Talk:99942 Apophis

Untitled

• Archive of discussions prior to 01.01.2006
• Archive of discussions prior to 01.01.2009

Misleading Lead-in

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)

No calculations exist of earths magnetic field movement influence about 50km/per annum with North closer to Siberia for determining if NEO's keyholes alter from earlier calculations. Are we back at 2004 concern? — Preceding unsigned comment added by Plainbandit (talk • contribs) 02:50, 25 March 2019 (UTC)

I agree that this lead-in section needs to be re-written. It is obviously fairly old. Additionally to the comment above, there is a comment about the existence of the keyhole being 800m (1/2 km) in size in 2006 and then refers to a 2006 article saying that in 2008, it had reduced in size to 1 km (which is greater than 800 meters). I may take a shot at soon, but feel free to do it before. As a former Physics/Astrophysics grad student, I would suggest that due to the inertia of the asteroid as it travels through the Earth-Moon system, the Earth's magnetic field will not be noticed by the asteroid. Gravity will be the only force of significance in this encounter.Autkm (talk) 01:31, 4 January 2020 (UTC)

Russian plans

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

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

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. {{cite journal}}: 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

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 (talk • contribs) 10:43, 20 July 2009 (UTC)

Which is it?

"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

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

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

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

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?

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 (talk • contribs) 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

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

"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"?

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

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

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

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

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?

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

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 (talk • contribs) 12:29, 1 March 2012 (UTC)

New estimate – mass

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

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

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

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 (V_impact) 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)

External links modified

Hello fellow Wikipedians,

I have just added archive links to 4 external links on 99942 Apophis. Please take a moment to review my edit. You may add {{cbignore}} after the link to keep me from modifying it, if I keep adding bad data, but formatting bugs should be reported instead. Alternatively, you can add {{nobots|deny=InternetArchiveBot}} to keep me off the page altogether, but should be used as a last resort. I made the following changes:

• Attempted to fix sourcing for http://neo.jpl.nasa.gov/risk/2004mn4.html
• Attempted to fix sourcing for http://neo.jpl.nasa.gov/risk/a99942.html
• Attempted to fix sourcing for http://neo.jpl.nasa.gov/risk/a99942.html
• Attempted to fix sourcing for http://neo.jpl.nasa.gov/risk/a99942.html

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

Y An editor has reviewed this edit and fixed any errors that were found.

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—^{cyberbot II}_{Talk to my owner:Online} 12:42, 29 March 2016 (UTC)

External links modified

Hello fellow Wikipedians,

I have just modified 3 external links on 99942 Apophis. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20130511010048/http://neo.jpl.nasa.gov/risk/a99942.html to http://neo.jpl.nasa.gov/risk/a99942.html
• Added archive https://web.archive.org/web/20141231154154/http://neo.jpl.nasa.gov/risk/ to http://neo.jpl.nasa.gov/risk/
• Added archive https://web.archive.org/web/20090929071053/http://nai.arc.nasa.gov:80/impact/news_detail.cfm?ID=161 to http://nai.arc.nasa.gov/impact/news_detail.cfm?ID=161

When you have finished reviewing my changes, please set the checked parameter below to true or failed to let others know (documentation at {{Sourcecheck}}).

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 15:53, 30 September 2016 (UTC)

What Happened to Foresight?

The article says that "Foreisght" would be launched aboard a Minotaur IV between 2012 and 2014 and reach Apophis five to ten months later. This is in the past, so this either already happened or the project was canceled or delayed, but the article has no information on this and when I attempted a google search I was unable to find out anything. What became of this project?71.89.179.54 (talk) 02:57, 16 March 2017 (UTC)

The keywords in that paragraph are "proposed" and "would be". It never got further than a contest entry. Someguy1221 (talk) 03:17, 16 March 2017 (UTC)

Torino impact hazard scale: rating inconsistencies in the introduction

During the introduction the Torino Scale rating citations are unclear enough to make the rating itself unclear:

"However,[...] a possibility remained that [...] Apophis would pass [...] a small region [...] that would set up a future impact [...]. This possibility kept it at Level 1 on the Torino impact hazard scale until August 2006, when the probability that Apophis would pass through the keyhole was determined to be very small. [...] During the short time when it had been of greatest concern, Apophis set the record for highest rating on the Torino scale, reaching level 4."

My main issue was that when reading this passage I wasn't sure until the last line that the Torino scale didn't peak at 1: the sense of danger is transmitted well, but then the implication that thus the Torino rating was kept at 1 due to the danger is very confusing.

So what happened? From my understanding, it was discovered in 2004 (or earlier), and during that year an estimated impact probability was made, and it was high, and the danger was only assuaged in 2006 when the probability was drastically lowered.

Was the initial rating after the 2004 probability prediction 4? Was it 1? Did it just peak at some point during 2004-2006, but was reset to 1( or 0?) in 2006?

--NoePol (talk) 11:51, 9 May 2017 (UTC)

External links modified

Hello fellow Wikipedians,

I have just modified 5 external links on 99942 Apophis. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20080228181959/http://www.b612foundation.org/papers/wpdynamics.pdf to http://www.b612foundation.org/papers/wpdynamics.pdf
• Corrected formatting/usage for http://mpainesyd.com/idisk/Public/paine_tsunami_asteroid99.pdf
• Added archive https://web.archive.org/web/20161007201020/http://neo.jpl.nasa.gov/risk/ to http://neo.jpl.nasa.gov/risk/
• Corrected formatting/usage for http://nai.arc.nasa.gov/impact/news_detail.cfm?ID=161
• Added archive https://web.archive.org/web/20160106045208/http://neo.jpl.nasa.gov/cgi-bin/ip?1 to http://neo.jpl.nasa.gov/cgi-bin/ip?1

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 14:00, 23 June 2017 (UTC)

External links modified

Hello fellow Wikipedians,

I have just modified 2 external links on 99942 Apophis. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

• Added archive https://web.archive.org/web/20080420013749/http://afp.google.com/article/ALeqM5g6fIS_34_CxE8-vcC5GvbjD4MIOQ to http://afp.google.com/article/ALeqM5g6fIS_34_CxE8-vcC5GvbjD4MIOQ
• Added archive https://web.archive.org/web/20130317183119/http://apophisasteroid.net/ to http://apophisasteroid.net/

When you have finished reviewing my changes, you may follow the instructions on the template below to fix any issues with the URLs.

This message was posted before February 2018. After February 2018, "External links modified" talk page sections are no longer generated or monitored by InternetArchiveBot. No special action is required regarding these talk page notices, other than regular verification using the archive tool instructions below. Editors have permission to delete these "External links modified" talk page sections if they want to de-clutter talk pages, but see the RfC before doing mass systematic removals. This message is updated dynamically through the template {{source check}} (last update: 5 June 2024).

• If you have discovered URLs which were erroneously considered dead by the bot, you can report them with this tool.
• If you found an error with any archives or the URLs themselves, you can fix them with this tool.

Cheers.—InternetArchiveBot (Report bug) 04:52, 26 December 2017 (UTC)

Pronunciation

Yesterday I edited the article to say that the word should be accented on the first syllable, but Renerpho reverted it saying that I had not given a reference. What I said in my edit comment was that the o is short so in Latin the accent goes on the first syllable (as in Greek), and so in English it is also accented on the first syllable. What exactly needs a reference? There are several possibilities:

• In English, classical proper names are accented as in Latin.
• In Latin, the accent is on the antepenultimate syllable if the penultimate is short.
• The o in "Apophis" is short in Latin if it is short in Greek.
• The o in the Greek is an omicron, which is short.

In the meantime I am removing the incorrect pronunciation. Eric Kvaalen (talk) 07:22, 5 May 2019 (UTC)

It is questionable to label a pronunciation of newly set names as "incorrect". The name could be pronounced as in the television series it comes from (and I do not know how they choose to do it without watching an episode). It could also be pronounced in Latin, as one often does in English, and you give a correct, but probably irrelevant, summary of how that is determined. Or it could be pronounced as in the original Greek. I don't care which. Mlewan (talk) 07:42, 6 May 2019 (UTC)

Whether the word is pronounced with a short o in classical Latin is irrelevant. This article is about the asteroid. I have never heard it being pronounced with a short o by any astronomer (or anyone on the tv show, for that matter). It is usually pronounced with a long o in this context, and thus, the stress is on the second syllable. Note that this is mentioned as an alternative pronunciation on Wiktionary. Renerpho (talk) 12:26, 6 May 2019 (UTC)

@Renerpho: The asteroid is named after a mythological creature whose name is accented on the first syllable, because that's how it's pronounced in Latin and English follows Latin (when all the syllables are present). I suggest we put a sentence such as "Although the name of the creature Apophis is accented on the first syllable, many astronomers accent the second syllable." Eric Kvaalen (talk) 18:31, 8 May 2019 (UTC)

@Eric Kvaalen: We could add a paragraph that discusses the pronunciation, yes, as does Charon. Please note though that, unlike for Charon, there isn't really a debate about the pronunciation of the asteroid; it is pronounced with a long o pretty much unanimously. So it is not like those astronomers pronounced it wrong; it's just not the same word. We could write something like this: "The mythological creature Apophis is pronounced with the accent on the first syllage (/ˈæpəfɪs/). In contrast, the asteroid's name is accented on the second syllable." And we should reinstate the pronunciation /əˈpɒfɪs/ to the first sentence. Renerpho (talk) 19:20, 8 May 2019 (UTC)

All right, I have put in that sentence (with one word added). I couldn't bring myself though to say in the first sentence that it's definitely pronounced /əˈpɒfɪs/! Eric Kvaalen (talk) 10:49, 9 May 2019 (UTC)

I can help out there. Renerpho (talk) 18:43, 9 May 2019 (UTC)

Hi all (Eric Kvaalen, Mlewan, Renerpho), The asteroid was discovered 20 years ago, it was named 19 years ago, this discussion is 5 years old, and still, there is still not any reference given anywhere (neither in the article nor even in this discussion) to support the statement about the pronounciation. Either there are supporting sources to justify this statement, or it should have been purely removed long ago. "I have never heard..." is basically uncheckable. If there are no articles discussing specifically the pronunciation (and as a fact, only the spelling is officially approved by the IAU, not the prononciation), the bare minimum would be to provide a recording (e.g. a conference video) where the prononunciation can be heard (it wouldn't demonstrate that it is the majority pronunication, but it would show that at least someone uses this pronunication). (By the way, unfortunately but sadly unsurprisingly, Wiktionary is of no help on this point since not any of the sources in the article tells anything about pronounciation nor about the asteroid...) SenseiAC (talk) 01:35, 6 March 2024 (UTC)

My opinion hasn't changed. I still do not think it matters. If there is no information, there is no reason to try to say anything. (As the Greek said: Οὐκ οἶδ’· ἐφ’ οἷς γὰρ μὴ φρονῶ σιγᾶν φιλῶ. Or the Romans: Tu ne quaesieris, scire nefas.) Mlewan (talk) 08:37, 6 March 2024 (UTC)

@SenseiAC: My opinion hasn't changed either -- I still think it should be accented on the first syllable! I think it's good to tell people how it should be pronounced. In my opinion, there's enough justification for saying that it should be accented on the first syllable (as I wrote above, and we could try to find references for those four things I said). One could add that it's often pronounced with the accent on the second syllable. I don't really care whether that has a reference or not. I take Renerpho's word for that. Eric Kvaalen (talk) 09:39, 6 March 2024 (UTC)

@SenseiAC: e.g. a conference video -- Here is how David Tholen (the discoverer) pronounces it: DPS 52 Monday Press Conference, 26 October 2020 (YouTube video, with timestamp). For reference, this is the pronunciation used in the TV show, with the stress on the 2nd syllable (example), and every astronomer I have ever heard follows that example. Here is the first published interview they gave about the origin of the name, from August 2005, in which Tholen talks about the TV show, and how he thought the name would be fitting: Asteroid Apophis set for a makeover Renerpho (talk) 20:55, 6 March 2024 (UTC)

I wouldn't be surprised if Tholen was unaware that there was a different way to pronounce it. It doesn't matter though. At the risk of repeating myself, the "classical" pronunciation of the name of the mythological creature is of no relevance to the topic of this article. When Eric Kvaalen claims that people should be educated about how to pronounce it (that is, to put the stress on the first syllable), I believe they are misled by their affection for the classical sources, rather than the asteroid. I have no problem with having a clarifying statement in the article that tells people about how the name of the mythological creature is pronounced, but not more. Renerpho (talk) 21:03, 6 March 2024 (UTC)

@Eric Kvaalen, Mlewan, and SenseiAC: I just went ahead and added the link to the DPS 52 conference as an example of the asteroid's pronunciation. I also marked the preceding sentence, about the pronunciation of the name of the mythological creature, as needing a citation.[1] It's not controversial, but it needs a reference nonetheless. Strangely, I cannot find a good source that clearly establishes it, without the WP:OR step of implying the rules of Latin or Greek pronunciation. The Apep article refers to dictionary.com for the pronunciation, but that source conflates the two meanings, and is of no use. Maybe one of you knows some academic book about Egyptian mythology that provides proper pronunciations of names, and which can be cited in both articles (here, and in Apep)? Renerpho (talk) 20:39, 19 April 2024 (UTC)

Sorry, I don't have a reference for you. But I think it's ridiculous to call it "original research" to simply apply the well-known rules of Classical pronunciation! That's not what the "original research" rule is supposed to be against. It's not even research, let alone original. Eric Kvaalen (talk) 08:03, 20 April 2024 (UTC)

Future collision

I would like to see in the article something about the eventual fate. Approximately every 1.1 years after 2029 Apophis will come back to approximately the same place in the solar system where it will almost have hit the earth in 2029. The earth comes back approximately to that point every sidereal year. So every so often there will be a fairly close encounter. Eventually there will be one that again significantly alters the orbit of Apophis, but then after that what I have just said will still be true, that is, Apophis and the earth will still come back to the same place every so often. It seems to me that these near misses will continue for a long time, until Apophis either gets perturbed so much that it has a fairly close encounter with another planet (changing its orbit so that it no longer has close encounters with Earth) or Apophis hits something, most probably the earth! What is known about the future of Apophis? When is the next time after 2029 that it will come close enough to Earth to have its orbit changed significantly? What is the probability that it will eventually hit the earth? Eric Kvaalen (talk) 10:49, 9 May 2019 (UTC)

If Earth was the only planet in the Solar System that influences Apophis then this would indeed be true. Apophis would continue to encounter Earth until it hits or is ejected. However, as Apophis undergoes close approaches to Earth, at the same time its orbit will continue to precess due to the influence of the other planets (mainly Jupiter). As a result, its MOID is likely to increase beyond the 0.05 AU threshold on a time scale of a century millennium or two. After that, there will be no close encounters for a long time. - That is of course assuming that it doesn't hit Earth along the way, or come close enough to have its orbit altered in such a way that it crosses one of the neighbouring planets (Venus, Mars). If that happens, this provides an alternative pathway to getting out of the scenario you describe (via a close encounter to another planet). This is true for all potentially hazardous asteroids. Applying that argument backwards, you get to the reason why the concept of a PHA makes sense: An asteroid with a MOID of 0.05 AU at the present epoch can easily evolve into one with a MOID of 0 due to orbital precession. The best example is 1950 DA, which at present has a MOID of 0.041 AU, but has a chance to hit the Earth in the 29th century. Renerpho (talk) 18:55, 9 May 2019 (UTC)

To answer your other questions: "When is the next time after 2029 that it will come close enough to Earth to have its orbit changed significantly?" - We don't know, because the 2029 encounter will make such a prediction impossible. But we know that it will have to be within the next 200 years or very far in the future, because after that point, its MOID will have increased to where such an encounter becomes impossible for thousands of years. We can look at that question from a different direction: Statistically, an encounter like that of 2029 happens once every 800 years, involving any of the ~10,000 NEAs the size of Apophis. So the time between consecutive approaches from the same asteroid will be close to 800x10,000 = 8 million years. That calculation is rough, but it probably gives the right order of magnitude for the time scale you are looking for. -- And "What is the probability that it will eventually hit the earth?" - Again, we don't know, but it depends on what you mean by "eventually". Over the course of the next 100 years, that probability is about 1 in 110,000. That's the point to which Sentry does its calculations. After that, the potential impacts become rarer (because the MOID doesn't tend to stay at 0 for long), so the risk for the next few thousand years is probably close to that number. Over the course of its dynamical lifetime (which is a few tens of millions of years), the chance of impact may be a few percent.Renerpho (talk) 21:05, 10 May 2019 (UTC)

@Renerpho: All right, thanks for the explanation. Can you add some of that to our article? Eric Kvaalen (talk) 15:27, 12 May 2019 (UTC)

@Eric Kvaalen: I'd have to check if there's anything regarding its long-term future in the literature (I have no reliable source at hand)... If I find the time, I'll give it a try. Renerpho (talk) 18:41, 12 May 2019 (UTC)

@Renerpho: Well, what you said above is just general knowledge. You don't need a reference for that. Another question for you: What does this reference mean when it says that the distance on April 12, 2068 will be 0.02 Earth radii? Why did an editor (Kheider) just the other day say that on that date /ˈæpəfɪs/ may be further away than the sun? Eric Kvaalen (talk) 06:40, 13 May 2019 (UTC)

The 0.02 r(adius)_Earth is just the minimum possible distance over the line of variation (LOV)s. That is more of a 5-sigma solution and has nothing to do with the nominal solution. If the asteroid was expected to be within say 1 million km of Earth on 12 April 2068, and the LOV was only 1 million km long, the odds of impact would be more like 1:1000, not 1:150000. Apophis is expected to be ~0.5AU from Earth in 2066, and be nowhere near Earth in 2068. But non-linear methods can not yet rule-out an impact in 2068. -- Kheider (talk) 07:33, 13 May 2019 (UTC)

@Eric Kvaalen: To add to what Kheider (correctly) explained: The 0.02 Earth radii is the Earth MOID of Apophis's line of variation in 2068. As you may know, it is a necessary (but not sufficient) condition for an impact to be possible that the Earth MOID be less than 1 Earth radius (if the orbits don't intersect, a collision cannot happen). The MOID is less than 1 Earth radius here (0.02<1). The sufficient condition (the LOV actually crosses the position of Earth) is also satisfied, as Sigma LOV is within (-5,+5), and so there is a chance of impact in 2068. That chance though is very small! The LOV is stretched very long at that time, 1.31e+5 Earth radii (834 million km). That is close to the circumference of Apophis's orbit... What that means is that Apophis could be literally anywhere along its orbit at that time, and the chance that it happens to be exactly where the Earth is is miniscule. Compare that with a case where an impact is actually realistic (albeit still not likely), 2009 FD in 2185: The Stretch LOV is just 2.23e+2 Earth radii (1.4 million km), and so there is a chance that it would intersect Earth (actual odds are 1 in 710 for that impact). If you see a Sentry prediction, and you want to know whether it is a meaningful prediction (not merely a theoretical one), check the Stretch LOV. If it is small compared to the Earth's orbit (i.e., less than 1e+4 Earth radii) then it is interesting. Otherwise it is just a fancy way of saying "this asteroid could be anywhere". -- Regarding the addition to the article: The basic principles are general knowledge; the numbers, including the time scales I mentioned, are not. There is little value (imho) adding those general principles to the Apophis article without being able to give numbers. Maybe some of this could be added to the potentially hazardous asteroid article. Renerpho (talk) 09:40, 13 May 2019 (UTC)

@Renerpho and Kheider: Thanks for the explanations. But there are still a few things I don't understand.

1. First of all, what is a line of variations? The SENTRY site uses the term but doesn't explain what it is.

The LOV is a tool used to describe the complicated motion of Solar System objects, by making a linear approximation that is easier to understand than the full equations. Of course the simulations are still done with the full set of equations; the approximation is only made to make the description easier. Why is the LOV useful? Well, as you probably know, the position of an asteroid is always known imprecisely (see astrometry). Usually, as an object is observed in the sky, we get two of its three spacial coordinates very precisely (we can measure RA and Dec, but have no idea about the third, its distance). This means its true position can be anywhere along a line pointing at us from the direction of the object (this isn't the LOV yet, but bear with me). With more data coming in, we can rule out most of that line, but we can't get it to zero. When you combine this with the fact that our measurements of the two observable coordinates also come with imprecision, you get that the best case we can hope for is to know the position of the asteroid to within some sphere of a given radius (usually, that radius is a few km's to a few thousand km's for most asteroids). If you then stop to observe the object, or simulate its posible future orbit, you need to take that uncertainty into account: What happens to a spherical cloud of particles under gravity? It turns out that it gets stretched, and lucky as we are, the maths of orbital mechanics are such that it gets stretched in one axis much more than in the others (the orientation of that special axis depends on the circumstances!). So the uncertainty region first looks like an ellipsoid, then like a very long ellipsoid, and eventually it becomes almost a line. That is the Line of Variation. If you want to see that in action, I suggest you play with NeoDyS. See also [2]. Renerpho (talk) 20:15, 13 May 2019 (UTC)

2. Where do the values 1:1000 and 1:150000 come from?

1:150000 is the probability of impact on 2068-04-12. Sentry gives it as 6.7e-6. If you click on that number, a pop-up window will open that tells you that 6.7e-6 is equal to 1:150000. The 1:1000 is hypothetical. I made that precise by giving an example ((2009) FD) that actually gets close to the number that Kheider mentioned. If Apophis's LOV was as short as that of (2009) FD then its impact probability would be similar to the 1:710 risk I quoted for that object. In general, the impact probability will be of roughly the same order of magnitude as 1/(Stretch LOV), i.e. if the LOV stretches 1,000 Earth radii (6.4 million km) then the impact risk may be something like 1:1000.Renerpho (talk) 20:15, 13 May 2019 (UTC)

3. And isn't it contradictory to say that Apophis is expected to be nowhere near Earth in 2068 but also that we can't rule out an impact? Do you mean that the "expected value" of the distance is more than 1.5 AU but that the distance could be zero?

Exactly that. In other words, it could be anywhere along its orbit, and will most likely be very far away, but we don't know enough to rule out that it is where the Earth is.Renerpho (talk) 20:15, 13 May 2019 (UTC)

4. It seems to me that there could be an impact even if the MOID is greater than one Earth radius, because if the thing gets quite close to the earth, the earth's gravitational force will bend its path and it could hit the earth even if the unperturbed path would not have done so.

A good observation! This is correct, but luckily it is already taken into account in the Sentry table (think of their number as a "gravitationally bent MOID"). There is an alternative method for calculating impacts, the B-plane, and there you need to consider what you mentioned.Renerpho (talk) 20:15, 13 May 2019 (UTC)

5. And finally, how can they know so precisely what the MOID will be, but have no idea where on the orbit the thing will be?? Eric Kvaalen (talk) 12:34, 13 May 2019 (UTC)

The MOID of the asteroid itself comes with uncertainty just as all the other orbital parameters. But because that uncertainty can be modelled so well using the Line-of-Variation method, one can calculate how close that LOV can come to Earth, and so get a value for the smallest possible Earth MOID of the asteroid. Of course, one needs to be careful: If our knowledge of the orbit is too imprecise, the LOV becomes a 3-dimensional being again. For that purpose, Sentry gives the width of the LOV in its table. For all but the worst cases, that width is <1e-4 Earth radii (less than 1 km), which means that the LOV can be handled as if it were a line with zero width. Calculating the distance between a line (the LOV) and a point in space (the centre of the Earth) is Linear Algebra. Renerpho (talk) 20:15, 13 May 2019 (UTC)

Removal of a WP:RS

This should stay. The headline says what it says. WP:LIKE is no excuse for WP:Censorship. 7&6=thirteen (☎) 16:49, 3 November 2020 (UTC)

Your Popular Mechanics reference incorrectly states, "Apophis is also scheduled to make a close approach to Earth muchin 2029. The chances of it colliding with Earth during this pass, however, are negligible." There is ZERO chance of Apophis impacting in 2029. Also there is no reason to think Apophis will be anywhere near Earth in 2068. That is why the odds of impact (the line of variation) is at 1/150000 and not 1/1000. -- Kheider (talk) 17:02, 3 November 2020 (UTC)

The reference's statement about any negligible (non-zero) impact risk in 2029 is nonsense. All the rest can be more reliably verified via the hawaii.edu reference. I see no use in keeping the Popular Mechanics citation. Renerpho (talk) 19:15, 3 November 2020 (UTC)

References

Pronunciation #2

The lead says this asteroid is pronounced /ˈæpəfɪs/ yet §Discovery_and_naming says The mythological creature Apophis is pronounced with the accent on the first syllable (/ˈæpəfɪs/). In contrast, the asteroid's name is generally accented on the second syllable (/əˈpɒfɪs/) as the name was pronounced in the TV series.. Which is it?  Nixinova   T   C   02:24, 12 November 2020 (UTC)

Thanks, as you can see at Talk:99942_Apophis#Pronunciation, this has been discussed before, and the change was made to /əˈpɒfɪs/ in the lead section. This was silently reverted a few months ago, introducing the contradiction between the lead and the article body below. Renerpho (talk) 03:05, 12 November 2020 (UTC)

2029 close approach

The article says "The close approach will be visible from Europe, Africa, and western Asia". Will it be visible (but dimmer) from North America before or after closest approach? Bubba73 ^{You talkin' to me?} 21:32, 6 March 2021 (UTC)

Yes. Apophis approaches Earth from the south, so locations in the southern hemisphere are favoured, but it will be observable from the continental United States prior to closest approach (Canada is difficult, South America and Australia are better than the US). Apophis will last be visible from the US east coast about 14 hours before the closest approach (at 7th magnitude, when it is about to cross the Moon's orbit), and an hour or two longer (at 6th magnitude) from the west coast. Naked eye sightings might be possible from dark sites, especially in the south-west of the United States. It will not be observable at all after the closest approach. Renerpho (talk) 00:31, 7 March 2021 (UTC)

Thanks, then a time exposure with my camera can probably get a streak. Bubba73 ^{You talkin' to me?} 02:14, 7 March 2021 (UTC)

2068-Apr-10 Aphelion

• Apophis is expected to come to aphelion 2068-Apr-10 15:41 @ 1.31AU from the Sun (JPL #204 dated 2021-Mar-05).
• Apophis is expected to come to aphelion 2068-Apr-10 11:39 @ 1.31AU from the Sun (JPL #206 dated 2021-Mar-09).
• Apophis is expected to come to aphelion 2068-Apr-10 11:20 @ 1.31AU from the Sun (JPL #207 dated 2021-Mar-15).
• Apophis should be 0.52AU from Mars, **1.87AU from Earth**, 1.4AU from Venus, and 1.1AU from Mercury on 2068-Apr-12. Closest approach to Mars should occur 2068-Jun-11 @ 0.45AU. -- Kheider (talk) 07:35, 8 March 2021 (UTC)

Removal from Sentry Risk Table (timeline)

The article currently gives conflicting information about when and how Apophis was removed from the Sentry Risk Table, marking the point when an impact in the next 100 years was ruled out. While the final paragraph of the article lead, and some of the sources, give 25/26 March 2021 as the date, and the radar data collected in early March 2021 as the main reason for the removal, the Sentry Risk Table itself disagrees: Its Removed Objects page gives 2021-02-21 08:22:28 UTC as the time when Apophis was removed (not 26 March, as claimed in the article). At that point, only optical astrometry had been collected in 2020/2021. This needs to be clarified. Renerpho (talk) 05:52, 27 November 2021 (UTC)

I have removed both references[3] to the timing of its removal from the Sentry risk list. If there was a way to resolve the issue, I think one year (more than 1 1/2 years, actually) would have been enough to resolve it. Since the available sources are inconsistent, there's no way for us to present the information accurately, so we better don't present it at all. --Renerpho (talk) 22:42, 23 June 2023 (UTC)

While we're at it: The (very useful) image [4] gives a source that does in no way support the data presented in it. Looking at its file page, things only get worse, as the page makes claims that the source can never support. The Close Approach List given as its single source does not contain any positional data that could be used to create a plot like this, let alone physical explanations, like the stated (on the file page) connection to the opposition effect. Maybe someone can look into that, too, and determine to what extent that image is WP:OR and to what it just needs better sources. Renerpho (talk) 06:27, 27 November 2021 (UTC)

Since the issue of the unsupported image remains unresolved, I have removed the image for now, so we can resolve the issues and make sure it can be added back with a proper source. I will copy that part of the discussion over to the file's page on WikiCommons. I suggest to discuss the necessary steps there, so that we can (hopefully - anyone?) use this page here to concentrate on the problems of the Sentry Risk page raised above. Renerpho (talk) 02:29, 3 May 2022 (UTC)

2029 hypothetical impact risk corridor

• Specific text to be added or removed: (Image)

  

  Hypothetical risk corridor for an impact on 13 April 2029, based on the 2020–21 planetary defense exercise

• Reason for the change: To be added after the first paragraph of the 2020–21 observations section. The image could support the section, in the context of the Planetary Defense Campaign exercise.
• Reason for the request: I am one of the authors of the Apophis Planetary Defense Campaign paper, resulting in a WP:COI. I made contributions to this Wikipedia article before, including some where I had to disclose COIs, but here I'd just be citing myself.
• References supporting change: While the similar image used in the publication is copyrighted (see the link above, page 14, figure 8 - not my work), my February 2021 image [5] has been uploaded under a suitable license, and can be used on Wikipedia.

Renerpho (talk) 09:03, 1 June 2022 (UTC)

 Done PK650 (talk) 07:56, 9 June 2022 (UTC)

AI generated meme?

I have just removed the following paragraph[6] from the Popular Culture section, which had been added yesterday by an IP user:
The phenomenon became an Internet meme proliferated by commenters on the sponge.ai livestream in May and June 2023. The stream focused on an AI program generating parodic mini-episodes of Spongebob SquarePants.
Besides the fact that I don't even understand what it's trying to say (which phenomenon?), I have no way to assess whether this is complete nonsense or a useful addition. With no references attached, I considered it better be moved here for discussion. Any insights? --Renerpho (talk) 20:22, 7 June 2023 (UTC)

Venus closer than Apophis in 2036?

Animation of 99942 Apophis around Sun - 2036 close approach

   Sun ·    Earth ·    99942 Apophis  ·   Venus

"Apophis will make two modestly close approaches to Earth in 2036, but even the planet Venus will come closer to Earth in 2036"

It may or may not, but that's not really the point. Venus isn't earth crossing whereas Apophis is. In a discussion about impact risk bringing the distance to Venus in just seems confusing. I get the point being made, that in 2036 Apophis never gets close, but perhaps there is another way to say it...

"Apophis will make two modestly close approaches to Earth in 2036, but current predictions suggest these will be no closer than 23m kilometres (60 times the distance to the moon)"

46.227.49.108 (talk) 11:37, 10 July 2023 (UTC)

The point is that Venus will come closer to Earth in 2036 than Apophis will. The orbit of Apophis is that well known. The uncertainty region for Apophis on 27 March 2036 is only ±130,000 km (3-sigma) and Apophis will be 0.309 AU (46.2 million km; 120 LD) from Earth. Venus will be 0.288 AU from Earth in May 2036. Your "no closer than 23 million km" is an obsolete 2013 source from 10 years ago. -- Kheider (talk) 12:55, 10 July 2023 (UTC)

Hi, I was looking at the lede. It just feels strange there to bring Venus into it there. (It reads fine in the 2036 detail section). To be clear I'm not questioning the facts, just that it reads a bit strangely in the lede.

I'm just thinking that the lede point is really that Apophis is not approaching that closely. We often use multiples of the earth-moon distance for approaches, so why not use that instead?

(BTW Sorry for the obsolete source, I got it from that strange encyclopaedia called Wikipedia - "List of future astronomical events" :) Does that need correcting? I'm not brave enough - yet!) 46.227.49.108 (talk) 14:05, 10 July 2023 (UTC)

I would think saying Venus will come closer to Earth than Apophis gives a better sense of distance than saying 120 Lunar distances? As a further example, Venus will be 0.2887 AU (43.19 million km; 26.84 million mi; 112.4 LD) from Earth next month on August 3. -- Kheider (talk) 14:25, 10 July 2023 (UTC)

Do you think so? I guess my thinking is that the earth-moon distance is pretty constant, it's a kinda vaguely understandable distance in our cultural consciousness (moon landings, permanently visible, quarter of a million miles, 3-days etc), and that we use it quite a lot for asteroid flyby distances.

That Venus is closer at some point in 2036 is an interesting factoid which I certainly didn't know, but I'm not sure it really gives me a scale of how near Apophis gets. That's what I'd be after in the lede.

Anyway, I'm not going to try and force what is really a matter of opinion, so unless any other thoughts emerge I'll leave well alone. 46.227.49.108 (talk) 14:52, 10 July 2023 (UTC)

If there was to be a change it should be to solar distances with something like: "at a third the distance of the Sun which is also about how close Venus gets to Earth". But that would make the lede more wordy and the lede should be short and to the point. Venus beats Apophis in 2036. -- Kheider (talk) 15:10, 10 July 2023 (UTC)

Having said I'll leave well alone.... I like the idea of using Solar distances. That is also something that is going to be more widely understood by the general reader. The challenge is how to word it naturally.

How about replacing...

"Apophis will make two modestly close approaches to Earth in 2036, but even the planet Venus will come closer to Earth in 2036"

With..

"In 2036 Apophis will cross the earths orbit twice, but even the closest of these approaches will still be 46 million km away. To put that into perspective the distance from the Earth to the Sun is 150 million kilometres."

Something along those lines anyway. That kinda makes the point that it really is going to miss by a fair margin and gives the non-expert a more easily understandable scale of the miss.

Now I really will drop out! 46.227.49.108 (talk) 09:08, 11 July 2023 (UTC)

What 143.44.185.142 (talk) 09:40, 19 October 2023 (UTC)

Is there a secondary source that says that Venus comes closer to the Earth than Apophis does in 2036? That should settle the question of whether it is belongs in the article, per WP:SYNTH. Renerpho (talk) 06:11, 11 July 2023 (UTC)

Hi, Sorry, I wasn't questioning the inclusion. Assuming it's correct (and I don't have the knowledge to question it) it is an interesting fact. It certainly would never even have occurred to me. I just think that in the lede it's more technical that most people would get and so is best in the main body. I remember trying to explain to someone a few years ago why journeys to Mars were easier every two'ish years. "Wha'd'ya mean the distance to Mars varies...."! At least the lunar and solar distances are constant (more or less) in comparison. 46.227.49.108 (talk) 09:19, 11 July 2023 (UTC)

Inclusion criteria for Popular Culture section

I have just removed the Enter Shikari song from the "Popular Culture" section (again). Danbloch had last removed it on September 29th,[7] and it was independently added back earlier today by an IP user. What is the baseline for inclusion? Of course we need reliable sources and establish notability, but maybe we can do that for the suggested additions, rather than simply remove them? Renerpho (talk) 10:12, 27 October 2023 (UTC)

"Proposed" symbol

In Discovery and naming, we mention Denis Moskowitz's proposed symbol. Our sources are his 2008 book, and his website. I have two issues with this section.

1. The use of the image seems problematic for copyright reasons. I have just nominated it for deletion (see here for details). Copyright would probably be no issue if this was just a Unicode symbol, but...
2. Unlike most of the other symbols devised by Moskowitz (see here and here for the two latest examples), I see no evidence that he ever actually proposed this one to Unicode. When we write that Denis Moskowitz, a software engineer who devised most of the dwarf planet symbols in Unicode, proposed a symbol for Apophis, aren't we implying that he proposed them to Unicode, like the dwarf planet and many other asteroid symbols he devised? Until he submits it to Unicode, the proposal was for his book, and his book only, and I think we may be giving it undue weight here. Renerpho (talk) 02:48, 25 October 2024 (UTC)

1. Copyright isn't an issue for simple graphic symbols like this, and in any case the rights have been changed.

2. You could read that into it, so perhaps it should be reworded, but AFAICT Moskowitz hasn't proposed anything to Unicode. — kwami (talk) 06:12, 28 October 2024 (UTC)