物性
位置と識別子
可視性
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M22について
説明
The Great Sagittarius Cluster is one of the brightest globular clusters in the sky and one of the nearest, at about 10,600 light-years from Earth. It contains roughly 70,000 stars spanning about 99 light-years. M22 is one of only four globulars known to contain a planetary nebula (IRAS 18333-2357). It is the brightest globular visible from mid-northern latitudes after Omega Centauri and 47 Tucanae.
観測のコツ
Located about 2.5 degrees northeast of Lambda Sagittarii (Kaus Borealis), the top of the Teapot. Visible to the naked eye from dark sites. Binoculars show a large, bright fuzzy ball. Even a 3-inch telescope begins resolving individual stars. An 8-inch at 150x provides a stunning view with stars resolved across the entire cluster. Despite being brighter than M13, it sits low for northern observers and is often underappreciated. Best observed from June through September.
歴史
One of the first globular clusters discovered, possibly by Abraham Ihle in 1665. Charles Messier cataloged it in 1764. It was one of the first globulars to have individual stars resolved, by William Herschel in 1783.
豆知識
M22 was possibly the first globular cluster ever discovered (1665), predating M4 by 80 years. It is one of only four globulars known to contain a planetary nebula within it. Studies have also found two stellar-mass black holes in M22, confirmed through radio observations — making it a rare system with multiple known black holes.
コミュニティ写真 (1)
Credit: ESA/Hubble & NASA. License: CC BY 4.0. (Wikimedia Commons)
Skybred Feb 28, 2026