TY - JOUR
T1 - Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions
AU - Unterborn, Cayman T.
AU - Desch, Steven
AU - Hinkel, Natalie R.
AU - Lorenzo, Alejandro
N1 - Funding Information:
C.T.U. acknowledges the support of Arizona State University through the SESE Exploration fellowship. The results reported herein benefited from collaborations and/ or information exchange within NASA’s Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate. N.R.H. would like to thank CHW3 and acknowledges the support of the Vanderbilt Office of the Provost through the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA) fellowship.
Publisher Copyright:
© 2018 The Author(s).
PY - 2018/4/1
Y1 - 2018/4/1
N2 - Multiple planet systems provide an ideal laboratory for probing exoplanet composition, formation history and potential habitability. For the TRAPPIST-1 planets, the planetary radii are well established from transits 1,2, with reasonable mass estimates coming from transit timing variations 2,3 and dynamical modelling 4 . The low bulk densities of the TRAPPIST-1 planets demand substantial volatile content. Here we show, using mass-radius-composition models, that TRAPPIST-1f and g probably contain substantial (≥50 wt%) water/ice, with TRAPPIST-1 b and c being significantly drier (≤15 wt%). We propose that this gradient of water mass fractions implies that planets f and g formed outside the primordial snow line whereas b and c formed within it. We find that, compared with planets in our Solar System that also formed within the snow line, TRAPPIST-1b and c contain hundreds more oceans of water. We demonstrate that the extent and timescale of migration in the TRAPPIST-1 system depends on how rapidly the planets formed and the relative location of the primordial snow line. This work provides a framework for understanding the differences between the protoplanetary disks of our Solar System versus M dwarfs. Our results provide key insights into the volatile budgets, timescales of planet formation and migration history of M dwarf systems, probably the most common type of planetary host in the Galaxy.
AB - Multiple planet systems provide an ideal laboratory for probing exoplanet composition, formation history and potential habitability. For the TRAPPIST-1 planets, the planetary radii are well established from transits 1,2, with reasonable mass estimates coming from transit timing variations 2,3 and dynamical modelling 4 . The low bulk densities of the TRAPPIST-1 planets demand substantial volatile content. Here we show, using mass-radius-composition models, that TRAPPIST-1f and g probably contain substantial (≥50 wt%) water/ice, with TRAPPIST-1 b and c being significantly drier (≤15 wt%). We propose that this gradient of water mass fractions implies that planets f and g formed outside the primordial snow line whereas b and c formed within it. We find that, compared with planets in our Solar System that also formed within the snow line, TRAPPIST-1b and c contain hundreds more oceans of water. We demonstrate that the extent and timescale of migration in the TRAPPIST-1 system depends on how rapidly the planets formed and the relative location of the primordial snow line. This work provides a framework for understanding the differences between the protoplanetary disks of our Solar System versus M dwarfs. Our results provide key insights into the volatile budgets, timescales of planet formation and migration history of M dwarf systems, probably the most common type of planetary host in the Galaxy.
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U2 - 10.1038/s41550-018-0411-6
DO - 10.1038/s41550-018-0411-6
M3 - Article
AN - SCOPUS:85045213463
SN - 2397-3366
VL - 2
SP - 297
EP - 302
JO - Nature Astronomy
JF - Nature Astronomy
IS - 4
ER -