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Star in the constellation Apus From Wikipedia, the free encyclopedia
Theta Apodis (θ Apodis, θ Aps) 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,[3] 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 (110 parsecs), based upon parallax measurements made from the Gaia telescope.[6] It is unusual in that it is a red star with a high proper motion (greater than 50 milliarcseconds a year).[10]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Apus |
Right ascension | 14h 05m 19.87784s[1] |
Declination | −76° 47′ 48.3204″[1] |
Apparent magnitude (V) | 4.65 - 6.20[2] |
Characteristics | |
Spectral type | M7 III[3] |
U−B color index | +1.07[4] |
B−V color index | +1.48[4] |
Variable type | SRb[3] |
Astrometry | |
Radial velocity (Rv) | +9.0[5] km/s |
Proper motion (μ) | RA: −83.823[6] mas/yr Dec.: −34.694[6] mas/yr |
Parallax (π) | 9.2261 ± 0.6873 mas[6] |
Distance | 350 ± 30 ly (108 ± 8 pc) |
Absolute magnitude (MV) | 0.7[3] |
Details | |
Mass | 2.9[7] M☉ |
Radius | 208[8] R☉ |
Luminosity | 3,748[8] L☉ |
Surface gravity (log g) | −0.086[8] cgs |
Temperature | 3,131[8] K |
Metallicity [Fe/H] | −0.20[7] dex |
Other designations | |
Database references | |
SIMBAD | data |
This is an evolved red giant that is currently on the asymptotic giant branch,[12] with a stellar classification of M7 III.[3] It shines with a luminosity approximately 3879 times that of the Sun and has a surface temperature of 3,131 K.[8] It is a semiregular pulsating variable and its brightness changes over a range of 0.56 magnitudes with a period of 119[3] days. A longer period of around 1,000 days has also been detected.[11] It is losing mass at the rate of 1.1 × 10−7 times the mass of the Sun per year through its stellar wind. Dusty material ejected from this star is interacting with the surrounding interstellar medium, forming a bow shock as the star moves through the galaxy. The stand-off distance for this front is located at about 0.134 ly (0.041 pc) from Theta Apodis.[12]
Theta Apodis has been identified as an astrometric binary, indicating that it has an orbiting companion that causes gravitational perturbation of the primary star.[13]
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