Carbon monoxide gas produced by a giant impact in the inner region of a young system

Abstract

Models of terrestrial planet formation predict that the final stages of planetary assembly, lasting tens of millions of years beyond the dispersal of young protoplanetary disks, are dominated by planetary collisions. It is through these giant impacts that planets like the young Earth grow to their final mass and achieve long-term stable orbital configurations. A key prediction is that these impacts produce debris. To date, the most compelling observational evidence for post-impact debris comes from the planetary system around the nearby 23 Myr-old A star HD 172555. This system shows large amounts of fine dust with an unusually steep size distribution and atypical dust composition, previously attributed to either a hypervelocity impact or a massive asteroid belt. Here, we report the spectrally resolved detection of a CO gas ring co-orbiting with dusty debris between ~6-9 au - a region analogous to the outer terrestrial planet region of our Solar System. Taken together, the dust and CO detections favor a giant impact between large, volatile-rich bodies. This suggests that planetary-scale collisions, analogous to the Moon-forming impact, can release large amounts of gas as well as debris, and that this gas is observable, providing a window into the composition of young planets.

21 pages (double spaced, including references and figures), 3 figures, 1 table, published in Nature 20/10/2021, published version available online through SharedIt initiative at https://rdcu.be/cAlEy

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Cited by in corpus (12)

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• The vertical structure of debris disks and the impact of gas
• Primordial or Secondary? Testing models of debris disk gas with ALMA
• Large planets may not form fractionally large moons
• Hint of an exocomet transit in the CHEOPS lightcurve of HD 172555
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) IV: CO gas imaging and overview
• Characterization of debris disks observed with SPHERE
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) VIII: A dust arc and non-Keplerian gas kinematics in HD 121617
• Discovery of Volatile Gas in the Giant Impact Disk around the 150-Myr old HD 23514
• Discovery of carbon monoxide emission from five debris disks around young A-type stars
• Re-accretion of Giant Impact Ejecta Can Drive Significant Atmospheric Erosion on Terrestrial Planets
• HD 44892: The youngest (or oldest?) gas-harbouring debris disc around an intermediate mass star