Messier 28

Location

In the sky it is less than a degree to the northwest of the 3rd magnitude star Kaus Borealis (Lambda ). This cluster is faintly visible as a hazy patch with a pair of binoculars and can be readily found in a small telescope with an 8 cm aperture, showing as a nebulous feature spanning 11.2 arcminutes. Using an aperture of 15 cm, the core becomes visible and a few distinct stars can be resolved, along the periphery. Larger telescopes will provide greater resolution, one of 25 cm revealing a dense 2′ core, with more density within.

It is about 18,300 light-years away from Earth. It is about and its metallicity (averaging −1.32 which means more than 10 times less than our own star), coherency and preponderence of older stellar evolution objects, support its dating to very roughly 12 billion years old. 18 RR Lyrae-type variable stars have been found within.

Discovery

It bore the first discovery of a millisecond pulsar in a globular cluster – PSR B1821–24. This was using the Lovell Telescope at Jodrell Bank Observatory, England. A total of 11 further of these have since been detected in it with the telescope at Green Bank Observatory, West Virginia. As of 2011, these number the third-most in a cluster tied to the Milky Way, following Terzan 5 and 47 Tucanae.

Gallery

File:Nebulous, but no nebula Messier 28.jpg|Messier 28 taken by Hubble. File:Messier 28 Hubble WikiSky.jpg| 2.5' view of M28 taken by Hubble Space Telescope. File:Messier28.jpg|Messier 28 on 2MASS; wide angle File:M28map.png|Map showing location of M28

References and footnotes

References

Footnotes

References

1. "Messier 28".
2. From [[trigonometry]]: radius = distance × sin( diameter_angle / 2 ) = 30 ly
3. "JBO - Stars". [[Jodrell Bank Observatory]].
4. "Nebulous, but no nebula".
5. (2022). "Precise distances from OGLE-IV member RR Lyrae stars in six bulge globular clusters". Astronomy & Astrophysics.
6. (August 1927). "A Classification of Globular Clusters". Harvard College Observatory Bulletin.
7. (November 2011). "Young Radio Pulsars in Galactic Globular Clusters". The Astrophysical Journal.
8. (2004). "Astronomy of the Milky Way: Observer's guide to the northern sky". Springer.
9. (2007). "Illustrated Guide to Astronomical Wonders". [[O'Reilly Media, Inc.]].
10. (February 2001). "Horizontal-Branch Morphology and Dense Environments: Hubble Space Telescope Observations of Globular Clusters NGC 2298, 5897, 6535, and 6626". The Astronomical Journal.
11. (April 2011). "Chandra X-ray Observations of 12 Millisecond Pulsars in the Globular Cluster M28". The Astrophysical Journal.
12. (1979). "Burnham's celestial handbook: an observer's guide to the universe beyond the solar system". [[Dover Publications]].
13. (April 2008). "Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting". [[Monthly Notices of the Royal Astronomical Society]].