[HN Gopher] Asteroid ZTm0038 with a >3% impact probability
___________________________________________________________________
Asteroid ZTm0038 with a >3% impact probability
Author : isbn
Score : 175 points
Date : 2023-08-15 19:19 UTC (3 hours ago)
(HTM) web link (newton.spacedys.com)
(TXT) w3m dump (newton.spacedys.com)
| amiralul wrote:
| Do we know how close it was?
| fghorow wrote:
| According to a site [1] pointed to by another post in this
| page, the estimate for "Minimum Orbit Insertion Distance" was
| about 0.02 AU or about 3 million km (in round numbers).
|
| Luna's distance is roughly 384,000 km -- so call it 8 lunar
| orbital distances...
|
| (edited to add the link) [1]
| https://www.projectpluto.com/neocp2/mpecs/ZTm0038.htm
| radicaldreamer wrote:
| Is this the highest probability assigned to such an object?
| jacquesm wrote:
| That depends on the timescale. Over a long enough time it is
| 100%, for a human lifetime maybe one in a million or so.
| harwoodr wrote:
| Pretty graphs of possible impact sites:
|
| https://twitter.com/JoelSercel/status/1691549821629526219
| s5300 wrote:
| [dead]
| 23B1 wrote:
| This thread cracks me up.
|
| 1. Bungled headline
|
| 2. Useless visualization
|
| 3. A bunch of comments trying their best to ELI5
|
| 4. Links to twitter threads attempting to do the same
|
| 5. "3% of what?"
|
| 6. "Oh shit did we almost die? I still can't tell!"
|
| Maybe you'd disagree... but it sure seems to me that stuff like
| this is what journalists and the commentariat at large should be
| paying attention to as opposed to, I dunno, billionaire cage
| fights!
| [deleted]
| dang wrote:
| Instead of snarking and putting others down, which is against
| the site guidelines, why not explain something so we can all
| learn? If you know more than others, that's a much better way
| to show it.
|
| https://news.ycombinator.com/newsguidelines.html
| 23B1 wrote:
| Site guidelines also say "assume good faith". My comment is
| on how absurd the situation is, not a dig at any HN users.
| 1970-01-01 wrote:
| Indeed. We've got facts and numbers but lack an expert that can
| put them together in any meaningful way.
| xwdv wrote:
| Not threatening, mostly harmless.
| refulgentis wrote:
| How do you tell?
| [deleted]
| xwdv wrote:
| Only 400m in diameter.
| Tuna-Fish wrote:
| ... The Chelyabinsk meteor had ~20m of diameter.
|
| The impact energy of a 400m diameter asteroid is somewhere
| in the same ballpark as the deployed nuclear arsenal of the
| United States.
|
| Not extinction-level impact, but wherever it hit would
| definitely feel it.
| xwdv wrote:
| Yes some place _will_ feel it somehow, 70% chance it
| strikes an ocean and creates a tsunami.
|
| But the world will go on, people will shrug their
| shoulders and go on with life.
|
| If it was a 60 mile wide asteroid, now that would truly
| be the end.
| jacquesm wrote:
| This would wipe out an area equivalent to a mid sized
| country and would possibly have global effects. The
| threshold for that is somewhere between 250 meters and a
| kilometer but we _fortunately_ do not have any data to
| make that much more precise. You definitely wouldn 't
| shrug your shoulders and get on with life, it would be
| the most important event in your life assuming it didn't
| end. Depending on where it happened the economic impact
| of such an incident would destabilize the world economy
| for decades.
| [deleted]
| lijok wrote:
| Going at 55~ km/s
| lucb1e wrote:
| Or 8. The page isn't quite sure.
|
| Bad news for any life forms on its path either way, to be
| fair
| brink wrote:
| How much of that would burn up in the atmosphere if it did
| hit?
| throwanem wrote:
| The better question to ask is, how much energy would that
| transfer to the atmosphere on its way to dumping the rest
| into the planet proper?
| pcblues wrote:
| https://www.quora.com/Would-an-asteroid-
| measuring-400-metres...
|
| I googled your question :)
| hoten wrote:
| Quora is pretty much unreadable now. Is the main answer
| just chat gpt? That's how it seems from mobile view. The
| page is too noisy to navigate for me.
| NotYourLawyer wrote:
| Quora has been trash for awhile now.
| gs17 wrote:
| Yep, they've added a ChatGPT answer on top of all the
| human answers. Although in this case the human answer
| isn't really better, but it's the fault of the person who
| asked the question for being vague about the kind of
| speed they meant.
| kjs3 wrote:
| How could Quora suck worse? Rub a little AI on it.
| radicaldreamer wrote:
| Not sure why this happened but it went viral in India as
| a place to practice english for internet points or an
| online place to for Indians to do endless chit-chat,
| which is a lot more fun in person there than it is
| online!
| wheelerof4te wrote:
| A lot.
| jacquesm wrote:
| Not enough.
| vkou wrote:
| As a fraction of the overall asteroid, very little,
| thanks to the square-cube law.
| deepakg wrote:
| This video has comparisons of devastation that would be
| caused by different sizes (around 7:50 mark) of
| asteroids: https://www.youtube.com/watch?v=4Wrc4fHSCpw
| hoten wrote:
| So a 500m is roughly a couple thousand or ten thousand
| times more than a Hiroshima nuke?
| jacquesm wrote:
| More like 50,000 or so (back of the envelope).
| AbrahamParangi wrote:
| At 400m diameter we should expect an impact energy of ~3Gt,
| which would be one of the most energetic events in human
| history, if not the most.
|
| For a comparison, the Lake Toba eruption (which is suspected of
| causing homo sapiens to almost go extinct 76kya) is estimated
| to have been in the 1-2Gt range.
| charlieyu1 wrote:
| 400m diameter is certainly pretty bad if hit.
|
| And why is there no articles about it on Wikipedia yet?
| babelfish wrote:
| ChatGPT estimates about ~5Kt of damage to the affected area if
| it hit
| https://chat.openai.com/share/d69b4a6d-c113-4a78-a155-e843e9...
| groby_b wrote:
| ChatGPT also believes the moon is made out of green cheese.
|
| (Less snarky: It hallucinates an answer. It can't do math. Do
| not rely on ChatGPT for math. Or facts.)
| [deleted]
| jacquesm wrote:
| Based on even the slightest bit of checking you could see
| that that number is utter bullshit, 5Kt is _nothing_ at all
| like the impact of an asteroid of this size.
|
| https://en.wikipedia.org/wiki/Chelyabinsk_meteor
|
| Was 100 times as much and was only an 18 meter asteroid.
| AbrahamParangi wrote:
| This seems like it's off by ~6 orders of magnitude
|
| (see https://en.wikipedia.org/wiki/Impact_event)
| AbrahamParangi wrote:
| Amusing addendum, in order for this asteroid to have a 5Kt
| impact energy it would need to be traveling at around 50
| mph as it impacts earth.
|
| A typical impact velocity would be something closer to
| 30,000 mph.
| gs17 wrote:
| I would recommend using a calculator designed by experts,
| like
| https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffectsMap/
| instead of ChatGPT. I get a low-end estimate of tens of
| megatons.
| songeater wrote:
| 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...
| fghorow wrote:
| Something weird is going on. This site [1] suggests the MOID
| was about 0.02 AU.
|
| [1] https://www.projectpluto.com/neocp2/mpecs/ZTm0038.htm
| amiralul wrote:
| Other source[1] says 0.0002 AU, still very close (about 40,000
| km).
|
| [1]: https://cneos.jpl.nasa.gov/scout/object/ZTm0038
| lucb1e wrote:
| This, as I understand it, being the closest approach to our
| _orbit_ , not our _atmosphere_ or so. To put this in
| perspective, the Earth is some 6.4 Mm in radius, so that 's
| 40-6.4 = 33.6 Mm above the surface.
| lucb1e wrote:
| MOID being minimum orbit intersection distance, for anyone else
| wondering. Sounded like someID (identifier) to me, was
| wondering why that value was given in AU
| pvg wrote:
| MOID is an id that is just that big. You wanted more id, you
| got MOID.
| FredPret wrote:
| 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.
| ortusdux wrote:
| I used the Earth Impact Effects Program calc w/ 90 deg impact,
| rock asteroid, and 15km/s.
|
| https://impact.ese.ic.ac.uk/cgi-bin/crater.cgi?dist=100&diam...
|
| 4 mile crater, 2300 MT of TNT equiv. so about 45 Tsar Bombas.
| H8crilA wrote:
| Where did you find the mass/size?
| ortusdux wrote:
| I had to guess without albedo data, but an H of 19.2 puts
| it in the 0.4 to 0.5 km range, so 400m could be on the
| conservative side. If it randomly has an albedo of 0.05, it
| could be as large as 0.96km
|
| https://cneos.jpl.nasa.gov/tools/ast_size_est.html
| [deleted]
| version_five wrote:
| 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.
| zardo wrote:
| That's just measure of uncertainty in out measurements, unless
| we're saying there was a ~3% chance someone would do an
| emergency asteroid redirection to make it hit.
| lucb1e wrote:
| > ~400m along it's biggest dimension
|
| Where did you find this information? I don't understand all the
| fields on the page, but don't see any number being 400 within
| an order of magnitude
| SoftTalker wrote:
| 400m in one dimension leaves a lot of room for variation.
| 400m x 1m x 1m is a lot less concerning than a 400m diameter
| sphere.
| lucb1e wrote:
| I wonder what the distribution is like; the most extreme
| length to height ratios we've seen for example. Not sure
| I've ever heard of something weirder than on the order of
| 2:1
| cafxx wrote:
| 'Oumuamua was closer to 8:1
| https://en.wikipedia.org/wiki/%CA%BBOumuamua
| postalrat wrote:
| 400x1x1 would be a pretty nasty spear that must have been
| made by someone.
| radicaldreamer wrote:
| It's the Spear of Longinus
| dougmwne wrote:
| That would sound like a kinetic bombardment weapon and that
| we were about to get rodded. My level of concern would be
| sky high!
| jacquesm wrote:
| Depending on how it is aimed... straight in that would be
| messy.
| almostnormal wrote:
| If it has the same density than earth, it wont pierce
| deeper than its length. If it is made of uranium a bit
| over twice that (assuming earth is made of iron).
| jacquesm wrote:
| I wonder if there have been any simulations of such an
| impact and what the worst case would look like for
| equivalent mass but different shapes and asteroid
| compositions.
| version_five wrote:
| That would be an interesting analysis to see, my guess is
| it wouldn't be that different than if it was a sphere of
| equivalent mass, and vs a 400m sphere would be
| 400/(4*pi*200^3/3) = .0012% the volume (and so kinetic
| energy), and it would not penetrate in a way that does
| specifically worse damage. Just guessing though.
|
| Edit: I confused radius and diameter in my calculation
| and revised it. I may have made other mistakes
| jacquesm wrote:
| That would highly depend on what the composition of the
| asteroid was and where it impacted. On a fault line? In
| the middle of an ocean, or a city?
|
| For sure the depth of penetration would be different for
| a rod shaped object of equivalent mass compared to a
| spheroid, the latter would penetrate much less deep.
| Angle of incidence would be a factor as well as
| (obviously) the speed of the impacting body. But if it
| impacted at a higher speed than that the ejecta could get
| out of the way it would cause an absolutely massive
| crater. As though you'd exploded an absolutely enormous
| nuclear bomb deep underground, but not so deep that the
| explosion would still reach the surface. That would
| probably be the worst case scenario for an impact like
| this.
| version_five wrote:
| Everything I wrote was from skimming the comments here. This
| is the 400m: https://news.ycombinator.com/item?id=37138510
|
| I was hoping someone more familiar with this stuff could
| write a definitive summary.
| jacquesm wrote:
| It's accurate and it could have been a pretty big deal but for
| now it isn't, unless there are very low magnitude companions to
| it that hit unexpectedly because they have not been observed at
| all. There is some precedent for that sort of thing.
| ConanRus wrote:
| [dead]
| lucb1e wrote:
| > 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?
| lijok wrote:
| Can you elaborate on the question you're asking?
| lucb1e wrote:
| Put differently: am I missing something if I say this website
| is similar in function to
| https://hasthelargehadroncolliderdestroyedtheworldyet.com ?
|
| At least in terms of a public service announcement; I
| understand it's interesting for science but not so much for
| linking "hey look there's an X% chance of
| impact....yesterday!" on news websites
| NyxWulf wrote:
| When I was taking physics at the University 20 years ago,
| one of my professors said that the closest we have ever
| come to predicting an asteroid impact was "whoa that was
| close" as it zipped by.
|
| Sounds like that's still state of the art.
| CafeRacer wrote:
| I wonder how many people already used this
| https://neal.fun/asteroid-launcher/ to see what happens if it
| falls in moscow downtown
| gdy wrote:
| [dead]
| [deleted]
| rurp wrote:
| 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.
| post_break wrote:
| How long ago was it spotted. That's what I'm curious about, did
| we have any lead time?
| mcint wrote:
| 3 days ago, it was first seen. About a dozen observations.
| F***, it's not fun that these pass with so little forewarning.
| ZTm0038* C2023 08 12.49542 06 32 33.23 +15 57 35.5
| 18.86rUNEOCPI41
|
| Is the first entry, and asterisk-marked, on
| https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038 at the
| bottom, in the Observations section.
|
| Unusual (new to me) format. Appears to me, first guess to read:
| [object] [yr] [m] [day.time-decimal] [position] [elevation-
| angle] [observatory]
|
| Likely oriented relative to the plane of the ecliptic, and
| absolute direction relative to Earth at time of observation.
| mcint wrote:
| Here's a visualization of its orbit, Earth in green, object
| in teal: http://orbitsimulator.com/gravitySimulatorCloud/yr/g
| sim2023....
| jacquesm wrote:
| Not to spoil your lunch or anything:
|
| https://www.youtube.com/watch?v=bU1QPtOZQZU
|
| Of course 500 Km is a big difference with 400 meters but to
| those near the point of impact it wouldn't matter and the
| global effects would still be beyond anything in our history.
|
| This is one interpretation of what this could look like:
|
| https://youtu.be/ZyyrfB8s5cY?t=152
| vkou wrote:
| The difference between the 500km asteroid impact in the
| video, and a 400m asteroid impact is the difference between
| a man jumping, and a man jumping to the moon.
| jacquesm wrote:
| Yes, it is the difference between a sterilization level
| event and one that is _probably_ survivable. But it would
| still be the most significant impact in all of recorded
| history and to get to a larger one you 'd have to go back
| a long, long time.
| sp332 wrote:
| According to
| https://www.projectpluto.com/neocp2/mpecs/ZTm0038.htm#elemen...
| the observations were taken a few days ago, August 12-13. I
| don't know when someone calculated the future trajectory and
| impact probability though.
| thatcherc wrote:
| 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?
| throwaway5729 wrote:
| I saw this tweet:
| https://twitter.com/ByronDrury/status/1691487518590402560?s=...
|
| linking to https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038
|
| It has some cool graphs that seem to show a lot of uncertainty
| in closest approach time
|
| [edited to fix second link]
| SkyPuncher wrote:
| I am not an expert, but my interpretation was the same as
| yours.
|
| TBD seems to be roughly UTC time. In which case, this passed by
| 8 hours ago.
| elchief wrote:
| TDB is https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time ?
| fghorow wrote:
| Which following the contained link to Terrestrial Time (TT)
| states that TBD is relativity corrected TT, which itself is
| about 30 +/- seconds from UTC -- something much more familiar
| to we groundhogs...
| [deleted]
| hughes wrote:
| Impact time is in the past. Mission accomplished, everyone!
| ortusdux wrote:
| Am I reading this data correctly?:
|
| https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038
|
| Because it looks like today is the most probable day of impact
| at 10%, but there is a good 25%+ chance it will impact sometime
| in the next two weeks.
| tophi wrote:
| Can't find any information on this anywhere else.
| EGreg wrote:
| I would also very much like to know what the consequences of
| an impact might be
| ortusdux wrote:
| This paper is an interesting read:
|
| https://www.sciencedirect.com/science/article/pii/S00945765
| 1...
|
| Not my area of expertise, but it sounds like a deep ocean
| impact would not be completely catastrophic.
|
| _With only ~1% of the asteroid kinetic energy being
| converted into tsunami waves and with the stronger decay
| with distance implies that moderate size asteroids (100-500
| m in diameter) striking the deep ocean basins off the
| continental shelves are not a significant overall
| hazard..._
|
| So like a 50% chance it wouldn't be that bad. Larger
| asteroids would vaporize enough ocean water to cause long
| lasting atmospheric affects.
|
| Otherwise, a land impact would be somewhere in the 1-100
| Tsar Bomba range energy wise.
| radicaldreamer wrote:
| If it hit land anywhere other than Siberia or the Sahara,
| it would be pretty bad!
| EGreg wrote:
| How bad is the question
| [deleted]
| nocoiner wrote:
| I must have put a decimal point in the wrong place or
| something. I always do that. I always mess up some mundane
| detail.
| czbond wrote:
| I did my part - go team
| arcticpeanuts wrote:
| 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?
| abathur wrote:
| The linked page indicates:
|
| Impact probability 0.034
|
| Edit: Not familiar with the site, but I get the sense that this
| probability reflects the latest run. The probability hopefully
| gets more accurate as observations rise?
|
| I couldn't readily figure out how to see the probability at
| each of the 8 observations for this one (perhaps this is the
| first run it's included in--all 8 observations predate this
| run?), but the page for actual impactors (https://newton.spaced
| ys.com/neodys2/NEOScan/index_past_imp.h...) at least implies
| that accuracy may improves with each (and then maybe flip to
| 0/100?)
| soneca wrote:
| I think it specifies that it's a 3.4% probability in the page.
|
| So it was just an odd choice of title by the poster.
| codetrotter wrote:
| From the page: Impact probability 0.034
|
| I guess OP decided to abbreviate to >3% instead of writing 3.4%
|
| Personally I would've written ~3%
| sp332 wrote:
| It was 3.4%
| https://newton.spacedys.com/neodys2/NEOScan/risk_page/ZTm003...
| If you're not logged in to Twitter, I don't think you can
| scroll from the linked tweet up to see the one this page was
| linked from, so I put it here.
| arcticpeanuts wrote:
| I think the link works just fine and I can see it's at 3.4%
| right now, but was mostly wondering why it's written as >3%
| in the title. Most likely it's meant as ~3% like other people
| suggested and I shouldn't be reading to much in it :) Thank
| you for taking the effort to write your comment.
| [deleted]
| arketyp wrote:
| Think of it as the most sensational number you can write
| without lying. So it's between 3% and 4%.
| macawfish wrote:
| Looks pretty bad in this asteroid impact simulator:
| https://neal.fun/asteroid-launcher/
| ArtWomb wrote:
| How accurate is this? I just feel implicitly that a 1mi
| asteroid would leave a creater bigger than 30mi wide upon
| direct max impact ;)
| tshaddox wrote:
| I also wouldn't expect an impact in rural Kansas to create a
| 2,500 foot tall tsunami.
| macawfish wrote:
| If you scroll you'll see that the fireball is much larger
| than the crater.
| [deleted]
| jacquesm wrote:
| Let's hope there are no 'dark companions' like with the
| Chelyabinsk meteor.
| marcodiego wrote:
| > 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.
| [deleted]
| moonchrome wrote:
| That's what I get for reading HN before going to sleep...
| jacquesm wrote:
| If you wake up: no problem. If you don't wake up: no problem.
| lucb1e wrote:
| > If you wake up: no problem
|
| Depends on what you wake up from: sirens and broken windows
| everywhere but not a direct hit, for instance, I wouldn't
| call 'no problem' :(
| jacquesm wrote:
| Fair enough, that would definitely be a possibility. The
| dashcam and other videos from Siberia are still very fresh
| in my mind. That was a _very_ close call. Slightly
| different angle in a more populous part of the world...
| pyrolistical wrote:
| This is why numbers should always be bounded. Is this 3.3-3.5%?
|
| Or 0-3.4%?
|
| Or 0-6.8%?
|
| Etc
| mcint wrote:
| 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.
| mcint wrote:
| VSauce with packages summary for passive consumption.
| https://www.youtube.com/watch?v=4Wrc4fHSCpw
|
| And jacquesm's replies to my other comments,
| https://news.ycombinator.com/item?id=37139144
| hoten wrote:
| FYI VSauce is a different content creator than Veratasium
| (unaffiliated).
| mcint wrote:
| It was first seen on August 12, midday UT1. About a dozen
| observations. ZTm0038\* C2023 08 12.49542 06
| 32 33.23 +15 57 35.5 18.86rUNEOCPI41
|
| Is the first entry, and asterisk-marked, on
| https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038 at the
| bottom, in the Observations section. Unusual (new to me)
| format. Appears to me, first guess to read:
| [object] [yr] [m] [day.time-decimal] [position] [elevation-
| angle] [observatory]
|
| Likely oriented relative to the plane of the ecliptic, and
| absolute direction relative to Earth at time of observation.
|
| I don't know what I'm talking about. Just giving best-guess
| interpretations.
| yread wrote:
| 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
| lamontcg wrote:
| 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.
| vkou wrote:
| Yes, but how many ant-sized swimming pools deep is it?
| pcrh wrote:
| 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.
| chasd00 wrote:
| I don't know what action could be taken. The risk of mass
| anxiety and the behavior that comes with that is probably
| greater than any additional safety a vague 3 day warning would
| provide.
| jcul wrote:
| Is there any action that could have been taken? Genuinely
| curious, I read about a test of some technology for deflecting
| asteroids a few weeks ago on HN, but I don't think we really
| have those capabilities yet?
| radicaldreamer wrote:
| There is likely a capability in the classified world to
| launch a vehicle to hit this object, but it won't be used
| because disclosing this ability would spark an arms race.
| JumpinJack_Cash wrote:
| 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!
| hoten wrote:
| It seems any serious asteroid prevention program is going to
| require the learnings of "pointless" (as you might put it)
| scientific expeditions like putting an object into L2.
| jacquesm wrote:
| There have been many studies about what could be done to deal
| with asteroids that are on track to impact earth and the simple
| answer is 'nothing'. Frustrating, but unless you can think of
| something that none of the very clever people on those
| committees could think of it's going to stay that way.
| JumpinJack_Cash wrote:
| The obvious answer to that is being able to reliably detect
| asteroids on a collision course, and compute where is it
| gonna fall in order to proceed the emergency evacuation.
|
| But first you have to be able to detect it, second you have
| to do it with reasonable time to save as many people as
| possible
| jacquesm wrote:
| Again, these people aren't stupid. You will have a very
| large amount of uncertainty based on a series of
| observations which essentially project a circle of
| probability on the planet that shrinks as more information
| from newer observations comes in and then _just_ before
| impact that probability will either drop to zero because it
| is deemed to be a near miss (sorry, George) or it will then
| become a certainty. By that time it will be too late to
| evacuate. I can dig up the report from one of these
| committees if you want (I should be able to find it), they
| make for very interesting reading, it is a really nice
| example of science at work, even if the result is a
| negative. Anything more advanced makes for great special
| effects in movies and science fiction but isn 't going to
| work. You'd have a very short time to move the entire
| population of a circle with a radius of a few hundred
| kilometers to outside of that circle starting from the
| center. The longer you waited the fewer people you'd have
| to move but the bigger the chance you'd be too late.
| vkou wrote:
| Any links to these reports?
| jacquesm wrote:
| I can go digging.
| dheera wrote:
| I'm surprised Elon Musk didn't pick up on this a couple days ago
| and launch something at it.
| rossdavidh wrote:
| 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.
| haunter wrote:
| H=19.9
|
| ~400m diameter
|
| https://cneos.jpl.nasa.gov/tools/ast_size_est.html
| Keyframe wrote:
| Where did you get its albedo (reflectivity)?
| [deleted]
| lucb1e wrote:
| That's in the submission, there's a column called H in the
| first table that says 19.90
| ortusdux wrote:
| The chart is H vs. Albedo, and is awkwardly formatted. H
| is the brightness observed on earth. Albedo is the
| inherent reflectivity of the object. What the chart is
| saying is that if we observe an object that is 19.5 H
| bright, it could either be highly reflective (0.30
| albedo) and 310m across, very dim (0.05 albedo) and 760m
| across, or somewhere in between.
|
| As I understand it, we can only calculate the albedo if
| we know the size and apparent brightness.
|
| I'll note that the linked NEOscan page has an H of 19.9,
| while JPL's CNEOS has an H of 19.2.
| [deleted]
| killthebuddha wrote:
| 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?
|
| In general, I am very confused by this news because "400m
| diameter asteroid 3% chance of impact" is something I would
| expect _literally everybody_ to be talking about all the time. It
| 's also something where if I learned that everything north of
| Kansas has a 5% chance of getting hit but everything south of
| Houston has a 1% chance, I'd seriously consider taking an
| impromptu vacation.
| vkou wrote:
| Uncertainty in measurements make it almost impossible to tell
| _where_ an object like this is going to impact, until we are
| hours, if not minutes away from impact.
| mrb wrote:
| I can answer 2 of your questions: - What is the
| probability that this asteroid will hit us?
|
| It's listed in the article: Impact probability 0.034, meaning
| 3.4% chance of impact. - What is the time
| interval where that probability applies?
|
| It's also listed: impact was estimated to potentially occur
| between 2023/08/14 04:48 TDB and 2023/08/15 12:22 TDB. (TDB
| seems to be UTC time without leap seconds? not sure). In other
| words the asteroid already passed Earth, and is currently no
| longer a risk.
| onlyrealcuzzo wrote:
| Probability without confidence interval is not very useful.
|
| If there's <1% confidence - this is not exactly news.
| Karellen wrote:
| TDB: https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time
|
| > [TDB] is a relativistic coordinate time scale, intended for
| astronomical use as a time standard to take account of time
| dilation when calculating orbits and astronomical ephemerides
| of planets, asteroids, comets and interplanetary spacecraft
| in the Solar System. TDB is now (since 2006) defined as a
| linear scaling of Barycentric Coordinate Time (TCB). A
| feature that distinguishes TDB from TCB is that TDB, when
| observed from the Earth's surface, has a difference from
| Terrestrial Time (TT) that is about as small as can be
| practically arranged with consistent definition: the
| differences are mainly periodic, and overall will remain at
| less than 2 milliseconds for several millennia.
|
| https://en.wikipedia.org/wiki/Terrestrial_Time
|
| > TT is distinct from the time scale often used as a basis
| for civil purposes, Coordinated Universal Time (UTC). TT is
| indirectly the basis of UTC, via International Atomic Time
| (TAI). Because of the historical difference between TAI and
| [Ephemeris Time] ET when TT was introduced, TT is
| approximately 32.184s ahead of TAI.
|
| Phew!
| Leary wrote:
| Found this tweet with an impact probability map that is around
| northern US/Asia/Europe :
| https://twitter.com/JoelSercel/status/1691549821629526219
|
| "If it is real this IS the worst asteroid threat ever
| discovered and the impact location and times are ugly (will
| post pics shortly). Note that the impact is in the next couple
| days! However, an Italian colleague of one of our astronomers
| suspects there is an error in the reported observations and
| there has been no chatter about this object and no followup.
| This probably means that it is not real. " - Joel C. Sercel,
| PhD
|
| I'm guessing the impact death area will be around 3600 km2 (I
| have no idea, please correct), so ultimately the chance of it
| falling on me is 1 in 10,000 to 1 in 100,000 provided the
| asteroid hits. Which means 1 in 1,000,000 to 1 in 10,000,000 in
| total? (assuming 1% hit probability)
| noduerme wrote:
| If I'm looking at the time chart correctly, that basically
| corresponds to "daylight hours", when you're facing the sun,
| tomorrow within the northern hemisphere...
| radicaldreamer wrote:
| We should look for secondary evidence, did the gov start
| continuity of gov operations etc. If it is real and if
| nothing can be done about it, we cannot expect official
| confirmation.
| tophi wrote:
| There is a disclaimer from the data source: "Scout data are
| about unconfirmed objects and all information should
| therefore be treated as potentially unreliable"
|
| I'm hoping this ztm0038 is an error or hoax.
| ortusdux wrote:
| Do NEOscan and CNEOS share data? They have slightly
| different details:
|
| https://cneos.jpl.nasa.gov/scout/#/object/ZTm0038
| onlyrealcuzzo wrote:
| If it hits the ocean, how big will the tidal wave be?
| 1970-01-01 wrote:
| We need an expert to explain these facts and numbers. Until
| then, please buy necessary amounts of toilet paper.
| lijok wrote:
| Spotted 3 days ago. There's an incentive not to publicize this.
| Lots of close passes only get coverage after the fact.
| apatil wrote:
| Also, is it possible to quantify the risk of unseen companion
| asteroids, which someone else mentioned in the comments.
| Analemma_ wrote:
| When a new potentially-hazardous asteroid is discovered, it's
| normal for the probability of impact to go up a couple times
| before abruptly plummeting to zero, as the radius of
| uncertainty shrinks until it shrinks past the Earth. See https:
| //en.wikipedia.org/wiki/Torino_scale#/media/File:Apoph....
|
| A 3% chance of impact right after discovery with the initial
| error ellipse isn't all that unusual; it will almost certainly
| be revised to 0 with more observation (and if it's not, you'll
| hear about it).
| mortehu wrote:
| What percent of the times when the initial probability is 3%
| will it later be revised to zero? Is it more than 97%?
| apatil wrote:
| This makes sense, thanks. However, it doesn't mean that the
| 3% estimate of the chance of impact was wrong at the time of
| initial observation given data available, and that still
| makes it a huge deal at that time. At minimum, it would seem
| to justify using the best available instruments to
| characterize the asteroid more precisely as soon as possible.
|
| If these large numbers happen so often that asteroids with
| initial impact probabilities of 3% are known to actually
| impact much less frequently than that, then the model is
| poorly calibrated, no? In other words, the reported
| probabilities aren't really probabilities and that is what
| has caused the confusion and anxiety in these comments.
| abathur wrote:
| I don't _know_ , but I suspect this is more about the
| limits of the observations (which I imagine are mostly from
| terrestrial observatories) needed to obtain much certainty
| about the object's size, course, speed, density, etc.
| cfraenkel wrote:
| It's not a model that is poorly calibrated - you seem to be
| taking a software-centric concept far away from where it's
| useful. The uncertainty at initial observation is because
| when you first observe an object, you only have
| observations covering a tiny bit of the orbit, resulting in
| very wide error bars. The "model" (Newtonian orbital
| dynamics) is one of the most precise models we have.
| Doesn't help when the observations are noisy.
| MauranKilom wrote:
| Unless one in every 33 asteroids that have 3% impact
| probability at some point in time actually impacts earth,
| there is clearly some unwarranted assumption in the error
| bar/distribution calculation.
|
| "The measurement data has noise" does not explain why the
| noise has a bias towards "the asteroid will hit earth"
| whereas reality so far has been biased towards "the
| asteroid will not hit earth".
|
| (This assumes that significantly more than 33 asteroids
| have had >= 3% impact probability predicted at some
| point. The opposite would not be less concerning.)
| noduerme wrote:
| One explanation would be the Anthropic Principle.
| [deleted]
| snewman wrote:
| If you have very wide error bars, shouldn't your estimate
| of impact probability be much lower than 3%? Most
| trajectories within your error bars will not intersect
| the Earth.
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