In a new paper accepted in the Monthly Notices of the Royal Astronomical Society with lead author Joshua Lovell, researchers detail the observations of fast-moving carbon monoxide gas flowing away from a young, low-mass star.

Per the press release: 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-radiates that energy as a faint glow that can be studied with ALMA.

The star, NO Lup, is a class-III star and about 70% the size of our Sun. These types of stars are expected to only have cold, dim dust left by this point in their evolution as the biggest gas giants have formed, and all that should remain is the equivalent of our own Kuiper Belt and Oort Cloud. NO Lup is the first class-III star observed to have carbon monoxide, and even more intriguing is the speed and scale of the ejection.

Grant Kennedy, who led the modelling work, explains: We found a simple way to explain it: by modelling a gas ring but giving the gas an extra kick outward. Other models have been used to explain young discs with similar mechanisms, but this disc is more like a debris disc where we haven’t witnessed winds before. Our model showed the gas is entirely consistent with a scenario in which it’s being launched out of the system at around 22 kilometers per second, which is much higher than any stable orbital speed.

Some of the gas may even come from the collision of asteroids or sublimation of their various ices. The release goes on to note: There has been recent evidence of this same process in our own solar system from NASA’s New Horizons mission when it observed the Kuiper Belt object [Arrokoth] in 2019 and found sublimation evolution on the surface of the comet, which happened around 4.5 billion years ago.

We may be witnessing the destruction of comets in a system 400 light-years away. As co-author Mark Wyatt said: While we have seen gas produced by planetesimals in older systems, the shear rate at which gas is being produced in this system and its outflowing nature are quite remarkable and point to a phase of planetary system evolution that we are witnessing here for the first time.

This observation only lasted thirty minutes. Imagine how much more they could learn with more observing time. And now we add even more pieces to the planetary system formation puzzle.

More Information

The University of Cambridge press release 

“Rapid CO Gas Dispersal from NO Lup’s Class III Circumstellar Disc,” J. B. Lovell et al., to be presented at Five Years After HL Tau, 7-11 December 2020.

“ALMA Survey of Lupus Class III Stars: Early Planetesimal Formation and Rapid Disc Dispersal,” J. B. Lovell et al., 2020 Oct. 28, Monthly Notices of the Royal Astronomical Society (preprint on arxiv.org)