The star cluster in the center of this photograph is known as M7 or NGC 6475. This is a magnitude 3.3 open cluster that is visible to the naked eye near the tail of Scorpius. Known since ancient times, this galactic star cluster is also sometimes called Ptolemy's Cluster. M7 was mentioned by Ptolemy in the Almagest. M7 has the distinction of being the southern-most object in Messier's catalog. It is about 800 light-years away and approaching us at a speed of about 5 miles per second. This star cluster is older than the Pleiades, but is much younger than globular clusters like M4. M7 is projected against a background rich with numerous faint Milky Way stars near the center of our galaxy. A number of dark nebula show up well in this region of the sky.
M6 is the star cluster above M7 and to the right. M6 is located about 3-1/2 degrees northwest of M7. Although smaller, M6 stands out well because a dark nebula provides a high-contrast background for the star cluster. M7 and M6 are two of the largest and brightest galactic star clusters.
The two red nebula to the right of M7 are NGC 6357 and NGC 6334. The bright star to the left of M7 is Kaus Australis.
This photograph was taken with a Mamiya 645AF camera piggyback on a telescope mount at a dark sky site in Southeastern Arizona.
M7 (NGC 6475)
Constellation: Scorpius
RA: 17h 53m 46s Dec: -34d 47' 00" (J2000)
May 11, 2004
Photo by Sid Leach
Sunglow Ranch, Arizona
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