54 Eridani
Star in the constellation Eridanus
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54 Eridani is a suspected astrometric binary[11] star system located around 400 light years from the Sun in the barely equatorial-southern constellation of Eridanus. It is visible to the naked eye as a faint, reddish hued star with a baseline apparent visual magnitude of 4.32.[2] The object is moving closer to the Earth with a heliocentric radial velocity of −33 km/s.[2]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Eridanus |
| Right ascension | 04h 40m 26.51159s[1] |
| Declination | −19° 40′ 17.3723″[1] |
| Apparent magnitude (V) | 4.32[2] |
| Characteristics | |
| Evolutionary stage | asymptotic giant branch[3] |
| Spectral type | M3/4 III[4] |
| U−B color index | +1.80[5] |
| B−V color index | 1.599±0.021[2] |
| Variable type | SRb[6] |
| Astrometry | |
| Radial velocity (Rv) | −32.9±0.8[2] km/s |
| Proper motion (μ) | RA: +29.13[7] mas/yr Dec.: −96.42[7] mas/yr |
| Parallax (π) | 8.2063±0.2709 mas[1] |
| Distance | 400 ± 10 ly (122 ± 4 pc) |
| Absolute magnitude (MV) | −0.93[2] |
| Details | |
| Mass | 3.95[8] M☉ |
| Radius | 69+12 −6[1] R☉ |
| Luminosity | 2,239[8] L☉ |
| Surface gravity (log g) | 1.98[9] cgs |
| Temperature | 3,500[8] K |
| Metallicity [Fe/H] | 0.00[8] dex |
| Other designations | |
| DM Eridani, BD−19°988, GC 5695, HD 29755, HIP 21763, HR 1496, SAO 149818, WDS J04404-1940[10] | |
| Database references | |
| SIMBAD | data |
The variability of 54 Eridani was announced by Benjamin Apthorp Gould in his Uranometria Argentina, published in 1879.[13] But it was not given its variable star designation, DM Eridani, until nearly 100 years later, in 1973.[14] The visible component is an aging red giant star, currently on the asymptotic giant branch,[3] with a stellar classification of M3/4 III.[4] It is a semiregular variable star of subtype SRb, ranging in magnitude from 4.28 down to 4.36.[6] The star has pulsation periods of 18.8 and 45.5 days, each with an amplitude of 0.019 in magnitude.[12] With the hydrogen and helium at its core exhausted, the star has expanded to around 69 times the Sun's radius and it is radiating 1,021 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3,915 K.[1]
It was the second-brightest star in the obsolete constellation of Sceptrum Brandenburgicum after 53 Eridani.