M7
Ptolemy's Cluster
Properties
Position & Identifiers
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M7 · 22.2′ diameter · N up, E left
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About M7
Description
Ptolemy's Cluster is a large, bright open cluster in Scorpius, about 980 light-years from Earth — one of the nearest Messier clusters. It contains about 80 stars spread over nearly a degree of sky (roughly 25 light-years across). The cluster is estimated to be 200 million years old, and its brightest members are blue-white B-type stars.
Observing Tips
Located about 4.5 degrees northeast of the Scorpion's stinger. Easily visible to the naked eye as a bright, large patch. Best viewed with binoculars or a wide-field telescope at very low power (20-30x), as the cluster spans about 80 arcminutes. The rich Milky Way background adds to the visual splendor. Nearby M6 makes an excellent pair. Best observed from June through August, but sits low for northern observers.
History
One of the earliest deep-sky objects recorded — Ptolemy described it around 130 AD as 'the nebula following the sting of Scorpius,' giving it its common name. Giovanni Battista Hodierna recorded it before 1654. Charles Messier cataloged it in 1764.
Fun Facts
Ptolemy's Cluster is one of the most ancient deep-sky objects known to humanity — Ptolemy's description from nearly 2,000 years ago makes it one of the first 'nebulae' ever recorded. The cluster sits in front of a rich dark nebula, which provides a beautiful dark background that makes the bright stars stand out.
Community Photos (1)
Credit: Credit: ESO. License: CC BY 3.0. (Wikimedia Commons)
Skybred Feb 28, 2026