Lucky Stars

StarDate: October 22, 2009

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If you've ever wanted to thank your lucky stars, this is a good time to try. The constellation Aquarius sails across the southern sky on autumn evenings, and several of its stars have names that signify luck or good fortune.

The most prominent examples are the constellation's two brightest stars. Their proper names are Sadalmelik and Sadalsuud. The names are from ancient Arabic, and mean "lucky one of the king" and "luckiest of the lucky."

The names may refer to the stars' positions. Back when the constellations were named, the Sun passed through this region of the sky in early spring, when the long nights of winter had passed and the new season brought gentle, life-giving rains. In fact, Aquarius is one of several "watery" constellations in that part of the sky.

As luck would have it, both of the stars are members of a rare class of stars known as yellow supergiants. Supergiants of any kind are rare enough. But most supergiants are either hot and blue or cool and red. Yellow ones are the rarest of all.

Sadalmelik is the larger and brighter of the pair. It's a few dozen times the diameter of the Sun, and several thousand times brighter. It's 600 light-years away.

These "lucky stars" -- both moderately bright -- are in the southeast at nightfall, and pass fairly high across the south later on. We'll have more about them tomorrow.

Script by Damond Benningfield, Copyright 2006, 2009

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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