Delta Hydri
Star in the constellation Hydrus
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Delta Hydri, Latinized from δ Hydri, is a single,[7] white-hued star in the southern constellation of Hydrus. It is bright enough to be faintly visible to the naked eye with an apparent visual magnitude of 4.09.[2] The distance to this star, based upon an annual parallax shift of 23.35 mas,[1] is about 140 light years. It is moving away from the Sun with a radial velocity of +6 km/s.[4]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydrus |
| Right ascension | 02h 21m 44.94286s[1] |
| Declination | −68° 39′ 33.9038″[1] |
| Apparent magnitude (V) | 4.09[2] |
| Characteristics | |
| Spectral type | A2 V[3] |
| U−B color index | +0.05[2] |
| B−V color index | +0.03[2] |
| Astrometry | |
| Radial velocity (Rv) | +6.00[4] km/s |
| Proper motion (μ) | RA: -49.95[1] mas/yr Dec.: +2.48[1] mas/yr |
| Parallax (π) | 23.35±0.34 mas[1] |
| Distance | 140 ± 2 ly (42.8 ± 0.6 pc) |
| Absolute magnitude (MV) | 0.92[3] |
| Details | |
| Mass | 2.25[5] M☉ |
| Radius | 2.3[5] R☉ |
| Luminosity | 39.52[3] L☉ |
| Surface gravity (log g) | 3.98[6] cgs |
| Temperature | 9,880±336[6] K |
| Metallicity [Fe/H] | +0.12[3] dex |
| Rotational velocity (v sin i) | 162[6] km/s |
| Age | 209[6] Myr |
| Other designations | |
| δ Hyi, CPD−69°113, FK5 1065, GC 2872, HD 15008, HIP 11001, HR 705, SAO 248545 | |
| Database references | |
| SIMBAD | data |
This is an ordinary A-type main-sequence star with a stellar classification of A2 V[3] It is about 209 million years old and has a high rate of spin, showing a projected rotational velocity of 162 km/s.[6] This is giving the star an oblate shape with an equatorial bulge that is 7% larger than the polar radius.[8] The star has 2.25 times the mass of the Sun and 2.3 times the Sun's radius.[5] It is radiating 39.5[3] times the Sun's luminosity from its photosphere at an effective temperature of around 9.880.[6] Delta Hydri has been checked for an infrared excess, but none was found.[7]