Astronomers Just Spotted a Water Snow Line Around a Star for the First Time

Artist’s conception of a water snow line around a young star (Image: A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO))
Artist’s conception of a water snow line around a young star (Image: A. Angelich (NRAO/AUI/NSF)/ALMA (ESO/NAOJ/NRAO))

A telescope just snagged the very first image of a water snow line drifting around a young star in space—and it could transform what we know about how planets form.

The extreme conditions around young stars sometimes means that water goes directly from gas into snow and ice, skipping the liquid phase entirely. The region right where that transition happens is called the water snow line. This water snow line was only visible because the star in question, V883 Orionis, had a massive flare that pushed the water snow line around its protoplanetary disk, where planets are formed, outwards. This made it visible to Atacama Large Millimeter/submillimeter Array (ALMA) which took this view:

It’s not just a cool thing to see, though. It also has some implications for how planets form. Researchers at ESO say they suspect that the location of a forming-planet within the water snow line shows up in the planet’s eventual form. If a forming planet is on the inside of the water snow line, where water shows up as gas, the resulting planet is rocky like Earth. Planets forming on the outside of the water snow line, where the water shows up as ice, eventually form into gas giants like Jupiter.


Now that they’ve gotten a good look at a water snow line in action, they hope to be able to explain even more about the role it plays in planetary evolution.

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