THE ROCHE LIMIT FOR CLOSE-ORBITING PLANETS: MINIMUM DENSITY, COMPOSITION CONSTRAINTS, AND APPLICATION TO THE 4.2 hr PLANET KOI 1843.03
- Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
- Department of Astronomy and Department of Planetary Science, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States)
- 37-575 MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139 (United States)
The requirement that a planet must orbit outside of its Roche limit gives a lower limit on the planet's mean density. The minimum density depends almost entirely on the orbital period and is immune to systematic errors in the stellar properties. We consider the implications of this density constraint for the newly identified class of small planets with periods shorter than half a day. When the planet's radius is accurately known, this lower limit to the density can be used to restrict the possible combinations of iron and rock within the planet. Applied to KOI 1843.03, a 0.6 R{sub Circled-Plus} planet with the shortest known orbital period of 4.245 hr, the planet's mean density must be {approx}> 7 g cm{sup -3}. By modeling the planetary interior subject to this constraint, we find that the composition of the planet must be mostly iron, with at most a modest fraction of silicates ({approx}< 30% by mass)
- OSTI ID:
- 22136607
- Journal Information:
- Astrophysical Journal Letters, Vol. 773, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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