Messier 28

Messier 28
Messier 28 by Hubble Space Telescope; 2.5′ view Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Class	IV
Constellation	Sagittarius
Right ascension	18h 24m 32.89s[1]
Declination	-24° 52′ 11.4″[1]
Distance	18.3 kly (5.6 kpc)
Apparent magnitude (V)	+7.66[1]
Apparent dimensions (V)	11′.2
Physical characteristics
Radius	30 ly[2]
Notable features	Contains pulsar
Other designations	M 28, NGC 6626, GCl 94[1]
See also: Globular cluster, List of globular clusters

Messier 28 (also known as M28 or NGC 6626) is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1764. In the sky it is very close to the 3rd magnitude star Kaus Borealis.

M28 is at a distance of about 18,000 to 19,000 light-years away from Earth. 18 RR Lyrae type variable stars have been observed in this cluster. In 1986, M28 became the first globular cluster where a millisecond pulsar was discovered (by the Lovell Telescope at Jodrell Bank Observatory).^[3]

Messier 28 on 2MASS; wide angle

External links

• Globular Cluster M28 @ SEDS Messier pages
• Messier 28, Galactic Globular Clusters Database page
• Messier 28 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

References

1. ^ ^{a b c d} "SIMBAD Astronomical Database". Results for NGC 6626. http://simbad.u-strasbg.fr/Simbad. Retrieved 2006-11-16. 
2. ^ distance × sin( diameter_angle / 2 ) = 30 ly radius
3. ^ "JBO - Stars". Jodrell Bank Observatory. http://www.jb.man.ac.uk/tech/lovell/aunstar.html. Retrieved 2007-06-01. 

Coordinates: 18^h 24^m 32.89^s, −24° 52′ 11.4″