Theta Delphini
Star in the constellation of Delphinus
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Theta Delphini, a name Latinized from θ Delphini, is a single[12] star in the northern constellation of Delphinus. It has an apparent visual magnitude of about 5.7,[2] meaning that it is just barely visible to the naked eye under excellent viewing conditions. The distance to this star is approximately 2,050 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −15 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 38m 43.98644s[1] |
| Declination | +13° 18′ 54.4543″[1] |
| Apparent magnitude (V) | 5.69[2] |
| Characteristics | |
| Spectral type | K3Ib[3] |
| U−B color index | +1.71[4] |
| B−V color index | 1.509±0.047[2] |
| Astrometry | |
| Radial velocity (Rv) | −15.09±0.13[5] km/s |
| Proper motion (μ) | RA: 3.068[1] mas/yr Dec.: −0.179[1] mas/yr |
| Parallax (π) | 1.5887±0.0738 mas[1] |
| Distance | 2,050 ± 100 ly (630 ± 30 pc) |
| Details | |
| Mass | 5.69[6] M☉ |
| Radius | 125 R☉[7] 88±25[8] R☉ |
| Luminosity | 2,333+1,103 −748[7] L☉ |
| Surface gravity (log g) | 1.3[9] cgs |
| Temperature | 3,986±170[7] K |
| Metallicity [Fe/H] | +0.22[9] dex |
| Rotational velocity (v sin i) | 3.0[10] km/s |
| Other designations | |
| θ Del, 8 Del, BD+12°4411, GC 28743, HD 196725, HIP 101882, HR 7892, SAO 106342[11] | |
| Database references | |
| SIMBAD | data |
The stellar classification of Theta Delphini is K3Ib, which means it is a K-type supergiant.[13] These types of stars form when relatively massive (10 to 30 M☉) stars like B-type main sequence stars run out of hydrogen to fuse and start cooling down.[14] It has been described as a super-metal-rich star because of its high metallicity.[9]