Coma Berenices – Berenice's Hair

Coma Berenices – Berenice's Hair
You may not have heard of Coma Berenices. It's a small dim constellation that doesn't figure in the well-known mythological tales. Yet it isn't an insignificant area of sky. It contains our Galaxy's north pole, several Messier objects and thousands of galaxies.

History
Berenice was an Egyptian queen in the third century BCE, not a mythological figure. Soon after her marriage to Ptolemy III, the king went off to war. Berenice promised a goddess that she would sacrifice her beautiful long hair if her husband returned safely. Upon his return she made good her vow and placed her tresses in the temple.

But – oh no! – the offering disappeared overnight. What had happened? The simple answer is that we don't know, but there is a story. Hyginus (64 BCE-17 CE) told it in Poetic Astronomy, writing that astrologer Conon of Samos smoothed over the outrage. He told the king that his wife's sacrificed hair had not only been accepted by the goddess, but that she'd put it in the sky. Conon then pointed out a group of faint stars near Leo's tail.

To second-century astronomer Claudius Ptolemy (90-168 CE) the stars of Coma Berenices were an asterism in Leo, i.e., a recognizable grouping of stars that don't form a constellation. However that changed in the 16th century when it was shown as a constellation on celestial globes, and then listed as such by the Danish astronomer Tycho Brahe (1546-1601) in his atlas. In modern times the International Astronomical Union (IAU) chose it as one of the 88 official constellations.

The Galactic North Pole
In an edge-on view of the Milky Way you can see it's disk-shaped with a bulge in the center. When we look up at the constellation Sagittarius, we're looking towards the center of the Galaxy. There are not only 28,000 light years worth of stars and nebulae between us and the Center, but also quite a lot of obscuring dust. However when we look up at Coma Berenices, we're looking out of the plane of the Galaxy towards the Galactic North Pole. Imagine it as sticking up out of the Galactic Center where there aren't so many stars.

Stars
There aren't any bright stars in Coma Berenices. The three brightest ones are similar to the Sun, only seeming dim because of their distance. Beta Comae Berenices is 30 light years away. And although Alpha Comae Berenices is a binary composed of two sunlike stars, it's 65 light years from us and appears dimmer than Beta. It's also called Diadem and represents the jewel in Berenice's crown.

Clusters
Messier 53 (M53) is a globular cluster. Globular clusters are large star clusters whose gravity pulls them together into spherical form. They are found in the halo of the Galaxy, which is a large sphere of ancient stars and clusters orbiting the Galactic Center. M53 is one of the more distant globular clusters – it's 60,000 light years from the Galactic Center.

There are open clusters of various ages, but none as old as the globular clusters. They contain fewer stars and are more diffuse than the globular clusters. The Coma Berenices open star cluster has about fifty stars, but since it's only 288 light years away, it fills a large area of sky.

Galaxy clusters
Coma Berenices has galaxies galore. In the Coma Galaxy Cluster alone are over a thousand identified galaxies. The top ten of the brightest galaxies can be seen in larger amateur telescopes, but the rest are visible only in big telescopes. There could be 30,000 smaller galaxies, but even using big telescopes, astronomers can't say how many. The cluster isn't full of gorgeous spirals, but is dominated by elliptical galaxies varying in size from dwarfs to supergiants.

More Galaxies
One of my favorites is NGC 4676 whose nickname is the Mice Galaxies. This pair is about 300 million light-years from Earth. They began as spiral galaxies, but around 290 million years ago they began interacting. During one close approach gravitational effects triggered a lot of star formation, and pulled out long strands of material that look a bit like mouse tails.

The Needle Galaxy (NGC 4565) is around 30 million light years away, and right above the Galactic North Pole. Eighteenth-century astronomer William Herschel discovered it, seeing it only as a fuzzy cloud. We now recognize it as a spiral galaxy seen edge-on.

A much more spectacular spiral galaxy than NGC 4565 is M100. Its prominent and well-defined spiral arms make it a grand design spiral, one of the biggest and brightest jewels of the Virgo Cluster. It's also a starburst galaxy, a galaxy that shows very strong star formation.

An unusual galaxy is M64 which has various nicknames, one of them being the Black Eye Galaxy. It has two concentric disks of equal mass that are rotating in opposite directions. There is some star formation where the disks are in contact. The composite galaxy may have resulted when two galaxies collided and merged long ago.



You Should Also Read:
Milky Way – Our Galaxy
Galaxy or Star Cluster
What Is a Galaxy

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