NGC 2438

NGC 2438 is a planetary nebula in the southern constellation of Puppis. Parallax measurements by Gaia put the central star at a distance of roughly 1,370 light years. It was discovered by William Herschel on March 19, 1786. NGC 2438 appears to lie within the cluster M46, but it is most likely unrelated since it does not share the cluster's radial velocity. The case is yet another example of a superposed pair, joining the famed case of NGC 2818.
This is a multi-shell planetary nebula with a bright inner nebula with a diameter of , consisting of two somewhat detached shells. It is expanding with a velocity of . The structure is surrounded by a fainter, mostly circular halo that is more visible on the western half, and has a diameter of . The mass of the main nebula is estimated at , while the shell has 0.5–. The main nebula has a temperature of about 10–13,000 K, rising to 15–17,000 K at the inner edge.
The nebula consists of material ejected from the central star during the asymptotic giant branch stage, beginning some 8,500 years ago. The main nebula was formed at about half that age. The central star of this planetary nebula is a 17.7-magnitude white dwarf, with surface temperature of about . It is one of the hottest stars known.


Gamma Caeli

The Bayer designation Gamma Caeli (γ Cae, γ Caeli) is shared by two star systems, in the constellation Caelum:
They are separated by 0.22° on the sky.


Mu Librae

μ Librae (Latinised as Mu Librae) is the Bayer designation for a probable triple star system in the zodiac constellation of Libra. They have a combined apparent visual magnitude of 5.32, which is bright enough to be faintly visible to the naked eye. With an annual parallax shift of 13.71 mas, the system is located at an estimated distance of around 240 light years.
The inner pair consists of two A-type stars that, as of 2006, had an angular separation of 1.79 arc seconds along a position angle of 5.5°. They have an estimated physical separation of 139 AU. The primary, component A, is a visual magnitude 5.69 magnetic Ap star showing overabundances of the elements aluminum, strontium, chromium, and europium. Hence, it has a stellar classification of A1pSrEuCr. It is a photometric variable with periods of and . The surface magnetic field strength is 1,375 Gauss.
The secondary, component B, is an Am star with a stellar classification of A6m. It has a visual magnitude of 6.72. The tertiary member, component C, is a magnitude 14.70 star at an angular separation of 12.90 arc seconds along a position angle of 294°, as of 2000.


NGC 4455

NGC 4455 is a spiral galaxy located in the constellation of Coma Berenices at an approximate distance of 28.06 Mly. NGC 4455 was discovered in 1785 by William Herschel.


Lambda Piscis Austrini

Lambda Piscis Austrini, Latinized from λ Piscis Austrini, is a solitary star in the southern constellation of Piscis Austrinus. It has a blue-white hue and is visible to the naked eye with an apparent visual magnitude of +5.42. Based upon an annual parallax shift of 6.51 mas as measured from Earth, it is located around 500 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.16 due to interstellar dust.
This is a B-type main sequence star with a stellar classification of B7 V. It has an estimated 3.58 times the mass of the Sun and about 4.2 times the Sun's radius. The star is spinning with a projected rotational velocity of 50 km/s and is 76% of the way through its main sequence lifetime. It is radiating 249 times the solar luminosity from its photosphere at an effective temperature of 12,023 K.
Lambda Piscis Austrini is moving through the Galaxy at a speed of 18.1 km/s relative to the Sun. Its projected Galactic orbit carries it between 23,800 and 29,300 light years from the center of the Galaxy.
Naming.
In Chinese, (), meaning "Palace Guard", refers to an asterism consisting of λ Piscis Austrini, 29 Aquarii, 35 Aquarii, 41 Aquarii, 47 Aquarii, 49 Aquarii, HD 212448, ε Piscis Austrini, 21 Piscis Austrini, 20 Piscis Austrini, υ Aquarii, 68 Aquarii, 66 Aquarii, 61 Aquarii, 53 Aquarii, 50 Aquarii, 56 Aquarii, 45 Aquarii, 58 Aquarii, 64 Aquarii, 65 Aquarii, 70 Aquarii, 74 Aquarii, τ2 Aquarii, τ1 Aquarii, δ Aquarii, 77 Aquarii, 88 Aquarii, 89 Aquarii, 86 Aquarii, 101 Aquarii, 100 Aquarii, 99 Aquarii, 98 Aquarii, 97 Aquarii, 94 Aquarii, ψ3Aquarii, ψ2Aquarii, ψ1Aquarii, 87 Aquarii, 85 Aquarii, 83 Aquarii, χ Aquarii, ω1 Aquarii and ω2 Aquarii. Consequently, the Chinese name for λ Piscis Austrini itself is (, .)


P Velorum

p Velorum (abbreviated to p Vel) is a triple star system in the constellation Vela. Parallax measurements by the Hipparcos spacecraft put it at a distance of 87.5 light-years, or 26.8 parsecs from Earth. It is visible to the naked eye with a combined apparent magnitude of 3.83.
The primary component is a spectroscopic binary whose components have an orbital period of 10.21 days. The inner spectroscopic binary consists of two F-type stars, a subgiant and a main-sequence star. There is a companion star which is a white A-type main-sequence star, with an apparent magnitude of 5.76. It is separated 0.361 arcseconds from the primary and has an orbital period of 16.651 years.


HD 56456

HD 56456 is a class B8.5V (blue main-sequence) star in the constellation Puppis. Its apparent magnitude is 4.76 and it is approximately 377 light years away based on parallax.
It has one companion, B, at magnitude 13.5 and separation 18".


NGC 3656

NGC 3656 is a peculiar galaxy formed by the collision of two galaxies in the constellation of Ursa Major. It is located about 135 million light years away from Earth, which means, given its apparent dimensions, that NGC 3656 is approximately 70,000 light years across. It was discovered by William Herschel on April 14, 1789.
Characteristics.
NGC 3656 is a galaxy merger, created by the collision of two disk galaxies. The merger has created shells around the galaxy and two faint tidal tails. The first tail emanates from a position angle of 260° and after bends to the north-northwest. Its total extent is about 180 arcseconds, towards a dwarf galaxy, and maybe even more, towards a second dwarf galaxy. Its width is 15 arcseconds. The other tail lies at the north-northeast part of the galaxy and isn't as well defined as the other. Other characteristics of the galaxy include the presence of a condensation at the south part of the galaxy connected with the rest of the galaxy with a ring-like feature and is associated with a bright shell.
A prominent feature of the galaxy is a dark lane running across the minor axis of the galaxy, similar to that observed in Centaurus A. At the centre of the galaxy a warped molecular gas disk extending for about 7 kiloparsecs has been observed in H I imaging, with an estimated mass of . The inner part of the disk features more intense star formation. The total star formation rate of the galaxy is estimated to be 1.1 per year.
The nucleus of NGC 3656 has been found to rotate around an axis that is almost perpendicular to the rotation axis of the rest of the galaxy, which is another indication of a galaxy merger.
Supernovae.
Two supernovae have been observed in the galaxy, SN 1963K, with a peak apparent magnitude of 15, and SN 1973C, with a peak apparent magnitude of 17. Both supernovae were not specified as far as their type was concerned.
Nearby galaxies.
NGC 3656 is the foremost member in a galaxy group known as the NGC 3656 group. Another member is UGC 6422. A bit further away lies the galaxy NGC 3549 with its group. Five dwarf galaxies with estimated masses between and have been detected in HI imaging around the galaxy and are probably in the process of being accreted by NGC 3656.


CoRoT-6

CoRoT-6 is a magnitude 13.9 star located in the Ophiuchus constellation.
Location and properties.
The star has a radius of about 102% of the Sun and a mass of about 110% of the Sun. It is a main sequence F type star a little larger and hotter than the Sun.
Planetary system.
The star is orbited by one known extrasolar planet identified as CoRoT-6b. The discovery was made by the CoRoT program using the transit method.


NGC 6002

NGC 6002 is a star located in the constellation Corona Borealis. It was discovered on 20 April 1873.


Iota Cygni

The Bayer designation Iota Cygni (ι Cyg / ι Cygni) is shared by two stars, in the constellation Cygnus:


Kepler-9

Kepler-9 is a sunlike star in the constellation Lyra. Its planetary system, discovered by the Kepler Mission in 2010 was the first detected with the transit method found to contain multiple planets.
Nomenclature and history.
Kepler-9 was named for the Kepler Mission, a project headed by NASA that was designed to search for Earth-like planets. Unlike stars such as Aldebaran or Sirius, Kepler-9 does not have a colloquial name.
In June 2010, some 43 days after Kepler came online, its operating scientists submitted a list of over 700 exoplanet candidates for review. Of those, five were originally suspected to have more than one planet. Kepler-9 was one of the multiplanetary systems; it was identified as such when scientists noticed significant variations in the time intervals at which Kepler-9 was transited. Kepler-9 holds the first multiplanetary system discovered using the transit method. It is also the first planetary system where transiting planets were confirmed through transit timing variations method, allowing to calculate the masses of planets. The discovery of the planets was announced on August 26, 2010.
Characteristics.
Kepler-9 is located in the constellation Lyra that lies some 620 parsecs away from Earth. With a mass of and a radius of , Kepler-9 is almost exactly the same size and width of the Sun, being only 7% more massive and 2% wider. Kepler-9 has an effective temperature of 5777 (± 61) K, as compared to the Sun's at 5778 K, and is approximately 32% more metal-rich (in terms of iron) than the Sun. Kepler-9 is younger than the Sun, and is estimated to be one billion years old.
Planetary system.
There are three confirmed planets, all in direct orbit. The outer two planets, Kepler-9b (the inner one) and Kepler-9c (the outer one), are low-density gas giants that are respectively 25% and 17% the mass of Jupiter and around 80% the radius of Jupiter. Both planets have a density less than that of water, similar to Saturn. The innermost planet, Kepler-9d, is a super-Earth with a radius that is 1.64 times that of Earth, orbiting the star every 1.6 days. It is estimated that there is a 0.59% chance that the discoveries are false.
From Kepler-9d (closest to star) to Kepler-9b (second from star), the ratio of their orbits is 1:12. However, the ratio of the orbits of the two outer planets is 1:2, a relationship known as a mean motion resonance. Kepler-9b and Kepler-9c are the first transiting planets detected in such an orbital configuration. The resonance causes the orbital speeds of each planet to change, and thus causes the transit times of the two planets to oscillate. The period of Kepler-9b is increasing by 4 minutes per orbit, while that of Kepler-9c is decreasing by 39 minutes per orbit. These orbital changes allowed the masses of the planets (a parameter not normally obtainable via the transit method) to be estimated using a dynamical model. The mass estimates were further refined using radial velocity measurements obtained with the HIRES instrument of the Keck 1 telescope.
Kepler-9b and 9c are thought to have formed beyond the "frost line". They are then thought to have migrated inward due to interactions with the remains of the protoplanetary disk. They would have been captured into orbital resonance during this migration.
In 2021, it was found the orbital plane of Kepler-9b and Kepler-9c are slowly changing, likely under the gravitational influence of the additional giant planet.


NGC 4665

NGC 4665, also catalogued as "NGC 4624" and "NGC 4664", is a barred lenticular or spiral galaxy located in the constellation Virgo. It is located at a distance of circa 60 million light years from Earth, which, given its apparent dimensions, means that NGC 4665 is about 75,000 light years across. NGC 4665 lies 2 and 3/4 degrees east-south east of Delta Virginis and 50 arcminutes southwest of 35 Virginis. It can be viewed through a telescope at a 23 magnification, forming a pair with an 11th magnitude star 1.5 arcminutes southwest. It is part of the Herschel 400 Catalogue.
It was discovered by William Herschel on February 23, 1784, however, he noted a location 10 arcminutes off the galaxy, where there is no object. It was observed by William Herschel again on April 30, 1786, noting the correct coordinates, and he misidentified it as another nebula. The fact that they are the same object was noted by John Louis Emil Dreyer in 1912 in the corrections of the New General Catalogue. It was also recorded independently on April 9, 1828 by John Herschel.
NGC 4665 has a luminous, slightly elliptical bulge and a prominent bar with high surface brightness. The isophotes appear boxy at the end of the bar. The total bar length is estimated to be near 3 kpc. The bar is slightly twisted, turning near 12 degrees along its axis. Two diffuse, faint arms emerge from each side of the bar and form a pseudoring. The surface brightness of the arms is higher near the bar. The southern arm appears a bit stronger. An arch feature is observed at the east side of the galaxy that could be a partial outer dusty ring. The outer isophotes are elliptical. The total mass of molecular gas is less than .
NGC 4665 belongs to the NGC 4636 group. Other members of the group include NGC 4457, NGC 4586, NGC 4587, NGC 4600, NGC 4636, and NGC 4688. These galaxies, along with NGC 4753, Messier 61 and their groups form the southern boundary of the Virgo cluster. It can be difficult to determine which galaxies belong to which group, especially around the southern edge of the Virgo cluster where there is a confusion of galaxies at different distances.


VV Corvi

VV Corvi (abbreviated as VV Crv) is a close spectroscopic binary in the constellation Corvus. It is also an eclipsing binary, varying from magnitude 5.19 to 5.34 over 3.145 days. The two stars orbit each other with a period of 1.46 days and an eccentricity of 0.088. The mass ratio of the two stars is 0.775±0.024. The primary is 1.978 ± 0.010 times as massive as the Sun, 18.253 ± 2.249 its luminosity and has 3.375 ± 0.010 the Sun's radius. The secondary is 1.513 ± 0.008 times as massive as the Sun, 4.745 ± 0.583 its luminosity and has 1.650 ± 0.008 the Sun's radius. Both are yellow-white main sequence stars of spectral type F5V, though the primary has begun expanding and cooling as it nears the end of its time on the main sequence. A tertiary companion was discovered during the Two Micron All-Sky Survey.
The system shares a common proper motion with HR 4822, which is 5"2 away.


TrES-3b

TrES-3b is an extrasolar planet orbiting the star GSC 03089-00929. It has an orbital period of just 31 hours and is undergoing orbital decay due to tidal effects. It has nearly twice the mass of Jupiter.
The planet TrES-3b is named Umbäässa. The name was selected in the NameExoWorlds campaign by Liechtenstein, during the 100th anniversary of the IAU. In the local dialect of southern Liechtenstein, Umbäässa is a small and barely visible ant.
Discovery.
It is the third transiting planet found by the Trans-Atlantic Exoplanet Survey. It was discovered in the constellation Hercules about 10 degrees west of Vega, the brightest star in the summer skies.
Transits in front of the star GSC 03089-00929 were detected by two 10 cm telescopes operating out of Palomar and Lowell Observatories. Transits of TrES-3 were also independently observed by the Hungarian Automated Telescope Network. Seven high-precision radial velocity measurements were made using the HIRES spectrometer at W. M. Keck Observatory, which confirmed the presence of a planetary mass companion with a minimum mass twice that of the planet Jupiter.
Characteristics.
The planet's home star is slightly smaller and cooler than the Sun. The orbital period is less than one and a third days, one of the shortest known. Despite of close proximity to the star, no evidence of tidal-driven orbital decay was present as in 2020, with best data fit indicating only an apsidal precession of planetary orbit.


Antinous (constellation)

Antinous is an obsolete constellation no longer in use by astronomers, having been merged into Aquila, which it bordered to the north.
The constellation was created by the emperor Hadrian in 132. Antinous was a beautiful youth loved by Hadrian, and also his erotic lover. Cassius Dio, having access to Hadrian's diary now lost, informs that Antinous died either by drowning or (as he himself believed) as a voluntary human sacrifice, something supported by Lambert (1984). The elevation to divinity meant that Antinous was to be a god in the heavens forever - Hadrian having named an asterism in the sky after him.
Tycho Brahe was originally given credit for inventing Antinous, but current finds include a celestial globe by the cartographer Caspar Vopel from 1536 that contains Antinous, so Brahe simply measured up the sky according to contemporary traditions and decided to give Antinous a separate table in his star catalogue.
In the following modern times, Antinous has been variously considered an asterism within Aquila or as a separate constellation, until the International Astronomical Union discarded it when formalizing the constellations in 1930.


RU Ursae Minoris

RU Ursae Minoris is a binary star system in the constellation Ursa Minor. Its apparent magnitude ranges from 10 to 10.66 over 0.52 days as one star passes in front of the other relative to observers on Earth.
Its component stars were calculated to be a primary star of spectral type F0IV/V and a secondary of spectral type K5V, both slightly more luminous than their spectral types indicate. The system is semidetached, as the secondary star is filling its Roche lobe and transferring matter to the primary. The primary is between 2.2 and 2.3 times as massive as the Sun, with 1.8 times its radius and around 8 times its luminosity. The secondary has around 0.72 times the Sun's mass, 1.1 times its radius and between 0.58 and 0.86 times its luminosity.
The period the two take to orbit each other is decreasing very slowly (by approximately 0.15 seconds per year), suggesting the components are moving closer and will become a contact binary.


Kepler-69

Kepler-69 ("KOI-172", "2MASS J19330262+4452080", "KIC 8692861") is a G-type main-sequence star similar to the Sun in the constellation Cygnus, located about from Earth. On April 18, 2013 it was announced that the star has two planets. Although initial estimates indicated that the terrestrial planet Kepler-69c might be within the star's habitable zone, further analysis showed that the planet very likely is interior to the habitable zone and is far more analogous to Venus than to Earth and thus completely inhospitable.
Nomenclature and history.
Prior to Kepler observation, Kepler-69 had the 2MASS catalogue number 2MASS J19330262+4452080. In the Kepler Input Catalog it has the designation of KIC 8692861, and when it was found to have transiting planet candidates it was given the Kepler object of interest number of KOI-172.
The star's planets were discovered by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits move in front of their stars from the perspective of Earth. The name Kepler-69 derives directly from the fact that the star is the catalogued 69th star discovered by "Kepler" to have confirmed planets.
The designations "b", "c" derive from the order of discovery. The designation of "b" is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet. In the case of Kepler-69, all of the known planets in the system were discovered at one time, so "b" is applied to the closest planet to the star and "c" to the farthest.
Stellar characteristics.
Kepler-69 is a G4 star that is approximately 81% the mass of and 93% the radius of the Sun. It has a surface temperature of 5638 ± 168 K. In comparison, the Sun has a surface temperature of 5778 K.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 13.7. Therefore, Kepler-69 is too dim to be seen with the naked eye.
Planetary system.
Kepler-69 has two known planets orbiting around it. Kepler-69b is a hot super-Earth-sized exoplanet. Kepler-69c is a super-Earth-sized exoplanet, about 70% larger than Earth. It receives a similar amount of flux from its star as Venus does from the Sun, and is thus a likely candidate for a super-Venus.


NGC 769

NGC 769 is a spiral galaxy located in the constellation Triangulum about 197 million light years from the Milky Way. It was discovered by the American astronomer Truman Safford in 1866.


DN Orionis

DN Orionis is an Algol variable located in the constellation of Orion. The primary star is a spectral type A2e star and the secondary star is a spectral type gF5 star.


26 Aurigae

26 Aurigae is a binary star system in the northern constellation of Auriga. It is visible to the naked eye as a faint star with an apparent visual magnitude of 5.41.
The distance to this system remains poorly constrained. The new Hipparcos reduction gives a parallax of . The original Hipparcos parallax was given as , leading to a distance of being assumed in many texts. A distance of has been derived from fitting the spectrum.
26 Aurigae is a visual binary system, and the two stars orbit each other every 52.735 years with an ellipticity of 0.653 and an angular separation . The system is made of a magnitude 6.29 G-type red giant, and a hotter magnitude 6.21 star that has been classified as an early B-type main-sequence star to an A-type subgiant star. Component A is the cool giant star, the brighter but less massive of the pair. The hotter star is sometimes listed as the primary on the basis of its stronger showing in the blended spectrum.


N44 (emission nebula)

N44 is an emission nebula with superbubble structure located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way in the constellation Dorado. Originally catalogued in Karl Henize's "Catalogue of H-alpha emission stars and nebulae in the Magellanic Clouds" of 1956, it is approximately 1,000 light-years wide and 160,000-170,000 light-years distant. N44 has a smaller bubble structure inside known as N44F. The superbubble structure of N44 itself is shaped by the radiation pressure of a 40-star group located near its center; the stars are blue-white, very luminous, and incredibly powerful. N44F has been shaped in a similar manner; it has a hot, massive central star with an unusually powerful stellar wind that moves at 7 million kilometers per hour. This is because it loses material at 100 million times the rate of the Sun, or approximately 1,000,000,000,000,000 tons per year. However, varying density in the N44 nebula has caused the formation of several dust pillars that may conceal star formation. This variable density is likely caused by previous supernovae in the vicinity of N44; many of the stars that have shaped it will eventually also end as supernovae. The past effects of supernovae are also confirmed by the fact that N44 emits x-rays.
N44 is classified as an emission nebula because it contains large regions of ionized hydrogen. However, the three strongest emission lines in the nebula are singly ionized oxygen atoms, which emit at an ultraviolet wavelength of 372.7 nm, doubly-ionized oxygen atoms, which emit at a blue-green wavelength of 500.7 nm, and neutral hydrogen atoms, which emit the hydrogen-alpha line at a red wavelength of 656.2 nm.


Theta Centauri

Theta Centauri (θ Centauri, abbreviated Theta Cen, θ Cen), officially named Menkent , is a star in the southern constellation of Centaurus, the centaur. With an apparent visual magnitude of +2.06, it is the fourth-brightest member of the constellation. Based on parallax measurements obtained during the Hipparcos mission, it is about distant from the Sun.
Nomenclature.
"θ Centauri" (Latinised to "Theta Centauri") is the star's Bayer designation.
It bore the traditional name of "Menkent" derived from an Arabic word for "shoulder" (of the Centaur) attached to the Latin abbreviation for "kentaurus" (centaur). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Menkent" for this star on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, (), meaning "arsenal", refers to an asterism consisting of Theta Centauri, Zeta Centauri, Eta Centauri, 2 Centauri, HD 117440, Xi¹ Centauri, Gamma Centauri, Tau Centauri, D Centauri and Sigma Centauri. Consequently, the Chinese name for Theta Centauri itself is (, ).
Properties.
This is an evolved giant star with a stellar classification of K0 III. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of about 10.6 times the radius of the Sun. The outer envelope has an effective temperature of 4,980 K, giving it the orange-hued glow of a cool, K-type star. Soft X-ray emission has been detected from this star, which has an estimated X-ray luminosity of .
References.
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V636 Scorpii

V636 Scorpii is a multiple star system in the constellation Scorpius, 3,000 light years away. The primary is a Classical Cepheid (δ Cephei) variable and its visual magnitude varies from 6.4 to 6.9.
V636 Scorpii is a spectroscopic binary, and the fainter companion is thought to itself consist of two stars. The primary is a luminous yellow star and a δ Cephei variable. The less massive companion orbits every 3.6 years and is apparently a B9.5 main sequence star, but the dynamics of the system suggest that it may actually be a pair of stars is a close orbit.
The Cepheid primary pulsates regularly with a period of 6.79671 days. It is a yellow-white supergiant or bright giant that is 5.6 times as massive as the Sun and 2,500 times as luminous.


Abell 39

Abell 39 is a low surface brightness planetary nebula in the constellation of Hercules. It is the 39th entry in George Abell's 1966 Abell Catalog of Planetary Nebulae (and 27th in his 1955 catalog) of 86 old planetary nebulae which either Abell or Albert George Wilson discovered before August 1955 as part of the National Geographic Society - Palomar Observatory Sky Survey. It is estimated to be about 6,800 light-years from earth and 4,600 light-years above the Galactic plane. It is almost perfectly spherical and also one of the largest known spheres with a radius of about 2.5 light-years.
Central star.
Its central star is slightly west of center by about 2″ or 0.1 light-years. This offset does not appear to be due to interaction with the interstellar medium, but instead, it is hypothesized that a small asymmetric
mass ejection has accelerated the central star. The mass of the central star is estimated to be about with the material in the planetary nebula comprising an additional .
This planetary nebula has a nearly uniform spherical shell. However, the eastern limb of the nebula is 50% more luminous than the western limb. Additionally, irregularities in the surface brightness are seen across the face of the shell. The source of the east–west asymmetry is not known but it could be related to the offset of the central star.
The central star is classified as a subdwarf O star.
Structure and composition.
The bright rim of the planetary nebula has an average thickness of about 10″.1 or about 0.34 light-years. There is a faint halo that extends about 18″ beyond the bright rim giving a complete diameter of around 190″ under the assumption that this emission is uniform around the planetary nebula.
This planetary nebula has been expanding for an estimated 22,100 years, based on an assumed expansion velocity between 32 and 37 km/s and a 0.78 parsec radius.
Background galaxies are visible near the nebula, and some can be seen through the translucent nebula.
Oxygen is only about half as abundant in the nebula as it is in our own sun.


Nu Telescopii

Nu Telescopii (ν Telescopii) is a solitary, white-hued star in the southern constellation of Telescopium. With an apparent visual magnitude of +5.35, it is faintly visible to the naked eye. There is a faint magnitude 9.3 companion star at an angular separation of 102 arc seconds along a position angle of 333°, as of 2010. The estimated distance to Nu Telescopii, based upon an annual parallax shift of 20.18 mas, is about 162 light years.
At the age of around 686 million years, Nu Telescopii shows the spectral characteristics of an evolving A-type star with a stellar classification of A7 III–IV. Here, the luminosity class of III–IV indicates mixed traits of a subgiant and a giant star. It has about 1.85 times the mass of the Sun and 2.1 times the Sun's radius. Based upon its motion through space, it is a candidate for membership in the IC 2391 supercluster.


Gliese 829

Gliese 829 is a double-lined spectroscopic binary system of two red dwarf stars in the constellation of Pegasus. They have a high proper motion of 1.08 arc seconds per year along a position angle of +69.58°. Based upon parallax measurements, the stars are at a distance of about 22 light years from the Sun. The system will make its closest approach to the Sun around 91,000 years from now when it achieves a perihelion distance of .
Characteristics.
The primary star has a temp of 3400 K. It is an M3.0Ve star with a B-V color index of 1.61 and it is also called Ross 775. It has an app. mag. of 10.35.


HD 34626

HD 34626, also known as MZ Aurigae, is an unusual variable star in the northern constellation of Auriga. It varies in brightness by 0.1 magnitude over time scales of 8 to 12 hours, but these variations are not periodic. This indicates the variability is not caused by ellipsoidal effects, and the nature of the variability remains unknown. It is a Be star and is rotating rapidly.


Theta Ophiuchi

Theta Ophiuchi (θ Oph, θ Ophiuchi) is a multiple star system in the equatorial constellation of Ophiuchus. It lies on the "right foot" of the serpent-bearer, just southwest of Kepler's Star, the nova of 1604. According to Richard H. Allen's, "" (1899), θ Oph together with ξ Oph formed the Sogdian "Wajrik" "the Magician", the Khorasmian "Markhashik" "the Serpent-bitten" and with η Oph the Coptic "Tshiō", "the Snake", and "Aggia", "the Magician". This star has an apparent visual magnitude of +3.26, making it readily visible to the naked eye. Based upon parallax measurements from the Hipparcos mission, it is roughly from Earth. It is 1.8 degrees south of the ecliptic.
Theta Ophiuchi appears to be a triple star system. The brightest component is a spectroscopic binary with an orbital period of 56.71 days and an eccentricity of 0.17. The third component is 5.5 magnitude star with a stellar classification of B5. Its angular separation from the binary pair is 0.15 arcseconds. This system is a proper motion member of the Upper Scorpius sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.
The primary component of this system is a variable star of the Beta Cephei type with a period of just 3h 22m. It has nearly nine times the mass of the Sun and more than six times the Sun's radius. Although only 21 million years old, it has begun to evolve away from the main sequence and has become a subgiant star with a stellar classification of B2 IV. This massive star is radiating around 5,000 times the luminosity of the Sun from its outer atmosphere at an effective temperature of about 22,260 K, giving it the blue-white hue of a B-type star.


IZ Aquarii

IZ Aquarii is a red giant star in the constellation Aquarius. It is a slow irregular variable that varies between magnitudes 6.23 and 6.47.


Phi Aurigae

Phi Aurigae, Latinized from φ Aurigae, is a giant star in the northern constellation of Auriga. It is faintly visible to the naked eye with an apparent visual magnitude of 5.089. It lies from another faint naked-eye star HD 35520, between the three open clusters M36 and M38, and NGC 1893.
The distance to this star, as determined from parallax measurements, is approximately with a 10 light-year margin of error. This is an evolved giant star with a stellar classification of K3 IIIp and an estimated radius equal to 16 times the radius of the Sun. The outer envelope has an effective temperature of 4,367 K, giving it the cool orange-hued glow of a K-type star.


Kepler-5

Kepler-5 is a star located in the constellation Cygnus in the field of view of the Kepler Mission, a NASA project aimed at detecting planets in transit of, or passing in front of, their host stars as seen from Earth. One closely orbiting, Jupiter-like planet, named Kepler-5b, has been detected around Kepler-5. Kepler-5's planet was one of the first five planets to be discovered by the Kepler spacecraft; its discovery was announced on January 4, 2010 at the 215th meeting of the American Astronomical Society after being verified by a variety of observatories. Kepler-5 is larger and more massive than the Sun, but has a similar metallicity, a major factor in planet formation.
Nomenclature and history.
Three discoveries made prior to the Kepler mission, which were in Kepler's field of view, were given the Kepler designations 1, 2 and 3. Kepler-5 is actually the second planet-bearing star discovered during the course of the Kepler Mission, a NASA operation that seeks to discover Earth-like planets that transit, or cross in front of, their host stars with respect to Earth. The star's planet, Kepler-5b, was therefore the second of the first five planets to be announced to the public on January 4, 2010 at the 215th meeting of the American Astronomical Society in Washington, D.C., along with planets around Kepler-4, Kepler-6, Kepler-7, and Kepler-8.
Kepler-5b's initial discovery by Kepler was re-examined by scientists at the W.M. Keck Observatory at Mauna Kea, Hawaii; the McDonald Observatory in west Texas; the Palomar and Lick Observatories in California; the MMT, WIYN, and Whipple Observatories in Arizona; and the Roque de los Muchachos Observatory in the Canary Islands.
Characteristics.
Kepler-5 is a sunlike star that is 1.374 (± 0.056) Msun and 1.793 (± 0.053) Rsun, and is 137% the mass of and 179% the radius of the Sun. The star has a metallicity of [Fe/H] 0.04 (± 0.06), making it approximately as metal-rich as the Sun, therefore increasing the star's likelihood to have planets in orbit. Kepler-5 has an effective temperature of 6297 (± 60) K, which is hotter than the Sun's effective temperature of 5778 K. Kepler-5 has an apparent magnitude of 13.4, and cannot be seen with the naked eye.
Companion stars.
A recent catalog of companions to Kepler stars determined from high-resolution imaging shows two companions to Kepler-5 at distances of 0.9 and 3.5 arc seconds. Whether these stars are physically bound to Kepler-5 or merely chance alignments of unrelated stars is unknown however recent studies have shown that 60 to 80% of companions within 1 arc second of Kepler stars are true binaries.
Planetary system.
Kepler-5b is 2.111 MJ and 1.426 RJ. It is, thus, more than twice the mass of Jupiter, and slightly less than three halves of Jupiter's radius. Kepler-5b orbits its star every 3.5485 days, lying at approximately 0.0538 AU from Kepler-5. It is, thus, a Hot Jupiter, or a gas giant that orbits near to its host star. To compare, Mercury orbits the sun at .3871 AU every 87.97 days. The planet's eccentricity is assumed to be 0, which is the eccentricity for a circular orbit.


36 Ophiuchi

36 Ophiuchi (or Guniibuu for A) is a triple star system 19.5 light years from Earth. It is in the constellation Ophiuchus.
The primary and secondary stars are nearly identical orange main sequence dwarfs of spectral type K2/K1; the tertiary star is an orange main sequence dwarf of spectral type K5.
Star C is separated from the A-B pair by 700 arc seconds, compared to a minimum of 4.6 arcsec for A-B, so its effect on the movements of the A-B pair is small. A and B have active chromospheres.
Nomenclature.
In the Kamilaroi and Euahlayi Aboriginal peoples in modern-day New South Wales, Australia, the star A is called "Guniibuu" that represents the robin red-breast bird ("Petroica boodang"). In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Guniibuu" for the star A on 10 August 2018 and it is now so included in the List of IAU-approved Star Names.
Hunt for substellar objects.
The McDonald Observatory team has set limits to the presence of one or more planets around 36 Ophiuchi A with masses between 0.13 and 5.4 Jupiter masses and average separations spanning between 0.05 and 5.2 astronomical units, although beyond 1.5 AU orbits are inherently unstable around either 36 Ophiuchi A or 36 Ophiuchi B.
The star C (or namely HD 156026) is among five nearby paradigms as K-type stars of a type in a 'sweet spot’ between Sun-analog stars and M stars for the likelihood of evolved life, per analysis of Giada Arney from NASA's Goddard Space Flight Center.


NGC 7752 and NGC 7753

NGC 7752 and NGC 7753 are a pair of galaxies approximately 272 million light-years away in the constellation Pegasus.
NGC 7753 is the primary galaxy. It is a barred spiral galaxy with a small nucleus. NGC 7752 is the satellite galaxy of NGC 7753. It is a barred lenticular galaxy that is apparently attached to one of NGC 7753's spiral arms. They resemble the Whirlpool Galaxy (M51A) and its satellite NGC 5195 (M51B).
Supernovae.
The first supernova detected in NGC 7753 was SN 2006A in January 2006. It was followed four months later by SN 2006ch, a Type Ia supernova. In January 2013 another Type Ia supernova, SN 2013Q, was detected, and in August 2015 a Type II supernova, SN 2015ae, was discovered.


NGC 6293

NGC 6293 is a globular cluster located in the constellation Ophiuchus. Its Shapley–Sawyer Concentration Class is IV. It was discovered by the American astronomer Lewis A. Swift on 8 July 1885. Like many other globular clusters, its distance is not well known; it may be anywhere from to light-years away from Earth.


Rho Ophiuchi cloud complex

The Rho Ophiuchi cloud complex is a dark nebula of gas and dust that is located 1° south of the star ρ Ophiuchi of the constellation Ophiuchus. At an estimated distance of , it is one of the closest star-forming regions to the Solar System.
Cloud complex.
This cloud covers an angular area of on the celestial sphere. It consists of two major regions of dense gas and dust. The first contains a star-forming cloud (L1688) and two filaments (L1709 and L1755), while the second has a star-forming region (L1689) and a filament (L1712–L1729). These filaments extend up to 10–17.5 parsecs in length and can be as narrow as 0.24 parsecs in width. Some of the structures within the complex appear to be the result of a shock front passing through the clouds from the direction of the neighboring Sco OB2 Association.
Temperatures of the clouds range from 13–22 K, and there is a total of about 3,000 times the mass of the Sun in the material. Over half of the mass of the complex is concentrated around the L1688 cloud, and this is the most active star-forming region. There are embedded infrared sources within the complex. A total of 425 infrared sources have been detected near the L1688 cloud. These are presumed to be young stellar objects, including 16 classified as protostars, 123 T Tauri stars with dense circumstellar disks, and 77 weaker T Tauri stars with thinner disks. The last 2 categories of stars have estimated ages ranging from 100,000 to a million years.
The first brown dwarf to be identified in a star-forming region was Rho Oph J162349.8-242601, located in the Rho Ophiuchi cloud. One of the older objects at the edge of the primary star-forming region was found to be a circumstellar disk seen nearly edge-on. It spans a diameter of 300 AU and contains at least twice the mass of Jupiter. The million-year-old star at the center of the disk has a temperature of 3,000 K and is emitting 0.4 times the luminosity of the Sun.


Sigma Cassiopeiae

Sigma Cassiopeiae (σ Cas, σ Cassiopeiae) is a binary star in the constellation Cassiopeia. It is approximately 5000 light years from Earth and has a combined apparent magnitude of +4.88.
The primary component, σ Cassiopeiae A, is a B2 subgiant with an apparent magnitude of +5.0. Its companion, σ Cassiopeiae B, is a B5 main sequence dwarf with an apparent magnitude of +7.1. The two stars are three arcseconds apart.
Naming.
In Chinese, (), meaning "Flying Serpent", refers to an asterism consisting of σ Cassiopeiae, α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for σ Cassiopeiae itself is (, ).


HD 92945

HD 92945 is a K-type main sequence star in the constellation of Hydra. Its apparent visual magnitude varies by 0.02 magnitudes and is approximately 7.72 at maximum brightness.
Debris disk.
In 2007, a debris disk with estimated dust mass 0.047 has been observed around the star by coronagraphic imaging, using the ACS and NICMOS instruments on the Hubble Space Telescope. It appears to extend 45 to 175 astronomical units from HD 92945.
The disk has a gap at radius 73 AU which may be carved by the planet, but no planet with mass exceeding 1-2 was observed in the gap.


Silvery River


List of stars in Perseus

This is the list of notable stars in the constellation Perseus, sorted by decreasing brightness.
Ambiguity.
Some sources, including Starry Night (planetarium software), an atlas, and a web site attribute the name 'Atik' to Zeta Persei instead of nearby Omicron Persei.


72 Leonis

72 Leonis is a single variable star in the zodiac constellation of Leo, located roughly 1,000 light years away from the Sun. It has the variable star designation FN Leonis; "72 Leonis" is the Flamsteed designation. In Chinese astronomy, 72 Leonis is called 虎賁, Pinyin: Hǔbēn, meaning "Emperor’s Bodyguard", because this star is marking itself and stands alone in the "Emperor’s Bodyguard" asterism, Supreme Palace enclosure mansion (see : Chinese constellation). It is dedicated to the memory of Julio Cubillas, who died in December 2020, by the White Dwarf Research Corporation.
This object is visible to the naked eye as a red-hued star with an apparent visual magnitude of 4.56. It is an evolved bright giant with a stellar classification of M3 IIb and was listed as a spectral standard star for that class. The star is classified as an irregular variable of type LC, ranging from Hipparcos magnitude 4.56 down to 4.64. It has a radius 162 to 179 times that of the Sun and radiates 5,407 times the Sun's luminosity at an effective temperature of around 3,734 K. The star is moving away from the Earth with a heliocentric radial velocity of 15 km/s.


Zeta Horologii

Zeta Horologii, Latinized from ζ Horologii, is a yellow-white hued binary star system in the southern constellation of Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 5.20. Based upon an annual parallax shift of 20.37 mas as seen from Earth, it is located around 160 light years from the Sun.
This system was determined to be a double-lined spectroscopic binary by J. H. Moore in 1911−12. The first orbital elements were published by J. Sahade and C. A. Hernández in 1964, who found it consisted of two F-type main sequence stars of probable stellar classifications F2 V and F5 V. The pair orbit each other with a period of 12.9274 days and an eccentricity of 0.25. The system displays an infrared excess at a wavelength of 24μm but not at 70μm, yielding a derived temperature of 260 K. This suggests a circumbinary debris disk orbiting at a distance of less than 4.8 AU from the star system.


Epsilon Scorpii

Epsilon Scorpii (ε Scorpii, abbreviated Eps Sco, ε Sco), formally named Larawag , is a star in the southern zodiac constellation of Scorpius. It has an apparent visual magnitude of +2.3, making it the fifth-brightest member of the constellation. Parallax measurements made during the Hipparcos mission provide an estimated distance to this star of around from the Sun.
Epsilon Scorpii has a stellar classification of K1 III, which indicates it has exhausted the supply of hydrogen at its core and evolved into a giant star. The interferometry-measured angular diameter of this star, after correcting for limb darkening, is , which, at its estimated distance, equates to a physical radius of nearly 13 times the radius of the Sun. Presently it is generating energy through the nuclear fusion of helium at its core, which, considering the star's composition, places it along an evolutionary branch termed the red clump. The star's outer atmosphere has an effective temperature of 4,560 K, giving it the orange hue of a cool K-type star.
ε Scorpii is classified as a suspected variable star, although a study of Hipparcos photometry showed a variation of no more than 0.01–0.02 magnitudes. It is an X-ray source with a luminosity of .
Nomenclature.
"ε Scorpii" (Latinised to "Epsilon Scorpii") is the star's Bayer designation.
The star bore the traditional name "Larawag" in the culture of the Wardaman people of the Northern territory of Australia, meaning "clear sighting". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name "Larawag" for Epsilon Scorpii on 19 November 2017 and it is now so included in the List of IAU-approved Star Names.
Patrick Moore introduced the name "Wei" as Chinese name for this star. However, this seems to be a misreading, as Chinese (, English "Tail") refers to an asterism (i.e. Chinese constellation) consisting of Epsilon Scorpii, Mu¹ Scorpii, Zeta¹ Scorpii and Zeta² Scorpii, Eta Scorpii, Theta Scorpii, Iota² Scorpii and Iota¹ Scorpii, Kappa Scorpii, Lambda Scorpii and Upsilon Scorpii. Consequently, the name for Epsilon Scorpii itself is (), which means "the Second Star of Tail".
In culture.
Epsilon Scorpii appears on the flag of Brazil, symbolising the state of Ceará.
References.
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Upsilon Lupi

Upsilon Lupi, Latinized from υ Lupi, is a star system in the southern constellation of Lupus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.37. Based upon an annual parallax shift of 8.02 mas as seen from Earth, it is located around 410 light years from the Sun. The two components of Upsilon Lupi share a common proper motion through space and most likely form a wide binary star system. As of 1945, the pair had an angular separation of 1.50 arc seconds along a position angle of 40°.
The brighter member, component A, is a chemically peculiar Ap star with a stellar classification of A0p Si, where the 'Si' suffix indicates an abnormal abundance of silicon in the star's photosphere. A magnetic field has been detected with a quadratic field strength of . The star is radiating 113 times the solar luminosity from its outer atmosphere at an effective temperature of 10,049 K.
The magnitude 10.9 companion star, component B, has a visual magnitude of 10.90. It may be the source of the X-ray emission detected coming from these coordinates.


HD 89744

HD 89744 is a star in the northern circumpolar constellation of Ursa Major, positioned about 0.4° due south of the bright star Tania Australis (μ UMa). This object has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.73. The distance to this star has been measured using the patallax method, which locates it 126 light years from the Sun. It is drifting closer with a radial velocity of −4.4 km/s. There are two known exoplanets orbiting this star.
At various times the star HD 89744 has been assigned a stellar classification of F7V, F7IV-V, and F8IV, suggesting it is an F-type main-sequence star that is evolving onto the subgiant branch. It is ~8.4 billion years old with an inactive chromosphere and is spinning with a projected rotational velocity of 9.3 km/s. The star is 2.16 times the size of the Sun with 1.4 times the Sun's radius. It is a high metallicity star, showing a greater abundance of heavier elements than in the Sun. The star is radiating 6.4 times the luminosity of the Sun from its photosphere at an effective temperature of 6,381 K.
In 2001, a faint co-moving companion was identified at an angular separation of from the primary. This is equivalent to a linear projected separation of . The companion, designated component B, is an L-class (~L0.5) brown dwarf with a mass of .
Planetary system.
In April 2000, a planet was discovered using radial velocity measurements taken at Fred Lawrence Whipple Observatory and Lick Observatory. The orbital parameters were updated in 2006 and 2007 using additional measurements. A second planet with a much longer period was discovered in 2019.


Kepler-453b

Kepler-453b is a transiting circumbinary exoplanet in the binary-star system Kepler-453. It orbits the binary system in the habitable zone every 240.5 days. The orbit of the planet is inclined relative to the binary orbit therefore precession of the orbit leads to it spending most of its time in a non-transiting configuration. By the time the TESS and PLATO spacecraft are available for follow up observations it will no longer be transiting.


CU Virginis

CU Virginis is a single star in the equatorial constellation of Virgo. It has an apparent visual magnitude of 4.99, which is bright enough to be faintly visible to the naked eye. The distance to this star can be estimated from its annual parallax shift of , yielding a separation of 234 light years.
This is one of the best studied Ap stars. It has a stellar classification of Ap Si with strong lines of silicon and weak helium lines. The star is a fast rotator with a period of 0.52 days and an axis that is inclined by to the line of sight from the Earth. Both the spectrum and luminosity of the star vary with the rotation, and it is classified as a α2 Canum Venaticorum variable with the designation CU Virginis (CU Vir). There is some evidence that the rotation period may vary slightly over a timescale measured in decades. Such changes have been observed to occur in glitches, rather than varying constantly.
CU Virginis has three times the mass of the Sun and double the Sun's radius. It is radiating 100 times the Sun's luminosity from its photosphere at an effective temperature of 12,750 K. The star has a strong magnetic field, placing it in the class of magnetic chemically peculiar stars. The polar magnetic field has a strength of about . The magnetic pole may be displaced by 87° from the axis of rotation, and the effective magnetic field is seen to vary over the course of a rotation. The mean surface magnetic field varies over the range .
This star is a radio emitter, with the emission being modulated by the rotational phase. This emission is believed to be "gyrosynchrotron radiation emitted by mildly relativistic (Lorentz factor of γ ≤ 2) electrons trapped in the magnetosphere". Two pulses of 100% circularly polarized radio energy are detected each rotation, which may be produced via an electron cyclotron maser process. These polarized beams are then refracted as they pass through cold plasma in the star's magnetosphere.


Iota Telescopii

ι Telescopii, Latinized as Iota Telescopii and abbreviated iot Tel, is a solitary star in the southern constellation of Telescopium. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of +4.89. The star is located approximately 347 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +22 km/s.
This object is an aging K-type giant star with a stellar classification of K0 III, which indicates it has exhausted the supply of hydrogen at its core then cooled and expanded. At present it has 19 times the radius of the Sun. It is radiating 157 times the Sun's luminosity from its swollen photosphere at an effective temperature of 4,680 K.


Delta Horologii

Delta Horologii (δ Horologii) is a binary star system in the constellation Horologium. It is visible to the naked eye with a combined apparent visual magnitude of 4.93. As of 2014, the pair had an angular separation of 0.20 arc seconds along a position angle of 24°. Based upon an annual parallax shift of 18.24 mas as seen from Earth, it is located 179 ± 4 light years from the Sun.
The primary, component A, is a magnitude 5.15 A-type main sequence star with a stellar classification of A9 V. At the estimated age of 768 million years, it is spinning rapidly with a projected rotational velocity of 220 km/s, giving the star an oblate shape with an equatorial bulge that is 15% larger than the polar radius. The star has 1.4 times the mass of the Sun.
The secondary has an apparent magnitude of 7.29.


List of stars in Cancer

This is the list of notable stars in the constellation Cancer. The 121 stars are sorted by decreasing brightness, beginning with Beta Cancri, the brightest star in Cancer.


Chi Scorpii

Chi Scorpii, Latinized from χ Scorpii, is a single star in the zodiac constellation of Scorpius. It has an orange hue and can be faintly seen with the naked eye with an apparent visual magnitude of 5.22. Based upon parallax measurements, this star is around 409 light years from the Sun. The star is drifting closer with a radial velocity of −23.6 km/s.
This is an aging K-type giant star with a stellar classification of K3 III, which means it has exhausted the supply of hydrogen at its core. There is a 57% chance that this evolved star is on the horizontal branch and a 43% chance it is still on the red-giant branch. If it is on the former, the star is estimated to have 1.09 times the mass of the Sun, nearly 27 times the solar radius and shines with 191 times the Sun's luminosity. It is around 8 billion years old.
Planetary system.
One superjovian planet orbiting Chi Scorpii was detected in 2020 on a mildly eccentric orbit utilizing a radial velocity method.


Nu Herculis

Nu Herculis, Latinized from ν Herculis, is a binary and variable star in the constellation of Hercules. With an apparent magnitude of about 4.4, it is faintly visible to the naked eye. Parallax measurements made by the Hipparcos spacecraft put it at a distance of about 860 light years (260 parsecs).
This is a binary system with the two components separated by . The secondary is nearly three magnitudes fainter than the primary at magnitude 7.5, and is hotter than the primary with a spectral type of B9.5.
Nu Herculis's spectral type of F2 II means that it is an F-type bright giant, with a luminosity 799 times that of the Sun. Its effective temperature is 6,410 K, hotter than the Sun. Its mass is about 5.3 solar masses. It is a possible semiregular variable star with a range of about a tenth of a magnitude. A period of 29 days has been derived.


Gamma Horologii

γ Horologii, Latinised as Gamma Horologii, is a solitary star in the southern constellation of Horologium. It is just bright enough to be visible to the naked eye as a dim, yellow-hued point of light with an apparent visual magnitude of +5.74. This object is located at a distance of 183 light years from the Sun, but is drifting closer with a radial velocity of −19 km/s.
The stellar classification of this object is G8 III/IV, matching a G-type star with a luminosity class intermediate between a subgiant and giant star. This suggests it has exhausted the supply of hydrogen at its core and is evolving off the main sequence. It has 5.5 times the radius of the Sun and is radiating 17 times the Sun's luminosity from its swelling photosphere at an effective temperature of 4,961 K. The metallicity is sub-solar, indicating a lower abundance of elements more massive than helium, as compared to the Sun.


Epsilon Leporis

Epsilon Leporis, Latinized from ε Leporis, is a third-magnitude star in the southern constellation Lepus. The apparent visual magnitude of +3.166 places it third in brightness among the stars in this constellation. Based upon parallax measurements, it is located at a distance of around from Earth.
This is an evolved giant star with a stellar classification of K4 III that has expanded to 40 times the Sun's radius. It is about 1.72 billion years old and has 1.70 times the mass of the Sun, with a luminosity 372 times as great. The outer atmosphere is cooler than the Sun's with an effective temperature of 4,131 K, giving it the orange hue of a K-type star. In terms of its composition, this star shows a similar abundance of elements other than hydrogen and helium to the Sun.
The envelope of this star is undergoing oscillations that show up as changes in the star's radial velocity. Over long durations these follow a linear trend, in combination with shorter period oscillations occurring over a few days. These oscillations are unlikely to be the result of rotational module as that would imply a high rotation rate, which would display itself through strong X-ray emissions. Instead, they may be the result of solar-like and Mira-like oscillations.


NGC 3998

NGC 3998 is a lenticular galaxy located in the constellation Ursa Major. It was discovered on April 14, 1789 by the astronomer William Herschel. At a distance of 45 million light-years (13.7 megaparsecs), it is located relatively nearby, making it a well-studied object.
In Gérard de Vaucouleurs' atlas of galaxy morphological types, NGC 3998 has a classification of SA00(r):, meaning it is unbarred and has an internal ring. It is classified as a LINER-type galaxy. As an early-type galaxy, NGC 3998's stars are relatively old and reddish in color, but its nuclear region may still have signs of star formation with stars less than 10 million years old. The galaxy's shape is very round, and also oblate.
Structure.
NGC 3998 contains an active galactic nucleus, or AGN. These are supermassive black holes that are surrounded by accretion disks that emit large amounts of energy across the electromagnetic spectrum. The supermassive black hole has been modeled to be about The AGN's power is relatively low, and like most other low-power radio galaxies, most of its emission is concentrated near its core. However, it also has some S-shaped lobes of emission, which are quite young and active, at only a few tens of millions of years old.
NGC 3998 has a small disk of ionized Hα radiation that is about 100 parsecs wide, along with a larger, warped disk of neutral hydrogen. It is thought that the gas disk has just started to align with the stellar distribution, which would also explain the warped shape of the radio emission.


AU Microscopii

AU Microscopii (AU Mic) is a young small star located about away – about 8 times as far as the closest star after the Sun. The apparent visual magnitude of AU Microscopii is 8.73, which is too dim to be seen with the naked eye. It was given this designation because it is in the southern constellation Microscopium and is a variable star. Like β Pictoris, AU Microscopii has a circumstellar disk of dust known as a debris disk and at least two exoplanets.
Stellar properties.
AU Mic is a young star at only 22 million years old; less than 1% of the age of the Sun. With a stellar classification of M1 Ve, it is red dwarf star with a physical radius of 75% that of the Sun. Despite being half the Sun's mass, it is radiating only 9% as much luminosity as the Sun. This energy is being emitted from the star's outer atmosphere at an effective temperature of 3,700 K, giving it the cool orange-red hued glow of an M-type star. AU Microscopii is a member of the β Pictoris moving group. AU Microscopii may be gravitationally bound to the binary star system AT Microscopii.
AU Microscopii has been observed in every part of the electromagnetic spectrum from radio to X-ray and is known to undergo flaring activity at all these wavelengths. Its flaring behaviour was first identified in 1973. Underlying these random outbreaks is a nearly sinusoidal variation in its brightness with a period of 4.865 days. The amplitude of this variation changes slowly with time. The V band brightness variation was approximately 0.3 magnitudes in 1971; by 1980 it was merely 0.1 magnitudes.
Planetary system.
The presence of the inner hole and asymmetric structure has led a number of astronomers to search for planets orbiting AU Microscopii. By 2007, no searches had led to any detections of planets. However, in 2020 the discovery of a Neptune-sized planet was announced. Its rotation axis is well aligned with the rotation axis of the parent star, misalignment being equal to 5°.
Since 2018, the second planet AU Microscopii c was suspected to exist. It was confirmed in December 2020, after additional transit events were documented by the TESS observatory.
Debris disk.
AU Microscopii harbors its own disk of dust, first resolved at optical wavelengths in 2003 by Paul Kalas and collaborators using the University of Hawaii 2.2-m telescope on Mauna Kea, Hawaii. This large debris disk faces the earth edge-on, and measures at least 200 AU in radius. At these large distances from the star, the lifetime of dust in the disk exceeds the age of AU Microscopii. The disk has a gas to dust mass ratio of no more than 6:1, much lower than the usually assumed primordial value of 100:1. The debris disk is therefore referred to as "gas-poor". The total amount of dust visible in the disk is estimated to be at least a lunar mass, while the larger planetesimals from which the dust is produced are inferred to have at least six lunar masses.
The spectral energy distribution of AU Microscopii's debris disk at submillimetre wavelengths indicate the presence of an inner hole in the disk extending to 17 AU, while scattered light images estimate the inner hole to be 12 AU in radius. Combining the spectral energy distribution with the surface brightness profile yields a smaller estimate of the radius of the inner hole, 1 - 10 AU.
The inner part of the disk is asymmetric and shows structure in the inner 40 AU. The inner structure has been compared with that expected to be seen if the disk is influenced by larger bodies or has undergone recent planet formation.
The surface brightness (brightness per area) of the disk in the near infrared formula_1 as a function of projected distance formula_2 from the star follows a characteristic shape. The inner formula_3 of the disk appear approximately constant in density and the brightness is unchanging, more-or-less flat. Around formula_4 the density and surface brightness begins to decrease: first it decreases slowly in proportion to distance as formula_5; then outside formula_6, the density and brightness drops much more steeply, as formula_7. This "broken power-law" shape is similar to the shape of the profile of β Pic's disk.
In October 2015 it was reported that astronomers using the Very Large Telescope (VLT) had detected very unusual outward-moving features in the disk. By comparing the VLT images with those taken by the Hubble Space Telescope in 2010 and 2011 it was found that the wave-like structures are moving away from the star at speeds of up to 10 kilometers per second (22,000 miles per hour). The waves farther away from the star seem to be moving faster than those close to it, and at least three of the features are moving fast enough to escape the gravitational pull of the star.
Methods of observation.
AU Mic's disk has been observed at a variety of different wavelengths, giving humans different types of information about the system. The light from the disk observed at optical wavelengths is stellar light that has reflected (scattered) off dust particles into Earth's line of sight. Observations at these wavelengths utilize a coronagraphic spot to block the bright light coming directly from the star. Such observations provide high-resolution images of the disk. Because light having a wavelength longer than the size of a dust grain is scattered only poorly, comparing images at different wavelengths (visible and near-infrared, for example) gives humans information about the sizes of the dust grains in the disk.
Optical observations have been made with the Hubble Space Telescope and Keck Telescopes. The system has also been observed at infrared and sub-millimeter wavelengths. This light is emitted directly by dust grains as a result of their internal heat (modified blackbody radiation). The disk cannot be resolved at these wavelengths, so such observations are measurements of the amount of light coming from the entire system. Observations at increasingly longer wavelengths give information about dust particles of larger sizes and at larger distances from the star. These observations have been made with the James Clerk Maxwell Telescope and Spitzer Space Telescope.


54 Aurigae

54 Aurigae is a binary star system located around away from the Sun in the northern constellation of Auriga. It is visible to the naked eye as a dim, blue-white hued star with a combined apparent visual magnitude of 6.02. The system is moving further from the Sun with a heliocentric radial velocity of around +19 km/s.
The primary component is a B-type giant star of visual magnitude 6.22 with a stellar classification of B7 III. This is a suspected variable star of unknown type with a measured amplitude of 0.02 in visual magnitude. It is radiating 315 times the luminosity of the Sun from its photosphere at an effective temperature of , and is spinning with a projected rotational velocity of . The secondary companion is a magnitude 7.82 star at an angular separation of along a position angle of 34° from the primary, as of 2008.


Kepler-34

Kepler-34 is an eclipsing binary star system in the constellation of Cygnus. Both stars have roughly the same mass as the Sun, therefore both are spectral class G. They are separated by 0.22 AU, and complete an eccentric (e=0.5) orbit around a common center of mass every 27 days.
Planetary system.
Kepler-34b is a gas giant that orbits the two stars in the Kepler-34 system. The planet is just over a fifth of Jupiter's mass and has a radius of 0.764 Jupiter radii. The planet completes a somewhat eccentric orbit every 288.822 days from a semimajor axis of just over 1 AU, the largest of any transiting planets at the time of its discovery. Such detection was possible as the planet transits both the stars, thus requiring fewer orbits to confirm the planet.
The majority of circumbinary planets were formed much further away from binary stars. In case of Kepler-34, Kepler-34b has likely the migrated to their current locations due interaction with the massive debris disk.
From the physical growth rate of planets and account data on collisions, it is found that Kelper-34b would have grown where we find it now.
Numerical simulation of formation of planetary system Kepler-34 has shown the formation of additional rocky planets in and near the habitable zone is unlikely.


RCW 49

RCW 49 is a H II region nebula located 13,700 light years away. It is a dusty stellar nursery that contains more than 2,200 stars and is about 350 light years across.
RCW 49 is recognized as among the brightest and most massive HII regions.
Other designations for the RCW 49 region include NGC 3247 and G29.
The nebula RCW49, shown in infrared light in this image from the Spitzer Space Telescope, is a nursery for newborn stars. Using NASA's Spitzer Space Telescope, astronomers have found in RCW49 more than 300 newborn or 'protostars,' all with circumstellar disks of dust and gas. The discovery reveals that galaxies make new stars at a much more prolific rate than previously imagined. The stellar disks of dust and gas not only feed material onto the growing new stars, but can be the raw material for new planetary systems.
In 2004 an image by the Spitzer Space Telescope in late 2003, was released showing the nebula in infrared wavelengths. This included and image showing the infrared colors mapped to visible light colors : 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red). It was noted as being almost 14 thousand light years from Earth, and the infrared light could detect the stars obscured by dust clouds. It was estimated at least 200 of the stars in the nebula have dust disks.
The results of observations of the Spitzer Telescope, including the IRAC camera, have been studied leading to the conclusion that the region is a star-forming region.
In 2014, RCW 49 was identified as a bow shock candidate, along with M17 in a study of Extended Red Objects (ERO's) and Stellar Wind Bow Shocks in the Carina nebula.


Delta Cancri

Delta Cancri (δ Cancri, abbreviated Delta Cnc, δ Cnc) is a double star about 180 light-years from the Sun in the constellation of Cancer.
Its two main constituents are designated Delta Cancri A and B. A is itself a binary star whose components are Delta Cancri Aa (formally named Asellus Australis , the traditional name of the entire system) and Ab.
The star system is 0.08 degree north of the ecliptic, so it can be occulted by the Moon and more rarely by planets; it is occulted (eclipsed) by the sun from about 31 July to 2 August. Thus the star can be viewed the whole night, crossing the sky at the start of February.
Nomenclature.
"δ Cancri" (Latinised to "Delta Cancri") is the system's Bayer designation. The designations of the two constituents "Delta Cancri A" and "B", and those of "A's" components - "Delta Cancri Aa" and "Ab" - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
It bore the traditional name "Asellus Australis" which is Latin for "southern donkey colt". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name "Asellus Australis" for the component Delta Cancri Aa on 6 November 2016 and it is now so included in the List of IAU-approved Star Names. Together with Gamma Cancri, it formed the "Aselli", flanking Praesepe.
As "Arkū-sha-nangaru-sha-shūtu", which means "the southeast star in the Crab", it marked the 13th ecliptic station of the ancient Babylonians.
In Chinese astronomy, "Ghost" () refers to an asterism consisting of Theta Cancri, Eta Cancri, Gamma Cancri and Delta Cancri. Delta Cancri itself is known as the fourth star of Ghost ().
Observations.
Delta Cancri was involved in the first recorded occultation by Jupiter:
Delta Cancri also marks the famous open star cluster Praesepe (or the Beehive Cluster, also known as Messier 44). In ancient times M44 was used as a weather gauge as the following Greek rhyme from Aratos' "Prognostica" reveals:
The meaning of this verse is that if Asellus Borealis or Gamma Cancris is hidden by clouds, the wind will be from the south and that situation will be reversed if Asellus Australis is obscured. There is some doubt however as to the accuracy of this as Allen notes: "Our modern Weather Bureau would probably tell us that if one of these stars were thus concealed, the other also would be." (Allen, 1898)
But Delta Cancri also acts as more than just a dubious weather guide: it is a reliable signpost for finding the vividly red star X Cancri as Patrick Moore notes in his guidebook "Stars of the Southern Skies":
Delta Cancri also marks the radiant of the Delta Cancrids meteor shower.
In 1876, the possibility of Delta Cancri having a companion star was proposed.


NGC 3073

NGC 3073 is a dwarf lenticular galaxy in the constellation Ursa Major. It is at a distance of about 65 million light-years (20 megaparsecs) from Earth. NGC 3073 was discovered by astronomer William Herschel on April 1, 1790. The galaxy belongs to the NGC 3079 Group.


NGC 408

NGC 408 is a star located in the constellation Pisces. It was discovered on October 22, 1867 by Herman Schultz. It was described by Dreyer as "very faint, very small, (WH) II 220 eight seconds of time to east.", WH II 220 being NGC 410.


H Centauri

H Centauri (H Cen), also known as V945 Centauri, is probable triple star system located in the constellation Centaurus. From parallax measurements, it is located 113 parsecs (370 light years) from the sun. It is a member of the Lower Centaurus-Crux (LCC) subgroup of the Scorpius–Centaurus Association.
This system is a double-lined spectroscopic binary formed by two B-type main-sequence star with spectral types B7V and B8.5V. They are in a close (but detached) circular orbit with a period of 0.6496 days and a separation of 5.63 solar radii. Observed at an inclination of 24°, the system is an ellipsoidal variable whose apparent visual magnitude varies from 5.14 to 5.17 over the course of an orbit as the star's visible surface area changes. The system's spectrum contains a third set of spectral lines that are probably from a third star, also of type B.


NGC 6905

NGC 6905, also known as the Blue Flash Nebula, is a planetary nebula in the constellation Delphinus. It was discovered by William Herschel in 1784. The central star is 14.0 mag. The distance of the nebula, as with most planetary nebulae, is not well determined and estimates range between 1.7 and 2.6 kpc.
The shape of NGC 6905 is characterised by an internal shell with angular dimensions 47" ×34" and roughly conical extensions, with ansae-type formations along the major axis. The nucleus of the nebula possesses one of the most broad emission of O emission lines among planetary nebulae. Moreover, O emission has been detected in NGC 6905. The ansae were particularly intense in N. The central star, a white dwarf is estimated to have a surface temperature of 150.000 K.
NGC 6905 can be detected under dark skies with a 4-inch telescope, but it better observed with larger instruments.


La Superba

La Superba (Y CVn, Y Canum Venaticorum) is a strikingly red giant star in the constellation Canes Venatici. It is a carbon star and semiregular variable.
Visibility.
La Superba is a semiregular variable star, varying by about a magnitude over a roughly 160-day cycle, but with slower variation over a larger range. Periods of 194 and 186 days have been suggested, with a resonance between the periods.
Y CVn is one of the reddest stars known, and it is among the brightest of the giant red carbon stars. It is the brightest of known J-stars, which are a very rare category of carbon stars that contain large amounts of carbon-13 (carbon atoms with 7 neutrons instead of the usual 6). The 19th century astronomer Angelo Secchi, impressed with its beauty, gave the star its common name, which is now accepted by the International Astronomical Union.
Properties.
The angular diameter of La Superba has been measured at . It is expected to be pulsating but this has not been seen in the measurements. At , this corresponds to a radius of . If it were placed at the position of the Sun, the star's surface would extend beyond the orbit of Mars.
La Superba's temperature is believed to be about , making it one of the coolest true stars known. It is faintly visible to the naked eye, and the red colour is very obvious in binoculars. When infrared radiation is included, Y CVn has a bolometric luminosity several thousand times that of the Sun. The mass of this type of star is difficult to determine; it would initially have been around and somewhat less now due to mass loss. An estimate from Jim Kaler gives the star a luminosity between and radius between based on an assumed temperature of 3,000 K, and the author then classified it as a C7 or CN5 supergiant star although its mass is too low to be a true supergiant.
Observations in the 60 and 100 micron infrared bands by the IRAS satellite showed that Y CVn is surrounded by a dust shell 0.9 parsecs in diameter.
 This is one of the most prominent circumstellar dust shells detected in the IRAS all-sky survey.
Evolution.
After stars up to a few times the mass of the sun have finished fusing hydrogen to helium in their core, they start to burn hydrogen in a shell outside a degenerate helium core, and expand dramatically into the red giant state. Once the core reaches a high enough temperature, it ignites violently in the helium flash, which begins helium core burning on the horizontal branch. Once even the core helium is exhausted, a degenerate carbon-oxygen core remains. Fusion continues in both hydrogen and helium shells at different depths in the star, and the star increases luminosity on the asymptotic giant branch (AGB). La Superba is currently an AGB star.
In the AGB stars, fusion products are moved outwards from the core by strong deep convection known as a dredge-up, thus creating a carbon abundance in the outer atmosphere where carbon monoxide and other compounds are formed. These molecules tend to absorb radiation at shorter wavelengths, resulting in a spectrum with even less blue and violet compared to ordinary red giants, giving the star its distinguished red color.
La Superba is most likely in the final stages of fusing its remaining secondary fuel (helium) into carbon and shedding its mass at the rate of about a million times that of the Sun's solar wind. It is also surrounded by a 2.5 light year-wide shell of previously ejected material, implying that at one point it must have been losing mass as much as 50 times faster than it is now. La Superba thus appears almost ready to eject its outer layers to form a planetary nebula, leaving behind its core in the form of a white dwarf.


Ophiuchus Superbubble

The Ophiuchus Superbubble is an astronomical phenomenon located in the Ophiuchus constellation, with a center around ℓ ≈ 30 °. This giant superbubble was first discovered in a 2007 study of extraplanar neutral hydrogen in the disk-halo transition of the Galaxy. The top extends to galactic latitudes over 25°, a distance of about 7 kpc. The Green Bank radio telescope has measured more than 220,000 HI spectra both in and around this structure.
Structure.
The movable 110 meter antenna of a radio telescope made it possible to take pictures of several neighboring regions of the sky, resulting in a folded mosaic in which an area filled with hydrogen was highlighted. Near this area the interstellar gas is disturbed and many ejections are evident.
The total mass of HI in the system is ≈ 106 M☉, with an equal mass of H+. The base of the structure consists of HI "whiskers" measuring several hundred pc wide and its halo extends over more than 1 kpc. The "whiskers" have a vertical density structure suggesting that they are the walls of the bubble and were created by a lateral rather than an upward movement. They resemble the vertical streaks of dust seen on NGC 891.
Geographical.
The superbubble is located 23 thousand light-years from the Earth, and the object itself is "raised" 10 thousand light-years above the plane of the galaxy.
According to the of an expanding bubble, the age of this system is ≈ 30 Ma, and its total energy content is ~ 10^53 erg. It may be at the stage when expansion stops and the shell begins to experience significant instabilities. This system offers an unprecedented opportunity to study several important phenomena at close range, including the evolution of superbubbles, turbulence in the HI shell, and the magnitude of the ionizing flux over the galactic disk.
Formation hypothesis.
The superbubble is hypothesized to be based on a massive cluster of young stars. The brightest of these stars exploded one after another, but since bright stars have a short lifespan (about 10 million years), a difference of a couple of million years essentially meant they all exploded at the same time. With a high degree of probability, the matter was "pushed" out of the galactic plane by such explosions, resulting in the inflation of the bubble. The interstellar matter itself is present in most galaxies and is mainly neutral or ionized hydrogen.
Such structures are capable of influencing the distribution of chemical elements in the galaxy: heavy nuclei that are born inside stars are ejected during an explosion together with gas, which - in the form of a "superbubble" - transports them over considerable distances.


NGC 293

NGC 293 is a barred spiral galaxy in the constellation Cetus. It was discovered on September 27, 1864 by Albert Marth.


NGC 409

NGC 409 is an elliptical galaxy located in the constellation Sculptor. It was discovered on November 29, 1837 by John Herschel. It was described by Dreyer as "extremely faint, small, round, very small (faint) star near."


BO Microscopii

BO Microscopii (BO Mic) is a star in the constellation Microscopium located about from the Sun. It has been dubbed "Speedy Mic" because of its very rapid rotation. The projected rotational velocity at the equator of this star is about , which, with an estimated inclination of 70° to the line of sight from the Earth, means it completes a rotation every . The photosphere of this star shows a high level of magnetic activity, with multiple star spots and prominences observed at the same time. As many as 25 prominences have been observed simultaneously, extending outward as far as 3.6 times the radius of the star. BO Mic is a flare star that undergoes sudden increases in X-ray and ultraviolet emissions. These events can emit a hundred times more energy than large solar flares. Speedy Mic is one of the most active stars in the vicinity of the Sun.


List of stars in Leo Minor

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


V957 Scorpii

V957 Scorpii is a variable star in the constellation of Scorpius. It is a blue straggler in the open cluster Messier 7, a star that is unexpectedly hot compared to other members of the cluster.
Spectrum.
V957 Scorpii shows a peculiar B5 or B6 spectrum. Its luminosity class has been given as main sequence (V), subgiant (IV), giant (III), and supergiant (Ib). From its position in the H-R diagram, it is actually thought to be a main sequence star. With a helium abundance 25 times lower than that of the sun, it is classified as helium-weak. It also has a low carbon abundance and a strong magnetic field.
Messier 7.
Messier 7 is a naked-eye open cluster. Except for one obvious orange giant star, its brightest members are mostly early A and late B main sequence stars and giants. Several of them are also chemically peculiar stars. However, two stars are hotter than the others and lie to the left of the isochrone for the cluster. These are the blue stragglers HD 162586 and V957 Scorpii. V957 Scorpii is considered 92% likely to be a member of M7. M7 has an age around 220 million years, but the apparent age of V957 Scorpii is less than 100 million years.
Variability.
V957 Scorpii varies in brightness by about 0.05 magnitudes. This is thought to be due to its rotation and variations in its surface brightness. It is classified as an SX Arietis variable, also known as helium variables. Their spectral lines also vary as the stars rotate.


Nu2 Canis Majoris

Nu2 Canis Majoris (ν2 Canis Majoris) is a single star in the southern constellation of Canis Major.
Characteristics.
With an apparent visual magnitude of 3.96, it is bright enough to be seen with the naked eye to the southwest of Sirius. It has an annual parallax shift of around 50.63 mas as seen from Earth, thus this system is about 64.4 light years from the Sun, a parallax well within the error margins of the figure later given by the Gaia space observatory data release 2, namely 50.471 ± 0.4168.
It is an evolved K-type giant around 4.6 billion years old. Around 1.3 times as massive as the Sun, it has expanded to around 4.9 times the Sun's diameter and 11 times its luminosity. In 2011, it was found to have a planet.
Chinese name.
In Chinese astronomy, ν2 Canis Majoris is called 野雞, Pinyin: Yějī, meaning "Wild Cockerel", because this star is marking itself and stand alone in "Wild Cockerel" asterism, Well mansion (see : Chinese constellation). 野雞 (Yějī), westernized into Ya Ke. According to R.H. Allen opinion, the name "Ya Ke" is asterism consisting ο1 Canis Majoris and π Canis Majoris, with other small stars in the body of the Dog
Planetary system.
By measuring periodic variations in the radial velocity of the host star between 2009 and 2010, the Pan-Pacific Planet Search program was able to identify a planet orbiting Nu2 Canis Majoris. An orbital fit produced a minimum mass estimate of with an orbital period of 2.1 years and an eccentricity of 0.23. Star spots were ruled out as a source for the signal with a false-alarm probability of 98.7%. Further observations through 2019 detected the planet, as well as a secondary planet c in a 4:3 orbital resonance with planet b.


List of stars in Virgo

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


Zeta Corvi

Zeta Corvi, Latinized from ζ Corvi, is a star in the constellation Corvus. It is a blue-white main sequence star of apparent magnitude 5.21. Located around 420 light-years distant, it shines with a luminosity approximately 154 times that of the Sun and has a surface temperature of 10,695 K. It is a Be star, the presence of hydrogen emission lines in its spectrum indicating it has a circumstellar disk. It is separated by 7 arcminutes from the star HR 4691. The two may be an optical double or a true multiple star system, with a separation of at least 50,000 astronomical units and the stars taking 3.5 million years to orbit each other. HR 4691 is itself double, composed of an ageing yellow-orange giant whose spectral type has been calculated at K0 or G3, and an F-type main sequence star.


SDC 335.579-0.292

SDC 335.579-0.292 is a dark nebula in the constellation of Norma. It is about 7.8 light-years (2.4 parsecs) in size. Its distance is poorly known, but it is thought to be about 10,000 light-years (3.25 kiloparsecs) away.
SDC 335.579-0.292 is a site where stars are forming. It is one of the most massive such star-forming regions known, with a total mass of over 5,500 solar masses. Inside, there are two massive star-forming cores, one of which has an estimated mass of 545 solar masses. It is thought to be a potential precursor to massive OB associations and massive star clusters, like the famous Trapezium Cluster. It is claimed to live a lifetime of barely a million years.


37 Leonis Minoris

37 Leonis Minoris is a single, yellow-hued star in the northern constellation of Leo Minor. It is faintly visible to the naked eye with an apparent visual magnitude of 4.68. The star is moving closer to the Sun with a heliocentric radial velocity of −8 km/s. The annual parallax shift of provides a distance estimate of roughly 580 light years.
The Bright Star Catalogue lists this star with a stellar classification of G2.5 IIa, indicating it is an evolved G-type bright giant. Gray et al. (2001) gave it a class of G1 II, while Keenan and McNeil (1989) assigned this star to the giant class G2.5 IIIa. It has an estimated 3.72 times the mass of the Sun and about 31 times the Sun's radius. The star is around 200 million years old with a projected rotational velocity of 6.4 km/s. It is radiating about 438 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 5,468 K.


Epsilon Sagittae

Epsilon Sagittae (ε Sagittae) is a solitary, yellow-hued star in the northern constellation of Sagitta. With an apparent visual magnitude of +5.64 to +5.67, it is faintly visible to the naked eye on a dark night. It is a variable star with a small amplitude of 0.03 magnitudes. Based upon an annual parallax shift of 5.60 mas as seen from Earth, it is located roughly 580 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.1 due to interstellar dust.
This is an evolved, G-type giant star with a stellar classification of G8 IIIvar, where the 'var' suffix indicates a variable spectral feature. The star is about 331 million years old with three times the mass of the Sun. It is radiating 185 times the Sun's luminosity from its photosphere at an effective temperature of 4,966 K.
Epsilon Sagittae is an optical binary, with a companion of magnitude 8.35 at an angular separation of 87.3 arc seconds along a position angle of 82°, as of 2013. The companion is actually a more distant giant star approximately 7,000 light-years from Earth, with a luminosity 1,800 times that of the Sun.


RX Leporis

RX Leporis ("RX Lep") is a star in the constellation of Lepus. It is a red giant and is a semi-regular pulsating star.
It has an apparent magnitude that varies from about 5 to 7.4. At its brightest it is dimly visible to the naked eye, and at its dimmest can be located with binoculars. In the sky it is about 4 degrees south of Rigel and is located next to Iota Leporis.


Centaurus X-3

Centaurus X-3 (4U 1118-60) is an X-ray pulsar with a period of 4.84 seconds. It was the first X-ray pulsar to be discovered, and the third X-ray source to be discovered in the constellation Centaurus. The system consists of a neutron star orbiting a massive, O-type supergiant star dubbed Krzeminski's star after its discoverer, Wojciech Krzemiński. Matter is being accreted from the star onto the neutron star, resulting in X-ray emission.
History.
Centaurus X-3 was first observed during experiments of cosmic X-ray sources made on May 18, 1967. These initial X-ray spectrum and location measurements were performed using a sounding rocket. In 1971, further observations were performed with the Uhuru satellite, in the form of twenty-seven 100-second duration sightings. These sightings were found to pulsate with an average period of 4.84 seconds, with a variation in the period of 0.02 seconds. Later, it became clear that the period variations followed a 2.09 day sinusoidal curve around the 4.84 second period. These variations in arrival time of the pulses were attributed to the Doppler effect caused by orbital motion of the source, and were therefore evidence for the binary nature of Centaurus X-3.
Despite detailed data from the Uhuru satellite as to the orbital period of the binary, and the pulsation period in the X-ray band as well as the minimum mass of the occulting star, the optical component remained undiscovered for three years. This was partly because Cen X-3 lies in the plane of the Galaxy in the direction of the Carina Spiral Arm, and so observations were forced to differentiate among dozens of faint objects. Centaurus X-3 was finally identified with a faint, heavily reddened variable star lying just outside the error box predicted by Uhuru observations. The visible star was later named after its discoverer, Poland astronomer Wojtek Krzemiński.
Centaurus X-3 was the first sources observed by the Russian x-ray telescope ART-XC. An image was released with the title "First Light Image of the Spektr-RG Observatory", showing the source imaged by the individual telescopes of ART-XC, as well as the light curve of Centaurus X-3 folded at its pulse period of 4.8s.
System.
Centaurus X-3 is located in the galactic plane about 5.7 kiloparsecs away, towards the direction of the Carina–Sagittarius Arm, and is a member of an occulting spectroscopic binary system. The visible component is Krzeminski's Star, a supergiant; the X-ray component is a rotating, magnetized neutron star.
X-ray component.
The X-ray emission is fueled by the accretion of matter from the distended atmosphere of the blue giant falling through the inner Lagrangian point, L1. The overflowing gas probably forms an accretion disc and ultimately spirals inwards and falls onto the neutron star, releasing gravitational potential energy. The magnetic field of the neutron star channels the inflowing gas onto localized hot spots on the neutron star surface where the X-ray emission occurs.
The neutron star is regularly eclipsed by its giant companion every 2.1 days; these regular X-ray eclipses last approximately 1/4 the orbital period. There are also sporadic X-ray off durations.
The spin period history of Centaurus X-3 shows a spin-up trend that is very prominent in the long term decrease in its pulse period. This spin-up was first noted in Centaurus X-3 and Hercules X-1 and is now noted in other X-ray pulsars. The most feasible way of explaining the origin of this effect is by a torque exerted on the neutron star by accreting material.
Krzeminski's Star.
Krzeminski's Star is a 20.5 solar mass (), slightly evolved hot massive star with a radius of and spectral type O6-7 II-III.
There is little doubt as to the correctness of the optical candidate, since it is in apparent agreement with the period and phase of Cen X-3, and exhibits the same similarity in its double wave and amplitude light curve seen in other known massive binary systems. The double wave ellipsoidal light variations are produced by a tidally deformed giant that nearly fills its Roche lobe. The visible component corresponds to an OB II class star, comparable with the mass derived from X-ray data, consistent with the minimum radius that has been fixed by X-ray eclipse duration.


NGC 3059

NGC 3059 is a barred spiral galaxy. It is located in the constellation of Carina. The galaxy can be described as being faint, large, and irregularly round. It was discovered on February 22, 1835 by John Herschel.


Rho Centauri

Rho Centauri, Latinized from ρ Centauri, is a binary star system in the southern constellation of Centaurus. It is visible to the naked eye as a blue-white hued point of light with a combined apparent visual magnitude of +3.97. The system is located approximately 276 light years from the Sun based on parallax, and is drifting further away with a radial velocity of around +15 km/s. It is a proper motion member of the Lower-Centaurus Crux sub-group in the Scorpius-Centaurus OB association, the nearest such association of co-moving massive stars to the Sun.
The primary component of this system is a B-type main-sequence star with a stellar classification of B3 V. It is about 24 million years old with a high rate of spin, showing a projected rotational velocity of 147 km/s. It has 6.6 times the mass of the Sun and 3.8 times the Sun's radius. The star is radiating 810 times the luminosity of the Sun from its photosphere at an effective temperature of 19,500 K.
The secondary companion is 1.1 magnitudes fainter than the primary, with a projected separation of along a position angle of 19.72°, as of 2013.


Alpha Lacertae

Alpha Lacertae, Latinized from α Lacertae, is a single white-hued star in the constellation of Lacerta, located 103 light years from the Sun. It is the brightest star in Lacerta with an apparent visual magnitude of 3.76. The star is moving closer to the Earth with a heliocentric radial velocity of −4.5 km/s.
This is an ordinary A-type main-sequence star with a stellar classification of A1 V, which indicates it is generating energy through hydrogen fusion at its core. It is around 400 million years old with a relatively high rate of spin, showing a projected rotational velocity of 128 km/s. The star has 2.2 times the mass of the Sun and 2.1 times the Sun's radius. It is radiating 28 times the Sun's luminosity from its photosphere at an effective temperature of 9,050 K.
Alpha Lacertae has a visual companion, CCDM J22313+5017B, of spectral type A and apparent visual magnitude 11.8, approximately 36 arcseconds away. The companion is optical, a chance line-of-sight coincidence.
Naming.
"Alpha Lacertae" is the Bayer designation for this star; it has the Flamsteed designation 7 Lacertae. In Chinese, (), meaning "Flying Serpent", refers to an asterism consisting of α Lacertae, 4 Lacertae, π2 Cygni, π1 Cygni, HD 206267, ε Cephei, β Lacertae, σ Cassiopeiae, ρ Cassiopeiae, τ Cassiopeiae, AR Cassiopeiae, 9 Lacertae, 3 Andromedae, 7 Andromedae, 8 Andromedae, λ Andromedae, κ Andromedae, ι Andromedae, and ψ Andromedae. Consequently, the Chinese name for α Lacertae itself is (, )


68 Draconis

68 Draconis is the Flamsteed designation for a star in the northern circumpolar constellation of Draco. It has an apparent visual magnitude of 5.69, so, according to the Bortle scale, it is faintly visible to the naked eye from suburban skies at night. Measurements made with the "Gaia" spacecraft show an annual parallax shift of , which is equivalent to a distance of around from the Sun. It is moving closer to the Earth with a heliocentric radial velocity of –14.6 km/s. The star has a relatively high proper motion, traversing the celestial sphere at a rate of per year.
The stellar classification of 68 Draconis is F5 V, indicating that it is a main sequence star that is fusing hydrogen into helium at its core to generate energy. The star appears to be over-luminous for a member of its class, being 0.73 magnitudes brighter than expected. This may indicate that this is a binary system with an unresolved secondary component. It has 15% more mass than the Sun but is less than half as old, with an estimated age of 1.7 billion years. The star is radiating 11 times the Sun's luminosity from its photosphere at an effective temperature of 6,137 K, giving it the yellow-white hue of an F-type star.


NGC 6584

NGC 6584 is a globular cluster in the constellation Telescopium that lies near Theta Arae and is 45000 light-years distant. It is an Oosterhoff type I cluster, and contains at least 69 variable stars, most of which are RR Lyrae variables: 46 stars were identified as RRab variables, 15 as RRc variables, 1 RRe variable, 4 eclipsing binaries and 3 long period variables. NGC 6584 is about 4 kpc from the Galactic center and about 2.7 kpc from the Galactic plane.
As is typical for metal-poor globular clusters, NGC 6584 has an enhanced concentration of alpha elements relative to iron.


Triangulum II

Triangulum II (Tri II or Laevens 2) is a dwarf galaxy close to the Milky Way Galaxy. It contains only 1000 stars, yet is quite massive, having a solar mass to light ratio of 3600. This is an unusually high mass for such a small galaxy.
The distance from the centre of the Milky Way is . The luminosity is 450 times that of the Sun. This makes it one of the dimmest known galaxies. The 2D half light radius is . The galaxy was discovered in images taken by Pan-STARRS by Benjamin P. M. Laevens in 2015.
Triangulum II is a candidate for detecting WIMPs as a source of dark matter.


NGC 6304

NGC 6304 is a globular cluster in the constellation Ophiuchus. William Herschel discovered this star cluster using an f/13 speculum reflector telescope in 1786. It is about 19,000 light-years away, near the Milky Way's central bulge.