Rarae Aves II
Many of the pinpoints of light that decorate the night sky are staging their own versions of “Dancing with the Stars” — with real stars. Pairs of stars whirl around each other in a tight gravitational embrace — an embrace that may get tighter as the dance goes on.
An example is a star system known as Zeta Phoenicis. It’s in the southern constellation Phoenix, which is named for the mythological bird that was reborn from its own ashes. Phoenix just peeks above the southern horizon this evening from most of the United States.
Zeta Phoenicis consists of at least three stars, two of which form a tight pair — they’re separated by only a few times the diameter of the stars themselves. At such close range, they orbit each other once every 40 hours.
Both stars are a good bit bigger, brighter, and heavier than the Sun, so they’re an impressive pair.
But one of them is a bit more impressive — it’s about half-again as massive as its partner. That means it will exhaust the hydrogen fuel in its core more quickly. As it does so, it’ll puff up to many times its current size. Its outer layers will engulf its smaller companion, which will “steal” some of the larger star’s gas. Over time, it may add so much gas that it’ll speed up its own evolution — and its own demise.
Eventually, both stars will lose their outer layers of gas, leaving only their small, dense cores — a pair of white dwarfs dancing gracefully into the long cosmic night.
Script by Damond Benningfield, Copyright 2011
For more skywatching tips, astronomy news, and much more, read StarDate magazine.