Discovery of Volatile Gas in the Giant Impact Disk around the 150-Myr old HD 23514

TL;DR

This paper reports the detection of CO2 gas emission in a giant-impact disk around the 150-million-year-old star HD 23514, revealing volatile retention during planetary formation processes.

Contribution

It presents the first observation of volatile gas in a giant-impact disk around a young star, linking silica dust and CO2 emission to past impact events.

Findings

CO2 gas emission detected around HD 23514

Silica dust remains stable over decades

Volatile gas and dust likely from a giant impact

Abstract

We report the discovery of CO$_2$ gas emission around HD 23514, an F5V star in the $\sim$150 Myr-old Pleiades cluster, hosting one of the rare giant-impact disks with unique mineralogy dominated by silica dust. We show that the dust feature remains stable over several decades, and that the sub-$\mu$m grains, which give rise to the $\sim$9 $\mu$m feature, are co-spatial with the hot CO$_2$ molecules within the sub-au vicinity of the star. Examining the Spitzer spectrum taken 15 years earlier, we show that the CO$_2$ emission was also present at 4.3 $\sigma$ significance. The existence of tiny silica grains and volatile gas requires special conditions to prevent the rapid loss caused by stellar radiation pressure and photodissociation. We explore several pathways explaining the observed properties and suggest that a past giant impact and/or stripping atmospheric event, involving large bodies with volatile content similar to the carbonaceous chondritic material, can simultaneously explain both the silica and volatile emission. Our discovery provides an important context for the amount of volatiles that a newly formed planet or the largest planetesimals could retain during the giant impact phase in the early solar system evolution.