How does the new interstellar object differ from Oumuamua?

The second interstellar object recorded visited our solar system, according to astronomical observations made this week. But how does this new visitor differ from Oumuamua, the first interstellar object?

Scientists are eager to learn more about Comet C / 2019 Q4 (Borisov) since amateur astronomer Gennady Borisov first sighted it on August 30th. Subsequent observations showed that its orbit suggested that it came from outside the solar system. A comparison with the first interstellar object, "Oumuamua", could provide an interesting perspective on the general nature of these objects.

Astronomers discovered the first interstellar object recorded on October 19, 2017, and were able to gather hundreds of observations of this object as it traversed the solar system. It was strangely shaped like a cigar and seemed to accelerate as it moved away from the sun. There was wild conjecture about its origin and the cause of its acceleration ("extraterrestrials!"), But a less speculative debate centered on whether the object looked more like a rock asteroid or a comet that released gas and accelerated as it went. Sun warmed it up. The observations did not reveal a comet-like tail, but "a volatile-rich degassing structure for" Oumuamua provides the simplest explanation of its strange trajectory ", according to an article in The Astrophysical Newspaper.

Comet C / 2019 Q4 (Borisov) has slightly different characteristics. The first sightings have already revealed a coma and a tail resembling a comet. Its orbit also looks different. "It has the kind of orbit that is more characteristic of what we expected to see [from an interstellar object,]Matthew Holman, director of the Minor Planet Center, told Gizmodo last week. "Oumuamua plunged very deep into the solar system and approached the Sun; this is not the typical behavior one would expect.

Astronomers expect interstellar objects to be more like icy comets than rock asteroids because they are thought to have formed in their own star system. "When you come out of the star, the disc is colder, so the objects have more ice," said Kat Volk, a scientist associated with the University of Arizona at Gizmodo. They are presumed to be more like the frozen objects of the far-flung Kuiper Belt of our solar system. "Most things that are ejected would have more ice."

Astronomers also believe that the object is a little larger than "Oumuamua", although the veiled coma makes it difficult to conform to comet C / 2019 Q4 (Borisov), said Volk.

The observatories have just gathered enough evidence to conclude that the object probably has interstellar origins, and watching it has been (and will continue to be) difficult, since it is now relatively close to the Sun in the sky from our angle of vision on Earth. But fortunately, the object travels to the Sun, which means that we will have more time to observe it, as opposed to 'Oumuamua, caught in his journey to go.

And scientists hope soon to have more interstellar objects.

"A sample of two is really small, but it's better than a sample of one," said Volk. "We will continue to learn about them as we see more and more of them."