I work on the NASA NEO Surveyor project (and have helped out a lot on the WISE/NEOWISE mission, which found a lot of asteroids). I create and run simulations of asteroid detections, which ends up being mostly orbit calculations.
In the next few years the rate of detections of these sort of objects are going to go way up, NEO Surveyor and the Vera Rubin LSST telescopes are going to take our current knowledge of the solar system from about 1.4 million asteroids to approximately 10x that. It is somewhat difficult to estimate how many we will see, since the size distribution follows a power law, and small changes in our estimates of the slope can be huge changes the number which exist.
There are most likely hundreds of thousands to millions of a few meter sized asteroids flying around the inner solar system.
I recommend figure 12 to get a sense of how far we can see at any given moment.
The definition which is commonly used as "hazardous" is about a 140m asteroid, which would cause a significantly bad day regionally, but not end civilization. That being said, 50m is still a very very bad day.
These meter-ish size ones usually just make a pretty fireball.
For anyone else curious who wants some tangible sense of the dangers, the Tunguska impactor is estimated to have been 50-60m in diameter [1]. The impactor that created the Barringer Crater in Arizona is estimated to have been about the same size [2].
Regarding a 100m asteroid impact:
> The pressure blast would destroy buildings up to 9 miles (15 km) from ground zero, and windows would shatter more than 60 miles away (100 km). To make matters worse, as the partially burned rock hit the ground, it would trigger seismic tremors that would spread through the planet's crust, carrying the destruction further away from the epicenter. The debris ejected into the air by the force of the impact would rain back on the ground miles away from the impact site, and the finer dust and dirt would remain hanging in the air, spreading with the wind across large distances.[3]
I can imagine a 140m asteroid causing a very, very bad day indeed for a region.
Not an expert, just curious and I can type stuff into a search engine.
I wonder, could an asteroid be traveling at a relative-to-Earth speed of very slowly, so that the impact most like just "setting down" on Earth rather than slamming into Earth?
There is minimum amount of energy from falling down Earth’s gravity well. Earth escape velocity is 11 km/s. A big chunk of asteroid energy comes from Earth’s gravity.
On the other hand, the orbital speed of Low Earth Orbit is 8km/s. Thus, with regard to asteroid redirection missions, we'd need 'only' about 3-4km/s of Δv to prevent this 'gently setting down' asteroid from hitting the Earth by capturing it into orbit.
Definitely into science fiction territory here considering that DART resulted in a Δv measured in centimetres per second, but I'm still rather tickled by the idea of collecting a new moon for ourselves :)
If we don't need to capture it to orbit, but just avoid hitting the Earth, centimeters might be enough. The trick is to be able to do it way in advance.
Besides, why LEO? Even GSO is 11 times closer than the Moon.
You're quite right - attaining GSO would indeed require only another 3 or 4km/s. But it does seem a little unfair to put it in GSO; we'd surely want people in both hemispheres to get a chance to gawk at our new satellite!
I recently decided that I wanted to learn more about your field, so I set up a jupyter notebook and was perusing the available python libraries and I found this one[0] however it is apparently unmaintained.
Can you suggest any beginner tools or resources for a layman to learn more about your field? I've taken an intro orbital mechanics course, solar system geology course and one on exoplanet detection and I'd like to keep the kinds of skills that I got from those courses fresh in my brain.
I am in the rather lengthy process of open sourcing a library for orbit propagation, but the previous art which is somewhat modern is the python rebound package. It's original design intent was for asteroid collision simulations, but it has been generalized a lot since then.
Most of the state of the art in the field is algorithms from the 60s/70s, the classic software which many people use are packages like Mercury, written in either fortran or C++.
These factors are why I am attempting to release my code to the (small) community.
Astrophysics peeps, why is it that the danger seems to be only tied to the mass of the object. Given p=mv is (relative) speed essentially the same for all of them or otherwise inconsequential?
The range of mass is typically much larger than the range of velocities. There is an upper bound to the speed for the vast majority of things which are dangerous (escape velocity of the solar system). However there are orders of magnitude differences in mass.
Adding a little context for those not familiar with orbital mechanics: the speed of a circular orbit is directly related to its distance from the barycenter (i.e. the Sun). The asteroid belt is between the orbits of Mars (orbiting at 24km/s) and Jupiter (13km/s). Whilst an asteroid that strays far enough to hit Earth (orbiting at 30km/s) is by definition not in an exactly circular orbit, nor one always between Mars and Jupiter, the difference in speeds isn't that great. That accounts for ddahlen's point about the limited range of velocities.
A very rough calculation of mine involving a hypothetical asteroid in a elliptical orbit extending as far as Jupiter and right down to Earth, assuming no difference in orbital inclination to Earth and no significant gravitational perturbations, would result in a relative speed of 5km/s. The actual impact speed would be greater due to Earth's own gravity, adding an extra 11km/s.
Not all asteroids are from the asteroid belt, but I am under the impression that visitors from the outer solar system (which could be as fast as the upper bound that ddahlen mentions) are much more infrequent than stray asteroid belt objects, so the median impact speed would still be relatively slow.
We have spotted a grand total of 2 interstellar objects, they were moving faster, but are many orders of magnitude less numerous then the local stuff.
Just doing some back of the envelope calculations, looks like Omuamua was moving about 165,000km/hr (relative to Earth) when it was about at Earths orbital distance.
This speed is not actually a crazy number, it is a lot faster than the majority of things which could hit us, but there are geometries of things in our solar system which can reach these relative velocities. (For example things in retrograde, IE: reverse orbits) can lead to basically escape velocity + earths velocity.
I'm not an astrophysicist, but I was part of a D&D group with one a few years ago and the topic came up (outside the game). In practice the speeds fall into two fairly tight clusters (asteroids and comets), but you don't even need that to justify focusing on mass. There's a hard lower bound on everything, and also a hard upper bound on any object that is part of our solar system, and it works out to at most a factor of 40ish in kinetic energy between the slowest and fastest possible impacts. The masses of objects of interest have a much wider range.
Everything coming in speeds up when it falls to earth.
Tiny stuff burns up completely in the upper atmosphere, where the pressure is low, because they have low surface area per mass -- the atmosphere can stop them entirely. Their terminal velocity is low. (That is, when the velocity through air is high enough that the drag prevents gravity from speeding up the object any further.)
Medium objects have a higher terminal velocity get deeper into the atmosphere before exploding. Fragments from these (which now have higher surface area per mass) can then be slowed further by the atmosphere and make it to the surface, but not so dramatically. Bits of the Chelyabinsk impactor fall into this category.
Big objects have a high terminal velocity. They make it to the ground largely intact... and without being slowed as much by the atmosphere. That gives you craters and bad days for being a dinosaur.
Not into astrophysics, but I guess "faster asteroids experience higher forces when going through the atmosphere, therefore burning faster". Another explanation could be "most of asteroid's speed comes from Earth's gravity, not from it's initial state".
These are just random guesses though, so I could be completely wrong.
It is better, and yeah for anybody who read the series the ending was especially awful. It's been awhile but I feel like they packed at least one book into the last 2-3 episodes of the last season. The book series still has a weird 30 year jump, but you stay there awhile at least.
For the first few seasons of the show I thought they did a good job, even though (or maybe because?) the show departs from the books in a lot of ways. But they tried to cram way too much into the last season and just made it seem like jibberish.
Why does the graphic have two streaks and a triangle? I can't figure out where to get more information.
In case it's not clear what I mean, one streak is greenish and the other is yellow/red. The triangle is black and one edge of it is colored red and seems to connect the centers of the streaks.
I'll take an educated guess:
(1) they are two different elevations
(2) they are essentially heatmaps of strike probability elongated because of the earth's rotation
(3) the triangle is a right triangle situated in a plane perpendicular to the earth's surface so that the red line indicates the angle.
It's funny that they'd have a strike location on the surface given that they said it won't hit the surface. But maybe it's a standard way to do the graphic, in which case it represents where it would strike if it were big enough even though it's not.
> [T]he coloured regions represent impact probabilities (to 1, 3, and 5 sigma). The red-orange-yellow area shows where the asteroid would reach Earth's surface if there were no atmosphere in the way.
>
> But there is an atmosphere! So we also mark in green where the asteroid will be when it is at an altitude of 100 km. This is roughly where it will begin to break up and therefore where observers could start seeing a fireball.
>
> The red line would be the asteroid's trajectory between those two points, if it were still one solid object, which it won't be.
I think it's the uncertainty areas. One it's 100km height and the other for 0m. It can be seen better on these links [0] [1]. I think it's done this way to show the trajectory.
Luck has a lot to do with it, sure, but we're (thankfully) a bit more advanced than just hoping someone is looking through a telescope at the right place/time.
NASA's Center for Near Earth Object Studies does a lot of neat work related to this. For example, Sentry [1], the NEOWISE mission [2], etc.
Thank you for your useful comment. It sent me down a brief rabbit hole of looking for a grid of amateur telescope owners cooperating for NEO object detection. I found eSTAR for the big boy telescopes [1] [2], but nothing for enthusiasts. I ran across NEO Surveyor that launches in September 2027, will run for 5 years, and is aiming for 90% coverage [3], so I suppose a grid of amateurs contributing telescope time into a software-driven grid and detection system won't be helpful?
Although there's always luck involved, it was discovered by the Catalina Sky Survey, a survey specifically designed to spot near-earth objects.
Their main telescope has a very large field of view (20 square degrees), and takes only 30 seconds per exposure, giving it many chances to get "lucky".
Does anyone know how the 10,000 Starlink satellites and the other 30,000 LEO competitors by the end of the decade are going to affect spotting near-earth objects?
I would have a hard time believing "not at all".
Vaguely related this is my favorite amateur astronomer spotting accident ever, capturing supernova an hour before it happened which hasn't been done before:
In sailing and shipping, another vessel is set for a collision course for you if and only if its direction from you doesn't change (assuming both keep constant speed).
Is this roughly the same for orbiting bodies? If so, it would seem that things on a collision course would be harder to detect, as they're indistinguishable from bodies far away that don't move. Possibly orbital mechanics change this significantly, but over the course of a few days the earth's trajectory is pretty much straight.
Yes, up until recently. The Vera Rubin observatory will change that quite a bit, and soon. Most observatories and telescopes are currently aimed at deep field (very long exposures of tiny portions of the sky). There are a few surveys meant for transients (supernovae, variables etc) and those are also well suited for near earth objects: look at the Catalina sky survey and the zwicky transient facility. When I was (very mildly) involved, the Vera Rubin observatory expected its first 25% of the mission to be overtaken by observing new near earth objects, even as its mission was to catalog variable stars and spot supernovae and other transients.
Some interesting stories about how these surveys work today and how they will work in ~10 years. Right now, it’s so rare to spot a weird thing in the sky that the alarms are all verified by grad students in graveyard shifts. When the new observatories come online, there won’t be enough grad students in the world :) so it’ll all be ML.
There are a number of projects dedicated to looking for near earth objects that could impact the earth. Pan-Starrs and Atlas are the ones that come immediately to mind for me, but there are others.
Not really. What the article fails to tell you is that there have been many, many, many more than nine times that asteroids have been spotted, often years in advance, where the initial data had wide enough error bars to make an Earth impact possible, but continued observation quickly ruled that out and predicted, correctly, that the asteroid would pass near the Earth but miss it. True, those asteroids were quite a bit larger than 1 meter wide, but as the article's description of the "impact" shows, a 1 meter wide asteroid isn't a real threat anyway.
Well yes, but these are only spotted so late because they're so small, which also makes them harmless. Anything that would be large enough to do damage would be also easier to detect sooner.
I get the odds of landing in someone roof are tiny in this rural area -probably smaller than meeting a grizzly in NYC- however I won't call a grizzly "harmless". Perhaps the panic induced by not calling it harmless would cause more harm.
> Space rocks smaller than about 25 meters (about 82 feet) will most likely burn up as they enter the Earth’s atmosphere and cause little or no damage.
It's always very impressive to me seeing our ability to detect such obscure objects in advance getting better and better. We'll soon have such good detection capabilities that we may start to take these kinds of predictions for granted the same way we take accurate weather forecasts for granted. Can't wait to see the local meteorologist talking about actual meteors.
Unfortunately, only one of the clips has a long enough duration to hear the start of the sonic booms, soundwaves from the detonations reaching the microphone.
I have mixed feelings about this. One the one hand, I'm super excited that we can go from discovery to wide dissemination within a few hours. On the other hand, what's the chance of something like this happening with a much bigger asteroid.
Bigger object should reflect more light, making detection more likely.
In very simplified terms, say its roughly spherical, the amount of light grows with the second exponent, so twice bigger object reflect 4 times as much light - but it is also potentially 8 times as heavy (eq. volume grows with third exponent) & thus more dangerous.
Both, but in practice the coverage of dangerous sized objects is pretty good already and when the Vera Rubin Observatory goes online it will get an order of magnitude better.
> On the other hand, what's the chance of something like this happening with a much bigger asteroid.
The same as it's always been, which is to say you can live your life without worrying about it.
If our technology advances such that we can observe/find more and more of these, that doesn't affect the chances that a particularly sized asteroid hits the earth or not.
>> such that we can observe/find more and more of these, that doesn't affect the chances that a particularly sized asteroid hits the earth or not.
Maybe under classical rules, but we know know that the act of observation collapses the range of possible outcomes, potentially locking us into a collision by an asteroid that previously existed only as a probability cloud.
because the claim “quantum effects do not apply to large objects” is not the same as “large objects behave classically in expectation”. the former claim is flat false
it wouldn’t make it more likely and the chance of an asteroid deviating from classical trajectory even by a centimeter is less likely than any event ever observed before
Ya, if your "asteroid" is a subatomic particle in the quantum regime, maybe. But the impact of one such particle, even ultra-high-energy cosmic rays, can be safely ignored.
Everything of asteroid size, or on the Torino Scale [0] is in the realm described by classical mechanical physics, and it will merrily follow it's existing trajectory whether or not we know about it in advance.
So, the only question is whether or not it's better to know it's arriving some hours/days/weeks in advance.
* Certainly better in cases like this (observable but harmless).
* Definitely would be better in cases like the Chelyabinsk meteor [1] which caused a fair amount of damage and some injuries, if people would be given a warning to avoid being near windows, etc.
* Absolutely better in cases of regional devastation to global catastrophe where we have time and resources to alter the trajectory to reduce or eliminate harm. Even just enough lead time to only move many of the people out of the impact damage region is a definite benefit.
* YMMV in cases of in cases of regional devastation to global catastrophe where we lack time and resources to alter the trajectory or move people. Is it better to know you'll die in X hours or be surprised?
So, I'd say everything below Torino-5 is definitely a good discovery (I think this is a Torino-0], and everything above depends on circumstances. Overall, a very good idea.
another metric that affects the ... impact ... of such an event is also the speed of the asteroid. Unlike size, I suspect higher speeds would make it harder to spot (and once spotted there would be less time to take action)
If we are only surveying a portion of the sky at a time and a faster asteroid spends less time traversing that portion, the likelihood of detection is lower.
Assuming you are not. What kind of "streak" you are thinking about? Are you thinking about comets with their tails? Or motion blur?
Because if motion blur I would expect an asteroid on a collision course to have none. (at least in the short timeframe before the collision) Because "Constant bearing, decreasing range" is how a collision looks like from a first person perspective.
Your last paragraph is correct, but only very close to the collision. Things in orbit around the sun don't move in straight lines, even if their paths are going to intersect. The earlier you see it, the less it's moving straight at you.
(Of course, if it's going to hit you, the faster it's going, the more straight at you its path is at the same distance. But for the same amount of "not straight at you", faster leaves a bigger streak.)
Yeah given that were talking about objects that are colliding with the earth, the faster they will come closer to us the less time we'll have to spot them
> what's the chance of something like this happening with a much bigger asteroid.
Negligible. As I noted upthread, objects large enough to be do significant damage if they hit Earth and are on trajectories that could bring them close to Earth are routinely spotted years in advance.
According to NASA [1], asteroid needs to be larger than 25 meters to cause localized damage. It’d need to be larger than 1-2km to cause globally observable consequences.
You can hear meteors. They hiss as they go by a hundred miles overhead. Which is weird of course. There are theories. Electromagnetic effects and such.
Last time I witnessed a meteor shower (I guess it was early 2000s or late 90s in Brazil), I swear I could hear it, but it was so faint that wasn't sure if I was imagining the sound.
BTW, I was watching the meteors from the attic, where my dad had a music studio, so lots of transducers around. The radio waves theory from the article would make sense.
Asteroid 2024 RW1, which was discovered just hours before its atmospheric entry, made a dramatic appearance over the Philippines on September 4, 2024. The asteroid, roughly the size of a small car (about 1 meter in diameter), was detected by the Catalina Sky Survey and was initially designated CAQTDL2 before being named 2024 RW1.
The asteroid entered the atmosphere at a speed of approximately 11 miles per second (around 40,000 miles per hour) and burned up, creating a spectacular green flash visible to observers on the ground. Despite the cloud cover from Typhoon Yagi, the event was still visible and was captured on video by local residents.
This event marks only the ninth recorded instance of an asteroid being detected before it impacted Earth.
we have come so far. i vaguely remember a similar-ish discovery/announcement was made in the early 2000s. well, i was too young and too stupid to check the news myself (there was no internet, just tv and newspapers anyways) but i quite remember that respectable town leaders searched for answers in their bibles and qur'ans. strange times they were.
I get that the size is small and therefore harmless to earthlings, however I feel like I lied to my better half when defending ESA and NASA that they would not withhold information about large objects that will hit earth and cause doom and destruction. Our plan that we documented in the Armageddon movie also is suddenly unrealistic to me.
There are most likely hundreds of thousands to millions of a few meter sized asteroids flying around the inner solar system.
I did a large chunk of the numerical analysis in this paper: https://arxiv.org/pdf/2310.12918
I recommend figure 12 to get a sense of how far we can see at any given moment.
The definition which is commonly used as "hazardous" is about a 140m asteroid, which would cause a significantly bad day regionally, but not end civilization. That being said, 50m is still a very very bad day.
These meter-ish size ones usually just make a pretty fireball.
Some various links to data about this impact:
https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20R...
https://minorplanetcenter.net/mpec/K24/K24R68.html
Regarding a 100m asteroid impact:
> The pressure blast would destroy buildings up to 9 miles (15 km) from ground zero, and windows would shatter more than 60 miles away (100 km). To make matters worse, as the partially burned rock hit the ground, it would trigger seismic tremors that would spread through the planet's crust, carrying the destruction further away from the epicenter. The debris ejected into the air by the force of the impact would rain back on the ground miles away from the impact site, and the finer dust and dirt would remain hanging in the air, spreading with the wind across large distances.[3]
I can imagine a 140m asteroid causing a very, very bad day indeed for a region.
Not an expert, just curious and I can type stuff into a search engine.
[1] https://en.m.wikipedia.org/wiki/Tunguska_event
[2] https://en.m.wikipedia.org/wiki/Meteor_Crater
[3] https://www.space.com/asteroid-apocalypse-how-big-can-humani...
Definitely into science fiction territory here considering that DART resulted in a Δv measured in centimetres per second, but I'm still rather tickled by the idea of collecting a new moon for ourselves :)
Besides, why LEO? Even GSO is 11 times closer than the Moon.
Just to quantify the bad day scale: Tunguska[0] is estimated to have been 50-60m.
[0]: https://en.wikipedia.org/wiki/Tunguska_event
Can you suggest any beginner tools or resources for a layman to learn more about your field? I've taken an intro orbital mechanics course, solar system geology course and one on exoplanet detection and I'd like to keep the kinds of skills that I got from those courses fresh in my brain.
How do you recommend I do that?
https://docs.poliastro.space/en/stable/index.html
Most of the state of the art in the field is algorithms from the 60s/70s, the classic software which many people use are packages like Mercury, written in either fortran or C++.
These factors are why I am attempting to release my code to the (small) community.
https://x.com/raymongdullana/status/1831378111453392958
Velocity is important though.
A very rough calculation of mine involving a hypothetical asteroid in a elliptical orbit extending as far as Jupiter and right down to Earth, assuming no difference in orbital inclination to Earth and no significant gravitational perturbations, would result in a relative speed of 5km/s. The actual impact speed would be greater due to Earth's own gravity, adding an extra 11km/s.
Not all asteroids are from the asteroid belt, but I am under the impression that visitors from the outer solar system (which could be as fast as the upper bound that ddahlen mentions) are much more infrequent than stray asteroid belt objects, so the median impact speed would still be relatively slow.
Just doing some back of the envelope calculations, looks like Omuamua was moving about 165,000km/hr (relative to Earth) when it was about at Earths orbital distance.
This speed is not actually a crazy number, it is a lot faster than the majority of things which could hit us, but there are geometries of things in our solar system which can reach these relative velocities. (For example things in retrograde, IE: reverse orbits) can lead to basically escape velocity + earths velocity.
Looks like there is not a significant amount of variance in asteroid speed so mass would be the biggest deciding factor.
Tiny stuff burns up completely in the upper atmosphere, where the pressure is low, because they have low surface area per mass -- the atmosphere can stop them entirely. Their terminal velocity is low. (That is, when the velocity through air is high enough that the drag prevents gravity from speeding up the object any further.)
Medium objects have a higher terminal velocity get deeper into the atmosphere before exploding. Fragments from these (which now have higher surface area per mass) can then be slowed further by the atmosphere and make it to the surface, but not so dramatically. Bits of the Chelyabinsk impactor fall into this category.
Big objects have a high terminal velocity. They make it to the ground largely intact... and without being slowed as much by the atmosphere. That gives you craters and bad days for being a dinosaur.
These are just random guesses though, so I could be completely wrong.
https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress
The moon colony uses this to win its freedom.
However, The Expanse is also a great book
For the first few seasons of the show I thought they did a good job, even though (or maybe because?) the show departs from the books in a lot of ways. But they tried to cram way too much into the last season and just made it seem like jibberish.
Example of it being different process: bullets are accelerated by gun powder, but stopped by various armor.
Example of increased dificulty: interception rockets have higher demands on speed and agility. (If somebody tries to evade, you have to be faster)
https://planetaryannihilation.com/
The delta-v required for a heavy asteroid may make it more practical to send a fleet of nukes though.
In case it's not clear what I mean, one streak is greenish and the other is yellow/red. The triangle is black and one edge of it is colored red and seems to connect the centers of the streaks.
I'll take an educated guess:
(1) they are two different elevations
(2) they are essentially heatmaps of strike probability elongated because of the earth's rotation
(3) the triangle is a right triangle situated in a plane perpendicular to the earth's surface so that the red line indicates the angle.
It's funny that they'd have a strike location on the surface given that they said it won't hit the surface. But maybe it's a standard way to do the graphic, in which case it represents where it would strike if it were big enough even though it's not.
from https://x.com/esaoperations/status/1831349538583445693
TIL. It seems like it's basically luck if someone is looking through a telescope in the right place at the right time?
NASA's Center for Near Earth Object Studies does a lot of neat work related to this. For example, Sentry [1], the NEOWISE mission [2], etc.
[1] https://cneos.jpl.nasa.gov/sentry/
[2] https://www.jpl.nasa.gov/missions/neowise
[1] https://indico.cern.ch/event/423169/contributions/1890157/at...
[2] https://ui.adsabs.harvard.edu/abs/2002SPIE.4845...13S/abstra...
[3] https://www.jpl.nasa.gov/missions/near-earth-object-surveyor
https://www.techbriefs.com/component/content/article/33153-q...
https://en.wikipedia.org/wiki/Robert_Holmes_(astronomer)
https://www.youtube.com/watch?v=MWLDvuK_4qU
Their main telescope has a very large field of view (20 square degrees), and takes only 30 seconds per exposure, giving it many chances to get "lucky".
I would have a hard time believing "not at all".
Vaguely related this is my favorite amateur astronomer spotting accident ever, capturing supernova an hour before it happened which hasn't been done before:
https://www.popsci.com/amateur-astronomer-photographs-birth-...
makes me wonder when the sky becomes so difficult to see through if we are going to lose all that enthusiastic effort
Is this roughly the same for orbiting bodies? If so, it would seem that things on a collision course would be harder to detect, as they're indistinguishable from bodies far away that don't move. Possibly orbital mechanics change this significantly, but over the course of a few days the earth's trajectory is pretty much straight.
Some interesting stories about how these surveys work today and how they will work in ~10 years. Right now, it’s so rare to spot a weird thing in the sky that the alarms are all verified by grad students in graveyard shifts. When the new observatories come online, there won’t be enough grad students in the world :) so it’ll all be ML.
[impact streak cover some human infrastructures]
I get the odds of landing in someone roof are tiny in this rural area -probably smaller than meeting a grizzly in NYC- however I won't call a grizzly "harmless". Perhaps the panic induced by not calling it harmless would cause more harm.
https://maps.app.goo.gl/1LE4EnzBz13gH3zt5
https://www.nasa.gov/solar-system/asteroids/asteroid-fast-fa... https://physics.stackexchange.com/questions/47754/minimum-si...
> Space rocks smaller than about 25 meters (about 82 feet) will most likely burn up as they enter the Earth’s atmosphere and cause little or no damage.
(This one is 1m, so it's a pretty good margin.)
https://x.com/esa/status/1831337534950924348
Note though, this will likely have a huge range of uncertainty on it, as 8 hours of observation is not a lot.
I have mixed feelings about this. One the one hand, I'm super excited that we can go from discovery to wide dissemination within a few hours. On the other hand, what's the chance of something like this happening with a much bigger asteroid.
Lower.
As size increases there are fewer bigger asteroids to begin with, and they are also easier to spot.
In very simplified terms, say its roughly spherical, the amount of light grows with the second exponent, so twice bigger object reflect 4 times as much light - but it is also potentially 8 times as heavy (eq. volume grows with third exponent) & thus more dangerous.
Trade-offs. :)
That assumes that the detection is photon constrained and not "nobody is looking in most directions" constrained.
It doesn't matter even if the asteroid is carrying a lit magnesium torch if nobody is looking for it systematically.
I'm not saying that it is the case. In fact I'm asking: are we photon constrained or are we constrained by the rate we are scanning the sky?
The same as it's always been, which is to say you can live your life without worrying about it.
If our technology advances such that we can observe/find more and more of these, that doesn't affect the chances that a particularly sized asteroid hits the earth or not.
Maybe under classical rules, but we know know that the act of observation collapses the range of possible outcomes, potentially locking us into a collision by an asteroid that previously existed only as a probability cloud.
Everything of asteroid size, or on the Torino Scale [0] is in the realm described by classical mechanical physics, and it will merrily follow it's existing trajectory whether or not we know about it in advance.
So, the only question is whether or not it's better to know it's arriving some hours/days/weeks in advance.
* Certainly better in cases like this (observable but harmless).
* Definitely would be better in cases like the Chelyabinsk meteor [1] which caused a fair amount of damage and some injuries, if people would be given a warning to avoid being near windows, etc.
* Absolutely better in cases of regional devastation to global catastrophe where we have time and resources to alter the trajectory to reduce or eliminate harm. Even just enough lead time to only move many of the people out of the impact damage region is a definite benefit.
* YMMV in cases of in cases of regional devastation to global catastrophe where we lack time and resources to alter the trajectory or move people. Is it better to know you'll die in X hours or be surprised?
So, I'd say everything below Torino-5 is definitely a good discovery (I think this is a Torino-0], and everything above depends on circumstances. Overall, a very good idea.
[0] https://en.wikipedia.org/wiki/Torino_scale
[1] https://en.wikipedia.org/wiki/Chelyabinsk_meteor
Bigger asteroids are easier to see.
another metric that affects the ... impact ... of such an event is also the speed of the asteroid. Unlike size, I suspect higher speeds would make it harder to spot (and once spotted there would be less time to take action)
Though warning times will be shorter the higher the relative speed is.
If we are only surveying a portion of the sky at a time and a faster asteroid spends less time traversing that portion, the likelihood of detection is lower.
Assuming you are not. What kind of "streak" you are thinking about? Are you thinking about comets with their tails? Or motion blur?
Because if motion blur I would expect an asteroid on a collision course to have none. (at least in the short timeframe before the collision) Because "Constant bearing, decreasing range" is how a collision looks like from a first person perspective.
(Of course, if it's going to hit you, the faster it's going, the more straight at you its path is at the same distance. But for the same amount of "not straight at you", faster leaves a bigger streak.)
Negligible. As I noted upthread, objects large enough to be do significant damage if they hit Earth and are on trajectories that could bring them close to Earth are routinely spotted years in advance.
[1] https://www.nasa.gov/solar-system/asteroids/asteroid-fast-fa...
BTW, I was watching the meteors from the attic, where my dad had a music studio, so lots of transducers around. The radio waves theory from the article would make sense.
More info:
https://earthsky.org/space/whoosh-can-you-hear-meteors-strea...
https://www.space.com/35908-meteor-sounds-mystery-solved.htm...
https://www.youtube.com/watch?v=JqXZbrDZrVU
The asteroid entered the atmosphere at a speed of approximately 11 miles per second (around 40,000 miles per hour) and burned up, creating a spectacular green flash visible to observers on the ground. Despite the cloud cover from Typhoon Yagi, the event was still visible and was captured on video by local residents.
This event marks only the ninth recorded instance of an asteroid being detected before it impacted Earth.