Tag Archives: M7

M7, Ptolemy Cluster



Messier 7 or M7, also designated NGC 6475 and sometimes known as the Ptolemy Cluster, is an open cluster of stars in theconstellation of Scorpius. The cluster is easily detectable with the naked eye, close to the “stinger” of Scorpius (also called Scorpion). With a declination of -34.8°, it is the southernmost Messier object.

M7 has been known since antiquity; it was first recorded by the 1st-century Greek-Roman astronomer Ptolemy, who described it as a nebula in 130 AD. Italian astronomer Giovanni Batista Hodierna observed it before 1654 and counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. English astronomer John Herschel described it as “coarsely scattered clusters of stars”.

Imaging telescopes or lenses: Planewave Instruments 17″ CDK
Resolution: 2928×2915
Dates: Oct. 12, 2014
Frames: 24×120″
Integration: 0.8 hours
Avg. Moon age: 18.55 days
Avg. Moon phase: 84.67%
RA center: 268.453 degrees
DEC center: -34.805 degrees
Orientation: 178.704 degrees
Field radius: 0.634 degrees
Locations: Siding Spring Observatory (SSO), Coonabarabran, Australia
Author: Thomas

M7: Open Star Cluster in Scorpius

Image Credit & Copyright: Lorand Fenyes

M7 is one of the most prominent open clusters of stars on the sky. The cluster, dominated by bright blue stars, can be seen with the naked eye in a dark sky in the tail of the constellation of the Scorpion (Scorpius). M7 contains about 100 stars in total, is about 200 million years old, spans 25 light-years across, and lies about 1000 light-years away. The above deep image, taken last June from Hungary through a small telescope, combines over 60 two-minute exposures. The M7 star cluster has been known since ancient times, being noted by Ptolemy in the year 130 AD. Also visible are a dark dust cloud and literally millions of unrelated stars towards the Galactic center.
NASA APOD 07-Jan-2014