Talk:Near-Earth object/Archive 1

Sky not currently surveyed
Um, I changed "30% of the sky that has never been surveyed" to "30% of the sky that is not currently surveyed." For one, it's wrong. The southern sky has been surveyed. A NEO survey operated in Australia for some time before funding was cut by the government. And for two, it's a bit alarmist and misleading. Asteroids move. An asteroid that's in the Southern sky now will be in the Northern sky at some time in the future. If we miss our chance to see it this year, we'll have other chances in the future. Not looking at 30% of the sky doesn't mean we're missing 30% of the asteroids, it just means it takes us longer to find them.--Bankrobber | Talk 09:55, 4 July 2006 (UTC)

Volcanos
...Volcanos likely pose a greater short and medium term threat to people, in general, than bolides and rocks from the sky. Pinatubo, one of the most recent Krakatoa-size eruptions, occurred within the past 20 years, and volcanos, particularly in the Pacific Rim, have been showing off with Plinian eruptions on a regular basis. &mdash; Rickyrab | Talk 03:58, 21 June 2006 (UTC)
 * NEOs threaten more people and are more likely to hit without warning. Volcanos kill those who fail to heed warnings and evacuate, much like hurricanes.  Although, the longer time periods one must be away for a volcano are definitely more inconvenient, years instead of days.--Poodleboy 18:37, 4 July 2006 (UTC)

IAU definition of a Planet quiry
Any idea why do NEO's not fail Earth as a planet under point c, citing a planet must have cleared the neighbourhood around it's orbit. Surely NEO's are in the neighbourhood around Earths orbit? - JVG 15:37, 24 August 2006 (UTC)


 * I'd have to guess that the actual scientific criteria is more specific than "cleared out orbit." It must have something to do with the relative size of the near-by objects.  Of course, you need some criteria that doesn't complicate matters further, given the Moon's large size compared to NEOs. —Taka2007 19:20, 28 August 2006 (UTC)

Updated Congressional Mandate
Didn't Congress recently update the NASA mandate to find all NEOs down to 140 meters in diameter? —Taka2007 19:20, 28 August 2006 (UTC)

Inconsistancy
Just a quick question: Meteoroid defines a Meteoroid as "between 100 µm and 10 m across". However, the N.E.O. page briefly mentions a Meteoroid as being smaller than 50 metres. Which is "correct"? (Or, at least, more widely considered to be correct? --Dave the Rave (DTR) 19:03, 19 September 2006 (UTC)

adding 2007 tu 24 closest approach ever
with only 1.4 lunar distance away and 500 meters big. classified as http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007TU24;cad=1#cad -- —Preceding unsigned comment added by Manchurian candidate (talk • contribs) 12:02, 18 January 2008 (UTC)
 * It most certainly is not the closest approach ever. There are always objects closer than the moon, in fact. Even if we count only named objects, there have been 1.4 LD passes before. Saros136 (talk) 05:44, 4 December 2008 (UTC)
 * As Saros136 stated, 2007 TU24 is nowhere near the closest approach ever made. See: Closest Approaches to the Earth by Minor Planets (from the Minor Planet Center) -- Kheider (talk) 16:27, 20 November 2011 (UTC)

Suggested merge with Near-earth asteroid article
Nearly two years ago, a suggestion was made in the Near-earth asteroid (NEA) article talk pages to merge the articles. At that time there was one "weak objection" due to the inexact equality of the two concepts. I have just weighed in there, supporting the merge, and am copying my comments there for discussion here:


 * "I support merging, as near-earth asteroids are near-earth objects (NEO)s, and almost all near-earth objects (except spacecraft and very rarely comets) are asteroids. Furthermore, the intrinsic interest in NE objects that are not asteroids is much lower than the interest of asteroidal objects, first due to the impact hazard, second due to their scientific interest as targets for detailed astronomical and geochemical investigation, and third due to their potential value as accessible sources of useful extra-terrestrial materials. The NEO article is at this moment about 12KB long, while this article is about 22K long.  The impact hazard dominates both articles.  If there are to be two articles, I would suggest one devoted to the impact hazard and mitigation issues, and the other focused on the scientific questions and potential extraterrestrial resource aspects of the subject.  This issue was raised two years ago, and the articles may have been different at that time, but now the overlap and redundancy seems large.
 * If I do not hear significant objection from other editors, I may undertake a merge and re-organization of these myself when I have time."

I have no objection to two (or more) articles, but would split the subject matter as indicated above, and retitle to make the topic of each clear. I would appreciate the thoughts of other editors. Thanks. Wwheaton (talk) 04:24, 15 November 2008 (UTC)

I have added merge tags to both articles. I suppose this article should be the survivor, with a redirect from Near-Earth asteroid, as asteroids are a subset of objects. I think that means the discussion link should point here, but so far I have not succeeded in making that happen; maybe someone else who sees what I have done wrong can help? Thanks Wwheaton (talk) 21:35, 28 November 2008 (UTC)

OK, I finally saw what I did wrong and have fixed the discussion links. Wwheaton (talk) 21:45, 28 November 2008 (UTC)
 * Strong support for merge. The merge proposal makes sense.  The redundancy of the impact hazard is an important point in favor.  The difference of NEAs as a subset of NEOs can be handled adequately in the text of the merged article. Ikluft (talk) 07:57, 29 November 2008 (UTC)
 * Strong support What he said. Zazaban (talk) 03:46, 4 December 2008 (UTC)
 * Strong support: SAE1962 (talk) 13:25, 12 December 2008 (UTC)
 * I support the merge, with Near-Earth Asteroid being a type of Near-Earth Object. This will eliminate the redundancy, NEA is better-cited, and as NEA's are the major subset of NEO's, NEA's will likely be the main part of the NEO article. Awickert (talk) 04:29, 4 December 2008 (UTC)
 * Support. NEO article is already mainly about asteroids. Ruslik (talk) 09:31, 4 December 2008 (UTC)
 * Support. NEAs are a subset of NEOs and at this stge of article complexity the NEA article would fit into the NEO article. However in the future when more that 10-20KB of information is added about near earth non asteroid objects there might then be a reason to re-divide the articles. Trilobitealive (talk) 17:06, 6 December 2008 (UTC)
 * Strong support For know lets merge NEA and NEO.johnxxx9 (talk) 01:36, 9 December 2008 (UTC)

You can call this consensus and go ahead with the merge. Ikluft (talk) 22:23, 8 December 2008 (UTC)

Started merge
I have done a tentative merge of the lead paragraphs. Perhaps a bit too detailed. I have not touched Near-Earth Asteroids yet, which will become a redirect once the merge is complete. Wwheaton (talk) 09:53, 15 December 2008 (UTC)

I just noticed SAE1962 (talk) had done much more before. Apologies for clobbering your lead section. Wwheaton (talk) 10:03, 15 December 2008 (UTC)
 * Do we have everything we need from Near-Earth Asteroids yet? If we let it sit too long, it will be a target for constructive editors doing good edits, which we should avoid.  I vote for turning it into a redirect to NEO unless there is objection within a few days. Wwheaton (talk) 23:47, 23 December 2008 (UTC)

I have redirected the old Near-Earth asteroid article to this one. The old NEA talk page is preserved in the redirect page. Wwheaton (talk) 17:25, 29 December 2008 (UTC)
 * Thanks to Wwheaton and SAE1962 for time and effort to do the merge. It looks excellent! Ikluft (talk) 19:42, 29 December 2008 (UTC)

Missing Something?
I heard on some science show yesterday that there was going to be a very close approach in a couple decades, I think he literally said "closer than our communication satellites", and at that point we'd be able to observe closely enough to tell whether it was going to collide with us few decades after that. Anyone know what that's about? —Preceding unsigned comment added by 67.188.114.26 (talk) 04:08, 14 February 2009 (UTC)


 * I have moved this section to the end of the talk page, as latest-last is the standard ordering. Thanks. Wwheaton (talk) 07:41, 14 February 2009 (UTC)

October 8 2009 Indonesia
I am not sure where this should be addressed. I know this isn't 'near earth' because it did hit:

the explosion was due to an asteroid about 5-10 meters (15-30 feet) in diameter exploding in the air between 15 and 20 km (nine to 12 miles) above sea level. Nobody was injured as a result of the explosion which was equal to 30 – 50 kilotons of TNT or two to three times larger then the Hiroshima bomb.

Most interesting point about this in my opinion is that it wasn't even news worthy and scientists didn't even know about it until days latter.

Which we didn't even know if it was a broken up asteroid or not (meaning more could have come in and we wouldn't have known about it.)

http://www.universetoday.com/2009/10/30/asteroid-explosion-over-indonesia/

--OxAO (talk) 20:03, 1 November 2009 (UTC)

Exploration
Seems to me that this article focuses solely on the risks of impact. There's nothing about NEOs as an easy target for exploration. Ordinary Person (talk) 07:38, 10 December 2011 (UTC)

PHO and NEO numbers
As I was researching the subject I noticed that the PHO and NEO counts were the same on both wikipidia pages. Not looking further, I do not know if this page needs editing or that the page on PHO's needs editing.98.92.202.152 (talk) 20:38, 15 May 2012 (UTC)


 * See NASA Survey Counts Potentially Hazardous Asteroids (May 16, 2012)


 * Potentially hazardous asteroids, or PHAs, are a subset of the larger group of near-Earth asteroids. The PHAs have the closest orbits to Earth's, coming within five million miles (about eight million kilometers), and they are big enough to survive passing through Earth's atmosphere and cause damage on a regional, or greater, scale. -- Kheider (talk) 09:35, 17 May 2012 (UTC)


 * Yikes, you were right, the numbers being used in the article were quite dated, not well referenced, and not explained in any detail. -- Kheider (talk) 17:54, 17 May 2012 (UTC)

Plural versus singular form
In the family description: "The Atens, which have average orbital radii less than one AU (the average distance from the Earth to the Sun) and aphelion of more than Earth's perihelion (0.983 AU), placing them usually inside the orbit of Earth." the plural subject, Atens, have many different aphelia. So, it seems to me that aphelion should be changed back to the plural form. The same goes for a number of recent changes of perihelia to perihelion. Also there should be no period at the end of the family description since it is not a sentence. - Fartherred (talk) 15:26, 4 June 2012 (UTC)
 * Plural forms are now what they should be. I have decided that periods at the end of sentence fragments can sometimes reduce confusion.  - Fartherred (talk) 06:19, 6 June 2012 (UTC)

Size of potentially hazardous objects
"Objects that ..are smaller than about 150 m" are NOT considered potentially hazardous? The Chelyabinsk meteor has been estimated to have a dimension of ca 17m - and did considerable damage. Is there no chance that with a different composition or entry angle an object of this size might release its energy closer to ground (more destruction)? IS 150m really an universally agreed definition of "PHO"? Kipala (talk) 09:14, 18 February 2013 (UTC)
 * The technical definition of a PHO is an object that is estimated to be at least 100 to 150 meters in diameter. That is an object large enough to leave an impact crater and do severe regional damage. The Russian impactor would have been more-or-less harmless if it had not been for all of the flying glass. Nickel-iron asteroids only account for about 1-5% of the asteroid population, so a 50-meter nickel-iron impactor, like the one that created the 1km Meteor crater in Arizona would be 20-100 times less common. Nickel-iron asteroid come from the core of disrupted differentiated asteroids such as 9 Metis.  -- Kheider (talk) 10:46, 18 February 2013 (UTC)
 * Are you sure? Obviously the classification looks at direct impacts; I could not see anything calculating shock wave effects. Chelyabinsk had some broken walls and roofs (besides the glass windows) because the thing fell apart at 15-20 km height. What about dissolution some km lower? at 10 or 5 km height? No direct impact yet but surely far more damage. Is that physically not possible? And is this "direct impact" asessment really the internationally agreed method?? Kipala (talk) 13:19, 18 February 2013 (UTC)
 * It is really just about the estimated size of an object. The diameter of most near-Earth asteroids that have not been studied by radar or infrared can generally only be estimated within about a factor of 2 based on the asteroids absolute magnitude (H).
 * Yes, an airburst by a 85-meter impactor would be horrible if it occurred just above a populated region, but it would still only be regional damage. There is a reason military bombs are designed to burst above the ground rather than explode on impact. -- Kheider (talk) 14:04, 18 February 2013 (UTC)
 * And I believe someone got a concussion and a man got his fingers amputated by the shock wave (a metal door was involved). Though you have to draw the line somewhere. Sagittarian Milky Way (talk) 12:33, 19 February 2013 (UTC)

Impact Events
I blanked the section that was turning into a commemoration of recent airbursts and meteorite falls. This is about near-Earth objects. The correct article for that stuff is probably impact event. This will probably be opposed, some relevant guidelines are WP:NOTNEWS, WP:COATRACK, WP:RECENTISM. Geogene (talk) 17:35, 6 August 2014 (UTC)

Future Impacts
The "Future Impacts" section on 1950DA is not very accurate.

Here is a brief summary of the conclusions of the paper:

First, there is a 20 minute window of intersection. Uncertainty about whether it will impacts result from uncertainty of where it will be along its orbital path at the time - whether it will hit that window or not.

Close approaches in 2809 and 2806 amplify the uncertainty effects.

From his table 3, the main uncertainties listed are in
 * Solar oblateness, could be between 21 and 49 minutes
 * Planetary mass uncertainty for between 1.1 and -1.3 days
 * Yarkovsky effect, between +9.6 and -57.7 days

The Yarkovsky effect is the main uncertainty, and it could be reduced somewhat in 2032 but more likely in 2074 or 2105. It could be reduced also with ground based photometric effects, or, if we sent a spacecraft mission there, we could assess it accurately that way.

Also, for further future impacts, he says that a close encounter in 2880 would amplify the effects so much that prediction beyond that date is impossible at present.

Paper here: http://neo.jpl.nasa.gov/1950da/1950da.pdf

Robert Walker (talk) 13:26, 24 September 2015 (UTC)


 * Why are you reading a paper from 2002? -- Kheider (talk) 13:33, 24 September 2015 (UTC)


 * It's the paper cited in that section of this article, so it is what it is supposed to be summarizing, but as I just said, its summary is inaccurate.


 * The current summary of this paper is: "The next radar opportunity for 1950 DA is in 2032, and will pinpoint our knowledge of the orbit, but additional optical position measurements have already reduced the probability of a 2880 impact to 1 in 20 000."


 * But it doesn't say that at all. Can search for a more recent paper of course. See if anyone has done those photometric observations, good point. Robert Walker (talk) 13:46, 24 September 2015 (UTC)


 * I found a later paper from 2013: http://arxiv.org/pdf/1310.0861.pdf - but this object is already summarized well in (29075)_1950_DA - could just summarize what they say there. Would be better than what it has. I'm not sure if the suggestion of refining its orbi via radar measurements is worth mentioning as it's from a 2002 paper, as you say, and not mentioned in the later papers. Robert Walker (talk) 14:13, 24 September 2015 (UTC)


 * Given the last observation was in 2014, you really need to use something more recent than 2002. It was been known since 2013 that 1950 DA is not really a concern for 2880. -- Kheider (talk) 14:16, 24 September 2015 (UTC)


 * I see the above discussion had no result on the article. I have now updated the text on 1950 DA to reflect the references more faithfully and to also include the latest data. Rontombontom (talk) 12:45, 8 November 2017 (UTC)

Angular momentum and risk of capture
Just like thermal neutron capture by atomic nuclei, bolide capture by planetary gravity is an inverse function of relative speed. Actually of course gravitational capture is the more widely understandable phenomenon. The missile's angular momentum relative to the centre of the planet is constant, so the product of the outer radius of the atmosphere, times the escape speed at that radius, is the upper limit for the object being captured by gravity, unless it is heading directly inside that radius. It is one thing to say "Object X came within N Earth radii of the surface", and more informative to add how fast it was going relative to the planet. If an object as far from Earth as a TV broadcasting satellite in "geostationary" orbit is moving tangentially at a higher speed than such satellites, there is nothing to worry about. But there is some fraction of that speed which means it will be captured and crash. If it were twice as close, moving more than twice as fast, we are still safe! Which is why the probability of a Kuiper belt object colliding with Earth is remarkable small. By the time it has fallen through that much solar gravity, its speed is tremendous, so the gravitational capture area is correspondingly small. Nevertheless, in the first billion years of our planet's existence, after it had cooled just enough, the atmosphere presumably was brought here by such comets!DaveyHume (talk) 13:59, 16 August 2016 (UTC)

Problems with text on approach of 4581 Asclepius (1989 FC) in 1989
The text quotes an oft-repeated line that 1989 FC was "...passing through the exact position where the Earth was only 6 hours before." This is not correct. The earliest reference to such a claim that I have been able to find is in an AIAA position paper from 1990 In fact, 1989 FC was about 400,000-500,000 km above the ecliptic plane at the time of passing from inside the Earth's orbit to the outside, having passed up through the ecliptic plane several days earlier. In addition, 1989 FC arrived at the "crossing point" (at least in a 2-dimensional sense) about 5 hours ahead of the Earth, not after as the incorrect story maintains. I computed my data using SOLEX 12.0 but I would expect that JPL's HORIZONS system would also give the same result. I also don't think the final sentence of the paragraph is correct either. It reads: "It attracted widespread attention as early calculations had its passage being as close as 64,000 km (40,000 mi) from the Earth, with large uncertainties that allowed for the possibility of it striking the Earth." Articles in the LA and New York Times quoting a NASA press release clearly indicate a pass of around 500,000 miles, there is no reference to the possibility of a closer pass with uncertainty allowing an Earth impact. I believe the rest of this sentence is actually referring to the fuss around 1997 XF11 in March 1998 regarding its close approach in 2028. The reference quoted is an article in the Boston Globe by Brian Marsden of the Minor Planet Center giving his version of the events in the 1997 XF11 story and only includes a brief mention of Asclepius' pass in 1989. I think the final sentence should be changed and the LA Times or New York Times article referenced instead. --Ptastro (talk) 13:03, 8 May 2017 (UTC)


 * Why haven't you done the edit yourself? I have now done it, and also added the 1997 XF11 story, along with other milestones in NEO awareness, into the first section. Rontombontom (talk) 21:58, 29 October 2017 (UTC)

Major re-edit for good article nomination - delete Notable objects section?
I started a major re-edit of the article with the aim to bring it into shape for a good article (GA) nomination. What I have done so far:
 * I have re-written the intro as more of a summary of the article (as per MOS:LEAD), moving passages on details into the main body of the article.
 * Using mostly stuff removed from the into, I added a Definitions section.
 * The History of human awareness of NEOs section was a stump. So I moved/added landmark discoveries and pre-Sentry-Risk-Table asteroid impact scares.
 * I merged the similar Highly Rated Risks and Future Impacts sections, while reviewing every detail of the impact risks mentioned.
 * I updated all stats.
 * In the Close approaches section, I restricted the selection to truly significant approaches within the Moon's orbit. With dozens of close approaches each year, there is no point in adding a reference to any reported event.
 * I checked almost all references and updated citations where necessary (four remain).
 * In line with MOS:DATEUNIFY, I unified the date format in the article and reference publication dates (to British English, e.g. "10 November 2017") and reference access and archive dates (to the YYYY-MM-DD ISO format).

Work I still intend to do:
 * Add some influenced popular culture (if I find good references).
 * Add a paragraph or section on Earth's quasi-satellites, horseshoe/tadpole orbit asteroids, Trojans and temporary satellites.
 * Add a paragraph or sub-section on Sun-orbiting space debris.
 * Given that most of the article discusses NASA-related stuff and most references are American, revise dates again to American English ("November 10, 2017") in line with MOS:DATETIES.
 * Change cite web citations to cite news where appropriate.

Finally, there is one major change I ask other editors about. I think the "Notable objects" section is a random list and completely useless. So I would delete it altogether (save for the image which I'd move to the previous section). Any objections? Rontombontom (talk) 09:53, 10 November 2017 (UTC)


 * The last two on my to-do list are now done. But I see the section on NECs also needs expanding.Rontombontom (talk) 14:31, 10 November 2017 (UTC)


 * Just for the record: I did delete the "Notable objects" and done all the work indicated above before the GA nomination. Also, added a Meteoroids section, added a paragraph on NEA moons, updated diagrams and ordered images, put the orbital classification of NEAs into its own sub-section, moved the two predicted impacts from the Close Approaches section and added a paragraph on extraterrestrial impacts into the Impacts section, and added on-going missions and space mining to Exploratory missions. Rontombontom (talk) 11:48, 23 January 2018 (UTC)

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Re-edit of Impacts
The first two paragraphs of the Impacts section dealt with the frequency of impacts. Editor N2e edited it with the edit summary "copyedit to reflect in prose that these are based on models, not historical or empirically observable facts, per source. Moreover, there are other sources with different models". I admit I overlooked this section during my recent major re-edit for GA. Checking the sources now, I felt both the new wording and what was left unchanged is problematic, and thought the two paragraphs need a total re-write. Here I give my reasons in more detail than fit for the edit summary.

First, I thought the different bases for impact frequency estimates is worthy of being stated explicitly. I feel the juxtaposition of "models" and "historical or empirically observable facts" is unfortunate, because the models are based on observable facts like crater density on the Moon, and even using direct observations of impacts in historical times need models to extrapolate for the parts of the Earth without observers (or surviving observation records) and to estimate impact energy.

Second, the frequency estimates aren't just predictions about the future, but estimates about the frequency in the recent past. Beyond the wording, I realised there was an unstated underlying issue: the assumption that the rate of impact is steady, which as per the sources is actually based on observations (analysis of lunar craters). So I thought this is worth to be mentioned explicitly, too.

Third, the examples for impact frequency for various asteroid sizes was an unholy mess with several sources. I chose to keep the figures derived with the impact effects calculator but condense them into a single sentence, to give a general idea of how quickly the frequency drops with increasing size; and add the rest to indicate variation. I'm not entirely happy with the impact effects calculator figures, because it borders on OR: in the source, the frequency estimates are tied to impact energy (the megaton numbers), but the connection to asteroid size requires an assumption of average impact speed and asteroid density. The fact that the figures assumed by the original editor who knows how long ago (17 km/h and 2600 kg/m^3) are okay is only clear from reading the journal article detailing the model (which I added as source). Any editors against keeping this, or with a better alternative source explicitly stating frequencies for a wide range of asteroid sizes?

Fourth, I thought the original second paragraph included an unnecessary extrapolation into the next billion years (also on the verge of OR) and a too detailed discussion of the mass loss of the asteroid main belt (more fit for ad already discussed at length in the "Near-Earth asteroids" section). What I saved from this I merged into the new sentence on the steadiness of the impact rate. Rontombontom (talk) 20:52, 19 March 2018 (UTC)

wrong link
In paragraph 3.3 Near Earth comets, the term "age of science" links to a book Dutchy45 (talk) 11:50, 22 May 2018 (UTC)

Up to date?
Since 2018 UA has passed the earth on October 19, 2018, it must at least be one more asteroid which is known. --Tanneneichhorn (talk) 15:09, 26 October 2018 (UTC)

Article opening sentences have issues - Bolded below
A near-Earth object (NEO) is any small Solar System body whose orbit brings it to proximity with an Airbus A350-1000 equipped with Trent XWB engines. By convention, a Penguin Lord’s body is a NEO if its closest approach to the — Preceding unsigned comment added by 99.14.172.250 (talk) 01:58, 4 March 2020 (UTC)

amount?
There reads: "There are over 26,000 known near-Earth asteroids" Somehow, the pie-chart have 5 sections of which numbers only sum up to 19,200 objects, So what are the 7,000 which are missing there? 109.240.153.46 (talk) 19:28, 24 September 2021 (UTC)
 * I assume the pie chart had not been updated in a while. Done. -- Kheider (talk) 20:00, 24 September 2021 (UTC)

is 594913 ʼAylóʼchaxnim really a NEA?
It fits the definition we give, but isn't what people would think of as "near". Should the definition be revised? — kwami (talk) 10:49, 22 December 2021 (UTC)
 * It fits the definition the MPC/NASA use. People think lots of weird *stuff*. 99% of the PHAs are not really worth talking about. Being a NEO is just a generic category. It does pass within 52 million km of Earth. -- 15:23, 22 December 2021 (UTC)

Definition of Near-Earth comet
The article says that JPL's CNEOS even restricts its definition of NECs to short-period comets. That statement is confusing. Not only is it hidden deep within the body of the text, and requires the reader to look up the definition of short-period comets to understand it; it also gives the impression that JPL are the only ones who use this definition. ESA's NEOCC does so as well, so why do we make a distinction? Renerpho (talk) 02:09, 3 October 2023 (UTC)