'Snow line' in distant solar system could be possible planet source

ANN ARBOR, Mich., July 18 (UPI) -- A snow line -- not on a mountain range but in a distant solar system -- has been directly imaged for the first time, U.S. astronomers say.

A snow line in a solar system is the point where falling temperatures freeze and clump together water or other chemical compounds that would otherwise be vapor, they said, and it's believed snow lines in space serve a vital role in forming planets because frozen moisture can help dust grains stick together.

Using the new Atacama Larger Millimeter/submillimeter Array telescope in Chile, scientists have captured radio-wavelength images of the carbon monoxide snow line around TW Hydrae, a young star 175 light-years away from Earth.

TW Hydrae is believed to be the closest infant, developing solar system to Earth.

"We've had evidence of snow lines in our own solar system, but now we're able to see one with our own eyes," University of Michigan astronomer Edwin Bergin said in a release Wednesday.

Different chemical compounds freeze at different distances from a central star; in our own solar system, water freezes in space between the orbits of Mars and Jupiter.

Different chemical compounds' snow lines may be linked to the formation of specific kinds of planets, the astronomers said; the carbon monoxide line in our system corresponds to the orbit of Neptune, where smaller icy bodies like comets and dwarf planets like Pluto would form.

"ALMA has given us the first real picture of a snow line around a young star, which is extremely exciting because of what it tells us about the very early period in the history of our own solar system," said study co-author Chunhua "Charlie" Qi, a researcher with the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

"We can now see previously hidden details about the frozen outer reaches of another solar system, one that has much in common with our own when it was less than 10 million years old."