Psi9 Aurigae

Psi9 Aurigae, Latinized from ψ9 Aurigae, is a star in the northern constellation of Auriga. It is dimly visible to the naked eye with an apparent visual magnitude of 5.75. Based upon an annual parallax shift of 2.59 mas, the distance to this star is approximately .
The spectrum of Psi9 Aurigae matches a giant star with a stellar classification of B8 IIIe. The 'e' suffix indicates this is a Be star that shows emission lines of hydrogen in its spectrum. This is caused by a circumstellar shell of hot gas. The emission undergoes variability on a time scale of sixteen years.


Upsilon Cassiopeiae

The Bayer designation Upsilon Cassiopeiae (υ Cas / υ Cassiopeiae) is shared by two star systems, in the constellation Cassiopeia:
They are separated by 0.3° on the sky.


Zeta Mensae

Zeta Mensae, Latinized from ζ Mensae, is a solitary, white-hued star in the southern constellation of Mensa. It is faintly visible to the naked eye, having an apparent visual magnitude of +5.64. Based upon an annual parallax shift of 8.2879 mas as seen from GAIA, it is located around 394 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.088 due to interstellar dust. Eggen (1995) listed it as a proper motion candidate for membership in the IC 2391 supercluster.
The stellar classification of A5 III suggests this is an A-type giant star. It is spinning rapidly, showing a projected rotational velocity of 200 km/s, giving the star an oblate shape with an equatorial bulge that is an estimated 26% larger than the polar radius. The star is radiating about 69 times the Sun's luminosity from its photosphere at an effective temperature of around 7,555 K. It displays a faint infrared excess at a wavelength of 18μm, indicating that it is being orbited by a debris disk.


R Geminorum

R Geminorum (R Gem) is a Mira variable and technetium star in the constellation Gemini. It is located approximately away.
R Geminorum pulsates with an average period of 369.9 days, varying by up to eight magnitudes at visual wavelengths. When at maximum light its apparent visual magnitude is usually between 6 and 7, while at minimum light it is typically near magnitude 14.
R Geminorum is one of the brightest known examples of an S-type star, a type that is similar to M-type star, but whose spectra shows zirconium oxide, yttrium oxide and technetium. These exotic elements are formed in the star's core. Technetium has a half-life of just 4.2 million years, so it must have been brought up from the core relatively recently. R Gem has an unusual amount of it, even for an S-type star.


NGC 240

NGC 240 is a lenticular or spiral galaxy located in the constellation Pisces. It was discovered on October 22, 1886 by Lewis Swift.


DI Herculis

DI Herculis is an Algol-type eclipsing binary star in the constellation of Hercules. The system has an apparent magnitude of about +8.5 and consists of two young blue stars of spectral type B5 and B4. It is about two thousand light years from Earth.
The orbit of the stars around their mutual centre of gravity is very elliptical, with an eccentricity of 0.489 and a semi-major axis of 0.201 astronomical units, resulting in an extremely close approach of the two stars at periastron.
Stellar masses of 5.15 and 4.52 solar masses lead to a theoretical precession of 4.27 degrees per century, at odds with the observed precession. However, detailed observations reveal an unexpectedly extreme obliquity of the spin axes of the two stars. One of the two stars is tipped over by at least 70 degrees from the vertical, and the other is tipped the opposite way by more than 80 degrees. Incorporating the effect of oblateness of the stars due to the unusually tilted axes, the predicted precession is consistent with general relativity.
Precession of periastron.
The precession of the periastron of the orbit of the stars serves as a test of the predictions of Einstein's general theory of relativity.
The known factors of the orbital distance of the stars, eccentricity, and stellar masses allows a theoretical prediction of precession of 4.27 degrees per century (1.93 degrees from classical effects and 2.34 degrees from general relativistic effects). However, the observed precession can be measured from eclipse timing, leading to an original measure of 1.04 degrees per century, and a more precise recent measurement of 1.39 degrees per century.
This discrepancy between theory and experiment has led to extensive studies of the bright binary system in the last thirty years; solutions discussed included
After observations of the Rossiter–McLaughlin effect in 2009, it emerged that the rotation axes of the two stars lay roughly in the orbital plane of the system. When this is taken account in calculating the rate of precession, the difference between expected and observed precession disappears; so DI Hercules is no longer a test case for a possible falsification of general relativity. However, a more recent research article shows that the 2009 study leaves many questions unanswered regarding the solution for the axes. For example, orbital effects caused by the tilting of the axes have not been observed; also, the stars' rotation axes themselves may also be precessing.


Tau Ophiuchi

Tau Ophiuchi (τ Oph) is a multiple star in the constellation Ophiuchus, approximately 167 light years away based on parallax. Its two main components are two yellow-white main sequence stars, A, of magnitude 5.24 and class F2V, and B, of magnitude 5.94 and class F5V, orbiting each other with a period of 257 years and eccentricity around 0.77. A is reported as a spectroscopic binary with a smaller star of 0.29 solar masses orbiting it every 186 days. An additional component, C, has a separation of 100.8" and magnitude 11.28.


Zeta Leporis

Zeta Leporis, Latinized from ζ Leporis, is a star approximately away in the southern constellation of Lepus. It has an apparent visual magnitude of 3.5, which is bright enough to be seen with the naked eye. In 2001, an asteroid belt was confirmed to orbit the star.
Stellar components.
Zeta Leporis has a stellar classification of A2 IV-V(n), suggesting that it is in a transitional stage between an A-type main-sequence star and a subgiant. The (n) suffix indicates that the absorption lines in the star's spectrum appear nebulous because it is spinning rapidly, causing the lines to broaden because of the Doppler effect. The projected rotational velocity is 245 km/s, giving a lower limit on the star's actual equatorial azimuthal velocity.
The star has about 1.46 times the mass of the Sun, along with 1.5 times the radius, and 14 times the luminosity. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is only 17% of the abundance in the Sun. The star appears to be very young, probably around 231 million years in age, but the margin of error spans 50–347 million years old.
Asteroid belt.
In 1983, based on radiation in the infrared portion of the electromagnetic spectrum, the InfraRed Astronomical Satellite was used to identify dust orbiting this star. This debris disk is constrained to a diameter of 12.2 AU.
By 2001, the "Long Wavelength Spectrometer" at the Keck Observatory on Mauna Kea, Hawaii, was used more accurately to constrain the radius of the dust. It was found to lie within a 5.4 AU radius. The temperature of the dust was estimated as about 340 K. Based on heating from the star, this could place the grains as close as 2.5 AU from Zeta Leporis.
It is now believed that the dust is coming from a massive asteroid belt in orbit around Zeta Leporis, making it the first extra-solar asteroid belt to be discovered. The estimated mass of the belt is about 200 times the total mass in the Solar System's asteroid belt, or . For comparison, this is more than half the total mass of the Moon. Astronomers Christine Chen and professor Michael Jura found that the dust contained within this belt should have fallen into the star within years, a time period much shorter than Zeta Leporis's estimated age, suggesting that some mechanism must be replenishing the belt. The belt's age is estimated to be years.
Solar encounter.
Bobylev's calculations from 2010 suggest that this star passed as close as 1.28 parsecs (4.17 light-years) from the Sun about 861,000 years ago. García-Sánchez 2001 suggested that the star passed 1.64 parsecs (5.34 light-years) from the Sun about 1 million years ago.


Kepler-440b

Kepler-440b (also known by its Kepler Object of Interest designation KOI-4087.01) is a confirmed super-Earth exoplanet orbiting within the habitable zone of Kepler-440, about from Earth. The planet was discovered by NASA's Kepler spacecraft using the transit method, in which the dimming effect that a planet causes as it crosses in front of its star is measured. NASA announced the confirmation of the exoplanet on 6 January 2015.
Confirmed exoplanet.
Kepler-440b is a super-Earth with a radius 1.86 times that of Earth. The planet orbits Kepler-440 once every 101.1 days.
Habitability.
The planet was announced as being located within the habitable zone of Kepler-440, a region where liquid water could exist on the surface of the planet.


HD 75063

HD 75063 is a single star in the southern constellation of Vela. It has the Bayer designation of "a Velorum", while "HD 75063" is the identifier from the "Henry Draper catalogue". This is a naked eye star with an apparent visual magnitude of 3.87 and has a white hue. The star is located at a distance of approximately 1,900 light years from the Sun based on parallax measurements and has an absolute magnitude of −4.89. It is drifting further away with a radial velocity of +23 km/s.
This object has been stellar classifications of A1III and A0 II, matching a massive A-type giant or bright giant star, respectively. It is an estimated 31 million years old and is spinning with a projected rotational velocity of 30 km/s. The star has 8.6 times the mass of the Sun and around 4.5 times the Sun's radius. The star is radiating 8,670 times the Sun's luminosity from its photosphere at an effective temperature of 8,023 K.


R Serpentis

R Serpentis is a Mira variable type star in the equatorial constellation of Serpens. It ranges between apparent magnitude 5.16 and 14.4, and spectral types M5e to M8e, over a period of 356.41 days. The variability of this star was discovered in 1826 by Karl Ludwig Harding.


EO Aurigae

EO Aurigae is an eclipsing binary of Algol type in the northern constellation of Auriga. With a combined apparent magnitude of 7.71, it is too faint to be seen with the unaided eye.
The eclipsing binary nature of the star was detected in 1943 by Sergei Gaposchkin at Harvard College Observatory. It consists of a pair of B-type main sequence stars orbiting each other with a period of 4.0656 days. During the eclipse of the primary star, the combined magnitude drops by 0.57; the eclipse of the secondary component drops the magnitude by 0.33.


Tau3 Serpentis

Tau3 Serpentis, Latinized from τ3 Serpentis, is a G-type giant star in the constellation of Serpens. It is approximately 410 light-years from Earth. It has an apparent visual magnitude of approximately 6.108.


HD 82943

HD 82943 (164 G. Hydrae) is a yellow dwarf star approximately 89 light-years away in the constellation of Hydra. Two extrasolar planets have been confirmed to be orbiting it, and it is thought that the system had more giant planets that were "swallowed" by the parent star. HD 82943 is estimated at roughly 1.15 times the mass of the Sun.
Planetary system.
The first planet discovered (designated HD 82943 b) was announced in 2000 by a team of French astronomers led by Michel Mayor. The planet orbits its parent star at a mean distance of 1.19 astronomical units (AU) and taking approximately 441 days to complete the orbit. Nearly a year later, a second planet (designated HD 82943 c) was announced by the same discoverers of the previous planet. This planet orbits closer than the other, at a mean distance of 0.746 AU and taking 219 days to complete its orbit. The two known planets appear to have a 2:1 resonance with one another. Further radial velocity analysis hinted at either long-period stellar activity or presence of a third Jovian planet with an orbital period of 1075 days.
Announced in 2001, HD 82943 was found to contain an unusually high amount of lithium-6. Stars do not naturally contain lithium-6, but unlike stars, planets never reach temperatures that are high enough to burn their initial content of lithium-6 (planets should retain lithium-6). The simplest and most convincing answer to explain this observation is that one or more planets, or at least planetary material, have fallen into the star, sometime after it passed through its early evolutionary stage.


24 Canum Venaticorum

24 Canum Venaticorum is a single star in the northern constellation of Canes Venatici, located 277 light years away from the Sun. This object is visible to the naked eye as a faint white-hued star with an apparent visual magnitude of +4.68. It is moving closer to the Earth with a heliocentric radial velocity of −18 km/s.
This is an A-type main-sequence star with a stellar classification of A4 V, and it is a shell star with rotationally-broadened lines. It is 310 million years old with a projected rotational velocity of 159 km/s. This rate of spin is giving the star an oblate shape with an equatorial bulge that is 7% larger than the polar radius. The star has 1.74 times the mass of the Sun and 1.9 times the Sun's radius. It is radiating 41 times the Sun's luminosity from its photosphere at an effective temperature of 8,285 K.
24 Canum Venaticorum displays a significant infrared excess at wavelengths of 24μm and 70μm, indicating an orbiting circumstellar debris disk. The signature matches a black body temperature of 464 K for an estimated orbital radius of .


NGC 805

NGC 805 is a lenticular galaxy approximately 194 million light-years away from Earth in the constellation of Triangulum. It was discovered by German astronomer Heinrich Louis d'Arrest on September 26, 1864 with the 11-inch refractor at Copenhagen.


NGC 3585

NGC 3585 is an elliptical or a lenticular galaxy located in the constellation Hydra. It is located at a distance of circa 60 million light-years from Earth, which, given its apparent dimensions, means that NGC 3585 is about 80,000 light years across. It was discovered by William Herschel on December 9, 1784.
NGC 3585 features a red discy region in the core with a semi-major axis of circa 45 arcseconds, probably associated with diffuse dust. There are nearly 130 globular cluster candidates in the galaxy, with the total number of globular clusters estimated to be nearly 550. This number is quite low, but it is typical for field elliptical galaxies. Based on luminosity turnover of the globular clusters, it is suspected that there is a subpopulation of younger clusters. The outer isophotes of the galaxy are asymmetrical, maybe due to a tidal disruption.
In the centre of NGC 3585 lies a supermassive black hole whose mass is estimated to be based on the tidal disruption rate or 108.53 ± 0.122 based on the observation of the circumnuclear ring with very-long-baseline interferometry. Based on observations by the Hubble Space Telescope to determine the stellar velocity dispersion at the core, the mass of the hole was estimated to be between 280 and 490 million by using the M–sigma relation.
NGC 3585 is the most prominent member of a loose galaxy group known as the NGC 3585 group. Other members of the group are the spiral galaxies UGCA 226, ESO 502- G 016, and UGCA 230.


Pi6 Orionis

Pi6 Orionis (π6 Ori, π6 Orionis) is a solitary star in the eastern part of the constellation Orion. It is visible to the naked eye with an apparent visual magnitude of 4.469. Based upon an annual parallax shift of 3.45 mas, it is around 950 light years from the Sun. At that distance, the visual magnitude of the star is reduced by an interstellar absorption factor of 0.52.
This is an evolved K-type giant star on the horizontal branch, with a stellar classification of K0/1 III. It is a suspected variable star with a measured variation between 4.45 and 4.49 in visual magnitude. Pi6 Orionis has over four times the mass of the Sun and has expanded to around 88 times the Sun's radius. Over the course of its life span, the star has shed around solar masses. With an effective temperature of 4,217 K in its outer atmosphere it is radiating roughly 2,200 times the solar luminosity.


Upsilon Piscis Austrini

Upsilon Piscis Austrini (υ Piscis Austrini) is a solitary, orange-hued star in the southern constellation of Piscis Austrinus. It is faintly visible to the naked eye with an apparent visual magnitude of +4.98. Based upon an annual parallax shift of 7.69 mas as seen from the Earth, the star is located 420 light-years from the Sun.
This is an evolved K-type giant star with a stellar classification of K4 III. It is catalogued as a member of the Wolf 630 moving group. Upsilon Piscis Austrini is moving through the galaxy at a speed of 36.4 km/s relative to the Sun. Its projected galactic orbit carries it between 17,700 and 25,400 light-years from the center of the galaxy.


Eta Pyxidis

Eta Pyxidis (η Pyxidis) is a solitary, white-hued star in the southern constellation of Pyxis. It is faintly visible to the naked eye with an apparent visual magnitude of +5.27. Based upon an annual parallax shift of 14.07 mas as seen from Earth, this star is located around 232 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an extinction factor of 0.07 due to interstellar dust.
This is an A-type main-sequence star with a stellar classification of A0 V. It is young with an age of around 67 million years and is spinning rapidly with a projected rotational velocity of 238 km/s. The star has 2.51 times the mass of the Sun and is radiating 42 times the Sun's luminosity from its photosphere at an effective temperature of around 11,614 K.


HD 42540

HD 42540, also known as HR 2196, is a suspected variable star in the constellation Pictor. A class K2-3III orange giant, its apparent magnitude is 5.04 and it is approximately 362 light years away based on parallax.


NGC 6786

NGC 6786 is an interacting spiral galaxy 350 million light years from the Earth, in the constellation of Draco. In 2004, a supernova occurred inside the galaxy. NGC 6786 is currently interacting with LEDA 62867, and, being the larger galaxy, it is likely that NGC 6786 will absorb LEDA 62867 in the future. Both galaxies appear to be undergoing a starburst, a phenomenon commonly seen among interacting and merging galaxies.


Lambda Coronae Australis

λ Coronae Australis, Latinized as Lambda Coronae Australis is a binary star system located in the southern constellation of Corona Australis. It is visible to the naked eye as a faint, white-hued point of light with an apparent visual magnitude of 5.11. The system is located at a distance of 205 light-years, based on parallax, and is drifting further away with a radial velocity of −26 km/s.
The primary member of this system, designated component A, is an A-type main-sequence star with a stellar classification of A0/1V. It is 273 million years old and is spinning with a projected rotational velocity of 149 km/s. This high rotation rate is producing an equatorial bulge that is 7% larger than the polar radius. It has 2.17 times the mass of the Sun and 2.24 times the Sun's radius. The star is radiating 31 times the Sun's luminosity from its photosphere at an effective temperature of 8,609 K.
The secondary companion, component B, has an apparent visual magnitude of 10.01 and a class of K0. As of 2016, it has an angular separation of from the primary along a position angle of 213°. Component C is a visual companion of magnitude 9.9 and separation from the primary.


G Scorpii

G Scorpii (abbreviated G Sco), also named Fuyue, is a giant star in the constellation of Scorpius. It has an apparent magnitude of +3.19. It is approximately 126 light-years from the Sun.
Nomenclature.
"G Scorpii" is the star's Bayer designation. It was formerly situated in the constellation of Telescopium where it was designated "γ Telescopii", Latinised to "Gamma Telescopii". It was resited in Scorpius and redesignated G Scorpii by Gould.
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 "Fuyue" for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
G Scorpii bore the traditional name "Fuyue" (）in ancient China. Fu Yue was a former slave that became a high-ranking minister to Shang dynasty ruler Wu Ding. G Scorpii is a member of the Tail mansion (, pinyin: ), one of the twenty-eight mansions of the Chinese constellations.
Properties.
G Scorpii is an orange K-type giant. The measured angular diameter is . At the estimated distance of this system, this yields a physical size of about 16 times the radius of the Sun. Calculations based on its physical properties give a diameter if about . With an effective surface temperature of , it has a bolometric luminosity of .
Evolutionary models show that G Scorpii has probably left the red giant branch and is now fusing helium in its core. This makes it a red clump star, at the cool end of the horizontal branch.
Just 5 arcminutes to the east is the globular cluster NGC 6441. At magnitude 3.2, G Scorpii is around 40 times brighter than the entire globular cluster.
References.
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NGC 446

NGC 446 is a lenticular galaxy of type (R)SAB0^0 located in the constellation Pisces. It was first discovered on October 23, 1864 by Albert Marth (and later listed as NGC 446); it was also seen on August 20, 1892 by Stéphane Javelle (and later listed as IC 89). It was described by Dreyer as "faint, very small, stellar."


Canopus (mythology)

In Greek mythology, Canopus or Canobus () was the pilot of the ship of King Menelaus of Sparta during the Trojan War. Canopus is described as a handsome young man who was loved by the Egyptian prophetess, Theonoe, but never reciprocated her feelings.
According to legend, while visiting the Egyptian coast, Canopus was bitten by a serpent and died. His master, Menelaus, erected a monument to him at one of the mouths of the River Nile, around which the town of Canopus later developed.
Also named for Canopus is Canopus, the brightest star in the southern constellation of Carina (the "keel" of the ship Argo), and the second-brightest star in the night sky, after Sirius.


Omicron Coronae Borealis

Omicron Coronae Borealis, Latinized from o Coronae Borealis, is a star in the northern constellation of Corona Borealis. It is a faint star but visible to the naked eye on a dark night with an apparent visual magnitude of +5.53. The annual parallax shift of the star as seen from Earth is 12.08 mas, which provides a distance estimate of around 270 light years. It is moving closer to the Sun with a radial velocity of −54 km/s.
Based upon the spectrum of this star, it has a stellar classification of K0 III. This indicates this is an evolved K-type giant star that has exhausted the hydrogen at its core and has left the main sequence. This is a red clump star, which means it is now generating energy through helium fusion at its core. It has 10% of the mass of the Sun and has expanded to over ten times the Sun's radius. The star is radiating 50 times the Sun's luminosity from its expanded photosphere at an effective temperature of 4,812 K.
Planetary system.
Omicron Coronae Borealis has one confirmed planet, believed to be, like HD 100655 b, one of the two least massive planets known around clump giants. The planet was detected by measuring changes in radial velocity of the host star caused by gravitational perturbation of the orbiting object. It is orbiting with a period of 188 days, at a semimajor axis 83% of the mean separation between the Earth and the Sun, and an eccentricity of 0.19.


Abell 33

Abell 33 is a planetary nebula located 2700 light years away in the constellation of Hydra. It lies just behind the star HD 83535. The star HD 83535 is also responsible for the "diamond ring" effect seen in the photograph.


NGC 436

NGC 436 is an open cluster located in the constellation Cassiopeia. It was discovered on November 3, 1787 by William Herschel. It was described by Dreyer as a "cluster, small, irregular figure, pretty compressed."


Upsilon2 Cancri

Upsilon2 Cancri (υ2 Cancri) is a faint, yellow-hued star in the zodiac constellation of Cancer. It is near the lower brightness limit of stars that can be viewed with the naked eye, having an apparent visual magnitude of +6.35. Based upon an annual parallax shift of 5.1325 mas as seen from our orbit, this system is roughly 635 light years away.
This is an evolved G-type giant star with a stellar classification of G9 III. It is radiating 98 times the Sun's luminosity from its photosphere at an effective temperature of 4,881 K. Upsilon2 Cancri is a member of the Epsilon Indi Moving Group of stars that share a common motion through space.


Pi4 Orionis

Pi4 Orionis (π4 Ori, π4 Orionis) is a binary star system in the western part of the Orion constellation. It is visible to the naked eye with an apparent visual magnitude of 3.7. Based upon an annual parallax shift of 3.1 mass, it is located roughly 1,050 light years from the Sun.
This is a spectroscopic binary star system with an orbital period of 9.5 days and an eccentricity of 0.03. The primary component is a B-type star with a stellar classification of B2 III. The stellar spectrum of π4 Ori A shows a strong depletion of the element boron. It has nearly 11 times the mass of the Sun and 9 times the Sun's radius. The star is 15.4 million years old and has a projected rotational velocity of 38 km/s. It shines with 19,726 times the solar luminosity from its outer atmosphere at an effective temperature of 21,874 k.


TW Pictoris

TW Pictoris is a cataclysmic variable star system located in the constellation Pictor.


C Ursae Majoris

c Ursae Majoris is the Bayer designation for a double-lined spectroscopic binary star system in the northern constellation of Ursa Major. It has an apparent visual magnitude of 5.20, which indicates that is visible to the naked eye. Parallax measurements yield an estimated distance of 64.1 light years from the Sun. The star is moving closer to the Earth with a heliocentric radial velocity of −14 km/s.
The spectroscopic binary nature of this system was among the first 75 such discovered by the Dominion Astrophysical Observatory in 1919. The pair orbit each other every 16.2 days with an eccentricity of 0.1. The semimajor axis of their orbit has an angle of around 2.9 mas, and the plane of the orbit is inclined to the line of sight at an angle of around 106°.
The primary component has a stellar classification of G0 V, suggesting that it is a G-type main sequence star similar to ι Per. It has a mass of about 1.2 times the mass of the Sun, and 2.6 times the Sun's radius. The magnitude difference between the two components is estimated to be . The estimated properties of the secondary indicate that it is most likely a K-type main sequence star. The system displays no indication of chromospheric activity.
The system has been examined for evidence of an infrared excess that could indicate the presence of a circumstellar debris disk, but none has been found. At present, c UMa is moving in Earth's direction with a radial velocity of −14.3 km/s. Perihelion passage will occur in 1.3 million years when the system comes within of the Sun. This is most likely a member of the Milky Way's thin disk population of stars.


NGC 6572

NGC 6572 is a planetary nebula with magnitude 8.1, easily bright enough to make it an appealing target for amateur astronomers with telescopes. NGC 6572 is a young planetary nebula. NGC 6572 began to shed its gases a few thousand years ago. Because of this, the material is still quite concentrated, which explains its abnormal brightness. The envelope of gas is currently racing out into space at a speed of around 15 kilometres per second. As it becomes more diffuse, it will dim. It is located within the large constellation of Ophiuchus (the Serpent Bearer) and at low magnification, it will appear to be just a colored star, but higher magnification will reveal its shape. NGC 6572 was discovered in 1825 by the German astronomer Friedrich Georg Wilhelm von Struve. According to several sources such as Sky & Telescope, this object received the nicknames Blue Racquetball, Emerald Nebula, Green Nebula, Turquoise Orb.


V509 Cassiopeiae

V509 Cassiopeiae (V509 Cas or HR 8752) is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae.
HR 8752 is around 15,700 light-years from Earth. It has an apparent magnitude that has varied from below +6 in historical times to a peak of +4.6 and now around +5.3 and is classified as a semiregular variable star of type SRd. It is undergoing strong mass loss as part of its rapid evolution and has recently passed partway through the yellow evolutionary void by ejecting around a solar mass of material in 20 years.
A hot main sequence companion (B1V) was described in 1978 on the basis of a colour excess in the ultraviolet.
Observations.
Brightness.
HR 8752 is a naked eye star but it has no Bayer or Flamsteed designation, and is not recorded in other catalogues before the 19th century. When first recorded in the Radcliffe Observatory catalogue in 1840 it was 6th magnitude, and it is assumed it had been 6th magnitude or fainter before then. The star is slightly variable on a timescale of around a year, but the average brightness increased steadily, reaching magnitude 5.0 in the 1950s.
The brightness climbed to magnitude 4.75 by 1973, but the exact onset of this event was not well observed. Since then the star has been studied much more closely. It peaked at magnitude 4.6 in 1976, then dropped quickly to magnitude 4.9 by 1979, then oscillated between magnitudes 4.75 and 4.85 for the next decade. Since then the brightness has generally decreased, with somewhat irregular variations of less than a tenth of a magnitude, to magnitude 5.3 in 2000 and may have stabilised at that level.
There are possible historical records of new stars in Cassiopeia that could correspond to earlier outbursts of HR 8752, but the association is highly speculative.
Spectrum.
Spectral types and colour comparisons for HR 8752 have been made regularly for over a century. The star was recognised as somewhat unusual and probably highly luminous, but not variable. It was actually proposed as a spectral standard for type G0Ia.
The colour of the star as measured by the difference between blue and visual magnitudes (B−V) may have decreased slightly from about 1.2 in 1900 to 0.8 in the 1960s. Measurements in different eras are not always calibrated to the same spectral bands, and the values have to be de-reddened to account for interstellar extinction, but the small change corresponds to records of the spectrum and are considered to be real. The colour then reddened dramatically to a B−V value of as much as 1.6 magnitudes in 1973, dropped rapidly to 0.02 by 2000, and has remained about constant since then. The detailed observations available since 1960 also show rapid colour variations of about 0.2 magnitudes on scales of 1–5 years super-imposed on the overall trends.
The spectral type over the same period has changed from a G0 hypergiant at the start of the 20th century, to early K in 1973, then rapidly back to G0 by 1977, continuing to reach A6 Ia+ in 2011. These spectral types are compatible with the observed colour changes, indicating changes in the temperature of the star or its dense winds. The spectrum contains nitrogen and helium emission lines with unusual P Cygni profiles, including "inverse P Cygni" and double-peaked line profiles. Forbidden NII lines and a triple-peaked Hα line have strengthened dramatically since 1993, and the profiles have also changed indicating developments in circumstellar material probably ejected from the star.
Properties.
It appears that HR 8752 is not just varying in brightness and fluctuating in temperature and size like most unstable stars, but is actually undergoing a secular evolutionary shift from cooler to hotter temperatures.
The temperature can be estimated with some accuracy from the spectral and colour observations. The calculated effective temperature increased from 4,500K in 1900 to 5,000K in 1960. At that stage the luminosity was around and the radius .
The star then varied erratically until 1973 when it rapidly expanded and cooled. A detailed spectral analysis in 1977 reported a temperature low of 4,000K, with a peak luminosity in 1976 of with a radius of . The surface gravity at this time was calculated to be log(g) = -2, indicating that the visible surface was effectively detached from the star. The star then rapidly returned to around its previous temperature of 5,000K, a luminosity of , and radius of .
Starting in 1985, HR 8752 began a startling change, increasing in temperature to around 8,000K and decreasing in size to by 2000, with a luminosity of . Since then the physical parameters have been more stable although the stellar wind continues to change. The surface gravity has returned to a more normal value for a luminous supergiant near log(g) = 1.0. This change means that in a few decades the star has passed through a region of instability on the H–R diagram where no stars are observed, an evolutionary change that has not been observed in any other star.
Elemental abundances derived from the spectrum indicate approximately solar metallicity, although some elements are enhanced due to the evolutionary state of HR 8752.
Evolutionary state.
Prior to 1973, HR 8752 was a cool yellow hypergiant with an early G spectral type. Following a dramatic shedding of its outer layers, it has now jumped to mid-A hypergiant and is not expected to return to its cool state. Models of a ZAMS star show it crossing the "yellow evolutionary void" instability region first towards cooler temperatures, then later back towards hotter temperatures. The yellow evolutionary void is named because very few stars are found in that part of the H–R diagram. This is likely to be because the evolution of stars with such parameters is extremely rapid, perhaps even almost instant in astronomical terms.
The first crossing of the yellow evolutionary void is very rapid but the star does not experience major instability. The second crossing, returning to hotter temperatures after a time as a yellow hypergiant, involves crossing a region, or possibly two regions, where the star experiences major instability, expected to show as episodes of strong mass loss. HR 8752 has crossed the first of the two major zones of instability and is expected to migrate to even hotter temperatures over a timescale on the order of a thousand years. Based on its current observed state, HR 8752 is estimated to now have left from an initial and is likely to become a relatively low-luminosity luminous blue variable before evolving further into a Wolf–Rayet star.
The ultimate fate of all massive stars is a core collapse and some sort of supernova explosion. Below about this is expected to occur as a type II supernova from a red supergiant progenitor. More massive stars evolve into Wolf–Rayet stars before exploding as a type Ib or Ic supernova. For some intermediate range of masses, stars are thought to undergo core collapse at the yellow hypergiant or LBV stage of their lives, resulting in a type IIb or perhaps IIn supernova. HR 8752 may be such a star, and may never make it beyond its current evolutionary state before exploding.
Possible binary.
HR 8752 may have a companion. Measurements of the ultraviolet spectral distribution show an excess that corresponds to the output of a B1 main-sequence star. The absolute magnitude was estimated at -4.5, approximately 40 times fainter than the primary at visual wavelengths. Although the stars must be fairly close (< 1400AU), no radial velocity variations have been detected in the spectral lines of the primary, and no lines are observed which can be attributed directly to the secondary. The observed spectrum may be mostly from a shell surrounding both stars. It has been suggested that some variations in spectral line profiles are caused by variations in colliding winds or disturbances of previously ejected material, caused during a periastron passage of the companion.


Iota Eridani

Iota Eridani (ι Eri) is a solitary star in the constellation Eridanus. It is visible to the naked eye with an apparent magnitude of 4.11. With an annual parallax shift of 0.02165 arcseconds, it lies at an estimated distance of about 151 light years.
This is an evolved red clump giant star with a stellar classification of K0 III. The measured angular diameter, after correcting for limb darkening, is . At an estimated distance of the star, this yields a physical size of around 11 times the radius of the Sun. It has 1.42 times the mass of the Sun and radiates 57.5 times the solar luminosity from its outer atmosphere at an effective temperature of 4,683 K. It is around four billion years old.
References.
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Eta Canis Minoris

Eta Canis Minoris (η CMi, η Canis Minoris) is a binary star system in the equatorial constellation of Canis Minor. It is approximately 318 light-years from Earth.
The primary component, η Canis Minoris A, is a yellow-white F-type giant with an apparent magnitude of +5.24. Its companion, η Canis Minoris B, is an eleventh-magnitude star located 4 arcseconds from the primary, though is actually around 440 AU from the main star and takes around 5,000 years to orbit it.


BPM 37093

BPM 37093 (V886 Centauri) is a variable white dwarf star of the DAV, or ZZ Ceti, type, with a hydrogen atmosphere and an unusually high mass of approximately 1.1 times the Sun's. It is about 50 light-years from Earth, in the constellation Centaurus, and vibrates; these pulsations cause its luminosity to vary. Like other white dwarfs, BPM 37093 is thought to be composed primarily of carbon and oxygen, which are created by thermonuclear fusion of helium nuclei in the triple-alpha process.
Structure.
In the 1960s, it was predicted that as a white dwarf cools, its material should crystallize, starting at the center. When a star pulsates, observing its pulsations gives information about its structure. BPM 37093 was first observed to be a pulsating variable in 1992, and in 1995 it was pointed out that this yielded a potential test of the crystallization theory. In 2004, Antonio Kanaan and a team of researchers of the Whole Earth Telescope estimated, on the basis of these asteroseismological observations, that approximately 90% of the mass of BPM 37093 had crystallized. Other work gives a crystallized mass fraction of between 32% and 82%. Any of these estimates would result in a total crystalline mass in excess of 5 kilograms. As the white dwarf has a radius of , this means that the core of BPM 37093, nicknamed "Lucy", is likely one of the largest diamonds in the local region of the universe.
Crystallization of the material of a white dwarf of this type is thought to result in a body-centered cubic lattice of carbon and/or oxygen nuclei, which are surrounded by a Fermi sea of electrons.


Pi Centauri

Pi Centauri, Latinized from π Centauri, is a binary star system in the southern constellation of Centaurus. It has a blue-white hue and is visible to the naked eye with a combined apparent visual magnitude of +3.90. The system is located at a distance of approximately 360 light years from the Sun based on parallax, and is drifting further away with a radial velocity of around +9 km/s. It is a member of the Lower Centaurus-Crux subgroup of the Scorpius–Centaurus Association.
The magnitude +4.08 primary, designated component A, is a B-type main-sequence star with a stellar classification of B5Vn, where the 'n' suffix indicates broad, diffuse (nebulous) lines due to rapid rotation. This star is spinning with a projected rotational velocity of 340 km/s, giving it an equatorial bulge that is 22% larger than the polar radius. It has 6.4 times the mass of the Sun and is radiating 783 times the Sun's luminosity from its photosphere at an effective temperature of 16,760 K.
The secondary companion, component B, is magnitude +5.65 with a class of B6V and 3.7 times the Sun's mass. The pair orbit around their common barycentre once every 39 years with an eccentricity of 0.8530. The semi-major axis of the companion is 0.23 arcseconds at an inclination of 19.4°.


NGC 266

NGC 266 is a massive barred spiral galaxy in the constellation Pisces. NGC 266 is located at a distance of from the Milky Way. It was discovered on September 12, 1784 by William Herschel. The form of this barred galaxy is described by its morphological classification of SB(rs)ab, which indicates a quasi-ring-like structure (rs) and moderate-to-tightly wound spiral arms (ab). It is the dominant member of a small group with six low-mass galaxies.
NGC 266 is an LINER-type active galaxy. It has a moderate star formation rate estimated at ·yr−1. A diffuse X-ray emission from hot gas has been detected around this galaxy, extending out to a radius of at least 70,000 light years. This emission not being driven by winds from a starburst region, so the root cause is unknown.
On October 12, 2005, a magnitude 16.8 supernova was discovered in NGC 266. It was positioned east and north of the galactic nucleus. An image of the galaxy taken on September 10 showed no supernova event, so this explosion occurred after that date. This event was designated SN 2005gl, and the progenitor was identified as a massive hypergiant star that was most likely a luminous blue variable.


Pi Ursae Minoris

The Bayer designation Pi Ursae Minoris (π UMi, π Ursae Minoris) is shared by two star systems, π1 Ursae Minoris and π2 Ursae Minoris, in the constellation Ursa Minor. They are separated by 0.64° on the sky.


NGC 5529

NGC 5529 is an edge-on intermediate spiral galaxy in the constellation Boötes. It is located approximately 144 million light-years (44 megaparsecs) away and was discovered by William Herschel on May 1, 1785.
NGC 5529 is an edge-on intermediate galaxy. It is located near dwarf galaxies PGC 50952, and PGC 50925.
Polycyclic aromatic hydrocarbons (PAHs) have been detected in the mid-infrared spectrum of NGC 5529. PAHs have been shown to only appear in galaxies with recent star formation.


Polophylax

Polophylax (Greek: "guardian of the celestial [south] pole") was a southern constellation that lay where Tucana and Grus now are.
It was introduced by Petrus Plancius in the small celestial planispheres on his large wall map of 1592. It is also shown on his smaller world map of 1594 and on world maps copied from Plancius.
It was superseded by the twelve constellations which Petrus Plancius formed in late 1597 or early 1598 from the southern star observations of Pieter Dircksz Keyser and Frederik de Houtman.


27 Cygni

27 Cygni is a subgiant star in the northern constellation of Cygnus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.38. The distance to this system, as estimated from its annual parallax shift of , is 78.1 light-years. At that distance, the visual magnitude is diminished by an extinction of 0.05 due to interstellar dust. It is moving closer to the Earth with a heliocentric radial velocity of −33 km/s, and has a relatively high proper motion, traversing the celestial sphere at the rate of per year.
27 Cygni is a G-type subgiant with a stellar classification of G8.5 IVa, a star that has used up its core hydrogen and is starting to expand. It was found to be slightly variable by Percy et al. (1986), changing by up to 0.05 in visual magnitude with a characteristic time scale of 50–60 days. Further observations suggested a possible rotation period of around 42 days. Samus et al. (2017) classify it as a suspected RS Canum Venaticorum variable, meaning that it is a close binary star whose components have star-spots that cause rotationally-modulated variations in brightness. It has been given the variable star designation V2008 Cygni.
27 Cygni is listed in multiple star catalogues with three faint companions within one arc-minute. The two closer ones are unrelated background objects, while the third has a similar distance and space motion and is described as a common proper motion companion.


Rho Lupi

Rho Lupi, Latinized from ρ Lupi, is a solitary star in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.05. Based upon an annual parallax shift of 10.32 mas as seen from Earth, it is located about 316 light years from the Sun. It is a member of the Upper Centaurus Lupus subgroup of the nearby Scorpius–Centaurus Association.
This is a B-type main sequence star with a stellar classification of B3/4 V. It is a microvariable with a period of 10.7 hours and an amplitude of 0.0046 in magnitude. With an age of just 44 million years, the star is spinning with a projected rotational velocity of 166 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 6% larger than the polar radius. It has an estimated 4.66 times the mass of the Sun and about 3.4 times the Sun's radius. It is radiating 365 times the solar luminosity from its outer atmosphere at an effective temperature of 15,947 K.


Chi Virginis

Chi Virginis (χ Vir, χ Virginis) is a double star in the constellation Virgo. Based upon parallax measurements, it is approximately from Earth. It has an apparent visual magnitude of 4.65, which is bright enough to be seen with the unaided eye under suitable viewing conditions.
This star has a stellar classification of K2 III, with the luminosity class "III" indicating that this is a giant star that has consumed the hydrogen at its core and evolved away from the main sequence. It has a mass about double that of the Sun and has expanded to 23 times the Sun's radius, giving it a luminosity of 182 times the luminosity of the Sun. The effective temperature of the star's outer envelope is about 4,395 K, which gives the star the orange hue typical of K-type stars. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is slightly higher than in the Sun.
This star has three optical companions. At an angular separation of 173.1 arcseconds is a magnitude +9.1 star, which is of spectral type K0. A 10th magnitude star is located 221.2 arcseconds away, and the third is a magnitude +9.1 K2 star 321.2 arcseconds away. None of these have been confirmed as a physical companion.
In July 2009, it was discovered that Chi Virginis has a massive planet with a high orbital eccentricity of 0.46. It is orbiting with a period of about 835 days and has a mass at least 11 times greater than Jupiter. There are indications of a second planet orbiting with a period of 130 days, but this has not been firmly established. But on 19 August 2015, the existence of a second planet, , (about three times bigger than Jupiter and having an orbit roughly that of Venus) was confirmed by Chilean astronomer Maritza Soto.


NGC 3239

NGC 3239 is an irregular galaxy in the constellation of Leo. It is the host of SN 2012A, the first supernova of 2012. The galaxy, which was discovered in 1784 by William Herschel, is part of the New Galactic Catalogue, and with an apparent magnitude of 13.5, is not visible to the naked eye. It has been shown to have many HII regions, while also having some star formation regions. These signs are common in galactic mergers, which is why it is believed that NGC 3239 is the result of a galactic merger. The supernova, SN 2012A, has been classified as a type IIP supernova, with a shorter plateau and non-constant luminosity.


G Centauri

G Centauri is a single star in the southern constellation of Centaurus. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of +4.82. This object is located approximately 450 light years from the Sun, based on parallax. It is a member of the Lower Centaurus Crux group of the Scorpius-Centaurus Association, with the former having an age of about 17 million years.
This object is a B-type main-sequence star with a stellar classification of B3V(n), where the 'n' indicates "nebulous" (broad) lines due to rapid rotation. It is around 16 million years old with a projected rotational velocity of up to 298 km/s. The star has six times the mass of the Sun and 3.4 times the Sun's radius. It is radiating 483 times the luminosity of the Sun from its photosphere at an effective temperature of 13,732 K. An infrared excess indicates a circumstellar disk of dust with a mean temperature of 50 K is orbiting the star at a separation of .


24 Sextantis

24 Sextantis, often abbreviated as 24 Sex, is the Flamsteed designation of a 7th-magnitude star located approximately 236 light years away in the constellation of Sextans. At an apparent visual magnitude of 6.61, this star can only be viewed from rural skies under good seeing conditions.
At the age of 2.8 billion years, it has reached an evolutionary stage called a subgiant star, having a stellar classification of K0 IV. Previously it was an A-type main sequence star before using up the hydrogen at its core. It has 54% more mass than the Sun, but the outer envelope has become cooler than the Sun's as it slowly expands into a giant star.
The star is known to have two giant extrasolar planets.
Planetary system.
On July 26, 2010 the California and Carnegie Planet Search team announced the discovery of two planets around 24 Sextantis along with two planets around HD 200964. The inner planet is twice as massive as Jupiter and takes 453 days to orbit the star in a circular orbit at the average distance of 1.33 AU (199 Gm). The outer planet is 5/6 the mass of Jupiter and takes 883 days to orbit eccentrically around the star at the average distance of 2.08 AU (312 Gm).
The two planets are in a 2:1 resonance, meaning that the outer planet orbits the star once every time when the inner planet orbits the star twice.
The planetary system was found to be unstable in 2019.


XO-4b

XO-4b is an extrasolar planet approximately 956 light years away in the constellation of Lynx. This planet was found by the transit method by McCullough in May 2008. The planet has mass and radius . This planet orbits very close to the F-type parent star, as it is typical for transiting planets, classing this planet as Hot Jupiter.
Orbit.
It takes only 4.125 days (or 99 hours) to orbit at a distance of 8.3 gigameters (0.0555 AU) away from the star.
The study in 2012, utilizing a Rossiter–McLaughlin effect, have determined the planetary orbit is strongly misaligned with the equatorial plane of the star, misalignment equal to -46.7°.
Naming.
The planet XO-4b is named Hämarik. The name was selected in the NameExoWorlds campaign by Estonia, during the 100th anniversary of the IAU. Hämarik is Estonian for dusk, and was named for a character in a folk tale written by Friedrich Robert Faehlmann.


Lambda Telescopii

λ Telescopii, Latinized as Lambda Telescopii, is a solitary, white-hued star in the southern constellation of Telescopium. It is visible to the naked eye as a faint point of light with an apparent magnitude of +4.87. This body is located approximately 610 light years from the Sun based on parallax. At that distance, the visual magnitude of the star is diminished by an extinction of 0.18 due to interstellar dust.
This is a late B- or early A-type main-sequence star that is generating energy through core hydrogen fusion. The star is 268 million years old with a relatively high rate of spin, showing a projected rotational velocity of 110. It has a higher than solar metallicity – the abundance of elements more massive than Helium. The star is radiating 350 times the Sun's luminosity from its photosphere at an effective temperature of 10,139 K.


Lambda Canis Majoris

Lambda Canis Majoris (λ Canis Majoris) is a solitary, blue-white hued star in the constellation Canis Major. Lambda CMa is visible to the naked eye with an apparent visual magnitude of +4.48. Based upon an annual parallax shift of 7.70 mas as seen from Earth, this star is located about 424 light years from the Sun. At that distance, the visual magnitude is diminished by an extinction of 0.14 due to interstellar dust.
This is a B-type main-sequence star with a stellar classification of B4 V. The star is roughly 40 million years old, and is spinning with a projected rotational velocity of 102 km/s. It has about 5.7 times the mass of the Sun and is radiating 560 times the Sun's luminosity at an effective temperature of 16,300 K.


List of stars in Hercules

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


37 Comae Berenices

37 Comae Berenices is a variable star system located around 690 light years away from the Sun in the northern constellation of Coma Berenices. It has the variable star designation LU Comae Berenices. 37 Comae Berenices was a later Flamsteed designation of 13 Canum Venaticorum. This object is visible to the naked eye as a faint, yellow-hued star with a baseline apparent visual magnitude of 4.88. It is drifting closer to the Earth with a heliocentric radial velocity of −14 km/s.
Tokovinin (2008) catalogued this as a wide triple star system. The primary component is an aging giant star, currently in the Hertzsprung gap, with a stellar classification of . It is a weak G-band star, a luminous giant star with a carbon abundance about a factor of 5 lower than is typical for such stars. This is a variable star most likely of the RS CVn type with an amplitude of 0.15 in magnitude, and it displays magnetic activity. It has 5.25 times the mass of the Sun and, having exhausted the supply of hydrogen at its core, has expanded to 38 times the Sun's radius.


53 Arietis

53 Arietis (abbreviated 53 Ari) is a variable star in the northern constellation of Aries. "53 Arietis" is the Flamsteed designation; it also bears the variable star designation UW Arietis. It is a B-type main sequence star with a stellar classification of B1.5 V and mean apparent magnitude of 6.10, which is near the lower limit for naked eye visibility. Based upon an annual parallax shift of 3.92 mas, the estimated distance to this star is roughly .
53 Arietis is a Beta Cephei variable. It is a runaway star with a peculiar velocity of 48.1 km/s relative to its neighbors. The star was ejected from the Orion nebula some 4–5 million years ago, possibly when an orbiting companion exploded as a supernova.


W Serpentis

W Serpentis is a multiple star in the constellation Serpens. The system varies between apparent magnitudes 8.42 and 10.2 over a period of just over 14 days, too faint to be seen with the unaided eye. This is mainly due to the system being an eclipsing binary (that is, one star passing in front of the other star and resulting in a change in brightness). However, variations in its period indicate there are some innate changes in luminosity of one or both component stars as they interact with each other, and it has been difficult to disentangle the light to determine their nature. The period is increasing by 14 seconds a year, indicating that a massive amount of material is being transferred from the larger fainter star to the smaller brighter one.
The system has been found to contain an accretion disk, and was one of the first discovered Serpentids, which are eclipsing binaries containing exceptionally strong far-ultraviolet spectral lines. These systems have a high rate of mass transfer between one star and the other, and are thought to evolve first into double periodic variables and then classical Algol variables. In the late stages of mass transfer, such systems can develop an optically thick disc and are segregated as a separate class of W Serpentis stars. The classes may also represent different types of system altogether, with the W Serpentis type being younger and more massive.
The spectral types of the component stars are not known; the hotter brighter star has been classed as an F-type giant. However, it appears to be completely obscured by material, and another theory holds that it is a hot main sequence star with the surrounding material responsible for the spectrum as it appears to be too luminous to be an F-class star. The spectrum of the secondary (larger and fainter) star has not been detected either. Examining the polarised light shows that a jet of material is probably coming from the primary star as well.
Further reading.
https://www.eso.org/sci/publications/messenger/archive/no.39-mar85/messenger-no39-40-42.pdf


Alpha Lupi

Alpha Lupi (α Lupi, α Lup) is a blue giant star, and the brightest star in the southern constellation of Lupus. According to the Bortle Dark-Sky Scale, its apparent visual magnitude of 2.3 makes it readily visible to the naked eye even from highly light-polluted locales. Based upon parallax measurements made during the Hipparcos mission, the star is around from the solar system. It is one of the nearest supernova candidates.
Characteristics.
Alpha Lupi is a giant star with a stellar classification of B1.5 III. It has about ten times the mass of the sun (~) yet is radiating 25,000 times the Sun's luminosity. The outer atmosphere has an effective temperature of 21,820 K, which gives it the blue-white glow of a B-type star. In 1956 it was identified as a Beta Cephei variable by Bernard Pagel and colleagues, which means it undergoes periodic changes in luminosity because of pulsations in the atmosphere. The variability period is 0.29585 days, or just over 7 hours, 6 minutes. The magnitude varies by about 0.05 magnitudes, or about 5% of its brightness. A 14th magnitude star situated 26" from Alpha Lupi is listed as a companion in double star catalogues.
This star is a proper motion member of the Upper-Centaurus Lupus sub-group in the Scorpius-Centaurus OB association, the nearest such co-moving association of massive stars to the Sun. This is a gravitationally unbound stellar association with an estimated age of 16–20 million years. The association is also the source of a bubble of hot gas that contains the Sun, known as the Local Bubble.
Visibility.
Visible from the Southern Hemisphere for much of the year, it can also be viewed for a shorter season from the northern tropics and from parts of the northern subtropical latitudes.
Etymology.
In Chinese, "Kekouan" (), meaning "Imperial Guards", refers to an asterism consisting of α Lupi, γ Lupi, δ Lupi, κ Centauri, β Lupi, λ Lupi, ε Lupi, μ Lup, π Lupi, and ο Lupi. Consequently, the Chinese name for α Lupi itself is (, .).
R. H. Allen described this star as having the Chinese name "Yang Mun" or "Men"(南門), meaning "the South Gate", in his work "". In Chinese astronomy, 南門 is located in "Horn" mansion and consisted of α and ε Centauri. It was referred to as "Yang Mun", meaning "the south Gate". Allen also suggested that the Babylonian name for the star was "Kakkab Su-gub Gud-Elim" (Star Left Hand of the Horned Bull).


NGC 237

NGC 237 is a spiral galaxy located in the constellation Cetus. It was discovered on September 27, 1867 by Truman Safford.


NGC 7777

NGC 7777 is a lenticular galaxy in the constellation of Pegasus.


NGC 398

NGC 398 is a lenticular galaxy located in the constellation Pisces. It was discovered on October 28, 1886 by Guillaume Bigourdan. It was described by Dreyer as "very faint, very small, stellar."


Gliese 299


Sigma Lupi

Sigma Lupi, Latinized from σ Lupi, is a star in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.4. Based upon an annual parallax shift of 5.67 mas as seen from Earth, it is located about 580 light years from the Sun. It is a member of the Upper Centaurus Lupus subgroup of the nearby Sco OB2 association.
This is a B-type main sequence star with a stellar classification of B1/B2 V. Sigma Lupi is a Helium strong star with an enhanced abundance nitrogen and an underabundance of carbon. Jerzykiewicz and Sterken (1992) showed a small amplitude variability with a period of 3.02 days. This suggests it is a close binary system forming a rotating ellipsoidal variable, although other causes such as rotational modulation can not be ruled out. There is a higher frequency photometric variability with a rate of 10.93482 per day and an amplitude of 0.0031 in visual magnitude, but the cause of this is unknown.
At an age of just 13.4 million years, Sigma Lupi is spinning with a projected rotational velocity of 68 km/s giving it a rotation period of 3.02 days. A magnetic field has been detected with a polar field strength of around 500 G, which is varying longitudinally with an amplitude of around 100 G. The star has an estimated nine times the mass of the Sun and 4.8 times the Sun's radius. It is radiating 5,754 times the solar luminosity from its outer atmosphere at an effective temperature of around 23,000 K.


Eta Ophiuchi

Eta Ophiuchi (η Ophiuchi, abbreviated Eta Oph, η Oph) is a binary star in the constellation of Ophiuchus. Based on parallax measurements taken during the Hipparcos mission, it is approximately 88 light-years from the Sun.
Eta Ophiuchi is part of a multiple star system designated WDS J17104-1544. It itself is designated WDS J17104-1544AB and its two components WDS J17104-1544A (also called Sabik , the traditional name for the system) and WDS J17104-1544B. The 'C' component is UCAC4 372-080717 and 'D' is UCAC2 26022336.
Nomenclature.
"η Ophiuchi" (Latinised to "Eta Ophiuchi") is the system's Bayer designation. WDS J17104-1544AB is its designation in the Washington Double Star Catalog. The designations of the two components as WDS J17104-1544 A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).
It bore the traditional name "Sabik", from the Arabic السابق "al-sābiq" "the preceding one", of uncertain reference. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name "Sabik" for the component WDS J17104-1544 A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.
In Chinese, this star is considered part of (), meaning "Left Wall of Heavenly Market Enclosure", which refers to an asterism representing eleven old states in China that mark the left borderline of the enclosure, consisting of Eta Ophiuchi, Delta Herculis, Lambda Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Theta¹ Serpentis, Eta Serpentis, Nu Ophiuchi and Xi Serpentis. Consequently, the Chinese name for Eta Ophiuchi itself is (, ), representing the state Song (宋).
Namesake.
USS Sabik (AK-121) was a United States Navy Crater class cargo ship named after the star.
Properties.
Eta Ophiuchi is a binary system that is difficult to resolve in amateur telescopes but whose true nature was determined through use of more advanced techniques. The primary star (whose observational data make up the table in this article) is actually only slightly larger and hotter than its companion. Individually each star is a fairly unremarkable A class main sequence star, but as a binary pair they are unusual. Each star orbits around a common center in a close and highly elliptical orbit, making planetary formation unlikely in this system and some stellar data imprecise.


Asalesha Nakshatram


List of stars in Caelum

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


T Microscopii

T Microscopii is a semiregular variable star in the constellation Microscopium. It ranges from magnitude 6.74 to 8.11 over a period of 352 days. Located around 700 light-years distant, it shines with a bolometric luminosity 7,509 times that of the Sun and has a surface temperature of .


NGC 5982

NGC 5982 is an elliptical galaxy located in the constellation Draco. It is located at a distance of circa 130 million light years from Earth, which, given its apparent dimensions, means that NGC 5982 is about 100,000 light years across. It was discovered by William Herschel on May 25, 1788.
NGC 5982 has a kinematically decoupled nucleus, with its major axis being nearly perpendicular to the rotation of the galaxy. NGC 5982 features many shells in its envelope, nearly 26. The shells form circular arcs, with the further being located at a radius of 150 arcseconds along the major axis of the galaxy, while the innermost one lies 8 arcseconds off the nucleus. The shells and the kinematically decoupled nucleus are the result of the merger of the elliptical galaxy with a small elliptical galaxy.
The galaxy has globular clusters that belong in two populations, red and blue. The age of the globular clusters in NGC 5982 is over 5 billion years. The luminosity of NGC 5982 is dominated by light emitted by old stars. In the centre of NGC 5982 lies a supermassive black hole whose mass is estimated to be (108.92 ) based on the M–sigma relation. The nucleus may display low level activity and has been categorised as a possible LINER.
NGC 5982 belongs to a galaxy group known as the NGC 5982 group. Other members of the group include the galaxies NGC 5976, NGC 5981, NGC 5985, NGC 5987, and NGC 5989. NGC 5981, a spiral galaxy seen edge-on, lies at a separation of 6.3 arcminutes from NGC 5982 and NGC 5985, a spiral galaxy seen face-on, lies at a separation of 7.7 arcminutes. The three galaxies are known as the Draco Trio or the Draco Group, although there is no evidence that they form a compact group.


RSGC3

RSGC3 is a young massive open cluster belonging to the Milky Way galaxy. It was discovered in 2010 in the GLIMPSE survey data. The cluster is located in the constellation Scutum at the distance of about 7 kpc from the Sun. It is likely situated at the intersection of the northern end of the Long Bar of the Milky Way and the inner portion of the Scutum–Centaurus Arm—one of its two major spiral arms.
The age of RSGC3 is estimated at 18–24 million years. The 16 detected red supergiant cluster members with masses of about are type II supernova progenitors. The cluster is heavily obscured and has not been detected in the visible light. It lies close to other groupings of red supergiants known as RSGC1, Stephenson 2, Alicante 7, Alicante 8, and Alicante 10. The total mass of RSGC3 is estimated at 20 thousand solar masses, which makes it one of the most massive open clusters in the Galaxy.
More work has identified a population of at least 30 additional red supergiants in the vicinity of RSGC3, 7 of which are tightly grouped and have been assumed to form a cluster name Alicante 7. The number of red supergiants identified in the several small areas studied in this region of the sky forms a significant fraction of all those known in the galaxy, suggesting very unusual properties for the region near the end of the galactic bar.


NGC 4536

NGC 4536 is an intermediate spiral galaxy in the constellation Virgo located about 10° south of the midpoint of the Virgo cluster. However, it is not considered a member of the cluster but is a member of the Virgo II Groups which form a southern extension of the Virgo Cluster. The morphological classification in the De Vaucouleurs system is SAB(rs)bc, which indicates it is a weakly barred spiral galaxy with a hint of an inner ring structure plus moderate to loosely wound arms. It does not have a classical bulge around the nucleus.
NGC 4536 has the optical characteristics of an HII galaxy, which means it is undergoing a strong burst of star formation. This is occurring prominently in the ring that surrounds the bar and nucleus. Based upon the level of X-ray emission from the core, it may have a small supermassive black hole with 104–106 times the mass of the Sun.
On March 8, 1981, a type Ia supernova was discovered 51 arcseconds to the northeast of the galactic center. It reached a peak visual magnitude of 12 on March 8 before steadily fading from view over the next two months. No prior supernova events have been observed in this galaxy.


NGC 5545

NGC 5545 is a spiral galaxy in the northern constellation of Boötes. It is interacting with the spiral galaxy NGC 5544.


Eta Canis Majoris

Eta Canis Majoris (η Canis Majoris, abbreviated Eta CMa, η CMa), also named Aludra , is a star in the constellation of Canis Major. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.
Nomenclature.
"η Canis Majoris" (Latinised to "Eta Canis Majoris") is the star's Bayer designation.
The traditional name "Aludra" originates from the Arabic: "العذراء" "al-adhraa" 'the virgin'. This star, along with Epsilon Canis Majoris (Adhara), Delta Canis Majoris (Wezen) and Omicron2 Canis Majoris (Thanih al Adzari), were "Al ʽAdhārā" ("العذاري"), 'the Virgins'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Aludra" for this star.
In Chinese, (), meaning "Bow and Arrow", refers to an asterism consisting of Eta Canis Majoris, Delta Canis Majoris, HD 63032, HD 65456, Omicron Puppis, k Puppis, Epsilon Canis Majoris, Kappa Canis Majoris and Pi Puppis. Consequently, Eta Canis Majoris itself is known as (, .)
Properties.
Aludra shines brightly in the skies in spite of a large distance from Earth due to being intrinsically many times brighter than the Sun. A blue-white supergiant of spectral type B5Ia, Aludra has a luminosity 176,000 times and a diameter around 80 times that of the Sun. Hohle and colleagues, using the parallax, extinction and analysis of spectrum, came up with a mass 19.19 times that and luminosity 105,442 times that of the Sun. It has only been around a fraction of the time the Sun has, yet is already in the last stages of its life. It is still expanding and may become a red supergiant, or perhaps has already passed that phase, but in either case it will become a supernova within the next few million years.
Aludra is classified as an Alpha Cygni type variable star and its brightness varies from magnitude +2.38 to +2.48 over a period of 4.7 days.
Namesakes.
Both USS Aludra (AF-55) and USS Aludra (AK-72), a Crater class cargo ship, were United States Navy vessels named after the star.


Theta Librae

θ Librae, Latinised as Theta Librae, is a single star in the southern zodiac constellation of Libra, near the constellation border with Scorpius. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.14. The distance to this star is approximately 168 light years, as determined by parallax, and it is drifting further away with a radial velocity of 5 km/s. The position of this star near the ecliptic means it is subject to lunar occultations.
This object is an aging giant star with a stellar classification of G9IIIb. Having exhausted the supply of hydrogen at its core, it has cooled and expanded; at present it has 12.3 times the girth of the Sun. The star has an estimated mass about 47% greater than the Sun. It is radiating about 68 times the luminosity of the Sun from its photosphere at an effective temperature of about . It is probably on the red giant branch, which indicates it is generating energy through hydrogen fusion in a shell outside an inert helium core. However, there is a 41% chance that it is a red clump giant on the horizontal branch, which would mean it was somewhat older and less massive. It has sometimes been classified spectroscopically as a subgiant, but detailed study shows that it is too cool and luminous to be on the subgiant branch.


NGC 204

NGC 204 is an unbarred lenticular galaxy located approximately 241 million light-years form the Solar System in the constellation Pisces. It was discovered on December 21, 1786 by William Herschel.


NGC 6072

NGC 6072 is a type I nebulae in the constellation Scorpius. It has a dynamical age of 104 years. Its circumstellar envelope is likely to be rich in Carbon as it has very strong CN (Cyanide) spectral lines. CN spectral lines are generally not detected in Oxygen rich AGB (Asymptotic giant branch) circumstellar envelopes. NGC 6072 also shows H2 (Hydrogen) emission and intense CO (Carbon Monoxide) emission which has been mapped displaying bipolarity and some gas at high velocity. The evolution of this planetary nebulae is likely to be dominated by photodissociation and ion/radical molecular reactions. Shock chemistry is also likely to be important.


S Coronae Australis

S Coronae Australis (S CrA), is a young binary star system estimated to be around 2 million years old located in the constellation Corona Australis. It is composed of a G-type main sequence star that is about as luminous as and just over twice as massive as the Sun, and a smaller K-type main sequence star that has around 50-60% of the Sun's luminosity and 1.3 times its mass. Both stars are T Tauri stars and both show evidence of having circumstellar disks. The system is around 140 parsecs distant.


RV Caeli

RV Caeli is a red giant star in the constellation Caelum. With an apparent magnitude of 6.4, it's barely visible to the naked eye, but this can vary. RV Caeli has a high radial velocity, which means it's moving away from the Solar System, and is currently located away using parallax.
Properties.
This star is a red giant who has exhausted hydrogen at it's core. It has a similar mass to the Sun, but has ballooned to 65 times the radius. It a very luminous star, with a luminosity about 1,000 times greater than our Sun. RV Caeli has a cool effective temperature of 3,984 K, which gives it a red hue. It is considered to be on the asymptotic giant branch, having exhausted its core hydrogen and helium.
Variability.
Hipparcos has found it to vary between its photometric values of 6.44 and 6.56, which roughly corresponds with the magnitude as seen with the naked eye. It was first suspected of variability in 1970. A 1982 survey again identified suspected variations, but could not confirm it was a variable star. It was confirmed as a variable star in 1999 on the basis of the Hipparcos photometry and given the variable star designation RV Caeli.


Omicron Geminorum

Omicron Geminorum (ο Geminorum, abbreviated Omicron Gem, ο Gem), also named Jishui, is a solitary star in the constellation of Gemini. It is faintly visible to the naked eye with an apparent visual magnitude of 4.90. Based upon an annual parallax shift of 19.61 mas, it is located at a distance of 166 light-years from the Sun.
Nomenclature.
"ο Geminorum" (Latinised to "Omicron Geminorum") is the star's Bayer designation.
The star bore the traditional Chinese name of "Jishui". 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 "Jishui" for this star on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.
Properties.
This is an F-type giant star with a stellar classification of F3 III. The measured angular diameter is , which, at its estimated distance, yields a physical size of about 3.7 times the radius of the Sun. It radiates approximately 24 times the solar luminosity from an outer atmosphere at an effective temperature of 6,309 K.
References.
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Kappa Eridani

Kappa Eridani, Latinized from κ Eridani, is a solitary star in the constellation Eridanus. With an apparent visual magnitude of 4.25, it is bright enough to be visible to the naked eye on a dark night. Based upon an annual parallax shift of 0.00642 arc seconds, it is roughly 510 light years distant from the Sun.
This appears to be an evolving B-type subgiant star with a stellar classification of B7 IV. The measured angular diameter is . At an estimated distance of Kappa Eridani, this yields a physical size of about six times the radius of the Sun. It has five times the Sun's mass, and radiates 1,175 times the solar luminosity from its outer atmosphere at an effective temperature of 14,700 K. Kappa Eridani is spinning with a projected rotational velocity of 10 km/s and is around 93 million years old.
References.
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Wall (Chinese constellation)

The Wall mansion () is one of the Twenty-eight mansions of the Chinese constellations. It is one of the northern mansions of the Black Tortoise.


HD 20782

HD 20782 is a 7th magnitude G-type main sequence star 117.5 light-years away from Earth, in the constellation of Fornax. HD 20782 is a part of a wide binary system in which the other star is designated HD 20781, and both stars host planetary systems. Indeed, this is the first known case of a binary star system where there are planetary systems around both the primary and the secondary stars in the system. The companion star HD 20781 has a very large angular separation of 252 arcsec, corresponding to 9080 AU at the distance of HD 20782. It is estimated to be 7.1 (± 4) billion years old, with a mass close to that of our Sun. (Note that, despite the numbering, HD 20782 is the primary star of the system, and HD 20781 the secondary star.)
An extremely eccentric extrasolar planet was announced around HD 20782 in 2006. In 2009 this planet's orbit was narrowed down, and it was found to have the highest eccentricity of all known exoplanets; this distinction has stood since 2012.
In 2011, two Neptune-mass planets were announced around the HD 20781, and initially they too were believed to be in eccentric orbits, but less so. However, later more detailed observations on this system revealed not only two more possible planets but also that all the planets in this system, in stark contrast to HD 20782, were likely in low eccentricity orbits.


Iota Carinae

Iota Carinae (ι Carinae, abbreviated Iota Car, ι Car), officially named Aspidiske , is a star in the southern circumpolar constellation of Carina. With an apparent visual magnitude of 2.2, it is one of the brighter stars in the night sky.
Appearance and location.
The star and rest of southern Carina never sets on places from about 34° S southwards including Cape Town; its northernmost viewpoints are unobstructed southern horizons near to the 30th parallel north, once a day.
The False Cross is an asterism formed from Iota Carinae, Delta Velorum, Kappa Velorum and Epsilon Carinae. It is so called because it is sometimes mistaken for the Southern Cross, causing errors in astronavigation.
The star appears 46.0' (0.7668°) WSW of lowercase a Carinae, a mid-third magnitude star, also forming part of the asterism and leading to its long, narrow projection which culminates in Canopus.
Nomenclature.
"ι Carinae" (Latinised to "Iota Carinae") is the star's Bayer designation.
It has the traditional cognate names "Aspidiske" (not be confused with "Asmidiske", the proper name of Xi Puppis), "Scutulum" and "Turais" (or "Tureis", a name shared with Rho Puppis). Turais is the Arabic "تُرَيْس" "turais" "small shield" (diminutive), while "Aspidiske" and "Scutulum" are Greek and Latin translations from "ασπίδα" and "scūtum". In 2016, the International Astronomical Union formed its Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names it approved which included "Aspidiske" for this star.
In Chinese, (), meaning "Sea Rock", refers to an asterism consisting of Iota Carinae, Epsilon Carinae, HD 83183, HD 84810 and Upsilon Carinae. Consequently, Iota Carinae itself is known as (, ).
Properties.
Based on parallax measurements this star is about from the Earth. It has a stellar classification of A9 Ib, with the luminosity class of 'Ib' indicating it has reached the stage of its evolution where it has expanded to become a lower-luminosity supergiant.
Iota Carinae has more than seven times the Sun's mass and has expanded to roughly 43 times the Sun's radius. It is radiating about 4,900 times the luminosity of the Sun. However, this luminosity appears to vary, causing the star's apparent magnitude to range between 2.23–2.28. This energy is being radiated into space from the star's outer envelope at an effective temperature of 7,500 K, giving Iota Carinae the white hue typical of an A-type star.
Due to precession of the Earth's axis of rotation, in the next 7,500 years the south celestial pole will pass close to this star and Upsilon Carinae and it will become the South Star around 8100 CE.


68 Cancri


TU Corvi

TU Corvi is a yellow-white hued star in the southern constellation of Corvus. It is a dimly visible to the naked eye with an apparent visual magnitude of 6.20. The distance to this star can be estimated from its annual parallax shift of , yielding a range of about 240 light years. Based upon measured changes in its proper motion, it may be a close binary system.
This is an F-type main-sequence star with a stellar classification of F0 V. Previously it had been classed as F0 III, matching an evolved giant star. It is a Delta Scuti variable, varying by an amplitude of 0.025 in B magnitude with a period of 118 minutes. At the age of 786 million years, it has a high rate of spin with a projected rotational velocity of 103 km/s. The star has 1.45 times the mass of the Sun and is radiating 12.6 times the Sun's luminosity from its photosphere at an effective temperature of 7,132 K.


Xi Aquilae b

Xi Aquilae b (abbreviated ξ Aquilae b, ξ Aql b), formally named Fortitudo , is an extrasolar planet approximately 200 light-years from the Sun in the constellation of Aquila. The planet was discovered orbiting the yellow giant star Xi Aquilae in 2008. The planet has a minimum mass of 2.8 Jupiter and a period of 137 days.
Name.
Following its discovery the planet was designated Xi Aquilae b. In July 2014 the International Astronomical Union launched a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning name was Fortitudo for this planet.
The winning name was submitted by Libertyer, a student club at Hosei University of Tokyo, Japan. "Fortitudo" is Latin for 'fortitude'. "Aquila" is Latin for 'eagle', a symbol of fortitude – emotional and mental strength in the face of adversity.


Teen Ta Tseang Keun

Teen Ta Tseang Keun () or Tëen ta tsëang keun meaning "Heaven's Great General", was a Chinese constellation () in the region of "Lóu" (). It lay between Andromeda and Triangulum. Allen based identification of Chinese star names by Williams and Reeves. But Allen lacked last word "kuen" as "Tien Ta Tseang" and also transliterated it as "Tsien Ta Tseang".
Identification of stars.
＊ 54 And is designated as φ Per in recent times.


NGC 6902

NGC 6902 is an unbarred spiral galaxy located in the constellation of Sagittarius at an approximate distance of 131.80 Mly. NGC 6902 was discovered in 1836 by John Herschel.


NGC 6940

NGC 6940 is an open cluster in the constellation Vulpecula. It was discovered by William Herschel in 1784. The cluster is nearly a billion years old and it is located 2,500 light years away. It is considered the finest open cluster in the constellation.
Observation.
It is located a bit more than two degrees south-southeast of 41 Cygni and three and a half degrees southwest from 52 Cygni. The cluster is bright enough to be seen even with small binoculars, which can partially resolve it. NGC 6940 is included in the Herschel 400 Catalogue.
Charasteristics.
NGC 6940 has hundreds of members. The cluster is quite scattered and in between its members are also visible field stars.
For example, two bright stars, an 8.6 mag B8III giant star at the NE edge and a 9.1 mag A0III giant at the SW corner of the cluster are too young to be true members of NGC 6940 and are probably background stars. The brightest star (lucida) of NGC 6940 is the red giant VG Vulpeculae, a semiregular variable star whose magnitude ranges from 9.0 to 9.5 every 80 days approximately. NGC 6940 is rich in red giants, more than 20 according to WEBDA database. Based on the spectroscopic analysis of twelve of them, the cluster age was estimated to be 1.1 billion years, with a turn-off mass of 2 M⊙. Its metallicity is close to the one of the Sun. In NGC 6940 have been detected 8 variable stars whose variability is consistent with the delta Scuti variables.
A study of the cluster by ROSAT in soft X-rays revealed four sources that are identified as cluster members. One more source was attributed to a possible cluster K0 giant star member, which was later confirmed to be a cluster member. Three of these sources were identified as binary stars, from a total of six known to exist in the cluster. The luminosity of the sources was typical of RS Canum Venaticorum variables, close binaries that could retain very active coronal sources despite the age of the cluster.


FS Canis Majoris

FS Canis Majoris (FS CMa), also known as HD 45677 or MWC 142, is a B-type star in the constellation of Canis Major. It has an apparent visual magnitude of approximately 8.50, having varied between magnitudes 7.35 and 8.58. Feinstein and colleagues reported in 1976 that it had decreased by 0.9 magnitude between 1969 and 1976, whereas it had only varied by 0.3 magnitude in the 70 years beforehand. Sometimes it could vary by up to 0.5 magnitude in a year or 0.1 magnitude in a night, and there did not appear to be any regular period to its variability.
Astronomer Anatoly Miroshnichenko has made it the prototype of a new type of variable star, the FS Canis Majoris variables. These are hot blue-white stars that exhibit forbidden line emission and strong infra-red excess suggestive of very young (pre-main-sequence) stars yet they do not lie in star-forming regions. Nor did they appear to be stars that had evolved off the main sequence into giant or supergiant stars. It is now thought that they are main sequence stars that have absorbed or are absorbing matter, most likely from a companion star, and are surrounded by a compact dusty shell. These stars are thought to be significant contributors to interstellar dust.
Its spectral type has been previously classified as B2III to B2V and its bolometric magnitude as -4.89. However, investigation of its spectrum in 2006 showed that FS Canis Majoris is a binary system. The system is between 1250 and 8000 times as luminous as the Sun. One calculation has the masses of the primary and secondary at 9.3±0.5 and 4.8±0.9 solar masses and radii 6.6±0.5 and 2.9±0.6 times that of the Sun, and surface temperatures of 21,600±350 and 16,380±1670 K respectively.


Mu Lupi

Mu Lupi (μ Lup) is a system of three or four stars in the southern constellation of Lupus. It is visible to the naked eye with an apparent visual magnitude of 4.29 and lies roughly 340 light years from the Sun.
Two of the components of this system, A and B, form a pair with an angular separation of 1.1 arc seconds. As of 2014, no orbit has been published. Component C lies at an angular separation of 22.6 arc seconds from the AB pair, and may be a common proper motion companion. It is an A-type main sequence star with a classification of A2 V. A fourth component at an angular separation of 6.15 arc seconds from component A, may be a brown dwarf.


HD 87883

HD 87883 is star in the northern constellation of Leo Minor. It is too faint to be viewed with the naked eye, having an apparent visual magnitude of 7.56. The star is located at a distance of 59.7 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +9.3 km/s. It has an absolute magnitude of 6.27.
This is an ordinary K-type main-sequence star with a stellar classification of K0V. It has a modest level of chromospheric activity, and is rotating with a period of 38.6 days. The star is smaller than the Sun, with 82% of the mass of the Sun and 76% of the Sun's radius. The age of this star is 9.8 billion years, compared with 4.6 billion years for our Sun. It is radiating 32% of the luminosity of the Sun from its photosphere at an effective temperature of 4,980 K.
In August 2009, this star was found to have a planet via the radial velocity method. The orbital solution shows it to be a Super-Jupiter body in an elliptical orbit with a period of and a typical separation of . A relatively high deviation on the model fit suggests there may be an additional planetary companion in a close, perturbing orbit of the star. The orbital parameters of the known planet does not preclude the existence of an Earth-mass planet with a dynamically-stable orbit in the habitable zone.


NGC 230

NGC 230 is a spiral galaxy located in the constellation Cetus. It was discovered in 1886 by Francis Leavenworth.


Tuiren (star)

Tuiren, also referred to as HAT-P-36, is a 12th magnitude G-type main-sequence star estimated to be approximately 1,034 light-years away from Earth in the constellation Canes Venatici. Tuiren is too faint to be seen with the naked eye, but it is possible to view it with binoculars or a small telescope. In 2012 a hot Jupiter-type exoplanet was discovered orbiting Tuiren with an orbital period of about 1.3 Earth days. In December 2019, HAT-P-36 was named Tuiren and its planetary companion, HAT-P-36b, was named Bran as a result of Ireland's contribution to the 2019 NameExoWorlds campaign. Bran has a mass approximately 1.8 times that of Jupiter and a radius 1.2 times larger.
Etymology.
Tuiren and its planet are named after characters from "The Birth of Bran", a story in the book "Irish Fairy Tales" by James Stephens. The book is a re-telling of various stories from Irish folklore. Tuiren was the aunt of the mythical hero Fionn mac Cumhaill and was turned into a hound by the fairy Uchtdealbh after Tuiren married her husband. Bran and Sceólan were the two puppies mothered by Tuiren while she was a dog. They were cousins of Fionn mac Cumhaill. The names were proposed by John Murphy, a teacher at Regina Mundi College, Cork.
Planets.
Bran (HAT-P-36b) was discovered in 2012 by the HATNet Project using the transit method.


HD 34557

HD 34557 is a double star in the northern constellation of Auriga. The fainter star has an angular separation of 0.380″ from the primary component. They have a combined apparent magnitude of 5.52, making HD 34557 faintly visible to the naked eye from dark skies. Based upon parallax measurements made with the Hipparcos satellite, this system is roughly 280 light years away. The primary component is spinning rapidly, with a projected rotational velocity of 217 km/s. It has a stellar classification of A3V, making it an A-type main sequence star.


Ghost Nebula

The Ghost Nebula (designated Sh2-136, VdB 141) is a reflection nebula located in the constellation Cepheus.
It lies near the cluster NGC 7023. Looking at the adjacent image, the nebula's name is easily understood. The Ghost nebula is referred to as a globule (cataloged "CB230") and over 2 light-years across. There are several stars embedded, whose emissions make the nebula shine in brownish colour.
The Ghost Nebula should not be confused with the Little Ghost Nebula (NGC 6369), the Ghost Head Nebula (NGC 2080) or the Ghost of Cassiopeia (IC 63).


Mu Canis Majoris

Mu Canis Majoris (μ Canis Majoris) is a binary star system in the southern constellation of Canis Major. The pair can be located a little to the southwest of the point midway between Gamma and Theta Canis Majoris, and the components can be split with a small telescope. The system is faintly visible to the naked eye with an apparent visual magnitude of 5.12. Based upon an annual parallax shift of just 2.62 mas as seen from Earth, this system is located roughly 1,200 light years from the Sun.
Grotius assigned the name Isis to this star, but the name, now obsolete, belonged rather to Gamma Canis Majoris.
As of 2011, the pair had an angular separation of 2.77 arc seconds along a position angle of 343.9°. The orange-hued primary member, component A, is an evolved K-type giant star with a stellar classification of K2/3 III and a visual magnitude of 5.27. The base magnitude 7.32 companion, component B, is a hybrid B/A-type main-sequence star with a class of B9/A0 V.
The system has two visual companions. As of 2008, magnitude 10.32 component C lies at an angular separation of 86.90″, while magnitude 10.64 component D is at a separation of 105.0″. Mu CMa should not be confused with the 9th magnitude variable star MU CMa located near NGC 2360.