Eta Delphini
Star in the constellation Delphinus
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Eta Delphini, Latinized from η Delphini, is a candidate astrometric binary[10] star system in the northern constellation of Delphinus. It has an apparent magnitude of about 5.4, meaning that it is faintly visible to the naked eye. Based upon a parallax measurement of 13.81[1] mas made by the Hipparcos spacecraft, this star is around 240 light years away from the Sun. It is advancing in general direction of the Earth with a radial velocity of −25 km/s.[4]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Delphinus |
| Right ascension | 20h 33m 57.04099s[1] |
| Declination | +13° 01′ 38.1437″[1] |
| Apparent magnitude (V) | 5.38[2] |
| Characteristics | |
| Spectral type | A3 IVs[3] |
| U−B color index | +0.05[2] |
| B−V color index | +0.08[2] |
| Astrometry | |
| Radial velocity (Rv) | −25.00±4.2[4] km/s |
| Proper motion (μ) | RA: +73.15[1] mas/yr Dec.: +24.66[1] mas/yr |
| Parallax (π) | 13.81±1.17 mas[1] |
| Distance | 240 ± 20 ly (72 ± 6 pc) |
| Absolute magnitude (MV) | +1.11[5] |
| Details | |
| Mass | 2.12[6] M☉ |
| Radius | 2.2[7] R☉ |
| Luminosity | 35[8] L☉ |
| Surface gravity (log g) | 4.38[6] cgs |
| Temperature | 9,355±318[6] K |
| Metallicity [Fe/H] | +0.56[5] dex |
| Rotational velocity (v sin i) | 65[8] km/s |
| Age | 309[6] Myr |
| Other designations | |
| η Del, 3 Del, BD+12°4378, GC 28617, HD 195943, HIP 101483, HR 7858, SAO 106248[9] | |
| Database references | |
| SIMBAD | data |
The stellar classification of the visible component is A3 IVs,[3] which matches an A-type subgiant star with narrow absorption lines.[11] It is a suspected chemically peculiar star[12] that is about 64.3%±9.2% of the way through its main sequence lifetime.[8] SIMBAD lists this star as a variable star,[9] although it is not catalogued as such in the GCVS.[13] It has more than double the mass[6] and radius[7] of the Sun, and is radiating 35[8] times the Sun's luminosity from its photosphere at an effective temperature of around 9,355 K.[6]