An interstellar visitor is set to zip by the sun this weekend, exciting astronomers who hope to learn more about the workings of other solar systems.
The comet will reach its closest point to the sun on Sunday. It is the second known interstellar object to enter the solar system, and it comes just two years after researchers discovered the first one, Oumuamua.
The first visitor was discovered on its way out, so astronomers didn’t have much time to observe it. That didn’t stop, or perhaps fueled, speculation that the object was some type of alien technology, though a recent study disproved that theory. This time around, researchers have been able to watch the comet during its approach and are a little more confident that it is a natural phenomenon.
Photos: Space Over Time
Despite the advanced notice, not much is known about the new interloper, according to Matthew Knight, an astronomer at the University of Maryland.
For example, researchers don’t know its origin or how it exited its solar system. “Comets are unpredictable beasts,” Knight says.
But the comet appears to contain ice and a similar chemical makeup to comets in the Earth’s solar system. The findings mean “our solar system may well be a representative of what other solar systems look like,” according to Knight.
As comets warm when they approach the sun, they emit gases that can lead to a visible tail. Astronomers from Yale University recently photographed the comet and found its tail to be nearly 100,000 miles long.
Some have speculated that as the comet gets closer to the sun, it might disintegrate as the star evaporates the ice that holds it together.
Knight says it’s more likely the comet will pass by normally, but he emphasizes that comets can be highly variable.
“I think people are just hedging their bets on this because comets are unpredictable,” Knight says.
Researchers are surprised the comet came so soon after Oumuamua.
“We don’t have a great explanation for that,” Knight says. He expects more interstellar objects to be found as instruments and computing methods improve.
Known as 2I/Borisov, the comet was named after its discoverer, amateur astronomer Gennady Borisov. The finding shows that “in this era of massive telescopes … amateurs can compete,” Knight says.
After the comet passes by the sun, it will approach Earth, reaching its closest point – roughly 190 million miles away – about three weeks later. Knight says the comet likely won’t be visible with the naked eye unless it unexpectedly gets much brighter, and it could be challenging for even experienced amateur astronomers to observe.