The sun is smaller than we thought – DW – 04/12/2023

It is the constant companion of our days, and it has been It has been widely studied: The Sun However, what we thought we knew about its size has been challenged by a new study published in the journal Sun Monthly Notices of the Royal Astronomical Society Which uses innovative sound wave technology.

Historically, astronomers measured the Sun’s size by observing its photosphere, the part of it that emits visible light during a solar eclipse. This technique has been the norm since the 1970s, and sets the Sun’s radius at about 695,990 km. But, as with any celestial body, appearances can be deceiving.

Key: helioseismology

A team of researchers from the University of Tokyo and the Cambridge Institute of Astronomy decided to explore alternative dimensions of the Sun using a new approach. Using the Michaelson Doppler imager (MDI) at the Solar Heliospheric Observatory (SOHO), which is jointly operated by a pot The European Space Agency has applied astroseismology to the Sun, which explores the interior of the Sun by analyzing sound waves, a field known as helioseismology.

What they discovered was revealing. By tracking solar oscillations, that is, vibrations that pass through the entire sun, they were able to more accurately estimate its size. Traditional measurements based on the photosphere put the Sun’s radius at 695,990 km, but the new approach gave a slightly different result: 695,780 km, a difference of a few hundredths of a hundred.

Although this difference may seem small, it can have a major impact on our understanding of the Sun and its effects on Earth. The Sun is essential for sustaining life on our planet, providing light and heat, but it is also a source of magnetic storms that can seriously affect terrestrial communications. Incorrect solar radii can lead to incorrect conclusions about the Sun’s dynamics and layers, which could have important consequences for our solar readiness. Solar storms Potentially harmful.

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Different results, why?

“Seismic inferences say things about the nuclear reactions, chemical composition and basic structure of the Sun,” Douglas Gough of the University of Cambridge and Masao Takata of the University of Tokyo explained to the magazine. new world. This new data will allow scientists to reinterpret the reversal of sound speed on the Sun, suggesting that the heliosphere and photosphere may not exactly match the current Standard Model.

Why do these audio and visual methods give different results? Scientists aren’t sure yet, but they think it could be related to the solar cycle, which is the change in activity our star experiences every 11 years or so.

(New Scientist, ABC)

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