A 40 Myr Old Gaseous Circumstellar Disk at 49 Ceti: Massive CO-Rich Comet Clouds at Young A-Type Stars

TL;DR

This paper identifies 49 Ceti as a 40-million-year-old star with a massive, CO-rich circumstellar disk, proposing a colliding comet model to explain the observed molecular gas and suggesting the presence of large comet-like bodies around young A-type stars.

Contribution

It introduces a colliding comet model to explain CO abundance and identifies 49 Ceti as part of the 40 Myr Argus Association, revealing massive comet clouds around young A-type stars.

Findings

49 Ceti is a 40 Myr old star with a CO-rich disk.

The disk contains approximately 400 Earth masses of comet-like objects.

Additional young A-type stars show infrared excess indicating similar disks.

Abstract

The gaseous molecular disk that orbits the main sequence A-type star 49 Ceti has been known since 1995, but the stellar age and the origin of the observed carbon monoxide molecules have been unknown. We now identify 49 Ceti as a member of the 40 Myr old Argus Association and present a colliding comet model to explain the high CO concentrations seen at 49 Ceti and the 30 Myr old A-type star HD 21997. The model suggests that massive -- 400 Earth mass -- analogs of the Sun's Kuiper Belt are in orbit about some A-type stars, that these large masses are composed primarily of comet-like objects, and that these objects are rich in CO and perhaps also CO2. We identify additional early-type members of the Argus Association and the Tucana/Horologium and Columba Associations; some of these stars display excess mid-infrared emission as measured with the Widefield Infrared Survey Explorer (WISE).