Eta Microscopii, Latinised as η Microscopii, is a solitary[7] star in the constellation Microscopium. It is visible to the naked eye as a dim, orange-hued star with an apparent visual magnitude of 5.53.[2] The star is located around 910 light-years distant from the Sun based on parallax, and is drifting further away with a radial velocity of +22 km/s.[1]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Microscopium |
| Right ascension | 21h 06m 25.51950s[1] |
| Declination | −41° 23′ 09.4805″[1] |
| Apparent magnitude (V) | 5.53[2] |
| Characteristics | |
| Spectral type | K3 III[3] |
| U−B color index | +1.50[2] |
| B−V color index | +1.35[2] |
| Astrometry | |
| Radial velocity (Rv) | +22.29±0.13[1] km/s |
| Proper motion (μ) | RA: +28.760[1] mas/yr Dec.: −11.548[1] mas/yr |
| Parallax (π) | 3.5657 ± 0.1149 mas[1] |
| Distance | 910 ± 30 ly (280 ± 9 pc) |
| Absolute magnitude (MV) | −1.13[4] |
| Details | |
| Mass | 1.2[5] M☉ |
| Radius | 47.41+0.95 −5.67[1] R☉ |
| Luminosity | 735±28[1] L☉ |
| Surface gravity (log g) | 1.1[5] cgs |
| Temperature | 4,365+287 −43[1] K |
| Metallicity [Fe/H] | −0.31[5] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an aging giant star with a stellar classification of K3 III,[3] indicating that it has exhausted the supply of hydrogen at its core then cooled and expanded. At present it has around 47[1] times the girth of the Sun. The star is radiating 735 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,365 K.[1]
Multiple star catalogues list two optical companions.[8] Two arc-minutes away, the 8th magnitude HD 200733 is a main sequence star much closer to Earth than η Microscopii.[9] A 14th-magnitude star one arc-minute from η Microscopii is a background object.[10]
References
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