![]() Whereas the early crossings were a surprise, both of Solar Orbiter’s encounters were predicted in advance thanks to the computer code developed by Geraint Jones, University College London Mullard Space Science Laboratory, and extended by Samuel. Solar Orbiter itself crossed the tail of fragmenting c omet C/2019 Y4 ATLAS in May and June 2020, shortly after launching. The ESA/NASA Ulysses mission encountered three comet ion tails, including that of C/1996 B2 Hyakutake in May 1996, and C/2006 P1 McNaught in early 2007. Of those that have been detected, most have been noticed only after the event. This means that not only do astronomers now have data from inside the tail, they also have contextual images from these other spacecraft (see image gallery above).Ĭomet tail crossings are relatively rare events. The ESA/NASA SOHO mission and NASA’s STEREO-A and Parker Solar Probe spacecraft were observing from afar. As the image sequence progresses, changes in the tail can be seen in response to variations in the solar wind speed and direction.Īnd it was not just Solar Orbiter that was watching the crossing. These images show large parts of the comet’s ion tail taken while the spacecraft itself was inside the tail. The Solar Orbiter Heliospheric Imager (SoloHI) also captured data. “We are in the process of investigating some smaller scale magnetic perturbations seen in our data and combining them with measurements from Solar Orbiter’s particle sensors to understand their possible cometary origin,” says Lorenzo Matteini, a co-investigator on MAG from Imperial College, London. The magnetometer instrument (MAG) data does indeed suggest the presence of such draped magnetic field structures but there is more analysis to be done to be absolutely sure. This magnetic field is being carried by the solar wind, and the draping creates discontinuities where the polarity of the magnetic field changes sharply from north to south and vice versa. “Because of their small charge, these ions are all clearly of cometary origin,” says Stefano Livi, Lead Investigator of SWA-HIS from Southwest Research Institute, Texas.Īs a comet moves through space, it tends to drape the Sun’s magnetic field around it. SWA-HIS detected ions of oxygen, carbon, molecular nitrogen, and molecules of carbon monoxide, carbon dioxide and possibly water. Ions are atoms or molecules that have been stripped of one or more electron and now carry an electrical charge.
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