Gas-giant planets orbiting near other stars have powerful magnetic fields, many times stronger than our own Jupiter, in response to a new study by a team of astrophysicists. It’s the first time the strength of those fields has been calculated from observations.
The group, led by Wilson Cauley of the University of Colorado, additionally contains associate professor Evgenya Shkolnik of Arizona State University’s School of Earth and Space Exploration. The other researchers are Joe Llama of Northern Arizona University and Antonino Lanza of the Astrophysical Observatory of Catania in Italy. Their report was printed July 22 in Nature Astronomy.
More than 3,000 exoplanet systems containing over 4,000 planets have been found since 1988. Many of those star systems embody what astronomers name “hot Jupiters.” These are massive gaseous planets presumed to be just like the Sun’s Jupiter however orbiting their stars at close distances, typically about five times the star’s diameter, or roughly 20 times the Moon’s distance from Earth.
Such planets travel well inside their star’s magnetic field, where interactions between the planetary field and the stellar one could be continual and strong.
Earlier studies, the team says, have placed upper limits on exoplanet magnetic fields, for example from radio observations or derived purely from theory.
The magnetic field strengths the crew discovered vary from 20 to 120? gauss. For comparability, Jupiter’s magnetic discipline is 4.3 gauss, and Earth’s field strength is only half a gauss, though that’s sturdy sufficient to orient compasses worldwide.
The field strengths, the staff says, are more significant than one would anticipate contemplating the rotation and age of the planet solely. The usual dynamo concept of planetary magnetic fields predicts area strengths for the sampled planets, which might be a lot smaller than what the staff discovered.
As a substitute, the observations assist the concept of planetary magnetic fields to depend upon the amount of heat moving through the planet’s inside. As a result of their absorbing loads of extra energy from their host stars, hot Jupiters ought to have larger magnetic fields than planets of similar mass and rotation rate.