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A model of magnetism for faraway planets

An artist's illustration of an evaporating hot giant exoplanet.
[Credit: NASA's Goddard Space Flight Center]

Researchers designed a model that measures the magnetic field of a distant exoplanet, or a planet outside of the solar system, and they suggest that it could be used to estimate the magnetic strength of other exoplanets as well. These magnetic fields can't be seen with the naked eye, but the invisible shields protect some planets, including Earth, from charged particles sent from the stars.

Kristina Kislyakova and colleagues took a close look at data from the Hubble Space Telescope, which showed a large, hot exoplanet--about the size of Jupiter--passing in front of the star it orbits. The Hubble data shows a strange pattern of charged hydrogen atoms moving away from the exoplanet, called HD 209458b, at very high speeds.

Astronomers have attempted to explain this Hubble data in various ways, but they haven't been able to settle upon a particular theory until now. Kislyakova and her team helped to settle the debate by designing a 3D model that includes everything researchers know about stellar winds and planets' atmospheres.

The researchers applied their new model to HD 209458b and discovered that stellar winds were traveling at about 249 miles per second as the Hubble recorded the exoplanet passing in front of its host star. They also say that the magnetism of HD 209458b was about 10% that of Jupiter's at the time.

In the future, these researchers hope that their model will be used to learn more about other exoplanets--and the interactions between such distant planets and their host stars.