Image: Chi Cygni
ESO/L. Cal?ada
Chi Cygni, a red giant star as shown in this artist's conception, is nearing the end of its life. As it runs out of fuel, it pulses in and out, beating like a giant heart and ejecting shells of material.
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updated 1/19/2010 7:03:14 PM ET 2010-01-20T00:03:14

A preview of what's in store for our sun is in view across the galaxy, as a similar star balloons in its dying throes.

This sun twin, called Chi Cygni, lies about 550 light-years away from Earth. As it nears the end of its life, it has bloated in size and begun to pulse in and out like a giant beating heart. These are the telltale signs of a star running out of fuel after billions of years shining bright.

New close-up photos of this star are offering a sneak peek at our own sun's demise. The sun is now 4.6 billion years old.

"This work opens a window onto the fate of our sun five billion years from now, when it will near the end of its life," said astronomer Sylvestre Lacour of the Observatoire de Paris.

Chi Cygni is now in a phase of its life called the red giant stage where it has inflated so much that, were it in our solar system, it would engulf every planet out to Mars. And indeed, the sun will likely do just that one day when it is a red giant. At that point, the Earth will most likely be toast.

A particularly interesting feature captured by the new data is Chi Cygni's pulsations, which occur once every 408 days. As the star begins to run out of hydrogen fuel for fusion burning in its core, it cycles through stages of contracting and expanding, causing it to brighten and dim in the sky. These pulsations allow it to jettison its outer gaseous layers, which will eventually become a colorful planetary nebula.

At its smallest, Chi Cygni's diameter is 300 million miles (483 million km). At this stage it is at its hottest, with giant plumes of hot plasma churning on its surface. When it expands, the star cools and dims, reaching a maximum diameter of about 480 million miles (772 million km).

The new photos were captured with the Smithsonian Astrophysical Observatory's Infrared Optical Telescope Array (IOTA), at Whipple Observatory on Mount Hopkins, Ariz. This network of interconnected telescopes combines the light from several telescopes into one image, to yield a resolution equivalent to an observatory as large as the distance between them.

"IOTA offered unique capabilities," said researcher Marc Lacasse of the Harvard-Smithsonian Center for Astrophysics. "It allowed us to see details in the images which are about 15 times smaller than can be resolved in images from the Hubble Space Telescope."

The team published their findings in a recent issue of The Astrophysical Journal.

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