Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Horologium |
Right ascension | 03h 12m 33.16062s [2] |
Declination | −57° 19′ 17.5710″ [2] |
Apparent magnitude (V) | 5.71 [3] (5.52 to 5.95) [4] |
Characteristics | |
Spectral type | C-N4IIIb: (C23.5) [5] |
U−B color index | +2.93 [6] |
B−V color index | +2.419±0.014 [3] |
Variable type | SRb [4] |
Astrometry | |
Radial velocity (Rv) | +14.3±2.9 [3] km/s |
Proper motion (μ) | RA: +18.492 [2] mas/yr Dec.: +13.298 [2] mas/yr |
Parallax (π) | 2.3755 ± 0.1295 mas [2] |
Distance | 1,370 ± 70 ly (420 ± 20 pc) |
Absolute magnitude (MV) | −1.79 [3] |
Absolute bolometric magnitude (Mbol) | −4.62 [7] |
Details | |
Mass | 3.29±0.65 [8] M☉ |
Radius | 303 [9] [lower-alpha 1] R☉ |
Luminosity | 6,700 [9] L☉ |
Surface gravity (log g) | 0.049 [10] cgs |
Temperature | 3,000 [9] K |
Other designations | |
Database references | |
SIMBAD | data |
TW Horologii is a carbon star and semiregular variable in the southern constellation of Horologium, [12] near the eastern constellation border with Reticulum. It has a ruddy hue and, with an apparent visual magnitude that ranges from 5.52 down to 5.95, [4] is visible to the naked eye and one of the brightest carbon stars. [12] Based on parallax measurements, it is located at a distance of approximately 1,370 light years from the Sun. [2] It is drifting further away with a radial velocity of +14 km/s. [3] In the past this star has been considered a member of the open cluster NGC 1252, but this now seems unlikely. [13]
This is an aging red giant star on the asymptotic giant branch [7] with a stellar classification of C-N4IIIb: and a C2 index of C23.5. It has been listed as a standard star for that MK spectral class. [5] The star is classified as a semiregular variable of type SRb and has a periodicity of 158 days. [4] It has expanded to 303 times the radius of the Sun and, on average, is radiating 6,700 times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,000 K. [9] The short-lived element technetium has been observed in the spectrum, an indicator of thermal pulses during helium shell burning. [14]
Based on the detection of excess ultraviolet excess, it is most likely a binary star system. [15] An analysis of the motion of TW Horologii suggests a low-mass companion, although the UV excess suggests it is hot. [8]
In 2013 the luminosity of Mira variables, based on Hipparcos parallaxes, was used to calibrate a Period-luminosity relationship for carbon stars. The absolute magnitude of TW Horologii was calculated to be −1.79. [3]
Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.
RV Tauri variables are luminous variable stars that have distinctive light variations with alternating deep and shallow minima.
Omega Virginis is a solitary star in the zodiac constellation Virgo. It has an apparent visual magnitude of +5.2, which is bright enough to be faintly visible to the naked eye. Based upon an annual stellar parallax shift of 6.56 milliarcseconds, it is located about 500 light years from the Sun.
Theta Apodis is a variable star in the southern circumpolar constellation of Apus. It is a variable star with an apparent visual magnitude range of 4.65 to 6.20, which, according to the Bortle Dark-Sky Scale, means it is a faint star but visible to the naked eye from dark suburban skies. The distance to Theta Apodis is approximately 350 light-years, based upon parallax measurements made from the Gaia telescope. It is unusual in that it is a red star with a high proper motion.
27 Cancri is a single star in the zodiac constellation of Cancer, located around 990 light-years away from the Sun. It is visible to the naked eye as a faint, red-hued star with a typical apparent visual magnitude of around +5.56. The star is moving closer to the Earth with a heliocentric radial velocity of −8.3 km/s. It is a member of the Arcturus stream, a group of stars with high proper motion and metal-poor properties thought to be the remnants of a small galaxy consumed by the Milky Way.
La Superba is a strikingly red giant star in the constellation Canes Venatici. It is a carbon star and semiregular variable.
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 Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.
PZ Cassiopeiae is a red supergiant star located in the constellation of Cassiopeia, and a semi-regular variable star.
RS Telescopii, abbreviated RS Tel, is a variable star in the southern constellation of Telescopium. It is a dim star with an apparent visual magnitude of 10.67, which is much too faint to be visible without a telescope. The variability of this star was discovered by Evelyn F. Leland and announced by Edward C. Pickering in 1910. It was first studied by Cecilia H. Payne in 1928 at the Harvard College Observatory.
S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17, which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements, but it is drifting closer with a heliocentric radial velocity of −75 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.
V915 Scorpii is a hypergiant and semiregular variable star, located 1,718 parsecs (5,600 ly) away in the constellation Scorpius. Its apparent magnitude varies between 6.22 and 6.64, being heavily diminshed by 2.93 magnitudes due to interstellar extinction.
BC Cygni is a red supergiant and pulsating variable star of spectral type M3.5Ia in the constellation Cygnus.
II Lupi is a Mira variable and carbon star located in the constellation Lupus. It is the brightest carbon star in the southern hemisphere at 12 μm.
V Crucis is a carbon star in the constellation Crux. A Mira variable, its apparent magnitude ranges from 8.7 to 11.1 over 376.5 days. The fact that this star's period is nearly equal to one year makes it hard to get good observational coverage over the entire cycle. Its near-infrared light curve shows a contribution from the first harmonic of the fundamental period.
R Fornacis is a Mira variable and carbon star located in the constellation Fornax. It is around 1,800 light years away based on parallax measurements.
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.
EP Aquarii is a semiregular variable star in the equatorial constellation of Aquarius. At its peak brightness, visual magnitude 6.37, it might be faintly visible to the unaided eye under ideal observing conditions. A cool red giant on the asymptotic giant branch (AGB), its visible light brightness varies by about 1/2 magnitude over a period of 55 days. EP Aquarii has a complex circumstellar envelope (CSE), which has been the subject of numerous studies.
56 Leonis is a red giant variable star located approximately 390 light years away in the constellation Leo.