StarDate: November 24, 2009

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A faint, skinny triangle climbs the sky this evening -- the constellation Triangulum. It's about halfway up the eastern sky at nightfall, and climbs higher as the night progresses.

Individually, the triangle's stars aren't all that impressive. But together, they form a distinctive pattern.

Triangulum was first drawn thousands of years ago. Unlike most constellations from that era, though, there's not much skylore associated with it -- no tales of monsters or heroes to liven it up. Instead, people took it a bit more literally. They saw the triangle's stars as a celestial representation of triangles on Earth -- the Nile River delta, for example, or the island of Sicily.

Its brightest star is known as Beta Trianguli. It's at the base of the triangle, which is to the north in early evening.

Beta Trianguli is actually a binary -- two stars that are bound to each other by their mutual gravity.

The brighter of the two is more than twice as massive as the Sun, and dozens of times brighter. It appears to be nearing the end of its life on the "main sequence" -- the time when it burns through the hydrogen atoms in its core to make helium. When that phase ends, it'll begin burning the helium to make even heavier elements. As that happens, its outer layers will puff up, so the star will become far larger than it is now -- and give the triangle a truly impressive corner.

We'll talk about Triangulum's second-brightest star tomorrow.

Script by Damond Benningfield, Copyright 2009

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