Beta Pegasi is a star in the constellation Pegasus. The apparent visual magnitude of this star averages 2.42, making it the second brightest star in the constellation after Epsilon Pegasi.
Based upon parallax measurements, Beta Pegasi is located about 196 light-years (60 parsecs) from the Earth. It is unusual among bright stars in having a relatively cool surface temperature compared to stars like the Sun. This star has a stellar classification of M2.3 II-III, which indicates the spectrum has characteristics partway between a bright giant and a giant star. It has expanded until it is some 95 times as large, and has a total luminosity of 1500 times that of the Sun. The effective temperature of the star’s outer envelope is about 3,700 K, giving the star the characteristic orange-red hue of an M-type star. The photosphere is sufficiently cool for molecules of titanium oxide to form.
Beta Pegasi is a semi-regular variable with a period of 43.3 day and a brightness that varies from magnitude +2.31 to +2.74. It is losing mass at a rate at or below 10–8 times the Sun’s mass per year, which is creating an expanding shell of gas and dust with a radius of about 3,500 times the Sun’s radius.
The star that marks the northwestern corner of the square is a red giant called Beta Pegasi (Scheat). It’s close to a hundred times the Sun’s diameter. If it took the Sun’s place in our own solar system, it would extend all the way to the orbit of Venus, the second planet out. And from the surface of the burned-out Earth, it would stretch half way across the sky.
Beta Pegasi shines about 350 times more brightly than the present-day Sun. But because it’s 200 light-years away, it looks like just another star.
Still, Beta Pegasi is one of the brightest red giants in the night sky. If you have a pair of binoculars, you might even be able to glimpse its red color. In that tiny red point of light, you’ll see the future of our own Sun.
19 Aug, 2013
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