47 Capricorni

47 Capricorni is a variable star located around 1,170 light years from the Sun in the southern constellation Capricornus, near the northern border with Aquarius. It has the variable star designation of AG Capricorni and a Bayer designation of c2 Capricorni; "47 Capricorni" is the "Flamsteed designation". This object is visible to the naked eye as a dim, red-hued point of light with an apparent visual magnitude that varies between 5.90 and 6.14. The star is receding from the Earth with a heliocentric radial velocity of +20 km/s.
This is an aging red giant star with a stellar classification of M2III. It is a semiregular variable star of subtype SRb with a period of 30.592 days and a maximum brightness of 5.9 magnitude. With the supply of hydrogen at its core exhausted, the star has expanded to around 102 times the Sun's radius. It is radiating 1,940 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,784 K.


Eta Hydrae

Eta Hydrae (η Hydrae) is the Bayer designation for a star in the equatorial constellation of Hydra. With an apparent visual magnitude of 4.3, it is visible to the naked eye. However, it is the faintest of the five stars that form the "head" of the hydra. Based upon an annual parallax shift of 5.56 mas, it is located roughly 590 light years from the Sun.
This is a B-type main sequence star with a stellar classification of B3V. It has been classified as a candidate Beta Cephei variable with a period of 2.2 days, although this designation was rejected by Stankov and Handler (2005). The spectrum shows a slight underabundance of carbon, compared to the Sun. The star is around 32 million years old and is spinning with a projected rotational velocity of 101 km/s. It has an estimated seven times the mass of the Sun and nearly four times the Sun's radius. Eta Hydrae radiates 2,680 times the solar luminosity from its outer atmosphere at an effective temperature of 18,630 K.
Name and etymology.
This star, along with δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir), were Ulug Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Min al Azʽal" or "Minazal" were the title for five stars:δ Hya as "Minazal I", η Hya as "Minazal II", ε Hya as "Minazal III", ρ Hya as "Minazal IV" and ζ Hya as "Minazal V" (exclude σ Hya).
In Chinese, (), meaning "Willow", refers to an asterism consisting of η Hydrae, δ Hydra, σ Hydrae, ρ Hydrae, ε Hydrae, ζ Hydrae, ω Hydrae and θ Hydrae Consequently, η Hydrae itself is known as (, ).
The people of Groote Eylandt called "Unwala", "The Crab", for the star cluster including this star, δ Hya (Lisan al Sudja), ε Hya, ζ Hya, ρ Hya and σ Hya (Minchir).


Tau2 Eridani

Tau2 Eridani (τ2 Eridani, abbreviated Tau2 Eri, τ2 Eri), formally named Angetenar , is a star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude of 4.78. The distance to this star, as determined via the parallax method, is around 187 light-years.
Nomenclature.
"τ2 Eridani" (Latinised to "Tau2 Eridani") is the system's Bayer designation. It is one of a series of stars that share the Bayer designation Tau Eridani.
It bore the traditional name "Angetenar", derived from the Arabic "Al Ḥināyat an-Nahr", 'the Bend in the River', near which it lies. 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 "Angetenar" for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "Celestial Meadows", refers to an asterism consisting of Tau2 Eridani, Gamma Eridani, Pi Eridani, Delta Eridani, Epsilon Eridani, Zeta Eridani, Eta Eridani, Pi Ceti, Tau1 Eridani, Tau3 Eridani, Tau4 Eridani, Tau5 Eridani, Tau6 Eridani, Tau7 Eridani, Tau8 Eridani and Tau9 Eridani. Consequently, the Chinese name for Tau2 Eridani itself is (, .)
Properties.
Tau2 Eridani is an evolved K-type giant star with a stellar classification of K0 III. It is a red clump giant on the horizontal branch of the Hertzsprung–Russell diagram, indicating that is it now generating energy through the thermonuclear fusion of helium at its core.
Around 660 million years old, Tau2 Eridani has 2.4 times the mass of the Sun and has expanded to over 8 times the solar radius. It shines with nearly 43 times the Sun's luminosity from an outer atmosphere that has an effective temperature of 5,049 K.
It is a member of the Galactic thin disk population.


NGC 986

NGC 986 is a barred spiral galaxy in the constellation of Fornax, located about 56 million light-years away. The galaxy contains two large, extended and slightly warped arms that begin at each end of the central bar. It was discovered in 1826 by the Scottish astronomer James Dunlop.


NGC 3923

NGC 3923 is an elliptical galaxy located in the constellation Hydra. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 3923 is about 155,000 light years across. NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. It has more than twenty shells. It was discovered by William Herschel on March 7, 1791.
Characteristics.
NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers. NGC 3923 has up to 42 shells, the highest number among all shell galaxies, and its shells are much more subtle than those of other shell galaxies. The shells of this galaxy are also symmetrical, while other shell galaxies are more skewed. Concentric shells of stars enclosing a galaxy are quite common and are observed in many elliptical galaxies. In fact, every tenth elliptical galaxy exhibits this onion-like structure, which has never been observed in spiral galaxies. The shell-like structures are thought to develop as a consequence of galactic cannibalism, when a larger galaxy ingests a smaller companion. As the two centers approach, they initially oscillate about a common center, and this oscillation ripples outwards forming the shells of stars just as ripples on a pond spread when the surface is disturbed.
With deep imaging were also detected a stream extending from the core of NGC 3923 and a small elliptical galaxy on its axis, which is a probable progenitor of some the shells. Another stream lies south of the core of NGC 3923, and a hook like structure lies at the northwest.
Based on the velocity dispersion of the globular clusters of NGC 3923 the mass of the supermassive black hole of the galaxy was estimated to be
Supernovae.
One supernova has been detected in NGC 3923, SN 2018aoz, a type Ia supernova with peak magnitude 12.7. It was discovered on April 2, 2018.
Nearby galaxies.
NGC 3923 is the brightest galaxy in a galaxy group known as the NGC 3923 galaxy group. Within 25 arcminutes from NGC 3923 have been detected seven dwarf elliptical galaxies. NGC 3904 is located 37 arcminutes away. Other galaxies in the group include NGC 3885, ESO 440-27, and ESO440-011. Other nearby galaxies include NGC 3617, NGC 3673, NGC 3717, NGC 3936, and NGC 4105.


Nu Draconis

Nu Draconis (also known as ν Dra, ν Draconis, or traditionally as Kuma ) is a double star in the constellation Draco. The respective components are designated ν1 Draconis and ν2 Draconis. The second component is a spectroscopic binary star system.
This star, along with β Dra (Rastaban), γ Dra (Eltanin), μ Dra (Erakis) and ξ Dra (Grumium) were Al ʽAwāïd, "the Mother Camels", which was later known as the Quinque Dromedarii.
In Chinese, (), meaning "Celestial Flail", refers to an asterism consisting of ν Draconis, ξ Draconis, β Draconis, γ Draconis and ι Herculis. Consequently, the Chinese name for ν Draconis itself is (, .)
The two stars of the visual binary are considered to be a common proper motion pair on the basis of their very similar parallaxes, radial velocities, and proper motions, although no orbital motion can be observed.
ν1 Draconis is an Am star, a slowly-rotating chemically peculiar star with abnormally strong metallic absorption lines in its spectrum. Its spectral type of kA3hF0mF0 means that it would have a spectral class of A3 if determined solely from its calcium K lines, F0 if determined from its hydrogen lines, and F0 if determined from other metallic spectral lines.
ν2 Draconis is a spectroscopic binary with a period of 38 days. The two stars are separated by 0.267 au on average, and they have an almost circular orbit with an eccentricity of 0.03. The primary is also an Am star, while the secondary has a low mass and luminosity and is only inferred from the orbital movement of the more massive star.


HD 200375

HD 200375 is a binary star system in the equatorial constellation of Aquarius. Their orbit does not yet have a unique solution available.


Kepler-88

Kepler-88 is a Sun-like star in the constellation of Lyra, with three confirmed planets. In April 2012, scientists discovered that a Kepler candidate known as KOI-142.01 (Kepler-88b) exhibited very significant transit-timing variations caused by a non-transiting planet. Timing variations were large enough to cause changes to transit durations to Kepler-88b as well. Large transit-timing variations helped to put tight constraints to masses of both planets. The non-transiting planet was further confirmed through the radial velocity method in November 2013.
Planetary system.
Kepler-88 b is the inner most planet in the system and is Neptune-sized but almost half as dense.
Kepler 88 c is about 60% as massive as Jupiter but its radius is not known due to not transiting the planet.
Kepler-88 d orbits its star every four years, and its orbit is not circular, but elliptical. At three times the mass of Jupiter, it is the most massive. It was discovered based on six years of radial velocity (RV) follow-up from the W. M. Keck Observatory High Resolution Echelle Spectrometer spectrograph.


Xi Telescopii

Xi Telescopii, Latinized from ξ Telescopii, is a solitary star in the southern constellation of Telescopium. It is visible to the naked eye, with an apparent visual magnitude of +4.95. Based upon an annual parallax shift of 3.02 mas as measured from Earth, it is located approximately 1,100 light years from the Sun.
This is an evolved star with a stellar classification of K5 III or M1 IIab, indicating it is a giant or bright giant star. This is a variable star tentatively classified as a slow irregular type variable with a brightness that varies between magnitude +4.89 and +4.94. With around 56 times the Sun's radius, it shines with a luminosity approximately 2,973 times that of the Sun and has a surface temperature of 4,030 K.


Beta Circini

Beta Circini, Latinized from β Circini, is an A-type main sequence star and is the second-brightest star in the constellation of Circinus. It has an apparent visual magnitude of approximately 4.069, which is bright enough to be viewed with the naked eye. Based upon an annual parallax shift of 35.17 mas as seen from the Earth, it is located about 93 light years from the Sun.
With a stellar classification of A3 Va, this is an A-type main-sequence star. It is between 370 and 500 million years old with around 1.3 times the Sun's radius. The star is radiating 19 times the Sun's luminosity from its photosphere at an effective temperature of 8,676 K. It has one known sub-stellar companion.
Planetary System.
Beta Circini b is a distant brown dwarf companion orbiting the host star at a distance of 6,656 AU. It has a surface temperature of 2,084.0 K. Its mass was estimated using the Spectrum method which concluded that the object has a mass of .


Omega Ursae Majoris

Omega Ursae Majoris (Omega UMa, ω Ursae Majoris, ω UMa) is the Bayer designation for a binary star system in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of 4.61. Based upon an annual parallax shift of 13.24 mas, it is roughly 246 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.11 due to interstellar dust.
This is a single-lined spectroscopic binary star system with an orbital period of 15.8 days and an eccentricity of 0.31. The primary member, component A, is an A-type main sequence star with a stellar classification of A1VsSi:. The stellar spectrum has the appearance of a hot Am star, showing overabundances of many iron-peak and heavier elements, but an underabundance of helium. In particular, it has an abnormal abundance of silicon.
Naming.
In Chinese, (), meaning "Celestial Prison", refers to an asterism consisting of ω Ursae Majoris, 57 Ursae Majoris, 47 Ursae Majoris, 58 Ursae Majoris, 49 Ursae Majoris and 56 Ursae Majoris. Consequently, the Chinese name for ω Ursae Majoris itself is (, .).


List of stars in Vela

This is the list of notable stars in the constellation Vela, sorted by decreasing brightness.
This constellation's Bayer designations (Greek-letter star names) were given while it was still considered part of the constellation of Argo Navis. After Argo Navis was broken up into Carina, Vela, and Puppis, these Greek-letter designations were kept, so that Vela does not have a full complement of Greek-letter designations. For example, since Argo Navis's alpha star went to Carina, there is no Alpha Velorum.


Arp 256

Arp 256 is a pair of interacting spiral galaxies located in the constellation of Cetus. Arp 256 (also Arp 256S) refers to the southern galaxy; the northern galaxy is Arp 256N.


BL Telescopii

BL Telescopii is a multiple star in the constellation Telescopium. An Algol-like eclipsing binary, the star system varies between apparent magnitudes 7.09 and 9.08 in just over 778 days (2 years 48 days), which is generally too faint to be seen with the unaided eye. This is mainly due to the system being an eclipsing binary (that is, one star passing in front of the other star and resulting in a change in brightness). The eclipse itself dims the star by two magnitudes and lasts around 104 days.
Dutch astronomer Willem Jacob Luyten noted this star to be variable in 1935. Minima were retrospectively identified in old photographic plates from 1913 and 1919, and then observed by Howarth in 1936. Initially thought to be an R Coronae Borealis variable, its true nature as an eclipsing binary became clear in the 1940s.
The primary component is a yellow supergiant, whose spectral type has been calculated as either F5Iab/b or F4Ib. It is intrinsically variable, varying in brightness by 0.02 magnitude. It has pulsations of two periods, 92.5 days and 64.8 days in length. It has been classified as a UU Herculis variable—a class of yellow supergiant with semiregular variability. These stars are thought to have affinities with Cepheid variables and lie near the instability strip on the Hertzsprung–Russell diagram. The secondary was identified as an M-type star from TiO (titanium oxide) absorption bands visible during the eclipses.
The BL Telescopii system lies outside the galactic plane and has a high space velocity; it is a runaway star.


NGC 453

NGC 453 is a triple star located in the constellation Pisces. It was discovered in 1881 by Édouard Stephan.


List of stars in Draco

This is the list of notable stars in the constellation Draco.


NGC 437

NGC 437 is a lenticular galaxy of type S0/a located in the constellation Pisces. It was discovered on October 22, 1886 by Lewis Swift. It was described by Dreyer as "pretty faint, very small, round, faint star to northwest."


Lambda Eridani

Lambda Eridani (λ Eri) is a star in the constellation Eridanus. It is visible to the naked eye on a dark night with an apparent visual magnitude of 4.25. The distance to this star, based upon an annual parallax shift of 0.00402 arcseconds, is roughly 810 light years.
λ Eri is classified in the General Catalogue of Variable Stars as a Beta Cephei variable. The AAVSO International Variable Star Index defines a LERI type of variation. λ Eri is classified as LERI + GCAS since it shows both short term periodic variations and longer timescale eruptive variation. It was one of the first stars where short-period variations were found. The line profile variability periods are 0.702d and 0.269d, with intermittently present periods of 0.6d and 0.75d. The photometric amplitude of the variation is 0.010 magnitude.
This is a giant or subgiant Be star with a stellar classification of B2 IVne or B2 III(e)p, depending on the source. It is spinning rapidly with a projected rotational velocity of 327 km/s. Compare this to the estimated break-up velocity of 440 km/s. This rotation is giving the star an oblate shape with an equatorial bulge that is 25% larger than the polar radius. The most likely rotation period is deemed to be twice the period of variation, or 1.4 days. The star also possesses a rotating circumstellar disc, seen edge on, which makes Lambda Eri a "shell star", where the disk appears more opaque than usual.
Like most Be stars, Lambda Eridani emits soft X-rays. In 1993, a giant X-ray flare was observed in which the X-ray luminosity increased by a factor of six over a 39-hour period. Lambda Eridani has about nine times the mass of the Sun, and 8.6 times the Sun's radius. It radiates 7,510 times the solar luminosity from its outer atmosphere at an effective temperature of 21,150 K.


65 Ursae Majoris

65 Ursae Majoris, abbreviated as 65 UMa, is a star system in the constellation of Ursa Major. With an apparent magnitude of about 6.5, it is at the limit of human eyesight and is just barely visible to the naked eye. Trigonometric parallax measurements made by the Hipparcos spacecraft put it at a distance of about 690 light years (210 parsecs); this is in close agreement with the dynamical parallax value of .
65 Ursae Majoris is a sextuple star system. It contains six stars in a hierarchical orbit where each star orbits the central system. Such systems are fairly uncommon, with only a few sextuple stars known. Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay into smaller systems.
Multiplicity.
Hierarchy of orbits in the 65 Ursae Majoris system
The central pair of stars are both A-type main-sequence stars. These are relatively bright, white-colored stars that typically have masses from to . 65 Ursae Majoris Aa1 and Aa2 both have relatively low masses for an A-type main sequence star and have spectral types of A7V. Both components periodically pass in front of each other while orbiting, so they form an eclipsing binary with the variable star designation DN Ursae Majoris. Therefore, the apparent magnitude of the system varies between 6.6 and 6.7 magnitudes. Its orbital period of 1.73 days.
The eclipsing binary pair 65 Ursae Majoris Aa is orbited by another star, designated 65 Ursae Majoris Ab. It is a spectroscopic binary: while the pair cannot be resolved, periodic Doppler shifts in their spectra indicate that there must be orbital motion. 65 Ursae Majoris orbits the inner pair with a period of 641 days (1.76 years) and an eccentricity of 0.169.
65 Ursae Majoris B orbits the three every 118 years. It is separated from the triple by 0.18″, and an astrometric orbit has been calculated. 65 Ursae Majoris C and D are common proper motion companions and are separated 4″ and 63″ away from the central system, respectively. 65 Ursae Majoris D also appears to be a chemically peculiar star with higher amounts of chromium, strontium, and europium than normal. Because of its unusual composition, determination of its stellar parameters is difficult; the effective temperature of this star may be 9300 or 9500 K, with the radius and the surface gravity of the star depending on the effective temperature.
<br>


Lambda Fornacis

The Bayer designation Lambda Fornacis (λ For / λ Fornacis) is shared by two faint naked-eye stars about a degree apart, in the constellation Fornax:


HOPS 383

HOPS 383 is a Class 0 protostar. It is the first class-0 protostar discovered to have had an outburst, and as of 2020, the youngest protostar known to have had an outburst. The protostar was discovered by the Herschel Orion Protostar Survey (HOPS) team.


Lambda Sculptoris

The Bayer designation Lambda Sculptoris (λ Scl, λ Sculptoris) is shared by two star systems, λ¹ Sculptoris and λ² Sculptoris, in the constellation Sculptor. They are separated by 0.29° on the sky.


NGC 370

NGC 370 is a triple star located in the constellation Pisces. It was recorded on October 7, 1861 by Heinrich d'Arrest. It was described by Dreyer as "very faint, 13th magnitude star 15 arcsec to south, diffuse." However, there is nothing there. It is now presumed to be either a lost or "non-existent" object, although it is possible it could be a duplication of NGC 372.


Theta Orionis

The Bayer designation θ Orionis (Theta Orionis) is shared by several astronomical objects, located near RA DEC :
The various components are spread over several arc-minutes in and near the Orion Nebula.


Antlia Dwarf

The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc (4.3 million light-years) from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia-Sextans Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy NGC 3109.
Discovery.
Antlia Dwarf was first cataloged in 1985 by H. Corwin, Gérard de Vaucouleurs, and A. de Vaucouleurs. Later in 1985 and 1987 it was noted as a possible nearby dwarf galaxy by two groups of astronomers. It was finally confirmed as a dwarf galaxy in 1997 by Alan Whiting, Mike Irwin and George Hau during a survey of the northern sky. They for the first time resolved it into stars and determined the distance to it—1.15 Mpc (the modern distance estimate is slightly larger). The same year, Antonio Aparicio, Julianne Dalcanton, Carme Gallart and David Martinez-Delgado studied for the first time its stellar content and measured its mass, luminosity and metallicity.
In 1999 Antlia Dwarf was identified by Sidney van den Bergh as the fourth member of the Antlia Group—the group of galaxies closest to the Local Group.
Properties.
The Antlia Dwarf is classified alternatively as a dwarf elliptical galaxy of type dE3.5, or either as a dwarf spheroidal galaxy (dSph) or as a transitional galaxy from spheroidal to irregular types (dSph/Irr). The last classification is due to a substantial star formation in this galaxy in the last 0.1 billion years.
Antlia Dwarf comprises two components: a core and an old halo. Its half-light radius is about 0.25 kpc. The metallicity is very low, at about <[Fe/H]>=−1.6 to −1.9 meaning that Antlia Dwarf contains 40–80 times less heavy elements than the Sun. The galaxy has a well-defined and easily observed red giant branch, which makes measuring its distance relatively easy. The total luminosity of Antlia Dwarf is approximately 1 million times that of the Sun (the visible absolute magnitude is MV=−10.3).
The stellar mass of Antlia Dwarf is estimated to be about 2–4×106 solar masses, while its total mass (within the visible radius) is approximately 4 solar masses. The galaxy contains stars of all ages but is dominated by old stars with the age of more than 10 billion year. There seems to have been a major episode of star formation in the Antlia Dwarf around 100 million years ago. However, the young stars are confined to the central core of the galaxy.
Antlia Dwarf is unusual among dwarf spheroidal galaxies in that it contains large amounts (as much as 7 ×105 solar masses) of neutral atomic hydrogen. However it does not have significant H II regions and does not actively form stars at the present moment.
Location and interactions.
The Antlia Dwarf is located about away, in the constellation Antlia. Its distance from the barycenter of the Local Group is about 1.7 Mpc. At this distance, it is situated well outside the Local Group and is a member of a separate group of dwarf galaxies called Antlia-Sextans Group. The Antlia Dwarf is separated from the small spiral/irregular galaxy NGC 3109 by only 1.18 degrees on the sky, which corresponds to a physical separation of to depending on their radial separation.
The Antlia Dwarf and NGC 3109 may be actually physically bound if the distance between them is not very large. However their velocity relative to each other—43 km/s makes it questionable whether they are in fact a bound system, especially if the distance between them is closer to the upper limit—180 kpc. If they are gravitationally bound, their total mass may be as high as 78 billion solar masses.
Observations have also demonstrated that NGC 3109 has a warp in its gaseous disk that is traveling at the same velocity as the gas in the Antlia Dwarf, indicating that the two galaxies had a close encounter about one billion years ago.


Omicron Orionis

Omicron Orionis refers to 2 distinct star systems in the constellation Orion:
All of them were member of asterism 參旗 (Sān Qí), "Banner of Three Stars", "Net" mansion.
See also.
o Orionis (22 Orionis)


NGC 6939

NGC 6939 is an open cluster in the constellation Cepheus. It was discovered by William Herschel in 1798. The cluster lies 2/3° northwest from the spiral galaxy NGC 6946. The cluster lies approximately 4.000 light years away and it is over a billion years old.
Observation.
NGC 6939 is located near the border of the constellations Cepheus and Cygnus, at the southwest corner of Cepheus. The open cluster is located two degrees southwest of Eta Cephei and 2/3° northwest from the spiral galaxy NGC 6946, which has visual magnitude 8.8. They appear as two patches of haze with 10x50 binoculars. NGC 6939 can be glimpsed with 7x35 binoculars where as 25x200 binoculars are required to start resolve the cluster. The cluster can be glimpsed with 4 inches telescope and is resolved at x72 magnification. NGC 6939 is included in the Herschel 400 Catalogue.
Characteristics.
NGC 6939 is an old open cluster, located 400 parsec above the galactic plane and 8.400 parsec away from the galactic centre. With the use of photometric studies, the age of the cluster was estimated to be between 1,0 and 1,3 billion years, using as sample 638 stars within the field. The metallicity of the cluster is slightly subsolar (-0.19±0.09).
Some of its members are variable stars: a study in 1998 led to the discovery of six variable stars among the red giants of the cluster, with two of which are Algol type and V466 Cephei appears to be a W Ursae Majoris type. A further study in 2004 identified further 10 variables near the cluster, five of which were W Ursae Majoris type and one RR Lyrae.


Omega Persei

Omega Persei (ω Persei) is a solitary, orange-hued star in the northern constellation of Perseus. It has the traditional name Gorgonea Quarta , being the fourth member of the quartet called the Gorgonea in reference to the Gorgons from the legend of Perseus. The star is faintly visible to the naked eye with an apparent visual magnitude of +4.6. Based upon an annual parallax shift of 11.32 mas as seen from the Earth, the star is about 288 light years from the Sun.
This is an evolved K-type giant star with a stellar classification of K0 III. It is a red clump star that is generating energy via helium fusion at its core. At the estimated age of 1.65 billion years, Omega Persei has double times the mass of the Sun and has expanded to about 19 times the Sun's radius. It is radiating 144.5 times the Sun's luminosity from its photosphere at an effective temperature of 4,586 K.


Kepler-25c

Kepler-25c is an exoplanet orbiting the star Kepler-25, located in the constellation Lyra. The planet was first detected as a candidate extrasolar planet by the Kepler space telescope in 2011. It was confirmed, in 2012, by Jason Steffen and collaborators using transit-timing variations obtained by the Kepler Space Telescope. It orbits its parent star at only 0.110 astronomical units away, and at its distance it completes an orbit once every 12.7 days.


Delta2 Lyrae

Delta2 Lyrae (δ2 Lyr) is a 4th magnitude star in the constellation Lyra, approximately 900 light years away from Earth. It is one of the M4II spectral standard stars, meaning it is a bright giant star with a surface temperature around 3,600 kelvins. It puts out more energy than 10,000 suns, although more than 90% of it at longer than visual wavelengths. Direct angular measurements, combined with the Hipparcos parallax, give a radius of 1.1
- 1.3
astronomical units, comparable to the size calculated from other observed data.
It began life as a hot blue main sequence star, but now is a large cool asymptotic giant branch star with a degenerate carbon-oxygen core. It is a semi-regular variable star that has its brightness change by 0.2 magnitudes over an ill-defined period. Delta2 Lyrae was once thought to form a visual binary with the star Delta1 Lyrae, but it does not, only appearing to do so if seen from earth's direction.
δ2 Lyrae is a variable star, probably a semiregular variable. It has a magnitude range of 4.22 to 4.33. It is the brightest member of the scattered open cluster Stephenson 1, also known as the δ Lyrae Cluster. Other known members include δ1 Lyrae, a handful of 8th-9th magnitudes stars, and at least thirty other stars down to 14th magnitude.
Multiple star catalogues list several companions to δ2 Lyrae, with designations such as ADS 11825. Two of them are a close pair of 10th magnitude stars about 87" from δ2, designated components B and C. The spectral type of the pair suggests that they are at the same distance as Delta2 Lyrae, which could mean that the three stars form a triple star system. In this case, the ADS 11825BC pair would be 24,000 AU away from δ2 Lyrae, and it would take 24,000 years for it to make an orbit. The two stars in the BC system take at least 10,500 years to make an orbit and are separated by 600AU.


62 Sagittarii

62 Sagittarii is a single, variable star in the constellation of Sagittarius. It has the Bayer designation c Sagittarii and the variable star designation V3872 Sagittarii, while "62 Sagittarii" is its Flamsteed designation. This object forms the southwest corner of the asterism called the Terebellum. It is visible to the naked eye with an apparent visual magnitude that varies between 4.45 and 4.64, and, at its peak, it is the brightest of the four stars in the Terebellum. 62 Sagittarii is the star in the Terebellum which is most distant from its centre; it is 1.72° from its northwest corner, 60 Sagittarii, and 1.37° from its southeast corner, 59 Sagittarii. This star is located approximately 450 light-years from the Sun based on parallax, and is drifting further away with a radial velocity of +10 km/s.
This is an aging red giant with a stellar classification of M4.5III, a star that has exhausted the supply of hydrogen at its core and expanded to around 72 times the Sun's radius. It is a slow irregular variable with multiple pulsation periods. The star is radiating about 1,100 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,915 K.


Delta Capricorni

Delta Capricorni (δ Capricorni, abbreviated Del Cap or δ Cap) is a multiple star system about 39 light-years away in the constellation of Capricornus (the Sea Goat). The primary star in the system is a white giant and the combined light of its members makes it the brightest star in the constellation.
The system consists of an eclipsing binary, Delta Capricorni A, and two companion stars, B and C. A's two components are themselves designated Delta Capricorni Aa (formally named Deneb Algedi , the traditional name of the system) and Ab.
Delta Capricorni is 2.6 degrees south of the ecliptic and can be occulted by the Moon, and (rarely) by planets.
Nomenclature.
"δ Capricorni" (Latinised to "Delta Capricorni") is the system's Bayer designation. The designations of the three constituents as "Delta Capricorni A", "B" and "C", and those of "A's" components – "Delta Capricorni Aa" and "Ab" – derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
The system bore the traditional names "Deneb Algedi", derived from the Arabic ذنب الجدي ("ðanab al-jady"), meaning "the tail of the goat", referring to the fishlike tail of the celestial sea-goat Capricorn, and "Scheddi". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Deneb Algedi" for the component Delta Capricornii Aa on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese astronomy, Delta Capricorni is known as (), meaning 'The Fourth Star of the Line of Ramparts'. This refers to its presence among an asterism known as 'The Line of Ramparts', which also includes Kappa Capricorni, Epsilon Capricorni, Gamma Capricorni, Iota Aquarii, Lambda Aquarii, Sigma Aquarii, Phi Aquarii, 27 Piscium, 29 Piscium, 33 Piscium and 30 Piscium.
Observational history.
In 1906 astronomer Vesto Slipher of Lowell Observatory discovered that Delta Capricorni A was a spectroscopic binary. The orbit was determined in 1921 by Clifford Crump using 69 radial velocity measurements obtained at Yerkes Observatory. However the eclipsing binary nature of the system was not discovered until 1956 by Olin J. Eggen at Lick Observatory.
Lunar occultations have been observed in 1951, 1962, and 1988.
Delta Capricorni was recognised as a metallic-line star in 1957 and included in a 1958 catalog of magnetic stars. It has also been associated with extreme ultraviolet and radio sources, believed to be from coronal activity in the secondary star.
Stellar system.
Delta Capricorni A is an Algol-type eclipsing binary star, with an orbital period of 1.022768 days and an inclination close to the line of sight from the Earth. The peak apparent visual magnitude of the pair is 2.81. During an eclipse of the primary, this magnitude drops by 0.24. When the primary is eclipsing the secondary, the magnitude decreases by 0.09.
Delta Capricorni A has an overall stellar classification of A7m III, indicating that it is a giant star that has exhausted the supply of hydrogen at its core. More specifically, this is a chemically-peculiar Am star with a spectral type of kA5hF0mF2 III under the revised MK system. This notation indicates that the calcium K-line matches the temperature of an A5 star, the hydrogen spectral type matches an F0 star, and the metallic absorption lines match an F2 star.
In the past this star was suspected of being a Delta Scuti variable, which is rare for an Am star. This categorization was brought into question during observations in 1994 and it is most likely not inherently variable. The primary has double the Sun's mass and nearly twice its radius. It is rotating rapidly with a projected rotational velocity of 105 km s−1. (This rotation rate is synchronous with the orbital period.) Note that it is unusual for an Am star to have such a high rotational velocity. The outer envelope of the star is radiating energy at an effective temperature of 7,301 K, giving it the white-hued glow of an A-type star. The secondary component is a G-type or K-type star with around 90% of the mass of the Sun.
There are two optical companions. A fifteenth magnitude star is one arcminute away, and a thirteenth magnitude star is over two arcminutes away from the primary star and that distance is increasing.
In culture.
According to astrology, Delta Capricorni's representation of a flexible tail is reflected in its association with both good and bad fortune alike. It was one of the fifteen Behenian stars of medieval astrology, associated with chalcedony, marjoram and the kabbalistic symbol .


NGC 6480

NGC 6480 is an open cluster in the constellation Scorpius. The object was discovered on 8 June 1836 by the British astronomer John Herschel.


NGC 3705

NGC 3705 is a barred spiral galaxy in the constellation Leo. It was discovered by William Herschel on Jan 18, 1784.


Epsilon Centauri

Epsilon Centauri (ε Cen, ε Centauri) is a star in the southern constellation of Centaurus. It is one of the brightest stars in the constellation with a slightly variable apparent visual magnitude of +2.30. Parallax measurements put it at a distance of around from Earth.
In Chinese, (), meaning "Southern Gate", refers to an asterism consisting of ε Centauri and α Centauri. Consequently, the Chinese name for ε Centauri itself is (, .)
ε Centauri is a massive star with nearly 12 times the mass of the Sun. The spectrum matches a stellar classification of B1 III, indicating this is an evolved giant star. It is radiating more than 15,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 24,000 K, giving it the blue-white hue of a B-type star. This is classified as a Beta Cephei type variable star with a primary period of 0.16961 days (4 hours 4 minutes), completing 5.9 cycles per day. During each cycle, the brightness of the star varies from apparent magnitude +2.29 to +2.31.
This star is a proper motion member of the Lower-Centaurus Crux sub-group in the Scorpius-Centaurus OB association, the nearest such association of co-moving massive stars to the Sun. Epsilon Centauri is a relatively young star, with an age of around 16 million years.


OGLE2-TR-L9

OGLE2-TR-L9 is a magnitude 15 star in the constellation Carina at a distance of approximately 5,142 light years.
Planetary system.
This star is home to the transiting extrasolar planet OGLE2-TR-L9b discovered in 2008.


WR 9

WR 9 is a spectroscopic binary in the constellation Puppis consisting of a Wolf-Rayet star and a class O star. It is around 4,800 light years away.
WR 9 is a binary with two components in a circular 14-day orbit. The Wolf-Rayet component is often identified as the primary because it dominates the spectrum with its broad emission lines, although it is less massive, less luminous, and less visually bright than its companion. The companion is an approximately O7 star.
The spectrum is dominated by broad emission lines, those of CIV being the strongest, followed by HeII. CIII lines are seen but much weaker. OV lines are also stronger than CIII. The classification is usually given as WC4, although it has previously been assigned as WC5. By comparison, the absorption lines of the secondary star are narrower and weaker, although at blue and shorter wavelengths they become stronger than the WR lines. The spectral type of the secondary can be set at O7. The luminosity class cannot be determined clearly, although it has been suggested to be a supergiant. The Wolf-Rayet star shows no hydrogen in its spectrum and is thought to be hydrogen-free. It is calculated to consist of 42% helium and 58% heavier elements, mostly carbon and oxygen.
WR 9 is listed as an eclipsing binary in the General Catalogue of Variable Stars, as well as having the more irregular brightness changes frequently seen in Wolf Rayet stars. The total amplitude is only 0.04 magnitudes. The eclipses are so shallow because only the atmosphere of the WR star eclipses the O star on each orbit.


NGC 245

NGC 245 is a spiral galaxy located in the constellation Cetus. It was discovered on October 1, 1785 by William Herschel.


HD 33463

HD 33463 is a suspected variable star in the northern constellation of Auriga. This is a red giant star with a stellar classification of M2III.


Sigma2 Cancri

Sigma2 Cancri, Latinized from σ2 Cancri, is the Bayer designation for a solitary, white-hued star in the constellation Cancer. It is faintly visible to the naked eye, with an apparent visual magnitude of +5.44. Based upon an annual parallax shift of 16.79 mas as seen from Earth, this star is located around 194 light years from the Sun.
With an estimated age of 441 million years, this is an A-type subgiant star with a stellar classification of A7 IV. It is spinning relatively rapidly with a projected rotational velocity of 133 K. The star has an estimated 1.8 times the mass of the Sun and is radiating 21.5 times the Sun's luminosity from its photosphere at an effective temperature of roughly 8,309 K.


NGC 824

NGC 824 is a barred spiral galaxy located in the constellation Fornax about 260 million light-years from the Milky Way. It was discovered by British astronomer John Herschel in 1837.


Iota Piscis Austrini

Iota Piscis Austrini (ι Piscis Austrini) is a solitary, blue-white hued star in the southern constellation of Piscis Austrinus. It has an apparent visual magnitude of +4.35 and is around 500 light years from the Sun. This is an A-type main sequence star with a stellar classification of A0 V. It has a magnitude 11.4 visual companion located at an angular separation of 20 arc seconds along a position angle of 290°, as of 1910.
Iota Piscis Austrini is moving through the Galaxy at a speed of 29.7 km/s relative to the Sun. Its projected Galactic orbit carries it between 18,400 and 24,300 light years from the center of the Galaxy.
Naming.
In Chinese, (), meaning "Celestial Money", refers to an asterism consisting of refers to an asterism consisting of ι Piscis Austrini 13 Piscis Austrini, θ Piscis Austrini, μ Piscis Austrini and τ Piscis Austrini. Consequently, the Chinese name for ι Piscis Austrini itself is (, .)


Kepler-46

 = {\left ( \frac{R}{R_{\odot}} \right )}^2 {\left ( \frac{T}{T_{\odot}} \right )}^4</math>.</ref>
Kepler-46, previously designated KOI-872, is a star located in the constellation Lyra. Observed since 2009 by the Kepler space observatory, it has since been found to possess a planetary system consisting of at least two planets and while it has a similar mass to the Sun (90%) it is significantly older at ten billion years.
Kepler-46 b (previously KOI-872.01), was the first planet discovered in the system. It was found through detailed analysis of Kepler space observatory data. An additional planet, Kepler-46 c, was discovered by an outside group using Kepler public data through analysis of transit timing variations. While only one additional planet was confirmed by the analysis, the study revealed the potential existence of an unconfirmed planet KOI-872.03 (KOI-872 d). Validation by the multiplicity method confirmed the existence of this planet which was then renamed Kepler-46d.
Planetary system.
Planet b is a gas giant planet with a mass slightly less than that of Jupiter. The second planet in the system was among the first to be discovered through the method of transit timing variations, and through its confirmation of KOI-872 c with a 99% confidence level has shown that the method of detection may be used to detect future extrasolar planets and, possibly, extrasolar moons. This second planet exerted a gravitational force on the first planet, orbiting its host star in just 34 days. While this usually occurs on an extremely regular schedule, additional planets within the system can disrupt the time of the transit, and these disruptions can indicate the presence of a planet, even if the disrupting planet does not pass in front of the host star itself.
The data show that Kepler-46 c is an approximately Saturn-mass object with an orbital period of 57 days. As the planet does not itself transit its host star, there is no way of knowing its size (probably a similar size to its sibling). The measurements also suggest the existence of another planet orbiting with a period of about 6.8 days, and this planet was confirmed in 2016.
The method in which the planet was detected is similar to the way that the planet Neptune was discovered, in which the newly discovered planet is detected by its pull on another which is already known to exist.
In 2021, it was found the orbital plane of Kepler-46b is slowly changing, likely under the gravitational influence of the additional giant planet.


Iota Horologii b

Iota Horologii b (ι Hor b / ι Horologii b), often catalogued HR 810 b, is an extrasolar planet approximately 56.5 light-years away in the constellation of Horologium (the Pendulum Clock). Iota Horologii b has a minimum mass 1.94 times that of Jupiter; however, preliminary astrometric measurements suggest that the object may be around 24 Jupiter masses and would therefore be a brown dwarf.
Detection and discovery.
The discovery of Iota Horologii b was the result of a long-term survey of forty Solar analog stars that was begun in November 1992. The planet represents the first discovery of an extrasolar planet with a European Southern Observatory instrument, with the data found at the La Silla Observatory in Chile.
The Keplerian signal found the planet to have an orbital period of 320.1 days, indicative of an orbiting planet with minimum mass of 2.26 Jupiter masses. Iota Horologii b was announced in the summer of 1999 as the first planet found by a team of planet hunters led by Martin Kürster.
The measurements of Iota Horologii show that the planet orbits the star approximately every 320 days. From this period, the known mass of the central star (1.25 solar masses) and the amplitude of the velocity changes, a mass of at least 2.26 times that of planet Jupiter is deduced for the planet.
It revolves around the host star in a somewhat elongated orbit. If it were located in the Solar System, this orbit would stretch from just outside the orbit of Venus (at 117 million km or 0.78 astronomical units [AU] from the Sun) to just outside the orbit of the Earth (at 162 million km or 1.08 AU). Because the planet is at least 720 times more massive than the Earth, it is predicted that Iota Horologii b is more similar to planet Jupiter.
In recent astrometric analysis of Iota Horologii b suggests that planet b may have as much as 24 times the mass of Jupiter with an inclination of 5.5 degrees from Earth's line of sight. With this calculations, Iota Horologii b may actually be an extremely dim brown dwarf and a substellar companion of Iota Horologii. However, these measurements were later proved useful only for upper limits of inclination.


Kepler-296b

Kepler-296 b is an s-type exoplanet located in the binary star system Kepler-296. All 5 planets in this system orbit a single star, but it is unknown which star this is
It has been classed as a hot superterran.
It was discovered by the Kepler space telescope in 2014 using the transit method and was originally classed as a planet candidate, but during a study by members of the NASA Ames Research Center on two other planets in the Kepler-296 system, Kepler-296f and Kepler-296e, they were able to confirm that Kepler-296 b is an exoplanet with "more than 99% confidence".
Data.
As with most other exoplanets, not many parameters are known about Kepler-296b. The few that are, are listed in the infobox to the right.


Psi3 Aurigae

Psi3 Aurigae, Latinized from ψ3 Aurigae, is a single, blue-white hued star in the northern constellation of Auriga. It is dimly visible to the naked eye with an apparent visual magnitude of +5.20. Based upon an annual parallax shift of as seen from the Earth, it is approximately distant from the Sun.
This is a B-type giant star with a stellar classification of B8 III. It has about 4.2 and is spinning with a relatively high projected rotational velocity of 118 km/s. The star is radiating 1,624 times the Sun's luminosity from its photosphere at an effective temperature of 13,361 K.


HD 64440

HD 64440, also known as a Puppis, is a spectroscopic binary star in the constellation Puppis. Its apparent magnitude is 3.71. Located around distant, the primary is a bright giant of spectral type K1.5II and the secondary is an early A-type star. They orbit with a period just under 7 years and eccentricity 0.38.


List of stars in Triangulum

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


List of stars in Puppis

This is the list of notable stars in the constellation Puppis, sorted by decreasing brightness.
This constellation's Bayer designations (Greek-letter star names) were given while it was still considered part of the constellation of Argo Navis. After Argo Navis was broken up into Carina, Vela, and Puppis, these Greek-letter designations were kept, so that Puppis does not have a full complement of Greek-letter designations. For example, since Argo Navis's alpha star went to Carina, there is no Alpha Puppis.


Theta Serpentis

Theta Serpentis (θ Serpentis, abbreviated Theta Ser, θ Ser) is a triple star system in the constellation of Serpens.
It consists of a binary pair designated Theta Serpentis AB and whose two components are designated Theta¹ Serpentis or Theta Serpentis A (officially named Alya , the traditional name for the entire system) and Theta² Serpentis or Theta Serpentis B, together with a third visual companion Theta Serpentis C.
Based upon parallax measurements obtained during the Hipparcos mission, θ Serpentis AB is approximately 160 light-years, and θ Serpentis C approximately 86 light-years, from the Sun.
Nomenclature.
"θ Serpentis" (Latinised to "Theta Serpentis") is the system's Bayer designation; "θ¹" and "θ² Serpentis" those of the brightest two components. The designations of the two constituents as "Theta Serpentis AB" and "C", and those of "AB's" components - "Theta Serpentis A" and "B" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
The system bore the traditional name "Alya", or "Alga", from the Arabic الية "’alyah" "fat tail (of a sheep)". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Alya" for the component Theta Serpentis A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In the catalogue of stars in the "Calendarium" of Al Achsasi al Mouakket, this star was designated "Dzaneb al Haiyet", which was translated into Latin as "Cauda Serpentis", meaning 'the serpent's tail'.
In Chinese, (), meaning "Left Wall of Heavenly Market Enclosure", refers to an asterism which represents eleven old states in China, consisting of Theta Serpentis, Delta Herculis, Lambda Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Eta Serpentis, Nu Ophiuchi, Xi Serpentis and Eta Ophiuchi. Consequently, the Chinese name for Theta Serpentis itself is (, ), representing the state Xu (徐).
Properties.
Both Theta¹ Serpentis and Theta² Serpentis are white A-type main sequence dwarfs. θ¹ has an apparent magnitude of +4.62 while the slightly dimmer θ² has a magnitude of +4.98. These two stars are 22 arcseconds apart on the sky, putting them at least 900 AU apart with an orbital period of at least 14,000 years. Both stars are similar to each other in all respects, having luminosities of 18 and 13 times solar respectively, radii of about twice solar and also masses of roughly 2 times that of the Sun. Both stars have a surface temperature of 8,000 kelvins.
Theta Serpentis C is a yellow G-type star with an apparent magnitude of +6.71. It is separated by 7 arcminutes from θ².


NGC 4306

NGC 4306 is a dwarf barred lenticular galaxy located about 100 million light-years away in the constellation Virgo. The galaxy was discovered by astronomer Heinrich d'Arrest on April 16, 1865.
NGC 4306 is a companion of NGC 4305 and appears to be interacting with it.
Virgo Cluster membership.
Although considered to be a member of the Virgo Cluster, its high radial velocity and similar distance as NGC 4305 suggest that NGC 4306 is a background galaxy.


List of stars in Libra

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


74 Cygni

74 Cygni is a visual binary star system in the northern constellation Cygnus, located around 249 light years distant from the Sun. It is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 5.04. The pair orbit each other with a period of and an eccentricity of 0.5. The system is a source of X-ray emission, which is most likely coming from the secondary component.
The primary component is an A-type main-sequence star with a stellar classification of A3 Vn; a star that is fusing its core hydrogen. The 'n' suffix indicates "nebulous" absorption lines due to rapid rotation, with the star having a projected rotational velocity of 201 km/s. The high rate of spin is giving the star an oblate shape with an equatorial bulge that is 8% larger than the polar radius. The star has 1.68 times the mass of the Sun and is radiating 36 times the Sun's luminosity from its photosphere at an effective temperature of about 7,859 K.


List of stars in Lacerta

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


MWC 480

MWC 480 is a single star, about 500 light-years away in the constellation of Auriga. It is located in the Taurus-Auriga Star-Forming Region. The name refers to the Mount Wilson Catalog of B and A stars with bright hydrogen lines in their spectra. With an apparent magnitude of 7.62, it is too faint to be seen with the naked eye.
Properties.
MWC 480 is a young Herbig Ae/Be star, a class of young stars with spectral types of A or B, but are quite young and are still not main-sequence stars. MWC 480 is about 7 million years old. It is about twice the mass of the Sun, and is estimated to be about 1.67 solar radii.
MWC 480 has X-ray emissions typical of a pre-main-sequence Herbig Ae/Be star but with an order of magnitude more photoelectric absorption. It has a gas-dust envelope and is surrounded by a protoplanetary disc that is about 11% the mass of the Sun. The disc is inclined about 37° towards the line of sight, on a position angle of about 148°. Astronomers using the ALMA (Atacama Large Millimeter/submillimeter Array) have found that the protoplanetary disc surrounding MWC 480 contains large amounts of methyl cyanide (CH3CN), a complex carbon-based molecule. Hydrogen cyanide (HCN) has also been detected in the disc. No signs of planet formation have yet been detected.


NGC 940

NGC 940 is a lenticular galaxy in constellation triangulum. It is estimated to be 222 million light-years from the Milky Way and has a diameter of approximately 80,000 ly. NGC 940 was discovered by Heinrich d'Arrest.


HD 70642

HD 70642 is a yellow dwarf star in the constellation of Puppis located 96 light years away. This star has about the same mass and radius as the Sun, is slightly cooler and less luminous, and is richer in abundance of iron relative to hydrogen.
Planetary system.
A long period planet companion to HD 70642 was announced in 2003. This planet orbits in a circular orbit (e=0.034) at 3.232 AU. The star is so like Sol that its habitable zone is in the same place (~ 1 AU). The jovian ensures the stability of an Earth-mass planet at 1 AU. This system is one of the most similar in conditions to the Solar System than any other currently known planetary systems.


Lambda Geminorum

Lambda Geminorum, Latinized from λ Geminorum, is a candidate multiple star system in the constellation Gemini. It is visible to the naked eye at night with a combined apparent visual magnitude of 3.57. The distance to this system is 101 light years based on parallax, and it is drifting closer with a radial velocity of –7.4 km/s. It is a member of what is suspected to be a trailing tidal tail of the Hyades Stream.
Components A and B of this system form a wide binary. The secondary, component B, is a magnitude 10.7 stellar companion at an angular separation of from the primary along a position angle of 35.72°, as of 2009. The primary was identified as a spectroscopic binary by E. B. Frost in 1924. This companion was confirmed during a lunar occultation with a separation of and magnitude 6.8.
The primary, designated component A, typically has been assigned a stellar classification of A3V, which indicates this is an A-type main-sequence star that generates energy from core hydrogen fusion. However, in 1970 D. C. Barry classed it as A4IV, suggesting this may be a subgiant star that has begun evolving into a giant star. It was catalogued a suspected variable star, but is now confirmed as constant.
This star is less than a billion years in age with a rapid spin, showing a projected rotational velocity of 154 km/s It larger and hotter than the Sun, with twice the Sun's mass and 2.8 times the radius of the Sun. The star is radiating 27 times the Sun's luminosity from its photosphere at an effective temperature of 7,932 K.
The primary displays a significant infrared excess in the K-band, which indicates an orbiting circumstellar disk of dust. A model fit to the data shows an inner radius between and , and an outer radius of up to .


Shatabhisha

Shatabhisha, also known as Chathayam or Sadayam (Devanagari: शतभिषा, , ), or "Shatabhishak" or "Shatataraka" is the 24th "nakshatra" in Hindu astronomy. It corresponds to the star γ Aquarii. Varuna is the deity of this nakshatra. The ruling planet of this nakshatra is Rahu.


NGC 5682

NGC 5682 is a spiral galaxy located in Boötes. It had a supernovae called SN 2005CI. SN 2005CI is located at and (near the galaxy).


Rho Coronae Borealis

Rho Coronae Borealis (ρ CrB, ρ Coronae Borealis) is a yellow dwarf star approximately 57 light-years away in the constellation of Corona Borealis. The star is thought to be similar to the Sun with nearly the same mass, radius, and luminosity. It is orbited by two known exoplanets.
Stellar properties.
Rho Coronae Borealis is a yellow main sequence star of the spectral type G0V. The star is thought to have 91 percent of the Sun's mass, along with 1.4 times its radius and 1.7 times its luminosity. It may only be 51 to 65 percent as enriched with elements heavier than hydrogen (based on its abundance of iron) and may be somewhat older than the Sun at around ten billion years old.
Planetary system.
An extrasolar planet in a 39.8-day orbit around Rho Coronae Borealis was discovered in 1997 by observing the star's radial velocity variations. This detection method only gives a lower limit on the true mass of the companion. In 2001, preliminary "Hipparcos" astrometric satellite data indicated that the orbital inclination of the star's companion was 0.5°, nearly face-on, implying that its mass was as much as 115 times Jupiter's. A paper published in 2011 supported this claim using a new reduction of the astrometric data, with an updated mass value of 169.7 times Jupiter, with a 3σ confidence region 100.1 to 199.6 Jupiter masses. Such a massive body would be a dim red dwarf star, not a planet. In 2016, however, a paper was published that used interferometry to rule out any stellar companions to this star, in addition to detecting a second planetary companion in a 102-day orbit.
Searches for circumstellar material.
In October 1999, astronomers at the University of Arizona announced the existence of a circumstellar disk around the star. Follow-up observations with the Spitzer Space Telescope failed to detect any infrared excess at 24- or 70-micrometre wavelengths, which would be expected if a disk were present. No evidence for a disk was detected in observations with the Herschel Space Observatory either.


Rigel

Rigel, designated β Orionis (Latinized to Beta Orionis, abbreviated Beta Ori, β Ori), is a blue supergiant star in the constellation of Orion, approximately from Earth. Rigel is the brightest and most massive componentand the eponymof a star system of at least four stars that appear as a single blue-white point of light to the naked eye. A
star of spectral type B8Ia, Rigel is calculated to be anywhere from 61,500 to 363,000 times as luminous as the Sun, and 18 to 24 times as massive, depending on the method and assumptions used. Its radius is more than seventy times that of the Sun, and its surface temperature is . Due to its stellar wind, Rigel's mass-loss is estimated to be ten million times that of the Sun. With an estimated age of seven to nine million years, Rigel has exhausted its core hydrogen fuel, expanded, and cooled to become a supergiant. It is expected to end its life as a typeII supernova, leaving a neutron star or a black hole as a final remnant, depending on the initial mass of the star.
Rigel varies slightly in brightness, its apparent magnitude ranging from 0.05 to 0.18. It is classified as an Alpha Cygni variable due to the amplitude and periodicity of its brightness variation, as well as its spectral type. Its intrinsic variability is caused by pulsations in its unstable atmosphere. Rigel is generally the seventh-brightest star in the night sky and the brightest star in Orion, though it is occasionally outshone by Betelgeuse, which varies over a larger range.
A triple-star system is separated from Rigel by . It has an apparent magnitude of 6.7, making it 1/400th as bright as Rigel. Two stars in the system can be seen by large telescopes, and the brighter of the two is a spectroscopic binary. These three stars are all blue-white main sequence stars, each three to four times as massive as the Sun. Rigel and the triple system orbit a common center of gravity with a period estimated to be 24,000 years. The inner stars of the triple system orbit each other every 10 days, and the outer star orbits the inner pair every 63 years. A much fainter star, separated from Rigel and the others by nearly an arc minute, may be part of the same star system.
Nomenclature.
In 2016, the International Astronomical Union (IAU) included the name "Rigel" in the IAU Catalog of Star Names. According to the IAU, this proper name applies only to the primary component A of the Rigel system. In historical astronomical catalogs, the system is listed variously as HII33, Σ668, β555, or ADS3823. For simplicity, Rigel's companions are referred to as Rigel B, C, and D; the IAU describes such names as "useful nicknames" that are "unofficial". In modern comprehensive catalogs, the whole multiple star system is known as WDS 05145-0812 or CCDM 05145–0812.
The designation of Rigel as β Orionis (Latinized to Beta Orionis) was made by Johann Bayer in 1603. The "beta" designation is commonly given to the second-brightest star in each constellation, but Rigel is almost always brighter than α Orionis (Betelgeuse). Astronomer James B. Kaler has speculated that Rigel was designated by Bayer during a rare period when it was outshone by the variable star Betelgeuse, resulting in the latter star being designated "alpha" and Rigel designated "beta". Bayer did not strictly order the stars by brightness, instead grouping them by magnitude. Rigel and Betelgeuse were both considered to be of the first magnitude class, and in Orion the stars of each class are thought to have been ordered north to south. Rigel is included in the General Catalogue of Variable Stars, but since it already has a Bayer designation it has no separate variable star designation.
Rigel has many other stellar designations taken from various catalogs, including the Flamsteed designation 19Orionis (19 Ori), the Bright Star Catalogue entry HR1713, and the Henry Draper Catalogue number HD34085. These designations frequently appear in the scientific literature, but rarely in popular writing.
Observation.
Rigel is an intrinsic variable star with an apparent magnitude ranging from 0.05 to 0.18. It is typically the seventh-brightest star in the celestial sphere, excluding the Sun, although occasionally fainter than Betelgeuse. It is fainter than Capella, which may also vary slightly in brightness. Rigel appears slightly blue-white and has a B-V color index of −0.06. It contrasts strongly with reddish Betelgeuse.
Culminating every year at midnight on 12 December, and at 9:00pm on 24 January, Rigel is visible on winter evenings in the Northern Hemisphere and on summer evenings in the Southern Hemisphere. In the Southern Hemisphere, Rigel is the first bright star of Orion visible as the constellation rises. Correspondingly it is also the first star of Orion to set in most of the Northern Hemisphere. The star is a vertex of the "Winter Hexagon", an asterism that includes Aldebaran, Capella, Pollux, Procyon, and Sirius. Rigel is a prominent equatorial navigation star, being easily located and readily visible in all the world's oceans (the exception is the area north of the 82nd parallel north).
Spectroscopy.
Rigel's spectral type is a defining point of the classification sequence for supergiants. The overall spectrum is typical for a late B class star, with strong absorption lines of the hydrogen Balmer series as well as neutral helium lines and some of heavier elements such as oxygen, calcium, and magnesium. The luminosity class for B8 stars is estimated from the strength and narrowness of the hydrogen spectral lines, and Rigel is assigned to the bright supergiant class Ia. Variations in the spectrum have resulted in the assignment of different classes to Rigel, such as B8 Ia, B8 Iab, and B8 Iae.
As early as 1888, the heliocentric radial velocity of Rigel, as estimated from the Doppler shifts of its spectral lines, was seen to vary. This was confirmed and interpreted at the time as being due to a spectroscopic companion with a period of about 22 days. The radial velocity has since been measured to vary by about around a mean of .
In 1933, the Hα line in Rigel's spectrum was seen to be unusually weak and shifted towards shorter wavelengths, while there was a narrow emission spike about to the long wavelength side of the main absorption line. This is now known as a P Cygni profile after a star that shows this feature strongly in its spectrum. It is associated with mass loss where there is simultaneously emission from a dense wind close to the star and absorption from circumstellar material expanding away from the star.
The unusual Hα line profile is observed to vary unpredictably. Around a third of the time it is a normal absorption line. About a quarter of the time it is a double-peaked line, that is, an absorption line with an emission core or an emission line with an absorption core. About a quarter of the time it has a P Cygni profile; most of the rest of the time the line has an inverse P Cygni profile, where the emission component is on the short wavelength side of the line. Rarely, there is a pure emission Hα line. The line profile changes are interpreted as variations in the quantity and velocity of material being expelled from the star. Occasional very high-velocity outflows have been inferred, and, more rarely, infalling material. The overall picture is one of large looping structures arising from the photosphere and driven by magnetic fields.
Variability.
Rigel has been known to vary in brightness since at least 1930. The small amplitude of Rigel's brightness variation requires photoelectric or CCD photometry to be reliably detected. This brightness variation has no obvious period. Observations over 18 nights in 1984 showed variations at red, blue, and yellow wavelengths of up to 0.13 magnitudes on timescales of a few hours to several days, but again no clear period. Rigel's color index varies slightly, but this is not significantly correlated with its brightness variations.
From analysis of "Hipparcos" satellite photometry, Rigel is identified as belonging to the Alpha Cygni class of variable stars, defined as "non-radially pulsating supergiants of the Bep–AepIa spectral types". In those spectral types, the 'e' indicates that it displays emission lines in its spectrum, while the 'p' means it has an unspecified spectral peculiarity. Alpha Cygni type variables are generally considered to be irregular or have quasi-periods. Rigel was added to the General Catalogue of Variable Stars in the 74th name-list of variable stars on the basis of the Hipparcos photometry, which showed variations with a photographic amplitude of 0.039 magnitudes and a possible period of 2.075 days. Rigel was observed with the Canadian MOST satellite for nearly 28 days in 2009. Milli-magnitude variations were observed, and gradual changes in flux suggest the presence of long-period pulsation modes.
Mass loss.
From observations of the variable Hα spectral line, Rigel's mass-loss rate due to stellar wind is estimated be solar masses per year (/yr)—about ten million times more than the mass-loss rate from the Sun. More detailed optical and Kband infrared spectroscopic observations, together with VLTI interferometry, were taken from 2006 to 2010. Analysis of the Hα and Hγ line profiles, and measurement of the regions producing the lines, show that Rigel's stellar wind varies greatly in structure and strength. Loop and arm structures were also detected within the wind. Calculations of mass loss from the Hγ line give in 2006-7 and in 2009–10. Calculations using the Hα line give lower results, around . The terminal wind velocity is . It is estimated that Rigel has lost about three solar masses () since beginning life as a star of seven to nine million years ago.
Distance.
Rigel's distance from the Sun is somewhat uncertain, different estimates being obtained by different methods. The 2007 Hipparcos new reduction of Rigel's parallax is , giving a distance of with a margin of error of about 9%. Rigel B, usually considered to be physically associated with Rigel and at the same distance, has a Gaia Data Release 2 parallax of , suggesting a distance around . However, the measurements for this object may be unreliable.
Indirect distance estimation methods have also been employed. For example, Rigel is believed to be in a region of nebulosity, its radiation illuminating several nearby clouds. Most notable of these is the 5°-long IC 2118 (Witch Head Nebula), located at an angular separation of 2.5° from the star, or a projected distance of away. From measures of other nebula-embedded stars, IC2118's distance is estimated to be .
Rigel is an outlying member of the Orion OB1 Association, which is located at a distance of up to from Earth. It is a member of the loosely defined Taurus-Orion R1 Association, somewhat closer at . Rigel is thought to be considerably closer than most of the members of Orion OB1 and the Orion Nebula. Betelgeuse and Saiph lie at a similar distance to Rigel, although Betelgeuse is a runaway star with a complex history and might have originally formed in the main body of the association.
Stellar system.
Hierarchical scheme for Rigel's components
The star system of which Rigel is a part has at least four components. Rigel (sometimes called Rigel A to distinguish from the other components) has a visual companion, which is likely a close triple-star system. A fainter star at a wider separation might be a fifth component of the Rigel system.
William Herschel discovered Rigel to be a visual double star on 1 October 1781, cataloguing it as star 33 in the "second class of double stars" in his Catalogue of Double Stars, usually abbreviated to HII33, or as H233 in the Washington Double Star Catalogue. Friedrich Georg Wilhelm von Struve first measured the relative position of the companion in 1822, cataloguing the visual pair as Σ 668. The secondary star is often referred to as Rigel B or β Orionis B. The angular separation of Rigel B from Rigel A is 9.5 arc seconds to its south along position angle 204°. Although not particularly faint at visual magnitude 6.7, the overall difference in brightness from Rigel A (about 6.6 magnitudes or 440 times fainter) makes it a challenging target for telescope apertures smaller than .
At Rigel's estimated distance, Rigel B's projected separation from Rigel A is over 2,200astronomical units (AU). Since its discovery, there has been no sign of orbital motion, although both stars share a similar common proper motion. The pair would have an estimated orbital period of 24,000years. Gaia Data Release 2(DR2) contains a somewhat unreliable parallax for Rigel B, placing it at about , further away than the Hipparcos distance for Rigel, but similar to the Taurus-Orion R1 association. There is no parallax for Rigel in Gaia DR2. The Gaia DR2 proper motions for Rigel B and the Hipparcos proper motions for Rigel are both small, although not quite the same.
In 1871, Sherburne Wesley Burnham suspected Rigel B to be a binary system, and in 1878, he resolved it into two components. This visual companion is designated as component C (Rigel C), with a measured separation from component B that varies from less than to around . In 2009, speckle interferometry showed the two almost identical components separated by , with visual magnitudes of 7.5 and 7.6, respectively. Their estimated orbital period is 63years. Burnham listed the Rigel multiple system as β555 in his double star catalog or BU555 in modern use.
Component B is a double-lined spectroscopic binary system, which shows two sets of spectral lines combined within its single stellar spectrum. Periodic changes observed in relative positions of these lines indicate an orbital period of 9.86days. The two spectroscopic components Rigel Ba and Rigel Bb cannot be resolved in optical telescopes but are known to both be hot stars of spectral type around B9. This spectroscopic binary, together with the close visual component Rigel C, is likely a physical triple-star system, although Rigel C cannot be detected in the spectrum, which is inconsistent with its observed brightness.
In 1878, Burnham found another possibly associated star of approximately 13th magnitude. He listed it as component D of β555, although it is unclear whether it is physically related or a coincidental alignment. Its 2017 separation from Rigel was , almost due north at a position angle of 1°. Gaia DR2 finds it to be a 12th magnitude sunlike star at approximately the same distance as Rigel. Likely a K-type main-sequence star, this star would have an orbital period of around 250,000 years, if it is part of the Rigel system. A spectroscopic companion to Rigel was reported on the basis of radial velocity variations, and its orbit was even calculated, but subsequent work suggests the star does not exist and that observed pulsations are intrinsic to Rigel itself.
Physical characteristics.
Rigel is a blue supergiant that has exhausted the hydrogen fuel in its core, expanded and cooled as it moved away from the main sequence across the upper part of the Hertzsprung–Russell diagram. When it was on the main sequence, its effective temperature would have been around . Rigel's complex variability at visual wavelengths is caused by stellar pulsations similar to those of Deneb. Further observations of radial velocity variations indicate that it simultaneously oscillates in at least 19 non-radial modes with periods ranging from about 1.2 to 74 days.
Estimation of many physical characteristics of blue supergiant stars, including Rigel, is challenging due to their rarity and uncertainty about how far they are from the Sun. As such, their characteristics are mainly estimated from theoretical stellar evolution models. Its effective temperature can be estimated from the spectral type and color to be around . A mass of at an age of million years has been estimated by comparing evolutionary tracks, while atmospheric modeling from the spectrum gives a mass of .
Although Rigel is often considered the most luminous star within 1,000 light-years of the Sun, its energy output is poorly known. Using the Hipparcos distance of , the estimated relative luminosity for Rigel is about 120,000 times that of the Sun (), but another recently published distance of suggests an even higher luminosity of . Other calculations based on theoretical stellar evolutionary models of Rigel's atmosphere give luminosities anywhere between and , while summing the spectral energy distribution from historical photometry with the Hipparcos distance suggests a luminosity as low as . A 2018 study using the Navy Precision Optical Interferometer measured the angular diameter as . After correcting for limb darkening, the angular diameter is found to be , yielding a radius of . An older measurement of the angular diameter gives , equivalent to a radius of at . These radii are calculated assuming the Hipparcos distance of ; adopting a distance of leads to a significantly larger size.
Due to their closeness to each other and ambiguity of the spectrum, little is known about the intrinsic properties of the members of the Rigel BC triple system. All three stars seem to be near equally hot B-type main-sequence stars that are three to four times as massive as the Sun.
Evolution.
Stellar evolution models suggest the pulsations of Rigel are powered by nuclear reactions in a hydrogen-burning shell that is at least partially non-convective. These pulsations are stronger and more numerous in stars that have evolved through a red supergiant phase and then increased in temperature to again become a blue supergiant. This is due to the decreased mass and increased levels of fusion products at the surface of the star.
Rigel is likely to be fusing helium in its core. Due to strong convection of helium produced in the core while Rigel was on the main sequence and in the hydrogen-burning shell since it became a supergiant, the fraction of helium at the surface has increased from 26.6% when the star formed to 32% now. The surface abundances of carbon, nitrogen, and oxygen seen in the spectrum are compatible with a post-red supergiant star only if its internal convection zones are modeled using non-homogeneous chemical conditions known as the Ledoux Criteria.
Rigel is expected to eventually end its stellar life as a type II supernova. It is one of the closest known potential supernova progenitors to Earth, and would be expected to have a maximum apparent magnitude of around (about the same brightness as a quarter Moon or around 300 times brighter than Venus ever gets.) The supernova would leave behind either a black hole or a neutron star.
Etymology and cultural significance.
The earliest known recording of the name "Rigel" is in the "Alfonsine tables" of 1521. It is derived from the Arabic name ', "the left leg (foot) of Jauzah" (i.e. "rijl" meaning "leg, foot"), which can be traced to the 10th century. "Jauzah" was a proper name for Orion; an alternative Arabic name was ', "the foot of the great one", from which stems the rarely used variant names "Algebar" or "Elgebar". The "Alphonsine tables" saw its name split into "Rigel" and "Algebar", with the note, "et dicitur Algebar. Nominatur etiam Rigel." Alternate spellings from the 17th century include "Regel" by Italian astronomer Giovanni Battista Riccioli, "Riglon" by German astronomer Wilhelm Schickard, and "Rigel Algeuze" or "Algibbar" by English scholar Edmund Chilmead.
With the constellation representing the mythological Greek huntsman Orion, Rigel is his knee or (as its name suggests) foot; with the nearby star Beta Eridani marking Orion's footstool. Rigel is presumably the star known as "Aurvandil's toe" in Norse mythology. In the Caribbean, Rigel represented the severed leg of the folkloric figure "Trois Rois", himself represented by the three stars of Orion's Belt. The leg had been severed with a cutlass by the maiden "Bįhi" (Sirius). The Lacandon people of southern Mexico knew it as "tunsel" ("little woodpecker").
Rigel was known as "Yerrerdet-kurrk" to the Wotjobaluk koori of southeastern Australia, and held to be the mother-in-law of "Totyerguil" (Altair). The distance between them signified the taboo preventing a man from approaching his mother-in-law. The indigenous Boorong people of northwestern Victoria named Rigel as "Collowgullouric Warepil". The Wardaman people of northern Australia know Rigel as the Red Kangaroo Leader "Unumburrgu" and chief conductor of ceremonies in a songline when Orion is high in the sky. Eridanus, the river, marks a line of stars in the sky leading to it, and the other stars of Orion are his ceremonial tools and entourage. Betelgeuse is "Ya-jungin" "Owl Eyes Flicking", watching the ceremonies.
The Māori people of New Zealand named Rigel as "Puanga", said to be a daughter of "Rehua" (Antares), the chief of all-stars. Its heliacal rising presages the appearance of "Matariki" (the Pleiades) in the dawn sky, marking the Māori New Year in late May or early June. The Moriori people of the Chatham Islands, as well as some Maori groups in New Zealand, mark the start of their New Year with Rigel rather than the Pleiades. "Puaka" is a southern name variant used in the South Island.
In Japan, the Minamoto or Genji clan chose Rigel and its white color as its symbol, calling the star "Genji-boshi" (), while the Taira or Heike clan adopted Betelgeuse and its red color. The two powerful families fought the Genpei War; the stars were seen as facing off against each other and kept apart only by the three stars of Orion's Belt.
In modern culture.
The MS "Rigel" was originally a Norwegian ship, built in Copenhagen in 1924. It was requisitioned by the Germans during World War II and sunk in 1944 while being used to transport prisoners of war. Two US Navy ships have borne the name USS "Rigel". The SSM-N-6 Rigel was a cruise missile program for the US Navy that was cancelled in 1953 before reaching deployment.
The Rigel Skerries are a chain of small islands in Antarctica, renamed after originally being called Utskjera. They were given their current name as Rigel was used as an astrofix. Mount Rigel, elevation , is also in Antarctica.
Due to its brightness and its recognizable name, Rigel is also a popular fixture in science fiction. Fictional depictions of Rigel can be found in "Star Trek", "The Hitchhiker's Guide to the Galaxy", and many more books, films, and games.


NGC 6394

NGC 6394 is a barred spiral galaxy located in the constellation Draco. It is designated as SBb in the galaxy morphological classification scheme and was discovered by the American astronomer Lewis A. Swift on 7 July 1885.<ref name="NASA/IPAC"></ref>


NGC 6566

NGC 6566 is a compact elliptical galaxy within the constellation Draco. It is located about 250 million light-years (80 Mpc) away from the Sun. It was discovered on October 27, 1861 by the astronomer Heinrich d'Arrest.


25 Vulpeculae

25 Vulpeculae is a single star in the northern constellation of Vulpecula, located roughly 1,170 light years away from the Sun. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 5.50 This object is moving closer to the Earth with a heliocentric radial velocity of −11 km/s.
This is a Be star with a stellar classification of B6 IVe, matching the spectrum of an aging subgiant with a circumstellar disk of ionized gas. Cowley (1972) had it rated as a more evolved giant star with a class of B8 IIIn, where the 'n' notation indicates "nebulous" lines due to rapid rotation. It has a high rate of spin, showing a projected rotational velocity of 160 km/s. The star has 7 times the mass of the Sun and 11 times the Sun's radius. It is radiating 1,345 times the luminosity of the Sun from its photosphere at an effective temperature of 13,170 K.


Tadpole Galaxy

The Tadpole Galaxy is a disrupted barred spiral galaxy located 420 million light-years from Earth in the northern constellation Draco. Its most dramatic feature is a massive trail of stars about 280,000 light-years long; the size of the galaxy has been attributed to a merger with a smaller galaxy that is believed to have occurred about 100 million years ago. The galaxy is filled with bright blue star clusters.
It is hypothesized that a more compact intruder galaxy crossed in front of the Tadpole Galaxy—from left to right from the perspective of Earth—and was slung around behind the Tadpole by their mutual gravitational attraction. During this close encounter, tidal forces drew out the spiral galaxy's stars, gas, and dust, forming the conspicuous tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older; the tail's star clusters forming smaller satellites of the large spiral galaxy.


Beta Crateris

Beta Crateris, Latinized from β Crateris, is a binary star system in the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is located around 340 light years from the Sun.
This is an astrometric binary star system with an orbital period of 6.0 years and a projected separation of 8.3 AU. The orbit has an estimated semimajor axis of 9.3 AU. The primary, component A, is listed as an A-type giant star with a stellar classification of A2 III. However, Houk and Smith-Moore (1988) give a main sequence classification of A1 V, while Abt and Morrell (1995) list it as a subgiant star with a class of A2 IV. The spectrum shows enhanced barium, possibly as a result of a previous mass transfer event.
The companion, component B, is a white dwarf of class DA with an effective temperature of 36,885 K that has been cooling down for around four million years. It has an unusually low mass, 43% that of the Sun, suggesting that the white dwarf progenitor may have transferred matter to its companion. Alternative scenarios require either the evolution of a triple star system, or a binary system with highly eccentric orbit resulting in grazing interactions. The dwarf is a source of X-ray emission.
Name.
This star was one of the set assigned by the 16th century astronomer Al Tizini to Al Sharāsīf (ألشراسيف), the Ribs (of Hydra), which included the stars from β Crateris westward through κ Hydrae.
According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Sharāsīf" were the title for two stars : β Crateris as "Al Sharasīf II" and κ Hydrae as "Al Sharasīf I".
In Chinese, (), meaning "Wings (asterism)", refers to an asterism consisting of β Crateris, α Crateris, γ Crateris, ζ Crateris, λ Crateris, ν Hydrae, η Crateris, δ Crateris, ι Crateris, κ Crateris, ε Crateris, HD 95808, HD 93833, θ Crateris, HD 102574, HD 100219, HD 99922, HD 100307, HD 96819, χ1 Hydrae, HD 102620 and HD 103462. Consequently, β Crateris itself is known as (, .)


Beta Trianguli

Beta Trianguli (Beta Tri, β Trianguli, β Tri) is the Bayer designation for a binary star system in the constellation Triangulum, located about 127 light years from Earth. Although the apparent magnitude is only 3.0, it is the brightest star in the constellation Triangulum.
This is a double-lined spectroscopic binary star system with an orbital period of 31.39 days and an eccentricity of 0.53. The members are separated by a distance of less than 5 AU. The primary component has a stellar classification of A5IV, indicating that it has evolved away from the main sequence and is now a subgiant star. However, the classification is uncertain and not consistent with the mass derived from the orbit. It is among the least variable of the stars that were observed by the Hipparcos spacecraft, with a magnitude varying by only 0.0005.
Based on observations using the Spitzer Space Telescope, as reported in 2005, this system is emitting an excess of infrared radiation. This emission can be explained by a circumbinary ring of dust. The dust is emitting infrared radiation at a blackbody temperature of 100 K. It is thought to extend from 50 to 400 AU away from the stars.


NGC 2266

NGC 2266 is an open cluster in the constellation Gemini. Its apparent size is 5 arc minutes. Its distance is . It was discovered by German-British astronomer William Herschel on 7 December 1785.


Upsilon2 Centauri

Upsilon2 Centauri (υ2 Centauri) is a binary star system in the southern constellation Centaurus. It is visible to the naked eye with an apparent visual magnitude of +4.33. Based upon an annual parallax shift of just 2.57 mas as seen from Earth, this star is located roughly 1,300 light years from the Sun. Relative to its neighbors, the system has a peculiar velocity of and it may form a runaway star system.
This is a single-lined spectroscopic binary star system with an orbital period of 207.357 days and an eccentricity of 0.55. The primary component has the spectrum of an evolved F-type giant/bright giant hybrid with a stellar classification of F7 II/III. It is around 46 million years old with 6.9 times the mass of the Sun. The star is radiating 3,919 times the Sun's luminosity from its photosphere at an effective temperature of 6,495 K.


Omicron Lupi

Omicron Lupi (ο Lup) is a binary star in the southern constellation of Lupus. It is a visible to the naked eye with a combined apparent visual magnitude of 4.323. Based upon an annual parallax shift of 8.07 mas as seen from Earth, it is located around 400 light years from the Sun, give or take 30 light years. At that distance, the visual magnitude of the system is diminished by an extinction factor of due to interstellar dust. It is a member of the Upper Centaurus Lupus subgroup of the nearby Scorpius–Centaurus Association.
This is a visual binary star system with the components having an angular separation of 0.1 arc seconds. The primary, component A, is a magnitude 4.84 B-type subgiant star with a stellar classification of B5 V. It displays radial velocity variations indicating it has an unseen second companion orbiting at a separation of at least 17 AU with a period of 27 years or more. The spectrum of the primary displays a Zeeman effect indicating a magnetic field with a strength ranging from −94 to 677 G. The visible companion, component B, has a visual magnitude of 5.27.


GAMA202627

GAMA202627 (also known as G202627) is a barred spiral galaxy similar to our own Milky Way.
The galaxy was described in a 2012 paper
by astronomer Dr Aaron Robotham, jointly from the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) and the University of St Andrews in Scotland, when he searched for groups of galaxies similar to ours in the most detailed map of the local Universe yet, the Galaxy And Mass Assembly survey (GAMA). The Galaxy and Mass Assembly (GAMA) survey is an international collaboration led from ICRAR and the Australian Astronomical Observatory to map our local Universe in closer detail. The galaxy has a redshift measured at z = 0.051219 +/- 0.000123, which corresponds to a distance of 705 Mly, or 216 Mpc.
Dr Robotham noted, "We found about 3% of galaxies similar to the Milky Way have companion galaxies like the Magellanic Clouds, which is very rare indeed. In total we found 14 galaxy systems that are similar to ours, with two of those being an almost exact match."
The Milky Way is surrounded by its close companions, the Large and Small Magellanic Clouds, which are visible in the southern sky. Many galaxies have smaller galaxies in orbit around them, but few have two that are as large as the Magellanic Clouds. That is why GAMA202627 is so unique as it has two massive satellite galaxies in close proximity.


Delta Ursae Minoris

Delta Ursae Minoris, Latinized from δ Ursae Minoris, formally named Yildun , is a white-hued star in the northern circumpolar constellation of Ursa Minor, forming the second star in the bear's tail. It is visible to the naked eye with an apparent visual magnitude of 4.36. Based upon an annual parallax shift of 18.95 mas as seen from Earth, it is located 172 light years from the Sun. The star is moving closer to the Sun with a radial velocity of about −8 km/s.
Description.
This is an A-type main-sequence star with a stellar classification of A1 Van, where the 'n' indicates "nebulous" absorption lines in the spectrum due to rapid rotation. It is spinning with a projected rotational velocity of 180 km/s, which is giving the star an oblate shape with an equatorial bulge that is an estimated 7% larger than the polar radius. The star is about 327 million years old with 2.35 times the mass of the Sun. It is radiating about 48 times the Sun's luminosity from its photosphere at an effective temperature of 9,911 K.
δ Ursae Minoris has a 12th magnitude common proper-motion companion at an angular separation of 4.5 arc seconds along a position angle of 67.3°, which is a projected separation of 237.4 au at the distance of δ Ursae Minoris. The pair were resolved using adaptive optics. The companion is assumed to be gravitationally bound and to have a mass of approximately .
Nomenclature.
"δ Ursae Minoris" (Latinised to "Delta Ursae Minoris") is the star's Bayer designation.
It bore the traditional name "Yildun" (also spelled "Vildiur" or "Gildun") from the Turkish "yıldız" "star". 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 "Yildun" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.


Rho3 Eridani

Rho3 Eridani, Latinized from ρ3 Eridani, is a star located in the constellation Eridanus. It forms an asterism with Rho1 and Rho2 Eridani, south of Cetus, in the upper north east portion of Eridanus. The star has an apparent visual magnitude of 5.26, which is bright enough to be seen with the naked eye on a dark, clear night. The distance to this star, as determined via the parallax method, is about 136 light years.
This is an A-type main sequence star with a stellar classification of A5 V. (Some sources list it as A8 V.) It is some 500 million years old and is spinning rapidly with a projected rotational velocity of 186 km/s. This rotation is giving the star a slightly oblate shape, with the equator being 5% larger than the poles. The star has about 120% of the radius of the Sun, and 183% of the Sun's mass. It shines with 10 times the solar luminosity from its outer atmosphere at an effective temperature of 7,400 K.


HD 203030

HD 203030 is a single orange (K-type) main-sequence, located approximately 128 light-years away in the constellation of Vulpecula, taking its primary name from its Henry Draper Catalogue designation.
History and nomenclature.
The designation HD 203030 is from the Henry Draper Catalogue, which is based on spectral classifications made between 1911 and 1915 by Annie Jump Cannon and her co-workers, and was published between 1918 and 1924.
Characteristics.
HD 203030 is a Sun-like K-type main-sequence star. It is likely very young, belonging to 45 million years old IC 2391 open cluster.
Planetary system.
In 2006, a direct imaging have discovered what was believed to be a brown dwarf of spectral class L7.5 at the projected separation 487.1 AU. The companion was proven to be in the bound orbit by 2014. In 2017, the planetary system reanalysis have indicated what the star HD 203030 is probably very young, and therefore both the primary and the observed companion is less massive than previously thought, placing the companion object within planetary definition. In 2019, the rotational period of HD 203030 B was measured to be equal to 7.5 hours, and patchy cloud cover was detected.


HD 34968

HD 34968 is a binary star system in the southern constellation Lepus. The combined apparent visual magnitude of 4.69 is bright enough to be visible to the naked eye. The distance to HD 34968 can be estimated from its annual parallax shift of , yielding a range of 374 light years. It is moving further away from the Earth with a heliocentric radial velocity of 31 km/s, having come within some 3,686,000 years ago.
The primary member, component A, is a magnitude 4.73 star. Houk and Smith-Moore (1978) gave this object a stellar classification of A0 V, indicating it is an ordinary A-type main-sequence star. Gray and Garrison (1987) classified it as B9.5 III and noted that the spectrum is slightly variable. It is of the way through its main sequence lifetime, with 3.34 times the mass of the Sun and 2.0 times the Sun's radius. The star is spinning with a projected rotational velocity of 84 km/s. It is radiating 245 times the Sun's luminosity from its photosphere at an effective temperature of 10,046
The fainter secondary, component B, is a magnitude 8.45 star at an angular separation of along a position angle of 279°, as of 2008.


HD 77258

HD 77258 is a binary star system in the southern constellation of Vela. It has the Bayer designation w Velorum, while "HD 77258" is the identifier from the "Henry Draper Catalogue". The system is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.45. It is located at a distance of approximately 218 light years from the Sun based on parallax. The radial velocity of the system barycenter is poorly constrained, but it appears to be drifting away at a rate of ~7 km/s.
The radial velocity variation of this system was first reported by H. K. Palmer in 1904. It is a single-lined spectroscopic binary with an orbital period of 74.14 days and an eccentricity (ovalness) of 0.00085, indicating the orbit is essentially circular. The visible component has a stellar classification of G8-K1III, matching a late G-type giant star. This is an evolved star that has exhausted the supply of hydrogen at its core, then cooled and expanded away from the main sequence. In 1975, S. Maladora flagged the spectrum as peculiar.
The level of ultraviolet flux coming from this system suggests the companion is a hot A-type star of class A6.5 or A7. The system is a source of X-ray emission.


Lambda Lupi

Lambda Lupi, Latinized from λ Lupi, is a triple star system in the southern constellation of Lupus. It is visible to the naked eye with a combined apparent visual magnitude of 4.04. Based upon an annual parallax shift of just 4.20 mas as seen from Earth, it is located roughly 800 light years from the Sun. The system has a peculiar velocity of relative to its neighbors, making it a candidate runaway star system. It is a member of the Upper-Centaurus Lupus sub-group in the Scorpius-Centaurus OB association.
The two visible components of this system orbit each other over a period of 70.8 years with a large eccentricity of 0.63. The primary component has a visual magnitude of 4.43, while the secondary is of magnitude 5.23. Both are B-type main sequence stars with a stellar classification of B3 V. One of the pair is itself a double-lined spectroscopic binary, making this a triple star system.


NGC 4700

NGC 4700 is a spiral galaxy located about 50 million light years away in the constellation of Virgo. NGC 4700 was discovered in March 1786 by the British astronomer William Herschel who noted it as a "very faint nebula".
NGC 4700 was imaged by Hubble in 2012, showing an abundance of star-forming regions similar to the Orion Nebula.