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Variable Stars


2-color closeup
Mira's Marvelous Tail — August 15, 2007
Mira, the closest and brightest of the red long-period variable stars, has thrown off a gassy hood and a comet-like tail so big that if you could see them, they would overflow your telescope's field of view.

The constellation Leo
Studying and recording the ups and downs of variable stars is a pleasant pastime that can also be scientifically rewarding. Here's a simple project to get you going.

Algol finder chart
Lurking in the seemingly changeless constellations are a few inconstant stars that pulse and eclipse. Here are a dozen variables that are easy to observe.

Stars charted
Why do larger numbers mean less light? Here's the story of astronomy's odd but beloved scheme for describing star brightnesses.

Now you can calculate the dates and times (local and Universal Times) when the eclipsing variable star Algol should be at its dimmest (magnitude 3.4 instead of its usual 2.1).

Beta Lyrae, an eclipsing binary, is one of the brightest and easiest-to-find variable stars in the sky.

Click for full chart
This red long-period variable is sometimes visible to the unaided eye — and sometimes invisible even in a 4-inch telescope.

Binary star artwork
Some of the Hipparcos satellite's unfinished business provides fair game for backyard observers.

T Pyx on April 15, 2011
T Pyxidis Finally Blows Again — April 15, 2011
A very overdue recurrent nova is having its long-awaited outburst. You can follow it with binoculars right after dark.

Citizen Sky Wants You! — September 11, 2009
Backyard astronomers of all types and experience levels can participate in a real-world science project — and help solve a mystery involving the star Epsilon Aurigae that's puzzled astronomers since 1821.

Robin Leadbeater of Wigton, UK, has reported the first sign of the long-awaited eclipse of Epsilon Aurigae, one of the most remarkable eclipsing variable stars in the sky.

RY Sgr with two dust clouds
Stars that Smoke — August 8, 2007
Astronomers have resolved carbon soot clouds around one of the sky's best-known R Coronae Borealis–type variable stars.

Scorpius closeup
A naked-eye nova erupted in the pre-dawn sky in early February and peaked at magnitude 3.8 on February 16th. As of the 27th it was still an easy binocular target at magnitude 5.4. And in the midst of the excitement, a second, fainter nova went off just below it.

Cygnus as photographed in infrared light on Sunday night, August 6, 2006. Chi Cygni (lower right of center) was the brightest star in the constellation at this wavelength, outshining even Deneb (top l
The red, Mira-type variable star Chi Cygni has had a very unusual maximum. It's one of the brightest such variables to begin with (typically peaking at about magnitude 5.2), but in late July and early August 2006, it peaked at about magnitude 3.8.

Finder chart
One is usually bright but fades unexpectedly; one is almost always faint but brightens unexpectedly. Check them out with binoculars.

Hipparcos satellite
The satellite caught tantalizing pieces of light curves for many new variable stars. Now it's time to fill in the details.



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