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 distinguished naked-eye suns (and twice as many which can be fainter) type essentially the most distinguished a part of the constellation Coma Berenices, Berenice’s Hair.
Not like 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 among the largest and brightest open star clusters within the sky. At a distance of 288 light-years, it is usually one of many nearest. The 400- to 600-million-year-old cluster incorporates 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. By binoculars, greater than 100 stars will be seen on this wedge-shaped portion shaped by 12, 14, and 17 Comae Berenices. The cluster incorporates no fully-evolved large stars.
Ten moderately vibrant galaxies are inside attain of a 4-inch telescope beneath 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 (principally ellipticals and lenticulars) greater than 300 million light-years distant. It’s the nearest huge 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, examine it together with your unaided eyes to see what number of dim stars you may detect. The cluster incorporates 9 stars between magnitude 6.0 and seven.4, with separations starting from 12″ to 31″.
Be sure to discover Astronomy’s full list of 101 cosmic objects you must see. New entries can be added every week all through 2022.
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