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NASA predicts asteroid to make one of closest approaches to Earth ever recorded

jpl.nasa.gov

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Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#51

Post by rpledge »

UI_at_80x24 wrote: post #49

When 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…

There's no way you saw any impact craters on an asteroid naked eye. You have a false memory

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#52

Post by pixl97 »

TheCapn wrote: post #36
jeffbee wrote: post #29

Earlier 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…

>canning with radio/laser/something-else

R-squared is not your friend. This would take a massive amount of energy.

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#53

Post by mc32 »

sand500 wrote: post #47
phkahler wrote: post #33

Notice 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…

Is there no parallax as the Earth moves around the Sun? Are these asteroids in some crazy hyperbolic orbit coming in straight from outside the solar system?

No, it looks like this asteroid had a similar trajectory as Earth around the sun, but after the encounter its path will be altered significantly.

"Before encountering Earth, the asteroid’s orbit around the Sun was roughly circular, approximating Earth’s orbit, taking 359 days to complete its orbit about the Sun. After its encounter, the asteroid’s orbit will be more elongated, moving it out to about halfway between Earth’s and Mars’ orbits at its farthest point from the Sun. The asteroid will then complete one orbit every 425 days."

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#54

Post by guerrilla »

derstander wrote: post #27
guerrilla wrote: post #18

Earlier quoted context omitted.

> there are cyclical natural catastrophes That sounds very made up.

I don’t really follow astrophysics, but there were hypotheses that the motion of the solar system through the galactic plane, which has a periodicity, would induce impact events. A cursory search suggests that recent analyses of crater data may not support those hypotheses. Here’s a link to a 2011 paper suggesting as much. So the notion was certainly a reasonable one even if not ultimately true. https://academic.oup.…

It's way beyond a three body problem though, so it's chaotic even if it's recurrent... even trying to retrodict precise correlations in celestial events 10k years ago is difficult, doing this would be way harder. The only thing I can think of on that scale that's somewhat predictable within meaningful margins is Milankovich cycles. Cool paper though. Thanks for sharing.

(And to note: I can't edit my reply now but I read 'there' as 'these'. Obviously there are other (somewhat) cyclic natural catastrophes especially on shorter timescales.)

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#55

Post by pocketstar »

bgirard wrote: post #50
phkahler wrote: post #33

Notice 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…

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/

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#56

Post by lamacase »

UI_at_80x24 wrote: post #49

When 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 misremembering some part of this.

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#58

Post by mturmon »

phkahler wrote: post #33

Notice 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…

Congress mandated that NASA construct a surveillance capability for relatively-large NEOs (larger than the ones in OP), so the detection problem has been well-studied. A little googling will turn them up, but here's what I remember:

- Detection in optical by ground-based telescopes is a good technique. You need several exposures and good spot-tracking. Because of the relatively short time-base, you also need good follow-up or else the NEO diverges from your estimated orbit and is lost again!

- The parallax issue you mention comes up more regarding orbit determination than detection per se. (I.e., you need more than just detection to do anything useful.) One link going deep on the relationship of parallax to good orbits: [1]

- There are a bunch of such optical surveys, e.g. Pan-STARRs [3].

- But ground-based telescopes rely on reflected light, and so NEOs coming from certain regions (e.g., within Earth's orbit, but it's worse than that) don't have much reflected sunlight so are hard to detect optically.

- So, IR telescopes can be used, but you have to go above the atmosphere. See, NEOSurveyor [2]. IR is based on the infrared "glow" of a NEO against the background, and so it does not rely on reflected light. So IR telescopes get around many of the geometric limitations of optical.

- What about radar? It's very useful for follow-up orbit determination, but not so good for surveys, because the radar energy diffuses so much. Crudely, if the NEO is R away, you get a 1/R^2 on the way out, and a 1/R^2 on the way back. It's more complicated than that, but this is the reason that radar has limitations for this problem.

[1] https://iopscience.iop.org/article/10.1088/1538-3873/ac43ca/...

[2] https://www.jpl.nasa.gov/missions/near-earth-object-surveyor

[3] http://legacy.ifa.hawaii.edu/research/Pan-STARRS.shtml

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#59

Post by LatteLazy »

>There is no risk of the asteroid impacting Earth. But even if it did, this small asteroid – estimated to be 11.5 to 28 feet (3.5 to 8.5 meters) across – would turn into a fireball and largely disintegrate harmlessly in the atmosphere, with some of the bigger debris potentially falling as small meteorites.

Re: NASA predicts asteroid to make one of closest approaches to Earth ever recorded

#60

Post by lamacase »

graderjs wrote: post #17

I 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.

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