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Star in the constellation Eridanus From Wikipedia, the free encyclopedia
Delta Eridani, which is Latinized from δ Eridani, is the fifth-brightest star in the constellation of Eridanus.
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 03h 43m 14.90088s[1] |
| Declination | –09° 45′ 48.2084″[1] |
| Apparent magnitude (V) | 3.51 - 3.56[2] |
| Characteristics | |
| Evolutionary stage | Subgiant |
| Spectral type | K0 IV[3] |
| U−B color index | +0.69[4] |
| B−V color index | +0.92[4] |
| Astrometry | |
| Radial velocity (Rv) | −6.28±0.09[5] km/s |
| Proper motion (μ) | RA: −93.16[1] mas/yr Dec.: +743.64[1] mas/yr |
| Parallax (π) | 110.61 ± 0.29 mas[1] |
| Distance | 29.49 ± 0.08 ly (9.04 ± 0.02 pc) |
| Absolute magnitude (MV) | 3.77[6] |
| Details[7] | |
| Mass | 1.33±0.07[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[8] km/s |
| Age | 6.194[9] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
The star is visible to the naked eye and has been observed to vary slightly in brightness between magnitudes 3.51 and 3.56,[2] although subsequent observations did not bear this out.[11] It is relatively near to the Sun, with a distance of about 29.5 light years as determined from parallax.[1] The star is drifting closer with a radial velocity of −6 km/s.[5]
Delta Eridani is sometimes called Rana:[12] Rana means "the frog" in Latin, but derivation of this name is uncertain. The name was approved by the International Astronomic Union on 4 April 2022.[13]
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[9] billion years old with 33% more mass than the Sun.[8] 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 is catalogued as a suspected RS Canum Venaticorum variable in 1983,[14] but the activity level for the star is very low that this is considered a mistake.[15] A low projected rotational velocity of under 1 km/s and the lack of radial velocity variation suggests that this star is being viewed from nearly pole-on. However, an examination of the star using interferometry does not detect the presence of a companion at the expected distance.[9]
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.[16] Consequently, the Chinese name for δ Eridani itself is 天苑三 (Tiān Yuàn sān, English: the Third Star of Celestial Meadows.)[17]
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