primary around its star "P"p must be < 1/9, e.g. if a planet takes 90 days to orbit its star, the maximum stable orbit for a moon of that planet is less than 10 days. Simulations suggest that a moon with an orbital period less than about 45 to 60 days will remain safely bound to a massive giant planet or brown dwarf that orbits 1 AU from a Sun-like star. In the case of Upsilon Andromedae d, the orbital period would have to be no greater than 120 days (around 4 months) in order to have a stable orbit.
Tidal effects could also allow the moon to sustain plate tectonics, which would cause volcanic activity to regulate the moon's temperature and create a geodynamo effect which would give the satellite a strong magnetic field.
To support an Earth-like atmosphere for about 4.6 billion years (the age of the Earth), the moon would have to have a Mars-like density and at least a mass of 0.07 . One way to decrease loss from sputtering is for the moon to have a strong magnetic field that can deflect stellar wind and radiation belts. NASA's Galileo's measurements hints large moons can have magnetic fields; it found that Jupiter's moon Ganymede has its own magnetosphere, even though its mass is only 0.025 .
Discovery and further studies.
Upsilon Andromedae d was detected by measuring variations in its star's radial velocity as a result of the planet's gravity. This was done by making precise measurements of the Doppler shift of the spectrum of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the hot Jupiter Upsilon Andromedae b; however, by 1999, it was clear that the inner planet could not explain the velocity curve.
In 1999, astronomers at both San Francisco State University and the Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data. The two new planets were designated Upsilon Andromedae c and Upsilon Andromedae d.
Preliminary astrometric measurements suggest the orbit of Upsilon Andromedae d may be inclined at 155.5° to the plane of the sky. However, these measurements were later proved useful only for upper limits;, and contradict even the inner planet u And b's inclination of >30°. The mutual inclination between c and d meanwhile is 29.9 degrees. The true inclination of Upsilon Andromedae d was determined as 23.8° after combined results were measured from the Hubble Space Telescope and radial velocity measurements.
When it was discovered, a limitation of the radial velocity method used to detect Upsilon Andromedae d is that the orbital inclination is unknown, and only a lower limit on the planet's mass can be obtained, which was estimated to be about 4.1 times as massive as Jupiter. However, by combining radial velocity measurements from ground-based telescopes with astrometric data from the Hubble Space Telescope, astronomers have determined the orbital inclination as well as the actual mass of the planet, which is about 10.25 times the mass of Jupiter.


Phi Centauri

Phi Centauri, Latinized from φ Centauri, is a blue-white hued star in the southern constellation Centaurus. It is visible to the naked eye with an apparent visual magnitude of +3.7. The annual parallax shift is 6.21 mas as measured from Earth, which yields a distance estimate of around 530 light years. It is moving further from the Sun with a radial velocity of +5 km/s.
This is a B-type subgiant star with a stellar classification of B2 IV. It has no known companions, but does show radial velocity variations and higher order pulsations in the spectrum. The star is just 18 million years old with 8.5 times the mass of the Sun and has 4.2 times the Sun's radius. It is radiating around 4,000 times the Sun's luminosity from its photosphere at an effective temperature of about 21,638 K.
This star is a proper motion member of the Upper-Centaurus Lupus sub-group in the
Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.


NGC 2985

NGC 2985 is a spiral galaxy located in the constellation Ursa Major. It is located at a distance of circa 70 million light years from Earth, which, given its apparent dimensions, means that NGC 2985 is about 95,000 light years across. It was discovered by William Herschel on April 3, 1785.
The galaxy is seen with an inclination of 37 degrees. The galaxy has a bright nucleus from which emanate multiple tightly wound spiral fragments. Numerous blue knots are visible at the galactic disk. At the outer part of the galaxy lies a massive spiral arm that forms a pseudoring that encircles the galaxy. The inner part of the galaxy, where active star formation has been observed, has been found to be unstable, contrary to the outer stable one. It has been suggested that the presence of molecular clouds accounts for the instability of the region.
The nucleus of NGC 2985 is active, and based on its spectrum has been categorised as a LINER. The most accepted theory for the activity source is the presence of an accretion disk around a supermassive black hole. The mass of the supermassive black hole at the centre of NGC 2985 is estimated to be 160 million (108.2) , based on stellar velocity dispersion. The velocity dispersion is anisotropic, and changes with the azimuth. The rotational speed of the galaxy at its effective radius is 222.9 ± 31.2 km/s.
NGC 2985 is the brightest member of a galaxy group known as the NGC 2985 group. Other members of the group include NGC 3027, 25 arcminutes away. Other nearby galaxies include NGC 3252, and NGC 3403.


CoRoT-3

CoRoT-3 is a white-yellow dwarf main sequence star hotter than our Sun. This star is located approximately 2560 light-years away in the constellation of Aquila. The apparent magnitude of this star is 13, which means it is not visible to the naked eye but can be seen with a medium-sized amateur telescope on a clear dark night.
Planetary system.
This star is home to object designated CoRoT-3b. This object was discovered by the CoRoT Mission spacecraft using the transit method. Measurements made using the radial velocity method show that this object is probably a brown dwarf.


Alpha Capricorni

Alpha Capricorni (α Capricorni, abbreviated Alpha Cap, α Cap) is an optical double star in the constellation of Capricornus. The two physically unrelated components are designated:
They are separated by 0.11° on the sky, and resolvable with the naked eye, similar to Mizar and Alcor. α¹ Capricorni is fainter (apparent magnitude 4.27) than α² Capricorni (apparent magnitude 3.58).
Nomenclature.
"α Capricorni" (Latinised to "Alpha Capricorni") is the system's Bayer designation; "α¹" and "α² Capricorni", those of the two components.
Alpha Capricorni bore the traditional names "Algedi", "Algiedi", "Al Giedi" or "Giedi", derived from the Arabic "الجدي" "al-jady" "the billy goat" or "kid". It also refers to the entire constellation of Capricornus. "Giedi" is sometimes also associated with Beta Capricorni. "α¹" and "α² Capricorni" were also called "Prima Giedi" and "Secunda Giedi", respectively. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Algedi" for "α² Capricorni" on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Alpha Capricorni is known as 牛宿二 (the Second Star of the Ox) in Chinese astronomy.


NGC 5949

NGC 5949 is a dwarf spiral galaxy located about 44 million light years away in the constellation of Draco.


50 Persei

50 Persei is a star in the constellation Perseus. Its apparent magnitude is 5.52, which is bright enough to be seen with the naked eye. Located around distant, it is a White main-sequence star of spectral type F7V, a star that is currently fusing its core hydrogen. In 1998 the star was named a candidate Gamma Doradus variable with a period of 3.05 days, which would means it displays variations in luminosity due to non-radial pulsations in the photosphere. Subsequently, it was classified as a RS Canum Venaticorum and BY Draconis variable by an automated program.
This is probably a binary system with an unseen companion. It is physically associated with the likely binary system HIP 19255, with the two pairs orbiting each other over a time scale of around a million years. The components of HIP 19255 have an angular separation of 3.87″ and the two components orbit each other every 590 years. 50 Persei may share a gravitational association with Capella, even though the two are separated by nearly 15° − equivalent to a distance of .
50 Persei is emitting an infrared excess at a wavelength of 70 μm, suggesting the presence of a circumstellar debris disk. The disk has a temperature of .


HD 88366

S Carinae (HD 88366) is a variable star in the constellation Carina.
S Carinae is an M-type red giant with a mean apparent magnitude of +6.94. It is approximately 1,620 light years from Earth. It is classified as a Mira type variable star and its brightness varies between magnitude +4.5 and +10.0 with a period of 149.49 days. It has one of the earliest spectral types, and hence the hottest temperatures, of any Mira variable, and has a relatively short period for the class. It is a pulsating star, with the temperature being highest at maximum visual brightness and lowest at the visual minimum.
S Carinae has exhausted its core hydrogen and expanded to become a red giant. It has also exhausted its core helium and evolved to the asymptotic giant branch, where it fuses hydrogen and helium in separate shells outside the core.


NGC 900

NGC 900 is a lenticular galaxy located in the constellation Aries about 430 million light-years from the Milky Way. It was discovered by the German astronomer Albert Marth in 1864.


3 Puppis

3 Puppis (3 Pup) is a supergiant star in the constellation Puppis. It is a very rare A[e] supergiant, referred to as a B[e] star despite its spectral classification, and its apparent magnitude is 3.93.
3 Puppis is surrounded by a disc of circumstellar dust, which is unusual for an A-type star. It is thought to be caused by a low mass companion. The companion is calculated to be a B8III - B6V star with a mass of , and its orbit has a semi major axis of 2.3 AU. Like most B[e] stars, 3 Pup rotates rapidly, at 30% - 60% of the speed at which it would start to break apart. The disc has its inner edge only 3.8 AU from the primary star and it is suspected that deceleration of the hot primary stellar wind by the companion allows the dust to form unusually close to such a luminous star.


NGC 6790

NGC 6790 is a young, compact planetary nebula with a high surface brightness located in the equatorial constellation of Aquila. Imaging by the Hubble Space Telescope shows elongated shells surrounding the central star. The distance to this nebula is poorly known, but is estimated at around , and it is roughly 6,000 years old. The expansion velocity of the neutral hydrogen component is in the range . The central star is a white dwarf with a temperature of around and a photographic magnitude of 11.1. It has a mass of , having evolved from a star with a mass about the same as the Sun.


Phi3 Hydrae

Phi3 Hydrae (φ3 Hya) is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 2 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 15.49 mas as seen from Earth, it is located around 211 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.90. It forms a triangle with the fainter φ1 Hydrae and φ2 Hydrae, between μ Hydrae and ν Hydrae.
This is a single-lined spectroscopic binary star system with an orbital period of about 1,200 days and an eccentricity of 0.1. The primary, component A, is an evolved G-type giant star with a stellar classification of G8 III. It is a red clump star, which means it is generating energy through the fusion of helium at its core. The star has twice the mass of the Sun and has expanded to 9 times the Sun's radius. It is 1.17 billion years old and is radiating 48 times the solar luminosity from its photosphere at an effective temperature of 4,952 K.


T Vulpeculae

T Vulpeculae is a possible binary star system in the northern constellation of Vulpecula, near the star Zeta Cygni, close to the pair 31 Vulpeculae and 32 Vulpeculae. It is visible to the naked eye with an apparent visual magnitude that ranges around 5.75. The distance to this system is around 1,900 light years, as determined from its annual parallax shift of .
A well-studied Classical Cepheid variable and one of the brightest known, the apparent magnitude of T Vulpeculae ranges from 5.41 to 6.09 over a period of 4.435 days. It is a yellow-white hued supergiant of spectral type F5 Ib. The variability of T Vul was discovered in 1885 by Edwin Sawyer. Observations between 1885 and 2003 shows a small but continuous decrease in the period of variability amounting to 0.25 seconds per year.
The companion star was detected in 1992; it is an A-type main-sequence star with a class of A0.8 V and 2.1 times the Sun's mass. Orbital periods of 738 and 1,745 days have been proposed for the pair, although, as of 2015, there remains doubt as to whether this is an actual binary system.


HD 202259

HD 202259 is a suspected variable star in the equatorial constellation of Aquarius. With an apparent magnitude of 6.39, according to the Bortle scale it is faintly visible to the naked eye from dark rural skies. It has a stellar classification of M1 III, and is a red giant located along the asymptotic giant branch of the HR diagram. Located about 900 light years away, its radial velocity of −123.5 km/s indicates this is a high-velocity star.


Phi Leonis

Phi Leonis (φ Leo) is a star in the constellation Leo. It is bright enough to be seen with the naked eye, having an apparent visual magnitude of 4.46. Based upon parallax measurements, the distance to Phi Leo is around 184 light years.
The spectrum of this star fits a stellar classification of A7IVn, which suggests it is an A-type subgiant star that has left the main sequence and is evolving into a giant star. It is being viewed with the plane of the star's equator lying close the line of sight from the Earth, and shows a high rotation rate with a projected rotational velocity of 254 km/s. This rapid spin is giving the star an oblate shape with an equatorial bulge that is 29% larger than the polar radius.
Phi Leonis has been mentioned as a shell star—indicating that there is a circumstellar disk of gas around the star's equator—and may display a slight variability. Sporadic variation of the spectra on the time scale of minutes up to months in duration suggests that solid, cometary bodies are in orbit around the star, with objects approaching close enough for refractory materials to sublimate. Most exocomet hosts do have a circumstellar disk, which can act as an exocomet reservoir. Cold dust around Phi Leonis was not detected, and the star is not associated with a warm debris disk.


32 Pegasi

32 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.81 The system is located approximately 560 light years away from the Sun based on parallax, and is drifting further away with a radial velocity of +11.4 km/s.
The brighter member of this system, designated component Aa, has visual magnitude 4.83 with a stellar classification of B9III, matching a late B-type star with the luminosity class of a giant. It is spinning with a projected rotational velocity of 60 km/s, and is radiating 541 times the luminosity of the Sun from its photosphere at an effective temperature of 11,403 K.
The fainter secondary, component Ab, is of magnitude 8.86 with an angular separation of along a position angle of 288° from the primary, as of 2005. Visual companions include component B, at a 70.7″ separation from the primary and magnitude 10.73; C, at a separation from B of 3.2″ and magnitude 12.4; as well as D (separation from A of 42.8″ and magnitude 11.9) and E (separation from A of 58.3" and magnitude 11.9).


Phi Lupi

The Bayer designation φ Lupi (Phi Lupi) is shared by two star systems in the constellation Lupus:


HR 6806

HR 6806 is a solitary, orange, main sequence (K2 V) star located thirty-six light-years away, in the constellation Hercules. The star is smaller than the Sun, with around 79% of the solar mass and radius, and 35% of the solar luminosity. It appears to be rotating slowly with an estimated period of 42 days. The star has an inactive chromosphere, with a surface magnetic field strength of 1,500 G. It is around six billion years of age.
There is a nearby brown dwarf, WISE J180901.07+383805.4, at an angular separation of 769″, which would correspond to a projected separation of 8460 AU at the distance of HR 6806. However, this is most likely a typical T7 dwarf, which would place it at a distance of —ruling out a physical association. This is confirmed by the differing proper motion of the star and this object.


HD 88206

HD 88206 is a star in the southern constellation of Vela. It has the Bayer designation Q Velorum and the Gould designation 186G Velorum; "HD 88206" is the identifier from the "Henry Draper catalogue". The star has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.85.
Parallax measurements provide a distance estimate of approximately 1,220 light years from the Sun. It is drifting further away with a radial velocity of +14 km/s. Although a young star and positioned in the general vicinity of the Scorpius–Centaurus Association, it is most likely not a member.
This massive star has a stellar classification of B3III/IV, which suggests it is entering the giant stage of its evolution. It is 24 million years old with 9 times the mass of the Sun and about 4.5 times the Sun's radius. The star is radiating 9,580 times the luminosity of the Sun from its photosphere at an effective temperature of about 17,900 K.


Kepler-40

Kepler-40, formerly known as KOI-428, is an F-type star in the constellation Cygnus. Kepler-40 is known to host at least one planet, Kepler-40b. The star is approximately 1.5 times more massive than the Sun, and is over two times its size; it was, at upon its discovery, the largest yet discovered with a transiting planet in its orbit. Kepler-40 was first noted as home to a possible transiting object by the Kepler spacecraft; the data on the system was released to the public. A team of French and Swiss scientists used follow-up data to determine the existence of the Hot Jupiter planet Kepler-40b, and later had their results published in a scientific journal on January 4, 2011.
Observational history.
Kepler-40 was first targeted by the Kepler spacecraft, an Earth-trailing NASA operation that searches for planets that transit, or cross in front of, their host stars. It was labeled a Kepler Object of Interest (KOI) during the satellite's first 33.5 days of operations, which stretched from mid-May to mid-June 2009, because of the detection of a potential transit event. The data collected by Kepler's photometer was publicly released, including data on Kepler-40 and its possible transiting companion.
Data on Kepler-40 was analyzed by a team of French and Swiss astronomers, who first tested for false positives. When all obvious false positives were cleared, the science team used the SOPHIE échelle spectrograph at the Haute-Provence Observatory in southern France to gather radial velocity measurements on the star. Collected data was then checked to see if it corresponded with that of a closely orbiting binary star or that of a planet; it was found to be that of a planet, leading to the confirmation of Kepler-40b.
After Kepler-40b was confirmed, the French and Swiss science team worked to clarify the stellar parameters its star by analyzing the star's spectrum as collected by SOPHIE. Kepler-40 is the sixth known planetary host star with a radius of more than 1.8 times that of the Sun. At the time of its discovery, Kepler-40 was the most evolved star known to have a transiting planet.
Kepler-40 and its exoplanet were published in the journal "Astronomy and Astrophysics" on January 4, 2011, after being submitted on September 15, 2010.
Characteristics.
Kepler-40 is an F-type star that is 1.48 times the mass of the Sun and 2.13 times its radius. The star has an effective temperature of 6510 K, making it hotter than the Sun. Its metallicity of [Fe/H] = 0.10 means that Kepler-40 has 1.26 times as much iron as the Sun does.
Kepler-40 was, at the time of its discovery, the largest and most evolved star known to host a transiting planet. It is the sixth known host star with a radius over 1.8 times that of the Sun and a transiting planet, after stars that include Kepler-5 and Kepler-7.
Kepler-40 lies approximately 2500 parsecs (8,100 light years) away from Earth, further than any star (with a known distance) with an exoplanet previously discovered by Kepler. With an apparent magnitude of 14.58, it was also dimmer than any star previously recognized by Kepler. Because of its low apparent magnitude, Kepler-40 cannot be seen with the naked eye.
Planetary system.
Kepler-40b is the first (and only) planet discovered so far in the orbit of Kepler-40. It has a mass that is 2.2 times that of Jupiter's, the rough equivalent of 700 Earths. The planet also has a radius that is 1.17 times that of Jupiter and a density of 1.68 grams/cm3. Kepler-40b has an equilibrium temperature of 1620 K, over six times hotter than the equilibrium temperature of Earth. It orbits its star every 6.87 days at a distance of 0.081 AU.


23 Ursae Majoris

23 Ursae Majoris, or 23 UMa, is a binary star system in the constellation Ursa Major, located is approximately 77.7 light years from the Sun. It has the Bayer designation h Ursae Majoris; "23 Ursae Majoris" is the Flamsteed designation. The system is visible to the naked eye as a yellow-white hued star with an apparent visual magnitude of +3.65. It is moving closer to the Earth with a heliocentric radial velocity of −10 km/s.
The primary component is a yellow-white F-type subgiant with an apparent magnitude of +3.65. It has 1.9 times the Sun's mass, 2.9 times the Sun's radius and is emitting 15 times the luminosity of the Sun at an effective temperature of 6,651 K. Orbiting at an angular separation of 22.7 arcseconds is the 9th magnitude secondary companion. There is a magnitude +10.5 optical companion at an angular separation of 99.6 arcseconds.
Nomenclature.
With τ, υ, φ, θ, e and f, it composed the Arabic asterism Sarīr Banāt al-Na'sh, the Throne of the daughters of "Na'sh", and Al-Haud, the Pond. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al-Haud" were the title for seven stars : f as "Alhaud I", τ as "Alhaud II", e as "Alhaud III", this star (h) as "Alhaud IV", θ as "Alhaud V", υ as "Alhaud VI" and φ as "Alhaud VII" .


NGC 273

NGC 273 is an edge-on lenticular galaxy in the constellation Cetus. It was discovered on September 10, 1785 by William Herschel.


Tau Capricorni

The Bayer designation Tau Capricorni (τ Cap, τ Capricorni) is shared by two star systems, in the constellation Capricornus:
They are separated by 0.50° on the sky.


NGC 7033

NGC 7033 is a lenticular galaxy located about 390 million light-years away in the constellation of Pegasus. It is part of a pair of galaxies that contains the nearby galaxy NGC 7034. NGC 7033 was discovered by astronomer Albert Marth on September 17, 1863.
SN 2016cyt.
On July 2, 2016 a type 1a supernova designated as SN 2016cyt was discovered in NGC 7033. It had a maximum apparent magnitude of 18.0.


V378 Normae

V378 Normae, also known as HR 6120, is a star in the constellation Norma. It is a likely Cepheid variable with a range of 6.21 to 6.23 and a period of 3.5850 days.


AB Aurigae

AB Aurigae is a young Herbig Ae star in the Auriga constellation. It is located at a distance of approximately 531 light years from the Sun based on stellar parallax. This pre-main-sequence star has a stellar classification of A0Ve, matching an A-type main-sequence star with emission lines in the spectrum. It has 2.4 times the mass of the Sun and is radiating 38 times the Sun's luminosity from its photosphere at an effective temperature of 9,772 K. The radio emission from the system suggests the presence of a thermal jet originating from the star with a velocity of . This is causing an estimated mass loss of .
This star is known for hosting a dust disk that may harbour a condensing planet or brown dwarf. The star could host a possible substellar companion in wide orbit. The star is part of the young Taurus-Auriga association, which is located in the Taurus Molecular Cloud. The star itself may recently have encountered a dense cloudlet, which disrupted its debris disk and produced an additional reflection nebula.
Planetary system.
In 2017 scientists used the Atacama Large Millimeter/submillimeter Array (ALMA) to take an image of the protoplanetary disk around AB Aurigae. The image showed a dusty disk which has a radius of about 120 astronomical units and a distinct "gap". Inside this gap gaseous spiral arms are detected in CO.
Oppenheimer et al. (2008) observed an annulus feature in AB Aurigae's dust disk between 43 and 302 AU from the star, a region never seen before. An azimuthal gap in an annulus of dust at a radius of 102 AU would suggest the formation of at least one small body at an orbital distance of nearly 100 AU. Such an object could turn out to be either a massive planetary companion or more likely a brown dwarf companion, in both cases located at nearly 100 AU from the bright star. So far the object is unconfirmed.
Observations with ALMA found two gaseous spiral arms inside the disk. These are best explained by an unseen planet with a semimajor axis of about 60-80 au. An additional planet with a semimajor axis of 30 au and with a large pitch angle compared to the disk (likely higher inclination) could explain the emptiness of the inner dusty disk.
External links.
Archived:


Iota Serpentis

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ι Serpentis, Latinized as Iota Serpentis and abbreviated Iot Ser, is a triple star system in the constellation Serpens, in its head (Serpens Caput). It is approximately 190 light years from Earth.
At the centre of the system is a spectroscopic binary, Iota Serpentis A and B. These are both white main sequence dwarfs and both have apparent magnitudes of +5.3. This binary has an orbital period variously reported as 11 or 22 years. First discovered as an astrometric binary, the pair have now been resolved and visual orbits have been derived.
There are two visual companions, Iota Serpentis C, a 13th magnitude star 143 arcseconds away and Iota Serpentis D, a 12th magnitude star 151 arcseconds distant.


8 Draconis

8 Draconis, formally named Taiyi , is a single star in the northern circumpolar constellation of Draco. Based upon an annual parallax shift of 34.14 mas as seen from the Earth, the star is located approximately 96 light-years from the Sun. It is moving further away with a heliocentric radial velocity of +9 km/s, having come within some 2.6 million years ago.
This is an F-type main-sequence star with a stellar classification of F1VmA7(n). It is a Gamma Doradus variable star with a brightness variation of about one tenth of a magnitude. 8 Dra has a relatively high rate of rotation, showing a projected rotational velocity of 120 km/s. The star has 1.56 times the mass of the Sun and 1.50 times the Sun's radius. It is radiating 5.75 times the Sun's luminosity from its photosphere at an effective temperature of 7,129 K. An infrared excess has been detected at wavelengths of 24 and 70μm, which suggests the presence of a circumstellar disk orbiting the star.
Nomenclature.
8 Draconis is the star's Flamsteed designation. It also received the variable star designation IR Draconis in 2000, after its variability had been discovered using Hipparcos photometry.
The star bore the traditional Chinese name of "Taiyi", from 太乙 ("Tài Yǐ") or 太一 ("Tài Yī", the Great One), both of which refer to Tao. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Taiyi" for this star on 30 June 2017 and it is now so entered on the List of IAU-approved Star Names.


Black Widow Pulsar

The Black Widow Pulsar (PSR B1957+20) is an eclipsing binary millisecond pulsar in the Milky Way. Discovered in 1988, it is located roughly 6,500 light-years away from Earth. It orbits with a brown dwarf or Super-Jupiter companion with a period of 9.2 hours with an eclipse duration of approximately 20 minutes. When it was discovered it was the first such pulsar known. The prevailing theoretical explanation for the system implied that the companion is being destroyed by the strong powerful outflows, or winds, of high-energy particles caused by the neutron star, and so the sobriquet "black widow" was applied to the object. Subsequent to this, other objects with similar features have been discovered, and the name has been applied to the class of millisecond pulsars with an ablating companion.
Later observations of the object showed a bow shock in H-alpha and a smaller-in-extent shock seen in X-rays (as observed by the Chandra Space Telescope), indicating a forward velocity of approximately a million kilometers per hour.
In 2010 it was estimated that the neutron star's mass was at least formula_1, and possibly as high as formula_2 (the latter of which, if true, would surpass PSR J0740+6620 for the title of most massive neutron star yet detected, and place it within range of the Tolman–Oppenheimer–Volkoff limit).
Planets.
The pulsar has a substellar companion, possibly a brown dwarf.
Gallery.
Artist impressions of the Black Widow Pulsar.


Tau Persei

Tau Persei (τ Per), also known as 18 Persei, is a binary star in the constellation of Perseus. The system is fairly close, and is located about 254 light-years (78 parsecs) away, based on its parallax.
Tau Persei is an eclipsing binary, which means the two stellar components orbit each other in such an orientation that they periodically eclipse each other, while blocking the other's light. Unlike many eclipsing binaries that have short orbital periods, Tau Persei has an orbital period of 4.15 years. With a semi-major axis of 0.055 arcseconds, this is one of the few eclipsing binaries whose components can be resolved with interferometry.
The primary component of Tau Persei is a red giant with a spectral type of G8III. It has a radius 16 times that of the Sun, and is about 390 million years old. Its companion is an A-type main-sequence star. In 1989, the primary star eclipsed the secondary, allowing for the stellar parameters to be derived via its light curve.
Naming.
In Chinese, (), meaning "Mausoleum", refers to an asterism consisting of τ Persei, 9 Persei, ι Persei, κ Persei, β Persei, ρ Persei, 16 Persei and 12 Persei. Consequently, the Chinese name for τ Persei itself is (, .).


Nu Cancri

Nu Cancri, Latinized from ν Cancri, is a binary star in the zodiac constellation of Cancer. It is faintly visible to the naked eye with an apparent visual magnitude of +5.46. Based upon an annual parallax shift of 8.31 mas as seen from the Earth, the star is located roughly 390 light years from the Sun.
This is a single-lined spectroscopic binary system with an orbital period of 3.8 years and an eccentricity of 0.35. The primary, component A, is a white-hued A-type giant star with a stellar classification of A0 III. It is a magnetic Ap star with a field strength of , showing abundance peculiarities in strontium, chromium, and mercury. The star has 2.8 times the mass of the Sun and is radiating 93 times the Sun's luminosity from its photosphere at an effective temperature of 10,250 K.


Psi Pegasi

Psi Pegasi, which is Latinized from ψ Pegasi, is a binary star system within the great square in the northern constellation of Pegasus. It has a red hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.66. This object is located at a distance of approximately 476 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of −6.6 km/s.
The orbital elements for this system were computed for the first time in 2004 based on interferometric observations, yielding an orbital period of roughly 55 years and an eccentricity of about 0.19. The visible component is an aging red giant star on the asymptotic giant branch with a stellar classification of M3III. It is a suspected variable, probably semiregular, with its magnitude varying from 4.63 to 4.69 over periods of 37.4 and 118.9 days. With the supply of hydrogen exhausted at its core, the star has cooled and expanded to around 98 times the Sun's radius. It is radiating 960 times the luminosity of the Sun from its bloated photosphere at an effective temperature of 3,882 K.


HD 33636

HD 33636 is a binary system located approximately 94 light-years away in Orion constellation. The visible member HD 33636 A is a 7th magnitude yellow main-sequence star. It is located at a distance of 91.6 light years from Earth. It has a metallicity of −0.05 ± 0.07.
A companion was discovered in 2002 with a minimum mass of planet size. This was ascertained to be a low-mass star in 2007, making it HD 33636 B.
HD 33636 B.
HD 33636 B was discovered in 2002 by the Keck telescope in Hawaii. It was independently detected at the Haute-Provence Observatory in France. With this method it showed a minimum mass of 10.58 Jupiter masses, and was initially assumed to be a planet and provisionally labelled "HD 33636 b" (lower-case).
In 2007, Bean et al. used the Hubble Space Telescope (HST) and he found that this body has an inclination as little as 4.1 ± 0.1°, which yielded the true mass of 142 Jupiter masses. This is too high to be a planet. It is now classified as an M-dwarf star of spectral type M6V, "HD 33636 B" (upper-case).
This star takes 2117 days or 5.797 years to orbit at the average distance of 3.27 Astronomical Units (AU).


26 Canis Majoris

26 Canis Majoris is a variable star in the southern constellation of Canis Major, located around 1,010 light years away from the Sun. It has the variable star designation MM Canis Majoris; "26 Canis Majoris" is the Flamsteed designation. This object is visible to the naked eye as a dim, blue-white hued star with a baseline apparent visual magnitude of 5.89. It is moving further from the Earth with a heliocentric radial velocity of +22 km/s.
With a stellar classification of B2 IV/V, it appears as a B-type main-sequence star intermixed with traits of an evolving subgiant star. Samus et al. (2017) classify it as a slowly pulsating B-type variable star (SPB), which ranges from magnitude 5.84 down to 5.87 with a rotationally-modulated period of 2.72945 days. Briquet et al. (2007) describe it as a chemically peculiar He-variable star, having inhomogeneous distributions of chemical elements across its surface. It has a variable, quasi-dipolar magnetic field, resulting in variations of the magnetic field and line strengths as it rotates.
This star is around 3.6 million years old with a rotation period of 2.7 days. It has 5.5 times the mass of the Sun and 3.25 times the Sun's radius. The star is radiating 1,000 times as much luminosity as the Sun from its photosphere at an effective temperature of 16,157 K.


NGC 3794

NGC 3794, also cataloged in the New General Catalogue as NGC 3804, is a low-surface-brightness galaxy in the constellation Ursa Major. It is very far from Earth, with a distance of about . It was discovered on April 14, 1789 by the astronomer William Herschel.


Kappa Lyrae

κ Lyrae, Latinized as Kappa Lyrae, is a solitary star in the northern constellation of Lyra, near the constellation border with Hercules. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.33. This object is located approximately 238 light years from the Sun based on parallax, but is moving closer with a radial velocity of −24 km/s.
This is an aging giant star with a stellar classification of K2-IIIabCN0.5, with the suffix notation indicating a mild underabundance of cyanogen. Having exhausted the supply of hydrogen at its core, the star has cooled and expanded. It now has 18 times the Sun's girth and is radiating 127 times the luminosity of the Sun at an effective temperature of 4,638 K. κ Lyrae is a red clump giant, which means it is on the horizontal branch and is generating energy through core helium fusion. It is a suspected small amplitude variable star.


Q Carinae

The Bayer designations q Carinae and Q Carinae are distinct.


A Puppis

The Bayer designations a Puppis and A Puppis are distinct and refer to two different stars in the constellation Puppus:


HD 85725

HD 85725 is a high proper-motion star in the constellation Antlia. Located around 176 light-years distant, it is 1.431 times as massive as the Sun and has a surface temperature of 5,855 K.


NGC 6334

NGC 6334, colloqually known as the Cat's Paw Nebula, Bear Claw Nebula, or Gum 64, is an emission nebula and star-forming region located in the constellation Scorpius. It was discovered by astronomer John Herschel in 1837, who observed it from the Cape of Good Hope in South Africa. The nebula is located in the Carina–Sagittarius Arm of the Milky Way, at a distance of approximately from the Sun.
The nebula is a high mass filamentary cloud structure spanning . Several embedded star-forming regions have been identified from infrared and radio emissions. Four of these sites have formed H II regions.


NGC 3294

NGC 3294 is a spiral galaxy in the constellation Leo Minor. It was discovered by William Herschel on Mar 17, 1787.


HD 45350

HD 45350 is an 8th magnitude star located approximately 160 light-years away in the constellation of Auriga. It is a yellow subgiant (spectral type G5 IV), a Sun-like star that is finishing hydrogen fusion in its core. Although slightly cooler, it is brighter, although not much considering its subgiant status. However, the star is very old and will soon start to expand becoming finally a red giant.
The star HD 45350 is named Lucilinburhuc. The name was selected in the NameExoWorlds campaign by Luxembourg, during the 100th anniversary of the IAU. The Lucilinburhuc fortress was built in 963 by the founder of Luxembourg, Count Siegfried. The year 2019-2020 class of 3B from the Luxembourgish Echternach high school won the contest to name both the star and its planet. The students who helped name both celestial objects were Lucien Nicolas Berger, Léna Boucq Kieffel, Ben de Boer, Cédric Dehlez, Nicolas Delhez, Sergio Manuel Dias Costa, Pierre Fusshoeller, Jil Menei, Philippe Schaack and Claire Zeien. The overseeing committee members who organized the contest and the vote of the respective celestial objects were Eric Buttini, Patrick Michaely, Nicolas Faber, Jeanny-Jungbluth-Schmidt and Yanna Di Ronco.
Planetary system.
In January 2005, the discovery of a very eccentric extrasolar planet orbiting the star was announced by the California and Carnegie Planet Search team.


NGC 493

NGC 493, also occasionally referred to as PGC 4979 or GC 281, is a barred spiral galaxy in the constellation Cetus. It is located approximately 90 million light-years from Earth and was discovered on December 20, 1786 by astronomer William Herschel. It was later also observed by his son, John Herschel. John Dreyer, creator of the New General Catalogue, described the galaxy as "very faint, large, much extended 60°" with "a little brighter middle".


Kepler-395c

Kepler-395c is a potentially habitable exoplanet 616 light-years away in the constellation of Cygnus.
Habitability and Properties.
It orbits an M-type star. Its radius is 1.32 ± 0.09 times that of Earth. It orbits at 0.177 AU with an orbital period of 34.9893 days. Because of its proximity to its star, its likely to be tidally locked, meaning one side always facing the star, and one side always facing away. This means one side is blistering hot and one side is bitter cold. However, in between those hostile zones, there would be a sliver of habitability. If it has a thick enough atmosphere, the sliver may even be global.


V Cephei

V Cephei is a white main sequence star in the constellation Cepheus. It only varies slightly by 0.03 of a magnitude. It was suspected of being variable by American astronomer Seth Carlo Chandler noting in 1890 that it varied by 0.7 magnitude but that it needed more confirmation. Subsequent observers were divided in whether they noted variability or not. A subsequent study with photoelectric photometry showed no variability.


Gliese 673

Gliese 673 is an orange dwarf star in the constellation Ophiuchus. It has a stellar classification of K7V. Main sequence stars with this spectra have a mass in the range of 60-70% of solar mass () (comparable to the members of the binary star system 61 Cygni).
This star is relatively near our Sun at a distance of about 25 light years. In spite of this proximity, however, it is still too faint to be viewed by the unaided eye. It is considered a slowly rotating star with a relatively high proper motion.
Gliese 673 is among nearby K-type stars of a type in a 'sweet spot’ between Sun-analog stars and M stars, in terms of the likelihood of life and its ease of detectability (in this case for planets in the system's outer conservative habitable zone), per analysis of Giada Arney from NASA’s Goddard Space Flight Center.


W Cephei

W Cephei is a spectroscopic binary and variable star located in the constellation Cepheus. It is thought to be a member of the Cep OB1 stellar association at about 8,000 light years. The supergiant primary star, known as W Cephei A, is one of largest known stars and as well as one of most luminous red supergiants.
Discovery.
W Cephei was reported in 1896 as a red star varying from magnitude 7.3 to 8.3. It was catalogued as BD+57°2568 in the Bonner Durchmusterung published in 1903, and HD 214369 in the Henry Draper Catalogue.
In 1925, W Cep was included in a listing of Be stars. It was recognised as a cool star with spectral type Mep. It was classified as K0ep Ia from a 1949 spectrum, but also recognised to have a small hot companion, plus an unusual infrared excess. Ultraviolet spectra allowed absorption lines from the companion to be studied and it was given a spectral type of B0-1.
System.
The W Cephei system contains a luminous red supergiant star with a non-supergiant early B companion. The star has unusual emission lines including both permitted and forbidden FeII, produced by a circumstellar envelope containing dust and ionised gas. The two components have been resolved at 0.262" using Speckle interferometry. An orbital period of 2,090 days has been proposed.
Variability.
W Cephei varies in brightness from 7th to 9th magnitude. The General Catalogue of Variable Stars lists it as a semiregular variable but attempts to find a period have shown only random variations.


Kappa Canis Majoris

Kappa Canis Majoris, Latinized from κ Canis Majoris, is a solitary, blue-white hued star in the constellation Canis Major. It is visible to the naked eye with an apparent visual magnitude of +3.87. Based upon an annual parallax shift of 7.70 mas as seen from Earth, this star is located about 660 light years from the Sun.
This is a B-type main-sequence star with a stellar classification of B1.5 Ve, although Hiltner et al. (1969) classified it as B1.5 IVe suggesting it is a subgiant star. The 'e' suffix indicates it is a rapidly rotating Be star with a circumstellar decretion disk of heated gas. The radius of the emitting disk is about , or about 3.7 times the radius of the star. It is classified as a Gamma Cassiopeiae type variable star and its brightness varies from magnitude +3.4 to +3.97. The star became 50% brighter between 1963 and 1978, increasing from magnitude 3.96 or so to 3.52.
Naming.
In Chinese, (), meaning "Bow and Arrow", refers to an asterism consisting of κ Canis Majoris, δ Canis Majoris, η Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris and π Puppis. Consequently, κ Canis Majoris itself is known as (, .)


Honores Friderici

Honores Friderici or Frederici Honores, (Latin, "the Honours, or Regalia, of Frederic") also called Gloria Frederica or Frederici ("Glory of Frederick") was a constellation created by Johann Bode in 1787 to honor Frederick the Great, the king of Prussia who had died in the previous year. It was between the constellations of Cepheus, Andromeda, Cassiopeia and Cygnus. Its most important stars were Iota, Kappa, Lambda, Omicron, and Psi Andromedae. The constellation is no longer in use.
History.
Johann Bode first introduced the constellation in his 1787 publication "Astronomisches Jahrbuch", calling it "Friedrichs Ehre", to honour Frederick the Great, who had just died the previous year. He latinized its name to Honores Friderici in his 1801 work "Uranographia".
He illustrated it as a crown above a sword, pen and olive branch, based on his perception of Frederick as a "hero, sage and peacemaker".
The constellation was taken up by some cartographers and not by others, but was increasingly ignored from the latter half of the 19th century, and is no longer in use. Most of it lies within the borders of modern Andromeda, with parts in Cassiopeia, Cepheus and Pegasus.
Stars.
Bode incorporated 76 stars into his new constellation, made up of 26 from Andromeda, 9 from Lacerta, 6 from Cepheus, 5 from Pegasus, and 3 from Cassiopeia. The three brightest stars—all of magnitude 4—that lay within its borders are Omicron, Lambda, and Kappa Andromedae. With an apparent magnitude of 3.62, Omicron Andromedae is a multiple star system, the brightest star of which is a blue-white subgiant of spectral type B6 IIIpe and its visible companion a white star of spectral type A2. Each appears to have a close companion, making it a quadruple system. It is approximately 690 light-years from Earth. Lambda Andromedae is a yellow subgiant star of spectral type G8IVk around 1.3 times as massive as the Sun that has used up its core hydrogen and expanded to around 7 times its diameter. It is a spectroscopic binary composed of two stars close together orbiting each other every 20 days, the brighter component a RS Canum Venaticorum variable. Kappa Andromedae is a blue white star of apparent magnitude 4.14, that was found to have a substellar companion by direct imaging in 2012. Initially thought to be a planet, it is now thought to be a brown dwarf around 22 times as massive as Jupiter.
Iota and Psi Andromedae make up the asterism. Shining at magnitude 4.29, Iota Andromedae is a blue-white main sequence star of spectral type B8V around 500 light-years distant from Earth.


HN Pegasi

HN Pegasi is the variable star designation for a young, Sun-like star in the northern constellation of Pegasus. It has an apparent visual magnitude of 5.9, which, according to the Bortle scale, indicates that it is visible to the naked eye from suburban skies. Parallax measurements made by the Hipparcos spacecraft put the star at a distance of around 58 light years.
This is a G-type main sequence star with a stellar classification of and an estimated age of just 237 million years. It has slightly more mass and a slightly larger radius than the Sun, but a somewhat lower metallicity. It is spinning relatively quickly, with an estimated rotation period of 4.84 days.
The surface magnetic field of the star has a complex and variable geometry. It is a BY Draconis variable star with an active chromosphere, which means there is a rotational modulation of its luminosity due to star spots. Much like the Sun, the star spot activity undergoes a periodic cycle of maxima and minima lasting roughly yr. Its apparent magnitude varies between a maximum of 5.92 and a minimum of 5.95 over a period of 24.9 days. However, the rotation period is on average 4.84 days. The star shows an anti-solar pattern of rotation, with the rotation rate steadily increasing during each cycle before dropping back to the initial value upon the start of a new cycle.
In 2007, the discovery of a brown dwarf companion was announced. HN Peg B was spotted using the Spitzer Space Telescope at an angular separation of 43.2 arc sec, showing a methane emission characteristic of T-type dwarfs. The separation corresponds to a projected physical distance of 795 AU, which is uncommonly wide for such brown dwarf companions. The estimated mass of the object is 28 MJ. Based upon its spectrum, HN Peg B has relatively thin cloud decks.
This star displays an emission of infrared excess that suggests there is a circumstellar disk of debris in orbit. HN Pegasi is most likely a thin disk population star. It is a member of the nearby Hercules-Lyra association of stars that share a common motion through space.


Kepler-44

Kepler-44,formerly known as KOI-204, is a star in the northern constellation of Cygnus. It is located at the celestial coordinates: Right Ascension , Declination . With an apparent visual magnitude of 16, this star is too faint to be seen with the naked eye.
Planetary system.
The Kepler spacecraft detected a transiting planet candidate around this star that was confirmed by radial velocity measurements taken by the SOPHIE spectrograph mounted on the 1.93 m telescope at the Haute-Provence Observatory.
The planet is likely to be tidally locked to the parent star. In 2015, the planetary nightside temperature was estimated to be equal to 2347 K.


HD 72659

HD 72659 is a star in the equatorial constellation of Hydra. With an apparent visual magnitude of 7.46, his yellow-hued star is too faint to be viewed with the naked eye. Parallax measurements provide a distance estimate of 169.5 light years from the Sun, and it has an absolute magnitude of 3.98. The star is drifting closer with a radial velocity of −18.2 km/s.
This is a Sun-like main sequence star with a stellar classification of G2V, indicating that it is generating energy through core hydrogen fusion. It is older than the Sun with an age of about seven billion years, and is spinning with a projected rotational velocity of 5.1 km/s. The star has 7% greater mass than the Sun and a 38% larger radius. It is radiating more than double the Sun's luminosity from its photosphere at an effective temperature of 5,956 K. The metallicity of the stellar atmosphere is similar to the Sun.
Planetary system.
An extrasolar planet was discovered orbiting this star in 2003 via the Doppler method. This is a superjovian planet with an eccentric orbit, completing a lap around its host star every .


UZ Pyxidis

UZ Pyxidis (HD 75021) is a semiregular variable star in the constellation Pyxis. It is located about 6,000 light-years (2,000 parsecs) away from the Earth.
UZ Pyxidis lies directly between α and γ Pyxidis. It has a common proper motion companion, HD 75022, less than 2' away but the two are not listed in double star catalogues.
UZ Pyxidis is a carbon star. These types of stars are known for having large amounts of carbon in their atmospheres, forming carbon compounds that make the star appear strikingly red. It was first recognised as having an unusual spectrum in 1893. Under the Morgan–Keenan classification of carbon stars, UZ Pyxidis' spectral type is C55; if it were a normal giant star, this would correspond to a spectral type of about K5. It is also unusual in that it has very strong isotopic bands of C2 and CN.
UZ Pyxidis is classified as a semiregular variable with a dominant period of 159.6 days. It varies in brightness between magnitude 6.99 and 7.63. The variability was first reported in 1972, and the variable star designation UZ Pyxidis was assigned in 1978.


QW Puppis

QW Puppis (QW Pup) is a class F3V (yellow-white dwarf) star in the constellation Puppis. Its apparent magnitude is 4.49 and it is approximately 69.9 light years away based on parallax.
It is a Gamma Doradus variable, ranging from 4.5 to 4.47 magnitude with a period of 0.96 days.


NGC 6530

NGC 6530 is an open cluster in the constellation Sagittarius. It has a diameter of 10 arc minutes, with stars as bright as 7th magnitude. It exists within nebula Messier 8, the Lagoon Nebula.


Luyten b

Luyten b (more commonly known as Gliese 273b) is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the nearby red dwarf Luyten's Star. It is one of the most Earth-like planets ever found and is the fifth-closest potentially habitable exoplanet known, at a distance of 12.2 light-years. Only Proxima Centauri b, Barnard's Star b, Ross 128 b, and Gliese 1061 d are closer. Discovered alongside Gliese 273c in June 2017, Luyten b is a Super-Earth of around 2.89 times the mass of Earth and receives only 6% more starlight than Earth, making it one of the best candidates for habitability. In October 2017 and 2018, the nonprofit organization METI (Messaging Extraterrestrial Intelligence) sent a message containing dozens of short musical compositions and a scientific "tutorial" towards the planet in hopes of contacting any potential extraterrestrial civilizations.
Characteristics.
Mass, Radius, and Temperature.
Mass and Size.
Luyten b is a Super-Earth, meaning that it has a mass and/or radius greater than that of Earth, but less than that of Uranus or Neptune. Radial velocity measurements shows that the planet has a minimum mass of 2.89 , placing it at the lower end of the Super-Earth range. The planet has not been found to transit its star, and as a result its true mass and radius are not known. For an Earth-like composition, Luyten b would have to be about 1.4 . Due to its low mass, the planet is likely terrestrial, with a radius below 1.5 . In addition, it is one of the least massive planets found within the nearest 20 light-years.
Temperature and Atmosphere.
The planet receives an incident flux only 6% greater than that of Earth. With an estimated albedo, or proportion of light reflected by the planet, of 0.30, Luyten b has an equilibrium temperature of 259 °K. For comparison, Earth has an equilibrium temperature of 255 °K. With an Earth-like atmosphere — if it has one — Luyten b would have an average surface temperature of about , very similar to that of Earth.
Orbit and Rotation.
Luyten b orbits quite close to its host star. One full revolution around Luyten's Star takes about 18.6 days at an average distance of 0.091 AU, much closer in than Mercury, which has a year of 88 days and an orbital radius of 0.387 AU. However, because the host star is so dim, Luyten b falls right within the system's habitable zone and only receives 6% more starlight than Earth. While most planets this close to their parent star would be tidally locked, Luyten b has a moderately high orbital eccentricity of which may allow the planet to be captured in a spin-orbit resonance, where the planet's rotation and orbital period can be simplified down to small integers (3:2, 1:2).
Host Star.
Luyten's Star is a medium-sized red dwarf star on the main sequence. It has 29.3% the radius, 29% the mass, 0.88% the luminosity of the Sun, and has an effective temperature of 3,382 °K. Unlike many nearby red dwarfs, like Proxima Centauri, Luyten's Star is very inactive with a long rotation period of over 118 days.
Habitability.
Similarity to Earth.
Luyten b is one of the most Earth-like planets ever found. The first factor in its potential habitability is its distance from the host star. With an orbital radius of about 0.0911 AU, and given the star's low luminosity, Luyten b is orbiting well within the habitable zone. This is the region around a star where temperatures are just right for liquid water to pool on a planet's surface, given sufficient atmospheric pressure. Many other factors are also in favor of Luyten b's potential habitability. It's only about 2.89 times the mass of Earth, almost certainly making it a rocky planet. The gray zone between rocky and gaseous planets is believed to be around 6–8 , in which planets above 8  earth would be more akin to mini Neptune(s). Luyten b's minimum mass falls well below the 6–8  transition, and the chances for its actual mass to exceed the lower limit of the gray zone are only around 12%.
Temperature.
In addition to its likely terrestrial nature, Luyten b is quite close in temperature to Earth, with an of 259 °K. The planet is exposed to a stellar incident flux of 1.06 times that of Earth – not enough to cause a runaway greenhouse effect: That would take more than 1.5 . While temperatures would probably be much higher on the direct star-facing side, a thick enough atmosphere would be able to distribute heat around the planet, providing life-friendly conditions to more of the planet. If Luyten b is found to be in a spin-orbit resonance with a rotation period less than or close to its orbital period, then this global heat distribution effect would be more efficient.
Interactions With Host Star.
Unlike many other potentially habitable exoplanets orbiting red dwarfs, like Proxima b and the TRAPPIST-1 planets, Luyten b has the advantage of orbiting a very quiet host. Luyten's Star has a very long rotational period of 118 days and is not prone to powerful solar flares. Strong enough flare events can strip the atmospheres of orbiting planets and eliminate their chances of habitability; a good example of this is Kepler-438b. However, with the low activity of its host, Luyten b is likely to retain any atmosphere for billions of years, potentially enabling the development of life as we know it.


NGC 7042

NGC 7042 is a spiral galaxy located about 210 million light-years away in the constellation of Pegasus. NGC 7042 is part of a pair of galaxies that contains the galaxy NGC 7043. Astronomer William Herschel discovered NGC 7042 on October 16, 1784.
On October 23, 2013 a Type Ia supernova designated as SN 2013fw was discovered in NGC 7042.


Phi Persei

Phi Persei (Phi Per, φ Persei, φ Per) is a Class B2Vpe, fourth-magnitude star in the constellation Perseus. Phi Persei is binary consisting of a blue main sequence primary of class B2 and an apparent magnitude of 4.01 and a hot subdwarf secondary. Due to its rapid rotation, the primary has a polar radius about and an equatorial radius of about . Phi Persei is also a variable star with rapid variations in its brightness and spectrum. The Phi Persei stellar system is located about 716 light-years from Earth.
Naming.
Flamsteed followed Ptolemy in treating φ Persei as being in Andromeda and gave it the designation 54 Andromedae. It is isolated from the main stars of Perseus, but lies within its formal borders.
In Chinese, (), meaning "Heaven's Great General", refers to an asterism consisting of φ Persei, γ Andromedae, 51 Andromedae, 49 Andromedae, χ Andromedae, υ Andromedae, τ Andromedae, 56 Andromedae, β Trianguli, γ Trianguli and δ Trianguli. Consequently, the Chinese name for φ Persei itself is (, .).


Beta Herculis

Beta Herculis (β Herculis, abbreviated Beta Her, β Her), formally named Kornephoros , or Rutilicus, is a binary star and the brightest star in the northern constellation of Hercules at a base apparent visual magnitude of 2.81. This is a suspected variable star with an apparent magnitude that may rise as high as 2.76. Based upon parallax measurements, it is located at a distance of from the Sun.
Although Beta Herculis appears to the naked eye to be a single star, in July 1899 the American astronomer W. W. Campbell discovered from spectroscopic measurements that its radial velocity varies, and concluded that it has a companion.
Properties.
At Palomar Observatory, Antoine Labeyrie and others used speckle interferometry with the Hale Telescope to resolve the system in 1977. The Hipparcos satellite observed the orbital motion of the primary relative to other stars, and an orbit was computed in 2005 using spectroscopic data together with these measurements. The period of the system is around 410 days. They have a high orbital eccentricity of 0.55 and the orbital plane is inclined 53.8° to the line of sight from the Earth.
The primary star has a stellar classification of G7 IIIa, indicating that it is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence. It has a mass nearly three times the mass of the Sun, and has expanded to 17 times the Sun's radius. The effective temperature of the star's outer envelope is about 4,887 K, which gives it the yellow hue of a G-type star. The secondary star has a mass only 90% that of the Sun.
Nomenclature.
"β Herculis" (Latinised to "Beta Herculis") is the star's Bayer designation.
It bore the traditional names "Kornephoros", a Greek word meaning "club bearer", and "Rutilicus", a corruption of the Latin word "titillicus", meaning "armpit". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Kornephoros" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
It was a member of the indigenous Arabic asterism "al-Nasaq al-Shāmī", "the Northern Line" of "al-Nasaqān" "the Two Lines", along with Gamma Herculis, Gamma Serpentis and Beta Serpentis. Though, according to a 1971 NASA catalog, "al-Nasaq al-Sha'āmī" or "Nasak Shamiya" was the title for three other stars: Beta Serpentis as "Nasak Shamiya I", Gamma Serpentis as "Nasak Shamiya II" and Gamma Herculis as "Nasak Shamiya III".
In Chinese, (), meaning "Right Wall of Heavenly Market Enclosure", refers to an asterism which represents eleven old states in China and which is marking the right borderline of the enclosure, consisting of Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Beta Serpentis, Delta Serpentis, Alpha Serpentis, Epsilon Serpentis, Delta Ophiuchi, Epsilon Ophiuchi and Zeta Ophiuchi. Consequently, the Chinese name for Beta Herculis itself is (, ), represent "Hézhōng" (河中), possibly Hezhong Municipality or Hezhong Circuit (see : Wang Chongrong, formally the Prince of Langye 瑯琊王, was a warlord of the late Chinese Tang Dynasty who controlled Hezhong Circuit, headquartered in modern Yuncheng, Shanxi). "Hézhōng" (河中) was westernized into "Ho Chung" by R.H. Allen, which means "in the river".
Namesake.
USS Rutilicus (AK-113) was a United States Navy Crater class cargo ship named after the star.


NGC 7606

NGC 7606 is a spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 100 million light years from Earth, which, given its apparent dimensions, means that NGC 7606 is about 165,000 light years across. It was discovered by William Herschel on September 28, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 45 arcminutes northeast from psi2 Aquarii. It can be seen with a 4 inch telescope but its visibility is greatly affected by light pollution.
Characteristics.
NGC 7606 is a spiral galaxy seen on inclination. It has a bright nucleus surrounded by a prominent bulge, which is seen elliptical due to the inclination. No bar has been observed. A ring with an apparent diameter of 0.85 arcminutes has been detected at the central part of the galaxy. The galaxy features two main arms, that can be traced for nearly 360°, and several arm fragments. The arms are smooth and rather tight, although not as tightly wound as the ones of NGC 488. Few bright spots have been observed in the arms. The galaxy is found to host a supermassive black hole, whose mass based on bulge velocity dispersion σ is estimated to be 15-22 million . NGC 7606 is an isolated galaxy.
Two supernovae have been observed in NGC 7606, SN 1965M (magnitude 16.0), and SN 1987N (type Ia, magnitude 13.8).


Upsilon Ophiuchi

Upsilon Ophiuchi is a triple star system in the equatorial constellation of Ophiuchus. It has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.62. The distance to this system is approximately 134 light years based on parallax. It is drifting closer with a radial velocity of −30.6 km/s.
The variable radial velocity of the brighter component was first observed by H. A. Abt in 1961. It is a double-lined spectroscopic binary system with an orbital period of 27.2 days and an eccentricity of 0.74. They have a combined magnitude of 4.71. Both components are similar stars with a combined stellar classification of kA2hA5VmA5, and one or both are Am stars. The third component has an 82.8 year orbit with the inner pair at an eccentricity of 0.45. The system is a source for X-ray emission.


NGC 5308

NGC 5308 is an edge-on lenticular galaxy in the constellation of Ursa Major. It was discovered on 19 March 1790 by William Herschel. It was described by John Louis Emil Dreyer as "bright, pretty large" when he compiled the New General Catalogue. A small, irregular galaxy near NGC 5308 has been given the designation LEDA 2802348.
NGC 5308 was imaged by the Hubble Space Telescope in 2016. The galaxy appears to be a flat, smooth disk, typical of most lenticular galaxies. Many large globular clusters orbit the galaxy; these are visible as tiny dots surrounding the galaxy, and are mostly made of old, aging stars similar to the galaxy itself.
SN 1996bk, a type Ia supernova, was discovered in NGC 5308 in October 1996. The supernova was 10.5" south and 17.9" west of center of the galaxy, and had an apparent visual magnitude of 15.


Omicron Eridani

ο Eridani (Latinised as Omicron Eridani) refers to two distinct star systems in the constellation of Eridanus: