Radar, stellar occultations, and citizen astronomers

38:47>> Yeah. Over 29 years. >> So So you're capturing the movement even though the picture is static. >> Exactly. And it's not just pictures, it's also radar. >> Okay. Right. Because we can beam it and it'll come back. So it'll give us a distance at least from Earth. And then the beam will also get get blues shifted. Yes. Because the guy is either coming away from us or to like if it's if it's moving away then it'll be redshifted. If it's moving towards us the beam that bounces back will be blue shifted. And we can measure that difference in frequency to figure out the velocity. You do this over multiple >> years 29 years and you get a really nice >> right >> um number. And it >> and that's the before. And this is like we basically have a uh it's like a when

39:27you go on a run on an app like whatever Strava or whatever and you get the little trail and it shows like where you've run before. It's like we have that very precise of >> very precisely of the movement of this over time >> over 29 years it's been doing the same thing right over and over again. >> Okay. So now how do we get after cuz it's only been 3 years. We've only got three years not 29 in order to gather this data. So there's two ways to do it. One is through radio astronomy. Astrometry which is the same thing that I was saying earlier. So radio astrometry is simply you >> use radar to bounce a microwave signal there and back. They actually use the Goldstone solar system radar which is part of JPL's deep space network. This

40:08is actually whenever we go to Mammoth. >> Yeah. >> Um you know next time when we go I we should like just pull over and I don't think we can get in cuz it's like security or whatever but >> hey let us in. It's it's still like next time we go I'll I'll point out the radio dishes to you. Um >> so we we use that and from that we can we can get the time delay. So that'll tell us within tens of meters what the position is. We get multiple positions then we can calculate the momenta and also the fact that the signal is redshifted or blue shifted. That Doppler shift is going to give us some idea about velocity. But over 3 years it's not going to give us enough of that error bar going down. It's going to be part of it but we need something else. And this is where something very cool

40:48comes in. It's called stellar occultations. Okay. The idea is the asteroid is going to pass in front of stars in the night sky. No way. >> And it's going to eclipse stars. >> No way. >> And so we can measure whenever it eclipses stars, the star is going to blink. And we know the star doesn't actually blink, >> right? We the star has a constant brightness. So when it like goes down and up and we we know where it's going to be. So we're like, dude, this thing is going to this thing is going to move in front of that star. >> Yeah. like around this time. >> Yeah. >> So, we can have volunteer astronomers. And that's what I found very cool about the story. There were volunteer astronomers that went out. >> Yes. >> And tried to capture these stellar

41:29occultations. We're effectively trying to capture the shadow >> of this asteroid >> passing in front of >> passing in front of a star in the night sky. >> And the star. >> Yeah. The shadow is only about a kilometer wide. >> Oh my god. >> Okay. So you need very precise like timing of like where you need to be in order to capture it and also space. And one thing that I found really cool was there was a guy volunteer again. He observed >> two of these occultations. He drove two days each way in the Australian outback >> to get it >> in order to get this data. >> That's we we that's >> like shout out to this kangaroo jack guy, dude. Like >> the Aussies Aussie Aussie Aussie.

42:09>> Yeah. That's it's pretty awesome. But this is this is so interesting again because sometimes you know there's a lot of uh ast a astrophotographers I guess that that are very popular now on socials and stuff like that and it's a real craft in and of itself. >> Yeah. Yeah. Yeah. This guy had to know where to point like how to get the data exactly where to be because you've got a 1 km radius that you need to you need to get this thing >> and it you can not only do it for the joys of being curious about the universe around us but also be a participant and a contributor um into sort of instit institutional >> yeah research I think he should put planetary defense >> researcher >> researcher on his CV right whatever he's

42:52doing in the Australian outback like that should be that should be part of his CV So with this international network they captured 22 distinct occultations between October 2022 and March 2025. >> Okay. >> And that is where they got all of their data to where they can say 11 micrometers per second is the change in the velocity of this asteroid >> because now we have like another reference point another reference frame by which to like understand because we have the historical data set from the 29 >> and that's the before and we need an after and we need an after. And so basically the the the stars that are behind in between the stars that are behind this passing in between us >> create a a reference point for us to

43:33measure against. >> Yes. >> And that allows us to get the after because we have such a precise understanding of the stars and their positions. >> So it's almost like they're a ruler. The stars become a ruler by which we're measuring >> and it's extremely precise and that's how you get that precision in such a short time. If we just waited for Goldstone radar to keep going, we'd have to wait for it to come back and then like, you know, that's just going to take forever. But if you if we supplement that with this really tight >> astronomical data, right, and then we run the models on it, then we can get the error rate down to where we can really say, yep, >> 11 micrometers per second is how much we took away >> from that asteroid, which means that its year, which is about 2 years, is going

44:14to be shorter by 0.15 seconds. And that's how we get that >> data. >> That's so >> that's how we that's how we conclude that number >> but it's hard work. >> It's really and it's a really creative solution to the time problem because