I'm having a weirdly difficult time finding some basic ELI5 answers.

  - What is the probability that this asteroid will hit us?
  - What is the time interval where that probability applies?
  - Do we have a probability distribution for where it might hit? I don't know anything about anything, but I assume we know what *general direction* it's coming from?
  - Do we have a probability distribution for the potential blast radius?

Here's a visualization of its orbit, Earth in green, object in teal: http://orbitsimulator.com/gravitySimulatorCloud/yr/gsim2023....

It passed about 9 hours ago.

> Closest approach time [...] t_max = 2023/08/15 12:22 TDB [...] Run started at 2023-08-14 23:51 UTC and ended at 2023-08-15 00:06 UTC

So this computation result became known after the closest approach would happen at the latest.

Looking at the asteroid I saw hitting us, 2023CX1 (known as Sar2667 before being designated), it says:

> Closest approach [...] t_max = 2023/02/13 03:22 TDB [...] Run started at 2023-02-13 11:47 UTC and ended at 2023-02-13 11:53 UTC

Again, hours after the impact actually occurred. And that's from the 7-observations page, there are 3 more pages with 28, 76, and 125 observations, all listed here: https://newton.spacedys.com/neodys2/NEOScan/index_past_imp.h...

The next one on the past impactors page has a 3 day delay between when it hit us and when its orbit was computed

What's the point of this?

I'm aware that it already passed its closest approach, but what does >3% even mean? 100% is >3%, but 3.000001% is >3% too. Was an impact certain at some point and the probability degraded to a bit above 3% over the course of the asteroid's trajectory? If so, I think I'd like to have a heads up when the probability is still closer to 100%, before it drops?

Is there an english / eli5 if you like, summary of what this means?

I gather that today or yesterday an asteroid ~400m along it's biggest dimension ultimately came within x km of earth, that was close enough there was a nontrivial chance it would hit us? And this is big enough to make a 30 mile crater? And we only found out it was coming a couple days ago? Sounds like a pretty big deal if that's accurate.

I don't really know how to read this page, but it looks like the time of closest approach has already passed -

> Closest approach time of impactors: t_min = 2023/08/14 04:48 TDB and t_max = 2023/08/15 12:22 TDB

If so then we're all good. Can the poster or anyone else chime in with background on this?

I plugged this into neal.fun/asteroid-launcher.

I'm not sure if I did it right (I used the 15.84 km/s as impact speed, picked 45 deg impact, and an iron asteroid). It's certainly serious - millions dead - especially if it hits Manhattan as neal.fun seems to invite you doing, but not world-ending.

Impact time is in the past. Mission accomplished, everyone!

Here are some more numbers:

https://www.projectpluto.com/neocp2/mpecs/ZTm0038.htm

In particular the MOID (Minimum Orbit Intersection Distance, the minimum distance between the orbit of the object and the Earth, in AU) is 0.0199 AU which is still 3 million km

From other comments in this thread, it seems this risk has passed, but was known three days ago?

Was any action taken at all? A 3% risk isn't small.

Oddly, I cannot find where on this page it says anything about the size of the asteroid in question. It's probably there somewhere, but I'm not seeing it somehow.

That's what I get for reading HN before going to sleep...

Looks pretty bad in this asteroid impact simulator: https://neal.fun/asteroid-launcher/

TDB is https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time ?

How long ago was it spotted. That's what I'm curious about, did we have any lead time?

Let's hope there are no 'dark companions' like with the Chelyabinsk meteor.

Looks like it is about the same size as 25143 Itokawa that the Hayabusa probe visited. That has a mass of 35 billion kg. The Burj Khalifa is 0.45 billion kg so that is about 80 Burj Khalifa's.

did this pass ~4000km from earth?

[1] MOID given as 0.0000296

https://newton.spacedys.com/neodys2/NEOScan/risk_page/ZTm003...

[2] AU to km https://www.google.com/search?q=au+to+kilomore&rlz=1C1GCEA_e...

Is it possible to estimate where the astroid is most likely to hit? I'm not sure how to interpret most of the info on that page.

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Pretty graphs of possible impact sites:

https://twitter.com/JoelSercel/status/1691549821629526219

there seems to be a second entity on the risk list (but less than 3 observations) https://newton.spacedys.com/neodys2/NEOScan/index_risk.html

Also both these entities are "lost" but not "high priority" https://newton.spacedys.com/neodys2/NEOScan/index_nspl.html

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Is this the highest probability assigned to such an object?

This is why numbers should always be bounded. Is this 3.3-3.5%?

Or 0-3.4%?

Or 0-6.8%?

Etc

Do we know how close it was?

> Closest approach time of impactors: t_min = 2023/08/14 04:48 TDB and t_max = 2023/08/15 12:22 TDB

If you can read this that means it hasn't hit you.

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Not threatening, mostly harmless.

I'm surprised Elon Musk didn't pick up on this a couple days ago and launch something at it.

The public is unanimously in favor of funding asteroid protection mechanisms and research. It's even higher support than the military.

Naturally what do we do with that money and goodwill instead? Yes! Let's build a massive space telescope which takes pictures that are only marginally better than the other multi-billion dollar space telescope!

Protect the Earth? Fuck that, don't ya know kid? She's toast anyway because the Sun will explode soon! Also get in loser, we're going to Mars!

I wonder how many people already used this https://neal.fun/asteroid-launcher/ to see what happens if it falls in moscow downtown