Beta Tucanae

β¹^,² Tucanae

Location of β Tucanae group.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Tucana
Right ascension	00h 31m 32.7s
Declination	−62° 57′ 29″
Apparent magnitude (V)	β¹: +4.36 β²: +4.53
Distance	140 ± 3 ly (43 ± 1 pc)
Spectral type	AB: A2V+B9V CD: A2V+A7V
Other designations
HR 126 + HR 126, HD 2884 + HD 2885, CP−63 50, HIP 2484 + HIP 2487, SAO 248201 + SAO 248202, GC 625, CCDM 00316-6258

Beta Tucanae (β Tuc, 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. The system is approximately 140 light years from Earth.

The two brightest stars, Beta-1 Tucanae and Beta-2 Tucanae, also referred to as Beta Tucanae A and Beta Tucanae C, are 27 arcseconds, or at least 1100 astronomical units (AU) apart. They are both main sequence dwarfs, Beta-1 a blue-white B-type star with an apparent magnitude of +4.36, and Beta-2 a white A-type star with an apparent magnitude of +4.53.

Both of these bright stars have at least one closer main sequence companion. Beta Tucanae B is a magnitude +13.5 M3-type star which is a close companion to Beta-1, being 2.4 arcseconds, or at least 100 AU away. Beta-2's companion, the 6th magnitude Beta Tucanae D, is another A-type star which is separated by approximately 0.38 arcseconds (16 AU) from Beta-2.

AB: 5.8 + 6.0

Beta-3 Tucanae is a binary star which is separated from Beta-1 and Beta-2 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's not clear how tightly Beta-3 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.