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Moon and Companions

StarDate: 
May 5, 2015

Antares is like a stellar iceberg — there’s much more to it than meets the eye. The “hidden” part of the star highlights the need for a variety of astronomical instruments.

Antares forms part of a brilliant triangle tonight. The orange star is close to the lower right of the Moon as they climb into good view in late evening. And the slightly brighter planet Saturn is about the same distance to the upper right of the Moon.

Antares is a supergiant — a star that’s much bigger and heavier than the Sun. It’s so big, in fact, that if it took the Sun’s place in our own solar system, it would easily engulf Earth and the other three innermost planets.

Not surprisingly, such a mammoth star shines brilliantly. At visible wavelengths, in fact, Antares is about 10,000 times brighter than the Sun. But its surface is much cooler than the surface of the Sun. At the lower temperature, it emits most of its light at infrared wavelengths, which are invisible to the human eye. When you add the infrared, the star’s total luminosity is about 60,000 times greater than the Sun’s.

So to fully understand Antares, astronomers must study it with instruments that are sensitive to the infrared. Earth’s atmosphere absorbs most infrared energy, so those instruments need to be placed above as much of the air as possible — on high mountaintops, or in airplanes or satellites. Without them, much of this gigantic star remains hidden from sight.

 

Script by Damond Benningfield, Copyright 2015

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