NGC 330

NGC 330 is an open cluster in the Small Magellanic Cloud. It is located in the constellation Tucana. It was discovered on 1 August 1826 by James Dunlop. It was described by Dreyer as "a globular cluster, very bright, small, a little extended, stars from 13th to 15th magnitude."^[4] At an aperture of 31.0 arcseconds, the apparent V-band magnitude is 9.60, but at this wavelength, it also has 0.36 magnitudes of interstellar extinction.^[2]

NGC 330
The star cluster NGC 330 Credit: Hubble Space Telescope
Observation data (J2000 epoch)
Right ascension	00h 56m 17.6s[1]
Declination	−72° 27′ 47″[1]
Distance	182000[1]
Apparent magnitude (V)	9.60[2]
Apparent dimensions (V)	2.8′ × 2.5′[3]
Physical characteristics
Mass	5.4×104[2] M☉
Estimated age	0.09±0.05 Gyr[2]
Other designations	ESO 029-SC 024.[1]
Associations
Constellation	Tucana
See also: Open cluster, List of open clusters

NGC 330 is quite young, at about 40 million years old, and has a large proportion of Be stars.^[5] Its estimated mass is 5.4×10⁴ M_☉, and its total luminosity is 8.93×10⁵ L_☉, leading to a mass-to-luminosity ratio of 0.06 M_☉/L_☉.^[2] All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.^[2] About 34% of the massive star population in NGC 330 is estimated to be in a close binary star system; this is lower than clusters in the Large Magellanic Cloud and the Milky Way, but it is unknown if this is because NGC 330 is metal-poor or is older than the compared clusters.^[5]