Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 440, Issue 4, Pages 3757-3777Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stu476
Keywords
celestial mechanics; planets and satellites: detection; planets and satellites: formation; planet-disc interactions; circumstellar matter
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Funding
- STFC
- European Union through ERC [279973, 320964]
- [ANR-2010 BLAN-0505-01]
- STFC [ST/J001414/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/J001414/1] Funding Source: researchfish
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We consider the observational signatures of giant impacts between planetary embryos. While the debris released in the impact remains in a clump for only a single orbit, there is a much longer lasting asymmetry caused by the fact that all debris must pass through the collision-point. The resulting asymmetry is stationary, it does not orbit the star. The debris is concentrated in a clump at the collision-point, with a more diffuse structure on the opposite side. The asymmetry lasts for typically around 1000 orbital periods of the progenitor, which can be severalMyr at distances of similar to 50 au. We describe how the appearance of the asymmetric disc depends on the mass and eccentricity of the progenitor, as well as viewing orientation. The wavelength of observation, which determines the grain sizes probed, is also important. Notably, the increased collision rate of the debris at the collision-point makes this the dominant production site for any secondary dust and gas created. For dust small enough to be removed by radiation pressure, and gas with a short lifetime, this causes their distribution to resemble a jet emanating from the (stationary) collision-point. We suggest that the asymmetries seen at large separations in some debris discs, like Beta Pictoris, could be the result of giant impacts. If so, this would indicate that planetary embryos are present and continuing to grow at several tens of au at ages of up to tens of Myr.
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