AP Columbae
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One of the stars of tonight’s sky is Orion, the brightest of all constellations. The hunter is low in the east at nightfall, with his “belt” of three stars pointing straight up from the horizon.
To the right of the belt, look for the hunter’s sword, which includes the fuzzy glow of the Orion Nebula — a giant cloud of gas and dust that’s given birth to thousands of stars. The nebula’s so far away, though, that it’s a bit tough to study its stars.
One other young star is much closer — just 27 light-years away. It’s in the constellation Columba, the dove, which is below Orion’s feet as the hunter climbs skyward.
AP Columbae is a red dwarf, which is much smaller, cooler, and fainter than the Sun. But it’s just 40 million years old — about one percent the age of the Sun. In fact, it’s so young that it hasn’t yet ignited its main supply of nuclear fuel. Instead, it generates light through gravity. As the star shrinks, it converts gravitational energy into heat, which makes the star glow.
The best evidence for the star’s youth comes from its high abundance of lithium. This lightweight element is quickly destroyed by nuclear reactions, so there’s little of it in mature stars like the Sun.
At a distance of just 27 light-years, AP Columbae is the closest infant star known. If it has planets, they should still be aglow from the heat of their birth. Because of their proximity, we might someday see these alien worlds, orbiting their young red sun.
Script by Ken Croswell, Copyright 2011
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