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NASA predicts asteroid to make one of closest approaches to Earth ever recorded
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Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#72When I was about 10 years old 1983 (+/- 2 years) I was 'camping' in my backyard with a friend. While we were running around in the dark we saw an asteroid bounce off the atmosphere and either enter below my visual horizon or pass by the earth. It was about the size golfball/chicken egg held at arms length. I was facing East-South-East (approximately). It was a bright red, and I could see impact craters on the surface…
A golf ball is around 4cm, and an arm's length is around 70cm. To be the same apparent size, it would have to maintain that same ratio. The atmosphere is like 50-100km thick (highest weather balloon flight was >50km) so you would have to be seeing it at a further distance than that. So your asteroid would have to be at least several kilometers across. That approaching dino-killer size. You're definitely misrememberin…
It's not impossible. How closely were we tracking 3 km objects in 1983?
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#73I wish they publicised error bars on these approach distances. What's the equation to calculate if such object given its mass, velocity, etc would get pulled into Earth orbit or collision or just fly past?
The equation is: if it isn't already in orbit, and it doesn't hit the atmosphere, then it flies past. For an incoming object to start orbiting earth, it has to decelerate through active propulsion or aerobraking or something like that.
Sounds like a nice heuristic but I don’t think that covers every case—and it’s not an equation. Sorry, wrong answer!!
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#74Notice that this was spotted by an amateur only 2 weeks before closest approach. Why was it not found by the larger installations? One problem I like to repeat at times like this, is that these hunts for near earth asteroids look for bright spots that move against the background stars. That's a nice way to find things nearby. But any object on a collision course with earth will not be moving against the background in…
> Dan : [the President asks about the size of the asteroid] it’s the size of Texas, Mr President.
> President : Dan, we didn't see this thing coming?
> Dan : Well, our object collison budget's a million dollars, that allows us to track about 3% of the sky, and beg'n your pardon sir, but it's a big-ass sky.
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#75Earlier quoted context omitted.
A golf ball is around 4cm, and an arm's length is around 70cm. To be the same apparent size, it would have to maintain that same ratio. The atmosphere is like 50-100km thick (highest weather balloon flight was >50km) so you would have to be seeing it at a further distance than that. So your asteroid would have to be at least several kilometers across. That approaching dino-killer size. You're definitely misrememberin…
It's not impossible. How closely were we tracking 3 km objects in 1983?
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Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#76Earlier quoted context omitted.
The equation is: if it isn't already in orbit, and it doesn't hit the atmosphere, then it flies past. For an incoming object to start orbiting earth, it has to decelerate through active propulsion or aerobraking or something like that.
Sounds like a nice heuristic but I don’t think that covers every case—and it’s not an equation. Sorry, wrong answer!!
It does cover every case though. The solution for the orbit of a mass in a 2-body problem is always an ellipse! (Or a parabola/hyperbola for an escape trajectory). You can find the derivation here [1], it's not too complicated.
There is no way for an asteroid and the earth to interact gravitationally to change the asteroid's orbit from what it was coming in. Non-gravitational interactions (like hitting the earth/atmosphere) can do it.
Also, over many interactions and a long time you can have orbital capture in many-body situations, but there is no general equation for this (look up 3 body problem). This is how you get objects accumulating at Lagrange points for example.
TLDR: The equation you're asking for does not exist. Sorry, wrong question!!
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#77Earlier quoted context omitted.
In between the extinction-level asteroids and the mostly harmless ones is a medium-size class of asteroids about the size of a football pitch. Those are the scary ones. They are small enough to be hard to spot, and there are enough of them that one of them hits earth every 10,000 years or so. They have not been a big deal in the past. They don't cause mass extinctions, but they are more than big enough to bring about…
This is an excellent way to do what-if scenarios https://neal.fun/asteroid-launcher/
Meh, I dropped one like GP mentioned in the north atlantic and other than mentioning the size of the Tsunami, all of the other factors assumed it was dropped within miles of land.
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#78Earlier quoted context omitted.
But with computers and sky tracking charts shouldn't it be trivial to find new spots in the sky without using parallax? Anything new should be pretty note worthy.
Not all asteroids are “bright” enough to be imaged from earth, the problem is the low albedo asteroids you cant see, thats why we need this: https://solarsystem.nasa.gov/missions/neo-surveyor/in-depth/
Right. If you can't see them, you can't see them. It's not a parallax problem.
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#79Earlier quoted context omitted.
Wouldn't they be throwing the rocks at the flashlight guy?
Well, to make the analogy work you'd be running circles around flashlight guy while they throw at him. Maybe you're in the crossfire, maybe not. But the other part that I think the original OP is sort of amazed at is that we're unable to detect these through some sort of automated system more accurately. It isn't fair to compare our space/vision capabilities to the eyesight of a person alone. Do we not have satellite…
You'll be horrified when you Google just how much of the sky we're able to observe at any one point using everything we've got online right now.
Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded
#80Earlier quoted context omitted.
A golf ball is around 4cm, and an arm's length is around 70cm. To be the same apparent size, it would have to maintain that same ratio. The atmosphere is like 50-100km thick (highest weather balloon flight was >50km) so you would have to be seeing it at a further distance than that. So your asteroid would have to be at least several kilometers across. That approaching dino-killer size. You're definitely misrememberin…
It's not impossible. How closely were we tracking 3 km objects in 1983?
The US and USSR were looking very closely for much smaller objects leaving and entering the atmosphere.