
A sprinkling of faint stars stands in the east a few hours after sunset right now. It’s to the upper right of brilliant Arcturus, the brightest star in that part of the sky. Those ribbons of stars are the main features of Coma Berenices.
The constellation represents Queen Berenice II of Egypt. The legend says that when her husband was about to head into battle, she offered her beautiful golden hair to the gods in exchange for his safety. When he returned undamaged, she cut her hair and placed it in a temple. Legend says the gods then placed it in the stars.
The brightest of those stars, Beta Coma, looks a lot like the Sun. It’s about the same size, mass, and brightness. It’s also about the same color — fittingly enough, bright gold, which shows up in binoculars or a telescope.
Long-term observations reveal that Beta Coma produces a 16-and-a-half-year magnetic cycle — half again the length of the solar cycle. During that cycle, the star probably goes through periods of high and low magnetic activity. During active times, more of the dark storms known as “starspots” probably speckle its surface — the result of lines of magnetic force getting twisted and stretched. When they snap, they produce powerful outbursts known as flares — eruptions that are equal to millions or billions of nuclear bombs.
Coma’s real claim to fame isn’t its stars, though — it’s a cluster of galaxies. We’ll have more about that tomorrow.