Talk:Near-Earth object

Text copy-and-pasted from Impact event

The material in the subsection "Close approaches and forecasts" doesn't belong in the Impact event article; they didn't cause impacts. Here is the text copy-and-pasted if someone wants to incorporate it into this article:

For some reason it created its own section. It follows this one.

Bettymnz4 (talk) 03:01, 7 April 2010 (UTC)

Close approaches and forecasts

See also: Near-Earth object

On May 19, 1996, a 300 to 500 m (980 to 1,640 ft) asteroid, 1996 JA1, passed within 450,000 km (279,617 mi) of Earth; it had been detected a few days before.

On March 18, 2004 a 30 m asteroid, 2004 FH, passed within 40,000 km of Earth only a few days after it had been detected. This asteroid probably would have detonated in the atmosphere and posed negligible hazard to the surface, had it been on impact course.

On March 31, 2004, a 6 m (20 ft) meteoroid, 2004 FU162 made the second-closest approach on record (closest so far was The Great Daylight 1972 Fireball) with a separation of only 1.02 Earth radii from the surface (6,500 kilometres (4,039 mi)). Because this object is certainly too small to pass through the atmosphere, it is classed as a meteoroid rather than an asteroid.

Path of risk where 99942 Apophis may impact Earth in 2036.

In 2004, a newly discovered 320 m (1,050 ft) asteroid, 99942 Apophis (previously called 2004 MN4), achieved the highest impact probability of any potentially dangerous object. The probability of collision on April 13, 2029 is estimated to be as high as 1 in 17 by Steve Chesley of NASA's Jet Propulsion Laboratory, though the previously published figure was the slightly lower odds of 1 in 37, calculated in December 2004. Later observations showed that the asteroid will miss the earth by 25,600 km (15,907 mi) (within the orbits of communications satellites) in 2029, but its orbit will be altered unpredictably in a way which does not rule out a collision on April 13 or 14, 2036 or later in the century. These possible future dates have a cumulative probability of 1 in 45,000 for an impact in the 21^st century.

Asteroid 2004 VD17, of 580 m (1,903 ft), previously was estimated to have a probability of 1 in 63,000 of striking earth on May 4, 2102 (as of July 2006), with risk 1 on the Torino scale, but further observations lowered the estimate. As of the observation on December 17, 2006, JPL assigns 2004 VD17 a Torino value of 0 and an impact probability of 1 in 41.667 million in the next 100 years.

Asteroid (29075) 1950 DA has a potential to collide with Earth on March 16, 2880. The probability of impact is either 1 in 300 or zero, depending on which one of the two possible directions for the asteroid's spin pole is correct. This asteroid has a mean diameter of about 1.1 km (0.68 mi). The energy released by the collision would cause major effects on the climate and biosphere and may be devastating to human civilization.

Asteroid 2007 TU24, with an estimated diameter between 300 to 500 m (984 to 1,640 ft), came very close to earth orbit by 1.4 ld (lunar distance) on January 29, 2008. The orbit of the asteroid is shown on NASA's website.

Relatively small objects that burn up in the atmosphere can be dangerous beyond their own capabilities. In 2002, U.S. Air Force Brig. Gen. Simon P. Worden told members of a U.S. House of Representatives Science subcommittee that the U.S. has instruments that determine if an atmospheric explosion is natural or man-made, but no other nation with nuclear weapons has that detection technology. He said there is concern that some of those countries could mistake a natural explosion for an attack, and launch nuclear retaliation. In the summer of 2001 U.S. satellites had detected over the Mediterranean an atmospheric flash of energy similar to a nuclear weapon, but determined that it was caused by an asteroid.

As of March 2008, the Near-Earth Asteroid with the highest probability of impact within the next 100 years is 2007 VK184, with a Torino scale of 1.

Bettymnz4 (talk) 03:00, 7 April 2010 (UTC)

Observational biases section re-write

With all due respect to the editors who worked on this admittedly important section, I found the version I saw yesterday to be very problematic:

• One of the main sources was low-quality (an article with no sources on permanent.com, the personal webpage of a somewhat cranky enthusiast) and thus needed replacing.
• There is a sentence with stats showing that most NEOs are discovered near opposition. The stats are without context, the source that was given was wrong, and I tracked down that it is original research by a user for the creation of this image on Wikimedia, and thus violates WP:OR.
• Many other sources were used inappropriately, to support claims they didn't make or with the claims they did make conflated with another.
• The description of the various biases was also too imprecise (probably still is in the new version).

Sadly, what appears to be the seminal work on observational biases, Bottke (2000), is behind a paywall, and I didn't find a good popular-science-level overview article either, so the section could probably still see significant improvement. Rontombontom (talk) 10:27, 26 January 2024 (UTC)

Diagrams showing orbital classes

The five diagrams presently included in the article are all problematic for different reasons. I made a request for a new diagram at WP:GLI. Rontombontom (talk) 17:24, 27 January 2024 (UTC)

Forgot to add: this was quickly solved, Nsae Comp found & inserted a public-domain NASA diagram instead. Rontombontom (talk) 16:55, 31 January 2024 (UTC)

Working-towards-FA feedback...

Ok placeholder here. Aim is to address as much as possible before going there. Cas Liber (talk · contribs) 19:40, 31 January 2024 (UTC)

• In lead - Most known PHOs and NEOs are asteroids, but a small fraction are comets - I'd put the percentage or percentage range here. Cas Liber (talk · contribs) 19:40, 31 January 2024 (UTC)
  • First, a thanks! Second, done. But 0.35% is such a small percentage. Rontombontom (talk)

• In body - Near-Earth objects (NEOs) are [by convention technically] defined... - could remove bracketed text without losing meaning...?
  • I replaced t with "formally", which matches what's written in the IAU source. Rontombontom (talk)

• Rejig the lead into 3 or 4 paragraphs of related material.

• The Close approaches section seems to contain similar material to the History of human awareness of NEOs section...but is waaay down the article. Could we maybe combine them?

• The Risk section would make more sense being moved further down the article to directly before what we do about these things...maybe...

• See also sections should only be populated as a last resort. In general I remove any links that can be in the body of text or at a more relevant location, or remove those entirely that are only very generally related to the article.

• Overall, the article is at the longer end - if more content needs adding it might be prudent to remove or summarise some exisiting content

• I began aligning refs to a consistent format. Doing this before FAC is prudent too.

  Yesterday I merged two paragraphs into one in the lead - was that enough?

  To reduce the length of the article, I think I can merge and shorten the Risk & Magnitude of risk sections (the wikilinked articles on the Torino & Palermo scales are fairly well detailed), and trim the Close approaches section, but it'll require careful consideration of what to keep & what to cut. Every section from History... to Artificial near-Earth objects is linked logically to the previous section, so I have to think about what could be done to fit Close approaches (and the linked Impacts) in-between. I think I'll have time over the weekend for this substantial work.

  The date formats were already consistent and in line with MOS:DATEUNIFY, but perhaps not in the way you're used to (EDIT: I realise this may sound passive-aggressive... what I meant was that you'll find this formatting in several Wikipedia articles, including some FA, but I encountered other experienced Wikipedia editors before who were unfamiliar with it): dates in the article body are all in the US date format, publication dates in citations are all in the same format as in the article text, while all access dates and archive dates are (well, were before your edit) in ISO format. Is there an FA preference here for full date format uniformity that goes beyond MOS:DATEUNIFY? As for replacing all authors with first-lasts, I started that last month but apparently forgot to finish it; can do that, too, over the weekend. Rontombontom (talk) 15:26, 15 February 2024 (UTC)

  An update on the MOS:DATEUNIFY issue. I like access & archive dates in ISO format for practical reasons: I primarily look at them to see how old they are and if an update is warranted, which is much easier to see than in the US date format; especially for some key sources (like archive.org) that use URLs with YYYYMMDD in them. On the other hand, looking at Wikipedia:Vital articles/Level/5/Physical sciences/Astronomy, the only FA I found with the same formatting choice (US for article body & publication and ISO for access/archive) is Cygnus X-1. So if this is really a factor in FA acceptance, I'll change the format of all access/archive dates over the weekend, too. Rontombontom (talk) 17:31, 15 February 2024 (UTC)

  Ah I see. Ok, I haven't been at FAC a while but we'd always line them up to be consistent. If others have been getting through like the way you have it then happy to leave it. Cas Liber (talk · contribs) 23:19, 15 February 2024 (UTC)

  I went through all your suggestions, please check how well it works now. Specifically, I have the same notion towards the See also... section as you, but there are just too many for this sprawling subject. I went through it again, and although I removed a few and put one into the article, I found the nine that remained are all relevant, but not enough to warrant addition to the article (or else the article will be really too long). For example, EURONEAR is a survey programme, but its discoveries are dwarfed by the ones already mentioned in the article, while NEOShield was a planetary defence research project which appears much less significant than what NASA has done. Rontombontom (talk) 21:55, 18 February 2024 (UTC)

  Having slept over it, I now find the new ordering even more problematic. The lead part of the History of human awareness of NEOs section and the Risk section tell different parts of the same story and should belong together. Will have to think about a better ordering. It will probably need some redundancies (for example a single-sentence re-cap of the close approachas of Halley's Comet, Hermes & Icarus in the Close approaches section after it is moved back to its original place). Rontombontom (talk) 10:17, 19 February 2024 (UTC)

  Another possible solution: keep the sequence as is, but refocus the intro of the History... section on the recognition of the extraterrestrial nature of meteors & comets + the discovery of the first NEA, and move other historical events to Close encounters & Risk. Then only the first NEA will have to be mentioned twice. Rontombontom (talk) 17:16, 19 February 2024 (UTC)

  Ugh, this was a lot of work, but finally done (I chose the second option). I'd really appreciate a second (or third or fourth...) opinion on whether the article's structure is now consistent and has good enough flow. Rontombontom (talk) 18:59, 21 February 2024 (UTC)

I think it is still jumpy - I would place the Number and classification section directly under Definition (as material similar), then all the History of human awareness of NEOs section (down to and including risk) then the Exploratory missions section. This is the best way I can think of to minimse subject matter jumping back and forth. Might also allow for some reduction Cas Liber (talk · contribs) 12:48, 6 March 2024 (UTC)

sdSds started a new section with a similar proposal at the bottom, I replied there. Rontombontom (talk) 17:55, 10 March 2024 (UTC)

So, pinging @Casliber: do you think we are ready for FAC? Rontombontom (talk) 13:54, 11 April 2024 (UTC)

Artificial vs. natural near-Earth objects

While the article has a section on "Artificial near-Earth objects" they aren't mentioned in the lead. Putting a mention there might give undue weight to the topic; perhaps merely adding the word "natural" somewhere in the lead would improve the article? (sdsds - talk) 22:07, 31 January 2024 (UTC)

• Done. Rontombontom (talk) 15:25, 1 February 2024 (UTC)

Explicitly excluding Earth's Moon

While obvious to the knowledgeable reader familiar with small solar system body topics, the article might be improved for general readers by explicitly mentioning that Earth's Moon is not considered a near-Earth object since it is a natural satellite. (sdsds - talk) 22:18, 31 January 2024 (UTC)

• I added a full sentence which also clarifies that planets & spacecraft aren't included. However, I doubt I could find an explicit source spelling this out. So I hope the "SYNTH is not explanation" section of WP:SYNTHNOT covers this. Rontombontom (talk) 15:25, 1 February 2024 (UTC)

Not necessarily near Earth

Again considering the general reader rather than the specialist, There's a key aspect captured by a sentence currently in the second section: "NEOs are thus not necessarily currently near the Earth, but they can potentially approach the Earth relatively closely." Consider moving that to be the last sentence of the lede paragraph. (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 23:32, 15 February 2024 (UTC)

I left it there but added a similar sentence right after the definition in the first paragraph of the lede. Does it work for you? Rontombontom (talk) 21:55, 18 February 2024 (UTC)

Yes the current version of the lede makes it clear, and leaving the details for later makes sense. Just nit-picking now...

• the use of 'whose' is potentially problematic since NEOs can't own their orbits. Perhaps something like, "A near-Earth object (NEO) is any small Solar System body whose orbit on a trajectory around the Sun that can bring it near the Earth?" Or "...in an orbit around..." would also avoid the personification of NEOs. Since solar system bodies all follow trajectories around the Sun even when we say they are orbiting a planet makes this murky. I defer to your subject matter expertise, acknowledging it might also be best to leave it as-is.
• and is using SSSB intended to imply a hypothetical interstellar object that zips between Earth and the Moon is not an NEO? That too is counter-intuitive for the general reader. If it were an NEO, the wording could reduce to, "...on a trajectory that can bring it...."

Thanks again for implementing the suggestion. The article deserves GA status! (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 00:36, 19 February 2024 (UTC)

Thanks for the nit-picking, no problem at all! I eliminated the two instances of "whose".

The problem with an interstellar object is the same as with long-period comets: the underlying intention is to find objects for which close encounters can be predicted well in advance with a good degree of confidence, but if something races in and out of the inner Solar System in a few months and returns in 50,000 years or never, you'll get neither a precise orbit nor a long-term prediction. It would be good to put this justification into the article, but sadly, even after searching for an hour, I couldn't find a worthy source that could be used for this. Rontombontom (talk) 19:22, 19 February 2024 (UTC)

Yes, retaining the current high quality of the article precludes adding content that might look like original research. Relatedly, it might seem obvious but the article is about how the phrase 'near-Earth object' is used in astronomy. Yet the article doesn't link early to astronomy, even where the term is used in the Observational biases section. Nor does it include an astronomy-related infobox. Is this intentional? Also, a link somewhere in the article to interstellar interloper might be useful for some readers, even if only in the 'See also' section. (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 21:05, 19 February 2024 (UTC)

I now implemented all of that. Rontombontom (talk) 14:48, 21 February 2024 (UTC)

Been busy - gonna read through soon. Another thought - article defines as is any small Solar System body with an orbit around the Sun that can bring it near the Earth. - but is it not anything closer to the sun than earth or are there any really close objects to the sun that are not NEOs? Cas Liber (talk · contribs) 22:44, 4 March 2024 (UTC)

That's a good question, a very good question! One I would love to cover explicitly in the article, but I can't find a good source (I had one but it was an article in a sanctioned non-peer-reviewed paper). But here is the situation regarding objects close to the Sun, as a synthesis of stuff I put into the article.

For now, the official NEO definition is anything that gets within 1.3 AU (Earth orbit radius) from the Sun. So yes, theoretically, that would include objects which are always close to the Sun (say on an orbit entirely within the orbit of Mercury, the definition of Vulcanoids) and thus not really near Earth. But we don't know any such objects. What's more, theoretical simulations show that such orbits aren't stable, both due to gravitational perturbations and non-gravitational ones, so we'll probably never find such objects greater than small rocks, and even if yes, they are likely to either end up destroyed or transfer to more eccentric orbits on which they can get closer to Earth. Even if we go out a bit further, to objects entirely within Venus's orbit (ꞌAylóꞌchaxnims, of which one is known), those don't have very stable orbits, either, perturbed by both Venus and Mercury. Getting to the next group in closeness to Earth's orbit, there are the co-orbitals of Venus. But all known ones are in eccentric orbits also crossing Earth's orbit and simulations show that the population of co-orbitals in near-circular orbits is low and not too stable either.

So, if our underlying motive in cataloguing objects as NEOs is to find anything that may be predicted in advance to hit the Earth, it is unnecessary to put an inner limit on the NEO orbital region. But I doubt that you'll find this written down explicitly anywhere. (I could not even find a clear statement justifying the exclusion of long-period comets from the NEO definition.) Rontombontom (talk) 17:47, 5 March 2024 (UTC)

Unsolicited comment: you have the article on a good path by avoiding this synthesis. At the same time I'm grateful for the explanation of it here! (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 23:47, 5 March 2024 (UTC)

Okay, so as it reads now - sentence 3 sorta labours the point a bit. I'd make the first sentence the official definition (now sentence 2), and then merge material from sentence 1 and 3 into a single sentence. Cas Liber (talk · contribs) 00:31, 6 March 2024 (UTC)

I edited it as per the suggestion. Rontombontom (talk) 17:53, 10 March 2024 (UTC)

Exploration mission delta-v requirements

Please review my recent edit in the Exploratory missions section. It attempts to get at the concept of delta-v being a measure of acceleration rather than velocity. Another way to do this might be to explicitly link Δv.

I further re-worded it.

I'm not sure what you mean with acceleration, and I may be missing something as I am no rocket scientist, but here is my understanding. Delta-v will be the time integral of acceleration over the time periods the rocket is fired. Low acceleration over a long time can achieve the same delta-v as high acceleration over a short time (see ion engines vs. chemical rockets). If you check the Tsiolkovsky rocket equation, using a given propellant with a specific effective exhaust velocity to deliver a given payload, delta-v is a function of only the initial total mass, whatever the acceleration. (Staging & atmospheric resistance will of course complicate things.) Rontombontom (talk) 19:58, 19 February 2024 (UTC)

Yes that's correct, delta-v is measured in units of velocity, and is the integral of acceleration over time. The current phrase 'sum total of changes in orbital speed' expresses that well. Thanks! (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 21:10, 19 February 2024 (UTC)

Rename and re-frame Definitions section

I suggest renaming the 'Definitions' section to 'Cataloging' and center the focus of the section on that. (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 23:54, 6 March 2024 (UTC)

Both you and Cas Liber proposed this. I can see the logic in it. However, I have other problems with it. Currently, the Number and classification section is a direct continuation of the Projects to minimize the threat section, which introduces the projects that led to the cataloguing in the first place. The very first subsection, Observational biases, is strongly tied to both of the preceding two sections (the biases stem from the methods of those surveys and indicates how the numbers of the discovered NEOs aren't necessarily representative of all NEOs). The Size distribution sub-subsection of the Near-Earth asteroids subsection also heavily builds upon the surveys introduced by Projects to minimize the threat. Meanwhile, the last sub-section, Artificial near-Earth objects, provides a bridge to the Exploratory missions section (though I can see that there is a link to Projects to minimize the threat, too).

Any ideas how these connections could be untangled without more jumpiness and duplications? I don't see a good way at the moment, will have to think about it.

Or do you have alternative ideas on how to reorder these sections? Rontombontom (talk) 17:51, 10 March 2024 (UTC)

Retitle the section and rearrange the paragraphs within. See User:Sdsds/sandbox/Near-Earth object. (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 06:06, 11 March 2024 (UTC)

A quick heads-up: OK, I'll check it, but I may not have the time before Friday. Rontombontom (talk) 12:56, 12 March 2024 (UTC)

I have now read your version. Seems I misunderstood you: you just want to rewrite the existing Definitions section, without the much larger re-ordering suggested by Cas Liber (moving the entire Numbers and classification section under the first chapter, which would make even more sense if the title is Detection and cataloging). Regarding your version, I would still put at least the definition of NEO in front, before using the term. (The same in the lede is a summary, the first chapter should stand on its own.) Otherwise, I could go with it. However, I also ask your opinion about the greater re-ordering suggested by Cas Liber, and if you can think of any solutions to my problems with it – the part you propose to re-write may need another re-edit if we do the big change. Rontombontom (talk) 17:11, 15 March 2024 (UTC)

The more extensive reordering proposal presents difficulties. I applaud the desire to make the article 'flow' better.

Links are another option; one possibility would be to move some content into separate articles, maybe e.g.: Detection and cataloging of small solar system bodies or Exploratory missions to small solar system bodies. I'm confident articles like that could be further expanded, and readers of the main article could choose whether and when to follow the links. That somewhat addresses the concern Cas Liber raises, though likely not entirely. (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 08:12, 19 March 2024 (UTC)

After a lot of consideration, here is my new alternative proposal: what if we do the opposite of your proposal? That is, keep the focus of Definitions strictly on definitions, and move the naming of the cataloguing bodies to the Numbers... section. (Plus, move the definition of JPL, ESA etc. acronyms to the new first instances.) A much more limited re-write, but one that I think that might also remove some of the jumpiness Cas Liber wanted to correct with that big reordering proposal (which doesn't seem to work for me or you). Rontombontom (talk) 13:30, 27 March 2024 (UTC)

Yes, that sounds like it would be an improvement! (— 𝐬𝐝𝐒𝐝𝐬 — - talk) 17:12, 27 March 2024 (UTC)

Done.

As for creating Detection and cataloging of small solar system bodies or Exploratory missions to small solar system bodies, both would make sense (especially the latter as ever more missions are done), but I would find the job overwhelming at the moment. Rontombontom (talk) 21:33, 29 March 2024 (UTC)