Researchers find fast-moving gas flowing away from star

A unique stage of planetary system evolution has been imaged by astronomers, showing fast-moving carbon monoxide gas flowing away from a star system over 400 light years away.
They have detected fast-moving carbon monoxide gas flowing away from a young, low-mass star: a unique stage of planetary system evolution which may provide an insight into how our own solar system evolved.
It suggests that the way systems develop may be more complicated than previously thought.
“Although it remains unclear how the gas is being ejected so fast, we believe it may be produced from icy comets being vaporised in the star’s asteroid belt,” said study authors from the University of Cambridge in the UK.
The detection was made with the Atacama Large Millimetre/submillimetre Array (ALMA) in Chile, as part of a survey of young ‘class III’ stars, reported in an earlier paper.
Some of these class III stars are surrounded by debris discs, which are believed to be formed by the ongoing collisions of comets, asteroids and other solid objects, known as planetesimals, in the outer reaches of recently formed planetary systems.
The leftover dust and debris from these collisions absorbs light from their central stars and re-radiate that energy as a faint glow that can be studied with ALMA.
In the inner regions of planetary systems, the processes of planet formation are expected to result in the loss of all the hottest dust, and class IIII stars are those that are left with – at most – dim, cold dust.
These faint belts of cold dust are similar to the known debris discs seen around other stars, similar to the Kuiper belt in our own solar system, which is known to host much larger asteroids and comets.
In the survey, the star in question, ‘NO Lup’, which is about 70 per cent the mass of our sun, was found to have a faint, low-mass dusty disc, but it was the only class III star where carbon monoxide gas was detected, a first for this type of young star with ALMA.
While it is known that many young stars still host the gas-rich planet-forming discs they are born with, NO Lup is more evolved, and might have been expected to have lost this primordial gas after its planets had formed.
While the detection of carbon monoxide gas is rare, what made the observation unique was the scale and speed of the gas, which prompted a follow-up study to explore its motion and origins.
“Just detecting carbon monoxide gas was exciting, since no other young stars of this type had been previously imaged by ALMA,” said first author Joshua Lovell.
“But when we looked closer, we found something even more unusual: given how far away the gas was from the star, it was moving much faster than expected. This had us puzzled for quite some time,” Lovell added.
Further analysis also showed that the gas may be produced during collisions between asteroids, or during periods of sublimation – the transition from a solid to a gaseous phase – on the surface of the star’s comets, expected to be rich in carbon monoxide ice.
The results was scheduled to be presented at the ‘Five Years After HLTau’ virtual conference in December. (IANS)

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