Messier 69. NGC 6637

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Messier 69 (M69) is a metal-rich globular cluster located 29,700 light years away, in the constellation Sagittarius. Its metallicity is just one fifth of that of the Sun, but approximately ten times that of the typical globulars. The main reason why this cluster is so metal-rich lays on its proximity to the bulge of the galaxy. All globular clusters in the bulge or its proximity have higher metallicities, compared to other globulars. Another peculiarity of this cluster is its tidal radius. This is the radius of a sphere, inside which, all stars orbit the clusters center of gravity. The fact of its proximity to the galactic center, makes it easier for the cluster to loose stars located in the periphery that get trapped by the black hole’s intense gravity. This means that the tidal radius is smaller compared to other globulars. In this case, it is 7.2 light years (or 8.3 arcmin at this distance).


Additional Information


Name(s): Messier 69, M69, NGC 6637

Type: Globular Cluster

RA:  18h 31m 22s

Dec: -32º 20’ 48”

Constellation: Sagittarius

Size (arcmin): 9×9 arcmin

Magnitude: +8.3

Distance: 29,700 ly


Date: 2021-09-22

Location:, SSO near Coonabarabran, NSW Australia

Size (arcmin): 39×26 arcmin

Telescope: 20” f/4.5 Reflector

Camera: FLI PL6303E (3072x2048pix)

Guiding: N/A

Total exposure: 3h 45m (L: 1.5h; RGB: 45 min each)

Processing: CCDStack, Photoshop CC 2021


Processing: CCDStack, Photoshop CC 2022

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