Thursday, May 31, 2007

The constellation Coma Berenices (Berenice's Hair) is very much a minor constellation. It was originally considered to be a tuft of hair on the tail of Leo. This constellation is a little bit to the east of Denebola in Leo and is also a bit further towards the zenith from Virgo. It contains only one named star, alpha Comae Berenices, known as Diadem, representing the gem in Berenice's hair. This is a white main sequence star of apparent magnitude 4.3 and is about 43 light years distant. This is actually a binary star, and the pair are very close to each other, with an orbital period of 25.8 years.
The origins of the name of this constellation date to the time of Ptolemy III of Egypt (246-221 BCE). His wife was Berenice II, daughter of Magas, king of Cyrene. Ptolemy III continued the work of his father Ptolemy II in advancing the city of Alexandria and its famous library(later destroyed by Christian rioters). About 243 Ptolemy set out on a campaign against the Seleucids and his wife vowed to sacrifice her hair for the success of this expedition. When he returned victorious she cut off her hair and placed it in a temple of Aphrodite. The same night the hair disappeared, and through the offices of the court astrologer 'Conon' the laxity of the priests was "explained" by saying that the goddess was so pleased that she took the hair up into the heavens as a constellation. One for the clergy. Negative one for the aristocracy. Nobody ever said you had to be smart to be king.
Coma Berenices was mentioned in ancient sources, but the astronomer Ptolemy (no relation to the king) didn't refer to it as a constellation even though he called it a "lock" (of hair). The Greek Eratosthenes referred to it both as "Adriane's hair" and "Berenice's hair". The modern opinion of this as a separate constellation dates to Tycho Brahe who listed it as such in his catalogue of 1602.
While being quite dim and lacking brilliant stars this constellation is not without interest. When you look at Coma Berenices you are looking "north" across the galactic plane, perpendicular to the arms of the Milky Way. This means that you have a clear view of the regions beyond our own galaxy. On the border of Coma Berenices and Virgo their are numerous other galaxies visible in better telescopes . Some are visible to the amateur and are listed as Messier objects. There are actually eight Messier objects in this constellation, of which 7 are galaxies.
If you are a more advanced amateur astronomer than Molly is go to for a tour of the stars, galaxies, clusters and extra-solar planets so far discovered in Coma Berenices.

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