Gliese 752

Gliese 752 is a binary star system in the Aquila constellation. This system is relatively nearby, at a distance of about 19 light years. This system consists of two M-type stars. The primary star is the magnitude 9 "Gliese (GJ) 752 A". The secondary star is the dim magnitude 17 "Gliese (GJ) 752 B", more commonly referred to as "VB 10". This stellar pair form a binary star system separated by about 74 arc seconds (~434 AU). This system is also known for its high proper motion of about 1 arc second a year.
In August 2018, a group of scientist using measurements taken from the CARMENES spectrograph, on the Calar Alto Observatory located in Spain, announced they had detected a planet orbiting the larger of the stars, HD 180617 (Gliese 752 A). The measurements indicated the presence of a planet with a minimum mass comparable to Neptune on an orbit partly located within the habitable zone.
The name and number are from the "Catalogue of Nearby Stars", published by German astronomer Wilhelm Gliese in 1969.
Interior dynamics of the Gliese 752 stars.
Before the Hubble Space Telescope observation of "Gliese 752" system, astronomers thought magnetic fields in stars required the same dynamo process that creates magnetic fields on the Sun. In the classic solar model heat generated by nuclear fusion reactions at the star's center escapes through a radiative zone just outside the core. The heat travels from the radiative core to the star's surface through a convection zone. In this region, heat bubbles to the surface by motions similar to boiling in a pot of water.
Dynamos, which accelerate electrons to create magnetic forces, operate when the interior of a star rotates faster than its surface. Recent studies of the Sun indicate its convection zone rotates at nearly the same rate at all depths. This means the solar dynamo must operate in the more rapidly rotating radiative core just below the convective zone.
Gliese 752 A characteristics.
The primary star, also known as "Wolf 1055", is a type M2.5 red dwarf with about half the size and mass as the Sun and considerably cooler at 3354 K. This star was first observed to be a high proper motion star by the German astronomer Max Wolf with his pioneering use of astrophotography. He added this star to his extensive catalog of such stars in 1919. It is a variable star with the variable star catalog name "V1428 Aquilae". It is a "BY Draconis" type variable star subject to flare events.
Gliese 752 B characteristics.
Gliese 752 was not known to be a binary star system until the discovery of a small dim secondary star by George Van Biesbroeck in 1944. This star is identified as "VB 10" in Van Biesbroeck's star catalog. This star is notable for its very low mass. At .08 solar mass it is near the lower mass limit for a star. It is also quite small at 10% of the solar radius.
This star is a type M8V red dwarf. This star is also known for its very low luminosity, with an absolute magnitude of nearly 19, due to its very cool surface temperature of only 2600°K. It is a variable star with the variable star catalog name "V1298 Aquilae". This star is a "UV Ceti" type variable star also subject to flare events. It shares the large proper motion, along with the tendency to flare, with the primary star.
In 2009 the discovery of the extrasolar planet, "VB 10b", was announced in orbit around this star. However a subsequent spectrographic survey failed to confirm the presence of any large planets in orbit around this star.


HD 8574

HD 8574 is a single star in the equatorial constellation of Pisces. It can be viewed with binoculars or a telescope, but not with the naked eye having a low apparent visual magnitude of +7.12. The distance to this object is 146 light years based on parallax, and it has an absolute magnitude of 3.88. The star is drifting further away from the Sun with a radial velocity of +18 km/s. It has a relatively high proper motion, advancing across the celestial sphere at the rate of 0.298 arc seconds per annum.
The star HD 8574 is named Bélénos. The name was selected in the NameExoWorlds campaign by France, during the 100th anniversary of the IAU. Bélénos was the god of light, of the Sun, and of health in Gaulish mythology.
This object is an F-type star with a stellar classification of F8 and unknown luminosity class. The star is five billion years old and is spinning with a projected rotational velocity of 6.6 km/s. It has 1.1 times the mass of the Sun and 1.4 times the Sun's radius. The star is radiating 2.3 times the luminosity of the Sun from its photosphere at an effective temperature of 6,065 K.
In 2001, an extrasolar planet in an eccentric orbit was announced by the European Southern Observatory. The discovery was published in 2003. This object has at least double the mass of Jupiter and has an eccentric orbit with a period of .


22 Scorpii

22 Scorpii (i Scorpii) is a single star in the southern zodiac constellation of Scorpius. It is faintly visible to the naked eye with an apparent visual magnitude of 4.78. The distance to this star can be estimated from its annual parallax shift of , which yields a value of around 410 light years. The star is embedded in, or adjacent to, a diffuse nebulous cloud.
This is a B-type main-sequence star with a stellar classification of B3 V. It is ten million years old and has a high rate of spin with a projected rotational velocity of 169 km/s. The star has about six times the mass of the Sun and is radiating 335 times the Sun's luminosity from its photosphere at an effective temperature of 19,600 K.


List of stars in Taurus

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


Kepler-635

Kepler-635 (KOI-649, KIC 5613330) is an F7V star with an extrasolar planetary system discovered by the Kepler space telescope. The star was first thought to be variable, but later determined to be static.
Planetary system.
The planetary system contains one confirmed planet and was first detected by the Kepler space telescope.


HD 96566

HD 96566 is a single star in the southern constellation of Carina. It has the Bayer designation z1 Carinae; "HD 96566" is the identifier from the "Henry Draper Catalogue". This object has a yellow hue and is visible to the naked eye with an apparent visual magnitude of +4.62. The star is located at a distance of approximately 376 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −1 km/s. It has an absolute magnitude of −0.81.
This is an aging G-type giant star with a stellar classification of G7.5III, which indicates it has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It has an estimated 3.6 times the mass of the Sun and has grown to 20 times the Sun's radius. The metallicity, or abundance of elements other than hydrogen and helium, is about the same as in the Sun. It is radiating about 214 times the Sun's luminosity from its photosphere at an effective temperature of 4,913 K.


HD 89890

HD 89890 is the brightest member of a multiple star system with at least four components, located in the southern constellation of Vela. It is visible to the naked eye with an apparent visual magnitude of 4.50. The annual parallax shift of provides a distance estimate of around 1,200 light years. It is moving further away from Earth with a heliocentric radial velocity of +10 km/s.
System.
The Washington Double Star Catalog lists three visible components for this system. The brightest, component A, is of visual magnitude 4.50. Component B has a magnitude of 7.179, and as of 2000 lies at an angular separation of from A, along a position angle (PA) of 102°. Component C is a magnitude 9.125 star at a separation of from A at a PA of 191°. The physical link between the stars was described on the basis of their dynamic parallax and mean velocities. The three components A, B, and C have Gaia Data Release 2 parallaxes of , , and respectively.
Properties.
Component A has a stellar classification of B3 III, and is categorized as a Be star. It shows photometric variations with multiple periods around 4.6 days and line-profile variations with a period of 2.318 days. The radial velocity of this star is constant. It has 10 times the Sun's radius and shines with 3,082 times the Sun's luminosity from its photosphere at an effective temperature of 15,000 K.
The component B shows a variation in spectra consistent with being a double-lined spectroscopic binary. The brighter member (Ba) is a silicon star with a class of A0 IVpSi, while the fainter component (Bb) is of type A2. Component C has a class of K0 III, indicating it is an evolved giant star. The measured effective temperature of C is 5,500 K. The fact that component A most likely shares a common origin with C suggests that the former is much older than expected, and may actually be a blue straggler formed from the merger of a close binary. This could have been caused by the gravitational influence of an unseen companion of A.


A Cancri

The Bayer designation A Cancri is shared by two stars/star systems in the constellation Cancer:
See also.
α Cancri


NGC 2787

NGC 2787 is a barred lenticular galaxy approximately 24 million light-years away in the northern circumpolar constellation of Ursa Major. It was discovered on December 3, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer described it as, "bright, pretty large, a little extended 90°, much brighter middle, mottled but not resolved, very small (faint) star involved to the southeast". The visible galaxy has an angular size of and an apparent visual magnitude of 11.8.
This galaxy is small and isolated with a morphological classification of SB(r)0+, which indicates a barred spiral (SB) with a ring around the bar (r). Being a lenticular galaxy, it has the large halo of an elliptical galaxy. The disk is inclined at an angle of to the line of sight from the Earth, with the major axis aligned along a position angle of . The galaxy has an unusually high mass-to-light ratio, much greater than for a typical spiral galaxy. The distribution of the galaxy's neutral hydrogen forms a clumpy ring with a radius of , double that of the visible galaxy, with a mass of . This ring appears misaligned with the central disk.
NGC 2787 contains a low-ionization nuclear emission-line region (LINER) at its core, which is a type of region that is characterized by spectral line emission from weakly ionized atoms. LINERs are very common within lenticular galaxies, with approximately one-fifth of nearby lenticular galaxies containing LINERs. The supermassive black hole at the center has a mass of . The central region of the galaxy contains dust rings that are tilted with respect to the disk, which may be the result of an encounter with another galaxy.


40 Leonis

40 Leonis is a star in the zodiac constellation of Leo. It is faintly visible to the naked eye, having an apparent visual magnitude of 4.80. An annual parallax shift of 46.80 mas, as seen from Earth's orbit, yields a distance estimate of 69.7 light years. It is moving away from the Sun with a radial velocity of 5.9 km/s and has a relatively high proper motion, traversing the sky at the rate of 0.315 arcseconds per year.
This is an F-type star with a stellar classification of F6 IV-V, which indicates the spectrum shows traits of both a main sequence star and a more evolved subgiant star. It is a suspected Delta Scuti variable and shows a depleted lithium abundance. The star is about 2.6 billion years old with a relatively high rate of spin for its age, showing a projected rotational velocity of about 17 km/s. It has 1.35 times the mass of the Sun and 1.68 times the Sun's radius. 40 Leonis is radiating around 4.4 times the Sun's luminosity from its photosphere at an effective temperature of roughly 6,450 K.
An X-ray emission with a luminosity of has been detected from this position, which may be coming from an undetected short-period, low mass companion. 40 Leonis has a common proper motion companion, NLTT 23781, with a wide angular separation of 5,230″ (1.453°), corresponding to a physical separation of at least . This magnitude 16.48 star has a class of M5 and is overluminous for its type, which may mean it is a binary system.


WASP-60

WASP-60 is a F-type main-sequence star about 1420 light-years away. The stars age is much younger than the Sun's at 1.7 billion years. WASP-60 is enriched in heavy elements, having 180% of the solar abundance of iron. The star does not have noticeable starspot activity, an unexpected observation for a relatively young star. The age of WASP-60 determined by different methods is highly discrepant though, and it may actually be an old star which experienced an episode of spin-up in the past.
The star was named Morava in 2019 by Serbian amateur astronomers as part of the "nameexoworlds" contest.
A multiplicity survey in 2015 did not detect any stellar companions to WASP-60.
Planetary system.
In 2012 a transiting hot Jupiter planet b was detected on a tight, circular orbit. The planet was named "Vlasina" by Serbian astronomers in December 2019.
Its equilibrium temperature is .
Measurement of the Rossiter–McLaughlin effect in 2018 revealed WASP-60b is on a retrograde orbit relative to the equatorial plane of the star, orbital obliquity equal to 129°.


Eta Cephei

Eta Cephei (η Cep, η Cephei) is a star in the northern circumpolar constellation of Cepheus. It shares the name Al Kidr with θ Cep, although the meaning of this name is unknown. With an apparent visual magnitude of 3.4, this is a third magnitude star that, according to the Bortle Dark-Sky Scale, is readily visible to the naked eye. Parallax measurements put it at a distance of from Earth.
Etymology.
Eta Cephei, along with α Cep (Alderamin) and β Cep (Alfirk), were identified as "Al Kawākib al Firḳ" (الكوكب الفرق), meaning "the Stars of The Flock" by Ulug Beg.
In Chinese, (), meaning "Celestial Hook", refers to an asterism consisting of η Cephei, 4 Cephei, HD 194298, θ Cephei, α Cephei, ξ Cephei, 26 Cephei, ι Cephei and ο Cephei. Consequently, the Chinese name for η Cephei itself is (, .).
Properties.
Eta Cephei is a subgiant star with a stellar classification of K0 IV, which indicates it is exhausting the supply of hydrogen at its core and is in the process of evolving into a giant star. With 1.6 times the Sun's mass, at an age of 2.5 billion years it has reached a radius four times larger than the Sun and a luminosity ten times greater. It is radiating this energy from its outer atmosphere at an effective temperature of 4,950 K, giving it the orange-hued glow of a K-type star. Eta Cephei has a high proper motion across the celestial sphere and a large peculiar velocity of .
Hunt for substellar objects.
According to Nelson & Angel (1998), Eta Cephei would show two significant periodicities of 164 days and 10 years respectively, hinting at the possible presence of one or more jovian planets in orbit around the subgiant. The authors have set an upper limit of 0.64 Jupiter masses for the putative inner planet and 1.2 Jupiter masses for the putative outer one. Also Campbell et al. (1988) inferred the existence of planetary objects or even brown dwarfs less massive than 16.3 Jupiter masses.
However, more recent studies have not yet confirmed the existence of any substellar companion around Eta Cephei. McDonald Observatory team has set limits to the presence of one or more planets with masses between 0.13 and 2.4 Jupiter masses and average separations spanning between 0.05 and 5.2 AU.


NS Puppis

NS Puppis (NS Pup) is an irregular variable star in the constellation Puppis. Its apparent magnitude varies between 4.4 and 4.5.
NS Puppis is a naked eye star, given the h1 and the Bright Star Catalogue number 3225. It was considered to be a stable star until 1966. It was given the variable star designation NS Puppis in 1975.
h2 Puppis is another luminous K-type star with almost the same visual magnitude about a degree to the southeast.


Chi Serpentis

Chi Serpentis (χ Ser, χ Serpentis) is a solitary star in the Serpens Caput section of the equatorial constellation Serpens. Based upon an annual parallax shift of 14.84 mas as seen from Earth, it is located around 220 light years from the Sun. The star is bright enough to be faintly visible to the naked eye, having an apparent visual magnitude of +5.30.
In 1966 it was listed as a suspected spectroscopic binary, but it is believed to be single. This is a chemically peculiar star Ap star with a stellar classification of , indicating the spectrum shows abnormal excesses of manganese and europium. The star has 2.11 times the mass of the Sun and about 1.9 times the Sun's radius. It is radiating 26 times the solar luminosity from its photosphere at an effective temperature of 9,557 K. At the age of 212 million years, it is spinning with a rotation period of 1.6 days.
Chi Serpentis is classified as an Alpha2 Canum Venaticorum type variable star, and its magnitude varies by 0.03 with a period of 1.5948 days. The pattern of variation in the spectrum suggest there are regions of enhanced strontium, chromium, iron, titanium, and magnesium on the surface of the star. The averaged quadratic field strength of the surface magnetic field is .


NGC 5676

NGC 5676 is an unbarred spiral galaxy in the constellation Boötes.
Disk.
This spiral galaxy is notably asymmetric. The spiral arms on the south side of the galaxy are chaotic in appearance, whereas the spiral arms on the north side of the galaxy are very well-defined. Also, the spiral arms on the south side of the disk extend twice as far from the galaxy's nucleus as the spiral arms on the north side. Because of the fragmentary appearance of some of the spiral arms, this galaxy is classified as a flocculent galaxy.
Star formation.
The north part of the disk also contains what appears to be a very intense region of star formation. Unusually, the star formation within this region appears to be more intense than the star formation in the galaxy's nucleus, and it is the brightest infrared source within the disk.


Pistol Nebula

The Pistol Nebula is located in the constellation Sagittarius. It surrounds one of the most luminous stars known, the Pistol Star. Both are located 25,000 light years away from Earth in the Quintuplet cluster, near the center of the Milky Way galaxy. The nebula contains approximately 9.3 solar masses worth of ionized gas that was ejected by the star several thousand years ago. The nebula was named in the 1980s for its shape as seen in low resolution images that were available at the time. The Pistol Star, a luminous blue variable is 1.6 million times brighter than the Sun making it one of the most luminous stars in the Milky Way.


Xi Lupi

The Bayer designation ξ Lupi (Xi Lupi) is shared by two star systems in the constellation Lupus:
Listed in the Washington Double Star Catalog as WDS J15569-3358, this double star most likely forms a wide binary star system. As of epoch 2004.38, the pair had an angular separation of along a position angle of . The difference in visual magnitude between the two stars is .


3C 234

3C 234 is a Seyfert galaxy with a quasar-like appearance located in the constellation Leo Minor.


Beta Hydrae

Beta Hydrae, Latinized from β Hydrae, is a double star in the equatorial constellation of Hydra. Historically, Beta Hydrae was designated 28 Crateris, but the latter fell out of use when the IUA defined the permanent constellation boundaries in 1930. The system is faintly visible to the naked eye with a combined apparent visual magnitude that ranges around 4.29. It is located at a distance of approximately 310 light years from the Sun based on parallax.
The double nature of this system was first reported by English astronomer John Herschel in 1834. The brighter primary, designated component A, has an average visual magnitude of 4.67, while the secondary, component B, is of magnitude 5.47. As of 2002, the secondary is located at an angular separation of from the primary, along a position angle of 28.5°.
The brighter component is an α2 Canum Venaticorum variable that changes in brightness with a period of 2.344 days and an amplitude of 0.04 in visual magnitude. It is a magnetic chemically-peculiar star with an average quadratic field strength of . The star is around 178 million years old with 3.4 times the mass of the Sun and 3.9 times the Sun's radius. On average, it is radiating 257 times the luminosity of the Sun from its photosphere at an effective temperature of 10,980 K.
In 1972, M. R. Molnar found a stellar classification of B9IIIp Si for β Hydrae A, showing an abundance anomaly for silicon. R. F. Garrison and R. O. Gray assigned it a class of kB8hB8HeA0VSi in 1994. This notation indicates the Calcium K line matches a star of class B8, the hydrogen lines also match a B8 spectrum, while the helium lines match an A-type main-sequence star of class A0V. They noted that the hydrogen lines have "curious rounded profiles". Later studies list abundance anomalies of silicon, chromium, and strontium.
Cultural signification.
The Kalapalo people of Mato Grosso state in Brazil called this star and ψ Hya "Kafanifani".


VY Pyxidis

VY Pyxidis is a BL Herculis variable (type II Cepheid) in the constellation of Pyxis. It ranges between apparent magnitudes
7.13 and 7.40 over a period of 1.23995 days. Located around 650 light-years distant, it shines with a luminosity approximately 45 times that of the Sun and has a surface temperature of 5892 K.


Zeta Puppis

Zeta Puppis (ζ Puppis, abbreviated Zeta Pup, ζ Pup), formally named Naos , is a star in the constellation of Puppis.
The spectral class of O4 means this is one of the hottest, and most luminous, stars visible to the naked eye. It is one of the sky's few naked-eye class O-type stars as well as one of the closest to Earth. It is a blue supergiant, one of the most luminous stars in the Milky Way. Visually it is over 10,000 times brighter than the Sun, but its high temperature means that most of its radiation is in the ultraviolet and its bolometric luminosity is over 500,000 times that of the Sun. It is also the 72nd brightest star in terms of apparent magnitude from Earth.
Naos is typical of O-type stars in having an extremely strong stellar wind, measured at 2,500 km/s, which sees the star shed more than a millionth of its mass each year, or about 10 million times that shed by the Sun over a comparable time period.
Nomenclature.
"ζ Puppis" (Latinised to "Zeta Puppis") is the star's Bayer designation.
It bears the name "Naos", from the Greek "ναύς" "ship", and in Arabic "Suhail Hadar" (سهيل هدار, possibly meaning "roaring bright one"). 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 "Naos" for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.
Namesake.
USS Naos (AK-105) was a United States Navy Crater class cargo ship named after the star.
Physical characteristics.
Zeta Puppis has been extensively studied because of its rareness and relative closeness to Earth, but its physical parameters and distance are still poorly known. It would be a valuable step on the cosmic distance ladder, clarifying the distance of other high luminosity stars in the Milky Way galaxy and external galaxies.
The spectral type is O4If(n)p. O4 indicates a hot massive hydrogen-burning star, typically 40,000-44,000K. The "f" indicates that the spectrum has emission lines of ionised Helium and Nitrogen, not uncommon in somewhat evolved hot O stars and typically identified by the composite emission and absorption profile of the 468.6nm HeII spectral line. The "n" (for nebulous) indicates broadened absorption lines, caused by rapid rotation of the star, in this case over 220 km/s at the equator. The "p" is a general spectral indicator of peculiarity. This combination of spectral characters is unusual because evolved hot stars are expected to rotate relatively slowly after braking by a strong stellar wind, and only 8 stars of this type are known in the Milky Way. The spectral type complicates determination of physical parameters as the standard spectral luminosity indicator lines are peculiar and this type of star cannot be fully modelled. The enhanced Helium and Nitrogen and the lower surface gravity indicates some degree of evolution away from the zero age main sequence and Zeta Puppis is ranked as a supergiant.
The angular size of Zeta Puppis has been measured interferometrically to be 0.41 mas, and photometrically to be 0.38 mas. A known distance would directly give the actual size of the star, which would confine other characters such as luminosity and mass. Publications of the distance of Zeta Puppis vary from around 300pc based on dynamical measurements or parallax to over 600pc based on physical modelling. This leads to estimates of luminosity between 550,000 and 800,000 times the Sun, mass between 22.5 and 56 times the Sun, and radius between 14 and 26 times the Sun. The revised Hipparcos parallax value give a distance of ± 4%, much lower than expected from the observed characteristics of the star.
Zeta Puppis has been reported to be variable and is classified as a suspected Alpha Cygni variable. It shows variations in Hα spectral line profiles and x-ray luminosity on timescales less than a day.
Helium.
In 1896, Williamina Fleming observed mysterious spectral lines from Zeta Puppis, which fit the Rydberg formula if half-integers were used instead of whole integers. It was later found that these were due to ionized helium.
Origin.
Early suggestions for the birthplace of Zeta Puppis were the very young Vela R2 stellar association at around 800pc and the Vela OB2 association at 450pc. Neither origin is satisfactory. A distance of 800pc requires an abnormally high luminosity, while the Vela OB2 association is much older than Zeta Puppis and the space velocity does not lead back to that cluster.
Many physical models and the original Hipparcos parallax measurements did lead to a distance value of around 450pc, but the revised Hipparcos reduction gave a much lower distance near 333pc. A recent dynamical study points to Zeta Puppis originating in the Trumpler 10 OB association at around 300pc, but this is also a much older cluster and physical models still lead to a distance of 450-600pc.
Zeta Puppis shows a high space velocity and very high rotation rate, and it has been speculated that it is a runaway star resulting from a supernova in a binary system, possibly the progenitor of the Gum Nebula but evidence supporting this is sparse.


Q Velorum

The Bayer designations q Velorum and Q Velorum are distinct. Due to , both designations link here. For the star


HD 220766

HD 220766 is a double star in the equatorial constellation of Aquarius. The primary is a K-type giant star with a stellar classification of K0III and an apparent magnitude of 6.44. It has a faint, magnitude 12 companion, located at an angular separation of 5.0″ along a position angle of 132° (as of 1933).


Lambda Leonis

Lambda Leonis (λ Leonis, abbreviated Lam Leo, λ Leo), formally named Alterf , is a star in the constellation of Leo. The star is bright enough to be seen with the naked eye, having an apparent visual magnitude of 4.32 Based upon an annual parallax shift of 0.00991 arcseconds, it is located about 329 light-years from the Sun. At that distance, the visual magnitude of the star is reduced by an interstellar absorption factor of 0.06 because of extinction.
Nomenclature.
"λ Leonis" (Latinised to "Lambda Leonis") is the star's Bayer designation.
It bore the traditional name "Alterf", from the Arabic الطرف "aṭ-ṭarf" "the view (of the lion)". In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Alterf" for this star on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.
This star, along with Xi Cancri, were the Persian "Nahn", "the Nose", and the Coptic "Piautos", "the Eye", both lunar asterisms.
Properties.
This is a K-type giant star with a stellar classification of K4.5 III. It is a suspected variable star with a reported magnitude range of 4.28−4.34. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of nearly 45 times the radius of the Sun. It shines with around 472 times the luminosity of the Sun, from an outer atmosphere that has an effective temperature of 3,900 K.
References.
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EQ Pegasi

EQ Pegasi is a nearby binary system of two red dwarfs. Both components are flare stars, with spectral types of M4Ve and M6Ve respectively, and a current separation between the components of 5.8 arcseconds. The system is at a distance of 20.4 light-years, and is 950 million years old.
Discovery.
EQ Pegasi was first noticed to be a binary star by Carl A. Wirtanen who in the course of a systematic survey of the McCormick Observatory photographic plates for M-type dwarfs, detected a companion about two magnitudes fainter at a separation of 3.5 arcseconds.
Both components are also though to be single-lined spectroscopic binaries, with faint companions that have not been resolved in orbits of a few years.
In culture.
In 1998, it was the basis of a hoax, as a telecommunications company claimed it had discovered "alien" signals originating from the star.


Delta2 Canis Minoris

Delta2 Canis Minoris (δ2 CMi, δ2 Canis Minoris) is a main-sequence star in the constellation Canis Minor, about away.
Astronomic findings.
The star figures from our part of the galaxy as the more central of three that share the Delta designation (the greek-lettered catalog is that of Johann Bayer's 1603 "Uranometria" atlas of bright stars) in star atlases very close, southwest of Delta3 Canis Minoris which is physically unrelated. The Flamsteed designation for this star is 8 Canis Minoris in John Flamsteed's 1712 star catalog.
As of 2008, no companion has been suspected or found orbiting δ2 Canis Minoris. The apparent magnitude of 5.589 means it is deemed visible to the naked eye but faint and requires a dark sky to view. Based on parallax measurements it is calculated to be distant from the Earth.
This star is rotating rapidly; the projected rotational velocity is 117.6 km/s, which means that the equator of this star is rotating at this velocity or greater. By comparison, the Sun is a slow rotator with an equatorial azimuthal velocity of 2 km/s. δ2 Canis Minoris has a stellar classification of F2 V, indicating that this is an F-type main-sequence star that is generating energy at its core through thermonuclear fusion of hydrogen. The effective temperature of the photosphere is about 7053 K, giving it the yellow-white hue that is characteristic of F-type stars. The radius of this star can be estimated indirectly based upon the measured brightness and color information, which suggests the star is about 86% larger than the Sun.


NGC 6453

NGC 6453 is a globular cluster approximately 37,000 light-years away from Earth in the constellation of Scorpius.
The cluster is located approximately 1 kpc (~3,260 light-years) from the Galactic center, which results in confounded view of the cluster from the Solar System due to many intervening clouds of cosmic dust.
The cluster measures nearly 8' across, and its brightest stars are no brighter than 14th magnitude.
Observational history.
NGC 6453 was discovered by John Herschel on June 8, 1837, while he was observing from the Cape of Good Hope in South Africa. He included the cluster as "h 3708" in his 1864 Catalogue of Nebulae and Clusters of Stars, and Danish-Irish astronomer John Dreyer later added the cluster to his New General Catalogue as object number 6453. Dreyer described the cluster as "considerably large, irregularly round, pretty much brighter (in the) middle, round".


Gamma Geminorum

Gamma Geminorum (γ Geminorum, abbreviated Gamma Gem, γ Gem), formally named Alhena , is the third-brightest object in the constellation of Gemini. It has an apparent visual magnitude of 1.9, making it easily visible to the naked eye even in urban regions. Based upon parallax measurements with the Hipparcos satellite, it is located at a distance of roughly from the Sun.
Properties.
Alhena is an evolving star that is exhausting the supply of hydrogen at its core and has entered the subgiant stage. The spectrum matches a stellar classification of A0 IV. Compared to the Sun it has 2.8 times the mass and 3.3 times the radius. It is radiating around 123 times the luminosity of the Sun from its outer envelope at an effective temperature of 9,260 K. This gives it a white hue typical of an A-class star.
Alhena is a spectroscopic binary system with a period of 12.6 years (4,614.51 days) in a highly eccentric Keplerian orbit.
Etymology.
"γ Geminorum" (Latinised to "Gamma Geminorum") is the star's Bayer designation. The traditional name "Alhena" is derived from the Arabic الهنعة "Al Han'ah", 'the brand' (on the neck of the camel), whilst the alternate name "Almeisan" is from the Arabic المیسان "Al Maisan", 'the shining one.' "Al Hanʽah" was the name of star association consisting of this star, along with Mu Geminorum (Tejat Posterior), Nu Geminorum, Eta Geminorum (Tejat Prior) and Xi Geminorum (Alzirr). They also were associated in "Al Nuḥātai", the dual form of "Al Nuḥāt", 'a Camel's Hump'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Alhena" for this star.
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Nir al Henat", which was translated into Latin as "Prima του al Henat", meaning 'the brightest of Al Henat'.
In Chinese, (), meaning "Well (asterism)", refers to an asterism consisting of γ Geminorum, ε Geminorum, ζ Geminorum, λ Geminorum, μ Geminorum, ν Geminorum, ξ Geminorum and 36 Geminorum. Consequently, γ Geminorum itself is known as (, .)
In culture.
"Alhena" was the name of a Dutch ship that rescued many people from an Italian cruise liner, the "SS Principessa Mafalda", in October 1927. In addition, the American attack cargo ship was named after the star.


42 Librae

42 Librae is a single star located around 370 light years distant from the Sun in the southern zodiac constellation of Libra. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.97. This object is drifting closer to the Earth with a heliocentric radial velocity of −22 km/s.
This is an aging giant star with a stellar classification of K3-III CN2, where the suffix notation indicates this is a strong CN star with a high overabundance of cyanogen in its spectrum. Having exhausted the supply of hydrogen at its core, this star has expanded to 26 times the Sun's radius. Within the margin of error it has near-solar abundances of iron, suggesting a Sun–like metallicity. The star is radiating 214 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,332 K.


HD 240237

HD 240237 is a star in the northern constellation of Cassiopeia. It is an orange star that can be viewed with binoculars or a small telescope, but is too faint to be seen with the naked eye at an apparent visual magnitude of 8.19. This object is located at a distance of approximately 3,100 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of −25 km/s.
This is an aging giant star with a stellar classification of K2III; a star that has exhausted the supply of hydrogen at its core and expanded to 78 times the radius of the Sun. S. Gettel and associates (2011) estimate the star is around 270 million years old with 1.7 times the mass of the Sun. However, S. G. Sousa and associates found a much lower mass of 0.61 times the mass of the Sun. It is radiating 1,244 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,878 K.
Planetary system.
In 2011, Gettel et al. announced the discovery of a planet orbiting this star. They estimated a mass around 5 times that of Jupiter, with an orbital period of and a moderate eccentricity. Sousa et al. (2015) gave a much lower estimate of . The designation "b" for this object, derives from the order of discovery. The designation of "b" is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of HD 240237, there was only one planet, so only the letter "b" is used.


49 Persei

49 Persei is a star in the northern constellation of Perseus. It is just visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 6.09. Based upon parallax measurements, this star is located around away from the Sun, but is drifting closer with a radial velocity of −44 km/s. It has a relatively large proper motion, traversing the celestial sphere at a rate of ·yr−1.
This is an aging red giant star with a stellar classification of K1III, a star that has used up its core hydrogen and has expanding. It is a candidate horizontal branch star, which would indicate it is past the red giant branch stage and is fusing helium at its core. The star is nearly four billion years old with 1.4 times the mass of the Sun and 3.7 times the Sun's radius. It is radiating eight times the luminosity of the Sun from its photosphere at an effective temperature of 5,028 K.


QU Normae

QU Normae, also known as HR 6131, is a blue supergiant star in the constellation Norma. It is also a variable star, thought to be an α Cyg variable.
The apparent magnitude of QU Normae varies somewhat irregularly between 5.27 and 5.41. The General Catalogue of Variable Stars quotes a period of 4.818 days, but other research only shows likely periods longer than 10 days.
QU Normae has a spectral type B1.5 Ia, a luminous supergiant that has swollen and cooled off the main sequence. Surface abundances suggest that it has not yet passed through a red supergiant phase. Around 1,820 light-years distant, it shines with a luminosity approximately 417,000 times that of the Sun and has a diameter around 58 times that of the Sun.


NGC 2800

NGC 2800, also known as PGC 26302, is an elliptical galaxy in the constellation Ursa Major. It was discovered February 17, 1831 by William Herschel.


53 Persei

53 Persei is a single variable star in the northern constellation of Perseus. It has the Bayer designation d Persei, while "53 Persei" is the Flamsteed designation. The star is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.80. It is located approximately 480 light years away from the Sun, as determined from parallax, and is drifting further away with a radial velocity of +7.3 km/s.
This star has a stellar classification of B4IV, and was the prototype of a class of variable stars known as slowly pulsating B stars. It was one of the first mid-B type variable stars in the northern hemisphere to be studied. The star undergoes non-radial pulsations with a primary period of 2.36 days. Observation of the star with the BRITE satellite revealed eight separate frequencies in the star's light curve.
53 Persei is around 50 million years old with a projected rotational velocity of 15 km/s. It has six times the mass of the Sun and four times the Sun's radius. The star is radiating 780 times the luminosity of the Sun from its photosphere at an effective temperature of 16,720 K.


54 Leonis

54 Leonis is a binary star system in the zodiac constellation of Leo, located around 321 light years from the Sun. It is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 4.30. As of 2017, the pair had an angular separation of along a position angle of 113°. They have a physical separation of around .
The magnitude 4.477 primary, designated component A, is an A-type main-sequence star with a stellar classification of A0 V, which indicates it is generating energy through hydrogen fusion at its core. It has a high rate of spin, showing a projected rotational velocity of 185 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 8% larger than the polar radius. The star
is roughly 411 million years old with 2.4 times the mass of the Sun and about 2.88 times the Sun's radius.
The fainter magnitude 6.29 secondary, component B, is a smaller A-type main-sequence star with a class of A2 Vn. The 'n' suffix indicates wide "nebulous" lines due to rapid rotation. It is spinning with an even higher projected rotational velocity of 250 km/s. The star has about 2.59 times the Sun's radius.
Asteroid 729 Watsonia occulted HIP 53417 on March 3, 2013 at 01:48.


TT Aquilae

TT Aquilae (TT Aql) is a Classical Cepheid (δ Cep) variable star in the constellation Aquila.
The visual apparent magnitude of TT Aql ranges from 6.52 to 7.65 over 13.7546 days. The light curve is asymmetric, with the rise from minimum to maximum brightness only taking half the time of the fall from maximum to minimum.
TT Aql is a yellow-white supergiant around five thousand times brighter than the sun. It pulsates and varies in temperature between about 5,000 K and 6,000 K, and the spectral type varies between F6 and G5. The radius is at maximum brightness, varying between and as the star pulsates.
Cepheid masses can be estimated using Baade-Wesselink relations and this gives . The mass estimated by matching to evolutionary tracks is . The mass calculated by modelling the pulsations is . The discrepancies between the masses obtained by the different methods occurs for most Cepheid variables.


List of stars in Gemini

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


49 Librae

49 Librae is the Flamsteed designation for a binary star system in the Zodiac constellation of Libra. It has an apparent visual magnitude of 5.47, making it faintly visible to the naked eye from dark suburban skies as a dim, yellow-white hued star. The system is located 95 light years away from the Sun, based on parallax, but is drifting closer with a radial velocity of −20 km/s.
The variable nature of the velocity for 49 Librae was first noted by W. S. Adams in 1924. It is a single-lined spectroscopic binary with an orbital period of and an eccentricity of 0.11. The primary component has a stellar classification of F8 V or F9 V, indicating it is an F-type main-sequence star. It has an estimated 1.4 times the mass of the Sun, while the companion only has 0.4 solar masses. The system is a source for radio and X-ray emissions, which may be coming from the secondary companion.


NGC 6778

NGC 6778 is a planetary nebula (PNe) located about 10,300 light years away from the Sun in the equatorial constellation of Aquila. It is positioned 5° to the SSW of the prominent star Delta Aquilae. This nebula was discovered by German astronomer Albert Marth during the period 1863–1865. English astronomer John Herschel may have mistakenly catalogued it as NGC 6785, as nothing can be found now at those coordinates. In the New General Catalogue it was described as a "small, elongated, ill-defined disk".
This PNe displays a disrupted morphology, with a roughly S-shaped feature projecting out of an irregular shell, along with linear jet-like forms. The inner part contains a highly distorted elliptical ring oriented along an east-west direction. The nebula and ring have an angular size of and they are about 4,400 years old, while the jets are around 1,700 years old.
At the center of the nebula is a close binary star system with an orbital period of just 3.68 hours, one of the shortest known among the binary central stars that form a planetary nebulae. Their proximity to each other provides strong evidence that they have passed through a common-envelope (CE) phase earlier in their evolution. The pair may now consist of a primary star with , a red dwarf secondary companion having , and a semimajor axis of only .
The surrounding nebula is inclined about 85° to the line of sight from the Earth. The torus of this nebula is notable for its high expansion velocity, measured at up to 60–70 km/s. It displays collimated outflows, possibly as a result of the CE behavior of the central stars or else a short-lived accretion disk. The pair of jets are located along a position angle of 15°, showing fast outflow with radial velocities of around 100 km/s. The nebula is notable for the rich amount of filamentary "low-ionization structures", or LIS, resembling the wispy structures of nova explosions. These too may be the result of the CE interaction.
In addition to a higher than normal helium abundance, the nebula displays unusually strong optical recombination lines from heavier elements; one of the highest known among PNe. These may be the result of a very late thermal pulse, or "final flash", following the initial ejection of the stellar envelope that formed the nebula. The pulse would have ejected chemically-enriched material into the old nebula, changing its abundances.


A Tauri

The Bayer designation A Tauri is shared by two stars in the constellation Taurus:


V376 Carinae

V376 Carinae is a binary star system in the southern constellation of Carina. It has the Bayer designation b1 Carinae; "V376 Carinae" is the variable star designation. The system is visible to the naked eye as a faint point of light with a combined apparent magnitude of +4.69. The distance to this system from the Sun is approximately 650 light years based on parallax. It is drifting further away with a radial velocity of +27 km/s.
The magnitude 4.87 primary, designated component A, is a B-type main-sequence star with a stellar classification of B2V. During a search for Beta Cephei variables in the southern sky, it was initially classed as a very short period variable. However, this variability was not confirmed by subsequent observations. Samus et al. (2017) now suspect it is a constant star that was assigned a variable designation in haste. It has an estimated age of 12.5 million years with 7.8 times the mass of the Sun. The star is radiating nearly three thousand times the Sun's luminosity from its photosphere at an effective temperature of 21,150 K.
The companion star, component B, was discovered by Scottish astronomer James Dunlop in 1836. It has a class of B9.5V with an apparent magnitude of +6.58. As of 2010, the secondary had an angular separation of from the primary along a position angle of 76°.


Medusa Nebula

The Medusa Nebula is a planetary nebula in the constellation of Gemini. It is also known as Abell 21 and Sharpless 2-274. It was originally discovered in 1955 by University of California, Los Angeles astronomer George O. Abell, who classified it as an old planetary nebula. Until the early 1970s, the nebula was thought to be a supernova remnant. With the computation of expansion velocities and the thermal character of the radio emission, Soviet astronomers in 1971 concluded that it was most likely a planetary nebula. As the nebula is so large, its surface brightness is very low, with surface magnitudes of between +15.99 and +25 reported.


Tau Ceti f

Tau Ceti f is a super-Earth or mini-Neptune orbiting Tau Ceti that was discovered in 2012 by statistical analyses of the star's variations in radial velocity, based on data obtained using HIRES, AAPS, and HARPS. It is of interest because its orbit places it in Tau Ceti's extended habitable zone, but a 2015 study implies that there may not be a detectable biosignature because it has only been in the temperate zone for less than one billion years.
Characteristics.
Few properties of the planet are known other than its orbit and mass. It orbits Tau Ceti at a distance of 1.35 AU (near Mars's orbit in the Solar System) with an orbital period of 642 days, and has a minimum mass of 3.93 Earth masses. However, if it and its companion planets were similarly inclined to Tau Ceti's debris disk at °, f could and Earth masses, which means it's slightly more likely to be a mini-Neptune, although the exoplanet is included in the conservative sample of potentially habitable exoplanets. It is estimated to be 1.81 Earth radii.
Habitability.
As of October 2020, Tau Ceti f is considered the most potentially habitable exoplanet orbiting a Sun-like star. Its neighbor, Tau Ceti e, was previously regarded as a potentially habitable exoplanet in the conservative sample, but it was determined to likely be too hot to hold life, more similar to Venus. It and its companion may suffer from a continuous bombardment of asteroids, up to 10 times higher than in the Solar System, but a conjectured (super-)Jovian planet as outlined in a 2019 "Astronomy & Astrophysics" paper may be shepherding the disk, as it may be as close as 3 AU and as far away as 20.
With a flux of 0.32 the flux on Earth, Tau Ceti f has an estimated equilibrium temperature of only 190 Kelvin. If the conditions were the same as on the Earth, Tau Ceti f's average temperature would be around -50 °C. However, with a thicker atmosphere and a larger ocean, the temperature could be similar to Earth's.


TV Geminorum

TV Geminorum (TV Gem / HD 42475 / HR 2190) is a variable red supergiant in the constellation Gemini. Its visual magnitude varies from 6.3 to 7.5.
Location.
TV Gem is less than a degree SW of η Geminorum. It is a member of the Gemini OB1 stellar association at around 4,500 light years from Earth.
Variability.
TV Geminorum is classified as a semi-regular variable star, meaning that its brightness changes are not predictable, but do show some periodicity. The General Catalogue of Variable Stars does not list a period, but the International Variable Star Index gives an uncertain period of 229 days. A detailed study of TV Gem between 1997 and 2014 detects periods of 411 days and 3,137 days.
Properties.
TV Geminorum changes its size, temperature, and luminosity as its brightness varies. The temperature changes between 3,500 K and 3,850 K, the radius between and , and the bolometric luminosity between and . The majority of the electromagnetic radiation is emitted at wavelengths longer than the visual band, being only around 20,000 times brighter than the sun at visual wavelengths.
The pulsations are not correlated with the brightness changes in the expected way; other pulsating variables are brightest when they are hottest and smallest, but TV Gem does not follow this rule. It has been suggested that the luminosity variations are affected by the formation of supergranules surrounding the star. The spectral type varies in line with the temperature changes, from as early as K5.5 to as late as M1.3. The type M1.3 is assigned by a numerical calculation from photometry. The MK spectral class is M0 - M1.5 Iab.
If TV Gem was at the centre of the solar system, the four inner planets, including the Earth, would be encompassed within the star. It is losing mass at an annual rate of .
Companion.
TV Gem appears to have a very close hot companion. Its existence is inferred from an ultraviolet excess in the spectral energy distribution. The spectral type determined from the ultraviolet portion of the spectrum is B4, appearing to be a giant although it is thought that this is caused by the stellar wind from an underlying main sequence star. It is estimated to have an apparent magnitude of 11.2 and an absolute magnitude of −1.4.


NV Puppis

NV Puppis (NV Pup), also known as υ1 Puppis, is a class B2V (blue main-sequence) star in the constellation Puppis. Its apparent magnitude is 4.67 and it is approximately 800 light years away based on parallax.
It is a γ Cas variable, ranging from 4.78 to 4.58 magnitude. It is most likely an optical double with the nearby NW Puppis.
Neither component of this double is given a letter in Lacaille's catalogue or the British Association star catalogue. Gould gave them the designations (Latin letter) v1 and v2 Puppis, but these are rarely used. Lacaille applied the Greek letter υ to the star now called υ Carinae. The designation υ1 first appeared in several catalogues at the end of the 19th century.


HD 74772

HD 74772 (d Velorum) is a single star in the southern constellation of Vela. It is positioned near the Vela SNR, which gives it an intense X-ray background. The star is of apparent visual magnitude 4.05, and hence is visible to the naked eye. Based upon an annual parallax shift of , it is located 207 light years from the Sun. It is moving closer to the Earth with a heliocentric radial velocity of −2 km/s.
This is an evolved G-type giant star with a stellar classification of G6 III. The interferometry-measured angular diameter of this star is , which, at its estimated distance, equates to a physical radius of about 12 times the radius of the Sun. It has 3.2 times the mass of the Sun and is radiating 128 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,210 K.
References.
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NGC 4546

NGC 4546 is a lenticular field galaxy located in the direction of the constellation Virgo, with a total population of globular clusters estimated at about 390. Located 45.6 million light years away, with a stellar mass of about 27 billion solar masses, it has a declination of -03 ° 47 '35 "and an average rise of 12 hours, 35 minutes and 29.5 seconds. NGC 4546 was discovered on December 29, 1786 by William Herschel.
The galaxy appears to be home to a supermassive black hole with a mass of 256 million (± 16million) times the mass of the sun. It is estimated to have 390±60 globular clusters.
NGC 4546 appears to have at least 2 companions. NGC 4546-UCD1 and CGCG 014-074.


Nu Ophiuchi

Nu Ophiuchi (ν Oph, ν Ophiuchi) is a star in the equatorial constellation of Ophiuchus. The apparent visual magnitude is +3.3, making it one of the brighter members of this constellation. Based upon parallax measurements made during the Hipparcos mission, this star is located about from Earth.
Properties.
Nu Ophiuchi has about three times the mass of the Sun and is roughly 330 million years old. The spectrum of the star matches a stellar classification of K0 IIIa, indicating it is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence of stars. Unusually, it displays an anomalously low abundance of cyanogen for a star of its type. The star's outer envelope has expanded to around 14 times the Sun's radius and now radiates with a luminosity 123 times that of the Sun. This energy is emitted from its outer envelope at an effective temperature of 4,928 K, giving it the cool, orange hue of a K-type star.
Companions.
This is not a binary star system in the sense of having a gravitationally-bound stellar companion. However, in November 2003, a brown dwarf companion Nu Ophiuchi b was discovered. This sub-stellar companion has at least 21.9 times the mass of Jupiter and takes 536 days (1.47 years) to complete an orbit. A second brown dwarf companion was discovered in 2010, orbiting further from the star with a period of 3,169 days (8.68 years). These have been confirmed in 2012. Two brown dwarfs are locked in 1:6 orbital resonance.
This star is following an orbit through the galaxy that carries the star between from the Galactic Center. As a probable member of the Milky Way's thin disk population, it has a low orbital inclination that carries it no more than about above the galactic plane.
Naming.
This star is sometimes called by the name Sinistra, meaning "left side" in Latin, although authors like Jim Kaler recommend not using this name, and instead stick to the Bayer designation only (Nu Ophiuchi).
In China, the star is part of (), meaning "Left Wall of Heavenly Market Enclosure." The stars in this group include ν Ophiuchi, δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, ζ Aquilae, θ1 Serpentis, η Serpentis, ξ Serpentis and η Ophiuchi. Consequently, ν Ophiuchi itself is known as (, ), and together with ζ Capricorni represents the state Yan (燕) in the "Twelve States" constellation.


72 Pegasi

72 Pegasi is a binary star system in the northern constellation of Pegasus. It is visible to the naked eye as a faint, orange-hued point of light with a combined apparent visual magnitude of 4.97. The system is located approximately 550 light years away from the Sun, based on parallax, but is drifting closer with a radial velocity of −25 km/s.
This is a visual binary with an orbital period of roughly 492 years and an eccentricity of 0.32. The two stars are relatively similar and are about twice the mass of the Sun each. The primary star, 72 Pegasi A, is an evolved K-type giant with a visual magnitude of 5.67. The companion, 72 Pegasi B, is another K-type giant with an apparent magnitude of 6.11, and a separation of about from the primary. 72 Pegasi B is thought to be a binary itself, with a brown dwarf companion in a 4.2-year period.


WX Coronae Australis

WX Coronae Australis (WX CrA) is an R Coronae Borealis (R CrB) star in the constellation Corona Australis, one of the brightest examples of this extremely rare class of variable star. Despite the rarity, Corona Australis hosts another R CrB star, V Coronae Australis.
WX Coronae Australis is a luminous star with a large excess of carbon and very little hydrogen. It has the spectrum of a carbon star, of type R5 indicating that it shows strong carbon molecular bands but not as red overall as the majority of carbon stars. Its brightness is variable, with 78.9-day pulsations producing changes of about 0.1 magnitudes, as well as occasional deep fades by six or more magnitudes. This classifies it as an R Coronae Borealis variable. These stars are likely to have formed from the merger of two white dwarfs into a hydrogen-deficient carbon-rich hot supergiant that then cooled. The deep fades are caused by obscuration by carbon-rich dust condensing around the star.
WX Coronae Australis was first reported to be variable in 1928 after it was detected on two different photographic plates at magnitudes 12.2 and 16.0. It was catalogued as HV (Harvard Variable) 4119. The type of variability was not known at the time, but in 1936 its spectrum was measured as R5 and it was tentatively classified as an R CrB star. By 1996 it had been observed to fade 13 times at an average interval of 2,000 days.


NGC 992

NGC 992 is a spiral galaxy in the Aries constellation and is estimated to be 188 million light years from the Milky Way. NGC 992 was discovered by astronomers Lewis A. Swift on September 6, 1886.


33 Vulpeculae

33 Vulpeculae is a single star located around 500 light years away from the Sun in the northern constellation of Vulpecula. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.31. The object is drifting closer to the Earth with a heliocentric radial velocity of −25 km/s.
This is an evolved giant star with a stellar classification of K3.5 III, having exhausted the supply of hydrogen at it its core and expanded to 35 times the Sun's radius. It serves as a spectral standard for stars of its particular class. This star is radiating 334 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,070 K.


Psi Aurigae

The Bayer designation Psi Aurigae (ψ Aur, ψ Aurigae) is shared by nine star systems in the constellation Auriga and one in Lynx:
The Psi Aurigae stars mostly belonged to the now obsolete constellation Telescopium Herschelii, that is now part of Auriga.
Other names of the Psi Aurigae stars include:


Zeta Coronae Borealis

ζ Coronae Borealis , Latinised as Zeta Coronae Borealis, is the Bayer designation of a double star in the constellation Corona Borealis. The two components are separated by six arc-seconds and share the same Hipparcos catalogue number and Flamsteed designation. Each of the two is also a spectroscopic multiple system, with a total of five stars in the group.
Nomenclature.
ζ Coronae Borealis has the Flamsteed designation 7 Coronae Borealis and the Hipparcos catalogue number HIP 76669. As a double star, the brighter component is designated A (e.g. WDS J15394+3638 A) while the fainter of the two is designated B. The brighter star is also known as ζ2 Coronae Borealis and the fainter as ζ1 Coronae Borealis.
Each of the pair has its own Bright Star Catalogue and Henry Draper Catalogue numbers: HR 5833 and 5834, and HD 139891 and 139892 for ζ1 and ζ2 respectively.
System.
ζ1 Coronae Borealis is a single-lined spectroscopic binary, with an orbital period of about 9.5 days. The nature of the companion is unknown.
The brighter star, ζ2 Coronae Borealis, is a spectroscopic triple system, consisting of three massive stars. The inner pair orbit in 1.7 days, while the outer pair orbit in 251 days.


WASP-66

WASP-66, also known as TYC 7193-1804-1, is an F-type star in the constellation Antlia. It has an apparent magnitude of 11.6, which is much too faint to be seen with the unaided eye. The star is younger than Sun at billion years, and may be either metal-poor or similar to Sun in concentration of heavy elements.
According to survey published in 2017, WASP-66 has a one suspected companion - a red dwarf star with temperature 3330 K, at projected separation 6800 AU.
Planetary system.
In 2012, a superjovian planet around WASP-66 was discovered. WASP-66b has a mass that is about 2.3 times that of Jupiter. It takes just over 4 days to complete an orbit around its star, making it a typical hot Jupiter. The planet was discovered by the transit method – this is when a planet passes in front of a star, temporarily blocking some of the star's light.
The planetary orbit is well aligned with the equatorial plane of the star, misalignment angle been equal to −4°. The planet`s equilibrium temperature is 1790 K.


Pi Puppis

Pi Puppis, Latinized from π Puppis, also named Ahadi, is the second-brightest star in the southern constellation of Puppis. It has an apparent visual magnitude of 2.733, so it can be viewed with the naked eye at night. Parallax measurements yield an estimated distance of roughly from the Earth. This is a double star with a magnitude 6.86 companion at an angular separation of 0.72 arcsecond and a position angle of 148° from the brighter primary.
The spectrum of Pi Puppis matches a stellar classification of K3 Ib. The Ib luminosity class indicates this a lower luminosity supergiant star that has consumed the hydrogen fuel at its core, evolved away from the main sequence, and expanded to about 290 times the Sun's radius. The effective temperature of the star's outer envelope is approximately 4,000 K, which gives it the orange hue of a K-type star. It is a semiregular variable star that varies in apparent magnitude from a high of 2.70 down to 2.85. Pi Puppis is the brightest star in the open cluster Collinder 135.
Naming.
The star has the traditional name Ahadi, which is derived from Arabic for "having much promise". In Chinese, (), meaning "Bow and Arrow", refers to an asterism consisting of π Puppis, δ Canis Majoris, η Canis Majoris, HD 63032, HD 65456, ο Puppis, k Puppis, ε Canis Majoris and κ Canis Majoris. Consequently, π Puppis itself is known as (, .)


NGC 2865

NGC 2865 is an elliptical galaxy in the constellation Hydra.


WR 86

WR 86 is a visual binary in the constellation Scorpius consisting of a Wolf-Rayet star and a β Cephei variable. It lies 2° west of NGC 6357 on the edge of the Great Rift in the Milky Way in the tail of the Scorpion.
WR 86 is a binary with two components of equal visual brightness 0.3" apart. One has the emission-line spectrum of a WC7 Wolf-Rayet star, while the other is a B0 giant. The blue giant varies slightly in brightness every 3.5 hours. The WR star may also be slightly variable.
The pulsations of the B-type giant are characteristic of a β Cephei variable. Analysis of its pulsations and comparison to the expected properties of a WC7 star suggest that both stars could have evolved without mass exchange. The WR and B stars would have had initial masses of and respectively four million years ago.


Epsilon Corvi

Epsilon Corvi (ε Crv, ε Corvi) is a star in the southern constellation of Corvus. It has the traditional name Minkar , from Arabic منقار "minqar" meaning "beak [of the crow]" The apparent visual magnitude is +3.0 and it is located at a distance of from Earth.
In Chinese, (), meaning "Chariot (asterism)", refers to an asterism consisting of ε Corvi, γ Corvi, δ Corvi and β Corvi. Consequently, ε Corvi itself is known as (, .).
Epsilon Corvi is a red giant with a stellar classification of K2 III, having consumed the hydrogen at its core and evolved away from the main sequence. It has about three times the Sun's mass. The interferometry-measured angular diameter of this star is about 4.99 mas, which, at its estimated distance, equates to a physical radius of about 52 times the radius of the Sun. The effective temperature of the outer envelope is , giving it an orange hue that is characteristic of a K-type star. Around 4 times as massive as the Sun, it spent much of its life as a main sequence star of spectral type B5V.
References.
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Xi2 Capricorni

Xi2 Capricorni (ξ2 Capricorni) is a yellow-white hued star in the southern constellation of Capricornus. It is dimly visible to the naked eye on a dark night, having an apparent visual magnitude of +5.83. Based upon an annual parallax shift of 36.10 mas as seen from Earth, this system is located 90 light years from the Sun.
This is an F-type main-sequence star with a stellar classification of , where the suffix notation indicates the spectrum displays a mild underabundance of iron. It is around three billion years old with 1.2 times the mass of the Sun. Although considered a single star, there is reason to suspect it forms a wide physical pair with the visual magnitude 10.94 red dwarf star LP 754–50. They have a projected separation of , with LP 754–50 having an estimated 0.55 times the mass of the Sun. If they are gravitationally bound, their orbital period would be around 3.7 million years.


NGC 4457

NGC 4457 is an intermediate spiral galaxy located about 55 million light-years away in the constellation of Virgo. It is also classified as a LINER galaxy, a class of active galaxy defined by their spectral line emissions. NGC 4457 Is inclined by about 33°. It was discovered by astronomer William Herschel on February 23, 1784. Despite being listed in the Virgo Cluster Catalog as VCC 1145, NGC 4457 is a member of the Virgo II Groups which form an extension of the Virgo cluster.
NGC 4457 may have had a recent minor merger with another galaxy.
On July 1 2020, an astronomical transient was discovered in NGC 4457 by astronomer Kiochi Itagaki and confirmed by ASAS-SN. Spectroscopic classification determined the object to be a Type Ia Supernova, SN 2020nvb.
Physical characteristics.
NGC 4457 has a broad oval zone containing an inner spiral which is defined mainly by two fairly open arms. There is a well-defined outer ring that is completely detached from the inner regions of the galaxy.
Truncated disk.
NGC 4457 has a severely reduced amount of star-formation in its disk while its inner regions have a normalized rate of massive star formation. This may have been caused by a recent interaction of the gas in the galaxy with the gas in the surrounding Virgo Cluster, causing the gas to be stripped away in an effect known as ram-pressure stripping.


46 Cancri

46 Cancri is a star in the zodiac constellation of Cancer, located around 680 light years away from the Sun. It is a dim, yellow-hued star, near the lower limits of visibility to the naked eye with an apparent visual magnitude of 6.12. The star is moving closer to the Earth with a heliocentric radial velocity of –13.1 km/s. It has a stellar classification of G5 III, matching an aging giant star that has consumed the hydrogen at its core and evolved away from the main sequence.
46 Cancri is 740 million years old with 2.65 times the mass of the Sun. It has expanded to about 11 times the Sun's radius and is radiating 125.9 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,966 K.


Omega Draconis

Omega Draconis, Latinized from ω Draconis and also known as 28 Draconis, is a binary star in the constellation of Draco. The system is fairly close, and is located about 76 light-years (23 parsecs) away, based on its parallax.
Omega Draconis is a spectroscopic binary, which means the two stellar components are too close to be resolved but periodic Doppler shifts in their spectra indicate orbital motion. In this case, light from both stars can be detected, and it is a double-lined spectroscopic binary. The orbital period of the system is 5.28 days, and the eccentricity of the system is 0.00220, implying a nearly circular orbit. The primary has a mass of , and is an F-type main-sequence star. The secondary is less massive, at .
Naming.
With 27 Draconis, it composed the Arabs' الأظفار الذئب "al-ʼaẓfār al-dhiʼb", "the hyena's claws" in the asterism of the Mother Camels. The two stars have been distinguished as "Adfar Aldib I" (ω) and "Adfar Aldib II" (27 Draconis).
In Chinese, (), meaning "Royal Secretary", refers to an asterism consisting of ω Draconis, 15 Draconis, 18 Draconis and 19 Draconis. Consequently, ω Draconis itself is known as (, .).


Andromeda IV

Andromeda IV (And IV) is an isolated irregular dwarf galaxy. The moderate surface brightness, a very blue color, low current star formation rate and low metallicity are consistent with it being a small (background) dwarf irregular galaxy, perhaps similar to Local Group dwarfs such as IC 1613 and Sextans A. Arguments based on the observed radial velocity and the tentative detection of the RGB tip suggest that it lies well outside the confines of the Local Group.
Further study using the Hubble Space Telescope has shown it to be a solitary irregular dwarf galaxy. The galaxy is between 22 and 24 million light years from Earth, and so is not close to the Andromeda Galaxy at all. The galaxy is severely isolated. The Holmberg diameter is 1880 parsecs, but neutral atomic hydrogen gas extends more than eight times further out in a disk. The galaxy is very dark, and the baryonic mass to dark matter ratio is 0.11.
History.
It was discovered by Sidney van den Bergh in 1972.


Kepler-35

Kepler-35 is a binary star system in the constellation of Cygnus. These stars, called Kepler-35A and Kepler-35B have masses of 89% and 81% solar masses respectively, and both are assumed to be of spectral class G. They are separated by 0.176 AU, and complete an eccentric orbit around a common center of mass every 20.73 days.
Description.
The Kepler-35 system consists of two stars slightly less massive than the sun in a 21-day orbit aligned edge-on to us so that the stars eclipse each other. The orbit has a semi-major axis and a mild eccentricity of 0.16. of The precise measurements made by the Kepler satellite allow doppler beaming to be detected, as well as brightness variations due to the ellipsoidal shape of the stars and reflections of one star on the other.
The primary star has a mass of and a radius fractionally larger than the sun. With an effective temperature of , its luminosity is . The secondary star has a mass of , a radius of , an effective surface temperature of , and a bolometric luminosity of .
Planetary system.
Kepler-35b is a gas giant that orbits the two stars in the Kepler-35 system. The planet is over an eighth of Jupiter's mass and has a radius of 0.728 Jupiter radii. The planet completes a somewhat eccentric orbit every 131.458 days from a semimajor axis of just over 0.6 AU, only about 3.5 times the semi-major axis between the parent stars. The proximity and eccentricity of the binary star as well as both stars have similar masses results the planet's orbit to significantly deviate from Keplerian orbit. Studies have suggested that this planet must have been formed outside its current orbit and migrated inwards later. The eccentricity of planetary orbit is acquired on the last stage of migration, due to interaction with the residual debris disk.
Numerical simulation of formation of planetary system Kepler-35 has shown the formation of additional rocky planets in the habitable zone is highly likely, and these planetary orbits are stable.


Beta Canum Venaticorum

Beta Canum Venaticorum (β Canum Venaticorum, abbreviated Beta CVn, β CVn), also named Chara , is a G-type main-sequence star in the northern constellation of Canes Venatici. At an apparent visual magnitude of 4.26, it is the second-brightest star in the constellation. Based upon an annual parallax shift of 118.49 mas, this star is distant from the Sun.
Along with the brighter star Cor Caroli, the pair form the "southern dog" in this constellation that represents hunting dogs.
Nomenclature.
"β Canum Venaticorum" (Latinised to "Beta Canum Venaticorum") is the star's Bayer designation.
The traditional name "Chara" was originally applied to the "southern dog", but it later became used specifically to refer to Beta Canum Venaticorum. Chara "(χαρά)" means 'joy' in Greek. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Chara" for this star.
In Chinese, (), meaning "Imperial Guards", refers to an asterism consisting of Beta Canum Venaticorum, Alpha Canum Venaticorum, 10 Canum Venaticorum, 6 Canum Venaticorum, 2 Canum Venaticorum, and 67 Ursae Majoris. Consequently, the Chinese name for Beta Canum Venaticorum itself is (, .)
Observations.
Beta CVn has a stellar classification of G0 V, and so is a G-type main-sequence star. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. The spectrum of this star shows a very weak emission line of singly ionized calcium (Ca II) from the chromosphere, making it a useful reference star for a reference spectrum to compare with other stars in a similar spectral category. (The Ca-II emission lines are readily accessible and can be used to measure the level of activity in a star's chromosphere.)
Beta CVn is considered to be slightly metal-poor, which means it has a somewhat lower portion of elements heavier than helium when compared to the Sun. In terms of mass, age and evolutionary status, however, this star is very similar to the Sun. As a result, it has been called a solar analog. It is about 3% more massive than the Sun, with a radius 12% larger than the Sun's and 15% greater luminosity.
The components of this star's space velocity are = . In the past it was suggested that it may be a spectroscopic binary. However, further analysis of the data does not seem to bear that out. In addition, a 2005 search for a brown dwarf in orbit around this star failed to discover any such companion, at least down to the sensitivity limit of the instrument used.
Habitability.
In 2006, astronomer Margaret Turnbull labeled Beta CVn as the top stellar system candidate to search for extraterrestrial life forms. Because of its solar-type properties, astrobiologists have listed it among the most astrobiologically interesting stars within 10 parsecs of the Sun. However, as of 2009, this star is not known to host planets.


Gamma Scuti

Gamma Scuti, Latinized from γ Scuti, is a single, white-hued star in the southern constellation of Scutum. The apparent visual magnitude of 4.67 indicates this is a dim star but visible to the naked eye. Based upon an annual parallax shift of 10.21 mas as seen from Earth, this star is located about 319 light years from the Sun. Currently it is moving towards the Solar System at 41 km/s, which means in 2.35 million years it will pass at just distance, probably becoming the brightest star in the night sky, at magnitude −2.1, for a period.
This is an A-type main-sequence star with a stellar classification of A2:V. At the age of 237 million years, it is spinning rapidly with a projected rotational velocity of 222 km/s. This is giving the star an oblate shape with a prominent equatorial bulge that is estimated to be 21% larger than the polar radius. The star has an estimated 2.91 times the mass of the Sun and 4.1 times the Sun's radius. It is radiating 150 times the Sun's luminosity from its photosphere at an effective temperature of 9,016 K.


Tau5 Eridani

Tau5 Eridani, Latinized from τ5 Eridani, is a binary star system in the constellation Eridanus. It is visible to the naked eye with a combined apparent visual magnitude of 4.26. The distance to this system, as estimated using the parallax technique, is around 293 light years.
Tau5 Eridani is a double-lined spectroscopic binary system. The two stars orbit each other closely with a period of 6.2 days and an eccentricity of 0.2. On average, the two stars are separated by around 0.183 AU.
The primary component is a B-type main sequence star with a stellar classification of B0 V. It is around 157 million years old and is spinning with a projected rotational velocity of 55 km/s. The star has around 3.3 times the mass of the Sun and 3.2 times the Sun's radius. It radiates 188 times the solar luminosity from an outer atmosphere at an effective temperature of 12,514 K.
The secondary component has a stellar classification of B9 V. It is slightly smaller, with an estimated size equal to 2.6 times the radius of the Sun.
Although τ5 Eridani has no bright visual companion stars, the galaxy IC 1953 is less than 10' away. It is one of the brighter members of a loose group of galaxies called the Eridanus Group scattered around the components of τ Eridani.


HD 63399

HD 63399 is an orange giant star located approximately 445 light years away, in the constellation Puppis. Its apparent magnitude is 6.46.


NGC 447

NGC 447 is a spiral galaxy of type (R)SB(rs)0/a located in the constellation Pisces. It was first discovered on October 8, 1861 by Heinrich d'Arrest (and later listed as NGC 447); it was also seen in the 1890s by Edward Emerson Barnard (and later listed as IC 1656). It was described by Dreyer as "faint, pretty large, brighter middle, 11th magnitude star to northeast."


NGC 7030

NGC 7030 is a barred spiral galaxy located about 380 million light-years away in the constellation Capricornus. NGC 7030 has an estimated diameter of 133,510 light-years. NGC 7030 was discovered by astronomer Francis Preserved Leavenworth on September 3, 1885.


NGC 2328

NGC 2328 is a low-luminosity, early-type (lenticular) galaxy. It is located in the Puppis constellation. NGC 2328 is its New General Catalogue designation. It is located about 59 million light-years (18 Megaparsecs) away from the Sun.
NGC 2328 was imaged by the Hubble Space Telescope, revealing a ring of star clusters near the center of the galaxy. These star clusters are massive, and are consequently quite young as well.


35 Cancri

35 Cancri is a star in the zodiac constellation of Cancer, located 630 light years from the Sun. It is a challenge to view with the naked eye even under good seeing conditions, having an apparent visual magnitude of +6.55. The star is moving further from the Earth with a heliocentric radial velocity of +35 km/s, and is a member of the Beehive Cluster.
This is a subgiant star with a stellar classification of G0 III. It is rotating at a relatively fast clip, giving it an oblate shape with an equatorial bulge that is 5% larger than the polar radius. 35 Cancri has a projected rotational velocity of 99 km/s and a rotation period of 0.5 days. This rotation is expected to decrease significantly as the star expands into a giant. It has nearly the same mass and size as the Sun, but is radiating 77 times the Sun's luminosity from its photosphere at an effective temperature of 5,950 K.


Iota Fornacis

The Bayer designation ι Fornacis (Iota Fornacis, ι For) is shared by two stars in the constellation Fornax:


EQ Virginis

EQ Virginis is a flare star in the constellation of Virgo. It is an orange dwarf of spectral type K5Ve and is a member of the IC 2391 moving group. The moving group of stars is between 30 and 50 million years old.


NGC 938

NGC 938 is an elliptical galaxy located in the constellation Aries, approximately 184 million light years from the Milky Way. It was discovered by the Prussian astronomer Heinrich d'Arrest in 1863.
SN 2015ab, a type Ia supernova, occurred within NGC 938.


Chi Sagittarii

The Bayer designation Chi Sagittarii (χ Sagittarii) is shared by three star systems in the zodiac constellation of Sagittarius. The brightest of these, χ1 Sagittarii and χ3 Sagittarii, are separated by 0.56° on the sky. The dimmer star χ2 Sagittarii is located between them, 0.10° from χ1, and is too faint to be seen with the naked eye. In 1977, the Wow! signal came from the direction of these stars.
Name and etymology.
These three χ star, together with φ Sgr, σ Sgr, ζ Sgr and τ Sgr were "Al Naʽām al Ṣādirah" (النعم السادرة), the Returning Ostriches. According to the catalogue of stars in the "Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars", "Al Naʽām al Ṣādirah" or "Namalsadirah" was originally the title for four stars: φ Sgr as "Namalsadirah I", τ Sgr as "Namalsadirah II", χ1 Sgr as "Namalsadirah III" and χ2 Sgr as "Namalsadirah IV" (except σ Sgr and ζ Sgr). In Chinese, (), meaning "Dog", refers to an asterism consisting of χ1 Sagittarii and 52 Sagittarii. Consequently, χ1 Sagittarii itself is known as (, .)


NGC 7723

NGC 7723 is a barred spiral galaxy located in the constellation Aquarius. It is located at a distance of circa 90 million light years from Earth, which, given its apparent dimensions, means that NGC 7723 is about 95,000 light years across. It was discovered by William Herschel on November 27, 1785. The galaxy is included in the Herschel 400 Catalogue. It lies 1.5 degrees north-northwest from Omega1 Aquarii. It can be seen with a 4-inch telescope under dark skies.
Characteristics.
NGC 7723 is a barred spiral galaxy. It has a bright nucleus and a boxy bulge. In the centre of the galaxy lies a supermassive black hole whose mass is estimated to be based on the spiral arm pitch angle. The bar emerges from the opposite sides of the bulge. Straight dust lanes are observed along the bar, the one smooth and the other appearing broken. The bar has a maximum apparent length 64 arcseconds. At the end of the bar the spiral arms form a pseudoring with diameter of 71 arcseconds. Based on observations in far ultraviolet (FUV) and Hα there is active star formation at the pseudoring. Based on the B-I color profile of the galaxy the bar finishes at 23 arcseconds, at the same distance where there is a population of older stars, and thus is suggested to be the corotation radius of NGC 7723.
The structure of the arms is complex. The arm that emanates from the southwest part of the bar is well defined for a quarter of a revolution and after that it becomes more diffuse and fades after reaching half a revolution. The other arm emanates from a feature about 60 degrees northwest of the bar and brightens after passing the end of the bar, and then it splits in two. The inner part forms the southwest part of the pseudoring and bifurcates after winding for about 120 degrees after the bar end, with the inner part being the brightest. The other arm becomes diffuse and of low surface brightness.
One supernova has been observed in NGC 7723, SN 1975N, a type Ia supernova with peak magnitude of 13.8.
Nearby galaxies.
NGC 7723 belongs to a small groups of galaxies known as the NGC 7727 group. Other members of the group include NGC 7727 and NGC 7724. NGC 7727 lies about 40' northwest of NGC 7723.


SZ Crateris

SZ Crateris is a binary star system in the southern constellation Crater. Both components belong to the main sequence: the primary star has a spectral classification of K5V while the secondary is a red dwarf of spectral class M0V. The radius of the primary is about 66% the radius of the Sun, while the secondary member is only about 42% of the solar radius. In 1994, the two stars were separated by 5.1 arc seconds, which is equivalent to 112.41 astronomical units.
SZ Crateris is classified as a marginal BY Draconis variable, and has an optical variability cycle of 11.58 days. (The star causing the variability is unspecified.) Compared to the Sun, SZ Crateris has a slightly higher proportion of elements other than hydrogen and helium. Based upon gyrochronology, the estimated age of this star is under 200 million years.
The SZ Crateris system is a member of the Ursa Major moving group of stars that have similar motions through space. The space velocity components of this system are U = , V = and W = . It is on an orbit through the Milky Way that has an orbital eccentricity of 0.092, which will bring it as close as to the galactic core, and as distant as . The inclination of the orbit carries the system as much as from the plane of the galactic disk.


HD 224693 b

HD 224693 b is an extrasolar planet orbiting the star HD 224693 every 27 days with a minimum mass 70% of Jupiter.
The planet HD 224693 b is named Xólotl. The name was selected in the NameExoWorlds campaign by Mexico, during the 100th anniversary of the IAU. Xólotl means animal in the native Nahuatl language and was an Aztec deity associated with the evening star (Venus).


A Centauri (disambiguation)

The Bayer designations A Centauri and a Centauri represent different stars. Due to technical limitations, both designations link here.


NGC 7034

NGC 7034 is an elliptical galaxy located about 380 million light-years away in the constellation of Pegasus. It is part of a pair of galaxies that contains the nearby galaxy NGC 7033. NGC 7034 was discovered by astronomer Albert Marth on September 17, 1863.


Eta Corvi

Eta Corvi (Eta Crv, η Corvi, η Crv) is an F-type main-sequence star, the sixth-brightest star in the constellation of Corvus. Two debris disks have been detected orbiting this star, one at ~150 AU, and a warmer one within a few astronomical units (AU).
Properties.
Eta Corvi is only about 30% of the Sun's age. The concentration of iron and other heavy elements in its atmosphere is only about 93% that of the Sun's. The projected rotational velocity at the star's equator ("v" sin "i") is 68 km/s - more than 30 times faster than that for the Sun. A yellow-white main sequence star of spectral type F2V, it has an estimated surface temperature of 6950 K. It is 1.52 times as massive as the Sun and is 4.87 times as luminous. It is 59 light-years distant from the Solar System.
The IRAS satellite detected an excess of infrared radiation from this star, beyond what would normally be expected for a stellar object of this class. Observations in the submillimetre band confirmed the presence of excess dust in orbit around the star having about 60% of the mass of the Moon and a temperature of 80 K. The data indicated a debris disk with an estimated maximum radius of 180 AU from the star, or 180 times the separation of Earth and the Sun. (Compare with the Kuiper belt, which extends out to 55 AU from the Sun.)
Recent submillimeter observations confirm the presence of an outer flat, circumstellar disk of debris with an outer radius of 150 AU. It is oriented at an inclination to the line of sight from the Earth. Most of the inner 100 AU of the disk is relatively free of material, which suggests it was cleared away by a planetary system. In addition, infrared radiation which appears to be from an inner, hotter, debris disk within 3.5 AU of the star has been observed.
Since the Poynting–Robertson effect would cause the dust in the outer disk to spiral in to the star within 20 million years, much younger than the age of the system, the observed presence of dust in the outer disk means that it must be constantly replenished. It is thought that this happens by the collisions of planetesimals orbiting at a distance of about 150 AU, which are repeatedly broken down into smaller and smaller pieces, eventually becoming dust. The origin of the inner disk is not clear. It may have originated from planetesimals recently having moved from the outer regions of the system into the inner system, in a process similar to the Late Heavy Bombardment in the history of the Solar System, and subsequently being ground to dust by collisions.
Possible Late Heavy Bombardment.
In 2010–2011, Carey Lisse of the Johns Hopkins University Applied Physics Laboratory and his group analyzed the Spitzer IRS 5–35 μm spectrum of the warm, ~360K circumstellar dust and found that it showed clear evidence for warm, water- and carbon-rich dust at ~3 AU from the central star, in the system's habitable zone, uncoupled and in a separate reservoir from the system's extended sub-mm dust ring at 150 ± 20 AU. Spectral features similar in kind and amplitude to those found for ultra-primitive (i.e., formed very early in the lifetime of the Eta Corvi system) ~10 Myr old cometary material were found (water ice and gas, olivines and pyroxenes, amorphous carbon and metal sulfides), in addition to emissions due to impact produced silica and high temperature/pressure carbonaceous phases. The warm dust is very primitive, and definitely not from an asteroidal parent body. A large amount, at least 3 x 1019 kg, of 0.1 – 1000 μm warm dust is present, in a roughly collisional equilibrium distribution with dn/da ~ a−3.5. This is the equivalent of a 160-kilometer-radius centaur or medium-sized Kuiper belt object of 1.0 g cm−3 density or a "comet" of 260 km radius and 0.40 g cm−3 density. The warm dust mass is much larger than that of a solar system comet (1012 – 1015 kg), but is very similar to the mass of a Kuiper belt object (1019 – 1021 kg). The amount of water tied up in the observed material, ~1019 kg, is > 0.1% of the water in the Earth's oceans, and the amount of carbon is also considerable, ~1018 kg.
The team found that the best model for what is going on is that some process (e.g., planetary migration) is dynamically exciting the Eta Corvi-equivalent of the Solar System's Kuiper belt (KB), causing frequent collisions amongst Kuiper belt objects (KBOs) and producing the observed copious Kuiper belt dust. As part of this process, one or more of the excited KBOs was scattered onto an orbit that sent it into the inner system, where it collided with a planetary-class body at ~3 AU, releasing a large amount of thermally unprocessed, primitive ice and carbon-rich dust. Their analysis suggests that the system is likely a good analogue for the Late Heavy Bombardment (LHB) processes that occurred in the early Solar System at 0.6–0.8 Gyr after the formation of the calcium–aluminium-rich inclusions (minerals such as olivines that are among the first solids condensed from the cooling protoplanetary disk) and is thus worthy of further detailed study in order to understand the nature of the LHB. It is also a good system to perform a search for a rocky planetary body at ~3 AU (the impacted planet), and for a giant planet at ~115 AU (the Kuiper belt dynamical stirrer at ~ the 3:2 resonance of the Kuiper belt dust at 150 AU).
Name.
In Chinese astronomy, Eta Corvi is called 左轄, Pinyin: Zuǒxiá, meaning "Left Linchpin", because this star is marking itself and stands alone in the "Left Linchpin" asterism, Chariot mansion (see : Chinese constellation). 左轄 (Zuǒxiá), westernized into Tso Hea, but the name "Tso Hea" was already designated for β Corvi (Kraz) by R.H. Allen.


Epsilon Ursae Minoris

Epsilon Ursae Minoris (ε Ursae Minoris) is a binary star system in the northern circumpolar constellation of Ursa Minor. It is visible to the naked eye with a combined apparent visual magnitude of 4.19. Based upon an annual parallax shift of 10.73 mas as seen from the Earth, it is located around 300 light years from the Sun. The pair are drawing nearer to the Sun with a radial velocity of −10.57 km/s.
This system forms a detached, single-lined spectroscopic binary with an orbital period of 39.5 days and a low eccentricity of 0.04. Its binary nature was discovered in 1899 by American astronomer W. W. Campbell and the first orbital determination was made in 1910 by Canadian astronomer J. S. Plaskett. The orbital plane is nearly aligned with the line of sight to the Earth, so the pair forms an eclipsing binary. The primary eclipse has a minimum of 4.23 in magnitude, while the secondary minimum is magnitude 4.21. This eclipsing behavior was discovered by German astronomer P. Guthnick using observations between 1946 and 1947.
The primary is an evolved G-type giant star with a stellar classification of G5 III. The secondary is a main sequence star with a class in the range A8-F0 V. One of the pair is an active RS Canum Venaticorum type variable star, which is causing the net brightness to vary with a period that matches the orbital period of the binary. The primary has a high projected rotational velocity of 25.6 km/s, which is likely the result of synchronization effects from tidal interaction with the secondary.
Epsilon Ursae Minoris has a visual companion: a magnitude 12.32 star at an angular separation of 77.0 arc seconds along a position angle of 2°, as of 2014.


Beta Sextantis

Beta Sextantis, Latinized from β Sextantis, is a variable star in the equatorial constellation of Sextans. With an apparent visual magnitude of 5.07, it is faintly visible to the naked eye on a dark night. According to the Bortle scale, it can be viewed from brighter lit suburban skies. The distance to this star, based upon an annual parallax shift of 8.06 mas, is around 400 light years.
This star served as a primary standard in the MK spectral classification system with a stellar classification of B6 V, indicating that it is a B-type main sequence star. However, Houk and Swift (1999) list a classification of B5 IV/V, suggesting it may be transitioning into a subgiant star. It has served as a "uvby" photometric standard, but is also categorized as an Alpha2 Canum Venaticorum variable with a suspected period of 15.4 days. This lengthy a period conflicts with a relatively high projected rotational velocity of 85 km/s, leaving the explanation for the variance unresolved.


NGC 6200

NGC 6200 is an open cluster in the constellation Ara, lying close to the galactic equator. It contains one β Cephei variable.


Nu Pegasi

ν Pegasi, Latinized as Nu Pegasi is a single star in the northern constellation of Pegasus. It is an orange-hued star that is faintly visible to the naked eye with an apparent visual magnitude of 4.84. The star is located approximately away based on parallax, but is drifting closer with a radial velocity of .
This is an aging giant star, most likely (94% chance) on the red giant branch, with a stellar classification of K4III. It is a suspected variable, with a magnitude range observed from 4.83 to 4.86. With the supply of hydrogen at its core exhausted, the star has cooled and expanded to 24.6 times the Sun's radius. It is 13% more massive than the Sun and is radiating 149 times the Sun's luminosity from its swollen photosphere at an effective temperature of .


NGC 6565

NGC 6565, also known as ESO 456-70, is a planetary nebula 14,000 light-years away, formed when a star ejected its outer layers during the late stages of its evolution.. It is about 13th magnitude and has a diameter of 8 to 10 arcseconds. It is located in the constellation Sagittarius.


NGC 739

NGC 739 is a spiral galaxy approximately 193 million light-years away from Earth in the constellation of Triangulum.
Observational history.
NGC 739 was discovered by English astronomer Ralph Copeland on January 9, 1874. He was using the 72" telescope at Birr Castle in an observation of Arp 166, which is composed of two interacting galaxies NGC 750 and NGC 751.
Copeland reported the wrong direction of the newly observed galaxy, but gave the correct orientation as PA 292° (WNW) and separation 524" (8.7'). Because of his error the derived position was in error and this was copied into the NGC Catalogue.
In 1913 American astronomer Heber Curtis noted there was nothing at that position and suggested MCG +05-05-030 was in fact NGC 739, based on Edward Crossley's photographs taken at Lick Observatory.


Theta Geminorum

Theta Geminorum (θ Gem, θ Geminorum) is a single star in the northern zodiac constellation of Gemini. It is visual to the naked eye with an apparent visual magnitude of 3.59. Based upon an annual parallax shift of 17.25 mas, it is about 189 light years distant from the Sun.
This is an evolving A-type subgiant star with a stellar classification of A2 IV. It has 1.80 times the mass of the Sun and radiates 93 times the solar luminosity. The measured angular diameter is . At an estimated distance of this star, this yields a physical size of about 5.1 times the radius of the Sun. It is around 252 million years old and has a projected rotational velocity of 133 km/s. This rotation rate is giving the star an oblate shape, with an equatorial bulge that is 11% larger than the polar radius.
The "Washington Visual Double Star Catalog" lists five visual companions within 100″; the closest and brightest such companion is the magnitude 8.6 θ Geminorum E at an angular separation of 2.4″ along a position angle of 295°, as of 2010.
References.
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