Rho Leonis

Rho Leonis (ρ Leo) is a binary star in the zodiac constellation of Leo, and, like the prominent nearby star Regulus, is near the ecliptic. With an apparent visual magnitude of 3.9, this star can be readily seen with the naked eye. Parallax measurements give a distance estimate of about from the Earth.
This is an enormous star with about 21 times the Sun's mass () and 37 times the Sun's radius. Its spectrum matches a stellar classification of B1 Iab, with the 'Iab' luminosity class indicating that it is in the supergiant stage of its evolution. Rho Leonis is radiating about 295,000 times the Sun's luminosity at an effective temperature of 24,200 K, giving it the blue-white hue typical of a B-type star. A strong stellar wind is expelling mass from the outer envelope at a rate of per year, or the equivalent of 1 every 2.8 million years. The rotation rate is probably about once per 7 days, with an upper limit of 47 days.
Rho Leonis is classified as a runaway star, which means it has a peculiar velocity of at least 30 km s−1 relative to the surrounding stars. It has radial velocity of away from the Sun and a proper motion that is carrying it about 1.56 Astronomical Units per year, equivalent to 7 km s−1, in a transverse direction. The star is situated about above the galactic plane.
Rho Leo is 0.15 degree north of the ecliptic, so it can be occulted by the moon. Unusual light variation during these occultations has been explained as the result of a possible close companion. The companion would be just over one magnitude fainter and separated by 0.01 arcsec. The companion has not been detected by any other means although it should be easily detected with modern observations.


HD 98800

HD 98800, also catalogued as TV Crateris (TV Crt), is a quadruple star system in the constellation of Crater (the cup). Parallax measurements made by the Hipparcos spacecraft put it at a distance of about 150 light-years (45 parsecs) away, but this value is in high error. The system is located within the TW Hydrae association (TWA), and has received the designation TWA 4.
The system consists of HD 98800 A and HD 98800 B each of which contains two stars. In 2007, a debris disk was discovered orbiting HD 98800 B consisting of two rings which indicates there may be an extrasolar planet orbiting within a distance of 1.5 to 2 astronomical units.
Stellar system.
The system is a member of the TW Hydrae association, a group of young stars. Its membership was derived from the fact that its proper motion is similar to other stars in the group. The system itself is estimated to be around 7-10 million years old.
HD 98800 is a quadruple system, with two pairs of stars orbiting each other. The two pairs are separated by over an arcsecond, so the wide visual orbit is poorly known. A preliminary range of orbits has been calculated, with an orbital period of 300 to 430 years, as well as a moderate eccentricity of 0.3 to 0.6.
The primary component, HD 98800 A, is a K-type main-sequence star with a varying radial velocity. This indicates the presence of another star orbiting it, but light from that star cannot be detected, so the system is a single-lined spectroscopic binary. The secondary system, HD 98800 B, is another spectroscopic binary, but double-lined since both stars (another K-type star and a red dwarf) can be directly detected. The stars in the HD 98800 are much larger than would be expected from their masses: at such a young age, these stars have not condensed into their normal size yet.
Variability.
The brightness of HD 98800 varies slightly between magnitudes 8.91 and 8.98, and it has been given the variable star designation TV Crateris. The designation TV Crateris includes all four stars and it appears that both components A and B are variable. Component A varies with a period of 2.521 days which is thought to be its rotation period and it is classified as an RS Canum Venaticorum variable, a dwarf star with an uneven surface brightness that changes brightness as it rotates. Component B is thought to be a T Tauri star, a pre-main-sequence star surrounded by a disk. It has been speculated that it is actually a post-T Tauri star and that the variations are caused by irregularities in the tilted disk intercepting the light from the star.
Planetary system.
Debris disk.
An infrared excess indicative of a debris disk was first discovered by IRAS. Further observations of the system have been made using Keck and the Spitzer Space Telescope. The disk consists of two separate belts. The inner ring extends from a distance of 1.5 to 2 astronomical units from the barycenter of the central binary. The outer ring begins at approximately 5.9 astronomical units from the central binary, and extends out an undetermined distance. The gap between the two rings is ~3 astronomical units. The inner ring is thin, while the inner portion of the outer ring is dense.
Dr. Elise Furlan, leader of the Spitzer team that imaged this disk, concludes that the dust generated from the collision of rocky objects in the outer belt should eventually migrate toward the inner disk. But because the system is a double binary system, the dust particles do not evenly fill out the inner disk as expected.
The disk was imaged with ALMA and the high resolution image showed that the disk is likely misaligned with the orbit of the inner binary. The long period of the orbiting inner binary could be responsible for this misalignment and any circumbinary planet forming in this disk would be misaligned with the orbit of the inner binary. Based on VLA observations the disk extends from 3 to 5 astronomical units. The disk is more similar to a massive gas-rich protoplanetary disks than to a debris disks, which is unusual for this kind of age of a circumbinary disk.
Possible planets.
Debris disks are thought to constitute a phase in planetary formation. Because of the gap within the debris disk, the possibility of a planet within the system becomes even more likely. The detected gap could be caused by a unique gravitational relationship between the disk and a possible planet already begun to form, carving out a clear space in the disk. However, the gap could also be gravitational resonance effects of the four stars.


VV Orionis

VV Orionis is an eclipsing binary located in the belt region of the constellation Orion. It is a faint naked eye star.
The brightness of VV Orionis dips regularly every 18 hours. The peak visual magnitude is 5.3, which varies slowly in between the dips. The minimum brightness of the dips alternates between magnitude 5.55 and 5.66. The deep minima have a somewhat rounded bottom, while the less deep minima have flat bottoms with a constant magnitude for several hours. However, there are also additional cycles in the lightcurve that suggest that at least one of the stars is pulsating.
The VV Orionis system contains two stars which are very close but are not touching. Their orbit is aligned almost perpendicularly to us and there are both primary and secondary eclipses. During secondary eclipse, the primary transits against the secondary, which produces the flat bottom to the secondary minimum. The orbital alignment allows very precise calculation of the orbit and the properties of the stars, but results from different studies have been unusually inconsistent. The lack of a single consistent solution to the orbit has led to suggestions that there is a third star in the system, but this is unproven. A circular orbit with the stars only apart can account for the observed brightness and radial velocity changes, while a third body may explain the decreasing orbital inclination.
The two stars are both on the main sequence. The primary, a β Cephei pulsator, has a spectral type of B1 and temperature of about 26,000 K, while the secondary (possibly a slowly pulsating B-type star) has a spectral type of B7 and a temperature of about 16,000 K. The secondary has a mass of , radius of , and bolometric luminosity of . The primary is over twice the mass, twice the radius, and thirty times the luminosity of its companion.


Lambda Caeli

Lambda Caeli, Latinized from λ Caeli, is a star in the constellation Caelum. It is also known by its designations HD 30202 and HR 1518. This star is a challenge to view with the naked eye, having an apparent visual magnitude of 6.24. Based on parallax measurements, Lambda Caeli is known to be around 700 light-years distant from the Sun, but is drifting closer with a radial velocity of −4 km/s.
This object is an aging K-type giant star with a stellar classification of K3/4III. Having exhausted the supply of hydrogen at its core, it has cooled and expanded; now having 31 times the radius of the Sun. It is radiating 274 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,189 K.


NGC 7068

NGC 7068 is a spiral galaxy located about 215 million light-years away in the constellation of Pegasus. NGC 7068 was discovered by astronomer Albert Marth on November 7, 1863.
On June 26, 2013 a type 1a supernova designated as SN 2013ei was discovered in NGC 7068.


List of stars in Pegasus

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


J Centauri

J Centauri (J Cen) is a star in the constellation Centaurus. It is approximately 350 light years from Earth.
J Centauri is a spectral class B3V main sequence star with a mean apparent magnitude of 4.5 and a luminosity 500 times that of the Sun. The temperature of the star's photosphere is nearly 24,000 K. The rotation velocity at the equator is at least 223 km/s. It is believed to be a binary star system.
This star may be a member of the Scorpio-Centaurus OB association (Sco OB2). This is one of the nearest regions of recent star formation.


Sigma Leonis

Sigma Leonis, Latinized from σ Leonis, is a blue-white hued star in the zodiac constellation Leo that is visible to the naked eye with an apparent visual magnitude of 4.0. Its annual parallax shift of 15.24 mas as seen from Earth implies a distance around 210 light years from the Sun. It is moving closer to the Sun with a radial velocity of –5 km/s.
Chini et al. (2012) list this as a single-lined spectroscopic binary system. The visible component has a stellar classification of B9.5 Vs, indicating it is a B-type main-sequence star. It is a suspected magnetic Ap star that shows an abundance anomaly with the element silicon. Sigma Leonis has an estimated 2.76 times the mass of the Sun and 3.3 times the Sun's radius. It is about 293 million years old with a projected rotational velocity of 70 km/s. The star is radiating 133 times the Sun's luminosity from its photosphere at an effective temperature of 10,250 K.
Name.
In Chinese, (), meaning "Right Wall of Supreme Palace Enclosure", refers to an asterism consisting of σ Leonis, β Virginis, ι Leonis, θ Leonis and δ Leonis. Consequently, the Chinese name for σ Leonis itself is (, .), representing (), meaning "The First Western General". 西上將 (Xīshǎngjiāng), spelled Shang Tseang by R.H. Allen, means "the Higher General".


Zeta Leonis

Zeta Leonis (ζ Leonis, abbreviated Zeta Leo, ζ Leo), also named Adhafera , is a third-magnitude star in the constellation of Leo, the lion. It forms the second star (after Gamma Leonis) in the blade of the sickle, which is an asterism formed from the head of Leo.
Nomenclature.
"ζ Leonis" (Latinised to "Zeta Leonis") is the star's Bayer designation. It has the traditional name "Adhafera" ("Aldhafera", "Adhafara"), which comes from the Arabic "الضفيرة" "aḍ-ḍafīrah" 'the braid/curl', a reference to its position in the lion's mane. 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 "Adhafera" for this star.
Properties.
Adhafera is a giant star with a stellar classification of F0 III. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Its apparent magnitude is +3.44, making it relatively faint for a star that is visible to the naked eye. Nevertheless, it shines with 85 times the luminosity of the Sun. Adhafera has about three times the Sun's mass and six times the radius of the Sun. Parallax measurements from the Hipparcos satellite yield an estimated distance to Adhafera of from the Sun.
Adhafera forms a double star with an optical companion that has an apparent magnitude of 5.90. Known as 35 Leonis, this star is separated from Adhafera by 325.9 arcseconds along a position angle of 340°. The two stars do not form a binary star system as 35 Leo is only 100 light years from Earth, thus separating the two stars by approximately .


Quintuplet cluster

The Quintuplet cluster is a dense cluster of massive young stars about 100 light years from the Galactic Center (GC). Its name comes from the fact it has five prominent infrared sources residing in it. Along with the Arches Cluster it is one of two in the immediate GC region. Due to heavy extinction by dust in the vicinity, it is invisible to optical observation and must be studied in the X-ray, radio, and infrared bands.
The Quintuplet is less compact than the nearby Arches Cluster, with fewer of the most massive and luminous stars, but it does have the distinction of hosting two of the extremely rare luminous blue variables, the Pistol Star and the less well-known qF 362 (aka V4650 Sgr), and a third just a few parsecs away. It also contains a number of red supergiants, all suggesting a slightly more evolved cluster around 4 million years old.
Discovery and naming.
The Quintuplet was originally identified in 1983 as a pair of infra-red sources in a 2.5 micron survey of the galactic centre. These two sources were numbered 3 and 4, and later referred to with the acronym GCS for Galactic Centre Source. GCS-3 was later resolved into four sources, labelled I-IV, that together with GCS-4 formed a compact quintuplet of unusually bright small objects. They were assumed to be young hot luminous stars surrounded by dust shells and therefore extremely reddened.
In 1990, a total of 15 sources in the Quintuplet region was studied in more detail at several wavelengths, later referred to by Q or GMM (after the authors Glass, Moneti, and Moorwood) numbers. The original five stars were identified as numbers Q1, Q2, Q3, Q4, and Q9, with additional sources Q5 and Q6 identified as part of the same cluster. They were still considered to be protostars reddened by surrounding dust.
In 1994, several stars were identified as having broad helium emission lines in their spectra, and some showed narrow hydrogen emission lines. This was completely unexpected for protostars, instead suggesting the objects were much more evolved stars. Shortly afterwards two emission line stars were classified as Wolf Rayet stars, and a third as a Luminous Blue Variable that was thought to be one of the most luminous stars in the galaxy. A small number of red supergiants were also identified, narrowing the likely age of the cluster.
In 1999, a study of nearly 600 stars in the cluster showed that the Quintuplet contained more Wolf–Rayet stars than any known cluster, as well as a second Luminous Blue Variable. The numbers from this survey are referred to as qF, or sometimes as FMM after all three authors (but not QMM). A 2008 study of the cluster used LHO numbers for the members and clarified the status of the unusual reddened Wolf–Rayet stars as WC stars surrounded by dust presumed to be formed from colliding winds between the WR component and a less evolved OB companion.
The cluster was also catalogued as a first magnitude "stellar" source at 4.2 microns in the Air Force Geophysics Lab survey and given the number 2004 (AFGL 2004).
Properties.
The Quintuplet is seen (in the infra-red) 12 arc-minutes NW of Sagittarius A* (Sgr A*). The cluster stars and associated objects such as the Pistol Nebula have large radial velocities only likely to be from orbiting close to the galactic centre, so the cluster is thought to be physically associated with the galactic centre. The galactic centre is considered to be about 8 kpc away, so the projected distance of the Quintuplet on the sky is 30 pc from Sagittarius A*.
The age of the quintuplet can be estimated from the likely ages of its member stars. Mapping the stars of the cluster to evolutionary isochrones gives ages around 4 million years. However stars such as the two (or three) LBVs are expected to explode as supernovae within three million years, an obvious problem. It has been suggested that the age may be as low as 3.3-3.6 million years or that star formation was staggered over a million years or more Another proposal is that the remaining highly massive stars were formed or rejuvenated by binary interactions.
The masses of stars clusters can be measured by integrating the stellar mass function. Although only the most massive cluster members can be detected, the mass function can be estimated to lower levels and the cluster mass is calculated to be around .
Members.
The Quintuplet contains a number of massive and somewhat evolved stars, including 21 Wolf–Rayet stars, 2 luminous blue variables (three including the nearby runaway V4998 Sagittarii), and a number of red supergiants. There is also associated nebulosity ionised by the hot stars, most notably the Pistol Nebula between the Pistol Star and the core of the Quintuplet.


Eta Cancri

Eta Cancri, Latinized from η Cancri, is a single, orange-hued star in the zodiac constellation of Cancer. It is a faint star but visible to the naked eye with an apparent visual magnitude of 5.34. The annual parallax shift of 10.93 mas as seen from Earth yields a distance estimate of 155 light years from the Sun. It is moving further away with a radial velocity of +22 km/s.
A stellar classification of K3 III for Eta Cancri indicates that, at the estimated age of 3.9 billion years old, it has left the main sequence and become an evolved giant star. The spectrum shows unusually strong absorption lines of cyanogen. It has 1.5 times the mass of the Sun and has expanded to 17 times the Sun's radius. The star is radiating 87 times the Sun's luminosity from its photosphere at an effective temperature of around 4,415 K.
In Chinese astronomy, "Ghost" () refers to an asterism consisting of Theta Cancri, Eta Cancri, Gamma Cancri and Delta Cancri. Eta Cancri itself is the second star of Ghost (), following the designation from its determinative star (θ Cnc) from east to west.


V Centauri

V Centauri (V Cen) is a Classical Cepheid variable, a type of variable star, in the constellation Centaurus. Its apparent magnitude is 6.72, and it is approximately 2,500 light-years (800 parsecs) away based on parallax. According to the South African Astronomical Observatory, the chemical composition was derived as being high in sodium (Na) and aluminium (Al) and low in magnesium (Mg). Following a normal composition for a Cepheid star, V Cen does not have any unusual characteristics. V Centauri's composition was observed alongside six other Classical Cepheid variable stars with the support of Russian, Chilean, and Ukrainian observatories.


Omicron Velorum

Omicron Velorum (ο Vel, ο Velorum) is a star in the constellation Vela. It is the brightest member of the loose naked eye open cluster IC 2391, also known as the ο Velorum Cluster.
Omicron Velorum is a blue-white B-type subgiant with a mean apparent magnitude of +3.60. It is approximately 495 light years from Earth. A slowly pulsating B star, it ranges between magnitudes 3.57 and 3.63 over 2.8 days.
The correct Bayer designation for ο Velorum has been debated. Lacaille assigned one Greek letter sequence for the bright stars of Argo Navis. These Lacaille designations are now shared across the three modern constellations of Carina, Puppis, and Vela so that the same Greek letter is not usually found in more than one of the three. However, ο (omicron) is commonly used for stars in both Vela and Puppis. Some authors contend that Lacaille actually assigned a Latin lower case 'o' to this star, while others suggest that ο Puppis should actually be a lower case 'o'. In the "Coelum Australe Stelliferum" itself, this star is labelled ο (omicron) Argus (du Navire in the French edition), while ο Puppis is labelled (Latin) o Argus in puppi (Pouppe du Navire in the French edition).


HD 203857

HD 203857 is a double star in the constellation Cygnus. It is near the lower limit of visibility to the naked eye, having a combined apparent visual magnitude of 6.46. The distance to the primary component is approsimatly 1,230 light years based on parallax, and it has an absolute magnitude of −0.75. The star is drifting closer to the Sun with a radial velocity of −6.3 km/s. It has a stellar classification of K5 and is known to be evolved. The star likely hosts an extrasolar planet, though yet unconfirmed.
HD 203857 is listed in the Washington Double Star Catalogue as having five visual companions. It is separated by six arc-minutes from HD 203784, an F-type subgiant, though it is likely they are actually not gravitationally–bound. HD 203784 is thought to be closer to us and less luminous than HD 203857. There are also fainter stars at and . HD 203784 has a 13th-magnitude star and a 14th-magnitude star within .
Substellar companion.
Okayama Planet Search team has published a paper in late 2008 reporting investigations on radial velocity variations observed for a set of evolved stars, announcing possible detection of a substellar companion orbiting the giant star HD 203857. Orbital period is estimated 2.3 years, but planet has still to be confirmed.


Delta Canis Minoris

The Bayer designation Delta Canis Minoris (δ CMi / δ Canis Minoris) is shared by three stars, in the constellation Canis Minor:


NGC 3245

NGC 3245 is a lenticular galaxy in the constellation Leo Minor. It was discovered by William Herschel on April 11, 1785.


NGC 444

NGC 444 is a spiral galaxy of type Sd located in the constellation Pisces. It was first discovered on October 26, 1854 by R. J. Mitchell (and later listed as NGC 444), and was also spotted on October 17, 1903 by Stéphane Javelle (and later listed as IC 1658). It was described by Dreyer as "very faint, much extended 135°, a little brighter middle."


NGC 3226

NGC 3226 is a dwarf elliptical galaxy that is interacting with the spiral galaxy NGC 3227. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in the "Atlas of Peculiar Galaxies". Both galaxies may be found in the constellation Leo.
Nucleus.
NGC 3226 contains a low-ionization nuclear emission-line region (LINER), a type of region that is characterized by spectral line emission from weakly ionized atoms. In general, the energy source for LINER emission has been a subject of debate among astronomers. Some astronomers have asserted that LINERs are powered by star formation regions, while other have asserted that LINERs are powered by active galactic nuclei (AGN) which contain supermassive black holes.
AGN.
The nucleus of NGC 3226 appears to contain an AGN. The nucleus is a strong source of both radio and X-ray emission that appears to be synchrotron emission, which is generated when electrons moving at high speeds oscillate within magnetic fields. Such synchrotron emission is expected from the environment around a supermassive black hole. The X-ray emission may also be variable, which is also expected in the environment of a supermassive black hole.
Interstellar medium.
It is possible that NGC 3226 may be acquiring gas from NGC 3227 during the interaction process, which would enhance star formation within NGC 3226. However, millimeter observations of NGC 3226 failed to detect any molecular gas within the galaxy. These results not only demonstrate that NGC 3226 contains little molecular gas but also demonstrate that the galaxy has acquired no gas from NGC 3227.


2 Pegasi

2 Pegasi is a single star in the constellation Pegasus, located approximately 394 light years away from the Sun based on parallax. It is visible to the naked eye as a faint, red-hued star with an apparent visual magnitude of 4.52. The object is moving closer to the Earth with a heliocentric radial velocity of −19 km/s. It has a magnitude 12.7 visual companion, designated component B, at an angular separation of .
This is an aging red giant star with a stellar classification of M1+III, currently on the asymptotic giant branch, having exhausted the hydrogen at its core and evolved away from the main sequence. The star has expanded to an estimated 55 times the radius of the Sun. It is radiating 653 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of .


NGC 3928

NGC 3928 is a lenticular galaxy in the constellation Ursa Major. It was discovered by William Herschel on March 9, 1788.


NGC 7448

NGC 7448 is a spiral galaxy located in the constellation Pegasus. It is located at a distance of circa 80 million light years from Earth, which, given its apparent dimensions, means that NGC 7448 is about 60,000 light years across. It was discovered by William Herschel on October 16, 1784. It is included in the Atlas of Peculiar Galaxies in the category galaxies with detached segments.
NGC 7448 features an inner disk region of tightly wound spiral fragments with high surface brightness. At the edge of this region the surface brightness decreases abruptly. At the outer part of the disk individual arm segments and dust lanes can be discerned. The outer arms feature HII regions. One HII region complex located at the northwest portion of the disk is as bright as the bulge. Two supernovae have been observed in NGC 7448, SN 1980L (mag 13.5), and SN 1997dt (type Ia, mag 15.3).
NGC 7448 belongs to a galaxy group known as the NGC 7448 group. Other members of the group are the galaxies NGC 7437, NGC 7454, NGC 7463, NGC 7464, and NGC 7465. The last three form a compact subgroup and there is evidence that NGC 7464 and NGC 7465 are in the process of merging. NGC 7479 lies a bit further to the south, and may be part of the group. There is a tail of HI gas extending from NGC 7448 and a stream of gas extending from NGC 7464/65 to NGC 7448.


HAT-P-3

HAT-P-3, is a metal-rich K5 dwarf star located about 441 light-years away in the constellation Ursa Major. At a magnitude of about 11.5 it is not visible to the naked eye but is visible in a small to medium-sized amateur telescope. It is believed to be a relatively young star and has a slightly enhanced level of chromospheric activity.
The star HAT-P-3 is named Dombay. The name was selected in the NameExoWorlds campaign by Russia, during the 100th anniversary of the IAU. Dombay is a resort region in the North Caucasus mountains.
Planetary system.
This star is home to the extrasolar planet HAT-P-3b discovered by the HATNet Project using the transit method.


Lambda Draconis

Lambda Draconis (λ Draconis, abbreviated Lam Dra, λ Dra), also named Giausar , is a solitary, orange-red star in the northern circumpolar constellation of Draco. It is visible to the naked eye with an apparent visual magnitude of +3.85. Based upon an annual parallax shift of 9.79 mas as seen from the Earth, the star is located around 333 light years from the Sun.
This is an evolved red giant star on the asymptotic giant branch with a stellar classification of M0III-IIIa Ca1. It is a suspected slow irregular variable with a periodicity of roughly 1,100 days. The measured angular diameter, after correction for limb darkening, is . At the estimated distance of the star, this yields a physical size of about 53 times the radius of the Sun. It has an estimated 1.7 times the mass of the Sun and is radiating 834 times the solar luminosity from its photosphere at an effective temperature of 3,958 K.
Nomenclature.
λ Draconis (Latinised to "Lambda Draconis") is the star's Bayer designation.
It bore the traditional name "Giausar" (also written as "Gianfar, Giansar and Giauzar") and "Juza." 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 "Giausar" for this star on February 1, 2017 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "Right Wall of Purple Forbidden Enclosure", refers to an asterism consisting of Lambda Draconis, Alpha Draconis, Kappa Draconis, 24 Ursae Majoris, 43 Camelopardalis, Alpha Camelopardalis and BK Camelopardalis. Consequently, the Chinese name for Lambda Draconis itself is (, .), representing (), meaning "First Minister". 上輔 (Shǎngfǔ) was westernized into "Sang Poo" or "Shaou Poo" by R.H. Allen.
Namesakes.
USS Giansar (AK-111) was a United States Navy Crater class cargo ship named after the star.
References.
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NGC 506

NGC 506 is a star in the constellation Pisces. It was discovered on 7 November 1874 by Lawrence Parsons, the 4th Earl of Rosse.
Observation history.
Lawrence discovered the object during his last observation of the NGC 499 Group. Though he noted no description, he gave a micrometric measure setting the object's position relative to a different nearby star. There is no object at this position, but the NGC position is corrected further southeast which leads to the assumption that John Louis Emil Dreyer, creator of the New General Catalogue, had additional information when he catalogued the star. In the catalogue, the object is described as "very faint, very small, southwest of NGC 507".


HD 83058

HD 83058 is a subgiant star in the constellation Vela and a spectroscopic binary. It is visible to the naked eye with an apparent visual magnitude of 5.0. Based upon an annual parallax shift of , it is located from the Sun. The system is moving further away with a heliocentric radial velocity of +.
HD 83058 has generally been considered to be a single star, but high-resolution spectra show it to be a double-lined spectroscopic binary. The two components have approximately the same spectral type. Line-profile variations have been detected which suggest that at least one component pulsates, as is common for stars of this spectral class.
HD 83058 was proposed as a runaway star from a supernova explosion. However, the discovery that it was a binary make this unlikely.


LBG-2377

LBG-2377 is the most distant galaxy merger discovered, as of 2008, at a distance of 11.4 billion light years. This galaxy merger is so distant that the universe was in its infancy when its light was emitted. It is expected that this galaxy proto-cluster will merge to form a brightest cluster galaxy, and become the core of a larger galaxy cluster.
Discovery.
Observations were conducted with the Keck Telescope in Hawaii by Jeff Cooke, a McCue Postdoctoral Fellow in physics and astronomy at UCI. While looking for single galaxies, Cooke found something that at first appeared like a bright, single object. However, further analysis of wavelengths of the emitted light proved that they were three galaxies merging, and likely two smaller galaxies.


S Antliae

S Antliae is a W Ursae Majoris-type eclipsing binary star in Antlia.
Characteristics.
S Antilia is classed as an A-type W Ursae Majoris variable, since the primary is hotter than the secondary and the drop in magnitude is caused by the latter passing in front of the former. S Antilia varies in apparent magnitude from 6.27 to 6.83 over a period of 15.6 hours. The system shines with a combined spectrum of A9V.
The system's orbital period is 6.48 days. The eccentricity of the orbit is 0.66. The stars' centres are an average of 3.31 times the sun's radius apart, which places their surfaces just 0.36 times the sun's radius apart. Thus, the two stars will eventually merge to form a single fast-spinning star.
Calculating the properties of the component stars from the orbital period indicates that the primary star has a mass 1.94 times and a diameter 2.026 times that of the Sun, and the secondary has a mass 0.76 times and a diameter 1.322 times that of the Sun. The primary has a surface temperature of 7800 K, while the secondary is a little cooler at 7340 K. The two stars have similar luminosity and spectral type as they have a common envelope and share stellar material. The system is thought to be around 5-6 billion years old.
Based upon an annual parallax shift of 11.84 milliarc seconds as measured by the Hipparcos satellite, this system is from Earth. Analysing and recalibrating yields a parallax of 13.30 and hence a distance of .
History.
The star's variability was first recorded in 1888 by H.M. Paul, when it had the shortest known period of any variable star. It was initially thought to be an Algol-type eclipsing binary, but this was discounted by E.C. Pickering on account of it lacking a shallow minimum in its maximum and the width of its minimum period. Alfred H. Joy noted the similarity of its light curve to W Ursae Majoris in 1926, concluding the system was indeed an eclipsing binary with two stars of spectral type A8.


Eta Scuti

Eta Scuti, Latinized from η Scuti, is a single star in the southern constellation of Scutum, near the constellation border with Aquila. Eta Scuti was a latter designation of 9 Aquilae before the official constellation borders were set in 1922. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of +4.83. This object is located approximately 213 light years from the Sun based on parallax, and is drifting further away with a radial velocity of -92.
This is an aging giant star with a stellar classification of K1-III. After exhausting the supply of hydrogen at its core, the star cooled and expanded until currently it has 12 times the girth of the Sun. It is a red clump giant, which indicates it is presently on the horizontal branch and is generating energy through core helium fusion. The star is about 2.8 billion years old with 1.5 times the mass of the Sun. It is radiating 63 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,693 K.


RT Aurigae

RT Aurigae (RT Aur, 48 Aurigae) is a yellow supergiant variable star in the constellation Auriga, about 1,500 light years from Earth.
RT Aurigae is an F to G type Classical Cepheid variable which varies from magnitude +5.00 to +5.82 with a period of 3.728309 days. The variability was discovered in 1905. It was quickly recognised as a member of the class of Cepheid variables, but their nature was not understood at that time. Radial velocity changes were detected corresponding to the brightness variations, but the idea that these were caused by stellar pulsations and temperature changes was largely dismissed in favour of orbital motions of a binary star. More accurate observations eventually proved beyond doubt that the brightness variations were caused by pulsations in the atmospheres of the stars, with the stars being smallest and hottest near maximum brightness.
RT Aurigae has been suspected to be a spectroscopic binary system, but this has not been confirmed. The strongest evidence was found in 2013 using CHARA array optical interferometry. The companion would be 6.7 magnitudes fainter than the supergiant primary, cooler and fainter than an F0 main sequence star. The two stars are separated by 2.1 milli-arc seconds.


Arches Cluster

The Arches Cluster is the densest known star cluster in the Milky Way located about 100 light-years from its center, in the constellation Sagittarius (The Archer), 25,000 light-years from Earth.
The discovery of this cluster was reported by Nagata et al. in 1995, and independently by Cotera et al. in 1996.
Due to extremely heavy optical extinction by dust in this region, the Arches Cluster is obscured in the visual bands, and is observed in the X-ray, infrared, and radio bands. It contains approximately 135 young, very hot stars that are many times larger and more massive than the Sun, plus many thousands of less massive stars.
This star cluster is estimated to be around two and a half million years old. Although larger and denser than the nearby Quintuplet Cluster, it appears to be slightly younger. Only stars earlier and more massive than O5 have evolved away from the main sequence while the Quintuplet Cluster includes a number of hot supergiants as well as a red supergiant and three luminous blue variables.
The most prominent members of the Arches Cluster are hot emission line stars: thirteen Wolf–Rayet stars, all massive hydrogen-rich types; and eight class O hypergiants. One of these is an eclipsing binary with a Wolf-Rayet primary and a class O supergiant secondary. X-ray emission from the cluster suggests that many other members are also in close binary systems with two hot luminous members, but there is little evidence of the evolution of these stars being affected by binary mass exchange. The spectral classes and their properties merge smoothly from the main sequence to normal class O giants and supergiants, to class O hypergiants, to the presumed most evolved Wolf-Rayets. One star is intermediate between WN8-9h and O4-6 Ia+. There are no cooler evolved stars.
Work by Donald Figer, an astronomer at the Rochester Institute of Technology suggests that 150 solar masses () is the upper limit of stellar mass in the current era of the universe. He used the Hubble Space Telescope to observe about a thousand stars in the Arches cluster and found no stars over that limit despite a statistical expectation that there should be several. However, later research demonstrated a very high sensitivity of the calculated star masses upon the extinction laws used for mass derivation, which can affect the upper mass limit by about 30% using different extinction laws (possibly from to about ).


Xi Ophiuchi

ξ Oph, Latinized as Xi Ophiuchi, is a visual binary star system in the equatorial constellation of Ophiuchus. It has a yellow-white hue and is faintly visible to the naked eye with a combined apparent visual magnitude of 4.39. The system is located approximately 56.6 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of -9 km/s.
The magnitude 4.40 primary, designated component A, is an ordinary F-type main-sequence star with a stellar classification of F2V. It is 916 million years old and is rotating with a projected rotational velocity of 20 km/s. The star has 1.3 times the mass of the Sun and 1.6 times the Sun's radius. It is radiating 4.4 times the luminosity of the Sun from its photosphere at an effective temperature of 6,611 K.
The system is a source of X-ray emission. The orbiting companion, component B, is a magnitude 8.9 star at an angular separation of along a position angle of 27° from the primary, as of 2015. A magnitude 10.8 visual companion, component C, lies at a separation of , as of 2004.


Omicron Draconis

Omicron Draconis (Latinised as ο Draconis, abbreviated to ο Dra) is a giant star in the constellation Draco located 322.93 light years from the Earth. It has a radius of 30 solar radii, and a luminosity of 269 suns. Its path in the night sky is circumpolar above the ecliptic, meaning the star never rises or sets when viewed in the night sky from certain positions in the northern hemisphere.
Omicron Draconis can be considered the north pole star of Mercury, as it is the closest star to Mercury's north celestial pole.
This is a single-lined spectroscopic binary system, but the secondary has been detected using interferometry. It is a RS Canum Venaticorum variable system with eclipses. The total amplitude of variation is only about a thousandth of a magnitude. The secondary star is similar to the sun, presumably a main sequence star, while the primary is a giant star 25 times larger than the sun and two hundred times more luminous.


Chi Capricorni

Chi Capricorni, Latinized from χ Capricorni, is a star in the southern constellation of Capricornus. Based upon an annual parallax shift of 18.14 mas as seen from the Earth, the star is located about 180 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of +5.28.
Properties.
This is an A-type main sequence star with a stellar classification of A0 V. It is a candidate Lambda Boötis star, showing a chemically peculiar spectrum with a low abundance of most elements heavier than oxygen. The star is around 251 million years old and is spinning rapidly with a projected rotational velocity of 212 km/s. It has 2.78 times the mass of the Sun and is radiating 21 times the solar luminosity from its photosphere at an effective temperature of 10,878 K.
At an angular separation of 1,199 arcseconds lies a faint proper motion companion designated HIP 99550. At the estimated distance of Chi Capricorni, this is equal to a projected separation of 28,300 AU. It has a visual magnitude of 10.94 and a classification of M0 Vk, indicating this is a red dwarf star.
Chinese Name.
In Chinese, (), meaning "Twelve States", refers to an asterism which is represent twelve ancient states in the Spring and Autumn period and the Warring States period, consisting of χ Capricorni, φ Capricorni, ι Capricorni, 38 Capricorni, 35 Capricorni, 36 Capricorni, θ Capricorni, 30 Capricorni, 33 Capricorni, ζ Capricorni, 19 Capricorni, 26 Capricorni, 27 Capricorni, 20 Capricorni, η Capricorni and 21 Capricorni. Consequently, the Chinese name for χ Capricorni itself represents the state Qi (), together with 112 Herculis in "Left Wall of Heavenly Market Enclosure" (asterism).
R.H.Allen had opinion that χ Capricorni, together with φ Capricorni, were represent the state Wei (魏).


Kappa Ophiuchi

Kappa Ophiuchi (κ Oph, κ Ophiuchi) is a star in the equatorial constellation Ophiuchus. It is a suspected variable star with an average apparent visual magnitude of 3.20, making it visible to the naked eye and one of the brighter members of this constellation. Based upon parallax measurements made during the Hipparcos mission, it is situated at a distance of around from Earth. The overall brightness of the star is diminished by 0.11 magnitudes due to extinction from intervening matter along the line of sight.
The spectrum of this star matches a stellar classification of K2 III, with the luminosity class of 'III' indicating this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence of stars like the Sun. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is 19% more massive than the Sun, but the outer envelope has expanded to around 11 times the Sun's radius. With its enlarged size, it is radiating 46 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 4,529 K. This is cooler than the Sun's surface and gives Kappa Ophiuchi the orange-hued glow of a K-type star.
Although designated as a variable star, observations with the Hipparcos satellite showed a variation of no more than 0.02 in magnitude. In designating this as a suspected variable star, it is possible that Kappa Ophiuchi was mistaken for Chi Ophiuchi, which is a variable star. Kappa Ophiuchi belongs to an evolutionary branch known as the red clump, making it a clump giant. The surface abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is similar to the abundances of those elements in the Sun.


Nu Hydrae

Nu Hydrae, Latinized from ν Hydrae, is an orange-hued star in the constellation Hydra, near the border with the neighboring constellation of Crater. It has an apparent visual magnitude of 3.115, which is bright enough to be seen with the naked eye. Based upon parallax measurements, this star is located at a distance of about from the Earth.
The spectrum of this star matches a stellar classification of K0/K1 III, where the luminosity class of 'III' indicates this is a giant star that has exhausted the supply of hydrogen at its core and evolved away from the main sequence. The radius of this star has expanded to 21 times the Sun's radius with an emission of about 151 times the luminosity of the Sun. This expanded outer envelope has an effective temperature of about 4,335 K, giving it the characteristic orange hue of a K-type star.
Nu Hydrae is an X-ray emitter with an estimated luminosity of in the X-ray band. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is about half that in the Sun. It has a relatively high proper motion across the celestial sphere, suggesting that it has a peculiar velocity roughly three times higher than its neighbors.
Nu Hydrae was a later designation of 4 Crateris.


Nu2 Lupi

Nu2 Lupi (ν2 Lup) is a 6th magnitude G-type main-sequence star located approximately 48 light-years away in the constellation of Lupus. The physical properties of the star are similar to those of the Sun, though Nu2 Lupi is significantly older.
Properties.
Nu2 Lupi is a bright star, barely observable with the naked eye in good observing conditions, that lies towards the bottom Lupus near to the border with Norma and close to the galactic plane.
At over 1.6 arcseconds per year, Nu2 Lupi has a particularly large proper motion. This indicates that the star is nearby, which was confirmed by Earth-based parallax measurements during the last century such as that of the Gliese Catalogue of Nearby Stars, measuring 63.1 ± 7.8 milli-arcseconds. The much more accurate space-based Hipparcos parallax of 67.51 ± 0.39 milli-arcseconds gives a distance of 48.3 ± 0.3 light-years, making Nu2 Lupi one of the closest G-type main-sequence stars to the Sun.
Somewhat surprisingly, Nu2 Lupi also has a large radial velocity of -68.7 km/s. When combined with its large proper motion, it becomes apparent that the star is moving much faster through the galaxy than the Sun. This indicates that the star is a member of an older, higher-motion stellar population, which is confirmed by the star's position on the Toomre diagram with Nu2 Lupi showing kinematics of a thick disk star. This means that Nu2 Lupi must be considerably older than the Sun, which is supported by its spectroscopic parameters: the depth of the star's iron spectral lines implies an iron abundance of -0.34 ± 0.01 dex, equalling 46 ± 1% of the solar iron abundance - a typical value for a thick disk star. Similarly, the star's surface gravity of log 4.39 ± 0.02 g is somewhat lower than is typical for a main-sequence G-type star and indicates modest evolution, which when combined with a spectroscopically derived mass of implies an age of 10.36 ± 2.30 billion years, over twice the solar age. Nu2 Lupi is therefore probably one of the oldest stars in the solar neighbourhood.
Planetary system.
On September 12, 2011 three low-mass planets were announced using data from the HARPS spectrograph. These three planets are among about seven dozen planets discovered in September 2011, the most of any month during the exoplanet era that begun in early 1990s. The two inner planet were also found using a transit method in 2020, allowing a precise determination of their mass and radii.
With a minimum mass of about 5 Earth masses, the innermost planet falls into the regime of Super-Earths, and was confirmed to be mostly rocky with density 7.8 g/cm3 in 2020. Outer planets straddle the commonly accepted upper limit between Super-Earths and Neptunes at , so it could be either predominantly rocky or gaseous. The middle planet Nu2 Lupi c with density 3.5 g/cm3 is expected to have a large gaseous envelope. All three planets orbit within 0.5 AU and are likely too hot to maintain liquid water.
The most recent published observation of this system for debris disks was in 2006 by the Spitzer telescope, searching for an excess of infra-red light that would indicate scattering of starlight by dust or planetesimals; no infra-red excess was detected.


OGLE-TR-56b

OGLE-TR-56b is an extrasolar planet located approximately 1500 parsecs away in the constellation of Sagittarius, orbiting the star OGLE-TR-56. This planet was the first known exoplanet to be discovered with the transit method. The object was discovered by the OGLE project, announced on July 5, 2002 and confirmed on January 4, 2003 by the Doppler technique.
The period of this confirmed planet was the shortest until the confirmed discovery of WASP-12b on April 1, 2008.
The short period and proximity of the OGLE-TR-56 b to its host mean it belongs to a class of objects known as hot Jupiters.
The planet is theorized to have iron rain.


NGC 4589

NGC 4589 is an elliptical galaxy located in the Draco constellation. It is at a distance of about 108 million light-years away from the Earth. It is known by its designations PGC 42139 or UGC 7797.
In the center of NGC 4589 lies a supermassive black hole in its center. It has a supernova called 2005cz. NGC 4589 was discovered by astronomer William Herschel on November 22, 1797.


NGC 6540

NGC 6540 is a globular cluster in the constellation Sagittarius. Its apparent magnitude is 9.3 and its diameter is about 9.5 arcminutes, with 12 faint stars visible. It is about 17,000 light years away from Earth and was discovered by Wilhelm Herschel on May 24, 1784 with an 18.7-inch mirror telescope, who described the cluster as "pretty faint, not large, crookedly extended, easily resolvable".


Epsilon Circini

Epsilon Circini, Latinized from ε Circini, is a solitary star located in the southern constellation of Circinus. It is faintly visible to the naked eye, having an apparent visual magnitude of 4.86. The distance to this star, as determined by a measured annual parallax shift of 8.00 mas, is around 410 light years.
This is an evolved K-type giant star with a stellar classification of K2.5 III. The measured angular diameter of this star is . At its estimated distance, this yields a physical size of about 27 times the radius of the Sun. It radiates about 244 times the solar luminosity from its outer atmosphere at an effective temperature of 4,576 K.
References.
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26 Vulpeculae

26 Vulpeculae is a close binary star system in the northern constellation of Vulpecula, around 644 light years away from the Sun. It is a challenge to view with the naked eye, having an apparent visual magnitude of 6.40. The star is moving closer to the Earth with a heliocentric radial velocity of −63 km/s, and is expected to come within in around 2.6 million years.
This is a single-lined spectroscopic binary with an orbital period of 11 days and an eccentricity of 0.28. The visible component is a suspected chemically peculiar star with a stellar classification of A5 III, suggesting this is an evolved giant star. It has about 4.6 times the Sun's radius and is radiating 80 times the Sun's luminosity from its photosphere at an effective temperature of 7,888 K.


HD 95808

HD 95808 is a double star in the constellation of Crater. Its apparent magnitude is 5.50, but interstellar dust makes it appear 0.11 magnitudes dimmer than it should be. It is located some 340 light-years (104 parsecs) away, based on parallax.
HD 95808 is a G-type giant star. At an age of 680 million years old, it has swelled up to a radius of 10.1 times that of the Sun, and it is 2.43 times as massive. It emits 64.6 times as much energy as the Sun at a surface temperature of 5,029 K.


NGC 2536

NGC 2536 is a barred spiral galaxy with a prominent inner ring structure encircling the bar in the constellation Cancer that is interacting with NGC 2535. The two galaxies are listed together in the "Atlas of Peculiar Galaxies" as an example of a spiral galaxy with a high surface brightness companion.


5 Vulpeculae

5 Vulpeculae is a single, white-hued star in the northern constellation of Vulpecula. It is situated amidst a random concentration of bright stars designated Collinder 399, or Brocchi's Cluster. This is a faint star that is just visible to the naked eye with an apparent visual magnitude of 5.60. Based upon an annual parallax shift of , it is located around 235 light years from the Sun. It is moving closer with a heliocentric radial velocity of −21 km/s, and will make its closest approach in 2.5 million years at a separation of around .
This is a young A-type main-sequence star with a stellar classification of A0 V. It is a rapidly rotating star with a projected rotational velocity of 154 km/s. The star has an estimated 2.33 times the mass of the Sun and about 2.7 times the Sun's radius. It is radiating 34 times the Sun's luminosity from its photosphere at an effective temperature of 8,940 K.
A warm debris disk was detected by the Spitzer Space Telescope at a temperature of , orbiting 13 Astronomical units from the host star. Although this finding has not been directly detected, the emission signature indicates the disk is in the form of a thin ring. The emission displays weak transient absorption features that are indicative of kilometer-sized exocomets that are undergoing evaporation as they approach the host star. These absorption features have been observed to vary on time scales of hours, days, or months.


NGC 3902

NGC 3902 is an intermediate spiral galaxy in the constellation Leo. It was discovered on April 6th, 1785 by William Herschel and observed on February 19th, 1827 by John Herschel. It is estimated to be 180 to 185 million light-years away, and its redshift-independent distance estimates to about 185 to 240 million light-years. It is around 75 thousand light-years in diameter.
NGC 3902 is one galaxy within the NGC 3902 group (or LGG 254), a group of galaxies in Leo; the other galaxies of which are NGC 3920, NGC 3944, UGC 6806 and UGC 6807.


Epsilon Hydrae

Epsilon Hydrae (ε Hydrae, abbreviated Epsilon Hya, ε Hya) is a multiple star system of a combined third magnitude in the constellation of Hydra. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly distant from the Sun.
The system consists of a binary pair designated Epsilon Hydrae AB, whose two components are themselves designated Epsilon Hydrae A (formally named Ashlesha ) and B, orbited by a spectroscopic binary designated Epsilon Hydrae C. A possible fourth component, designated Epsilon Hydrae D, shares a common proper motion with the other components and thus is most likely a gravitationally-bound member of the system.
Nomenclature.
"ε Hydrae" (Latinised to "Epsilon Hydrae") is the system's Bayer designation. The designations of the three constituents as "Epsilon Hydrae AB", "C" and "D", and those of "AB's" components - "Epsilon Hydrae A" and "B" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
In ancient Indian astronomy, the five-star cluster of Hydrae is collectively called आश्लेषा "āślēṣā" () "the embrace", the 9th of the 27 nakshatras or lunar mansions in Hindu astrology. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Ashlesha" for the component Epsilon Hydrae A on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.
This system, along with Delta Hydrae (Lisan al Sudja), Zeta Hydrae, Eta Hydrae, Rho Hydrae and Sigma Hydrae (Minchir), were Ulug Beg's "Min al Azʽal", "Belonging to the Uninhabited Spot". According to a 1971 NASA technical memorandum, "Min al Azʽal" or "Minazal" were the title for five stars: Delta Hydrae as "Minazal I", Eta Hydrae as "Minazal II", Epsilon Hydrae as "Minazal III", Rho Hydrae as "Minazal IV" and Zeta Hydrae as "Minazal V".
In Chinese, (), meaning "Willow (asterism)", refers to an asterism consisting of Epsilon Hydrae, Delta Hydrae, Sigma Hydrae, Eta Hydrae, Rho Hydrae, Zeta Hydrae, Omega Hydrae and Theta Hydrae Consequently, Epsilon Hydrae itself is known as (, ).
"Unwala", "The Crab", was the name given by the people of Groote Eylandt to the star cluster including this star, Delta Hydrae (Lisan al Sudja), Zeta Hydrae, Eta Hydrae, Rho Hydrae and Sigma Hydrae (Minchir).
Properties.
The Epsilon Hydrae AB binary has an orbital period of 15 years and an angular separation of 0.2 arcseconds. The spectroscopic binary Epsilon Hydrae C has a period of 9.9047 days and an orbital eccentricity of 0.62, while simultaneously orbiting AB with a period of 870 years. C is separated from AB by 3 arcseconds. Epsilon Hydrae D is separated from AB by 19 arcseconds and has an estimated orbital period of around 10,000 years.
The primary, Epsilon Hydrae A, is a giant star that is shining with 67 times the luminosity of the Sun. This energy is being radiated from the star's outer atmosphere at an effective temperature of 5,620 K, giving it the yellow hue of a G-type star. It is rotating rapidly with a projected rotational velocity of 19 km s−1. It has an X-ray luminosity of .


26 Hydrae

26 Hydrae is a binary star system located 334 light years away from the Sun in the equatorial constellation of Hydra. It is visible to the naked eye as a faint, yellow-hued point of light with a combined apparent visual magnitude of 4.77, just a few degrees away from Alphard. The system is moving closer to the Earth with a leisurely radial velocity of -1 km/s.
Keenan and McNeil (1989) gave the brighter component a stellar classification of G7 III, matching an aging giant star. Houk and Swift (1999) have it classed as a G8II bright giant. This is a red clump giant, which indicates it is on the horizontal branch and is generating energy through helium fusion at its core. It has a high lithium abundance and displays a far infrared emission excess. The star is an estimated 510 million years old with 2.72 times the mass of the Sun and has expanded to 15 times the Sun's radius. It is radiating 139 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 5,003 K.
The secondary component is a magnitude 12.4 star at an angular separation of , as of 2008.


Rho Sagittarii

The Bayer designation Rho Sagittarii (Rho Sgr, ρ Sagittarii, ρ Sgr) is shared by two stars in the constellation Sagittarius.
The two stars are separated by 0.46° in the sky. Because they are close to the ecliptic, they can be occulted by the Moon and, very rarely, by planets. The next occultation of ρ¹ Sagittarii by a planet will take place on 23 February 2046, when it will be occulted by Venus.
In Chinese, (), meaning "Establishment", refers to an asterism consisting of ρ¹ Sagittarii ξ² Sagittarii, ο Sagittarii, π Sagittarii, 43 Sagittarii and υ Sagittarii. Consequently, ρ¹ Sagittarii itself is known as (, .)


35 Cygni

35 Cygni is a spectroscopic binary star in the constellation Cygnus. Its apparent magnitude is 5.18. Located around distant, its primary is a yellow supergiant of spectral type F6Ib, a massive star that has used up its core hydrogen and is now fusing heavier elements.
Yellow supergiants are usually variable, often Classical Cepheid variables, but 35 Cyg is notable for having an especially constant brightness.
35 Cyg is a single-lined spectroscopic binary with a period of 2,440 days (over 6 years). The secondary cannot be seen directly, nor can its spectral lines be identified but the overall spectrum can be match by a combination of an F4 supergiant and a less luminous B6.5 star.


HD 60803

HD 60803 is a binary star system in the equatorial constellation of Canis Minor, located less than a degree to the northwest of the prominent star Procyon. It has a yellow hue and is visible to the naked eye as a dim point of light with a combined apparent visual magnitude of 5.904. The distance to this system is 135 light years as determined using parallax measurements, and is drifting further away with a radial velocity of +4.6 km/s.
The binary nature of this star system was first noted by O. C. Wilson and A. Skumanich in 1964. It is a double-lined spectroscopic binary with an orbital period of 26.2 days and an eccentricity of 0.22. Both components are similar, G-type main-sequence stars; the primary has a stellar classification of G0V while the secondary has a class of G1V. The masses are similar to each other, and are 28–31% greater than the mass of the Sun. They have low rotation rates which may be quasi-synchronized with their orbital period.


Epsilon Ophiuchi

Epsilon Ophiuchi (ε Ophiuchi, abbreviated Epsilon Oph, ε Oph), formally named Yed Posterior , is a red giant star in the constellation of Ophiuchus. Located less than five degrees south of the celestial equator in the eastern part of the constellation, it forms a naked eye optical double with Delta Ophiuchi (named "Yed Prior"). With an apparent visual magnitude of 3.220, the star can be seen with the naked eye from most of the Earth under suitably dark skies. Parallax measurements yield an estimated distance of from the Sun.
Nomenclature.
"ε Ophiuchi" (Latinised to "Epsilon Ophiuchi") is the star's Bayer designation.
It bore the traditional name "Yed Posterior". "Yed" derives from the Arabic يد "yad" meaning "hand". "Epsilon" and "Delta Ophiuchi" comprise the left hand of Ophiuchus (the Serpent Bearer) that holds the head of the serpent (Serpens Caput). "Epsilon" is "Yed Posterior" as it follows "Delta " across the sky. 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 "Yed Posterior" for this star on 5 October 2016 and it is now so included in the List of IAU-approved Star Names.
Epsilon Ophiuchi was a member of the indigenous Arabic asterism "al-Nasaq al-Yamānī", the "Southern Line" of "al-Nasaqān" the "Two Lines", along with Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Delta Ophiuchi, Zeta Ophiuchi and Gamma Ophiuchi.
In Chinese, (), meaning "Right Wall of Heavenly Market Enclosure", refers to an asterism which represents eleven ancient states in China and which mark the right borderline of the enclosure, consisting of Delta Ophiuchi, Beta Herculis, Gamma Herculis, Kappa Herculis, Gamma Serpentis, Beta Serpentis, Alpha Serpentis, Delta Serpentis, Epsilon Serpentis, Epsilon Ophiuchi and Zeta Ophiuchi. Consequently, the Chinese name for Epsilon Ophiuchi itself is (, ), representing the state Chu (楚) (or Tsoo), together with Phi Capricorni (or 24 Capricorni in R.H.Allen's version) in the "Twelve States" (asterism).
Properties.
Epsilon Ophiuchi has a stellar classification of G9.5 IIIb, with the luminosity class of III indicating that this is a giant star that has exhausted the hydrogen and evolved away from the main sequence. This red giant has nearly double the Sun's mass and has expanded to an estimated radius of over ten times the radius of the Sun, giving it a luminosity of about 54 times the Sun. It is about a billion years old.
Unusually for a class G giant, it is cyanogen-deficient and carbon-deficient. The outer envelope of this star displays solar-type oscillations with a period of 0.19 days, allowing the methods of asteroseismology to be applied. However, the models for this star have not been able to distinguish whether this star is generating energy by the thermonuclear fusion of hydrogen along a shell, or the fusion of helium at its core. Either model produces a good fit to the star's physical properties. The projected rotational velocity of the star is 5.7 km s−1, and the inclination of the rotation axis to the line of sight from the Earth lies in the range of 41–73°.


Q Eridani

q Eridani refers to 2 distinct star systems in the constellation Eridanus:


Pi Canis Majoris

Pi Canis Majoris (π Canis Majoris) is a binary star system in the southern constellation of Canis Major. It is visible to the naked eye, having an apparent visual magnitude of +4.69. Based upon an annual parallax shift of 33.80 mas as seen from Earth, this system is located 96.5 light years from the Sun. The star is moving in the general direction of the Sun with a radial velocity of −37.9 km/s. It will make it closest approach in around 733,000 years when it comes within .
The brighter primary, component A, is an F-type main-sequence star with a stellar classification of F1.5 V. It is a periodic variable star with a frequency of 11.09569 cycles per day (2.16 hours per cycle) and an amplitude of 0.0025 in magnitude. The star has an estimated 1.32 times the mass of the Sun and is radiating nine times the Sun's luminosity from its photosphere at an effective temperature of around 6,863 K. It displays a strong infrared excess at a wavelength of 24 μm and a weaker excess at 70 μm, indicating the presence of a circumstellar disk of dust with a temperature of 188 K, orbiting at 6.7 AU from the host star.
The magnitude 9.6 companion, component B, lies at an angular separation of 11.6 arc seconds from the primary as of 2008. Their projected separation is about 339 AU.


HR 9038

HR 9038 is a triple star system located thirty-five light-years away, in the constellation Cepheus. Component A is a spectroscopic binary system with an orbital period of 7.753 days and a combined stellar classification of K3 V. Component B is a red dwarf star that orbits the primary pair every 290 years.


Alpha Mensae

α Mensae (Latinised as Alpha Mensae, abbreviated to α Men or Alpha Men) is the brightest star in the constellation Mensa. At a magnitude of 5.09, it is the dimmest lucida (a constellation's brightest star) in the sky. Due to its declination, on Earth it is best visible from higher latitudes of the southern hemisphere, yet can also be seen, though low in the sky, from just north of the Equator when near its daily arc's highest point, the culmination.
This star has a stellar classification of G7 V, indicating that it is a G-type main sequence star that is generating energy by fusing hydrogen into helium at its core. It is of similar size but slightly cooler than the Sun, with 110% of the mass, 99% of the radius, and 83% of the Sun's luminosity. The effective temperature of the stellar atmosphere is 5,587 K, and it has a slightly higher (112%) proportion of elements other than hydrogen and helium—what Astronomers call the star's metallicity—compared to the Sun. The estimated age of this star is 5.4 billion years, and is rotating at a relatively leisurely projected rotational velocity of 1.7 km/s.
Located about 33 light years distant from the Sun, Alpha Mensae has a relatively high proper motion across the sky. It has already made its closest approach to the Sun, coming within about around 250,000 years ago. A candidate infrared excess has been detected around this star, most which would indicate the presence of a circumstellar disk at a radius of over 147 AU. The derived temperature of this dust is below 22 K. However, data from Herschel Space Observatory failed to confirm this excess, leaving the finding in doubt. No planetary companions have yet been discovered around it. It has a red dwarf companion star at an angular separation of 3.05 arcseconds; equivalent to a projected separation of roughly 30 AU.


Kepler-7

Kepler-7 is a star located in the constellation Lyra in the field of view of the Kepler Mission, a NASA operation in search of Earth-like planets. It is home to the fourth of the first five planets that Kepler discovered; this planet, a Jupiter-size gas giant named Kepler-7b, is as light as styrofoam. The star itself is more massive than the Sun, and is nearly twice the Sun's radius. It is also slightly metal-rich, a major factor in the formation of planetary systems. Kepler-7's planet was presented on January 4, 2010 at a meeting of the American Astronomical Society.
Nomenclature and discovery.
Kepler-7 received its name because it was the home to the seventh planetary system discovered by the NASA-led Kepler Mission, a project aimed at detecting terrestrial planets that transit, or pass in front of, their host stars as seen from Earth. The planet orbiting Kepler-7 was the fourth planet to be discovered by the Kepler spacecraft; the first three planets combed from Kepler's data had been previously discovered, and were used to verify the accuracy of Kepler's measurements. Kepler-7b was announced to the public on January 4, 2010 at the 215th meeting of the American Astronomical Society in Washington, D.C. along with Kepler-4b, Kepler-5b, Kepler-6b, and Kepler-8b. Kepler-7b was noted for its unusually and extremely low density.
The planet's initial discovery by Kepler was verified by additional observations made at observatories in Hawaii, Texas, Arizona, California, and the Canary Islands.
Characteristics.
Kepler-7 is a sunlike star that is 1.347 Msun and 1.843 Rsun. This means that the star is about 35% more massive and 84% wider than the Sun. The star is estimated to be 3.5 (± 1) billion years old. It is also estimated to have a metallicity of [Fe/H] = 0.11 (± 0.03), meaning that Kepler-7 is approximately 30% more metal-rich than the Sun; metallicity plays a significant role in the formation of planetary systems, as metal-rich stars tend to be more likely to have planets in orbit. The star's effective temperature is 5933 (± 44) K. In comparison, the 4.6 billion-year-old Sun releases less heat, with an effective temperature of 5778 K.
The star has an apparent magnitude of 13, meaning that it is extremely dim as seen from Earth. It cannot be seen with the naked eye. It is estimated to lie at approximately 3090 light years from the Solar System.
There is a star that is 4 magnitudes dimmer located 1.90 arcseconds away, whether this a gravitationally bound companion star or a chance optical alignment is unknown.
Planetary system.
Kepler-7b is the only planet that has been discovered in Kepler-7's orbit. It is .433 MJ and 1.478 RJ, meaning it is 43% the mass of planet Jupiter, but is nearly three halves its size. With a density of .166 grams/cc, the planet is approximately 17% the density of water. This is comparable to styrofoam. At a distance of .06224 AU from its host star, Kepler-7b completes an orbit around Kepler-7 every 4.8855 days. Planet Mercury, however, orbits the Sun at .3871 AU, and takes approximately 87.97 days to complete one orbit. Kepler-7b's eccentricity is assumed to be 0, which would give Kepler-7b a circular orbit by definition.


HD 70930

HD 70930 is a binary star system in the southern constellation of Vela. It has the Bayer designation "B Velorum", while "HD 70930" is the star's identifier in the "Henry Draper catalogue". With a combined apparent visual magnitude of 4.79, it is visible to the naked eye as a faint point of light. The distance to this system is approximately 1,700 light years based on parallax, and it has an absolute magnitude of −3.74. It is drifting further away from the Sun with a radial velocity of about +27 km/s. The system is a member of the Vel OB2 association of co-moving stars.
The double nature of this system was discovered in 1896 by Scottish astronomer Robert T. A. Innes – it is now known to be a double-lined spectroscopic binary. The magnitude 5.14 primary component has a blue-white hue and has been assigned stellar classifications of B1V and B2III, matching a B-type main-sequence star or a giant star, respectively. It is a massive object – over 15 times the mass of the Sun – and is around 10 million years old. The star has a high rate of spin, showing a projected rotational velocity of 169 km/s. Its companion, at magnitude +6.08, is located at an angular separation of along a position angle of 139°, as of 2008.


LP Aquarii

LP Aquarii is a pulsating variable star in the constellation of Aquarius that varies between magnitudes 6.30 and 6.64.


NGC 6503

NGC 6503 is a field dwarf spiral galaxy located at the edge of a region of space called the Local Void. The dwarf galaxy spans 30,000 light-years and lies approximately 17 million light-years away in the constellation of Draco (the Dragon). The spiral galaxy is especially colorful where bright red regions of gas can be seen scattered through its spiral arms. Bright blue regions contain stars that are forming. Dark brown dust areas are in the galaxy's arms and center.


Omicron2 Cancri

Omicron2 Cancri (ο2 Cnc, ο2 Cancri) is a solitary, yellow-white hued star in the zodiac constellation of Cancer. With an apparent visual magnitude of +5.67, it can be viewed with the naked eye on a dark night. Based upon an annual parallax shift of 21.68 mas as seen from Earth, this star is located around 150 light years from the Sun. It most likely forms a co-moving pair with Omicron1 Cancri.
With a stellar classification of F0 IV, this is an F-type subgiant star that has left the main sequence and is evolving toward the giant stage. It is estimated to be roughly 300 million years old with a relatively high rotation rate, as shown by a projected rotational velocity of around 90.5 km/s. With 1.72 times the mass of the Sun and 1.62 times the Sun's radius, it is radiating 10.3 times the solar luminosity from its photosphere at an effective temperature of 7,868 K.
The star has an infrared excess, suggesting it surrounded by a circumstellar debris disk. Modelling of this structure indicates there are three distinct components, consisting of belts orbiting at distances of about 20 AU, 80 AU, and 270 AU from the central star. They are inclined at an angle of 64° to the line of sight along a position angle of 103°. The gaps between the belts are most likely maintained by orbiting planets.


Girl (Chinese constellation)

The Girl mansion (女宿, pinyin: Nǚ Xiù) is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise.


W Canis Majoris

W Canis Majoris (W CMa) is a carbon star in the constellation Canis Major. A cool star, it has a surface temperature of around 2,900 K and a radius 234 times that of the Sun, with a bolometric absolute magnitude of −4.13 and distance estimated at 443 or 445 parsecs (1,444–1,450 light-years) based on bolometric magnitude or radius. The Gaia Data Release 2 parallax of implies a distance of about 555 parsecs.
W CMa is classified as a slow irregular variable star. Detailed analyses have found only very weak and probably spurious periods of approximately a month. It is a carbon star, an asymptotic giant branch star where carbon and s-process elements have been dredged up to the surface during thermal pulses of the helium-burning shell.


AG Carinae

AG Carinae (AG Car) is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance (20,000 light-years) and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.
Description.
The star is surrounded by a nebula of ejected material at 0.4–1.2 pc from the star. The nebula contains around , all lost from the star around 10,000 years ago. There is an 8.8 pc wide empty cavity in the interstellar medium around the star, presumably cleared by fast winds earlier in the star's life.
AG Carinae is apparently in a transitional phase between a massive class O blue supergiant and a Wolf–Rayet star, where it is highly unstable and suffers from erratic pulsations, occasional larger outbursts, and rare massive eruptions. The spectral type varies between WN11 at visual minimum and an early A hypergiant at maximum. At visual minimum the star is about and 20,000–24,000 K, while at maximum it is and 8,000 K. The temperature varies at different minima.
One study calculated that the bolometric luminosity of AG Carinae decreases during the S Doradus outbursts, unlike most LBVs which remain at approximately constant luminosity. The luminosity drops from around at visual minimum to around at visual maximum, possibly due to the energy required to expand a considerable fraction of the star.
Evolutionary models of the star suggest that it had a low rotation rate for much of its life, but current observations show fairly rapid rotation.
Models of LBV progenitors of type IIb supernovae list AG Carinae as matching the final stellar spectrum prior to core collapse, although the models are for stars with 20 to 25 times the mass of the Sun while AG Carinae is thought to be considerably more massive. The initial mass of the star would have been around and is now thought to be .
Distance controversy.
Parallaxes from data release 1 (DR1) of the Gaia mission suggest a much closer distance to AG Carinae and its neighbour Hen 3-519 than previously accepted, around 2 kpc. Then both stars would be less luminous than LBVs and it is argued that they would be former red supergiants whose unusual characteristics are the result of binary evolution.
The earlier Hipparcos parallax for AG Carinae had a margin of error larger than the parallax itself and so gave little information about its distance. The distance of 6,000 pc is based on assumptions about the properties of LBVs, models of interstellar extinction, and kinematical measurements. The Gaia DR1 parallax, derived from the combination of the first year of Gaia measurements with Tycho astrometry, is . The Gaia team recommend that a further 0.3 mas systematic error is allowed for (i.e. added to the formal margin of error). A 2017 study argues that the 0.3 mas systematic margin of error can be ignored and that the implied distance to AG Carinae is .
In Gaia Data Release 2, the parallax is , suggesting a distance around . A 2019 observation yields a most likely distance of . Gaia Early Data Release 3 gives a parallax of , although with a non-trivial level of excess astrometric noise where there was none in Gaia DR2.


NGC 5003

NGC 5003 is a spiral galaxy in the constellation Canes Venatici. The celestial object was discovered on April 9, 1787, by the German-British astronomer William Herschel.


R Coronae Australis

R Coronae Australis (R CrA) is a variable binary system in the constellation Corona Australis. It has varied between magnitudes 10 and 14.36. A small reflection/emission nebula NGC 6729 extends from the star towards SE.
This star is moving toward the Solar System with a radial velocity of . It was previously believed that in roughly 222,000 years, this system could have approached within of the Sun. However, the estimate had a considerable margin of error in it. With the release of Gaia DR2, the star was determined to be 4 times further from the Sun than initially believed, constraining the approach to only .
A companion to the star was detected in 2019 with a mass between 0.1 and 1 Solar masses, depending on the characteristics of the stellar environment, orbiting the primary in 43–47 years.


NGC 5792

NGC 5792 is a barred spiral galaxy about 70 million light-years away in the constellation Libra. There is a magnitude 9.6 star on the northwestern edge of the galaxy. It was discovered on April 11, 1787 by the astronomer William Herschel.


37 Geminorum

37 Geminorum is a solitary Sun-like star located at the northwest part of the northern constellation of Gemini, about three degrees to the east of the bright star Epsilon Geminorum. The apparent visual magnitude of 37 Geminorum is 5.74, which is just bright enough to be visible to the naked eye on a dark night. It is located at a distance of 57 light years from the Sun based on parallax. This star is drifting closer with a radial velocity of −15 km/s, and is predicted to come as near as in approximately a million years. It is positioned close enough to the ecliptic to be subject to lunar occultations, such as happened on April 8, 1984.
The stellar classification of 37 Geminorum is G0 V, which indicates it is an ordinary G-type main sequence star that is generating energy through core hydrogen fusion. In 2007, J. C. Hall and associates categorized it as a solar-type with a high mean activity level. The star is around 5.5 billion years old and is spinning with a rotation period of 25 days. It is slightly larger and more massive than the Sun, with a lower abundance of heavier elements based on its abundance of iron. 37 Geminorum is radiating 1.3 times the luminosity of the Sun from its photosphere at an effective temperature of 6,060 K.
As of 2012, no extrasolar planets or debris disks have yet been discovered around it. The center of the star's habitable zone lies at a distance of .
Teen Age Message.
There was a METI message sent to 37 Geminorum. It was transmitted from Eurasia's largest radar, 70-meter Yevpatoria Planetary Radar. The message was named the Teen Age Message, it was sent on September 3, 2001, and it will arrive at 37 Geminorum in December 2057.
Catalog of Nearby Habitable Systems.
The Catalog of Nearby Habitable Systems (HabCat) is a list of approximately 17,000 relatively close stars similar to the sun and considered able to support a planet habitable by humans. 37 Geminorum is on the HabCat list.


NGC 5223

NGC 5223 is an elliptical galaxy in the constellation of Canes Venatici. It was discovered on 1 May 1785 by William Herschel.


NGC 2627

 NGC 2627 is an open cluster in the constellation Pyxis. Around 15 stars are visible when viewed through binoculars.


HL Tauri

HL Tauri (abbreviated HL Tau) is a very young T Tauri star in the constellation Taurus, approximately from Earth in the Taurus Molecular Cloud. The luminosity and effective temperature of imply that its age is less than 100,000 years. At apparent magnitude 15.1, it is too faint to be seen with the unaided eye. It is surrounded by a protoplanetary disk marked by dark bands visible in submillimeter radiation that may indicate a number of planets in the process of formation. It is accompanied by the Herbig–Haro object , a jet of gas emitted along the rotational axis of the disk that is colliding with nearby interstellar dust and gas.
Protoplanetary disk.
Indications of a protoplanetary disk were first presented in 1975 with infrared spectral observations in wavelengths between 2 and 4 microns, which were made possible by the recent invention of the indium antimonide photovoltaic detector. Of 29 very young stars examined, only showed a strong absorption feature centered on the expected 3.07 micron absorption of ice particles, which authors attributed to the ν1, ν3, and 2ν2 vibrational frequencies of the O–H bond. A 1982 survey identified as one of the most highly polarized stars known, along with DG Tauri and V536 Aquilae.
A gas disk was discovered by interferometric observation of carbon monoxide (CO) emissions in 1986. Based on observation data in 1985 and 1986 from the Millimeter Wave Interferometer of the Owens Valley Radio Observatory, the circumstellar disk was estimated to have a mass between and , with a best fit of , and a radius of about 200 AU. The temperature of the gas and grains of the disk are probably of the order of a few tens of kelvins. The gas was found to be bound to and in Keplerian rotation around a star with a mass of about . Bipolar outflow of molecules such as carbon monoxide (CO) and diatomic hydrogen (H2) have been observed. The element iron has also been noted in the outflow in its Fe(II) oxidation state, also called Fe2+ or "ferrous iron".
An image of the protoplanetary disk made at submillimeter wavelengths by the Atacama Large Millimeter/submillimeter Array (ALMA) was made public in 2014, showing a series of concentric bright rings separated by gaps. The disk appeared much more evolved than would have been expected from the age of the system, which suggests that the planetary formation process may be faster than previously thought. ALMA's Catherine Vlahakis said, "When we first saw this image we were astounded at the spectacular level of detail. HL Tauri is no more than a million years old, yet already its disc appears to be full of forming planets. This one image alone will revolutionize theories of planet formation."
Stephens "et al." (2014) suggest that the faster accretion rate might be due to the complex magnetic field of the protoplanetary disk.


Southern Crab Nebula

The Southern Crab Nebula (or WRAY-16-47 or Hen 2-104) is a nebula in the constellation Centaurus. The nebula is several thousand light years from Earth, and its central star is a symbiotic Mira variable - white dwarf pair. It is named for its resemblance to the Crab Nebula, which is in the northern sky.
The Southern Crab was noted in a 1967 catalog, and was also observed using a CCD imager with the 2.2 meter telescope at the La Sila observatory in 1989. The 1989 observation marked a major expansion of knowledge about the nebula, and it was observed using various filters.
The nebula had already been observed using Earth-based telescopes, but images taken with the Hubble Space Telescope in 1999 have provided much more detail, revealing that at the center of the nebula are a pair of stars, a red giant and a white dwarf. It was imaged again by HST in 2019 with a newer instrument.
In 1999 it was imaged by the Hubble Space Telescope's Wide Field and Planetary Camera 2, noted for its unique "stair-step" crop and for such astrophotos as the Pillars of Creation.
The WFPC2 images were taken at a optical light wavelength of 658 nm.
The nebula was imaged again by the Hubble Space Telescope in 2019, and a set of images to celebrate the anniversary of the space telescope's launch in 1990 (29 years) by the Space Shuttle. This time a newer camera the WFC3 was used to image the nebula, at wavelengths filters of about 502, 656, 658, and 673 nanometers.
The designation He2-104 (or Hen 2-104) comes from the Henize catalog of 1967, "Observations of Southern Planetary Nebulae". The catalog includes 459 items identified as planetary nebula (or likely as such). (note that in this meaning it does not imply exoplanets)
Another designation that it has been recorded for this object is WRAY-16-47.
In 2008, an investigation of the Southern Crab with its symbiotic (astronomical term) star was published. The study used imaging and spectroscopic data from space and Earth-surface telescopes including Hubble and VLT observatories. The ESO defines a symbiotic star system as "binaries in which a small hot star (white dwarf or main sequence star) orbits around a red giant star. These systems are often surrounded by an envelope of gas or dust; those with gas are known as S-types and those with dust as D-types."


Gliese 908

Gliese 908 is a red dwarf star, located in constellation Pisces at 19.3 light-years from Earth. It is a BY Draconis variable star with a variable star designation of BR Piscium. Its apparent magnitude varies between magnitude 8.93 and magnitude 9.03 as a result of starspots and varying chromospheric activity.
The variability of Gliese 908 was confirmed in 1994, although no period could be detected in its brightness changes. It was entered into the General Catalogue of Variable Stars in 1997.
Gliese 908 is a cool main sequence star, a red dwarf, with a spectral class of M1V Fe-1. The suffix indicates a noticeable deficiency in heavy elements.


NGC 4993

NGC 4993 (also catalogued as NGC 4994) is a lenticular galaxy located about 140 million light-years away in the constellation Hydra. It was discovered on 26 March 1789 by William Herschel and is a member of the NGC 4993 Group.
NGC 4993 is the site of GW170817, the first astronomical event detected in both electromagnetic and gravitational radiation, the collision of two neutron stars, a discovery given the Breakthrough of the Year award for 2017 by the journal "Science". Detecting a gravitational wave event associated with the gamma-ray burst provided direct confirmation that binary neutron star collisions produce short gamma-ray bursts.
Physical characteristics.
NGC 4993 has several concentric shells of stars and large dust lane with diameter of approximately a few kiloparsecs which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connected to a small dust ring with a diameter of ~. These features in NGC 4993 may be the result of a recent merger with a gaseous late-type galaxy that occurred about 400 million years ago. However, Palmese et al. suggested that the galaxy involved in the merger was a gas-poor galaxy.
Dark matter content.
NGC 4993 has a dark matter halo with an estimated mass of .
Globular clusters.
NGC 4993 has an estimated population of 250 globular clusters.
The luminosity of NGC 4993 indicates that the globular cluster system surrounding the galaxy may be dominated by metal-poor globular clusters.
Supermassive black hole.
NGC 4993 has a supermassive black hole with an estimated mass of roughly 80 to 100 million solar masses ().
Galactic nucleus activity.
The presence of weak O III, NII and SII emission lines in the nucleus of NGC 4993 and the relatively high ratio of [NII]λ6583/Hα suggest that NGC 4993 is a low-luminosity AGN (LLAGN). The activity may have been triggered by gas from the late-type galaxy as it merged with NGC 4993.
Neutron star merger observations.
In August 2017, rumors circulated regarding a short gamma-ray burst designated GRB 170817A, of the type conjectured to be emitted in the collision of two neutron stars. On 16 October 2017, the LIGO and Virgo collaborations announced that they had detected a gravitational wave event, designated GW170817. The gravitational wave signal matched prediction for the merger of two neutron stars, two seconds before the gamma-ray burst. The gravitational wave signal, which had a duration of about 100 seconds, was the first gravitational wave detection of the merger of two neutron stars.
An optical transient, (also known as SSS 17a), was detected in NGC 4993 11 hours after the gravitational wave and gamma-ray signals, allowing the location of the merger to be determined. The optical emission is thought to be due to a kilonova. The discovery of AT 2017gfo was the first observation (and first localisation) of an electromagnetic counterpart to a gravitational wave source.
GRB 170817A was a gamma-ray burst (GRB) detected by NASA's Fermi and ESA's INTEGRAL on 17 August 2017. Although only localized to a large area of the sky, it is believed to correspond to the other two observations, in part due to its arrival time 1.7 seconds after the GW event.


Zeta Cephei

Zeta Cephei (ζ Cep, ζ Cephei) is a star in the constellation of Cepheus. Zeta Cephei marks the left shoulder of Cepheus, the King of Joppa (Ethiopia). It is one of the fundamental stars of the MK spectral sequence, defined as type K1.5 Ib.
Zeta Cephei is an orange supergiant star with a surface temperature of 3,853 K and eight times more massive than the Sun. The luminosity of Zeta Cephei is approximately 3,600 times that of the Sun. At a distance of about 840 light-years, Zeta Cephei has an apparent magnitude ("m") of 3.4 and an absolute magnitude ("M") of -4.7. The star has a metallicity approximately 1.6 times that of the Sun; i.e., it contains 1.6 times as much heavy-element material as the Sun.
Hekker et al. (2008) have detected a periodicity of 533 days, hinting at the possible presence of an as yet unseen companion. It is listed as a possible eclipsing binary with a very small amplitude.
At the edge of the 8 to 10 solar mass () limit at which stars develop iron cores and then explode as supernovae, Zeta Cephei's most likely fate is to produce a very massive white dwarf near the Chandrasekhar limit (1.4 ) at which such dense remnants can survive. If Zeta Cephei "is" a binary star; i.e., if there "is" a stellar companion, and it is close enough to feed sufficient matter to the white-dwarf-to-be, it is marginally possible that the limit could be overflowed, resulting in the white dwarf's collapse and a Type Ia supernova explosion.


Gamma Virginis

Gamma Virginis (γ Virginis, abbreviated Gamma Vir, γ Vir), officially named Porrima , is a binary star system in the constellation of Virgo. It consists of two almost identical main sequence stars at a distance of about 38 light years.
Name.
"γ Virginis" (Latinised to "Gamma Virginis") is the star's Bayer designation.
The traditional name "Porrima" derives from Ancient Rome: Porrima, also known as Antevorta, was one of the Camenae or goddesses of prophecy. 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 "Porrima" for this star.
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Laouiyet al Aoua", which was translated into Latin as "Angulus Latratoris", meaning 'the angle of the barker'. This star, along with Beta Virginis (Zavijava), Eta Virginis (Zaniah), Delta Virginis (Minelauva) and Epsilon Virginis (Vindemiatrix), were "Al ʽAwwāʼ", the Barker.
In Chinese, (), meaning "Left Wall of Supreme Palace Enclosure", refers to an asterism consisting of Gamma Virginis, Eta Virginis, Delta Virginis, Epsilon Virginis and Alpha Comae Berenices. Consequently, the Chinese name for Gamma Virginis itself is (, .), representing (), meaning "The First Eastern Minister". 東上相 (Dōngshǎngxiāng), westernized into "Shang Seang" by R.H. Allen and the meaning is "the High Minister of State".
Properties.
Gamma Virginis is a binary star, consisting of two stars of nearly equal apparent magnitudes 3.65 and 3.56, and of spectral type F0V. With an orbital period of 168.93 years, it was an easy object for amateur astronomers until the beginning of the 1990s, but in 2011 the smaller apparent distance between the stars requires a larger telescope or special techniques such as speckle interferometry, adaptive optics or optical interferometry to resolve the individual components. The last time they were at periapsis was in 1836. The distance will again be wide enough in 2020 to view with a small telescope. The star system has a combined apparent magnitude of 2.9. The system is 39 light years away from the Sun.
Gamma Virginis is 2.8 degrees north of the ecliptic, so it can be occulted by the Moon and (rarely) by planets. In June 2011 Saturn passed a quarter of a degree south of Porrima.
Based upon X-ray emissions—an indicator of the strength of the stellar magnetic field—this system has an estimated age of 1.14 billion years.
Changes of distance and position angle.
This table shows the apparent distance between the two stars and their relative position angle: first three columns show data predicted from an orbit calculated in 1937, the next two columns show in 2006, the next three columns show observations reported by the Hanwell Community Observatory.


Pollux (star)

Pollux , designated β Geminorum (Latinised to Beta Geminorum, abbreviated Beta Gem, β Gem), is an orange-hued evolved giant star about 34 light-years from the Sun in the constellation of Gemini. It is the brightest star in Gemini and the closest giant star to the Sun.
Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. In 2006 an extrasolar planet (designated Pollux b or β Geminorum b, later named Thestias) was confirmed to be orbiting it.
Nomenclature.
"β Geminorum" (Latinised to "Beta Geminorum") is the star's Bayer designation.
The traditional name "Pollux" refers to the twins Castor and Pollux in Greek and Roman mythology. 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 "Pollux" for this star.
Castor and Pollux are the two "heavenly twin" stars giving the constellation Gemini (Latin, 'the twins') its name. The stars, however, are quite different in detail. Castor is a complex sextuple system of hot, bluish-white A-type stars and dim red dwarfs, while Pollux is a single, cooler yellow-orange giant. In Percy Shelley's 1818 poem "Homer's Hymn To Castor And Pollux", the star is referred to as "..mild Pollux, void of blame."
Originally the planet was designated Pollux b. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Thestias for this planet. The winning name was based on that originally submitted by theSkyNet of Australia; namely Leda, Pollux's mother. At the request of the IAU, 'Thestias' (the patronym of Leda, a daughter of Thestius) was substituted. This was because 'Leda' was already attributed to an asteroid and to one of Jupiter's satellites.
In the catalogue of stars in the "Calendarium of Al Achsasi Al Mouakket", this star was designated "Muekher al Dzira", which was translated into Latin as "Posterior Brachii", meaning "the end in the paw".
In Chinese, (), meaning "North River", refers to an asterism consisting of Pollux, ρ Geminorum, and Castor. Consequently, Pollux itself is known as (, .)
Physical characteristics.
At an apparent visual magnitude of 1.14, Pollux is the brightest star in its constellation, even brighter than its neighbor Castor (α Geminorum). Pollux is 6.7 degrees north of the ecliptic, presently too far north to be occulted by the moon and planets. Lunar occultations were possible as recently as about 2000 years ago. .
Parallax measurements by the Hipparcos astrometry satellite place Pollux at a distance of about from the Sun.
The star is larger than the Sun, with about two times its mass and almost nine times its radius. Once an A-type main sequence star, Pollux has exhausted the hydrogen at its core and evolved into a giant star with a stellar classification of K0 III. The effective temperature of this star's outer envelope is about , which lies in the range that produces the characteristic orange hue of K-type stars. Pollux has a projected rotational velocity of . The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is uncertain, with estimates ranging from 85% to 155% of the Sun's abundance.
Evidence for a low level of magnetic activity came from the detection of weak X-ray emission using the ROSAT orbiting telescope. The X-ray emission from this star is about 1027 erg s−1, which is roughly the same as the X-ray emission from the Sun. A magnetic field with a strength below 1 Gauss has since been confirmed on the surface of Pollux; one of the weakest fields ever detected on a star. The presence of this field suggests that Pollux was once an Ap star with a much stronger magnetic field. The star displays small amplitude radial velocity variations, but is not photometrically variable.
Planetary system.
Since 1993 scientists have suspected an extrasolar planet orbiting Pollux, from measured radial velocity oscillations. The existence of the planet, Pollux b, was confirmed and announced on June 16, 2006. Pollux b is calculated to have a mass at least 2.3 times that of Jupiter. The planet is orbiting Pollux with a period of about 590 days.