The globular star cluster M12 in Ophiuchus is a fairly bright magnitude 6.1 star cluster that is about 16 arc-minutes in diameter. M12 orbits the Milky Way galaxy in an eliptical orbit in which it periodically passes through the plane of the galaxy near the central core. Observations by astronomers using the VLT telescope in Chile revealed that this globular cluster has apparently had as many as 1 million stars stripped away from it by the gravitational pull of the Milky Way during passes near the core of our galaxy. The cluster is now devoid of low mass stars. The stripping process is a slow one, and the star cluster is expected to last another 4.5 billion years before all of its stars are completely stripped away.
M12 was discovered by Messier in May 1764, and his crude telescope did not resolve it into stars. Messier spent much of his time searching for comets. This globular cluster and other objects that he viewed through his small telescope looked similar to a comet. Therefore, he added it as the 12th item on his list of objects to be avoided when looking for comets. This object was first identified as a star cluster by Sir William Herschel in 1783.
M12 is about 23,000 light-years away. This cluster is about 2000 light-years from the M10 star cluster. If someone lived on a planet orbiting one of the stars in M10, he or she would see M12 as a spectacular 2nd magnitude star cluster that would be visible to the naked eye.
This is an LRGB color composite CCD image taken with a Takahashi FCT-150 and an SBIG ST-8E. The images were acquired automatically using a plan executed by the Astronomer Control Panel software. The luminance images were binned 1x1, and the red, green and blue filtered images were binned 2x2.
M12 (NGC 6218)
Constellation: Ophiuchus
RA: 16h 47m 14s Dec: -01d 56' 50" (J2000)
April 20, 2005
Image by Sid Leach
Scottsdale, Arizona
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