Messier 28
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| 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 | |
| Mass: | ( M☉) |
| Radius: | 30 ly[2] |
| VHB: | |
| Estimated age: | |
| 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.
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 1987, M28 became the second globular cluster where a millisecond pulsar was discovered (the first was Globular Cluster M4).
[edit] External links
[edit] References
- ^ a b c d SIMBAD Astronomical Database. Results for NGC 6626. Retrieved on November 16, 2006.
- ^ distance × sin( diameter_angle / 2 ) = 30 ly. radius
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