ON THE EMERGENT SPECTRA OF HOT PROTOPLANET COLLISION AFTERGLOWS
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Institute for Astronomy ETH, Physics Department, HIT J 22.4, CH-8093 Zurich (Switzerland)
- Department of Earth, Atmospheric, and Planetary Sciences, Department of Physics, Massachusetts Institute of Technology, 54-1626, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
- Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 54-824, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)
We explore the appearance of terrestrial planets in formation by studying the emergent spectra of hot molten protoplanets during their collisional formation. While such collisions are rare, the surfaces of these bodies may remain hot at temperatures of 1000-3000 K for up to millions of years during the epoch of their formation (of duration 10-100 Myr). These objects are luminous enough in the thermal infrared to be observable with current and next-generation optical/IR telescopes, provided that the atmosphere of the forming planet permits astronomers to observe brightness temperatures approaching that of the molten surface. Detectability of a collisional afterglow depends on properties of the planet's atmosphere-primarily on the mass of the atmosphere. A planet with a thin atmosphere is more readily detected, because there is little atmosphere to obscure the hot surface. Paradoxically, a more massive atmosphere prevents one from easily seeing the hot surface, but also keeps the planet hot for a longer time. In terms of planetary mass, more massive planets are also easier to detect than smaller ones because of their larger emitting surface areas-up to a factor of 10 in brightness between 1 and 10 M {sub +} planets. We present preliminary calculations assuming a range of protoplanet masses (1-10 M {sub +}), surface pressures (1-1000 bar), and atmospheric compositions, for molten planets with surface temperatures ranging from 1000 to 1800 K, in order to explore the diversity of emergent spectra that are detectable. While current 8 to 10 m class ground-based telescopes may detect hot protoplanets at wide orbital separations beyond 30 AU (if they exist), we will likely have to wait for next-generation extremely large telescopes or improved diffraction suppression techniques to find terrestrial planets in formation within several AU of their host stars.
- OSTI ID:
- 21367382
- Journal Information:
- Astrophysical Journal, Vol. 704, Issue 1; Other Information: DOI: 10.1088/0004-637X/704/1/770; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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