Delta Eridani
Star in the constellation Eridanus
From Wikipedia, the free encyclopedia
Delta Eridani, Latinized from δ Eridani, also named Rana, is the fifth-brightest star in the constellation of Eridanus.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 03h 43m 14.90054s[1] |
| Declination | −09° 45′ 48.2110″[1] |
| Apparent magnitude (V) | 3.53[2] |
| Characteristics | |
| Evolutionary stage | Subgiant |
| Spectral type | K0 IV[3] |
| U−B color index | +0.69[4] |
| B−V color index | +0.92[4] |
| Variable type | none[2] |
| Astrometry | |
| Radial velocity (Rv) | −6.28±0.09[5] km/s |
| Proper motion (μ) | RA: −93.634 mas/yr[1] Dec.: +744.360 mas/yr[1] |
| Parallax (π) | 110.0254±0.1944 mas[1] |
| Distance | 29.64 ± 0.05 ly (9.09 ± 0.02 pc) |
| Absolute magnitude (MV) | 3.77[6] |
| Details[7] | |
| Mass | 1.215[8] M☉ |
| Radius | 2.35±0.01 R☉ |
| Luminosity | 3.17±0.09 L☉ |
| Surface gravity (log g) | 3.66±0.1 cgs |
| Temperature | 5,027±48 K |
| Metallicity [Fe/H] | +0.07±0.03 dex |
| Rotational velocity (v sin i) | 0.7±0.6[9] km/s |
| Age | 6.194[8] Gyr |
| Other designations | |
| Rana, δ Eri, 23 Eridani, NSV 1246, BD−10°728, GJ 150, HD 23249, HIP 17378, HR 1136, SAO 130686, LHS 1581[10] | |
| Database references | |
| SIMBAD | data |
The star is visible to the naked eye with an apparent magnitude of 3.54. It is relatively near to the Sun, with a distance of about 29.6 light-years as determined from parallax.[1] The star is drifting closer with a radial velocity of −6 km/s.[5]
Nomenclature
Delta Eridani is sometimes called Rana;[11] Rana means frog in Latin. This name first appeared as Rana Secunda, the "second frog", in Giuseppe Piazzi's star catalogue; this was likely a misattributed name for Beta Ceti (Diphda), known as the "second frog" in Arabic.[12] The name Rana was approved by the IAU Working Group on Star Names on 4 April 2022.[13]
In Chinese, 天苑 (Tiān Yuàn), meaning Celestial Meadows, refers to an asterism consisting of δ Eridani, γ Eridani, π Eridani, ε Eridani, ζ Eridani, η Eridani, π Ceti, τ1 Eridani, τ2 Eridani, τ3 Eridani, τ4 Eridani, τ5 Eridani, τ6 Eridani, τ7 Eridani, τ8 Eridani and τ9 Eridani.[14] Consequently, the Chinese name for δ Eridani itself is 天苑三 (Tiān Yuàn sān, English: the Third Star of Celestial Meadows.)[15]
Characteristics
The stellar classification of this star is K0 IV,[3] matching a subgiant star that has exhausted its core hydrogen. This has caused the star to expand and become cooler than a comparable main sequence star. Stellar modelling indicates it is near the end of the subgiant stage and about to transition into a giant. It is an estimated six billion years old[8] with 33% more mass than the Sun.[9] The star has 2.35 times the size of the Sun and is radiating three times the Sun's luminosity from its photosphere at an effective temperature of 5,022 K.[7]
Delta Eridani was catalogued as a suspected RS Canum Venaticorum variable in 1983,[16] varying slightly in brightness between magnitudes 3.51 and 3.56,[17] although subsequent observations did not bear this out[18] and an examination of the star using interferometry did not detect the presence of a companion at the expected distance.[8] Thus, this classification is now considered erroneous.[19] The star has a very low level of chromospheric activity.[19] A low projected rotational velocity of under 1 km/s and the lack of radial velocity variation suggest that this star is being viewed from nearly pole-on.[8]