NEWS NOTES
Is interstellar comet 2I/Borisov breaking up?
THE INTERSTELLAR COMET designated 2I/Borisov, discovered on its way into the Solar System in 2019, began shedding chunks in late March — more than three months after its closest approach to the Sun.
Two analyses of Hubble Space Telescope images taken between March 23 and 30 show fragments drifting from the comet.
Analysis of the images shows a small piece of the comet breaking off and floating slowly away, David Jewitt (University of California, Los Angeles) and colleagues found. The fragment was bright and only 180 kilometres from the comet’s core at the time Hubble took the images. What’s more, after processing the same Hubble images to increase the contrast between the core and the coma around it, Bryce Bolin (Caltech) and colleagues spotted a second piece farther out, floating away at more than 0.5 metres per second.
While the fragment that Jewitt’s team observed is about as bright as the comet’s core, he thinks this is due more to its icy surface than its size. Its mass, he estimates, is likely less than 1% of the whole comet, which would make the split more like a side mirror dropping off a car than the whole car falling apart. The piece that Bolin reports is likewise small, no more than 100 metres across based on its visibility.
While the data provide evidence that the comet is undergoing a fragmentation event, Bolin cautions that the event hasn’t yet destroyed the nucleus. “When comets catastrophically disrupt, their brightness drops very, very quickly… we’re not seeing that with Borisov,” he explains.
The timing is strange,
