Exposing PseudoAstronomy

January 7, 2013

No, Asteroid 99942 Apophis Won’t Kill Us This Week


Unfortunately, the UK’s The Guardian has a misleading title in an article that came out today (January 7, 2013): “Apophis – a ‘potentially hazardous’ asteroid – flies by Earth on Wednesday.”

Now, technically, the headline is correct. For awhile, asteroid 99942 Apophis (or just “Apophis” for short) was potentially dangerous with as much as a 1 in 37 chance as calculated in December 2004 of striking Earth in 2029. Then, the worry was that in 2029 during a close approach, it might pass through a very narrow region in 3D space that would alter its orbit so it would come back in April 2036 and strike Earth.

Apophis’ Orbit

To be clear, from hundreds (if not thousands) of observations at this point, the chance of it striking Earth in 2029 is as close to 0 as you can get, and the chances of it striking in 2036 is about 1 in 250,000. Yes, 2029 will be a very close approach, with estimates being it passing by at only 5.6 times the radius of Earth. But that’s not a hit.

So what’s all this then about 2013?

It’s just a close approach. It’s the closest approach in awhile and it will let us refine its orbit even more.

Why do we need lots of observations over a very long time to get a better orbit? It’s like watching a hot air balloon in the sky: If you observe it for 3 seconds, you can get a very rough idea of how fast it’s going and where it’s headed. But if you watch it for 3 minutes, you’ll have a much better idea. And if you watch it for 3 hours, even better. It’s the same idea with asteroids, or really anything else.

That’s why this Wednesday, January 9, with its closest approach in awhile and for awhile, is important. The closer it is, the better we can pin-point its position and so the more accurate orbit we can derive in the future. We can also get a better estimate of its size. But, this approach is perfectly safe – Apophis’ closest approach this year will take it about 37-38 times farther than the moon.

Final Thoughts

I wasn’t even going to comment on this, but I’ve already seen people asking on various forums based on The Guardian‘s headline. So, there it is. Yes, technically Apophis is “potentially dangerous” because, based on our current orbit estimates, there’s a 0.0004% chance of it striking Earth in 2036. But no, the world is not going to end in 2 days after just “narrowly” surviving the “Mayan apocalypse.”

I’m hoping that the author of the article, Stuart Clark, didn’t select it. He’s written popular astronomy books and various other things, so he should know better unless he was trying to drum up page views. I’m guessing it was some editor.



  1. It is always good to have the light of science and facts and evidence.

    Comment by Jennifer — January 7, 2013 @ 3:43 pm | Reply

  2. So, let me get this straight: the odds have now risen that Apophis will strike earth in 2029 and regarding 2036, earth scientists simply don’t yet know because that all depends on possibly orbit-altering factors of the window in space it flies through? So, iow, earth scientists did not know everything yesterday & that they/we are still able to learn and add to our knowledge on a daily/weekly/monthly/yearly/etc basis. Go figure, and I thought what earth scientists would say today, would stand the test of all time until the Big Bang collapses upon itself trillions and trillions of years from now.

    Perhaps the USA &/or NASA would like to join the efforts of the Russians & Chinese who are heeding BIlly Meier/the Plejarens suggestions of nudging the space rock from its current orbit before we leave our fate up to the unpredictability of some orbit altering window in space. Perhaps it is because the rock, according to Meier & the Plejaren would strike in the Russians & Chinese back yard.

    See futureofmankind.co.uk/Billy_Meier/Contact_Report_150#Contact_Report_150_Part_7 and futureofmankind.co.uk/Billy_Meier/Contact_Report_475#Contact_Report_475_Part_2

    [Moderator’s note: This is getting ridiculous. I am now removing all quotes and active links to Meier material. If you want to explore the nature of copy-paste, do so on your own blog.]

    Comment by Bruce — January 8, 2013 @ 2:19 am | Reply

    • You clearly did not read the blog post. I invite you to read it again. Until you can demonstrate that you understood what I wrote, you will not be posting to these comments again. That is all.

      Comment by Stuart Robbins — January 8, 2013 @ 2:23 am | Reply

    • If the future of mankind is in the hands of a pathological lying windbag like Billy Meier,we `re screwed………

      Comment by Unsocial Darwinist (@Unkindbydesign) — January 10, 2013 @ 8:56 pm | Reply

  3. btw, Stuart … where did Apophis originate?

    Comment by Bruce — January 8, 2013 @ 12:46 pm | Reply

    • Do none of the resident scientists know from where in this universe Apophis originated?

      Comment by Bruce — January 9, 2013 @ 2:22 am | Reply

    • Apophis is an Sq-Type asteroid that likely originated from the inner asteroid belt and was knocked out due to gravitational perturbation by another asteroid, Jupiter, or Mars; or through a collision within the inner belt.

      Comment by Stuart Robbins — January 9, 2013 @ 2:42 am | Reply

  4. I wondering what your take on the Yarkovsky/YORP effects on the Apophis were? I understand that the amount of uncertainty in the majority of measurements in many asteroids and their associated Torino “numbers” may fall upon the effects that I mentioned?

    An associated reference would be also be at scholarpedia

    David Vokrouhlicky and William F. Bottke (2011) Yarkovsky and YORP effects. Scholarpedia, 7(5):10599., revision #122352

    Comment by jaksichja — January 8, 2013 @ 3:35 pm | Reply

    • Yeah, YORP is something I know little about other than it definitely being an uncertainty here. A lot also depends on how exactly it spins, I think. The effects wouldn’t be important over the short-term, but on decade (and much longer) timescales even for these objects a few hundred meters across, the effects could be important.

      Comment by Stuart Robbins — January 8, 2013 @ 3:40 pm | Reply

    • This paper just came out on arXiv yesterday: Yarkovsky-driven impact risk analysis for asteroid (99942) Apophis.

      Comment by Stuart Robbins — January 9, 2013 @ 3:27 pm | Reply

      • I read the pre-print with much interest–and it does sound like an asteroid that will garnish alot of attention in the coming months.

        Their conclusion kind of sounds like what I thought about it on my post of few days ago–and it obviously needed the rigorous analysis that the authors put upon it.

        I wonder how that type of news will play in the mainstream media–as long as it is handled properly?

        Comment by jaksichja — January 9, 2013 @ 5:23 pm

      • I was just reading a BBC article about the approach, but it didn’t really have any new info. I’m guessing it’ll be awhile before all the data are reduced and orbits recalculated before anything really comes out.

        Comment by Stuart Robbins — January 9, 2013 @ 5:26 pm

      • Just found this link from JPL that has the impact probability with current data for the next century. Or at least, “current” through December 29. http://neo.jpl.nasa.gov/risk/a99942.html

        Comment by Stuart Robbins — January 9, 2013 @ 5:34 pm

  5. I can see how certain media types can blow uncertainties out-ot-proportion. My latest post is on the subject of YORP/Yarkovsky. Thanks for reading my response.

    Comment by jaksichja — January 8, 2013 @ 4:02 pm | Reply

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