"Maybe the big take-home point on this one is it's a pretty big object and it was only found 10 or 12 days before closest approach,"
I've said this before. The way they find these things is looking for movement against the distant background / starfield. That works pretty well for finding things, but there is one problem. Any object on a collision course with earth will NOT be moving across the background in the days leading up to the collision. It will appear stationary against the stars, so will not be detected by these systems. To some extent it also doesn't matter that we are orbiting the sun because while near, earth and asteroid will be in the same accelerating reference frame.
Another way to model it is to think of firing a projectile from earth into deep space and see how that tracks against the background. That'd be the reverse scenario and there will be no relative motion until it's far enough to not get the same influence from the sun.
What you're describing is known as Constant Bearing, Decreasing Range (CBDR), https://en.wikipedia.org/wiki/Constant_bearing,_decreasing_r... and generally doesn't apply to to the case of a nearby asteroid on a collision course with Earth. For the parallax created by our orbit to be negligible, the object would have to be very distant.
Sounds related to motion camouflage, which dragonflies use to hunt. Allows them to appear stationary, with the only sign they are on an intercept course is looming as their image slowly grows larger.
CBDR only requires constant velocity. Similar triangles are all you need. On short time scales even orbits are approximately straight. It still applies and may well be the reason this one was missed until so close.
This is an incredibly naive approach. All asteroids emit light in the infrared, to detect and track asteroids just takes an infrared telescope making apparent motion against any background completely irrelevant. NASA is working on this: https://en.m.wikipedia.org/wiki/NEO_Surveyor
I work on NEO Surveyor, I replied to the parent comment largely agreeing with you, however I wanted to mention that we do rely on apparent motion for determining if a source is moving (asteroid/comet). However IR is ideal for spotting asteroids for a few different reasons, a big one is that asteroids have a wide range of surface brightness. Think bright concrete to black coal, so in the visible spectrum a 100m light stony asteroid can be just as bright as a 500m coal colored one. It is very difficult to determine size from the brightness alone. However in IR everything is approximately the same temperature (largely proportional to the distance from the sun), so these things all glow in the IR directly proportional to their diameter.
>It will appear stationary against the stars, so will not be detected by these systems. To some extent it also doesn't matter that we are orbiting the sun because while near, earth and asteroid will be in the same accelerating reference frame.
I dont think that is true aside from the case where the asteroid vector is the exact opposite of the earth.
Even if the earth and the asteroid are in the same accelerating reference plane, the background is not.
If you have two race cars going in around a track and at one from the other, it still appears to be moving relative to the stands.
> If you have two race cars going in around a track and at one from the other, it still appears to be moving relative to the stands.
Right. Now put the stands on another planet and you start to understand the problem.
We need to be able to see an asteroid at a minimum of of 3-4x the distance between the earth and the sun to have enough time to do anything about it based on the average speed of 40k mph.
Now keep in mind that at that distance you are looking for something as "tiny" as 60 miles across, the accepted size that would unquestionably end life on earth. Something ~1km across would cause mass famine. In 1908 an asteroid less than 200 feet across flattened 80 million trees over an 830 square mile area.
Even if the stands are far away, even light years away, you pan through 360° every year. The fact that the background is far away means that it moves even quicker relative to a nearby object in a rotational frame.
If you spin around in a circle, hold your hand out and look at it, it will be moving very quickly against a distant background, like the horizon.
My point is that the distance to the background helps detection, not hurts it. If the background was nearby and co-rotating around the Sun, detection would be a near impossible.
Firstly, the several different unit systems in this comment give me a headache.
Next,
> We need to be able to see an asteroid at a minimum of of 3-4x the distance between the earth and the sun to have enough time to do anything about it based on the average speed of 40k mph.
Not really. The important variable is not distance, but rather the mass and velocity vector.
There could exist an asteroid that is currently barely 1 moon orbit away (~400 000 km), but has a velocity vector almost equal to that of Earth's. This asteroid could then be predicted to impact upon the next close encounter with Earth.
In general, the more distant the predicted impact date, the less the delta-v required to push the asteroid off its current path and avoid an impact in future.
> Now keep in mind that at that distance you are looking for something as "tiny" as 60 miles across
NASA and ESA have databases of some 35000 near-Earth asteroids, and many of them are orders of magnitude smaller than 100 km[1]. Our detection capability has significantly improved since efforts first started in the 1980s.
Asteroid impact avoidance is amongst the few natural disasters humanity has the technological, financial, and engineering capability to completely avoid.
We have both the firepower and the lift capability (if not now, then in the near future, dictated by the urgency of the asteroid impact) to deflect even a 12 km, Chicxulub-size impactor if detected sufficiently early. About 5-10 years' warning would be enough time for a large nuclear device to deflect such an asteroid, which would be a major achievement for humanity.
Really, we should have a moon base, 6 years ago. This makes me very anxious. We have all our eggs are in one basket.
As for detection there's some of them are coming from the other side of the sun, the one that Jupiter throw at us, It would be good to have a few more detection at L4, L3, It would be good to know what part of the earth is going to get hit. And evacuate them. Having a moon base off planet would be able to make all this coordination possible, because the amount of chaos that it would cause.So it needs a large gain antenna like the one that's in Australia that the Intuitive Machines lander low gain antenna was able to make two way contact with. The same one that was used to televise the Apollo missions.
I just can't, I can't emphasize enough the advantages to working and living on the moon. Shift all energy production all these experiments terraforming and such eco engineering To there just terraform one crater and start growing some plants . It shouldn't have been done so many years ago. It could be done with one pre-supply mission with a Falcon 9 and an Oberth Pumping orbit and then followed by a manned mission. Where the falcon heavy and dragon? The mayby recovered the second stage on the moon.
It's just been over thought, overly planned. I mean, against nature, we're nothing. It's impractical to think that we can. can't stop a meteor. We're never going to see it coming. We don't have five years to plan that I mean. I'm even surprised that any of the simulations converge . You know, don't need to be adjusted. We don't even have gravity physics consensus.
I can't be done on a Earth because it becomes someone else's problem far away because it usually backfires diffuses through the air in the sea. It does not happen on the moon. So I mean, you can make this terrible meltdown reactor and then just leave. Leave it in a crater. Those gamma rays are not going anywhere except up. I just put a thing that says no fly zone over it.
Seems that we put a lot of effort and money into these overly ambitious projects like going to Mars, which has absolutely no practical advantage when leaving the moon up there, unused. I mean, this isn't about Space tourism t's about survival. making the moon an exporter. It has everything that we don't have, but that we're running out of, rare earth minerals. oxygen. The only thing that's missing is carbon dioxide. And we're going to be bringing that. And as soon as the plans we grow up there, using that 24/7 solar. solar power. and have a greenhouse. All we have to do is breathe the air they make. They can extract oxygen from the regular and we can do it too with heat. And we can sublimate iron and build stuff. We can, we can figure out how to sublimate titanium from titanium dioxide. I mean, the conditions are so ideal. We we would go there cause it because we think it's easy. When we go there because we thought it would be easy, right? But right now, I think we think is is going to be a lot harder than it really is. There's sweet spots on them. Lunar S pole that are just 20 degrees C. To send stuff back down to Earth, you just have to shoot it at 2400 kph The railgun. will fall back down to Earth will take long. Superconductor is in permanently shadowed craters are almost sort of Ambient temperature. if not already. Type B, type 2 or whatever.
I actually work on NEO Surveyor telescope (surveying for dangerous asteroids), writing the simulation code use to track expected performance. So simulating +20 million asteroids and what will be visible during the mission. Motion is how we determine if there is an asteroid or just some static sky source (IE: star).
However your comment is not correct, everything moves, even in the days leading up to a potential impact things are constantly in motion. The only asteroids which appear stationary actually tend to be quite far away and just happen to be moving at just the right speed.
Things which are close to us, even impactors tend to have large angular velocities, very VERY few things come directly radially in. A part of this is that the Earth is rotating, if you are familiar with the parallax effect then the Earths rotation causes parallactic motion of the asteroids when close. IE, take a photo, wait 4 hours, and you, an observer on Earth, has now moved. The geometry has to be just right for close objects to be stationary, and a different observing position on Earth (or space) will see the object moving even if you see it stationary.
Earth is about 8000mi across. The moon is about 239000mi away. Looking at it from opposite sides would be about 0.016 degrees of angular displacement. And that's a couple days from impact.
>> So simulating +20 million asteroids and what will be visible during the mission.
How many impacts do you simulate? These are the ones we care most about, and I still think they will be the hardest to detect.
Here is a simulation I did in response to your comment, this is ~6 million impactors and their on sky velocity as they approach Earth. Dotted black line is our expected detectability limit, anything to the right of that is detectable.
On sky velocity is measured in degrees / day.
Thanks, that's really cool. And the detectability line is under 0.01 degrees per day, so the parallax from opposite sides of the earth is well within detectable at lunar distance. You also confirm that the detectability (due to motion) is dropping as the time to impact decreases, but this is apparently not a problem. Leave it to projects run by physicists to have exquisite measurement precision ;-)
thanks I think that that's really kind of scary, but motivational as to putting up a moon colony so that we just have a 2n base. H But I have. have a few questions. If you've got a minute, must be nerve wracking to work there.
looks like it would be coming from the sun's direction because it is kind of a. dominating force , but i wonder why a couple days after a flyby is when they are often detected. Is it just because the sun is able to light/heat it up more?
Also, I'm wondering what software you use to to do the modeling for one. And if it's open source. and if it's reversible , so you can back it up and fix positions when new datas comes in
https://en.wikipedia.org/wiki/Fermi%E2%80%93Pasta%E2%80%93Ul...
That was done at Los Alamos with a Maniac and the first version was fixed point, but as you can see it looks chaotic, but then there's a semi ring. There's a repetition. So I I'm guessing that's why that we care about are flybys. They go by once and at some point they'll come back.
This might help if you click the reversible to use fixed point. you can go back and and retrace.. the steps even with a rough integration.
as soon as you have a correction for any of them, you can place that correction. By reversing the entire model or the solver.
I'm guessing there's such a cloud of objects you use something like. Fluid solver, even if you had to do that to some other body, then may have had an influence on the body that's under investigation, and you have new data for that, it might help to make the prediction more accurate. And without introducing any discontinuities in the model, if the past positions help determine the future ones going back.
You can see here (Stam) that even though it's chaotic like an N body problem, there is a semi ring and it repeats. So what appears to be maybe chaotic over time would be periodicity of the lineup. Then it seems, though, when certain planets are lined up. It's more likely that it's gonna have this this. confluence of Of gravitational influence. that will bring it in our direction. I'm thinking thinking Jupiter, Mars, the moon and the sun and the earth in between. Jupiter all the way to the earth is basically one orbit. At that velocity S50 kilometers uh second.
Also, I wonder if. the if something hit the back of the moon, would we even notice that until we go to the back of the moon or with a lunar reconnaissance or over and we find some craters that have direct impacts so that it would have could have been our planet killer. I'm sure there's quite a few up there with some some markings that will indicate that it probably injected some heavy metal right at that very crater. A direct hit. The moon was in the way because the the lineup of the two bodies ,that caused the dynamic in the first place. I'm guessing here.
One more reason for deep space telescopes. A PHA about to impact will not have much movement in relation to the background stars when seen from Earth, but will be moving when seen from a different vantage point.
How large? "anywhere from 120 metres to 260 metres in diameter".
Is that bad? According to NASA, "If a rocky meteoroid larger than 25 meters but smaller than one kilometer ( a little more than 1/2 mile) were to hit Earth, it would likely cause local damage to the impact area. We believe anything larger than one to two kilometers (one kilometer is a little more than one-half mile) could have worldwide effects."
So... it would really suck if it hit a populated area, though that's unlikely.
well the Chicxulub impactor (The one that ended the Cretaceous Period) was estimated to be 10-15km. on the other end, the largest recorded asteroid in Siberia was 50-60m in size and did local but very noticeable damage[1], apparently 4x as powerful as the nuclear bomb that hit Hiroshima.
So 260m would be absolutely devastating, but wouldn't end civilization as we know it. it would absolutely destroy any state or smaller country it hit. if it hit/exploded above an ocean, we'd have record breaking tsunamis completely flood whatever coastal areas it hit.
> So 260m would be absolutely devastating, but wouldn't end civilization as we know it
It really depends. A ~100 m asteroid is roughly as energetic as some of the largest nuclear weapons ever detonated (~10¹ to 10² megatons).
As an example... It'd destroy London, and maybe some of its satellite cities like Luton, Oxford, and Cambridge, but the effects would be significantly diminished by the time the fireball radiation and the blast got to Nottingham.
I'm surprised there's no TNT equivalent comparing it to the biggest weapons humans have created. That always seems like a data point used when showing destructive forces.
> "This is a big object. An object of this size is going to have the equivalent impact energy in the hundreds of megaton approaching a gigaton," Brown said. "That'd be a regional impact. It's the sort of thing that if it hit the east coast of the U.S., you would have catastrophic effects over most of the eastern seaboard. But it's not big enough to affect the whole world."
Not very comfortable with how much that sounds like downplaying the effects. It would be the largest disaster in all of human history. For reference the estimated strategic nuclear arsenal of the United States is about 820 megatons and the largest US test detonation was 15 megatons so an impact of this size would be on par with or possibly worse than an all out nuclear war between the US and Russia. God knows what kind of effects that kind of blast would have, it would probably kill half the US population on impact and light the entire east coast on fire. No idea what would happen to the rest of the world after that but the supply chain “disruption” alone would mean millions starving and without fuel or medicine.
Nuclear weapons are targeted, an asteroid releasing 1000x the amount of energy of all the world's nuclear weapons isn't going to be 1000x worse. Perhaps it'll vaporize on impact in the middle of the Pacific.
The amount of "suckage" in case it would hit Earth is mentioned in the article:
> Fortunately, it won't impact Earth. But it would be a bad day if it did. "This is a big object. An object of this size is going to have the equivalent impact energy in the hundreds of megaton approaching a gigaton," Brown said. "That'd be a regional impact. It's the sort of thing that if it hit the east coast of the U.S., you would have catastrophic effects over most of the eastern seaboard. But it's not big enough to affect the whole world."
I recall that Google has a library that will answer the question, "given two identifiers like cluster names or machine names, which failure domains do they share?". Those failure domains can be like "they're in the same rack", "they share a power bus", "they're in the same physical building", "they're in the same geographical region", that kind of thing.
I wonder if it has since been updated to account for different disaster scenarios. It would be good to know, if you're storing 5 redundant copies of something critical, that all 5 copies won't be under 10 feet of water if an asteroid strikes one of the poles and melts all that pole's ice.
I can't imagine what data would be so critical that it's important to make sure it survives such an event, but that hasn't stopped googlers over-engineering internal things in the past.
The LOCKSS [1] digital preservation threat model (I've been told, there's a whitepaper if curious) considers nuclear first strikes and large solar storms -- they maintain a global network of servers for archiving and preserving academic research.
The biggest takeaway is that a former Queen member turned astrophysicist, Brian May. Rock on!
>> Asteroid Day, sanctioned by the United Nations, was started in 2014 by astrophysicist and former Queen musician Brian May along with Apollo 9 astronaut Rusty Schweickart along with a few others. The goal is to inform the public about asteroids and their potential threats as well as calling on governments to work on asteroid detection programs.
My physics might be wrong, but with Earth's radius at 6500km and Lunar orbit radius around 350,000km, probability of a collision course given asteroid being within a lunar orbit distance is only (6.5/350)^2 or 0.03%, or maybe even cleaner, 1 in 3000. So it's not that close a miss.
In terms of these things, its a hair's breadth, but in human terms it's incredibly distant. We don't have a great intuition about just how enormous and empty space is, how much of the universe (including our little patch) is just a seething void.
It's not about intuition, it's about probability of impact. All these articles talking about asteroids flying within a lunar orbit distance make it sound like we got away lucky. But that's still far, far away, and the chances of impact are quite remote, in absolute terms.
You will see this was actually spotted back in 2014, but only seen for a few days. When an object is only observed for a few days we generally cannot compute an orbit for it, there is just not enough data to pin it down. However during this current pass of it (the last time it will come by for at least a few centuries), we have enough observations to pin its orbit down. Note that a lot of this is automated nowadays, with automatic observation and "interesting" objects being flagged automatically. There are a lot of small rocks up there (sub 100m).
Your application for a tourist visa to the Earth Planetary Visitor's Bureau has been denied due to a clerical error. Please alter your course to enter a holding orbit until your application has been resubmitted. We thank you in your interest in visiting Earth.
So even if they announced on the day of the first observation, that's not really much notice to do anything about it other than start prepping for accepting of loss of life. I would seriously hope it took some amount of time for other people to verify/validate trajectory than the first person that observes it.
At this point, we're still at the point of needing years if not decades notice for us to even have a chance of actually protecting from an impact in a meaningful way.
I figure we could get a Falcon Heavy filled with rocks or something launched in a hurry. But, I did the math, and like you say, all we could do is watch.
Assuming the standard asteroid density of 2000 kg/m^3 [1], a 260 m diameter asteroid has a volume of 4/3 * pi * 130^3 = 1.84e10 m^3. Falcon Heavy can lift 16818 kg to a transfer orbit to Mars [2], which I assume is basically what it can do to reach an asteroid coming at us. A normal speed of space probes (without gravity assists) seems to be about 25,000 mph = 11600 m/s. Thus, it has a momentum of about 1.95e8 kg*m/s.
Assuming we hit the asteroid perpendicular to its motion, transferring all our momentum into transverse velocity, that is 1.95e8 / 1.84e10, or approximately 0.01 m/s. To ensure a miss, it would need to travel the whole diameter of the earth, 6.378e6 m, which would take 6.378e8 seconds, or about 20.2 years, which is the amount of time before impact we would need to hit the asteroid.
We would probably have more success hitting it head on. Since the earth is moving at about 3e4 m/s, we only need to delay the asteroid by 213 seconds. The minimum speed of an asteroid impacting Earth is 1.1e4 m/s, so we would need to move it backwards 2.343e6 m. This allows us to hit it slightly later, only 7.3 years ahead of time (in the best-case scenario). Assuming it could vary by a factor of two, we would need up to about a 14 year lead time.
Maybe if this was a Michael Bay movie, but real scientists know that an Earth ending level event would just laugh at your nukes as it just flew on by. In the grand scheme of the cosmos, man made nukes are but a mere gnat at the picnic nuisance.
To estimate this order of magnitude. A typical (non MERV) 1.2Mt B83 in the active US nuclear arsenal would likely vaporize ~100m diameter hemisphere to deflect a relatively large 3km asteroid. Assuming an asteroid at 1-10 km/sec relative velocity 12 days out is 1-10M km away and earth is ~10k km across. So a deflection angle of ~1-10mrad is needed for a 3km (~10km3) spherical asteroid mass of ~10^13kg.
A 5E15 J/Mt 1000kg bomb with a half momentum of about 10^9 kgkm/sec could deflect an angle of 0.1mrad 12 days out. Half energy conservation would gives you a similar ~0.01km/sec dV, so you'd need >10x more time or >10x more 1Mt nukes for a 3km asteroid. It gets much worse for larger asteroids, but interestingly dV doesn't change quickly with relative velocity since the required angle falls as the velocity rises.
If they knew it was going to hit, but not be an extinction event, maybe that makes some sense but realistically what kind of "prepping" can reasonably be done? Stock up on toilet paper?
If they knew it was going to hit and incinerate the surface of the earth, would they even say anything? Why create worldwide panic for no purpose?
Maybe, if you could pin point where that would be, but that's much more difficult than people give it credit. Margin of errors means thinking it will hit the east coast of the US, but wind up hitting the west coast. So you've evacuated for nothing, and didn't evacuate where it counts.
> If they knew it was going to hit and incinerate the surface of the earth, would they even say anything? Why create worldwide panic for no purpose?
Assuming 'they' knew it was a world-ending event... good luck getting everyone involved to not say anything to anyone, including their loved ones. I also imagine there are several agencies doing asteroid detection, so it's not like it's just NASA personnel we have to worry about.
The record shows many long winters,4 close tree rings. Global and in same strata. about 5000 yrs. So how can we survive that 4 winters? not impossible if coms,radio, light boards ,satellite messages.. and civility are maintained.During the Black death in England, funerals,and wills kept civility.
the lunar base can provide terra firma form dropping supplies and there's startups in that. i even proposed to AIG insurance company a lunar escape resort as futures,funding miners via from invested premiums into managed derivatives and holdings.moon should be a net exporter or technology and rare earth.
i'm late to this discussion but i work on unified gravity, its close, we had it a long time but its getting to be beautiful & simple. verifiable so far.
other possibility: A two burn oberth can zip a falcon heavy with high 50km/s towards a meteor if we saw it coming. this should be the 1000x higher priority over wars and genocides and pandemics and Gucci bags and mars fantasies and VR.
I've said this before. The way they find these things is looking for movement against the distant background / starfield. That works pretty well for finding things, but there is one problem. Any object on a collision course with earth will NOT be moving across the background in the days leading up to the collision. It will appear stationary against the stars, so will not be detected by these systems. To some extent it also doesn't matter that we are orbiting the sun because while near, earth and asteroid will be in the same accelerating reference frame.
Another way to model it is to think of firing a projectile from earth into deep space and see how that tracks against the background. That'd be the reverse scenario and there will be no relative motion until it's far enough to not get the same influence from the sun.