Giant planets can orbit in days
Planets with the mass of Jupiter orbit some stars in a few days, far inside the distance at which they were expected to form.
Established2 min read
51 Pegasi b, found by Mayor and Queloz in 1995, is a gas giant with a four-day year. Formation models had parked such planets beyond the ice line, where ices help a core grow. A giant next to its star was supposed to be rare or impossible.
They are common. The planets likely formed farther out and migrated in, dragged by the disk. Migration was the missing verb. The detections — radial velocity, then transits — are unambiguous. The surprise was nature’s, and then ours.
Caveats
- Not every giant is a hot Jupiter. They are a detected class, easier to find because they are heavy and close.
- Migration explains the orbit. The details of disk versus high-eccentricity migration still differ by system.
Sources
- 1Mayor M., Queloz D.. A Jupiter-mass Companion to a Solar-type Star. Nature 378, 1995.