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NGC 6656 (Globular Cluster, M22)


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NGC 6656, M22
Globular Cluster (球状星団)
Gb VII


別名 (Other names)
GCL 99, ESO 523-SC4, Messier 22

明るさ (Brightness)
5.2等級

星座 (Constellation)
いて座 (Sgr) (Sagittarius)

距離 (Distance)
10,000光年 (10,000 light-years)

NGC 6656 (M22) is a globular cluster located 10,000 light years from the Earth in the constellation Sagittarius.

NGC 6656 (Globular Cluster, M22) : Picture

NGC 6656 (Globular Cluster, M22)
NGC 6656 (Globular Cluster, M22)
(C) N.A.Sharp, REU program/NOAO/AURA/NSF
M22, or NGC6656, a globular cluster in the constellation Sagittarius. A conspicuous naked eye object, M22 is the brightest globular cluster visible from the northern hemisphere. As such, it seems to be the first known globular, having been observed by A.Ihle in 1665. It also appears in John Bevis' Uranographia Britannica. About 10,000 light-years from us, M22 is about 65 light-years across. This color picture was made from CCD images taken in June 1995 at the Burrell Schmidt telescope of the Warner and Swasey Observatory of the Case Western Reserve University, located on Kitt Peak in southwestern Arizona, during the Research Experiences for Undergraduates (REU) program operated at the Kitt Peak National Observatory and supported by the National Science Foundation.

Globular Cluster M22
Globular Cluster M22 from CFHT
(C) Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT
The globular cluster M22, pictured above, contains over 100,000 stars. These stars formed together and are gravitationally bound. Stars orbit the center of the cluster, and the cluster orbits the center of our Galaxy. So far, about 140 globular clusters are known to exist in a roughly spherical halo around the Galactic center. Globular clusters do not appear spherically distributed as viewed from the Earth, and this fact was a key point in the determination that our Sun is not at the center of our Galaxy. Globular clusters are very old. There is a straightforward method of determining their age, and this nearly matches the 13.7 billion-year age of our entire universe.

M22
M22
(C) Doug Matthews/Adam Block/NOAO/AURA/NSF
M22 is a truly spectacular example of a star cluster since it is very near and, as we view it, toward the center of the galaxy. Thus, when M22 is observed we see hundreds of thousands of its constituents as well as a myriad of stars in the foreground and background. The ultimate of stars upon stars. M22 is estimated to be 10,000 light years away and around 65 light years across. This cluster can be seen easily in binoculars near the star atop the "teapot" asterism of Sagittarius.

Globular Cluster M22
Globular Cluster M22
(C) Nigel A.Sharp, REU program/AURA/NOAO/NSF
Piercing the heart of a glittering swarm of stars, NASA's sharp-eyed Hubble Space Telescope unveils the central region of the globular cluster M22, a 12- to 14-billion-year-old grouping of stars in the constellation Sagittarius. The telescope's view of the cluster's core measures 3.3 light-years across.

The stars near the cluster's core are 100,000 times more numerous than those in the Sun's neighborhood. Buried in the glow of starlight are about six "mystery objects," which astronomers estimate are no larger than one quarter the mass of the giant planet Jupiter, the solar system's heftiest planet.

The mystery objects are too far and dim for Hubble to see directly. Instead, the orbiting observatory detected these unseen celestial bodies by looking for their gravitational effects on the light from far distant stars. In this case, the stars are far beyond the cluster in the galactic bulge, about 30,000 light-years from Earth at the center of the Milky Way Galaxy. M22 is 8,500 light-years away. The invisible objects betrayed their presence by bending the starlight gravitationally and amplifying it, a phenomenon known as microlensing.

M22, NGC6656 M22
M22, NGC6656
(C) NOAO
Globular Cluster M22
(C) CFHT
M22
M22
(C) NOAO
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