The sun’s corona, shown similarly to how a human eye would see it during an eclipse, but through a green filter
ESA/Proba-3/ASPIICS
A carefully coordinated dance between twin satellites has created the first artificial solar eclipse in space, revealing the sun’s scorching corona in extreme detail.
The Proba-3 mission, which launched in December last year, is operated by the European Space Agency (ESA) and consists of two satellites flying at a distance of 150 metres from each other.
One of the satellites, called the Occulter, carries a 1.4-metre-wide carbon fibre and plastic disc, which blocks out the sun’s light for the second satellite, the Coronagraph, which is equipped with a camera and scientific instruments. To take the pictures, there can’t be more than a 1-millimetre error in how the two satellites are aligned.
In March, the satellites flew autonomously and lined up for several hours, taking multiple seconds-long exposures of the eclipsed sun. ESA scientists could stitch these together to produce full photos of the sun’s corona, the outermost part of its atmosphere, which can reach temperatures that are millions of degrees hotter than its surface.
“The first time I saw these pictures, it was difficult to believe,” says Damien Galano at ESA. “But quickly, it was also a very, very strong feeling of achievement and pride for everything we have done over the years.”
The above image shows the visible light of the corona, the same as would be seen by the human eye, but with a green filter.
This image shows light emitted from electron-depleted iron in the hottest regions of the corona
ESA/Proba-3/ASPIICS
Proba-3’s camera can also look at frequencies of light that correspond to specific elements in the sun’s corona, such as the darker green image above, which shows light emitted from extremely electron-depleted iron that exists in the hottest regions of the corona.
“We can clearly see the corona, which is already a major achievement,” says Galano.
The sun’s corona in polarised white light, which has been coloured artificially to appear violet
ESA/Proba-3/ASPIICS
The above image shows the sun’s corona, coloured artificially to appear violet, in polarised white light. This was captured using a special technique that allows scientists to separate the polarised light of the hot corona from light that is scattered by interplanetary dust.
These images were mainly to test that Proba-3 was working correctly, but when the mission is fully up and running it will be able to take pictures of artificial eclipses every 19.6 hours, each time it orbits Earth, including much longer exposures lasting up to six hours.
This will improve our understanding of the sun’s corona physics, says Galano, as well as help us to better understand the solar wind and coronal mass ejections, which affect space weather.
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