September 24, 2021

I, Science

The science magazine of Imperial College

A total solar eclipse, photographed from Jakarta, Indonesia. The eclipse provided new opportunities for scientists to study the Sun's atmosphere.

This week’s image shows a total solar eclipse, as seen from a cruise ship in Indonesia. The eclipse provided new opportunities for scientists to study the Sun’s atmosphere.

Last night UK time, Indonesia and the Pacific region saw the only total solar eclipse of 2016.

Total solar eclipses are relatively rare, occurring when the Moon passes directly between the Earth and the Sun, blocking the Sun’s disc completely and casting a shadow over a portion of the Earth. Depending on where you are standing, the eclipse will happen at different times of the day and vary in length. If you are in the middle of the eclipse path, directly under its shadow, the eclipse occurs around midday and lasts longer than in the outskirts of the enormous shadow’s path.

As well as being an exciting event for hobby-astronomers and space fans around the world, a solar eclipse is a special occasion for scientists. The eclipse allows us to see the region of the Sun’s atmosphere called the Corona. To study the Corona, you’d need a coronagraph – an instrument attached to a telescope which blocks out the Solar body and its strong light, making its periphery visible. The technique was invented 85 years ago, and has since been improved and perfected, particularly with the ability to mount telescopes on satellites. In outer space, the coronagraph does not have to overcome atmospheric scattering, which normally causes glares in Earth-based telescopes. However, there is no better coronagraph than the Moon. Its size and distance completely out-rivals that of any scientific instrument, making even the innermost region of the faint Corona visible.

You can catch the next solar eclipse in Africa on the 1st of September this year. It will only be an annular eclipse, meaning the Moon does not completely block out the Sun, leaving an ‘annulus’ ring of light around the moon, and so it will not be as useful for viewing the Corona. However, the annular eclipses leave some much appreciated natural light where the total eclipse does not – today in Indonesia, midday was as dark as a night with a full moon.

For a full list of the next ten years’ eclipse events, including lunar eclipses, head to this page:


Zoë Öhman is studying for an MSc in Science Communication

Image: Margot Sib/Ponant Cruises, via Instagram