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Saturday, April 25, 2015

EarthSky: Mira the Wonderful, a famous variable star

EarthSky Communications

Friday, Oct. 23, 2009

Today’s chart looks southeast on October evenings. That’s where you’ll find the constellation Cetus the Whale.

Menkar is the brightest star in Cetus. It’s located about 220 light-years away. Menkar resides in the Head of the Whale, which is shaped like a lopsided pentagon and which is generally the easiest part of Cetus to identify.

Deneb Kaitos is in the Tail of the Whale. When you see the word “deneb” in star names, it nearly always means “tail.”

You might not see the other star marked on today’s chart with the eye alone. It’s a variable star, Omicron Ceti, whose proper name is Mira. Mira is one of the most famous of all variable stars. The brightness of this star varies over a period of about 11 months. Long ago, early stargazers must have looked at the pattern of stars we know as Cetus and noted the location of a star that was sometimes visible … and sometimes not. That’s probably how Mira came to be called “The Wonderful.”

Is Mira the Wonderful visible now? Perhaps. It reached its peak brightness in late December 2008 and another brightness maximum is predicted for late November 2009. Although this star’s variable character is not altogether predictable, it is usually bright enough to see with the unaided eye for a month or so before and after its peak brightness. Come to know the constellation Cetus now, and watch Mira in the months to come. One night, as this wonderful star steadily increases in brightness, you’ll see Mira pop into view!

By the way, Mira was discovered in mid-2007 to have an amazing comet-like tail. This trail of blue cast across the heavens – discovered by astronomers using a space telescope – is actually hot gas thrown off by Mira.

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