TheButterfly Cluster (cataloged asMessier 6 orM6, and asNGC 6405) is anopen cluster ofstars in the southernconstellation ofScorpius. Its name derives from the resemblance of its shape to abutterfly.[5]
Estimates of the Butterfly Cluster's distance have varied over the years.[8] Wu et al. (2009) found a distance estimate of 1,590light-years,[1] giving it a spatial dimension of some 12 light years.[3] Modern measurements show its total visual brightness to be magnitude 4.2. The cluster is estimated to be 94.2[1] million years old. Cluster members show a slightly higher abundance of elements heavier than helium compared to the Sun;[9] what astronomers refer to as themetallicity.
The cluster is located 24.59 ± 0.13 kly (7.54 ± 0.04 kpc)[9] from theGalactic Center and is following an orbit through theMilky Way galaxy with a loweccentricity of 0.03 and anorbital period of 204.2 Myr. At present it is 23 ly (7 pc) below thegalactic plane, and it will cross the plane every 29.4 Myr.[1]
^abFrommert, Hartmut; Kronberg, Christine (August 21, 2007),"Messier 6",SEDS Messier pages, Students for the Exploration and Development of Space (SEDS), retrieved2018-12-07.
