Exoplanets' Magnetic Field Is Generated By A Totally Different Process

Posted: Nov 23 2018, 9:59pm CST | by , Updated: Nov 23 2018, 10:03pm CST , in Latest Science News


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Exoplanet’s Magnetic Field is Generated by a Totally Different Process
Credit: NASA Goddard Space Flight Center

Researchers suggest that super-Earths probably do have magnetic fields but they are generated by the planets' magma oceans.

We all know that Earth is surrounded by a magnetic field. Earth’s magnetic field extends from its iron core and acts like an invisible shield that protects us from harmful radiation from the sun. Now, researchers have found that super-Earths, a type of exoplanet, also contain magnetic fields but they are generated in a totally novel way, inside the planets’ magma oceans.

It is an important step in better understanding the magnetic field in planets outside our solar system.

“This is a new regime for the generation of planetary magnetic fields. Our magnetic field on Earth is generated in the liquid outer iron core. On Jupiter, it arises from the convection of liquid metallic hydrogen. On Uranus and Neptune, it is assumed to be generated in the ice layers. Now we have added molten rocks to this diverse list of field-generating materials,” said Burkhard Militzer, a UC Berkeley professor of earth and planetary science.

“This is far in the future, but if someone makes an observation of an exoplanet and they find a magnetic field, that may be an indication that there is a magma ocean, even if they cannot see this directly.”

As magma oceans cool from the top and material solidifies, a surface hospitable to life could appear while causing churning. This slowly churning melted rock at or under the surface can generate a strong magnetic field. The surprising discovery not only provides a way for astronomers to learn about the composition of distant exoplanets and the odds of life there but also suggests that Earth in its early years also had a magma-generated magnetic field.

“A magnetic field is helpful in protecting a planetary atmosphere from being blown away by the stellar winds," said former UC Berkeley postdoctoral fellow François Soubiran. “Most of the super-Earths we are detecting now are very close to their host stars and exposed to very strong stellar winds. Thus, the possibility for a magnetic field to exist is definitely a key component in the evolution of the planet and its habitability."

Earth's magnetic field is believed to be generated by the churning of electrically conductive fluids in the core. As the planet spins, its iron core creates dynamo and produces a persistent magnetic field.

To understand the process on exoplanets, researchers calculated the conductivity of three minerals, quartz (silicon dioxide), magnesia (magnesium oxide) and a silicon-magnesium-oxide (post-perovskite), all of which are common in rocks on Earth, the moon and most other planets in our solar system. When researchers combined lengthy calculations of these mineral with models of Earth's interior, they discovered that the rocks were sufficiently conducting to sustain a dynamo and thus a magnetic field.

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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