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M28

NGC 6626

Proper NameNone
Messier NumberM28
NGC/IC NumberNGC 6626
Other DesignationsN/A
ConstellationSagittarius
Right Ascension18h 25m 37s
Declination-24° 51' 25"
Distancec.17,900 light years
c.5,500 parsecs
MagnitudeApparent: +6.8
Absolute: -6.9
DiameterApparent: 3' 54"
Actual: 21 light years
Optimum VisibilityJuly
NotesAn ancient globular cluster with a dense core, lying close to the plane of the Milky Way in the region of the Galaxy's nucleus. It is home to several pulsars, as well as RR Lyrae pulsating variables that help to determine its distance with considerable accuracy.

A Globular Cluster in Sagittarius, a little to the west of the star Kaus Borealis. It occupies a region of the sky in the direction of the Galaxy's Core busy with clusters and nebulae; near M28 in the sky is another Globular Cluster, M22, as well as the open cluster M21 and the Trifid Nebula. M28 is nearly 18,000 light years from the Solar System, placing it about 9,000 light years from the centre of the Galaxy.

M28 has a dense core, from which stars extend outward to create a sphere with an angular diameter of more than eleven arc minutes; given its distance, this makes the cluster roughly sixty light years from edge to edge. The stars of the cluster are very ancient, dating back some twelve billion years, meaning that they formed no more than about a billion years after the origins of the Milky Way itself.

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