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| Paper: |
Tidal Circularization and Kozai Migration |
| Volume: |
294, Scientific Frontiers in Research on Extrasolar Planets |
| Page: |
213 |
| Authors: |
Wu, Y. |
| Abstract: |
Extrasolar planets that lie close to their parent stars appear to have been tidally circularized. We quantify the circularization process using a quality factor Q which measures the inefficiency of tidal dissipation inside these planets. Observed data show Q ∼ 3 × 105, closely resembling that of Jupiter. We discuss the physical significance of this result. One of the planets (HD80606b) has a highly eccentric (e = 0.93) and tight (a = 0.46 AU) orbit. We study how it might have arrived at such an orbit and how it could have avoided tidal circularization. The presence of a stellar companion to the host star can cause Kozai oscillations in the planet's eccentricity. Combined with tidal dissipation, this can migrate the planet inward well after it has formed. Such a migration mechanism can account for the orbit of HD80606b, but only if the initial planet orbit was highly inclined relative to the binary orbit. We call this migration scenario "Kozai migration" and briefly discuss its relevance to other planetary systems. |
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