Beta Tucanae

β^{1, 2} Tucanae

Location of β Tucanae group.
Observation data Epoch J2000.0      Equinox J2000.0
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[7]
β Tuc A
Mass	3.84 M☉
β Tuc B
Mass	0.40 M☉
β Tuc C
Mass	2.76 M☉
β Tuc D
Mass	1.94 M☉
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
SIMBAD	data
	β1
	β2

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.^[8] The system is approximately 140 light years from Earth.

The two brightest stars, Beta¹ Tucanae and Beta² 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, 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.

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 Beta¹, being 2.4 arcseconds, or at least 100 AU away. Beta²'s companion, the 6th magnitude Beta Tucanae D, is another A-type star which is separated by approximately 0.38 arcseconds (16 AU) from Beta².

Beta³ Tucanae is a 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.

Both components of the binary system are white A-type main sequence stars and they have apparent magnitudes of +5.8 and +6.0. They are separated by 0.1 arcseconds, or at least 4 astronomical units.

Beta³ Tucanae has an infrared excess, suggesting the presence a debris disk around the primary star. The distance of the other star to the debris disk is not known.^[9]

Beta¹a's binary companion, Beta¹b, orbits at a bit over three times Neptune's distance from the Sun. The Beta² pair is located over ten times further away. The pair is separated by less than the distance from the Sun to Uranus. The Beta³ pair is much further out, at one-and-a-half times the distance of Proxima Centauri from the main Alpha Centauri pair. The Beta³ pair are separated by less distance than the Sun and Jupiter.