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October 6, 2012

The celestial water bearer pours a streamer of faint stars across the southern sky on October nights. Aquarius is low in the southeast as the sky gets good and dark, and stands due south before midnight.

The constellation was important to the cultures of the ancient Middle East. In Babylon, it represented the god Ea, who ruled the Sun’s path for a quarter of the year. And in Egypt, it represented the god of the Nile because it was associated with the river’s annual life-giving floods — the floods came when the water bearer dipped his jug into the Nile.

Aquarius’s brightest star is Sadalsuud — an Arabic name that translates as “best luck” or “luckiest of the lucky.” The name is related to the rains that accompanied it in the spring, when it first appeared in the morning sky.

Sadalsuud is many times bigger and heavier than the Sun, and more than 2,000 times brighter. When it was born it was smaller but much hotter than it is today. But it’s nearing the end of its life, so changes in its core have caused its outer layers to puff up like a balloon. As it puffed up its surface got cooler. But the surface also got a lot bigger, making the star much brighter.

We’ll talk about another star system in Aquarius tomorrow.

In the meantime, look for Aquarius in the southeast in early evening. Sadalsuud is at its top right corner. It stands high above Fomalhaut, the brightest star in that part of the sky, which can help you pick it out.


Script by Damond Benningfield, Copyright 2012

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