Messier 28
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Messier 28 or M28, also known as NGC 6626, is a globular cluster of stars in the center-west of Sagittarius. It was discovered by French astronomer Charles Messier in 1764.[1]Template:Efn He briefly described it as a "nebula containing no star... round, seen with difficulty in 3<templatestyles src="Fraction/styles.css" />1⁄2-foot telescope; Diam 2′."[2]
Location
In the sky it is less than a degree to the northwest of the 3rd magnitude star Kaus Borealis (Lambda Template:Abbreviation). This cluster is faintly visible as a hazy patch with a pair of binoculars[1] and can be readily found in a small telescope with an Script error: No such module "convert". aperture, showing as a nebulous feature spanning 11.2 arcminutes. Using an aperture of Script error: No such module "convert"., the core becomes visible and a few distinct stars can be resolved, along the periphery. Larger telescopes will provide greater resolution,[3] one of Script error: No such module "convert". revealing a dense 2′ core, with more density within.[1]
It is about 18,300 light-years away from Earth.[4] It is about Script error: No such module "val".[5] 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.[6] 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.[7] 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.[8]
Gallery
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2.5' view of M28 taken by Hubble Space Telescope.
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Messier 28 on 2MASS; wide angle
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Map showing location of M28
![Messier 28 taken by Hubble.[9]](/wiki143/index.php?title=File:Nebulous,_but_no_nebula_Messier_28.jpg){kind=link}
See also
References and footnotes
References
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Footnotes
External links
- Globular Cluster M28 @ SEDS Messier pages
- Messier 28, Galactic Globular Clusters Database pageTemplate:WikiSky
Template:Sky Template:Portal bar Template:Messier objects Template:Ngc70