Eta Delphini

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]

η Delphini

Location of η Delphini (circled)
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]