Butterfly Cluster
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| Observation data (Epoch J2000.0) | |
|---|---|
| Class | II,3,m |
| Right ascension | 17h 40.1m |
| Declination | −32° 13′ |
| Distance | 1.6 kly (491 Pc) |
| Apparent magnitude (V) | 4.2 |
| Apparent dimensions (V) | 25′ |
| Physical characteristics | |
| Mass | ( M☉) |
| Radius | 6 light years |
| VHB | |
| Estimated age | |
| Notable features | |
| Other designations | Messier 6 |
The Butterfly Cluster (also known as Messier Object 6 or NGC 6405) is an open cluster in the constellation Scorpius. It was discovered by Giovanni Batista Hodierna before 1654 and catalogued by Charles Messier in 1764 as number 6 in his catalogue of comet-like objects.
Estimates of the cluster's distance have varied over the years with a mean value of around 1,600 light years, giving it a spatial dimension of some 12 light years. Most of the bright stars in this cluster are hot, blue B type stars but the brightest cluster member is a K type orange giant star. This star, known as BM Scorpii, is classed as a semiregular variable star, its brightness varying from magnitude +5.5 to magnitude +7.0. In color photographs of the Butterfly Cluster this orange star contrasts sharply with its blue neighbours in the cluster.
External links
fr:Amas du Papillon it:M6 ja:M6 nl:Vlindercluster sk:Motýlia hviezdokopa fi:Perhosjoukko sv:M6
