Clues to the origin of hot Jupiters hidden in their orbits
Graduate School of Arts and Sciences, College of Arts and Sciences, The University of TokyoPeer-Reviewed Publication
The first exoplanet ever discovered in 1995 was what we now call a “hot Jupiter”, a planet as massive as Jupiter with an orbital period of just a few days. Today, hot Jupiters are thought to have formed far from their stars—similar to Jupiter in our Solar System—and later migrated inward. Two main mechanisms have been proposed for this migration: (1) high-eccentricity migration, in which a planet’s orbit is disturbed by the gravity of other celestial bodies and subsequently circularized by tidal forces near the star; and (2) disk migration, in which the planet moves gradually inward within the protoplanetary disk.
However, it is not straightforward to distinguish the mechanism a particular hot Jupiter experienced from observations alone. In the case of high-eccentricity migration, the gravitational perturbations can tilt the planet’s orbital axis relative to the star’s rotational axis, resulting in a measurable misalignment. However, tidal forces can realign these axes over time, meaning that an aligned orbit does not necessarily imply disk migration. As a result, there has long been no reliable observational method to identify planets that formed through disk migration.
To address this challenge, a research group led by PhD student Yugo Kawai and Assistant Professor Akihiko Fukui at the Graduate School of Arts and Sciences, the University of Tokyo, proposed a new observational method that takes advantage of the timescale of high-eccentricity migration itself.
- Journal
- The Astronomical Journal
- Funder
- JST SPRING, JSPS Grant-in-Aid for JSPS Fellows, JSPS KAKENHI Grant-in-Aid for Scientific Research (S), JSPS KAKENHI Grant-in-Aid for Scientific Research (B), JSPS Bilateral, JSPS Grant-in-Aid for JSPS