Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Canes Venatici |
Right ascension | 12h 45m 07.826s [1] |
Declination | +45° 26′ 24.93″ [1] |
Apparent magnitude (V) | +4.86 to +7.32 [2] |
Characteristics | |
Evolutionary stage | Asymptotic giant branch |
Spectral type | C54J(N3) [3] |
U−B color index | 6.62 [4] |
B−V color index | 2.54 [4] |
V−R color index | 1.75 [5] |
R−I color index | 1.38 [5] |
Variable type | SRb [3] |
Astrometry | |
Radial velocity (Rv) | 15.30 [6] km/s |
Proper motion (μ) | RA: −2.968 [1] mas/yr Dec.: 13.063 [1] mas/yr |
Parallax (π) | 3.2222 ± 0.1744 mas [1] |
Distance | 1,010 ± 50 ly (310 ± 20 pc) |
Absolute magnitude (MV) | −1.203 [7] |
Details | |
Mass | 1.2 [8] M☉ |
Radius | 422 [9] R☉ |
Luminosity | 9,400 [10] L☉ |
Surface gravity (log g) | +0.23 [8] cgs |
Temperature | 2,600 - 3,200 [11] K |
Metallicity [Fe/H] | −0.21 [8] dex |
Other designations | |
Database references | |
SIMBAD | data |
La Superba (Y CVn, Y Canum Venaticorum) is a strikingly red giant star in the constellation Canes Venatici. It is a carbon star and semiregular variable.
La Superba is a semiregular variable star, varying by about a magnitude over a roughly 160-day cycle, but with slower variation over a larger range. Periods of 194 and 186 days have been suggested, with a resonance between the periods. [11]
Y CVn is one of the reddest stars known, and it is among the brightest of the giant red carbon stars. It is the brightest of known J-stars, which are a very rare category of carbon stars that contain large amounts of carbon-13 (carbon atoms with 7 neutrons instead of the usual 6). The 19th century astronomer Angelo Secchi, impressed with its beauty, gave the star its common name, [12] which is now accepted by the International Astronomical Union. [14]
The angular diameter of La Superba has been measured at 13.81 mas . [15] It is expected to be pulsating but this has not been seen in the measurements. At 230 pc , this corresponds to a radius of 1.59 astronomical units (342 R☉ ). [lower-alpha 1] If it were placed at the position of the Sun, the star's surface would extend beyond the orbit of Mars.
La Superba's temperature is believed to be about 2,760 K , making it one of the coolest true stars known. It is faintly visible to the naked eye, and the red colour is very obvious in binoculars. [12] When infrared radiation is included, Y CVn has a bolometric luminosity several thousand times that of the Sun. The mass of this type of star is difficult to determine; it would initially have been around 3 M☉ and somewhat less now due to mass loss. An estimate from Jim Kaler gives the star a luminosity between 22,000 and 87,000 L☉ and radius between 557 and 1,092 R☉ based on an assumed temperature of 3,000 K, and the author then classified it as a C7 or CN5 supergiant star although its mass is too low to be a true supergiant. [16]
Observations in the 60 and 100 micron infrared bands by the IRAS satellite showed that Y CVn is surrounded by a dust shell 0.9 parsecs in diameter. [17] This is one of the most prominent circumstellar dust shells detected in the IRAS all-sky survey.
After stars up to a few times the mass of the sun have finished fusing hydrogen to helium in their core, they start to burn hydrogen in a shell outside a degenerate helium core, and expand dramatically into the red giant state. Once the core reaches a high enough temperature, it ignites violently in the helium flash, which begins helium core burning on the horizontal branch. Once even the core helium is exhausted, a degenerate carbon-oxygen core remains. Fusion continues in both hydrogen and helium shells at different depths in the star, and the star increases luminosity on the asymptotic giant branch (AGB). La Superba is currently an AGB star.
In the AGB stars, fusion products are moved outwards from the core by strong deep convection known as a dredge-up, thus creating a carbon abundance in the outer atmosphere where carbon monoxide and other compounds are formed. These molecules tend to absorb radiation at shorter wavelengths, resulting in a spectrum with even less blue and violet compared to ordinary red giants, giving the star its distinguished red color. [18]
La Superba is most likely in the final stages of fusing its remaining secondary fuel (helium) into carbon and shedding its mass at the rate of about a million times that of the Sun's solar wind. It is also surrounded by a 2.5 light year-wide shell of previously ejected material, implying that at one point it must have been losing mass as much as 50 times faster than it is now. La Superba thus appears almost ready to eject its outer layers to form a planetary nebula, leaving behind its core in the form of a white dwarf. [19]
Mu Cephei, also known as Herschel's Garnet Star, Erakis, or HD 206936, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.
R Centauri is a Mira variable star in the constellation Centaurus.
R Andromedae is a Mira-type variable star in the constellation Andromeda. Its spectral class is type S because it shows absorption bands of zirconium monoxide (ZrO) in its spectrum. It was among the stars found by Paul Merrill to show absorption lines of the unstable element technetium, establishing that nucleosynthesis must be occurring in stars. The SH molecule was found for the first time outside earth in the atmosphere of this star. The star is losing mass due to stellar winds at a rate of 1.09×10−6M☉/yr.
NO Apodis is a solitary, red hued variable star located in the southern circumpolar constellation Apus. It has an average apparent magnitude of 5.86, allowing it to be faintly seen with the naked eye. The object is relatively far at a distance of 790 light years but is drifting closer with a heliocentric radial velocity −18.3 km/s.
HD 30442 is a solitary star in the northern circumpolar constellation Camelopardalis. It is faintly visible to the naked eye with an apparent magnitude of 5.47 and is estimated to be 403 light years away from the Solar System. The object has a heliocentric radial velocity of −37 km/s, indicating that it is drifting closer.
TX Piscium is a variable red giant star in the constellation Pisces. It is amongst the reddest naked eye stars, with a significant reddish hue when seen in binoculars. It is approximately 800 light years from Earth.
WR 124 is a Wolf–Rayet star in the constellation of Sagitta surrounded by a ring nebula of expelled material known as M1-67. It is one of the fastest runaway stars in the Milky Way with a radial velocity around 200 km/s. It was discovered by Paul W. Merrill in 1938, identified as a high-velocity Wolf–Rayet star. It is listed in the General Catalogue of Variable Stars as QR Sagittae with a range of 0.08 magnitudes.
HD 85951, formally named Felis, is a solitary orange hued star in the constellation Hydra. It has an apparent magnitude of 4.94, making it faintly visible to the naked eye under ideal conditions. Based on parallax measurements, the object is about 570 light-years away from the Sun and is receding with a heliocentric radial velocity of 50 km/s.
UY Scuti (BD-12°5055) is a red supergiant star in the constellation Scutum. It is considered to be possibly one of the largest known stars and is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56. It has an estimated radius of 909 solar radii thus a volume of 750 million times that of the Sun., This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars.
TT Cygni is a carbon star located 561 parsecs (1,830 ly) away in the northern constellation of Cygnus. It is classified as a semiregular variable of subtype SRb that ranges in brightness from magnitude 7.26 down to 8.0 with a period of 118 days. This object is called a carbon star because it has a high ratio of carbon to oxygen in its surface layers. The carbon was produced by helium fusion, dredged up from inside the star by deep convection triggered by a flash from the helium shell.
10 Canum Venaticorum is the Flamsteed designation for an ordinary star in the northern constellation of Canes Venatici. It has an apparent visual magnitude of 5.95, which, according to the Bortle scale, can be faintly seen with the naked eye from suburban locations. Based upon an annual parallax shift of 0.057 arcseconds, this system is 57.26 light-years from Sun. It is drifting further away with a radial velocity of +80 km/s.
Y Lyncis is a semiregular variable star in the constellation Lynx. It is an asymptotic giant branch star of spectral type M6S, with a luminosity class of Ib, indicating a supergiant luminosity. It is around 1,160 light years away.
IK Tauri or NML Tauri is a Mira variable star located about 280 parsecs (910 ly) from the Sun in the zodiac constellation of Taurus.
BP Tauri is a young T Tauri star in the constellation of Taurus about 416 light years away, belonging to the Taurus Molecular Cloud.
GP Comae Berenices, abbreviated to GP Com and also known as G 61-29, is a star system composed of a white dwarf orbited by a planetary mass object, likely the highly eroded core of another white dwarf star. The white dwarf is slowly accreting material from its satellite at a rate of (3.5±0.5)×10−11 M☉/year and was proven to be a low-activity AM CVn star. The star system is showing signs of a high abundance of ionized nitrogen from the accretion disk around the primary.
Y Tauri is a carbon star located in the constellation Taurus. Parallax measurements by Gaia put it at a distance of approximately 2,170 light-years.
HD 179886 is a binary star located in the southern constellation Telescopium. It has a combined apparent magnitude of 5.37, making it faintly visible to the naked eye if viewed under ideal conditions. The system is situated at a distance of 700 light years but is receding with a heliocentric radial velocity of 6.3 km/s.
HD 200044 is a solitary star in the equatorial constellation Delphinus. It has an apparent magnitude of 5.7, allowing it to be faintly seen with the naked eye. The object is located 598 light years away, but is approaching the Solar System with a heliocentric radial velocity of −15.07 km/s.
HD 193373 is a solitary red hued star located in the equatorial constellation Delphinus. It has an apparent magnitude of 6.21, placing it near the limit for naked eye visibility. Parallax measurements place it 846 light years distant and it is currently receding with a heliocentric radial velocity of 22.7 km/s.
HD 37289, also known as HR 1916, is a solitary, orange hued star located in the northern circumpolar constellation Camelopardalis. It has an apparent magnitude of 5.61, making it faintly visible to the naked eye under ideal conditions. Based on parallax measurements from the Gaia spacecraft, the object is estimated to be 308 light years distant. It appears to be approaching the Sun, having a heliocentric radial velocity of −20.7 km/s.