Moon and Antares
If you tried to fly a spaceship into the outer layers of the Sun, it would be a quick trip. The Sun's heat would quickly roast you and anything else inside the ship, then melt the ship itself. But the outer layers of some stars are so cool and puffed up that you just might be able to skim into them and live to tell about it.
An example is Antares, the "heart" of Scorpius, the scorpion. It's the bright orange star just to the right of the Moon this evening.
Antares is classified as a red supergiant. It's about a dozen times as massive as the Sun. If it took the Sun's place, it would swallow the four innermost planets -- including Earth.
A star that big and bloated is pretty fluffy. On average, the air at Earth's surface is about 25,000 times denser than the gas that makes up Antares. But much of the star's mass is concentrated in its hot, dense core, so its outermost layers are much thinner than average -- a near-vacuum by Earthly standards. These layers are relatively cool, too.
That means a properly shielded spacecraft might dip into the outer layers of Antares and come back out again. It would take advanced technology to carry off such a mission, but technology that's within the realm of possibility.
So astronomers of the far-distant future may study Antares and similar stars not just from hundreds of light-years away -- but from the inside.
Watch Antares this evening as it precedes the Moon across the southwestern sky.
Script by Damond Benningfield, Copyright 2002, 2005, 2009
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