Scientists Explain Why Sun’s Surface Rotates Slower Than Its Core

Posted: Feb 7 2017, 6:14am CST | by , Updated: Feb 7 2017, 6:36am CST, in News | Latest Science News

Scientists Explain Why Sun’s Surface Rotates Slower than its Core
Credit: NASA/SDO

Sun's rotation is slowed down by its own photons

The core of the sun rotates slightly faster than its surface.

Sun is not a pure solid body. Its interior rotates like a solid sphere while most of its thin exterior spins at different speed. However the reason behind this odd behavior is largely unknown. No existing theory provides a complete picture of what is happening in the sun.

To better understand the imechanism, an international team of researchers looked at the images collected by the Solar Dynamics Observatory, which has been circling the sun since 2010. NASA’s Solar Dynamics Observatory or SDO is studying the solar atmosphere on small scales in many wavelengths simultaneously.

The treasure trove of images made it possible of researchers to get a detailed look at multiple layers of sun depth which eventually allowed them to measure the speed of the sun’s rotation at each depth. Researchers found that Sun’s exterior spun slower than its interior with outermost layer spinning 5 percent more than those below it.

Previous researches had shown that dust in interplanetary space is slowed by collisions with solar photons. When space dust slows, it loses angular momentum or the ability to continue moving in a certain way.

Researchers constructed a model of the sun to replicate this process. In the model, photons moving around the interior layers of plasma eventually encounter plasma that is much less dense at its outermost layer. When those photons collide with the plasma, plasma loses its angular momentum. That change slows down plasma's movement while the photons that cause it to lose its speed escape into space.

“I like the idea that photon emission can impart a significant torque on the outermost layers of the sun.” Hugh Hudson from University of California, Berkeley, who was not involved in the study told New Scientist. “This basic idea seems to have been missed before.”

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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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