Moon and Antares
One of the biggest, brightest stars in our region of the galaxy precedes the Moon across the sky in the wee hours of tomorrow morning. They're in good view in the southeast by around 3 a.m., and are almost due south at first light. Antares is the bright orange star a little to the upper right of the Moon.
In astronomical parlance, Antares is a class M-1-I star.
The letter M indicates its spectral type -- basically, its color, which is a direct probe of its surface temperature. Astronomers use the letters O, B, A, F, G, K, and M to designate stars. "O" stars are the hottest, so they shine blue-white. "M" stars like Antares are the coolest, so they shine orange or red.
Astronomers split each letter class into 10 categories, with zero representing the hottest members of the class. Antares is actually classified as a 1.5, so it's a fairly hot M star.
The last character in the star's designation is the Roman numeral I. Class I is a supergiant -- a star that's far larger and more massive than the Sun. Antares is at least 15 times as massive as the Sun, for example, and if it took the Sun's place, it would extend out to the orbit of Mars. The "supergiant" designation also tells us something about the star's fate: A supergiant is destined to end its life with bang -- a titanic explosion called a supernova.
So enjoy the beauty of this big, bright star as it sticks close to the Moon tonight.
Script by Damond Benningfield, Copyright 2009
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