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StarDate 4/17/2014: Moon And The Scorpion

by Damond Benningfield
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FROM THE UNIVERSITY OF TEXAS McDONALD OBSERVATORY, AS HEARD ON KCBS RADIO WEEKDAYS @ 9:52 A.M., 7:35 P.M. & 2:52 A.M.

STARDATE 4/17/2014:  The heart of the scorpion is doomed. Sometime within the next million years or so, the star Antares is likely to blow itself apart as a supernova. Only its tiny, dead core will remain — a neutron star.

That same fate awaits several other bright stars in Scorpius, including one that’s quite close to the Moon tonight. Acrab is to the right of the Moon as they climb into view after midnight, at the end of a short line of three stars that represents the scorpion’s head.

Acrab is actually a stellar sextuplet. It consists of two tight pairs of stars, each of which has a distant companion. The two triplets are then bound to each other as well, giving Acrab six stars in all.

Two of those stars appear to be at least 10 times as massive as the Sun. That’s above the weight limit that determines which stars will explode as supernovae. So within a few million years, the cores of each of these stars probably will collapse, and their outer layers will blast into space. For a few weeks, each explosion will shine as brightly as billions of normal stars. After that, the stars will fade from sight.

For now, though, Acrab remains in good view. Look for it just to the right of the Moon after midnight. Much brighter Antares, the orange star that marks the scorpion’s heart, stands below them. And an even brighter pinpoint of light — the golden planet Saturn — is farther to their upper right. The whole tableau is low in the southwest at first light.

Copyright ©2014 The University of Texas McDonald Observatory

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