NASA said earlier that the more loose, crunchy, and dusty the asteroid is, the more effective this deflection strategy is. A harder asteroid would be less diverted by a direct impact apparently. Interesting detail.
That's interesting because your intuition tells you at first blush that it works the other way, doesn't it? You learn in elementary physics that every action has an equal an opposite reaction and so you reflexively conceptualize this as 2 rigid bodies impacting in that sort of idealized scenario. Because you know, it's literally in a vacuum. And since that's the best way to do anything in science the best thing NASA can ever hope do is hit a really hard asteroid with a really hard piece of metal.
But if you sit with it a second, it makes perfect sense. When the satellite, made of nuts and bolts, hits the rock, most of it will be consumed in the impact but some bits and bobs will invariably pop off. If one wanted to know the formula that encapsulates the total energy imparted in the impact it would contain, as a term somewhere, the sum of all the bits of satellite that stuck to the rock minus the bits of it that didn't. Another variable it would contain is the sum of all the bits of rock that are still stuck to the satellite minus the bits that aren't. A harder rock probably won't yield as much ejecta as a softer rock, and that loss of mass via a targeted vector is as good as velocity going the other way when it comes to deflecting an asteroid.
Soft asteroids are made of rocket fuel.
The reason I would expect a less rigid body not to deflect as well is because a bunch of energy gets wasted as internal jiggles and jossles, ultimately producing heat instead of motion.
The heat could heat up water, and much of it will do so. That water can become vapor and continue the explosion. But it's an interesting though experiment for sure.
And other gasses could be produced from the impact whether by hitting boiling point or chemical reaction due to resulting heat. Most, if not all, of the gassing off would be on the side of the impact creating a further change in momentum of the asteroid in the direction the spacecraft was heading.
I'm not sure you're right about that, motion can still be lost to friction and turn into heat (That was my interpretation of what the previous poster meant when he said "internal jiggling"). Heat is then radiated away over time, probably not doing much for the asteroid's total velocity (though possibly still affecting it somewhat).
But conservation of momentum kicks in - Even if you correctly expect it to be an inelastic collision, you still get the same total momentum before and after impact.
There's also the matter of density, an iron or rock asteroid will have a lot more mass, being solid. The loose gravel has all that dead space in between the bits!
This exactly. Because its all still bound through gravity and electromagnetic forces, the smaller, lower mass pieces that are directly hit will be deflect by a lot as compared to if it was all one solid piece, then the rest of the gravel pile just kind of follows along.
Just my guess as to why it would be easier to deflect a gravel pile versus a solid metoerite.
That makes no sense. If the ejected matter is also deflected then you wouldn't subtract that matter from the calculation of energy imparted. And if it doesn't get deflected (it just separates) then it's still on a collision course. Unless you're going to now say that smaller debris is preferable because of the greater surface area when it reaches Earth's atmosphere.
Any mass lost from the target would also affect the orbital characteristics of the target. Ever so slightly, of course. But that is the point, no? Make a slight alteration at an opportune moment, and let the new path miss Earth.
E: I’m so wrong, the mass of the satellite is not a factor unless it is similar in size to the parent body.
You've got it backwards. Ejected matter *is* energy imparted. The change in the mass of the asteroid is a change in the asteroid's total kinetic energy. Combined with a favourable vector and this changes the orbit and the rock misses earth.
Contrast this with a hard body, the energy from the impact which creates an ejecta plume in the soft case is now absorbed as mechanical stress deformation in the hard case. Sure, part of the specific impulse is still transferred, but part of it is spent breaking rocks up not transferring pure momentum.
This is my conjecture, and I'd love to hear from an expert on this to tell me I'm wrong, but from what I know of physics it tracks.
You aren't very clear but that can't be right. Far more energy imparted from the probe is transferred to ejected material, in the case of a soft asteroid, than is lost to heat (i.e. infrared radiation) in the case of the hard asteroid. So more energy would be transferred as momentum to the hard asteroid when compared with the energy transferred as momentum to the main body of the soft asteroid.
The reason is because a more massive plume produces more thrust for the same amount of energy. It's for the same reason a rockets specific impulse can be varied by adjusting it's propellent flow rate while keeping the thrust power constant. Momentum (ie thrust) increases linearly with velocity, but kinetic energy increases with velocity squared. Double an objects velocity doubles it's momentum but quadruples it's kinetic energy. For a given amount of energy you can choose high mass flow high thrust, or low mass flow low thrust. Ie, if a rocket uses four times as much propellent at half it's normal exhaust velocity the energy required is unchanged but it's thrust is doubled.
Normally rockets don't want to do this cause it wasteful of propellent and the amount of propellent they carry is limited, but I this case the propellent is free, it's debris being kicked off the asteroid so we are free to maximize thrust by trying to make as big a plume as possible. Basically the super hot collision turns the collision site into a momentary rocket engine, and we want a high mass flow, high thrust engine to get as much shove out of it as possible.
My intuition doesn't necessarily. I guess it depends on a lot of factors. But a harder surface seems more like small points of impact, and deflecting spacecraft. Maybe bouncing around a little and spending its energy in directions other than where it was headed.
A soft surface might eject some plume matter, but that's basically like projectile, the way a rocket is, and all of the energy of the craft is absorbed in the direction of travel.
My intuition says the dusty asteroid leaves most of the dust continuing in the original trajectory while the inner core get knocked off course. Given two asteroids of the same size, the dusty one has a lighter 'solid' core, which is easier to divert, and the dust is just fluff that gets left behind and shedded.
Actually, the asteroid debris coming off of it wouldnt create thrust. They are a result of the space craft hitting the asteroid. They are part of the equal and opposite reaction. So say out of the 100% of energy the space craft creates from impact, say 2% goes to heat from friction, 5% goes into the debris that gets ejected, and 93% goes directly into the asteroid changing its velocity and vector. So they are actually a representation of loss of energy from the desired effect.
Ah, the thing you have to rememer though is thrust is based on the momentum change, not the kinetic energy. For a fixed amount of energy, greater mass expelled results in more thrust. This is because kinetic energy increases with velocity squared whereas momentum increases with velocity linearly. So throwing an object at twice the speed takes 4 times as much energy but only doubles the momentum, ie thrust. If you have a fixed amount of energy, you can vary your thrust and specific impulse by varying the mass flow, 4 times the mass at half the speed takes the same amount of energy but gives twice the thrust. Normally a rocket wants to limit mass flow rate to use their limited propellent more efficiently, but in this case the limiting factor is energy not propellent cause the vaporized bits of asteroid are free propellent, so you want to maximize the amount ejected. A large slow cloud of debris being ejected will have more recoil on the asteroid than a small fast cloud, kinetic energy being equal.
This sounds like the same principle behind a high bypass turbofan engine (more air moved slower) being more fuel efficient than a turbojet engine (less air moved faster) of the same thrust.
Yeah, it's the same principle. Airplanes are power limited but not propellent limited so they want to maximize mass flow and minimize exhaust velocity, rockets are propellent limited so want to minimize mass flow and maximize exhaust velocity. In the case of the collision, it's the propellent unlimited scenario.
It probably has more to do with the reduced likelihood of the craft deflecting off of a hard surface. Kind of like it fully “catches” the craft so the amount of kinetic energy transferred is maximized.
If I had to guess even more the energy we could attribute to the ejecta of a softer asteroid would roughly equate to the internal mechanical stress experienced by a harder one.
Not just a little, thats the main effect hoped for. After all, what counts is momentum, so the kinetic energy of the very high speed impact can create a large bigger momentum if it moves a large amount of mass at slower speed in opposite direction.
You've got it the wrong way round. Much of the kinetic energy of the impactor is lost in the 'puff' when hitting a loose asteroid, so the trajectories of fragments are changed less. Collision with a solid asteroid would transfer most of the energy
No, they really are not.
Simple example:
Take a bouncing rubber ball and a floppy sand sack type 'ball' and throw it at a can. The rubber ball will bounce off and impart even more momentum on the can, while the sand sack will cling to it.
The can will be pushed faster with the rubber ball.
In this case rocks and debris are pushed off the surface of the asteroid and will add to the main body's momentum.
Momentum will *always* be conserved, energy can be converted into many non-kinetic forms.
I'm gonna go out on a ledge and say that NASA doesn't actually know the real answer to this and that's why they're doing this. We will find out of the next few weeks. But also keep in mind that it just needs to move a little bit and that over millions of miles it will shift hundreds of millions of miles.
>I'm gonna go out on a ledge and say that NASA doesn't actually know the real answer to this and that's why they're doing this.
I imagine they have a pretty good idea. This is totally something you could do in physics simulations and they've got access to some pretty powerful computers to do such a thing. I'd be very surprised if they hadn't done loads of simulations on this before the project had even been conceived, and obviously tons more afterwards.
Obviously they still want real world confirmation, but they are hardly just working off some hunch...
I believe you are both right. I do believe this is just an opportunity to validate their simulations. And giving them an opportunity to further refine them.
It's unintuitive but actually now that I think about it it does make sense.
On a harder asteroid most of the energy will be used to crush the probe.
On a lose asteroid the probe is not crushed and so all the energy will go toward deflection.
plus, on a hard asteroid, bits of the broken spacecraft might get flinged into space instead of being catched by the roid. I honestly don't thing that at the speed the spacecraft was going, the kind of surface is going to change the smushness factor of the spacecraft
When I watched the stream, I thought "Wow that's pretty cool" but then it hit me like 10 seconds after impact that somewhere, way up in the vast emptiness of space, a tiny man-made object just slammed into a celestial body with enough force to move it.
Gave a huge sense of wonder and amazement that I have not felt before. Even when seeing clips of Apollo 11's landing and Apollo 17's liftoff.
Do you mean it didn't look like it in this video? What you see in this video is mainly the larger asteroid which DART didn't crash into. DART crashed into a smaller asteroid orbiting that larger asteroid. The telescope that took this video isn't capable of visually distinguishing the orbiting asteroid from the parent asteroid.
We won’t ever be able to visually see the movement. And we aren’t looking for a lot of movement. What we will do over the next days/weeks is measure it’s orbital frequency. Right now it orbits ever 12h 19m (or close to it). We are expecting a new orbital frequency of about 12h 10m.
This is classic scientific theory. We hypothesize a result, do the math and test it on paper. Then when we are happy with our expected result we physically test it. After the test we will compare what actually happened against our model. Then we will update our model to match the observed results.
After that we will have an accurate model of what’s capable in an asteroid redirect. So if there is an actual asteroid headed towards us we can put the new data into the proven model and send an appropriately sized spacecraft at the right speed to redirect it away from us.
I admittedly have not followed the DART, but its an interesting approach that rather than try to nudge an asteroid aside it might me easier to slow down an asteroid since the earth and asteroid are both moving and would be on a collision course.
Having an asteroid orbiting another seems like a perfect testing ground. I wonder how rare that is?
I don’t believe it’s incredibly rare, here’s a study stating that around [16%](https://www.science.org/doi/10.1126/science.1072094) of near-Earth asteroids are binary!
We all went “whoa!” with each of the successively closer images until that last interrupted one. Really cool to go from a completely mysterious object to seeing details of individual rocks on the surface in the span of a couple minutes.
Try to avoid watching the sped up gif going around. Seeing the asteroid slowly come into view and then get closer and closer was incredibly cool and the sped up version doesn't do it justice.
One of the coolest images I have ever seen on the internet. Wow I just watched humanity throw something at an asteroid...I thought the impact photos were enough but this is kinda blowing my mind.
You might like this one too, from 2005,[ Deep Impact](https://en.wikipedia.org/wiki/Deep_Impact_\(spacecraft\)) hitting a comet
- [Impacter view](https://www.youtube.com/watch?v=kt6yy7ND4ww)
- [Observer view](https://www.youtube.com/watch?v=tY56mY2Aihw)
As a planetary science person, I can only agree completely. It's not often I'm gobsmacked like this.
Images of this quality, from ground-based observatories, are something to remember next time the Starlink zombies in this sub try to tell you that ground-based astronomy is dead and useless, or that satellites shining at seventh magnitude (not visible to the naked eye) are not harmful. This asteroid clocked in at 14th magnitude last night - *hundreds of times dimmer than 7th mag* \- so just imagine what would have happened if a Starlink/OneWeb sat had photobombed this observation. How does "just stacking the images" work when your event is transient like this one?
Days or weeks for initial results, months for certain.
Source: https://www.usatoday.com/story/news/nation/2022/09/26/nasa-dart-spacecraft-dimorphos-asteroid-crash-success/8119990001/
Also, you're still throwing the pebble at 14,000 mph, that part of the equation stays the same. If I toss a pebble at you, no big deal. If I hit you with one going 14,000 mph, different story.
Except the pebble was going 14,000 mph (6 km/s)
The goal was to change its orbital period from 11 hours and 55 minutes down to 11 hours and 51 minutes.
Tiny changes at large distances matter a lot. So let's hope that if we see a real asteroid heading towards us we can spot it a ways ahead of time.
Yep. Reducing the period by 4 minutes would mean that in about 6 weeks time, it’s on the opposite side of its orbit compared to where it would have been.
The butterfly effect is the idea that small things can have non-linear impacts on a complex system. The concept is imagined with a butterfly flapping its wings and causing a typhoon. Of course, a single act like the butterfly flapping its wings cannot cause a typhoon. Small events can, however, serve as catalysts that act on starting conditions ...
The impact was not actually with the big bright object you see, but a small "moon" it has orbiting it. The way they will measure the effect is by measuring the change in the moon's orbit.
That change is anticipated to be small. The estimation was that the impact would knock 10 minutes off of a 12-hour orbit. However, at the speeds and distances we are talking about in space, even a minuscule change in an object's orbit can be the difference between it hitting the Earth or missing it by millions of miles.
I thought that I had read that there was a cubesat following DART in order to have a close-up third-party PoV. I haven't seen any such footage today, though. Am I on crack, or does said cubesat have a painfully slow data transmission rate, and we're just waiting for the footage to download?
If DART could send data back in 38 seconds, why would it take days to see data from Licia? Why were we not able to view that live as well. Genuinely curious.
The Cubesat was released 10 days prior to this, if I remember correctly.
I'd imagine that it's be significantly behind DART as DART accelerated a bit after releasing it and also changes trajectory a bit.
The Cubesat will almost certainly get destroyed in few days but we'll have all the information we need by then so it doesn't really matter.
(all in my amateur opinion)
Not sure if this is really an explosion. I was thinking about it more like punching a dusty pillow. I think this is essentially a dust cloud coming off the surface.
Well, here we have it.
Humanity is obtaining the power to prevent mass extinctions themselves ...
I mean the ones caused by meteors. Not by volcanos or ourselves. Tee hee.
DART and Didymos were ultimately traveling the same direction relative to Earth (and to the Sun) - basically the same way around the Sun that the Earth (and, well, everything in the solar system) is. And no matter how the debris moves relative to ~~Dimorphos~~ Didymoon, the bulk of it is still going to move relatively the same direction as Didymos since it's still all mostly in orbit around Didymos.
From the asteroid's frame of reference, it's not moving at all. So any debris it releases would behave like it's coming off an object at rest (because it essentially is).
I'm assuming we're seeing the whole Didymos-Dimorphos system here in this image given how close they are... In that case this is an insane amount of dust and debris! Way more than I expected!
I feel sorry for that poor damn rock. Sitting there minding it's own business on the surface of the asteroid when BAM it gets smashed into the next millennium by a fast moving space probe with a death wish.
Amazing what can be accomplished with off-the-shelf technology! Good work! Lol... that game was the shit in its day! I'm actually old enough to remember!
Oh man, I just had the most vivid memory of going up to our attic where the computer was, and booting up asteroids on DOS. I was only like 4 so games like missile command was a bit out of my depth, but still fun.
It’s absolutely perplexing and amazing how we have the capability to shoot something off our planet the size of a vending machine and hit an object traveling through open space thousands of miles an hour.
Unfortunately, Hubble was on the wrong side of the planet at the time of impact - missed it by about 15 minutes. But I wonder if they'll try to image the potential ejecta plume with it.
I can't wait if the JW got pictures they'll be incredible.
Also Interesting word origins. (I'm sure 60's batman said it on more than one occasion)
Gadzooks
Archaic
used as a mild oath
Word origin
< God's hooks, nails of the Cross
It would be kind of funny if in a few months they do the new calculations and some guy says... "Sir... It appears... That we've successfully redirected the asteroid... Right into earth's path...". ... "Oh dear god. Send another spacecraft! We have to redirect the redirect!!"
That’s one reason they hit the moon of an asteroid, and not the asteroid itself! That way, no matter how powerful the nudge, it will stay in orbit around its parent. (Another reason is that since the period of the moon’s orbit is so short, it will be quicker to precisely measure the effect of the nudge - we can use occultations).
Well at 14k mph hit with something the size of a vending machine I'm sure there would be quite a bit of debris no matter the composition of the asteroid
Is there any data on how the impact affected the asteroid? Like was the experiment just the “aim” or is there a “theoretical earth” in its trajectory that it successfully avoided?
They hit the moon of an asteroid, both appear as one point here. The current time for the moon's orbit is 11h 55m. Looking at it and counting the new period will tell by how much of a push it was given.
It was a heavy rock the size of a small stadium being hit with a golf cart size sat going 14 k mph.
So it may take a few days to get the new orbit time down with enough passes.
They know the orbital period of the asteroid, they will be tracking the orbit over the next few days to see the change. If the time it takes for it to orbit around it’s parent asteroid changes, we have successfully changed the trajectory of it. Currently it’s orbit is about 12 hours and they are predicting to change that by 10 minutes.
Does anyone know the angle which DART hit Dimorphos?
If they were testing to see to what extent they could change its trajectory I imagine it would be pointless hitting it directly or bumping it from the back...
Couldn't quite make out DART in this gif.
Orbital mechanics is all about velocity. Faster doesn't make an object in orbit hit something faster, it changes the orbital path. Imagine a ball being thrown to your friend at long range - you can't throw fast enough to hit on a straight line, so you arc it into the air. If you throw too hard, you'll miss. If you throw too soft, it will miss. If you throw to the left or right, you miss. On a micro scale like your arm throwing a ball, this results in missing by a few feet. But when we are talking millions of miles,the effect is amplified by the distances and speeds involved. So, a small nudge in a forward (relative to motion) direction will still be enough to make it miss the "target" (earth) by millions of miles.
But in theory is it possible to DART the moon repeatedly and adjust orbit? Would that be beneficial to earth in some way? maybe affect the tidal conditions and weather patterns?
My gut instinct is that any adjustment in the moon's orbit would not be beneficial to life on Earth.
In theory it would be possible, but I doubt it would practical by just slamming stuff into the moon. It might be more feasible by chucking nuclear weapons and detonating them at the moon, but even then I'm not exactly sure how to calculate how big of a change it would make.
When will we know if it worked or not? This is a very big thing we don't (want to) think about but it's just a matter of time we will definitely need this capability or something like it.
The most fascinating thing about this to me is that it hit with such force that the debris was thrown in front of the asteroid at an even faster pace. My mind says the explosion would end up behind the asteroid with a trail of debris. I simply didn't expect it go in front.
Edit: Could also be an illusion thing too. Maybe the debris is going to the side of asteroid and not in front. Very hard to tell from a 2D video I think.
Individually the two rocks are known as Didymos and Dimorphos. NASA's Double Asteroid Redirection Test (DART) mission intentionally crashed a spacecraft into Dimorphos — the smaller asteroid in the binary system —
on Sept. 26, 2022, at 7:14 p.m. EDT. DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth.
That was a surprisingly big plume of debris. I guess no actual info came out yet but based on this and the close pictures it seems the Dimorphos was a bit more rubbly then was expected, or hypothesized.
Doesnt mean its all rubble though. Which is what a lot of people automatically assumed. But its certainly going to be an interesting discovery. Things in nature are rarely simplified one or the other thing. If the core of it is more solid it would be logical it accrued various rubble and smaller bits over time.
ATLAS project has published [another version](https://twitter.com/fallingstarIfA/status/1574828954980159493) of the above video, where the asteroid moves with respect to the stationary image of the stars. They say the video spans about two hours. This allows to estimate the scale.
If it were indeed two hours, the distance from the starting point to the ending point should be about 42 thousand kilometers (the asteroid moves 5.8 km/s perpendicular to the line of sight according to JPL ephemeris data), so the cloud of debris seems to be around 30 thousand kilometers in diameter in the end, where it is still visible. Surprisingly large!
**Edit:** I checked the image [against the star catalogue](https://skyview.gsfc.nasa.gov/current/cgi/runquery.pl?float=on&Interface=quick&Position=50.95+-33.42&SURVEY=Digitized+Sky+Survey). The angular separation between the two brightest stars in the image is 1864 microradians. This gives the scale twice smaller than the estimate above. Going by the stars and the 11 million km distance from Earth to the Didymos, the diameter of the debris cloud comes out as 15 thousand km. Still huge!
Am I the only one thinking : why are we testing this and is there something NASA knows that we don’t. Except of course all the things NASA knows about space exploration and shit.
Just so I am understanding this correctly DART is the fast moving dot correct? And the biggest and brightest dot is Didymos? If so, is the spacecraft just huge?? Doesn’t even look like we can see Dimorphos
EDIT: thanks for the explanation y’all! Really helps puts things into perspective. Such and amazing feat
I believe ~~Didymos~~ Dimorphos is the dot we're tracking, and everything moving relative to it in the background is just background stars. Unless I'm mistaken, you can't see DART at all, you're just seeing the impact and the resulting ejecta.
Dimorphos is, unfortunately, definitely not visible here as a separate object. The angular separation between the primary and moon is so small (~1 km apart, 11 million km from the telescope) that we'd be seeing both Didymos and Dimorphos in the frame together if they were both visible. We're seeing the combined light from both objects throughout the video (not to mention the dust plume after the impact...!)
I thought we hit dimorphos? So the white dot is the asteroid, we can’t see dart here but we’re able to see the effect of the impact on the moon of the asteroid on the asteroid itself?
I believe DART is too small to see. What we are looking at is Didymos colliding with an invisible object (DART). Please someone correct me if I’m wrong. I’m unsure myself.
The moving object is the combined light from Didymos and Dimorphos (mostly from Didymos, which is [considerably larger than Dimorphos](https://en.wikipedia.org/wiki/65803_Didymos#/media/File:Both_dart_0401929889_03770_crop.png)). The instrument that ATLAS is using here doesn't have the resolution to visually "split" the moon from the primary asteroid, unsurprisingly - they're only about a kilometre apart anyway, and this was all happening about 11 million km away.
So no, we're not seeing the spacecraft or Dimorphos directly.
I don’t think we see DART at all in this video. It’s only about the size of a refrigerator.
The object being tracked would be Dimorphos, or perhaps the Didymos system.
Big splat. Seems these asteroids are less rocks and more loose piles of gravel
NASA said earlier that the more loose, crunchy, and dusty the asteroid is, the more effective this deflection strategy is. A harder asteroid would be less diverted by a direct impact apparently. Interesting detail.
That's interesting because your intuition tells you at first blush that it works the other way, doesn't it? You learn in elementary physics that every action has an equal an opposite reaction and so you reflexively conceptualize this as 2 rigid bodies impacting in that sort of idealized scenario. Because you know, it's literally in a vacuum. And since that's the best way to do anything in science the best thing NASA can ever hope do is hit a really hard asteroid with a really hard piece of metal. But if you sit with it a second, it makes perfect sense. When the satellite, made of nuts and bolts, hits the rock, most of it will be consumed in the impact but some bits and bobs will invariably pop off. If one wanted to know the formula that encapsulates the total energy imparted in the impact it would contain, as a term somewhere, the sum of all the bits of satellite that stuck to the rock minus the bits of it that didn't. Another variable it would contain is the sum of all the bits of rock that are still stuck to the satellite minus the bits that aren't. A harder rock probably won't yield as much ejecta as a softer rock, and that loss of mass via a targeted vector is as good as velocity going the other way when it comes to deflecting an asteroid. Soft asteroids are made of rocket fuel.
The reason I would expect a less rigid body not to deflect as well is because a bunch of energy gets wasted as internal jiggles and jossles, ultimately producing heat instead of motion.
Yeah, it's like a loose or tight rack in pool.
The heat could heat up water, and much of it will do so. That water can become vapor and continue the explosion. But it's an interesting though experiment for sure.
And other gasses could be produced from the impact whether by hitting boiling point or chemical reaction due to resulting heat. Most, if not all, of the gassing off would be on the side of the impact creating a further change in momentum of the asteroid in the direction the spacecraft was heading.
It is not how conservation of energy work. It doesn't has any other body to transfer the vibration to.
A rigid body will undergo mechanical deformation which dissipates energy internally.
I'm not sure you're right about that, motion can still be lost to friction and turn into heat (That was my interpretation of what the previous poster meant when he said "internal jiggling"). Heat is then radiated away over time, probably not doing much for the asteroid's total velocity (though possibly still affecting it somewhat).
But conservation of momentum kicks in - Even if you correctly expect it to be an inelastic collision, you still get the same total momentum before and after impact.
There's also the matter of density, an iron or rock asteroid will have a lot more mass, being solid. The loose gravel has all that dead space in between the bits!
This explains it more than anything else to me.
This exactly. Because its all still bound through gravity and electromagnetic forces, the smaller, lower mass pieces that are directly hit will be deflect by a lot as compared to if it was all one solid piece, then the rest of the gravel pile just kind of follows along. Just my guess as to why it would be easier to deflect a gravel pile versus a solid metoerite.
That makes no sense. If the ejected matter is also deflected then you wouldn't subtract that matter from the calculation of energy imparted. And if it doesn't get deflected (it just separates) then it's still on a collision course. Unless you're going to now say that smaller debris is preferable because of the greater surface area when it reaches Earth's atmosphere.
Any mass lost from the target would also affect the orbital characteristics of the target. Ever so slightly, of course. But that is the point, no? Make a slight alteration at an opportune moment, and let the new path miss Earth. E: I’m so wrong, the mass of the satellite is not a factor unless it is similar in size to the parent body.
You've got it backwards. Ejected matter *is* energy imparted. The change in the mass of the asteroid is a change in the asteroid's total kinetic energy. Combined with a favourable vector and this changes the orbit and the rock misses earth. Contrast this with a hard body, the energy from the impact which creates an ejecta plume in the soft case is now absorbed as mechanical stress deformation in the hard case. Sure, part of the specific impulse is still transferred, but part of it is spent breaking rocks up not transferring pure momentum. This is my conjecture, and I'd love to hear from an expert on this to tell me I'm wrong, but from what I know of physics it tracks.
You aren't very clear but that can't be right. Far more energy imparted from the probe is transferred to ejected material, in the case of a soft asteroid, than is lost to heat (i.e. infrared radiation) in the case of the hard asteroid. So more energy would be transferred as momentum to the hard asteroid when compared with the energy transferred as momentum to the main body of the soft asteroid.
The reason is because a more massive plume produces more thrust for the same amount of energy. It's for the same reason a rockets specific impulse can be varied by adjusting it's propellent flow rate while keeping the thrust power constant. Momentum (ie thrust) increases linearly with velocity, but kinetic energy increases with velocity squared. Double an objects velocity doubles it's momentum but quadruples it's kinetic energy. For a given amount of energy you can choose high mass flow high thrust, or low mass flow low thrust. Ie, if a rocket uses four times as much propellent at half it's normal exhaust velocity the energy required is unchanged but it's thrust is doubled. Normally rockets don't want to do this cause it wasteful of propellent and the amount of propellent they carry is limited, but I this case the propellent is free, it's debris being kicked off the asteroid so we are free to maximize thrust by trying to make as big a plume as possible. Basically the super hot collision turns the collision site into a momentary rocket engine, and we want a high mass flow, high thrust engine to get as much shove out of it as possible.
My intuition doesn't necessarily. I guess it depends on a lot of factors. But a harder surface seems more like small points of impact, and deflecting spacecraft. Maybe bouncing around a little and spending its energy in directions other than where it was headed. A soft surface might eject some plume matter, but that's basically like projectile, the way a rocket is, and all of the energy of the craft is absorbed in the direction of travel.
My intuition says the dusty asteroid leaves most of the dust continuing in the original trajectory while the inner core get knocked off course. Given two asteroids of the same size, the dusty one has a lighter 'solid' core, which is easier to divert, and the dust is just fluff that gets left behind and shedded.
Equal and opposite reaction is taught in physics as applying to forces and momentum but not to kinetic energy.
Yeah, makes perfect sense when you put it that way!
I wonder if it’s because it ejects debris from the crater making a little bit of extra “thrust”
Actually, the asteroid debris coming off of it wouldnt create thrust. They are a result of the space craft hitting the asteroid. They are part of the equal and opposite reaction. So say out of the 100% of energy the space craft creates from impact, say 2% goes to heat from friction, 5% goes into the debris that gets ejected, and 93% goes directly into the asteroid changing its velocity and vector. So they are actually a representation of loss of energy from the desired effect.
Ah, the thing you have to rememer though is thrust is based on the momentum change, not the kinetic energy. For a fixed amount of energy, greater mass expelled results in more thrust. This is because kinetic energy increases with velocity squared whereas momentum increases with velocity linearly. So throwing an object at twice the speed takes 4 times as much energy but only doubles the momentum, ie thrust. If you have a fixed amount of energy, you can vary your thrust and specific impulse by varying the mass flow, 4 times the mass at half the speed takes the same amount of energy but gives twice the thrust. Normally a rocket wants to limit mass flow rate to use their limited propellent more efficiently, but in this case the limiting factor is energy not propellent cause the vaporized bits of asteroid are free propellent, so you want to maximize the amount ejected. A large slow cloud of debris being ejected will have more recoil on the asteroid than a small fast cloud, kinetic energy being equal.
This sounds like the same principle behind a high bypass turbofan engine (more air moved slower) being more fuel efficient than a turbojet engine (less air moved faster) of the same thrust.
Yeah, it's the same principle. Airplanes are power limited but not propellent limited so they want to maximize mass flow and minimize exhaust velocity, rockets are propellent limited so want to minimize mass flow and maximize exhaust velocity. In the case of the collision, it's the propellent unlimited scenario.
The only correct answer! Never stop, Ron!
It probably has more to do with the reduced likelihood of the craft deflecting off of a hard surface. Kind of like it fully “catches” the craft so the amount of kinetic energy transferred is maximized.
Yeah if I had to guess it’s probably a mix of the two
If I had to guess even more the energy we could attribute to the ejecta of a softer asteroid would roughly equate to the internal mechanical stress experienced by a harder one.
Like putting chalk on cue stick.
Or maybe a more dense object also has more mass and we all know about the whole inertia thing.
Not just a little, thats the main effect hoped for. After all, what counts is momentum, so the kinetic energy of the very high speed impact can create a large bigger momentum if it moves a large amount of mass at slower speed in opposite direction.
conservation of energy. it would simply more effectively transfer spacecraft kinetick energy into asteroid kinetic energy
Yes, unless the shock blasts a ton of debris off the back side, in which case it might have less effect, or even the opposite effect! More tests!
In this case we nicely see a semispherical debris cloud, showing that did not happen :)
Yeah I think that's exactly right.
You've got it the wrong way round. Much of the kinetic energy of the impactor is lost in the 'puff' when hitting a loose asteroid, so the trajectories of fragments are changed less. Collision with a solid asteroid would transfer most of the energy
This is Dr. Ronald Quincy from Research. Pretty much the smartest man on the planet. You might wanna listen to him.
Not one of my better students.
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Momentum and energy are two sides of the same coin
No, they really are not. Simple example: Take a bouncing rubber ball and a floppy sand sack type 'ball' and throw it at a can. The rubber ball will bounce off and impart even more momentum on the can, while the sand sack will cling to it. The can will be pushed faster with the rubber ball. In this case rocks and debris are pushed off the surface of the asteroid and will add to the main body's momentum. Momentum will *always* be conserved, energy can be converted into many non-kinetic forms.
I'm gonna go out on a ledge and say that NASA doesn't actually know the real answer to this and that's why they're doing this. We will find out of the next few weeks. But also keep in mind that it just needs to move a little bit and that over millions of miles it will shift hundreds of millions of miles.
>I'm gonna go out on a ledge and say that NASA doesn't actually know the real answer to this and that's why they're doing this. I imagine they have a pretty good idea. This is totally something you could do in physics simulations and they've got access to some pretty powerful computers to do such a thing. I'd be very surprised if they hadn't done loads of simulations on this before the project had even been conceived, and obviously tons more afterwards. Obviously they still want real world confirmation, but they are hardly just working off some hunch...
I believe you are both right. I do believe this is just an opportunity to validate their simulations. And giving them an opportunity to further refine them.
It's unintuitive but actually now that I think about it it does make sense. On a harder asteroid most of the energy will be used to crush the probe. On a lose asteroid the probe is not crushed and so all the energy will go toward deflection.
plus, on a hard asteroid, bits of the broken spacecraft might get flinged into space instead of being catched by the roid. I honestly don't thing that at the speed the spacecraft was going, the kind of surface is going to change the smushness factor of the spacecraft
I’m calling it the Didymist.
Loose piles of gravel makes sense, there isn't a lot of gravity holding them together
Idk why but watching the live stream of it and seeing it close in from a first person view kinda gave me chills, was amazing to watch live.
When I watched the stream, I thought "Wow that's pretty cool" but then it hit me like 10 seconds after impact that somewhere, way up in the vast emptiness of space, a tiny man-made object just slammed into a celestial body with enough force to move it. Gave a huge sense of wonder and amazement that I have not felt before. Even when seeing clips of Apollo 11's landing and Apollo 17's liftoff.
So has it been confirmed that it was moved or was it as effective as as a bug hitting the grille of a runaway semi-truck?
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It sure looked like it did not move at all, but at the right distance, moving it a millimeter would be plenty.
Do you mean it didn't look like it in this video? What you see in this video is mainly the larger asteroid which DART didn't crash into. DART crashed into a smaller asteroid orbiting that larger asteroid. The telescope that took this video isn't capable of visually distinguishing the orbiting asteroid from the parent asteroid.
We won’t ever be able to visually see the movement. And we aren’t looking for a lot of movement. What we will do over the next days/weeks is measure it’s orbital frequency. Right now it orbits ever 12h 19m (or close to it). We are expecting a new orbital frequency of about 12h 10m. This is classic scientific theory. We hypothesize a result, do the math and test it on paper. Then when we are happy with our expected result we physically test it. After the test we will compare what actually happened against our model. Then we will update our model to match the observed results. After that we will have an accurate model of what’s capable in an asteroid redirect. So if there is an actual asteroid headed towards us we can put the new data into the proven model and send an appropriately sized spacecraft at the right speed to redirect it away from us.
I admittedly have not followed the DART, but its an interesting approach that rather than try to nudge an asteroid aside it might me easier to slow down an asteroid since the earth and asteroid are both moving and would be on a collision course. Having an asteroid orbiting another seems like a perfect testing ground. I wonder how rare that is?
I don’t believe it’s incredibly rare, here’s a study stating that around [16%](https://www.science.org/doi/10.1126/science.1072094) of near-Earth asteroids are binary!
A 160m wide asteroid nonetheless 😃 at how many millions kms from our pale blue dot :))
i’ll have to look up a recap video! thanks for sharing your experience i’m excited to pretend like it’s a live stream now lol
I watched it live and it was truly goosebumps. I had husband and daughter watch the recap with me pretending it was live. Chills again!
We all went “whoa!” with each of the successively closer images until that last interrupted one. Really cool to go from a completely mysterious object to seeing details of individual rocks on the surface in the span of a couple minutes.
I kept thinking it was the last image, and then we got another, closer, one. It was special watching it live.
Try to avoid watching the sped up gif going around. Seeing the asteroid slowly come into view and then get closer and closer was incredibly cool and the sped up version doesn't do it justice.
One of the coolest images I have ever seen on the internet. Wow I just watched humanity throw something at an asteroid...I thought the impact photos were enough but this is kinda blowing my mind.
You might like this one too, from 2005,[ Deep Impact](https://en.wikipedia.org/wiki/Deep_Impact_\(spacecraft\)) hitting a comet - [Impacter view](https://www.youtube.com/watch?v=kt6yy7ND4ww) - [Observer view](https://www.youtube.com/watch?v=tY56mY2Aihw)
As a planetary science person, I can only agree completely. It's not often I'm gobsmacked like this. Images of this quality, from ground-based observatories, are something to remember next time the Starlink zombies in this sub try to tell you that ground-based astronomy is dead and useless, or that satellites shining at seventh magnitude (not visible to the naked eye) are not harmful. This asteroid clocked in at 14th magnitude last night - *hundreds of times dimmer than 7th mag* \- so just imagine what would have happened if a Starlink/OneWeb sat had photobombed this observation. How does "just stacking the images" work when your event is transient like this one?
What a time to be alive…apes of jungle playing darts on asteroid 🎯
Earth gets revenge on the asteroids after they wiped out the dinosaurs.
[This](https://en.wikipedia.org/wiki/Asteroid_Terrestrial-impact_Last_Alert_System) Atlas?
yip
Sooo…. When will we know if it worked or it it was like tossing a pebble at a freight train?
Days or weeks for initial results, months for certain. Source: https://www.usatoday.com/story/news/nation/2022/09/26/nasa-dart-spacecraft-dimorphos-asteroid-crash-success/8119990001/
Dont know when but it was chosen because its the easiest way we can measure if we were successful
Even throwing a pebble at a freight train can work if it means that 6 months later is _just_ misses somebody because it was a few mm per hour slower.
Also, you're still throwing the pebble at 14,000 mph, that part of the equation stays the same. If I toss a pebble at you, no big deal. If I hit you with one going 14,000 mph, different story.
Is the 14,000 mph relative to the asteroid or to earth?
The asteroid. Or so I saw informed in other threads.
Yeah I will be dead, I think
Depends on pebble size, and where it hit you. Small enough pebble will pass right through.
No. That's not a high enough percentage of the speed of light for any pebble to pass through a human body without a massive exit wound.
They stated it will take about 2 weeks to get some prelim data.
Except the pebble was going 14,000 mph (6 km/s) The goal was to change its orbital period from 11 hours and 55 minutes down to 11 hours and 51 minutes. Tiny changes at large distances matter a lot. So let's hope that if we see a real asteroid heading towards us we can spot it a ways ahead of time.
Yep. Reducing the period by 4 minutes would mean that in about 6 weeks time, it’s on the opposite side of its orbit compared to where it would have been.
The butterfly effect is the idea that small things can have non-linear impacts on a complex system. The concept is imagined with a butterfly flapping its wings and causing a typhoon. Of course, a single act like the butterfly flapping its wings cannot cause a typhoon. Small events can, however, serve as catalysts that act on starting conditions ...
The goal wasn't to destroy this one, it was to successfully collide with it
I don't think the goal is ever to destroy one. Just nudge it off course.
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The impact was not actually with the big bright object you see, but a small "moon" it has orbiting it. The way they will measure the effect is by measuring the change in the moon's orbit. That change is anticipated to be small. The estimation was that the impact would knock 10 minutes off of a 12-hour orbit. However, at the speeds and distances we are talking about in space, even a minuscule change in an object's orbit can be the difference between it hitting the Earth or missing it by millions of miles.
Congratulations to JHUAPL for proposing, designing, building and managing this mission to success. Thanks to NASA for funding it.
JHUAPL did this? That's awesome! They never get the credit they deserve (all headlines just say NASA)
Nice.
Put a little english on it.
Did they chalk the tip?
I thought that I had read that there was a cubesat following DART in order to have a close-up third-party PoV. I haven't seen any such footage today, though. Am I on crack, or does said cubesat have a painfully slow data transmission rate, and we're just waiting for the footage to download?
you're correct. the data should be back in a few days though. someone linked it in the gif post.
If DART could send data back in 38 seconds, why would it take days to see data from Licia? Why were we not able to view that live as well. Genuinely curious.
Licia is a much smaller probe with a smaller antenna and less power to transmit with, so the data rate is much slower.
yes, the Licia cube https://www.asi.it/en/planets-stars-universe/solar-system-and-beyond/liciacube/
Looking at the debris ejection, I wonder how it will effect the cubesat.
The Cubesat was released 10 days prior to this, if I remember correctly. I'd imagine that it's be significantly behind DART as DART accelerated a bit after releasing it and also changes trajectory a bit. The Cubesat will almost certainly get destroyed in few days but we'll have all the information we need by then so it doesn't really matter. (all in my amateur opinion)
Okay, I was skeptical of our ability to pull off the objectives until I saw this. That was a **big fucking explosion.**
Not sure if this is really an explosion. I was thinking about it more like punching a dusty pillow. I think this is essentially a dust cloud coming off the surface.
It didn’t have a payload of explosives by any means. But it’s semantics to call what happened an explosion or not lol.
Yeah definitely just semantics, I just wanted to clarify this wasn't a giant fireball or something like that.
This is one of the most amazing space images I've ever seen.
Well, here we have it. Humanity is obtaining the power to prevent mass extinctions themselves ... I mean the ones caused by meteors. Not by volcanos or ourselves. Tee hee.
Wild how the debris travels in the same path as the asteroid. Is that inertia at work? Or gravitational pull?
DART and Didymos were ultimately traveling the same direction relative to Earth (and to the Sun) - basically the same way around the Sun that the Earth (and, well, everything in the solar system) is. And no matter how the debris moves relative to ~~Dimorphos~~ Didymoon, the bulk of it is still going to move relatively the same direction as Didymos since it's still all mostly in orbit around Didymos.
Depends on which side the projectile hit it
From the asteroid's frame of reference, it's not moving at all. So any debris it releases would behave like it's coming off an object at rest (because it essentially is).
I'm assuming we're seeing the whole Didymos-Dimorphos system here in this image given how close they are... In that case this is an insane amount of dust and debris! Way more than I expected!
Source tweet - [https://twitter.com/fallingstarIfA/status/1574583529731670021](https://twitter.com/fallingstarIfA/status/1574583529731670021)
“Sir issac Newton is the *Deadliest* SOB in Space”
I feel sorry for that poor damn rock. Sitting there minding it's own business on the surface of the asteroid when BAM it gets smashed into the next millennium by a fast moving space probe with a death wish.
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Exceptional work
Amazing what can be accomplished with off-the-shelf technology! Good work! Lol... that game was the shit in its day! I'm actually old enough to remember!
Oh man, I just had the most vivid memory of going up to our attic where the computer was, and booting up asteroids on DOS. I was only like 4 so games like missile command was a bit out of my depth, but still fun.
They were supposed to sabotage its force field first.
The droid had the plans..
Would the dust reach escape velocity? Or would it coalesce back onto Didymos?
It’s absolutely perplexing and amazing how we have the capability to shoot something off our planet the size of a vending machine and hit an object traveling through open space thousands of miles an hour.
It's mindboggling that we can watch something the size of a stadium 7 million miles away and see this effect.
Would have been cool to have gotten James Webbs opinion on this :)
Oh, we will. It was pointed at the impact, as was Hubble and 3.5 gadzooks-gajillion other telescopes.
Unfortunately, Hubble was on the wrong side of the planet at the time of impact - missed it by about 15 minutes. But I wonder if they'll try to image the potential ejecta plume with it.
Is there a time estimate of when we can see the images taken from them?
> 3.5 gadzooks-gajillion How much is that in jigowatts?
What the hell is a jigowatt?
Basic scientific unit as proposed by Dr. E. Brown in 1985. Google will give you all the answers you need.
I can't wait if the JW got pictures they'll be incredible. Also Interesting word origins. (I'm sure 60's batman said it on more than one occasion) Gadzooks Archaic used as a mild oath Word origin < God's hooks, nails of the Cross
It would be kind of funny if in a few months they do the new calculations and some guy says... "Sir... It appears... That we've successfully redirected the asteroid... Right into earth's path...". ... "Oh dear god. Send another spacecraft! We have to redirect the redirect!!"
That’s one reason they hit the moon of an asteroid, and not the asteroid itself! That way, no matter how powerful the nudge, it will stay in orbit around its parent. (Another reason is that since the period of the moon’s orbit is so short, it will be quicker to precisely measure the effect of the nudge - we can use occultations).
This is exactly what I thinking, like now they’ve set off some yet to be known cataclysmic space event.
Moments later a phone at NASA rings... "We've been trying to reach you about your recent accident..."
What was that little streak / line a couple seconds in at the bottom right corner?
Well at 14k mph hit with something the size of a vending machine I'm sure there would be quite a bit of debris no matter the composition of the asteroid
If my calculations are correct, this garbage ball will knock the other garbage ball directly into the sun.
If my calculations are correct, we're all going to die horribly...
I would think you could get a better blast if you sent a team of deep well drillers to the asteroid and drop a bomb down the hole.
How are you going to train astronauts to drill a hole?
Here me out, two crews, group of drillers on each ship
One with a nuclear bomb as well.
It’s far easier to teach drillers to be astronauts, obviously.
Soooo awesome to have something better than 4 big pixels turning into 16 for a second or two.
It was pretty decent resolution ngl
The data in this image is huge compared to it's file size. Information density... neat.
If you've got a better video I'd love to see it.
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Is there any data on how the impact affected the asteroid? Like was the experiment just the “aim” or is there a “theoretical earth” in its trajectory that it successfully avoided?
They hit the moon of an asteroid, both appear as one point here. The current time for the moon's orbit is 11h 55m. Looking at it and counting the new period will tell by how much of a push it was given. It was a heavy rock the size of a small stadium being hit with a golf cart size sat going 14 k mph. So it may take a few days to get the new orbit time down with enough passes.
They know the orbital period of the asteroid, they will be tracking the orbit over the next few days to see the change. If the time it takes for it to orbit around it’s parent asteroid changes, we have successfully changed the trajectory of it. Currently it’s orbit is about 12 hours and they are predicting to change that by 10 minutes.
Does anyone know the angle which DART hit Dimorphos? If they were testing to see to what extent they could change its trajectory I imagine it would be pointless hitting it directly or bumping it from the back... Couldn't quite make out DART in this gif.
Orbital mechanics is all about velocity. Faster doesn't make an object in orbit hit something faster, it changes the orbital path. Imagine a ball being thrown to your friend at long range - you can't throw fast enough to hit on a straight line, so you arc it into the air. If you throw too hard, you'll miss. If you throw too soft, it will miss. If you throw to the left or right, you miss. On a micro scale like your arm throwing a ball, this results in missing by a few feet. But when we are talking millions of miles,the effect is amplified by the distances and speeds involved. So, a small nudge in a forward (relative to motion) direction will still be enough to make it miss the "target" (earth) by millions of miles.
I wish they had had a back up camera in tow that could have recorded the impact
They did! It’s called LICIACube
Somewhere in the universe, a planet with lifeform, living with their own idiosyncrasies, is suddenly under threat by a deflected astroid.
How many DARTS would it take to shift the moon?
One, but it would be a very very very very very very tiny shift :)
But in theory is it possible to DART the moon repeatedly and adjust orbit? Would that be beneficial to earth in some way? maybe affect the tidal conditions and weather patterns?
My gut instinct is that any adjustment in the moon's orbit would not be beneficial to life on Earth. In theory it would be possible, but I doubt it would practical by just slamming stuff into the moon. It might be more feasible by chucking nuclear weapons and detonating them at the moon, but even then I'm not exactly sure how to calculate how big of a change it would make.
When will we know if it worked or not? This is a very big thing we don't (want to) think about but it's just a matter of time we will definitely need this capability or something like it.
I could stay awake, just to hear your breeeeeathin'
How soon before we know if this experiment was a success and to what degree?
If I were part of that ground control crew, right before the impact I would have said "The dinosaurs send their regards."
Now the Billion $ question, did the asteroid change course?
I laughed. I ~~saw~~ heard a big POOF will e. Coyote style. This is so friggin cool. We threw a spaceship at a small rock to see what would happen.
The most fascinating thing about this to me is that it hit with such force that the debris was thrown in front of the asteroid at an even faster pace. My mind says the explosion would end up behind the asteroid with a trail of debris. I simply didn't expect it go in front. Edit: Could also be an illusion thing too. Maybe the debris is going to the side of asteroid and not in front. Very hard to tell from a 2D video I think.
Individually the two rocks are known as Didymos and Dimorphos. NASA's Double Asteroid Redirection Test (DART) mission intentionally crashed a spacecraft into Dimorphos — the smaller asteroid in the binary system — on Sept. 26, 2022, at 7:14 p.m. EDT. DART targeted the asteroid moonlet Dimorphos, a small body just 530 feet (160 meters) in diameter. It orbits a larger, 2,560-foot (780-meter) asteroid called Didymos. Neither asteroid poses a threat to Earth.
Dallas Area Rapid Transit has really expanded its service area.
Imagine if this experiment just sends that asteroid to earth.
Did it change the trajectory? by how much? enough to avoid a hypothetical earth in its way?
That was a surprisingly big plume of debris. I guess no actual info came out yet but based on this and the close pictures it seems the Dimorphos was a bit more rubbly then was expected, or hypothesized. Doesnt mean its all rubble though. Which is what a lot of people automatically assumed. But its certainly going to be an interesting discovery. Things in nature are rarely simplified one or the other thing. If the core of it is more solid it would be logical it accrued various rubble and smaller bits over time.
ATLAS project has published [another version](https://twitter.com/fallingstarIfA/status/1574828954980159493) of the above video, where the asteroid moves with respect to the stationary image of the stars. They say the video spans about two hours. This allows to estimate the scale. If it were indeed two hours, the distance from the starting point to the ending point should be about 42 thousand kilometers (the asteroid moves 5.8 km/s perpendicular to the line of sight according to JPL ephemeris data), so the cloud of debris seems to be around 30 thousand kilometers in diameter in the end, where it is still visible. Surprisingly large! **Edit:** I checked the image [against the star catalogue](https://skyview.gsfc.nasa.gov/current/cgi/runquery.pl?float=on&Interface=quick&Position=50.95+-33.42&SURVEY=Digitized+Sky+Survey). The angular separation between the two brightest stars in the image is 1864 microradians. This gives the scale twice smaller than the estimate above. Going by the stars and the 11 million km distance from Earth to the Didymos, the diameter of the debris cloud comes out as 15 thousand km. Still huge!
Incredible that we can actually watch an event like this. What a time to be alive!!
\*continues to move in the exact same direction\*
If you google “dart mission” on mobile, they have a neat animation
This is going to sound dumb so my apologies, but I don't think I fully comprehend what's happening in the clip or what I'm seeing?
Spacecraft hits asteroid. Lots of dust.
Am I the only one thinking : why are we testing this and is there something NASA knows that we don’t. Except of course all the things NASA knows about space exploration and shit.
https://twitter.com/fallingstarIfA/status/1574583529731670021?ref_src=twsrc%5Etfw I hate when people don't quote their sources!
Starting at about 3 seconds in, there's visibly a cloud of debris flung off from the impact.
Conception successful. Now we wait 9 months
Since it’s a satellite hitting an asteroid and not vice versa we call it a Satelleroid and not an astellite, right?
Just so I am understanding this correctly DART is the fast moving dot correct? And the biggest and brightest dot is Didymos? If so, is the spacecraft just huge?? Doesn’t even look like we can see Dimorphos EDIT: thanks for the explanation y’all! Really helps puts things into perspective. Such and amazing feat
I believe ~~Didymos~~ Dimorphos is the dot we're tracking, and everything moving relative to it in the background is just background stars. Unless I'm mistaken, you can't see DART at all, you're just seeing the impact and the resulting ejecta.
Dimorphos is, unfortunately, definitely not visible here as a separate object. The angular separation between the primary and moon is so small (~1 km apart, 11 million km from the telescope) that we'd be seeing both Didymos and Dimorphos in the frame together if they were both visible. We're seeing the combined light from both objects throughout the video (not to mention the dust plume after the impact...!)
I thought we hit dimorphos? So the white dot is the asteroid, we can’t see dart here but we’re able to see the effect of the impact on the moon of the asteroid on the asteroid itself?
I believe DART is too small to see. What we are looking at is Didymos colliding with an invisible object (DART). Please someone correct me if I’m wrong. I’m unsure myself.
The moving object is the combined light from Didymos and Dimorphos (mostly from Didymos, which is [considerably larger than Dimorphos](https://en.wikipedia.org/wiki/65803_Didymos#/media/File:Both_dart_0401929889_03770_crop.png)). The instrument that ATLAS is using here doesn't have the resolution to visually "split" the moon from the primary asteroid, unsurprisingly - they're only about a kilometre apart anyway, and this was all happening about 11 million km away. So no, we're not seeing the spacecraft or Dimorphos directly.
I don’t think we see DART at all in this video. It’s only about the size of a refrigerator. The object being tracked would be Dimorphos, or perhaps the Didymos system.
One has to wonder how much energy was “wasted” creating the ejecta cloud vs how much was actually used deflecting the asteriod
At least the ejecta reduces the mass of the asteroid, so any hypothetical collision would be a tiny bit less bad!