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Space

The sun is smaller than we thought it was

Measurements of sound waves passing through the sun seem to confirm that it isn’t as big as we thought and we don’t fully understand its interior

By Alex Wilkins

7 November 2023

The sun with solar flares coming off it

The sun isn’t quite as big as we thought, so may release solar flares differently to how we expect

NASA

Our sun is fractionally smaller than it seems, which could change our understanding of its internal structure and behaviour.

Historically, astronomers have estimated the sun’s size by measuring the part that emits light, called the photosphere. This is done during a solar eclipse.

A different estimate of the sun’s radius can be found by measuring sound waves travelling through it. In the 1990s, astronomers did this using sound waves near the…

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