47 Tucanae

47 Tucanae or 47 Tuc (also designated as NGC 104 and Caldwell 106) is a globular cluster located in the constellation Tucana. It is about 4.45 ± 0.01 kpc (15,000 ± 33 ly) away from Earth, and 120 light years in diameter. 47 Tuc can be seen with the naked eye, with an apparent magnitude of 4.1. It appears about 44 arcminutes across including its far outreaches. Due to its far southern location, 18° from the south celestial pole, it was not catalogued by European astronomers until the 1750s, when the cluster was first identified by Nicolas-Louis de Lacaille from South Africa.

47 Tucanae
After Omega Centauri, 47 Tucanae is the brightest globular cluster in the night sky.
Observation data (J2000 epoch)
Class	III
Constellation	Tucana
Right ascension	00h 24m 05.67s
Declination	−72° 04′ 52.6″
Distance	4.45 ± 0.01 kpc (14,500 ± 32.6 ly)
Apparent magnitude (V)	+4.09
Apparent dimensions (V)	43.8′
Physical characteristics
Mass	7.00×105 M☉
Radius	60 ly
VHB	14.2
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = −0.78 dex
Estimated age	13.06 Gyr
Notable features	2nd brightest globular cluster after Omega Centauri
Other designations	ξ Tuc, NGC 104, Caldwell 106, Mel 1, GCl 1, 1RXS J002404.6-720456

47 Tucanae is the second brightest globular cluster after Omega Centauri, and telescopically reveals about ten thousand stars, many appearing within a small dense central core. The cluster may contain an intermediate-mass black hole.