A most superb deep-sky treasure hides in plain sight within the spring sky — the Coma star cluster (Melotte 111), which Ptolemy cataloged as a “nebula” round A.D. 138. This spangle of seven outstanding naked-eye suns (and twice as many which can be fainter) type essentially the most outstanding a part of the constellation Coma Berenices, Berenice’s Hair.
In contrast to most open star clusters, which hug the Milky Way’s spiral arms, we see the Coma Star Cluster solely about 5° west of the North Galactic Pole — the purpose on the celestial sphere’s northern half at which our galaxy’s axis of rotation is aimed. Shining at magnitude 1.8 and spanning 5° of sky, the Coma star cluster is likely one of the largest and brightest open star clusters within the sky. At a distance of 288 light-years, additionally it is one of many nearest. The 400- to 600-million-year-old cluster comprises some 270 members starting from magnitude 5 to 10.5. The cluster’s total mass is probably going lower than 100 solar plenty, and its density is about one star per 33 cubic light-years.
Its members type a roughly triangular sample within the sky that spans 22.5 light-years of space. Via binoculars, greater than 100 stars might be seen on this wedge-shaped portion fashioned by 12, 14, and 17 Comae Berenices. The cluster comprises no fully-evolved big stars.
Ten fairly vibrant galaxies are inside attain of a 4-inch telescope below a darkish sky. All of them lie inside 2° of the Coma star cluster: NGC 4225, 4251, 4274, 4278, 4283, 4314, 4448, 4494, 4559, and 4565. These all belong to the nice Coma Cluster of galaxies, a turbulent array of hundreds of galaxies (largely ellipticals and lenticulars) greater than 300 million light-years distant. It’s the nearest large cluster of galaxies and is scattered throughout greater than 20 million light-years of space.
When you’ve completed inspecting the Coma star cluster with binoculars and a telescope, research it along with your unaided eyes to see what number of dim stars you may detect. The cluster comprises 9 stars between magnitude 6.0 and seven.4, with separations starting from 12″ to 31″.
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