| NGC 2257 | |
|---|---|
 | |
| Observation data (J2000epoch) | |
| Constellation | Dorado |
| Right ascension | 06h 30m 12.62s[1] |
| Declination | −64° 19′ 40.0″[1] |
| Apparent magnitude(V) | 12.62[1] |
| Apparent dimensions(V) | 3.4′[2] |
| Physical characteristics | |
| Mass | 1.01×105[1] M☉ |
| Estimated age | 12.74±2.00 Gyr[1] |
| Other designations | KMHK 1756, [SL63] 895, ESO 87-24, LW 481[3] |
| See also:Globular cluster,List of globular clusters | |
NGC 2257 is aglobular cluster that lies on the outskirts of theLarge Magellanic Cloud (LMC). It was discovered in 1834 byJohn Herschel. The compiler of theNew General Catalogue,John Louis Emil Dreyer, described this cluster as "faint, considerably large, round, very gradually a little brighter middle, mottled but not resolved, 17.0 seconds of time diameter."[4] At an aperture of 30.5 arcseconds, its apparent V-band magnitude is 12.62, but at this wavelength, it has 0.12 magnitudes ofinterstellar extinction.[1]
NGC 2257 is quite old, at about 12.74 billion years old. Its estimated mass is1.01×105 M☉, and its total luminosity is5.1×104 L☉, leading to a mass-to-luminosity ratio of 2.00M☉/L☉.[1] All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.[1]
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