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 | |
| Evolutionary stage | main sequence[3] |
| Spectral type | B9 III-IV[4] |
| U−B color index | −0.27[2] |
| B−V color index | −0.08[2] |
| Astrometry | |
| Radial velocity (Rv) | +24.3±2.6[5] 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[6] |
| Details | |
| Mass | 2.92[7] M☉ |
| Radius | 3.52[7] R☉ |
| Luminosity | 172[7] L☉ |
| Surface gravity (log g) | 3.81[7] cgs |
| Temperature | 11,143[7] 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,[4] 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.[3] 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 2.9 times the mass of the Sun and around 3.5 times the Sun's radius. It is radiating 172 times the solar luminosity from its photosphere at an effective temperature of about 11,143 K.[7]