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Gravitational nudges can dislodge comets from the icy outer areas of a planetary system and ship them on a collision course with the system’s planets. What sort of planets are prone to ensnare these inbound comets, and that are prone to wave them away?
R. Evans, J. Trauger, H. Hammel and the HST Comet Science Group and NASA
Comets on the Transfer
When the interstellar object ʻOumuamua sped by way of the photo voltaic system, its arrival confirmed what many astronomers had lengthy suspected: house is teeming with particles that has been kicked out of planetary programs by gravitational interactions.
However the identical gravitational interactions that may launch comets into interstellar house can as an alternative ship them careening into the internal areas of the planetary programs the place they have been born. When that occurs, the comets can settle into new orbits, be consumed by their host star, or, as a brand new publication explores, be accreted by the planets within the system. What determines whether or not a planet will acquire comets that wander near it, and the way would possibly the accretion of comets have an effect on our interpretation of exoplanet spectra?
Alan Fitzsimmons (ARC, Queen’s College Belfast), Isaac Newton Group
Commercial
Accreted or Scattered?
A workforce led by Darryl Seligman (College of Chicago) developed a set of equations that predict which planets are most probably to accrete inbound comets. The equations describe the probability of a planet accreting a comet into its ambiance or scattering a comet into a brand new orbit (or out of the system totally) as a operate of the properties of the planet — its mass and orbital distance — and people of the comet — primarily its eccentricity, which is a measure of how round or elongated its orbit is.
The workforce used their metric to find out which of the beforehand detected exoplanets are prone to have added cometary materials to their atmospheres. Seligman and collaborators discovered that, normally, planets categorized as heat Jupiters, super-Earths, and sub-Neptunes usually tend to ensnare passing comets than colder, extra huge planets.
Seligman et al. 2022
Composition Imposition
What does it imply for our understanding of distant planetary programs if exoplanets accrete a considerable amount of cometary materials? Probably, quite a bit! Planetary composition is assumed to narrate to the place in a protoplanetary disk a planet fashioned. Nevertheless, if planets accumulate cometary materials — which bears the chemical signature of getting fashioned far out within the disk — estimates of a planet’s birthplace based mostly on its atmospheric composition may be inaccurate.
Seligman and collaborators observe a number of causes that their estimates are possible an higher restrict on the quantity of cometary materials that planets accumulate. For instance, if comets in different planetary programs are likely to disintegrate or lose their unstable compounds shortly, the probability of exoplanet–comet encounters — and the impact they’ve on an exoplanet’s atmospheric composition — may drop.
Seligman et al. 2022
This difficulty is a well timed one, since based mostly on the workforce’s metric, almost the entire exoplanets that JWST will observe inside the subsequent 12 months have the potential to have accreted cometary materials.
Quotation
“Inferring Late-stage Enrichment of Exoplanet Atmospheres from Noticed Interstellar Comets,” Darryl Z. Seligman et al 2022 ApJL 933 L7. doi:10.3847/2041-8213/ac786e
This submit initially appeared on AAS Nova, which options analysis highlights from the journals of the American Astronomical Society.
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