More Moon and Antares
The Moon scrunches up close to the heart of the scorpion tonight -- the bright orange star Antares. They're low in the south at nightfall, with Antares a little to the left of the Moon.
One of the other wonders of Scorpius is just a few degrees to the east of Antares. But you can't see it -- at least not yet. It's a black cloud that may someday give birth to a new star.
The cloud is Barnard 68. It's named for American astronomer Edward Emerson Barnard, who cataloged it in 1919. It's about 300 to 400 light-years from Earth -- a bit closer than Antares.
The cloud consists mostly of hydrogen and helium, two gases that are, strangely enough, transparent. But about one percent of the cloud is made of dust, which blocks the light from the stars beyond it.
Barnard 68 is five light-months across. In other words, if the dust didn't absorb it, light would take five months to speed from one side of the cloud to the other. If you centered the cloud on the solar system, it would extend 12,000 times farther from the Sun than Earth's orbit.
Barnard 68 is frigid: 440 degrees below zero Fahrenheit -- colder than Pluto. At that temperature, its gas exerts little outward pressure. As a result, the inward pull of gravity may make the cloud collapse.
If that happens, the cloud will heat up. Its center will get so hot that it will begin to shine -- and a new star will take its place in the night.
Script by Ken Croswell, Copyright 2008
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
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