A gust of solar wind appeared to make a comet wiggle its tail as it passed close to the sun. More observations of this phenomenon could help astronomers learn more about space weather in the region close to our star, where it is hard to send probes.
Comets are small, icy objects that can be found whizzing around the solar system. As they zoom past Earth and approach the sun, their frozen bodies melt and release a stream of gas and dust known as a tail.
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In September 2020, astronomers discovered Comet C/2020 S3, also called Erasmus, as it was hurtling towards the inner solar system. By December 2020, the comet reached its closest approach to the sun at 0.4 times the distance between Earth and the star, just inside Mercury鈥檚 orbit.
Using the solar telescopes on board the STEREO-A and SOHO spacecraft, at the University of California, Los Angeles, and her colleagues tracked the comet鈥檚 path near the sun.
During the 34-hour period when the comet was closest to the sun, the comet鈥檚 tail swung like a pendulum, making a 30-degree angle on either side of the direction of travel.
鈥淲e saw that the tail had a very wide swing. That was unusual,鈥� says Li.
This behaviour was most probably due to an eruption of plasma and radiation from the surface of the sun, known as a coronal mass ejection, she says.
Based on their observations, the researchers calculated that the coronal mass ejection that hit comet Erasmus was travelling at an average speed of 205.5 kilometres per second.
鈥淭he study shows that it is possible to use comets as solar wind probes,鈥� says at Auburn University in Alabama. It has been difficult to measure solar wind properties very close to the sun in the past because it is hard to send spacecraft there, he says.
鈥淭his is a pretty interesting work,鈥� says at the University of Maryland. 鈥淲e don鈥檛 have a lot of observations like this because we can only do this kind of study when there is a comet in this region, which does not occur very often 鈥� usually no more than once or twice a year.鈥�
arXiv
