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France

Scientists measure rotation rate of Sun's core

media Researchers have found out that the Sun's core rotates four times faster than its surface. SOHO (ESA & NASA)

An international team of scientists from France, Spain and the US have managed to measure the rate of rotation of the Sun’s core for the first time with high precision.

Using the GOLF (Global Oscillations at Low Frequencies) instrument orbiting around the Sun aboard the spacecraft SOHO, researchers have found out that the Sun’s core rotates once per week and is four times faster than its surface.

They managed to make this discovery by detecting the signature of gravity waves which are propagated from deep within the Sun.

Patrick Boumier from the Institut d’Astrophysique Spatiale, who is involved in the research, told RFI that the finding was a surprise.

“We know the Sun is a magnetic star. We know it for a long time thanks to the Sun Spots and solar flares. But we don’t know the value of the magnetic field inside the core. We were expecting an even faster rotation of the core, in case the Sun had no magnetic field and a similar rotation rate of the core as the surface if there was a relic of a magnetic field deep inside the Sun. We are in between these two cases,” he said.

He also added that the faster rotation rate of the core could help us understand its chemical composition and, in general, the process of stellar evolution.

Boumier said that the core’s rotation probably indicates that it is a relic of what the Sun was at the very beginning when the nuclear fusion reactions began around 4.6 billion years.

Boumier said that the signature of the gravity modes signal or g modes is very tiny on the surface. “These modes, which are driven by gravity, cannot propagate through the convection zone which is just below the surface of the Sun. Until now, we have been able to observe the acoustic waves (or p modes) driven by pressure for four decades.

Using 16.5 years of data, our lead author Eric Fossat developed a novel technique – an indirect method of uncovering gravity mode signatures in the observation of the p modes, more precisely through modulations of the p mode time of propagation inside the Sun.”

Using these modulations, the researchers were able to reveal another intriguing characteristic of our star.

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