Talk:Near-Earth object

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Sky not currently surveyed[edit]

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 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. — 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[edit]

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[edit]

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)


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[edit]

with only 1.4 lunar distance away and 500 meters big. classified as;cad=1#cad -- —Preceding unsigned comment added by Manchurian candidate (talkcontribs) 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[edit]

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)

Green tickY 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)
Green tickY 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[edit]

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?[edit]

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 (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[edit]

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

Text copy-and-pasted from Impact event[edit]

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[edit]

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 21st 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.[1]

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.[2][3][4] Bettymnz4 (talk) 03:00, 7 April 2010 (UTC)


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[edit]

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. (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[edit]

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[edit]

"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[edit]

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[edit]

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:

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: - 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)