Upsilon2 Hydrae
Star in the constellation Hydra
From Wikipedia, the free encyclopedia
Upsilon2 Hydrae, Latinised from υ2 Hydrae, is a solitary[10] star in the equatorial constellation of Hydra. Visible to the naked eye, it is photometrically stable[11] with an apparent visual magnitude of 4.59.[2] Based upon an annual parallax shift of 10.40 mas as seen from Earth,[1] it is located about 314 light-years from the Sun.
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10h 05m 07.46888s[1] |
| Declination | −13° 03′ 52.6561″[1] |
| Apparent magnitude (V) | 4.59[2] |
| Characteristics | |
| Spectral type | B9 III-IV[3] |
| U−B color index | −0.27[2] |
| B−V color index | −0.08[2] |
| Astrometry | |
| Radial velocity (Rv) | +24.3±2.6[4] km/s |
| Proper motion (μ) | RA: −39.39[1] mas/yr Dec.: +19.65[1] mas/yr |
| Parallax (π) | 10.40±0.23 mas[1] |
| Distance | 314 ± 7 ly (96 ± 2 pc) |
| Absolute magnitude (MV) | −0.31[5] |
| Details | |
| Mass | 3.29±0.03[6] M☉ |
| Radius | 3.2[7] R☉ |
| Luminosity | 182[6] L☉ |
| Surface gravity (log g) | 3.87[8] cgs |
| Temperature | 11758±400[8] K |
| Rotational velocity (v sin i) | 58[8] km/s |
| Age | 97[8] Myr |
| Other designations | |
| υ2 Hya, 40 Hydrae, BD−12°3073, FK5 1261, HD 87504, HIP 49402, HR 3970, SAO 155713[9] | |
| Database references | |
| SIMBAD | data |
This is a B-type star with a stellar classification of B9 III-IV,[3] showing partial traits of a subgiant and giant star in its spectrum. However, Zorec and Royer (2012) estimate the star still only 79% of the way through its life span on the main sequence.[6] With an age of around 97 million years,[8] it is spinning with a projected rotational velocity of 58 km/s.[8] The star has an estimated 3.29[6] times the mass of the Sun and around 3.2[7] times the Sun's radius. It is radiating 182[6] times the solar luminosity from its photosphere at an effective temperature of about 11,758 K.[8]