M6
Butterfly Cluster
物性
位置と識別子
可視性
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M6について
説明
The Butterfly Cluster is a bright open cluster in Scorpius, about 1,600 light-years from Earth. It contains around 80-120 stars spread across about 12 light-years, with an age of roughly 100 million years. The cluster's brightest member is the orange giant BM Scorpii, a semiregular variable star whose color contrasts beautifully with the blue-white stars around it.
観測のコツ
Located about 5 degrees north of the Scorpion's stinger (Lambda Scorpii). Easily visible to the naked eye as a hazy patch. Binoculars reveal a beautiful butterfly-shaped pattern of stars. A telescope at low power (30-50x) provides the best view, showing the full extent of the cluster with the butterfly outline clearly visible. Look for the contrasting orange color of BM Scorpii among the blue-white members. Best observed from June through August.
歴史
Possibly observed by Ptolemy around 130 AD as a nebulous patch near the Scorpion's stinger. Giovanni Battista Hodierna recorded it before 1654. Charles Messier cataloged it in 1764, noting a cluster of small stars.
豆知識
The orange giant BM Scorpii is a semiregular variable star that changes brightness between magnitude 5.5 and 7.0 over roughly 850 days. Its warm orange hue among the hot blue-white cluster stars makes a striking visual contrast — a beautiful example of stellar evolution in action.
コミュニティ写真 (1)
Credit: Giuseppe Donatiello from Oria (Brindisi), Italy. License: CC0. (Wikimedia Commons)
Skybred Feb 28, 2026