Scientists see auroras in new colours on distant comet
Scientists have spotted ultraviolet auroras, similar to the northern lights, on a distant comet.
It is the first time that emissions on that wavelength have been spotted anywhere other than a planet or moon, researchers say.
The display was spotted on the comet comet 67P/Churyumov-Gerasimenko, known as Chury for short, which was examined by Nasa instruments on board the European Space Agency's Rosetta mission, which orbited around the comet from 2014 until it crashed into it two years later.
Researchers have been poring through the data sent back from that mission in the years since, in an attempt to better understand the comet. Even though the spacecraft was lost in 2016, new surprises continue to come from the data it sent back.
The new findings are described in a paper, ‘Far-ultraviolet aurora identified at comet 67P/Churyumov-Gerasimenko’, published in Nature Astronomy.
“Rosetta is the gift that keeps on giving,” said Paul Feldman, an investigator on Alice at the Johns Hopkins University in Baltimore and a co-author of the paper, said in a statement. “The treasure trove of data it returned over its two-year visit to the comet have allowed us to rewrite the book on these most exotic inhabitants of our solar system -- and by all accounts there is much more to come.”
Auroras on Earth – such as the northern lights – are created when electrically charged particles fly from the sun and collide with the upper atmosphere of Earth. As they crash, they create colourful and spectacular splashes across the sky.
Similar behaviour has been spotted elsewhere in the solar system, such as on Jupiter and some of its moons. But it had not been detected in comets until now.
Researchers had initially thought the light they could see was “day glow”, which happens when light hits the coma – or gassy envelope – that wraps around the comet itself. But further research has shown that it is actually the result of auroras of the kind we see on Earth.
“The glow surrounding 67P/C-G is one of a kind,” said Marina Galand of Imperial College London and lead author of the study. “By linking data from numerous Rosetta instruments, we were able to get a better picture of what was going on. This enabled us to unambiguously identify how 67P/C-G’s ultraviolet atomic emissions form.”
