NGC 6540

NGC 6540 is a globular cluster in the constellation Sagittarius. Its apparent magnitude is 9.3[2] and its diameter is about 9.5 arcminutes, with 12 faint stars visible. It is about 17,000 light years away from Earth and was discovered by Wilhelm Herschel on May 24, 1784 with an 18.7-inch mirror telescope, who described the cluster as "pretty faint, not large, crookedly extended, easily resolvable".

NGC 6540
Observation data (J2000 epoch)
Constellation	Sagittarius
Right ascension	18^h 06^m 08.60^s[1]
Declination	−27° 45′ 55.0″[1]
Distance	17.3 kly (5.3 kpc)
Apparent magnitude (V)	9.30[2]
Physical characteristics
Absolute magnitude	-6.35[2]
Radius	4.75' x 4.75'[2]
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = -1.35[3] dex
Other designations	Cr 364, Djorg 3, VDBH 258, C 1803-278[1]

References

1. "NGC 6540". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 7 January 2017.
2. "NGC 6540". Retrieved 15 January 2016.
3. "A Galactic Globular Clusters Database: NGC 6540". Retrieved 15 January 2017.

• Robert Burnham, Jr, Burnham's Celestial Handbook: An observer's guide to the universe beyond the solar system, vol 3, p.1556

External links

• NGC 6540