In a First, a “Snow-Line” Was Spotted Around a Young Star

July 14, 2016 | Gillian Burrell

Snow-line around a young star V883 Orionis
Photo credit: A. Angelich (NRAO/AUI/NSF). Artist’s impression of the water snowline around V883 Orionis.

All thanks to an outburst of energy from the star.

Astronomers observing a young star in the Orion Nebula Cluster were in for a surprise when a violent outburst of activity revealed the very first glimpse of a “snow-line.”

The researchers were using the Atacama Large Milimeter/submilimeter Array (ALMA) to observe the star V883 Orionis for evidence of disk fragmentation, which is one of the proposed ways that giant planets form. What they instead witnessed was a snow-line — the point at which water or another volatile substance is far enough from the star that it can condense and freeze into ice.

As reported in Nature, this is a significant finding because ice is necessary for the formation of ice giants like Uranus and Neptune and the cores of gas giants like Jupiter.

SEE ALSO: Our Sun May Have Devoured a Young Super-Earth During the Solar System’s Formation

Astronomers believe that gases and dust particles orbiting a young star like V883 Orionis in a “protoplanetary disk” will eventually snowball into planets and comets. Whether the water in the disk is frozen or not determines what kind of planets will form.

Usually, the snow-line is too close to the star for astronomers to observe the boundary from Earth, but a quick burst of light from V883 Orionis heated its protoplanetary disk, pushing the snow-line out to a distance of 40 astronomical units or 40 times the distance from Earth to the sun.

ALMA image of V883 Orionis with a snow-line

ALMA image of V883 Orionis. The dark ring is the snow-line. Credit: L. Cieza et al.; ALMA (ESO/NAOJ/NRAO)

The “violent outburst” that shifted the snow-line was likely caused by material from the disk falling into the star. Outbursts are thought to occur in most planetary systems, although this is the first time it has been observed.

According to Zhaohuan Zhu, an astronomer at Princeton University and co-author of the paper, the movement of snow-lines is important because they affect how and when planets will form.

“Since water ice is more abundant than dust itself beyond the snowline, planets can aggregate more solid material and form bigger and faster there. In this way, giant planets like Jupiter and Saturn can form before the protoplanetary disk is gone,” Jhu commented in a press release.

What we learned from ALMA’s observations of V883 Orionis could also improve our understanding of how frozen water was distributed when our own solar system was young.

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