Talk:2024 YR4

2024 YR4 Torino scale 3 probability

I think the probability of Torino scale 3 is 99%. 長衫兆紫隆 (talk) 07:06, 27 January 2025 (UTC)[reply]

2024 YR4 Torino Scale Chart
Energy (MT)	Probability
Energy (MT)	<0.0078%	≥0.0078%, ≤0.0091%	>0.0091%, <0.01%	≥0.01%, ≤0.20%	>0.20%, <0.78%	≥0.78%, <0.91%	=0.91% (now)	>0.91%, <1%	≥1%, <78%	≥78%, ≤91%	>91%, <99%	≥99%
MT<100	0	0	0	0 or 1	1	1	1	1	3	3	3	8
100≤MT≤115	0	0	0 or 1	1	1	1	1	1 or 2	4	4	4 or 5	9
MT>115	0	0 or 1	1	1	1	1 or 2	2	2	4	4 or 5	5	9

Probability Evolution

December 28, 1860/1 December 29, 1044/1 December 30, 919/1 December 31, 875/1 January 1, New Year holiday January 2, 842/1 January 3, 760/1 January 4, 735/1 January 5, Sunday January 6, 710/1 January 7, 630/1 January 8, JPL on fire January 9, JPL burning January 10th 630/1 January 11th 630/1 January 12th Sunday January 13th 630/1 January 14th 630/1 January 15th 620/1 January 16th 610/1 January 17th 610/1 January 18th 610/1 January 19th Sunday January 20th 550/1 January 21st 320/1 January 22nd 190/1

文爻林夕 (talk) 16:40, 27 January 2025 (UTC)[reply]

In many early screenshots, there are two collision probabilities: 2032-12-22.59 and 2032-12-22.62. Should we choose the highest one or calculate their sum? 文爻林夕 (talk) 17:58, 1 February 2025 (UTC)[reply]

I'm sorry, I always mess up the form. 文爻林夕 (talk) 18:13, 1 February 2025 (UTC)[reply]

I would not worry about earlier calculations as two virtual impactors that are only 40 minutes apart are the same generic risk scenario. We know exactly where Earth will be on 22 Dec 2032 at 14:00 UT, the only question is very minor differences in the LOV for the asteroid. The LOV is cigar shaped and is very much longer than it is wide. -- Kheider (talk) 18:18, 1 February 2025 (UTC)[reply]

1:71 ? not 1:77 ?

In any other place i find 1:77 (1.3%). Sinucep (talk) 00:16, 30 January 2025 (UTC)[reply]

@Sinucep: The cumulative risk is 1:71. The risk for the impact in 2032 (which is by far the most likely out of the 5 possible impacts, and the only one that is noteworthy) is 1:77.[1] Renerpho (talk) 00:41, 30 January 2025 (UTC)[reply]

@Renerpho:Here (https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20YR4) i see that all the other impacts only increase the probability by tens of millionths.. where did you find 1:71? Sinucep (talk) 00:53, 30 January 2025 (UTC)[reply]

@Sinucep: Click on the number 1.4e-2, to the right of "Impact Probability (cumulative)". Renerpho (talk) 01:29, 30 January 2025 (UTC)[reply]

I just noticed the wrong number (1:71) was still in the collapsible table. I have now removed it. Renerpho (talk) 02:54, 30 January 2025 (UTC)[reply]

2024 YR4 Impact Energy

S-type (density 2.5~3.5g/cm³, albedo 0.15~0.25) diameter 43~56m, mass 1.04*10⁸ kg ~ 3.22*10⁸ kg, energy 3.72 Mt ~ 11.54 Mt TNT.

L-type (density 2~3g/cm³, albedo 0.05~0.15) diameter 56~96m, mass 1.84*10⁸ kg ~ 1.39*10⁹ kg, energy 6.60 Mt ~ 49.83 Mt TNT. 長衫兆紫隆 (talk) 05:48, 30 January 2025 (UTC)[reply]

@長衫兆紫隆: I appreciate your help trying to make the article more comprehensive, but unfortunately your estimates for 2024 YR4's density, albedo, and size cannot be added to this article because there are no official and reliable sources that give this information directly. This qualifies as original research, which is not allowed on Wikipedia. Sorry. Nrco0e (talk • contribs) 06:34, 30 January 2025 (UTC)[reply]

25 Dec 24 position poor?

"The earliest known precovery (pre-discovery) observation of 2024 YR₄ was on 25 December 2024, although the measured position of the asteroid in that observation is poor." Article says this, but references cited don't seem to call position measurements poor. Deen says "I personally consider the measurement and its associated uncertainty trustworthy, but I can understand others disagreeing". Clarifying this needs more information than I have. It's probably not important as it will become clearer with time and Palomar data.

The Sky & Telescope article makes an interesting point: work backwards: "one way to [determine] the possibility of impact is to find prior observations of exactly the point where the asteroid would have had to be if it were indeed on a collision course. If there were nothing there, then the asteroid couldn’t be on that course, and an impact would be ruled out."

Best wishes, Pol098 (talk) 17:54, 30 January 2025 (UTC)[reply]

@Pol098: Looking at the 2024 YR4 observation data from the MPC Explorer page, the astrometry in that single 25 Dec 2024 precovery has a root-mean-square error of 1.6" in RA and 0.7" in Dec. The RMS residuals of this precovery are significantly higher than almost all the other observations listed for 2024 YR4. This is presumably due to the fact that 2024 YR4 was moving quite fast on 25 Dec 2024; I'd imagine it'd be pretty hard to accurately measure the position of something moving at 200"/min, which would give the object a smeared rather than a pointlike appearance. Attempting to fit that precovery with other observations in an orbit-fitting software like Find_Orb shows that the precovery observation doesn't really fit well with residuals of around ~1" (compare to the mean RMS residual of around 0.24" reported by Find_Orb), hence why that 25 Dec 2024 precovery measurement is somewhat unreliable. That's essentially what Deen (and others like me who deal with asteroid observations) have noticed with 2024 YR4. Nrco0e (talk • contribs) 18:20, 30 January 2025 (UTC)[reply]

Daniel Bamberger here. If I may comment on this, as I was involved both in Sam's adjusted impact risk estimates, and in the Sky & Telescope article: When this object's observation arc was shorter, I had doubts about the validity of the Dec. 25 observation, for several reasons:

It is a single data point, and the final orbit very strongly depends on it. A shift of just a few tenths of an arc-second in its position leads to a very different outcome in 2032. Putting much weight on single measurements is rarely a good idea. Usually one wants at least two, ideally three to five observations per site per night, so that random errors are more likely to cancel each other out, and are more easy to spot. We don't always have that luxury, and I'm glad that this observation exists at all.
The observation is poor in the sense described by Nrco0e, having some large uncertainty. It is not poor in the sense that something is wrong with it. In fact, it would be expected to be off by around 1" or more, based on the uncertainty that was reported by the observers. As I said, I had some doubts about it previously, but now that the arc has been extended further, I can confidently say that its residuals are within the expected range. I believe I agree with Sam on this question.
That the uncertainties in RA and Dec are so different (1.6" vs. 0.7") is a consequence of measuring a trailed image rather than a point source. The SOLEX/EXORB software I was using to help Sam estimate his "adjusted" impact probability (among other things, like producing the risk corridor map) is very powerful, but it has difficulties dealing with observations for which RA and Dec need to be weighed differently. Sam's overall result doesn't depend on whether one includes that observation or not, and this turns out to be a minor issue in the end.

@Pol098: I hope this clarifies things? Renerpho (talk) 18:54, 30 January 2025 (UTC) I have reworded it and added an explanatory note. I hope this helps. Renerpho (talk) 19:09, 30 January 2025 (UTC)[reply]

@Renerpho: Much better, the statement is clearer, and the footnote with reference supports it. I've changed the RMS link to Root mean square deviation, which I expect is what's meant. Best wishes, Pol098 (talk) 19:30, 30 January 2025 (UTC)[reply]

Right, thank you! Renerpho (talk) 19:57, 30 January 2025 (UTC)[reply]

That means the impact probably will rise to 3~6%? 長衫兆紫隆 (talk) 04:25, 31 January 2025 (UTC)[reply]

If you mean Sentry's risk assessment then no, that wouldn't be a valid conclusion. They are not (yet) taking negative observations of 2024 YK4 into account. Renerpho (talk) 17:42, 31 January 2025 (UTC)[reply]

Mention JWST's capability of detecting 2024 YR4

I'm bringing this up to the talk page by the request of an IP user who originally wanted to mention JWST on the article.

Would it be worth mentioning in the article that JWST is capable of detecting decameter-sized asteroids like 2024 YR₄ at large distances up to the asteroid belt? There's been a study about this published last month, and although it doesn't directly talk about 2024 YR₄, it could have applications to 2024 YR₄. Particularly, JWST could observe the asteroid while it is outbound and too far to be observed by optical telescopes. I'm somewhat concerned this may fall under WP:SYNTH of Wikipedia's no original research rule (not to mention that reliable sources and news outlets have not mentioned JWST observing 2024 YR4 yet), but I'd like to hear what others think. Nrco0e (talk • contribs) 19:16, 30 January 2025 (UTC)[reply]

This quote from the source may have some relevance to 2024 YR₄ even though it isn't a direct mention of the asteroid. But I thought it's worth mentioning. Nrco0e (talk • contribs) 20:09, 30 January 2025 (UTC)[reply]

"The capability of JWST to observe decametre objects all the way to the main belt (including NEOs at their aphelion) while deriving tighter (that is, nearly albedo-independent) sizes highlights its unique capability to monitor and study with great precision possible future impactors detected closer to Earth by other surveys, thereby making JWST an important asset for future planetary-defence efforts."

Great idea! Let someone propose to use JWST in this way, then mention that on Wikipedia (citing their proposal). Until then, this is WP:SYNTH. Renerpho (talk) 19:20, 30 January 2025 (UTC)[reply]

An article by Jonathan O’Callaghan in Scientific American notes that a researcher from ESA has applied for time on JWST to observe 2024 YR4. https://www.scientificamerican.com/article/will-asteroid-2024-yr24-strike-earth-in-2032/ 1.145.138.112 (talk) 04:07, 1 February 2025 (UTC)[reply]

JWST is a multi-billion dollar telescope whose time is valued at an equally massive rate. The approach of 2028 is close enough that it will perturb the orbit significantly, which means that current unavoidable uncertainties in the orbit will be greately magnified ater that close approach.

Putting all these together, it is an appallingly poor use of expensive telescope time to observe the asteroid NOW. After the 2028 close approach, IF that results in predictions of a very close approach or even a possible collision - sure. But not now. 2001:8003:E40F:9601:983:E2D8:2FEA:C9C2 (talk) 00:51, 31 January 2025 (UTC)[reply]

@2001:8003:E40F:9601:983:E2D8:2FEA:C9C2 Am I wrong in thinking that if we refine the orbit now, we can predict the 2028 pertubation much more accurately?

It also gives 1. significantly more time to prepare a DART-type redirection mission, which would take potentially > 4yrs to plan; and 2. some interesting new data on near-Earth objects, which AFAIK haven't been observed with JWST before ElectronicsForDogs (talk) 21:45, 3 February 2025 (UTC)[reply]

I saw some discussion on X about whether the SOFIA Observatory can be resumed and photograph the asteroid. 文爻林夕 (talk) 03:14, 4 February 2025 (UTC)[reply]

Monte Carlo Impact Probability

According to JPL, the impact probability will be 1.64% (1 in 61) 長衫兆紫隆 (talk) 14:48, 31 January 2025 (UTC)[reply]

According to JPL, the impact probability will be 1.77% (1 in 56) 長衫兆紫隆 (talk) 15:18, 1 February 2025 (UTC)[reply]

It ended up being 1/63 and 1/59, respectively. Renerpho (talk) 18:39, 1 February 2025 (UTC)[reply]

I just simulated the impact probability on python, and I always show the probability to hundredth of the percent. 長衫兆紫隆 (talk) 00:12, 2 February 2025 (UTC)[reply]

According to JPL, the impact probably will be 1.4% (1 in 71) 長衫兆紫隆 (talk) 14:27, 2 February 2025 (UTC)[reply]

According to JPL, the impact probably will be 1.53% (1 in 65.4) 長衫兆紫隆 (talk) 14:58, 3 February 2025 (UTC)[reply]

Occultation

An occultation on Feb 6 of a mag 11 star lasting 0.14 seconds detected by multiple reliable telescopes would refine the trajectory greatly, but would tell us basically nothing about the size that we do not already know. 98943 Torifune (2001 CC21) mentioned in the edit summary is nearly 500 meters in diameter and was only 0.13 AU from Earth on 5 March 2023. By Feb 6th, YR4 will be 0.39 AU from Earth. -- Kheider (talk) 20:25, 1 February 2025 (UTC)[reply]

The duration of the occultation gives information about the magnitude. If it really was a 0.14 second dip in brightness, that would be even longer than (98943), 12h46m47.s252 ± 0.s003UT and12h46m47.s346±0.s003 UT. 文爻林夕 (talk) 21:52, 1 February 2025 (UTC)[reply]

Of course, current occultation technology and star catalogs are not suitable for occultation of asteroids of this size. It is very likely that there will be no occultation as you said. But as long as there is a reliable decrease in brightness, sub-second milliseconds can provide help in terms of size. 文爻林夕 (talk) 21:56, 1 February 2025 (UTC)[reply]

Mind you that Dave Herald user a diameter of 100 meters for his 2024 YR4 occultation prediction. Given 2024 YR4's spectral type, it's most likely half that size, which means the occultation duration will be half the 0.14 second value reported by Herald. Such a short dip will make it more prone to being drowned out by Fresnel diffraction.

Sam Deen brings a similar argument in the IOTA occultations mailing list, though he mentions an interesting possibility of ruling out virtual impactors via occultation. Interesting, but that cannot be added to the Wikipedia article until more reliable sources (news articles, etc.) start talking about observing 2024 YR4 via occultations. Nrco0e (talk • contribs) 22:37, 1 February 2025 (UTC)[reply]

Let's wait for the occultation result on the 6th. I also think there is a high probability that it will miss. It is too small. 文爻林夕 (talk) 23:08, 1 February 2025 (UTC)[reply]

I don't know their telescope arrangements for the American occultation on February 6. The occultation across the Indian Ocean and China on February 8, with a 1-sigma width of 6.6 km, requires 48 telescopes to ensure coverage of the occultation (penumbra 140 m).文爻林夕 (talk) 09:35, 2 February 2025 (UTC)[reply]

As Fresnel allows its occultation to cover larger and larger areas, the brightness decreases lower and lower. We may encounter the same problem with 1I/'Oumuamua, and by the time we understand its nature, diffraction will have ruled out a successful occultation. 文爻林夕 (talk) 05:09, 3 February 2025 (UTC)[reply]

In order to ensure the success of this occultation passing through Xiamen, 48 telescopes are needed, and only a few have been assembled so far. 文爻林夕 (talk) 05:14, 3 February 2025 (UTC)[reply]

HiPERCAM can take a thousand pictures per second, and 0.1 seconds is enough to take 100 pictures. It helped scientists discover the very faint Rings of Quaoar. Of course, we can't expect the occultation track of 2024YR4 to pass through the Gran Telescopio Canarias. 文爻林夕 (talk) 23:01, 1 February 2025 (UTC)[reply]

@文爻林夕: Since you keep insisting to mention the 6 Feb 2025 occultation in this article, we need to talk this out because I don't want to get into an edit war with you. I feel like the occultation-related stuff you're adding to the article has too much detail (especially for something that probably won't be observed and is not talked about by news reports) and would be confusing to a layman reader. This is only the second paragraph of the article introduction, and introductions are supposed to be clear and simple without too many technical concepts.

I think we should create a new section that talks about 2024 YR4 observations and its discovery, since this article doesn't really talk much about them. We can then put all the occultation details in that section instead of the introduction. Does that sound good to you? Nrco0e (talk • contribs) 17:06, 2 February 2025 (UTC)[reply]

Change it to say that after the asteroid is no longer observable with most telescopes, there is still a chance to observe it through occultation. Then move the rest of the chapter to the back as a chapter on occultation observation? There will no longer be a change that interrupts other chapters while I am editing. . . I think this is better too. I apologize for the interruption just now.文爻林夕 (talk) 17:15, 2 February 2025 (UTC)[reply]

Until any occultations are observed it should not take up much, if any of the lede. And we need to be careful of WP:SYNTH. -- Kheider (talk) 17:48, 2 February 2025 (UTC)[reply]