Planets Form With Magnetic Storms

Astronomers might have solved an outstanding mystery of why forming planetary systems emit more infrared light than expected. The key lies with gas and dust suspended in giant magnetic loops.

This artist's conception shows the magnetic loops above a planet-forming disk.  NASA / JPL-Caltech

This artist's conception shows the magnetic loops above a planet-forming disk.
NASA / JPL-Caltech

Stars are born in enormous clouds of gas and dust. Small pockets in these clouds collapse under the pull of gravity. But as the pocket shrinks, it spins rapidly, with the outer region flattening into a turbulent disk. Eventually the central clump becomes so hot and dense that it ignites nuclear fusion, while the outer disk begins to form planets.

Of course, every detail of this process is not perfectly understood. In the 1980s, astronomers began finding more infrared light than expected around these nascent solar systems. While a planet-forming disk will absorb the star’s heat and then glow with infrared energy, this was not enough to account for the excess. Recent follow-up observations with NASA’s Spitzer Space Telescope have only furthered the puzzle.

Now researchers have developed computer models of planet-forming disks that suggest the answer: gas and dust suspended in magnetic loops above the disk will also absorb the star’s heat and glow in the infrared. These gigantic magnetic loops look similar to those seen on the Sun, where their sudden reconfigurations cause solar prominences to flare up above the surface.

In a young planet-forming disk, all of the primordial gas either falls onto the star or gets caught up in what will later become an orbiting planet. The flowing charged particles within the moving gas naturally create magnetic fields, which easily trap pockets of less-dense gas in the disk that then rise into the atmosphere. This essentially makes the disk two to three times taller, which is enough to account for all the excess infrared light.

JPL RELEASE:
Mystery of Planet-forming Disks Explained by Magnetism

Astronomers say that magnetic storms in the gas orbiting young stars may explain a mystery that has persisted since before 2006 . . . Read the full press release.

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