First-ever sighting of water ‘snow line’ around star

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) facility in Chile have reported the first-ever sighting of water snow line around a young star.

A violent outburst by the young star V883 Orionis has given astronomers their first view of a water “snowline” in a protoplanetary disk – the transition point around the star where the temperature and pressure are low enough for water ice to form.

A dramatic increase in its brightness has pushed the water snow line out to a distance of around six billion km or roughly the size of the orbit of the dwarf planet Pluto.

The sudden brightening that V883 Orionis experienced is an example of what occurs when large amounts of material from the disc surrounding a young star fall onto its surface.

V883 Orionis is only 30 per cent more massive than the Sun but thanks to the outburst it is experiencing, it is currently a staggering 400 times more luminous.

“The ALMA observations came as a surprise to us. Our observations were designed to look for disc fragmentation leading to planet formation. We saw none of that. This illustrates well the transformational power of ALMA, which delivers exciting results even if they are not the ones we were looking for,” said lead author Lucas Cieza, astronomer at Diego Portales University, Santiago, Chile.

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