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Solar Orbiter to make serendipitous pass through the tail of a comet

The European Space Agency’s Solar Orbiter spacecraft will soon have a fortuitous encounter with a comet. The craft’s main mission is to capture images of the sun’s poles, which have never been seen before. But while it is on its way to the sun, it is already firing up its instruments and collecting data.

As luck would have it, along its journey the Solar Orbiter will pass through the tail of an intriguing object, comet ATLAS. Discovered in December last year, this exceptionally bright comet fragmented into pieces this April in a process that scientists are still trying to understand.

Hubble’s Observation of Comet C/2019 Y4 (ATLAS) on 23 April
A view of Comet C/2019 Y4 (ATLAS) obtained with the NASA/ESA Hubble Space Telescope on 23 April 2020. NASA, ESA, D. Jewitt (UCLA), Q. Ye (University of Maryland)

Given the size of the solar system, it’s very rare that a craft passes through the tail of a comet by chance. In fact, it has only happened six times before, and in all of these cases, it was only discovered when data was analyzed after the event.

The passing of the Solar Orbiter through the tail is the first time that such an event has been predicted in advance, which means that the researchers can turn on the most relevant instruments before the meeting to gather as much data as possible.

“With each encounter with a comet, we learn more about these intriguing objects,”  Geraint Jones of the UCL Mullard Space Science Laboratory and principal investigator of ESA’s future Comet Interceptor mission said in a statement.

“If Solar Orbiter detects Comet ATLAS’s presence, then we’ll learn more about how comets interact with the solar wind, and we can check, for example, whether our expectations of dust tail behavior agree with our models. All missions that encounter comets provide pieces of the jigsaw puzzle.”

The researchers are hoping that they’ll be able to capture a few precious particles from the comet’s dust tail. If a dust particle were to impact the craft it won’t do it any harm, but due to the extremely high speeds involved the particle would be instantly vaporized in a tiny cloud of plasma which may be detectable with its instruments.

“An unexpected encounter like this provides a mission with unique opportunities and challenges, but that’s good!” said Günther Hasinger, ESA Director of Science. “Chances like this are all part of the adventure of science.”

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