Eta Tucanae, Latinized from η Tucanae, is a probable binary star[6] system in the southern constellation of Tucana, a few degrees to the north of Epsilon Tucanae. It is visible to the naked eye as a dim, white-hued point of light with an apparent visual magnitude of +5.00.[2] parallax measurements provide a distance estimate of about 154 light years from the Sun, and it is drifting further away with a mean radial velocity of +32.5 km/s.[4] It is a member of the 30 million year old Tucana-Horologium association of co-moving stars.[6][2]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Tucana |
Right ascension | 23h 57m 35.07852s[1] |
Declination | −64° 17′ 53.6229″[1] |
Apparent magnitude (V) | +5.00[2] |
Characteristics | |
Spectral type | A1V[2] |
U−B color index | +0.08[3] |
B−V color index | +0.06[3] |
Astrometry | |
Radial velocity (Rv) | +32.50[4] km/s |
Proper motion (μ) | RA: +78.850[1] mas/yr Dec.: −62.049[1] mas/yr |
Parallax (π) | 21.2425 ± 0.3639 mas[1] |
Distance | 154 ± 3 ly (47.1 ± 0.8 pc) |
Absolute magnitude (MV) | 1.62[5] |
Details | |
Mass | 1.94[6] M☉ |
Radius | 1.8[7] R☉ |
Luminosity | 23[8] L☉ |
Surface gravity (log g) | 4.31[9] cgs |
Temperature | 9,057[8] K |
Rotational velocity (v sin i) | 190[6] km/s |
Other designations | |
Database references | |
SIMBAD | data |
The radial velocity for Eta Tucanae displays strong oscillations, suggesting this is a spectroscopic binary system. A companion was directly detected in 2014, but this result has some unexplained anomalies.[6] The primary component is an A-type main-sequence star with a stellar classification of A1V.[2] It is spinning rapidly with a projected rotational velocity of 190 km/s,[6] giving it an equatorial bulge that is 15% larger than the polar radius.[11] The star has 1.9[6] times the mass of the Sun and 1.8[7] times the Sun's radius. It is radiating 23[8] times the luminosity of the Sun from its photosphere at an effective temperature of 9,057 K.[8]
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