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The variable star Mira, the Owl Cluster (NGC 457), and the Little Spindle Galaxy (NGC 584)

November 14–21, 2013: The variable star Mira in Cetus is an excellent target for naked-eye and binocular observers, the Owl Cluster (NGC 457) in Cassiopeia offers small-telescope owners nice views, and large-telescope owners can seek out the Little Spindle Galaxy (NGC 584) in Cetus.
This week's small-telescope target, the Owl Cluster (NGC 457), lies 2° south-southwest of Delta (δ) Cassiopeiae.
Astronomy: Roen Kelly
Each week, Astronomy magazine Senior Editor Michael E. Bakich, a master at explaining how to observe, posts a podcast about three or more objects or events you can see in the sky.

Targets for November 14–21, 2013

Naked eye: Variable star Mira
Small telescope: The Owl Cluster (NGC 457)
Large telescope: The Little Spindle Galaxy (NGC 584)
A wonderful star
This week's naked-eye object is one of the sky's most famous variable stars — Mira in the constellation Cetus. Long ago, German celestial cartographer Johannes Bayer designated this star Omicron (ο) Ceti. But most observers know it by its common name.

The name Mira is Latin for "the Wonderful," and this luminary is the archetype for an important class of variable stars. It was, in fact, the first variable star discovered. German astronomer David Fabricius noted its changeable nature beginning in 1596. Mira-type variables have long periods and large-amplitude variations in brightness. Mira itself takes 332 days to vary between 2nd and 10th magnitude, but it does so irregularly.

In February 1997, Mira reached nearly 2nd magnitude, but at its next maximum at the beginning of 1998, the star disappointed observers by attaining only 4th magnitude. You can locate Mira slightly more than 7° southeast of magnitude 3.8 Al Rischa (Alpha [α] Piscium).

In 2007, astronomers studying ultraviolet images from the Galaxy Evolution Explorer (GALEX) satellite discovered another that Mira possesses an enormous comet-like tail nearly 13 light-years long. Mira is now a red giant star that is blowing its outer layers of material into interstellar space. NASA estimates the amount of material in Mira's tail equals 3,000 times Earth's mass.

This cluster's a hoot
This week's small telescope target is the Owl Cluster in Cassiopeia. This great open cluster is also known as the E.T. Cluster, the Psi Cassiopeiae Cluster, and NGC 457. It shines at magnitude 6.4 and measures 13' across. Sharp-eyed observers may spot this object from a dark site without optical aid, but a telescope will really make it pop.

Sir William Herschel discovered NGC 457 in 1787. Messier missed this cluster, although it outshines the two objects he did include from this constellation — magnitude 6.9 M52 and magnitude 7.4 M103.

While observing this cluster in 1977, Astronomy magazine Editor David J. Eicher saw an owl figure made of the two brightest stars and the cluster's overall shape. He dubbed it the Owl Cluster, and it's carried that name ever since. Five years later, Universal Pictures released the movie E.T.: The Extra-Terrestrial. Some observers saw a resemblance between the alien character in the film and NGC 457, and they subsequently dubbed it the E.T. Cluster.

As the Owl Cluster, NGC 457 is one of the sky's two celestial owls (the other is the Owl Nebula [M97]). Magnitude 5 Phi (φ) Cassiopeiae also lends its name to the cluster, but that star doesn't travel with it through space.

NGC 457 contains 25 stars brighter than 12th magnitude. Its most luminous star shines at magnitude 8.6. Under a dark sky, a 4-inch telescope at a magnification of 50x shows nearly 75 cluster stars. Note the uniform background glow caused by distant, unresolved Milky Way stars.

A small spindle in Cetus
This week's large telescope target is the Little Spindle Galaxy in Cetus, also known as NGC 584. You'll find it 2.2° northeast of magnitude 3.6 Theta (θ) Ceti. NGC 584 glows at magnitude 10.5 and measures 4.1' by 2'.

NGC 584 is a fat, lens-shaped elliptical galaxy that doesn't show much detail. Through an 8-inch telescope, you'll see the broad, bright core take up three-quarters of the galaxy's length. A bright halo lies outside the core, but it quickly fades to the black of space.

Only 4' east-southeast of NGC 584's core lies the magnitude 13.2 spiral galaxy NGC 586. Crank up the magnification past 200x to put some distance between the two objects before you observe the fainter galaxy.

Astronomy magazine Contributing Editor Stephen James O'Meara called NGC 584 the Little Spindle because of its resemblance to a similar object, the Spindle Galaxy (NGC 3115), which lies in Sextans.
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Check out's interactive StarDome to see an accurate map of your sky. This tool will help you locate this week's targets.

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Observing Talk
After you listen to the podcast and try to find the objects, be sure to share your observing experience with us by leaving a comment at the blog or in the Reader Forums.


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