Why Sun's corona is hotter than its surface decoded

Scientists have found possible evidence of a source of energy that could be responsible for heating the Sun's atmosphere or corona.

In the study published in the journal Nature Astronomy, the researchers used data from the FOXSI-2 sounding rocket - a rocket payload carrying seven telescopes designed to study the Sun.

Space researchers have always wondered why the Sun's atmosphere or corona is so much hotter than its surface.

The main obstacle in answering the question is the lack of suitable instruments for measuring what occurs on the Sun's surface and its atmosphere, 'Phys.org' reported.

The researchers, including those from Japan Aerospace Exploration Agency, tested a theory that suggests heat is injected into the atmosphere by multiple tiny explosions on the surface of the Sun.

Such flares are too small to see with most observational equipment, so the idea has remained just a theory.

However, the new data offers some evidence suggesting the theory is correct.

To test the theory, the researchers looked at X-ray emissions from the corona and found some that were very energetic.

This is significant, because solar flares emit X-rays. However, the team was studying a part of the Sun that had no visible solar flares occurring at the time.

The researchers suggest the only likely source is superheated plasma that could only have occurred due to nanoflares.