By Deborah Byrd in SPACE | August 2, 2017
Eureka! After decades of puzzling about whether the sun?s core spins faster than its surface, astronomers can now measure it.

Our star, the sun, isn?t a solid body but instead a huge, shining ball of gas. Astronomers have long known it doesn?t rotate, or spin, as a single rigid mass. They?ve known, for example, that gases in the sun?s outer layers move around at different speeds depending on their latitude, with the equator spinning faster than the higher latitudes. The rotation of the sun?s outer layers varies from 25 days at the equator to 35 days at the poles. But what of the sun?s core? For decades, scientists have suspected the core moves faster than the surface, but, until now, no measurement was possible. Now an international team of astronomers, using data from a long-lived spacecraft called the Solar and Heliospheric Observatory (SoHO), has measured the rotation of the sun?s core and found it rotates nearly four times faster than the surface. The sun?s core spins once in about an earthly week, these researchers said. The study is published August 1, 2017 in the peer-reviewed journal Astronomy and Astrophysics.

These researchers ? led by astronomer Eric Fossat of the Observatoire de la C?te d?Azur in Nice, France ? studied acoustic waves, essentially sound waves, in the sun?s atmosphere. These are longitudinal waves; that is, the waves have the same direction of vibration as their direction of travel, and they move at the speed of sound. A statement from the European Space Agency explained more:
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Scientists had been searching for these elusive gravity waves in the sun for over 40 years, the ESA statement said, and although earlier attempts have hinted at detections, none were definitive.

This new study represents scientists? success at unambiguously extracting the signature of the gravity waves, and thus being able to measure how fast the sun?s core rotates.
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more: http://earthsky.org/space/suns-core-...r-than-surface