NGC 339

NGC 339 is a globular cluster in the constellation Tucana the Toucan. It is located both visually and physically in the Small Magellanic Cloud, being only about 10,000 ± 12,000 light years (3,000 ± 3,000 parsecs) closer than the cloud. It is rather prominent, being the brightest cluster in the southern reaches of the cloud. It was discovered by John Herschel on September 18, 1835.^[1] It was observed in 2005 by the Hubble Space Telescope. Its apparent V-band magnitude is 12.12, but at this wavelength, it has 0.19 magnitudes of interstellar extinction.^[3]

NGC 339
NGC 339 imaged by the Hubble Space Telescope
Observation data (J2000.0 epoch)
Class	~VIII
Constellation	Tucana
Right ascension	00h 57m 45.0s
Declination	−74° 28′ 20″[1]
Distance	186 ± 4 kly (57 ± 1 kpc[2])
Apparent magnitude (V)	12.12[3]
Apparent dimensions (V)	2.2 arcminutes[1]
Physical characteristics
Mass	5.7×104[3] M☉
Radius	119 ± 3 ly (36.5 ± 0.7 pc[4])
Estimated age	6.30±0.50 Gyr[3]
Other designations	ESO 029-SC 02[2]
See also: Globular cluster, List of globular clusters

NGC 339 is about 6.3 billion years old. Its estimated mass is 5.7×10⁴ M_☉, and its total luminosity is 7.2×10⁴ L_☉, leading to a mass-to-luminosity ratio of 0.79 M_☉/L_☉.^[3] All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.^[3]