NGC 6624

NGC 6624
The globular cluster NGC 6624. Credit Hubble Space Telescope
Observation data (J2000 epoch)
Constellation	Sagittarius
Right ascension	18^h 23^m 41^s
Declination	−30° 21′ 39″
Distance	25.8 ± 1.1 kly (7.91 ± 0.34 kpc)
Apparent magnitude (V)	7.6
Apparent dimensions (V)	8.8 arcminutes[1]
Physical characteristics
Metallicity	${\displaystyle {\begin{smallmatrix}\left[{\ce {Fe}}/{\ce {H}}\right]\end{smallmatrix}}}$ = -0.56 ± 0.27[2] dex

NGC 6624 is a globular cluster in the constellation Sagittarius. It was discovered on 24 June 1784 by the astronomer William Herschel. It is given an apparent magnitude of 7.6 to 8.5.^[3] Six pulsars are known in NGC 6624. The first of these to be discovered was PSR J1823-3021A. This globular cluster also contains 4U 1820-30, a low-mass X-ray binary with an orbital period of only 11.5 minutes.

NGC 6624 is visible as a hazy spot with a small telescope, and appears as a star-like object with binoculars. Its core appears significantly condensed.^[1] It is located 0.8 degrees southeast of the star Delta Sagittarii,^[4] and is about 1.17 kpc (3.8 kly) from the Galactic center.^[2]

Map showing location of NGC 6624

References

1. O'Meara, Steve (2007). Steve O'Meara's Herschel 400 Observing Guide. Cambridge: Cambridge University Press. p. 236. ISBN 978-0-521-85893-9.
2. Sofue, Yoshiaki. The Central Regions of the Galaxy and Galaxies. Netherlands: Kluwer Academic Publishers. p. 37. ISBN 0-7923-5061-8.
3. It is given a diameter of 6 to 8.5 arcminutes, and class VI with stars magnitude 14 and dimmer. It is less than a degree southeast of star Delta Sagittarii. O'Meara, Stephen James (2007). Deep Sky Companions: Hidden Treasures. Cambridge University Press. p. 452.
4. Bakich, Michael E. (2010). 1001 Celestial Wonders to See Before You Die: The Best Sky Objects for Star Gazers. Springer. p. 249. doi:10.1007/978-1-4419-1777-5. ISBN 978-1-4419-1776-8.

• Robert Burnham, Jr, Burnham's Celestial Handbook: An observer's guide to the universe beyond the solar system, vol 3, p.1557

External links

• NGC 6624