From: University of California - Los Angeles
Published August 1, 2017 10:06 AM

Astronomers find that the sun's core rotates four times faster than its surface

The sun's core rotates nearly four times faster than the sun's surface, according to new findings by an international team of astronomers. Scientists had assumed the core was rotating like a merry-go-round at about the same speed as the surface.

“The most likely explanation is that this core rotation is left over from the period when the sun formed, some 4.6 billion years ago,” said Roger Ulrich, a UCLA professor emeritus of astronomy, who has studied the sun’s interior for more than 40 years and co-author of the study that was published today in the journal Astronomy and Astrophysics. “It’s a surprise, and exciting to think we might have uncovered a relic of what the sun was like when it first formed.”

The rotation of the solar core may give a clue to how the sun formed. After the sun formed, the solar wind likely slowed the rotation of the outer part of the sun, he said. The rotation might also impact sunspots, which also rotate, Ulrich said. Sunspots can be enormous; a single sunspot can even be larger than the Earth.

The researchers studied surface acoustic waves in the sun’s atmosphere, some of which penetrate to the sun’s core, where they interact with gravity waves that have a sloshing motion similar to how water would move in a half-filled tanker truck driving on a curvy mountain road. From those observations, they detected the sloshing motions of the solar core. By carefully measuring the acoustic waves, the researchers precisely determined the time it takes an acoustic wave to travel from the surface to the center of the sun and back again. That travel time turns out to be influenced a slight amount by the sloshing motion of the gravity waves, Ulrich said.

Read more at University of California - Los Angeles

Image: This is the sun. The white areas are where the sun's magnetic field is especially strong, and are close to sunspots, which can be larger than the Earth. The sun is emitting plumes of hydrogen plasma (for example, near the upper right). (Credit: SoHO, a joint project of the European Space Agency and NASA)

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