A novel mechanism could unravel the mystery of decaying exoplanet orbits

Why some exoplanets are spiraling towards their stars?


Hot Jupiter, which closely orbits its star, takes only a few days to complete a single orbit. This close proximity locks both planet and star in powerful gravitational tides that transfer orbital energy. This causes the planets to slowly spiral inward over billions of years until they are eventually consumed.

The system WASP-12b is a hot Jupiter whose orbital decay will hurl it into its host star, WASP-12, in a few million years. Current tidal theories cannot explain the observation of orbital decay in this system.

Scientists from Durham University have found a novel mechanism that could solve a long-standing mystery about decaying planetary orbits around stars. Their study suggests that stellar magnetic fields have significantly dissipated the gravitational tides responsible for the orbital decay of ‘hot Jupiter’ exoplanets.

Large magnetic fields found within some sun-like stars can effectively dissipate gravitational tides from hot Jupiter planets.

Inside the stars, the tides produce waves. These waves change into other kinds of magnetic waves that go outward and eventually vanish when they come into contact with the magnetic fields.

Reflecting on the research findings, the study’s lead author, Dr Craig Duguid of Durham University, said“This new mechanism has wide-ranging implications for the survival of short-period planets and particularly hot Jupiters.

“It opens a new avenue of tidal research and will help guide observational astronomers in finding promising targets to observe orbital decay.

“It is also exciting that this new mechanism could be observationally tested within our lifetime.”

The study’s results indicate that a few neighboring stars would make viable candidates for further hot Jupiter planet searches on deteriorating orbits.

If discovered, they might offer more proof of the influence of magnetic fields on tides from these extraterrestrial worlds.

The study may also shed light on where the tidal energy that has been dissipated travels inside the star.

Journal Reference:

  1. C Duguid, N De Vries, D Lecoanet, and A Barker. An efficient tidal dissipation mechanism via stellar magnetic fields. The Astrophysical Journal Letters. DOI: 10.3847/2041-8213/ad3c40


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