The headline seems to be plainly wrong. It's an interstellar comet that supposedly has not had a close encounter with another star. But it certainly is not the "first interstellar comet to have visited our solar system", or did I miss something?
It is the first confirmed interstellar comet and so is the first under the interstellar comet classification, Unfortunate that the headline does not contain that detail however.
That was my reaction; I'm not sure whether they meant to say the "21/Borisov, the interstellar comet for whom our system is the first solar system it has visited", or (as other comments suggest) "the first confirmed interstellar comment to visit our system". Obviously if something is only now noticed with modern technology, it's unlikely that interstellar comets haven't swung by our solar system many times before. We just don't have a record of it.
It's somewhat debatable. 1I/Omuamua was reclassified as an asteroid because it didn't exhibit a coma. But it's possible that it's a remnant of a comet.
Despite reading quite a lot about astronomy, comets and asteroids and the history of all of the three, I didn't get the distinction between asteroids and comets yet. I understand the composition makes the difference, but I didn't get why we expect exactly two (!) distinct categories of intersolar/interstellar objects, and giving them exactly two distinct names. Why not more, or less (i.e. no distinction at all, just a summary of the probable composition)?
Why is this so? Is there a fundamental reason to make this special distinction, or is it just "tradition"?
UnlockedSecrets|4 years ago
elihu|4 years ago
davidcuddeback|4 years ago
firebaze|4 years ago
Why is this so? Is there a fundamental reason to make this special distinction, or is it just "tradition"?