ARI SHAPIRO, HOST:
A remarkable object is rocketing through our solar system. It's a comet known as 3I/ATLAS. NASA caught a sharp image of it, which is striking because astronomer David Jewitt says that's like glimpsing a rifle bullet for a thousandth of a second. Jewitt is lead author of a forthcoming paper about the object in the Astrophysical Journal Letters, and he's here to share his team's finding with us. Welcome.
DAVID JEWITT: Hello.
SHAPIRO: This is only the third interstellar object observed entering our solar system. But we don't know where in the universe it came from. How do you know for sure that it came from outside the solar system?
JEWITT: The key signature is that it's traveling really, really fast relative to the sun. So it's going so fast that the gravity of the sun cannot hold onto it. It came in at about 40 miles per second, and that's just way too fast for the sun's gravity to be able to hold it back.
SHAPIRO: And that kind of points to the challenge of capturing it. How extraordinary is it to actually have an image of something going at that speed?
JEWITT: Well, we thought objects like this might be out there, for decades, maybe centuries. But we didn't see anything like that until the first one - the famous one - ʻOumuamua in 2017. It was very exciting because it's literally the tip of the iceberg. So this is the start of the study of a totally new population of bodies that we can look at with our telescope. So it's very exciting for that reason.
SHAPIRO: Yeah. It's kind of amazing that astronomers have always believed these things are out there, but it's only in the last decade that images of them have been caught - three of them. So how does this expand the potential for scientific discovery?
JEWITT: Well, it just reveals the population for the first time. So we can begin to try to measure them and try to understand them. And we have all these questions that we'd like to answer about them - not just where are they from, but how many of them are there? We think there's probably a huge number of them. How big are they? And, you know, the first two look completely different from each other. So the first one - ʻOumuamua - looked like basically a rock, an asteroid with no sign of any material coming out of it. Second one - Borisov - looked just like a regular comet in the solar system. So I think many people, including me, were wondering, well, what's the third one going to be like? And are they...
SHAPIRO: And what's it like? What's this third one like?
JEWITT: It's actually much more like the second one than the first one. So it has ice in the nucleus, and the ice gets warmed by the sun, and it turns into a gas. The gas streams away from the nucleus, and it blows out bits of dust, and then the bits of dust reflect sunlight and we see it as kind of a cloud or a coma surrounding the object. So it's an ice-containing body. It looks like a comet, so we think it is a comet. But it's a comet that doesn't come from our solar system. It comes from somebody else's planetary system somewhere else in the Milky Way, some probably very long time ago.
SHAPIRO: You are in your 60s. You've been at this for a while. What's it like to finally have this new area of research just open up to you for the first time?
JEWITT: Yeah. It's very nice, of course. It's happened before, right? So we found the Kuiper belt also in my lifetime. So it gives you this recognition that solar system is, even though you think we know everything about it - oh, we've sent a spacecraft here and a spacecraft there - gives you this recognition that actually we don't know much about the solar system. So these objects, even though they're not from the solar system, they're in the solar system. We have a lot of them, and we're going to be able to study them - figure out how many there really are and maybe figure out where they came from.
SHAPIRO: Well, if we assume that many more of these objects will soon be detected and studied and documented, is this one - 3I/ATLAS - going to mean anything special to you, or will it just be one in a long lineage?
JEWITT: It will fade away, you know (laughter)? So now we have three. When we have 300, for me, the field will be boring - right? - by that time.
SHAPIRO: (Laughter).
JEWITT: And then I won't work on it anymore. Other people can have it as far as I'm concerned.
SHAPIRO: David Jewitt leads analysis of images captured by the Hubble Space Telescope, and he's a professor of astronomy at UCLA. Thank you so much for talking with us.
JEWITT: OK. You're welcome.
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