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Chameleon Star

July 6, 2014

Stars live so long that they change little during our own much shorter lifetimes. For example, the Sun will eventually turn from yellow to orange and then red, but it’s a process that will play out over billions of years. Even so, a few rare stars have changed color in recent years. One is in Aquila, the eagle, which is in the eastern sky this evening.

V1302 Aquilae is roughly 16,000 light-years from Earth, and it’s one of the most powerful stars in the galaxy. In the 1970s, it shined yellow-white. A star’s color indicates its surface temperature: the hottest stars are blue and the coolest are red; our yellow Sun is in between. When V1302 Aquilae was yellow-white, it was about the same temperature as the Sun.

Since then, though, the star has heated up, so its color has changed from yellow-white to white. And astronomers suspect it was recently shining as a red star. The star is so massive that it’s destined to explode, but no one knows when that will happen or what color it will be when it does so.

For that matter, no one knows what color the star will be even a decade from now. Will it continue to heat up and become blue, like the hottest stars? Or will it cool down, becoming yellow and then red again? No one knows, but astronomers are watching every move of this rare stellar chameleon.

As night falls, look for Aquila to the lower right of Cygnus, the swan, another celestial bird that soars through the summer Milky Way.


Script by Ken Croswell, Copyright 2014

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