Beta Tucanae
Star system in the constellation Tucana
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Beta Tucanae, Latinized from β Tucanae, is a group of six stars which appear to be at least loosely bound into a system in the constellation Tucana. Three of the stars are luminous and distinct enough to have been given their own Bayer designations, β1 Tucanae through β3 Tucanae.[11] The system is approximately 140 light years from Earth.
 | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Tucana |
| β1 Tuc (β Tuc AB) | |
| Right ascension | 00h 31m 32.6709s[1] |
| Declination | −62° 57′ 29.587″[1] |
| Apparent magnitude (V) | +4.37[2] |
| β2 Tuc (β Tuc CD) | |
| Right ascension | 00h 31m 33.4223s[1] |
| Declination | −62° 57′ 56.134″[1] |
| Apparent magnitude (V) | +4.54[2] |
| Characteristics | |
| β1 Tuc | |
| Spectral type | B9V[3] |
| β2 Tuc | |
| Spectral type | A2V + A7V[4] |
| Astrometry | |
| β1 Tuc | |
| Parallax (π) | 23.2596±0.2471 mas[5] |
| Distance | 140 ± 1 ly (43.0 ± 0.5 pc) |
| β2 Tuc | |
| Parallax (π) | 19.5923±0.9674 mas[6] |
| Distance | 166 ± 8 ly (51 ± 3 pc) |
| Details | |
| β Tuc A | |
| Mass | 3.84[7] M☉ |
| Radius | 2.73[8] R☉ |
| Luminosity | 39[9] L☉ |
| Surface gravity (log g) | 4.37[9] cgs |
| Temperature | 10,726[9] K |
| Rotational velocity (v sin i) | 170[8] km/s |
| β Tuc B | |
| Mass | 0.40[7] M☉ |
| β Tuc Ca | |
| Mass | 2.0[10] M☉ |
| Radius | 1.6[10] R☉ |
| Temperature | 9,200[10] K |
| β Tuc Cb | |
| Mass | 1.45[10] M☉ |
| Radius | 1.4[10] R☉ |
| Temperature | 7,000[10] K |
| β Tuc D | |
| Mass | 1.45[10] M☉ |
| Radius | 1.4[10] R☉ |
| Temperature | 7,000[10] K |
| Other designations | |
| β Tuc, CPD−63°50, GC 625, HR 126, CCDM 00316-6258 | |
| β1: HD 2884, HIP 2484, SAO 248201 | |
| β2: HD 2885, HIP 2487, SAO 248202 | |
| Database references | |
| β1 | |
| β2 | |
β1, 2 Tucanae
The two brightest stars, Beta1 Tucanae and Beta2 Tucanae, also referred to as Beta Tucanae A (or AB) and Beta Tucanae C (or CD), are 27 arcseconds, or at least 1100 astronomical units (AU) apart. They are both main sequence dwarfs, Beta1 a blue-white B-type star with an apparent magnitude of +4.36, and Beta2 a white A-type star with an apparent magnitude of +4.53.
Beta1 Tucane is a binary while Beta2 is a trinary. Beta Tucanae1 B is a magnitude +13.5 star which is a close companion to Beta1, being 2.4 arcseconds, or at least 100 AU away.[3] Beta Tucanae C is a close binary of components Ca and Cb, separated by 0.6 AU.[10] The 6th magnitude Beta Tucanae D, is another A-type star which is separated by approximately 0.38 arcseconds (16 AU) from Beta Tucanae C.[3]
| β1 A | |||||||||||||||||
| Sep = ~100 au | |||||||||||||||||
| β1 B | |||||||||||||||||
| Sep = ~1,200 au | |||||||||||||||||
| β2 Ca | |||||||||||||||||
| Sep = 0.59 au | |||||||||||||||||
| β2 Cb | |||||||||||||||||
| Sep = 22 au | |||||||||||||||||
| β2 D | |||||||||||||||||
| Sep = ~23,000 au | |||||||||||||||||
| β3 | |||||||||||||||||
Hierarchy of orbits in the β Tucanae system[10]
β3 Tucanae
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Tucana |
| Right ascension | 00h 32m 43.905s[12] |
| Declination | −63° 01′ 53.40″[12] |
| Apparent magnitude (V) | +5.09[13] |
| Characteristics | |
| Spectral type | A0V[14] |
| Astrometry | |
| Radial velocity (Rv) | 3.60[12] km/s |
| Proper motion (μ) | RA: +86.541[12] mas/yr Dec.: −50.115[12] mas/yr |
| Parallax (π) | 21.6794±0.0683 mas[12] |
| Distance | 150.4 ± 0.5 ly (46.1 ± 0.1 pc) |
| Absolute magnitude (MV) | +1.8[15] |
| Details | |
| Mass | 2.0[12] M☉ |
| Radius | 1.7[12] R☉ |
| Luminosity | 19[12] L☉ |
| Surface gravity (log g) | 4.14[12] cgs |
| Temperature | 9,275[12] K |
| Metallicity [Fe/H] | 0.17[16] dex |
| Rotational velocity (v sin i) | 100[16] km/s |
| Other designations | |
| CPD−63°52, GC 651, HD 3003, HIP 2578, HR 136, SAO 248208, CCDM 00327-6302 | |
| Database references | |
| SIMBAD | data |
Beta3 Tucanae is a suspected binary star which is separated from Beta1 and Beta2 Tucanae by 9 arcminutes on the sky, which puts the two systems at least 23 000 astronomical units (AU) or 0.37 light years apart. It is not clear how tightly Beta3 Tucanae is gravitationally bound to the rest of the β Tucanae system, but all the stars have similar distances from Earth and have the same proper motion on the sky, indicating they are gravitationally influencing each other to some degree.
In 1926, Beta3 Tucanae was reported to be a binary, with two components of magnitudes 5.7 and 6.1 separated by 0.1″,[17] although more recent observations could not confirm this.[14][18] At the separation of 0.1″ they would be separated by at least 4 au.[19]
Beta3 Tucanae has an infrared excess, suggesting the presence a debris disk around the primary star.[19]