Talk:99942 Apophis

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Untitled[edit]

Misleading Lead-in[edit]

The lead-in section of this article is misleading

"that caused a brief period of concern in December 2004 because initial observations indicated a small probability (up to 2.7%) that it would strike the Earth in 2029."

It should say has continued to cause concern from December 2004 until recently and then you can use this article http://www.foxnews.com/scitech/2011/02/10/doomsday-determined-asteroid-apophis-strike-earth/ as evidence for example. Don't belittle the situation.212.219.231.1 (talk) 12:59, 11 August 2011 (UTC)

Russian plans[edit]

This article just popped up this morning. Anyone interested in editing this article may find it interesting and may be able to incorporate the information. http://news.yahoo.com/s/ap/eu_russia_asteroid_encounter 98.215.128.112 (talk) 17:55, 30 December 2009 (UTC)


My apologies. Apparently someone has already found and posted the article below. 98.215.128.112 (talk) 17:57, 30 December 2009 (UTC)

Somebody should add this to the article. http://news.yahoo.com/s/ap/20091230/ap_on_re_eu/eu_russia_asteroid_encounter I don't know how and don't want to mess it up. —Preceding unsigned comment added by 67.175.127.171 (talk) 15:35, 30 December 2009 (UTC)

Perminov's statements (in the linked interview) indicate that he was not aware of the low probability of impact, and do not reflect any official decisions by Roscomos - so there aren't really any 'Russian plans' yet. I recommend that we leave this out of the article for the moment. Also please remember that this is the talk page for editing the article about Apophis, not a forum for personal opinions (I removed those posts). Michaelbusch (talk) 19:20, 30 December 2009 (UTC)

I agree and have added it. The news story does not talk about Russian Plans, it merely talks about a statement to look into a possible mission, i.e. it may make plans and is considering that now. This is very relevant and worth reporting, as it comes from the official Russian Space Agency. Its not up to us to interpret that they "are not aware of the low probability." That is not relevant.76.14.42.191 (talk) 20:31, 30 December 2009 (UTC)

Since you insist, 76.14.42.191, I'll let it stay. But I have rephrased the text to be more accurate. Note: I do have a personal bias with this article. I am a member of the team that has been refining the impact probability estimates for the past several years. It is very relevant to me that Perminov has apparently been mis-informed about our work. Michaelbusch (talk) 20:39, 30 December 2009 (UTC)

My 2 cents. -- Kheider (talk) 20:54, 30 December 2009 (UTC)


Thanks for letting it stay and I have no problem with your re-wording of my addition. I can see you are close to the subject, and you are probably right that Perminov has been mis-informed about your work. However, we as editors here need to be careful to merely report and not interject our bias, even if that bias is well informed on the subject. Perhaps Perminov is aware of the probabilities but doesnt want to take any chances, or perhaps its PR reasons that they are talking about this. Lets wait to see if other respected and notable people speak about this latest development, but lets not fail to report on it.76.14.42.191 (talk) 20:56, 30 December 2009 (UTC)
Even if the impact is not very likely, this mission could make a lot of sense. This asteroid would offer a perfect opportunity to practice deflecting a body headed for Earth, so if in a few decades or centuries another body appears that will actually hit Earth, invaluable experience gained during the practice mission will make deflecting it that much easier and cheaper. In other words, since we practice responding to disasters all the time, we could do so here as well. Sourcelat0r (talk) 23:04, 30 December 2009 (UTC)

2013 Pass of Apophis[edit]

Novosti 2009-02-25 (http://en.rian.ru/analysis/20090225/120298367.html) says "In 2012, Apophis will pass close enough to Earth, enabling scientists to more accurately calculate its 2029 orbit." If so, ISTM worth giving date and distance of that pass, and of any other comparatively near passes before the important ones. 82.163.24.100 (talk) 18:59, 25 February 2009 (UTC)

See Talk:99942_Apophis/Archive_2#2016_Venus_encounter for more details.. -- Kheider (talk) 19:24, 25 February 2009 (UTC)

Some minor details in the naming section[edit]

The statement of Apophis being the most persistent Stargate villain, although in the article Goa'uld characters in Stargate is stated that Ba'al is the longest-running villain in Stargate show. 195.39.74.163 (talk) 17:21, 13 July 2009 (UTC)

The article cites a supporting source. Because of this, the article should be read as asserting that

Although the Greek name for the Egyptian god may be appropriate, Tholen and Tucker — two of the co-discovers of the asteroid — are reportedly fans of the TV series Stargate SG-1. The show's most persistent villain is an alien also named for the Egyptian god." (Supporting source: Bill Cooke (August 18, 2005). "Asteroid Apophis set for a makeover". Astronomy Magazine.  Unknown parameter |urldate= ignored (help).)

As that cited supporting source does indeed support the assertion, the article should not be changed to make a contrary assertion; though information about contrary assertions made by other sources (with those sources being cited, of course) might be added to the article. Or, alternatively, perhaps this bit of trivia might be left out of the article. See WP:V, WP:CITE. Wtmitchell (talk) (earlier Boracay Bill) 23:38, 14 July 2009 (UTC)
Could be that at the time of the discovery, The show was still in production. Stargate SG1 ran 10 seasons, and Apophis was a major antagonist for at least the first 4 (possibly 5 or more), while Baal (spelling?) was introduced later on (5th season perhaps?) 24.235.198.91 (talk) 23:25, 2 January 2010 (UTC)
I'm opposed to mixing fiction as a source kinds of references into this article, as it will dilute the perceived quality to many readers. It is more-than-enough to state that the etymology traces to greek, and a rather annoying and irrational distraction to speculate that the discoverers are fans of a tv show; even if this were true, the name of the asteroid is irrelevant to its orbit and properties. The discussion doesn't belong here, but belongs on the page about the tv show -- 99.233.186.4 (talk) 13:32, 16 April 2010 (UTC)

Aldrin Manned Mission Plan[edit]

During the lecture for the 40th Apollo 11 Anniversary, Buzz Aldrin proposed a manned mission, here's a powerpoint slide of his which shows it, if someone wants to add something to the missions section: http://www.nasawatch.com/archives/2009/07/buzz_aldrins_on.html —Preceding unsigned comment added by Jafafa Hots (talkcontribs) 10:43, 20 July 2009 (UTC)

Which is it?[edit]

"Apophis’s brightness will peak at magnitude 3.3, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be ~2 arcseconds, so that it will be barely resolved by telescopes not equipped with adaptive optics."

"On that date, it will become as bright as magnitude 3.3 (visible to the naked eye from rural and some darker suburban areas, visible with binoculars from most locations"

According to the Apparent_magnitude page, the second quote would appear to be the correct one. Does someone want to take a shot at fixing this? —Preceding unsigned comment added by 76.21.3.245 (talk) 12:53, 14 August 2009 (UTC)

The resolving power of a telescope has nothing to do with the limiting apparent magnitude. These are separate characteristics. It is the difference between seeing an object (magnitude) and resolving it as a disc. -- Kheider (talk) 15:08, 14 August 2009 (UTC)

1 in 233,000 chance[edit]

I rv'ed an edit showing a 1 in 250,000 chance of a collision. The auto generated link at NEO does show the odds as only 1 in 233,000 (2036-04-13.37; 4.3e-06), but since it is an auto generated page I think it is better if we stay with a human created reference. Besides there have been no new observations of the asteroid since 2008-01-09. -- Kheider (talk) 18:31, 7 October 2009 (UTC)

As per an October 7, 2009 NASA Release, chances of impact in 2036 have been recalculated to be 1 in 250,000. So, I undid your edit and added the reference. Darry2385 (talk) 19:04, 7 October 2009 (UTC)
Ah good. Nice to know the automated program is accurate. :) -- Kheider (talk) 19:28, 7 October 2009 (UTC)
Still better odds than winning the lottery —Preceding unsigned comment added by 98.231.242.193 (talk) 21:28, 24 February 2010 (UTC)
Looks like the miscalculations continue. The link on Jan 10 2013 says 7.5e-06 chance, which equates to 1 in 133,000. Anarchofascist (talk) 08:37, 10 January 2013 (UTC)
Looks like someone does not bother reading the text. The risk in the year 2036 is 1.4e-07 which is 1 in 7,143,000. The cumulative risk from 2036 to 2105 is 1 in 133,000. -- Kheider (talk) 12:34, 10 January 2013 (UTC)

Easter Sunday[edit]

The event of 2036 will occur on Gregorian Easter Sunday (Orthodox Easter Sunday will be a week later) - that seems worth mentioning.

Could there be a table of all nearest approaches this century, with brief details including miss distance, visible magnitude, GMT of pass, terrestrial nadir of pass, with uncertainties?

82.163.24.100 (talk) 09:57, 8 October 2009 (UTC)

NEODyS Close Approaches (ref #13) has the info you are looking for. -- Kheider (talk) 10:11, 8 October 2009 (UTC)
You miss the point. Such a table, in a more user-friendly form, should be in the Article. Moreover, the NEODyS table includes only some of the above, and gives later figures with what looks like unreasonable precision. 94.30.84.71 (talk) 10:02, 13 May 2011 (UTC)
The Article indicates a pass or impact at 2036-04-12 - but NEODyS has nothing that year. Why the discrepancy? 94.30.84.71 (talk) 10:22, 13 May 2011 (UTC)
Unless the asteroid passes through the unlikely 2029 gravitational keyhole, the nominal close approach of 2036 will be on 2036-Mar-26 at a distance of 0.324593 AU (48,558,400 km; 30,172,800 mi). -- Kheider (talk) 13:14, 13 May 2011 (UTC)

────────────────────────────────────────────────────────────────────────────────────────────────────Apophis will then come no closer than about 14 million miles — and more likely miss us by something closer to 35 million miles. -- Kheider (talk) 14:54, 10 January 2013 (UTC)

Effect[edit]

Article includes "An impact several thousand kilometres off the West Coast of the US would produce a devastating tsunami." True, no doubt; but why the parochiality? An impact off North Brazil would devastate the northern coast of South America, the Caribbean, the African coast, etc. Better to say something like "A [deep-]sea impact would devastate coasts up to thousands of kilometres away". 94.30.84.71 (talk) 10:22, 13 May 2011 (UTC)

The references says, "The most likely target, though, is several thousand miles off the West Coast". -- Kheider (talk) 13:24, 13 May 2011 (UTC)

Impact risk path[edit]

I suggest that this image be removed, since it illustrates as possible as event that has now been ruled out. gpeterw (talk) 12:35, 1 March 2013 (UTC)

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

I have a question. According to the impact risk there is a path that covers a 20 hour earth turn rate. (I would think the curved path indicates this is a time lag due to how the earth is turned).

At the speed the earth is revolving around the sun how can predictions of the accuracy they are claiming be made? Just wondering. —Preceding unsigned comment added by 207.160.238.250 (talk) 16:08, 21 December 2009 (UTC)

Using Newtonian mechanics, the errors in the known trajectory of Apophis result in slightly different arrival times and impact points. If we knew the exact orbit of Apophis we would know when and where it would hit. When Apophis gets very close to the Earth there will be significant perturbations to the asteroid. -- Kheider (talk) 21:45, 21 December 2009 (UTC)
This seems to be based on this,particularly this and this cited there. Wtmitchell (talk) (earlier Boracay Bill) 01:18, 1 January 2010 (UTC)
It should be noted that this path prediction for a 2036 impact is based upon calculations with an estimated mass from a theoretical model which cannot be accurate without a much better understanding of the exact metalurlgical and geological make-up of Apophis. Further, the 2029 path may well lead to a gravitational deflection, and/or an increase or decrease in velocity, which cannot be accurately calculated without knowing the specific mass of Apophis, and which may completely alter the illustrated path and/or time of the 2036 encounter. I fail to see how this illustration holds any relevence whatsoever. There cannot be any significant degree of certainty until after 2029. The distance Apophis travels means that even slightest error in estimation could convert to a huge change in predicted orbital path.
There are predictions for both 2036 amd 2037 (for an estimated 7 year orbit?). The 2029 orbit is theorized to pass close to a "keyhole" with a 2000ft diameter, Apophis is estimated at 1300ft in diameter, the 2006 prediction has a 2000 mile margin of error...and has anyone considered loss of mass due to outgassing and such? More estimates equal greater margins of error, regardless of scientific method or the theories applied. There is any given number of stellar bodies along the Apophis orbit which could introduce variables that could never be predicted without actually trailing Apophis through it's entire orbit.
There is no need to label this illustration as the prediction for a "Path of Risk" for a period of 20 hours on October 13, 2036, alarming people who may be near to this path for nothing... The illustration does however reflect the possible path of a non-geostationary sattelite traveling counter to the earth's rotation, and is an excellent example of exactly that. Wikipedia is not a soapbox for those looking to justify or finance a trip to space. 24.235.198.91 (talk) 22:10, 2 January 2010 (UTC)
The plot is the intersection of the uncertainty region (points where Apophis can be at that time given our current knowledge of its orbit and all possible perturbations) and the Earth. That is what a 'path of risk' is. 24.235.198.91, I don't have the time to explain all of the details of our trajectory prediction (see Jon Giorgini and Steve Chesley's papers for that), but please understand that this is simply a way to represent the potential impact and nothing more. Regardless of where the path of risk plots on the Earth, the trajectory prediction gives a 0.0004% chance that Apophis will actually be along that line at the time that the Earth is there. Michaelbusch (talk) 19:23, 5 January 2010 (UTC)

Risk path, 2036 or 2037?[edit]

This image is used on both elsewhere on this talk page and on the main article, as well as on a few other articles. The filename File:2037 Apophis Path of Risk.jpg indicates that it charts the path of risk in 2037, but the descripion always cites 2036. As 2036 is the greater risk, it seems likely that the file was misnamed. Can anyone confirm the correct year for this image and correct its name or usage? —Preceding unsigned comment added by Sparr (talkcontribs) 05:00, 31 December 2009 (UTC)

It is certainly meant to represent the 2036 keyhole risk (NEO at JPL). -- Kheider (talk) 05:41, 31 December 2009 (UTC)

Impact calculations: solid rock vs. rubble pile[edit]

I was wondering how the impact calculations would differ if the asteroid Apophis turns out to be a big rubble pile, its center of mass would change during close approach and rotation rate? Also if Apophis turns out to be a rubble pile that breaks apart on close aproach to Earth,How much more of a threat would it be to multible geostationary satellites? Jalanp2 (talk) 18:26, 8 November 2009 (UTC)

Apophis in popular culture[edit]

"In the soon to be released id Software game Rage, the game-play takes place on Earth years after an impact by Apophis.[29]"

Does anyone else think this section is utterly unnecessary (to be kind) in a serious article about Apophis?Rodney420 (talk) 18:37, 12 January 2010 (UTC)

These sections appear in tons of articles. Most of the time the content is rubbish. I think that's true for this particular section also. I've removed it based on the idea that we're trying to develop a quality encyclopedia and "gamevideospot.com" doesn't satisfy the requirements for using reliable sources. Good catch Rodney. Dawnseeker2000 20:31, 12 January 2010 (UTC)

How wide is the "path of risk"?[edit]

In the section Possible impact effects, the article says:

The result is a narrow corridor a few miles wide, called the path of risk, and it includes most of southern Russia, ...

This is incoherent. If the path of risk is only a few miles wide, it cannot possibly cover "most of southern Russia", and indeed not more than a few thousand square miles. Someone with better understanding should correct this. —Dominus (talk) 18:00, 6 April 2010 (UTC)

I reworded that bit. Wtmitchell (talk) (earlier Boracay Bill) 04:53, 7 April 2010 (UTC)
Thanks very much. —Dominus (talk) 15:04, 7 April 2010 (UTC)

Basic Data[edit]

Curious about the dimension info in the Basic Data section. 1) There's a historical statement that there was an estimate of 450 meters at an unspecified time. 2) In the same sentence, an estimate of 350 meters, without stating that this is the most recent and accurate estimate (is it?) 3) In the summary sidebar, an estimate of ~270 meters, with a References link to a JPL database and a suggestion that the most recent observation in the database is 2008.01.09. I was looking for a statement of highest confidence for the dimensions of Apophis relative to most-recent observations, and am not sure whether I found it. Mvsmith (talk) 14:01, 10 November 2010 (UTC)

Orbit Estimation Methodology[edit]

Is a Bayesian or some similar statistical method being used to estimate the object's orbit? Is a standardized method being used by all of the observers presenting estimates of the probability of an Earth impact? (What is the apples/oranges potential in the numbers presented?) Are all of the observations obtained to date used to form a population of observations or are the estimates based on the short arcs defined by each of the sets of observations listed in the article? It would be pertinent to mention the methodology used in each case or at least point the reader to a general discussion of orbit estimation methods used by astronomers. Virgil H. Soule (talk) 07:35, 9 February 2011 (UTC)

Orbit Guesswork[edit]

There is no orbit info that I can see in this article for the Apophis asteroid. The articles for Ceres and other larger asteroids show their orbits and also considerable eccentricity in their orbits. Although most Asteroids orbit the Sun in the "Asteroid belt", their paths are also affected by gravitation of Jupiter and Mars and other planets of the Solar system, the paths also affected by thousands of other asteroids gravitation and possible collisions. Although Astronomers track thousands of these objects, there is a margin of error in each track that is multiplied by gravity's positive coefficient (the path of a Apophis sized body is affected by Jupiter and Mars and Earth and Venus but Apophis also affects them and other Asteroids and their altered paths affect Apophis and so on). Other unknowns in Apophis' orbital path range from pressure of Solar wind (Solar flares) to Yarkovsky effect. Gravitation or collision can break up an object, close approach to Earth could fracture Apophis (Jupiter did that to an impacting Comet), sending smaller but still lethal pieces at us. Truth is we still plan on in course correction for our space flights. Radio beacons on the ten thousand objects we now track sounds good, not so when you consider the rate of air traffic control accidents with only a few planes in the sky. And wasn't that figure of a hundred thousand asteroids big enough to wipe us out? Shjacks45 (talk) 09:32, 9 February 2011 (UTC)

The orbit of Apophis is listed in the infobox. Apophis is largely only affected by the Sun+Earth+our Moon+Venus over a short 200 year simulation. The orbit of this asteroid is not known well enough to reliably calculate out beyond ~200 years. The affect Apophis' mass has on other bodies can be ignored in the simulations and Apophis can be treated as massless. If you are truly anal you may also need to consider Earth's exosphere for very close approach simulations. -- Kheider (talk) 11:36, 9 February 2011 (UTC)
──────────────────────────────────────────────────────────────────────────────────────────────────── See the 99942 Apophis (2004 MN4) orbit simulation from JPL using a java applet at http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=99942;orb=1. Wtmitchell (talk) (earlier Boracay Bill) 04:27, 10 February 2011 (UTC)
Warning!: That is a 2-body (Sun+Asteroid) simulation and can not be used to reliably predict the trajectory of Apophis during/ after a close approach to a planet (3rd body). -- Kheider (talk) 18:20, 16 November 2011 (UTC)

A space test[edit]

Just have read the chance part here; of course it would go perfect, as if in its trajectory it will only pass earth, but there is so many more out there. Such an object hitting the moon might be wrong too, depending on it internal makeup. Why not enter this rock as soon as possible use solar sails, or bombs and get it out of our path ?. Seams to me better then visiting the Moon or Mars, so i think this is a nice space test at least rusia takes it serious. (but probaply lack funding). —Preceding unsigned comment added by 84.107.161.119 (talk) 13:12, 11 March 2011 (UTC)

There is no reason to worry about it until 2013 when we know the trajectory better. Guessing is never good science. -- Kheider (talk) 19:27, 11 March 2011 (UTC)

NOT A FORUM

Stabilize Orbit for Luna II?[edit]

With a bit of calculations and some rockets out there they might be able to change the trajectory into a stable orbit around the earth, and close enough to be readily used as another Space Station. If it were to have viable resources within it, then the hollowed mining shafts can easily be used for living space when no longer being worked. Not only that, but the shell of the Asteroid itself would be a perfect shield against Micrometeorite impacts. I think it's a good idea, but I don't know if anyone is seriously considering the project. 207.216.58.59 (talk) 08:16, 2 September 2011 (UTC) Yet another dumb idea. We do not yet have the technology to destroy the asteroid should something go wrong with this dangerous experiment of capturing another small moon. It sure would be difficult to explain to the country it lands on by mistake why we purposely altered its orbit to study it, rather than deflecting it into the sun, if we could even do that.66.176.3.97 (talk) 03:46, 25 July 2012 (UTC)

Not a dumb idea at all.
An asteroid captured into a stable orbit would be very valuable both as a laboratory for research of asteroids and space in general and as an orbital platform.
As for the "should something go wrong" argument - technology needed for anchoring an asteroid in a stable orbit is by definition more advanced and precise than technology needed to simply deflect or destroy it.
Also, 99942 Apophis has a diameter of about 270 meters, meaning that should push come to shove it could be simply nuked away.
A 20-30kT device ("Fat Man" dropped on Nagasaki was 21kT) would obliterate it, as a 20kT ground detonation leaves a crater ~193 meters wide. 89.146.181.82 (talk) 04:57, 22 August 2012 (UTC)

2029 close approach pictures[edit]

The images shown for the 2029 close approach give a false impression of the current (March 2012) uncertainty. The images are those produced for the JPL news release in February 2005 (http://neo.jpl.nasa.gov/news/news149.html). The white bar showing the range of positions is much too large to represent the current (March 2012) uncertainty. Mind you, I haven't been able to find an easily accesible better image. The following link (http://lesia.obspm.fr/semaine-sf2a/2011/proceedings/2011/2011sf2a.conf..0629B.pdf) discusses observations made in March 2011 (there have been even more recent observations reported to the Minor Planet Center) and shows the uncertainty ellipse on the 2029 b-plane and its relation to the keyholes for various impacts in future years. Figure 3 in that publication shows how the 3-sigma ellipse on the b-plane has shrunk to 27 km x 140 km and is centred approximately 1800 km from both the 2036 and 2037 key holes. — Preceding unsigned comment added by Pdthomas23 (talkcontribs) 12:29, 1 March 2012 (UTC)

New estimate – mass[edit]

Now that there is a new size estimate, which ups the mass estimate by 75%, what should we do with the mass value in the infobox? --JorisvS (talk) 18:14, 9 January 2013 (UTC)

The biggest problem here is that the density is still an unknown so any crude mass estimate can be off by a factor of 2 or 3. -- Kheider (talk) 18:29, 9 January 2013 (UTC)

Close approaches[edit]

The date for the 2029 and the 2036 passes are both listed as April 13. Is this a coincidence or a typo? Listing the 2029 date as Friday the 13th is a superstitious reference rather than a scientific one. The day of the week wouldn't normally be included for other days such as Monday the 8th for example. Shouldn't this trivia be moved closer to other popular culture items such as songs mentioning the asteroid? 22yearswothanks (talk) 18:02, 10 January 2013 (UTC)

The potential impact in 2036 would also be April 13, but the nominal solution shows the closest approach of 2036 as occurring around 23 March 2036. Thus Apophis and Earth will not be in the same place at the same time in 2036. -- Kheider (talk) 18:21, 10 January 2013 (UTC)
The phrase closest approach has a more NPOV connotation. Impact tends to promote a worst case scenario that it will hit with the word potential giving wiggle room in the meaning. Even the higher early estimates were far less than 50%, making it always more likely it wouldn't hit. 22yearswothanks (talk) 18:26, 12 January 2013 (UTC)
Potential impacts is common terminology and is more accurate. -- Kheider (talk) 18:53, 12 January 2013 (UTC)

Updating Needed[edit]

JPL/NASA have seemingly ruled out impact for 2036, with closest approach being 19,000 miles.

http://www.jpl.nasa.gov/:

I think many parts of the article might need to be rephrased in past tense. Also, in the section "History of Impact estimates" it was stated "Apophis will then come no closer than about 14 million miles — and more likely miss us by something closer to 35 million miles.[29] " These distances are not correct. --RichG (talk) 17:21, 12 January 2013 (UTC)

The statements are not really out of date. The JPL Sentry Risk Table is current as of the 2012-Dec-29 observation arc. Goldstone observations are still on going and have not yet been fully submitted. Until Goldstone observations are complete the uncertainty in the trajectory will keep shrinking. The statement, "Apophis will then come no closer than about 14 million miles — and more likely miss us by something closer to 35 million miles" was written Jan 9th and refers to the 2036 passage. The statement, "comes no closer than 19, 400 miles (31,300 kilometers) above Earth's surface." was written Jan 10th, but refers to the 2029 passage. The nominal solution (even using the less detailed 2012-12-29 observation arc) has Apophis passing 0.38AU from Earth on 2036-Mar-23. By 2036-Apr-13 Apophis will be 0.41AU from Earth. Even in 2011 the nominal solution had Apophis passing 0.32AU from Earth on 2036-Mar-26. -- Kheider (talk) 19:12, 12 January 2013 (UTC)

Impact[edit]

I know an impact is ruled out but this line grabbed my attention. "A later, more refined NASA estimate was 880 megatons, then revised to 510 megatons.[3]" The link given says 7.5e+0.2MT, I don't know if I understand correctly, probably not but that's 7.5 megatons no? Using the site Impact: Earth! and putting the data of Apophis gives and impact yield of 6.2MT, was the article vandalized or something? Mike.BRZ (talk) 21:00, 22 February 2013 (UTC)

Forget it, I used the Impact: Earth! site wrong and I'm sure I don't understand what 7.5e+0.2MT means. Mike.BRZ (talk) 21:11, 22 February 2013 (UTC)
Thank you for the question. That leading sentence did need cleaning up. The kinetic energy of Apophis when it makes atmosphere entry (Vimpact) is simply a function of different diameter estimates. Obviously the larger Apophis is, the more energy it will come in with. "7.5e+02 MT" is 750 Mt when you move the decimal place over 2 places. -- Kheider (talk) 21:48, 22 February 2013 (UTC)
This caught my interest when it popped up on my watchlist.
  • First, Mike, "7.5e+0.2MT" is a geeky way of saying "750 megatons" (of energy) or, possibly, "750 metric tons" (of mass).
  • The quote from the article wikilinked above doesn't appear in the current text. Mike's comment was dated 22 Feb; I searched article versions back to 18 Feb version) for "510 megatons" without success.
  • The link in the article to 99942 Apophis (2004 MN4) Earth Impact Risk Summary source cited was dead. I've fixed that.
  • The NASA web page pointed to by the repaired link estimates the mass of 99942 Apophis as 2.7e+10 kg (27 million metric tons), and its energy as 5.1e+02 MT (510 megatons).
  • The article said, "The Sentry Risk Table estimates that Apophis would make atmospheric entry with 750 megatons of kinetic energy." As mentioned, the data in th cited source (as repaired) said 510 megatons. I've fixed that.
Wtmitchell (talk) (earlier Boracay Bill) 01:27, 24 February 2013 (UTC)
Why are you not using the current Sentry data? The wayback archive uses an estimated size of 270 meters (510 Mt). The new estimated size is 330 meters (750 Mt). -- Kheider (talk) 01:31, 24 February 2013 (UTC)
Because http://neo.jpl.nasa.gov/risk/a99942.html failed when I tried it. I got, and still get, a 504 HTTP error code for that URL. traceroute from my system to neo.jpl.nasa.gov gets stopped with a string of timeouts at ae-3.r005.lsanca03.us.bb.gin.ntt.net -- I was able to get to the copy archived on January 20, 2013, so I used that. I see that you have reverted my change, so I'll leave you or others who edit this page more frequently than I to sort out anything which might need sorting regarding this. Wtmitchell (talk) (earlier Boracay Bill) 07:07, 24 February 2013 (UTC)