When the interstellar comet 2l/Borisov made its first appearance in our solar system, astronomers were quick to turn their telescopes’ attention to it with the hope of learning more about what comets from other stellar systems might be like. At the least, we’d be able to compare these observations with comets from our own solar system, but on the more captivating side of things, we’d also potentially be able to learn more about the chemistry of the system it came from.
As it approached the Sun, 2l/Borisov shed quite literally millions of gallons of water to create the notorious ‘tail’ comets are renowned for. As it did this, NASA’s Neil Gehrels Swift Observatory took careful measurements in an effort to measure just how much water 2l/Borisov shed.
These measurements revealed that when the comet made its closest approach to the Sun, it shed enough water to fill a standard-sized bathtub in as little as 10 seconds – that’s a rate of approximately 8.5 gallons every second. It’s also worth noting that at least 55% of the comet’s surface was shedding water at the time of these measurements, and that’s up to 10 times higher than the level of shedding we traditionally see from comets here in our own solar system.
Perhaps unsurprisingly, the amount of water shed decreased as 2l/Borisov moved farther away from the Sun. Worthy of note, however, its water shedding curve dropped faster than any comet ever observed from our own solar system during this time.
In total, the Swift telescope measured a loss of approximately 60 million gallons of water during its brief trip through our solar system. It was the first time that astronomers had ever measured the water shedding of a comet not from our solar system, and the results were particularly fruitful to say the least.