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Butterfly Cluster

M6, NGC 6405

Proper NamesButterfly Cluster
Messier NumberM6
NGC/IC NumberNGC 6405
ConstellationScorpius
Right Ascension17h 40m 20s
Declination-32° 15' 12"
Distancec.15,900 light years
c.4,900 parsecs
MagnitudeApparent: +4.2
Absolute: -4.3
DiameterApparent: 20'
Actual: 9 light years
Number of Starsc. 120
Optimum VisibilityJune / July
NotesThis rich and bright open cluster lies northward of the Fishhook of Scorpius' tail, alongside another bright cluster, Ptolemy's Cluster or M7. M6's arrangement of stars gives a vague impression of a butterfly with outstretched wings, an impression reinforced by two distinct streams of stars that can be seen as the northward-pointing antennae of the butterfly.

An open star cluster that lies in the heart of the Milky Way as it passes through the southern parts of Scorpius. M6 is bright enough to be seen by the naked eye, and lies a little to the north of its more prominent neighbouring cluster, M7 or Ptolemy's Cluster.

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