"Our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass," they wrote in a new paper, which is available on the pre-print server arXiv.

From March 4 to 9, the comet brightened considerably - a cometary outburst.

About three weeks after the outburst, on March 30, a secondary chunk of comet was spotted.

According to the calculations made by Jewitt and his team, the early March outburst was a cloud of about 100 square kilometres (38.6 square miles) across, consisting of particles about 0.1 millimetres in size.

The team believes this chunk broke off the main nucleus during the early March outburst, but didn't appear for several weeks.

"Overall," the researchers wrote, "our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass: 2I/Borisov will survive its passage through the planetary region largely unscathed."