Astronomers Using ALMA Image Snow Line in Infant Star System

Posted on July 28, 2013

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have taken the first ever image of the snow line in an infant planetary system. The ALMA image of the carbon monoxide snow line in the disc around the Sun-like star TW Hydrae is pictured above. An artist's impression of snow lines around TW Hydrae is pictured below.

On Earth, snow lines are clearly visible on a mountain. The snow lines around young stars form in a similar way, in the distant, colder reaches of the dusty discs from which planetary systems form. Water is the first to freeze and forms the first snow line. Further out from the star, where temperatures are even colder, more exotic molecules can freeze and turn to snow, including carbon dioxide, methane and carbon monoxide. Astronomers say each of these different snow lines may be linked to the formation of particular kinds of planets.

The snow line spotted by ALMA is the first glimpse of the carbon monoxide snow line, around TW Hydrae, a young star 175 light-years away from Earth. Astronomers believe this budding planetary system shares many of the same characteristics of the Solar System when it was just a few million years old.

Chunhua "Charlie" Qi, Harvard-Smithsonian Center for Astrophysics, one of the two lead authors of the paper, said in a release, "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 the Solar System. We can now see previously hidden details about the frozen outer reaches of another planetary system similar to our own."

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