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ESA: Small meteorite will safely impact atmosphere tonight over northern France
- Kukumber 4y agoLot of things going on in space lately Let's take a moment to remember this beautiful story: https://www.smithsonianmag.com/smart-news/reagan-and-gorbachev-agreed-pause-cold-war-case-alien-invasion-180957402/ https://www.smithsonianmag.com/smart-news/reagan-and-gorbach...
- dredmorbius 4y agoESA's own Twitter stream would be a more direct (and informative, in this case) source: <https://twitter.com/esaoperations/status/1624901825785724929 https://twitter.com/esaoperations/status/1624901825785724929> Looks as if the predicted entry point will be over Rouen. That tweet cites Richard Moissl (also on Twitter): <https://twitter.com/Richard_M_F/status/1624890692156751872 https://twitter.com/Richard_M_F/status/1624890692156751872>
- dang 4y agoOk, changed to that from https://twitter.com/disclosetv/status/1624909455325294593 https://twitter.com/disclosetv/status/1624909455325294593. Thanks!
- dredmorbius 4y agoAppreciated. (For those reading this: I'd of course emailed hn@ycombinator.com, largely with the text in my comment. It's an effective way to get attention / make changes to posts.)
- deleted 4y ago[deleted]
- dredmorbius 4y agoImpactor is ~1m in size, and projected impact time is 04:00 +/- 10 minutes CET (03:00 UCT). That's about three hours from now as I write this. My very off-the-cuff estimate is that a 1m impactor might mass anything from a few hundred kilos to a few tonnes, depending on composition (less for ice / chondrites, more for a heavy nickel-iron meteorite). Looking forward to the skycam views.
- version_five 4y agoStupid question: if the impact time is +/- 10 minutes, doesn't that translate into a lot of uncertainty for where it will hit? How do they know it's going to be Rouen?
- dredmorbius 4y agoMy (lay, nonexpert) understanding is: - The centroid of probability is near Rouen. - Earlier/later impact probability would be along a path along the movement/orbit of the impactor. I'm going to guess that that's largely east-west track, though with a possible orbital inclination. - The probability distribution across that range is likely far higher near the centre than at the extremes. - Relative motion of Earth's rotation (~1,600 km/hr at the equator, less than that at the latitude of Rouen) is a much smaller component than the likely relative velocity of the meteorite (~20 km/s). - 20 km/s +/- 10 minutes ... gives 12,000 km as a possible range around the impact site. There's also the question of accurately noting the original position of the impactor. That said: good question and I'd love to hear from someone who knows what they're talking about. Thought also comes to mind of Aristotle's future contingents, "there will be a sea battle tomorrow" ...
- cshimmin 4y agoHmmm, interesting analysis, but 12,000km is 3x wider than continental US. Based on the plot from ESA's projection, the track over the +-10m period is much smaller than France. I think the issue with your reasoning is that when you are dealing with orbits, you cannot really talk separately about position and (relative) velocity. Instead, for a given orbital trajectory, the position completely defines the speed. Moreover, your estimate might tell us how far _in space_ the impact would be given +/- 10min, but since both earth and asteroid are moving though space that doesn't really tell us much about how far apart it would be in an earthbound reference frame. In practice, I don't think they can accurately measure the position OR speed of an object like this... Instead, they make multiple observations over time and can fit the "shape" of the orbit, which can be done even with a fair amount of noise since we know all orbits are elliptical. If the object's orbit doesn't intersect Earth's, there's no impact. If the orbits do interest, there _may or may not_ be an impact event. To determine this, you have to figure out if both the object and the earth will be at that intersection point, _at the same time_. I'm guessing this is why the quoted uncertainty is given in minutes.
- jacknobody 4y agoThat's a meteor. Meteorites are different - they're the ones that hit the dirt.
- technothrasher 4y agoIf we're going to be pedantic, it's actually a meteoroid. Meteoroid is the object, meteor is what happens when it hits the atmosphere, and meteorite is when it has hit the ground.
- nick123567 4y agoI found Wiktionary the most helpful: Usage notes Meteor (streak of light in night sky): Not to be confused with meteoroid and meteorite (cause and remains of a meteor), or asteroid and comet (celestial bodies).
- ern 4y agoIt confused me as well. This post is mistitled. The original Tweet is: A 1-meter meteoroid (small #asteroid) has been detected and is expected to safely strike Earth's atmosphere over northern France between 3:50-4:03 CET.
- GalenErso 4y agoCould a F-22 shoot it down? /s
- rvba 4y agoIgnoring the sarcasm marker. F15s could fire anti satelite missiles in early 1980s. Who knows what "toys" are available 40 years later. https://en.m.wikipedia.org/wiki/ASM-135_ASAT https://en.m.wikipedia.org/wiki/ASM-135_ASAT
- version_five 4y agoBut this isnt an orbiting satellite, it's an object moving at 20 km/s (quoting another post, I dont really know in what direction or relative to what) which is ~Mach 60. I don't know how that compares to satellites - is it close enough we'd expect an anti-satellite missile to work?
- h2odragon 4y agoI think we might be able to put something in front of it; but at that speed I dont think anything we loft does not do more than begin the party early. All the energy it's going to release pretty much happens in the same path, we might just begin the breakup and distribution a second or two before the air otherwise would have.
- margalabargala 4y agoCan't speak to the missiles, but objects in low earth orbit travel at around 7km/s relative to the earth. The benefit of this sort of task is in both cases the target object doesn't move of its own accord, so presumably if you can predict the path of the object with enough precision then it would work. Clearly we can pinpoint a 1m satellite, but no idea on the error bars for a 1m meteoroid.
- kijin 4y agoDepends on what kind of warhead you have on that missile. :) A small nuke could definitely obliterate a 1-meter rock, if you don't mind contaminating a large part of Europe with radioactive dust.
- prvc 4y ago"Safely" because it is expected to burn completely before impact with the surface? If not, then fair to call it a potential hazard, even if a small one?
- chmod775 4y agoThese things don't even need to impact the surface to cause massive damage. They can disintegrate mid-air or just pass earth closely and the resulting shock wave will already be devastating. Examples: Tunguska explosion and the Chelyabinsk meteor. At their speeds they're impacting the atmosphere in a similar way a bullet impacts water (it disintegrates and loses speed rapidly, causing a big splash).
- codethief 4y agoAh yes, the Chelyabinsk meteor: https://www.youtube.com/watch?v=c9ch5mtxmLk https://www.youtube.com/watch?v=c9ch5mtxmLk Also, here's a great recording of the shock wave, illustrating your point: https://youtu.be/TKXZ5dwwTyc https://youtu.be/TKXZ5dwwTyc
- Aachen 4y agoWow!! From just east of Aachen, perfectly visible. Turning from a point of light coming down into a "oh wow that's really cool" into an actual fireball at >400 km horizontal distance! Holy crap that was exhilarating Edit: I was expecting that it would be too far away, also with Aachen's city glow and the highway, that nothing would be visible, or at best, a point appearing and disappearing at basically the same location in the haze of city glow. Compared to that, I'm absolutely blown away. Will post a video in a few minutes, just took the 380MB thing off my phone, now cropping to the right ~10 seconds, rotating, that stuff Edit again: here we are finally https://lgms.nl/files/Sar2667-Aachen.mp4 https://lgms.nl/files/Sar2667-Aachen.mp4 Quite sad it defocused, and you'll need an x264 decoder in your browser I think (I used `ffmpeg -c:v copy` to avoid losses, so it's whatever encoding my phone uses), should work in a local video player if you download it. A friend found this one https://www.youtube.com/watch?v=8owpwqzBEPA https://www.youtube.com/watch?v=8owpwqzBEPA Location estimate, based on where I saw it plus this video https://twitter.com/meteordoc/status/1624967987294765059 https://twitter.com/meteordoc/status/1624967987294765059 from Brighton looking over a pier: <https://www.openstreetmap.org/?mlat=50.0761&mlon=0.5335#map=8/50.0761/0.5335 https://www.openstreetmap.org/?mlat=50.0761&mlon=0.5335#map=...>. It became visible to me at 03:59:13 GMT+1/CET and exploded 5 seconds later, with my phone's clock sync being ~0.6s behind so it might have been 03:59:14 Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life of me find out which buildings are in view to map it to an angle. This location guess is going to be my final estimate.
- mendigou 4y agoGreat writeup, thanks! How did you check your phone's time synchronization?
- Aachen 4y agohttps://time.is https://time.is Per this thread https://twitter.com/tw__astro/status/1624908400902504451 https://twitter.com/tw__astro/status/1624908400902504451 it seems my time is a bit off, though. I took the filename and just checked the time offset in the video. Was considering checking metadata but thought 'nah, those few milliseconds difference'. However, exiftool says 2023:02:13 02:59:29, file name is 20230213_035256.mp4. Adding those three seconds to my previous guess comes out to the tweet's time. As I write this, I'm still... what's the word, excited? Thrilled? Like, I'm still not down to baseline relaxed. It's really just five seconds of light show, but looking at an astronomical event unfolding, knowing this is hundreds of kilometers away in northwestern France, the tiny voice in the back of your head as you see it explode "could they have been wrong about it being just 1 meter?" I wasn't truly scared at any point but the combination of feelings and awe is still a little bit with me.
- ggm 4y agoPhotos? Apparently, predicting arrival for natural near-earth objects is rare enough we're still in single digits. \ Very cool!
- deleted 4y ago[deleted]
- vermilingua 4y agoSee https://twitter.com/hashtag/Sar2667 https://twitter.com/hashtag/Sar2667 for some great shots of the impact.
- foreverobama 4y ago[dead]
- deleted 4y ago[deleted]
- pupppet 4y agoOr it won’t be a safe impact and the UFOs are here to watch the show.
- tehc-uk 4y agoI happened to be up watching the Super Bowl in the UK, saw the ESA tweet across my timeline and was able to pop outside to see it at the time they predicted - was also able to grab a video [0]. So cool to see how far our detection of these objects is coming along, especially for something as small as this was. [0] https://twitter.com/teh_c/status/1624967399131824130 https://twitter.com/teh_c/status/1624967399131824130
- Aachen 4y agoWould you be willing to share your exact location, perhaps in an email to sar2667observation@lgms.nl? From a sibling comment: > Got so lucky finding that Brighton video as the 2nd result earlier. Spent another 15 minutes looking for a third angle but the "looking east", "looking south" indicated angles are either implausible or too inaccurate to be useful. A Paris video is of such quality that I couldn't for the life of me find out which buildings are in view to map it to an angle. There is a building visible in your video, so with that info I could figure out the angle to get a third line. I currently have these two: https://snipboard.io/rBNozt.jpg https://snipboard.io/rBNozt.jpg Or if someone simply knows where to find someone who has a calibrated observation with range finder, I'd also be happy to find the location that way :D somehow I'm having a lot of trouble finding any information about this stone.
- mnw21cam 4y agoThere's a moon in that video. That'll give you the angle more accurately than a building.
- dmurray 4y agoHow? Everywhere nearby me, the moon is in the same direction, but my building isn't.
- Aachen 4y agoI considered that, but I don't think that works because where the moon appears in the sky also depends on where you are. There are two unknowns (moon and meteor) and one video (one equation), if I understand the math correctly (we didn't have solving multiple unknowns in school but this is the theory I heard in relation to GPS needing 4 sats to solve for x,y,z,time). It surprised me how many different combinations of meteor-moon constellations I saw in the various videos being posted. For some, the moon was very close; for me, the moon was like 110° removed I think (somewhere over my left shoulder). Maybe, knowing it was in England, it could help me to narrow down the scenarios (perhaps from an area down to a line?), but I don't have the experience to do that in a time-effective manner and I don't know if it would significantly help with the outcome.
- singularity2001 4y agowhy are these events always forecasted so late? some hours earlier i could have witnessed it
- spenczar5 4y agoTwo related reasons. 1m is quite small, so it needs to be close for us to detect it. Since we don’t have many observations, the error in estimates of its orbital path is high. In general, it also is extra difficult to calculate the exact last little bit of a trajectory that will impact earth because the force models start getting really wild as something gets very close to earth - approximations stop working.
- Aachen 4y ago> it also is extra difficult to calculate the exact last little bit of a trajectory that will impact earth because the force models start getting really wild What kind of forces? I assume you're talking about the space part, before atmosphere, so I would assume it's the same gravity effects that you also get in space, just that gravity is a bit larger value. I wrote a gravity simulator at lgms.nl/p/badgravity so I have a bit of an idea but am definitely no expert (the thing doesn't do any sort of collisions and assumes 2d point masses), so I'm curious what you mean. Especially with the earth dominating the gravity and not needing to use N-body physics anymore, it should get more accurate if anything. Could you elaborate or do you have a link? Or do you simply mean the compounding effect of having used N-body approximations for the interplanetary space part of the trajectory leading to different starting points for the final approach?
- throwaway4aday 4y agoMy guess is that the uncertainty has little to do with gravity, although there is gravitational variation in both the Moon and Earth depending on what part you are close to but I don't think that comes into play here. The error is likely more to do with the observational data. Try pinpointing the exact distance and trajectory of a 1m rock using ground based telescopes. Hard enough but remember there is also atmospheric distortion and you only get limited time on the scope.
- aaron695 4y ago[dead]
- Maursault 4y agoVideo from multiple locations.[0] [0] https://www.youtube.com/watch?v=_eJq6DcIEzM https://www.youtube.com/watch?v=_eJq6DcIEzM