Dusty Impact
One of the night sky's indicators that summer's here is the appearance of the bright star Vega. As we head into the heart of summer, it's well up in the northeast at nightfall, and climbs almost directly overhead later on. This pure white star is one of the brightest in the night sky, so it's pretty easy to pick out.
Like many stars, Vega's encircled by a disk of gas and dust - the raw material for planets. No one's sure if Vega actually has planets. But they're pretty sure that at least one good-sized body orbited the star in the past. This body probably was pulverized in a collision with another object, adding a fresh supply of dust to the particles that already orbit Vega.
The orbiting Spitzer Space Telescope recently found evidence of the collision by measuring the infrared energy from the dust particles around Vega. Grains of dust glow brightly in the infrared, making the cloud stand out.
Spitzer found that the cloud is about 20 times bigger than our solar system. The particles in the outer regions are tiny. They're blown outward by a strong "wind" from Vega. This wind should clear out such small particles in a million years or less, so something must be supplying new particles.
That "something" could be collisions between bodies as big as Pluto. The most recent probably occurred within the last million years or so, adding fresh grains for Vega to sweep away.
We'll talk about another dusty collision tomorrow.
Script by Damond Benningfield, Copyright 2005
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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