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Monday, November 19, 2012

Comet collisions at 49 CETI

Early in their history, stars are surrounded by a cloud of dust and gas. Although the dust may persist, the gas is usually lost fairly quickly (within a few million years). That isn’t the case for the star 49 CETI, which still has an extremely gassy orbit some forty million years after its formation. Cosmologists were at a loss to explain why all that gas was still in orbit around the star. Recently, Benjamin Zuckerman from the University of California, Los Angeles and Inseok Song from the University of Georgia came up with the solution. It seems that the gas is constantly being replenished from comet collisions.

In our solar system, there’s a disk of space known as the Kuiper Belt that begins just past the orbit of Neptune. This region of space is home to at least 70,000 objects, including the dwarf planet Pluto. Astronomers say that the total mass of these objects, currently one tenth that of the Earth, was once 400 times larger. Remember that our solar system is over a hundred times older than 49 CETI. If 49 CETI has its own, much younger, version of the Kuiper Belt, that band of comets could be far larger than ours. This is exactly what Zuckerman and Inseok found.

In fact, according to the researchers, there are hundreds of trillions of comets circling 49 CETI, so many that two of them collide about every six seconds. This constant barrage releases a steady stream of carbon monoxide into the surrounding space—enough to keep the orbit of 49 CETI well supplied with gas.

Zuckerman, B., & Song, I. (2012). A 40 Myr OLD GASEOUS CIRCUMSTELLAR DISK AT 49 CETI: MASSIVE CO-RICH COMET CLOUDS AT YOUNG A-TYPE STARS The Astrophysical Journal, 758 (2) DOI: 10.1088/0004-637X/758/2/77