Take A Breath, Apophis Won’t Hit Earth In 2036

Artist impression of the rocky asteroid Apophis, named after an ancient Greek god who was the enemy of the Egyptian sun god Ra. Credit: ESA

99942 Apophis, a near-Earth asteroid that orbits the sun every 324 days, briefly raised a few hairs on the backs of astronomers after its discovery in 2004. Early orbital calculations gave it a 2.7 percent probability of striking Earth during a close flyby in 2029.

A later study of older photos that happened to include the asteroid helped to refine its orbit and eliminate the impact possibility that year. Unfortunately it also pointed to the chance for another potential strike in April 13, 2036.

During the 2029 flyby, it was predicted that Apophis might pass through a gravitational keyhole, a narrow region of space (just 1/2 mile wide in this instance) where Earth’s gravity alters the asteroid’s path in such a way as to set it on a future collision course. While remote, the possibility was enough to cause concern.

The orbit of near-Earth asteroid Apophis cycles within and near the orbits of the three innermost planets. Credit: NASA

Thanks to fresh data gathered when Apophis zipped 9.3 million miles from Earth this Wednesday Jan. 9, we can now breath a sigh of relief.

Astronomers used NASA’s Goldstone 230-foot radar dish as well as the Magdalena Ridge Observatory in New Mexico and Pan-STARRS observatory in Hawaii to track the asteroid and determine a very accurate orbit.

“With the new data … we have effectively ruled out the possibility of an Earth impact by Apophis in 2036,” said Don Yeomans, manager of NASA’s Near-Earth Object Program Office at JPL. “”The impact odds as they stand now are less than one in a million, which makes us comfortable saying we can effectively rule out an Earth impact in 2036. Our interest in asteroid Apophis will essentially be for its scientific interest for the foreseeable future.”

Time exposure of Apophis on Jan. 8, 2013 near the time of its most recent approach to Earth. Credit: G. Masi and F. Nocentini

If you’re a catastrophist, don’t get too down about the news.  The April 13, 2029 appearance will be the closest flyby we’re aware of of an asteroid this big. On that date, Apophis will pass only 19,400 miles from the surface of Earth and shine brightly enough (mag. 3.5) to be visible with the naked eye from suburban skies.

Viewing conditions will be ideal in Europe, Africa and the Middle East observers with dark skies during closest approach on the 13th; U.S. observers won’t be as fortunate. When Apophis is nearest and brightest, the sun will still be up in the sky. The best views for the States will happen on the evening of the 12th, when you’ll see it in binoculars as a 7th magnitude point of light low in the southern sky. When darkness falls on the 13th in the U.S., you’ll need an 8-inch or larger scope to spot it.

Speed and proximity are behind Apophis’ dramatic change in brightness over such a short span of time. It tears by Earth at such a high rate of speed that it brightens and fades in hours instead of days or weeks.

Herschel’s 3-color view of Apophis during the asteroid’s approach on Jan. 5-6, 2013. During the latest pass, Herschel collected important information about the physical properties of the asteroid, which will help astronomers make refined predictions for the future trajectory of the asteroid. Credit: ESA/Herschel/PACS/MACH-11/MPE/B.Altieri (ESAC) and C. Kiss (Konkoly Observatory)

Apophis was originally thought to be 885 feet across, but that number was refined this week when the European Space Agency’s orbiting Herschel Space Observatory made  a series of observations in infrared light during the asteroid’s approach. When those observations were combined with visual light data, scientists were able to come up with a more accurate estimate of it size. It grew! Apophis’ measures 1,066 feet +/- 50 feet across.

It’s also darker than previously thought which affects how much sunlight it absorbs. That in turn can lead to changes in Apophis’ orbit over time. Astronomers won’t be taking their eye off this monster rock anytime soon. You can read more about the findings HERE.

15 Responses

  1. H.Bob

    Great blog Astro Bob. Just started following. Great info and great images in a goldilocks zone of quantity.

    Question on the asteroid. If it did have it’s orbit changed and was heading for earth (in 2029) how long would it take to impact ?

    1. astrobob

      Thanks H.Bob. I don’t know that I can answer your question. If you’re referring to the effects of sunlight (named the Yarkovsky Effect), its orbit could be changed in ways that would make it pass even farther from Earth. Or it could go the other way. Assuming it was headed directly for the Earth it would hit the planet during one of its regular flybys. Based on how its orbit evolved, astronomers would make a prediction for a particular year and date when Apophis’ orbit would intersect Earth’s at the same time the asteroid was at that point. For more on the Yarkovsky Effect, click here: http://osiris-rex.lpl.arizona.edu/?q=node/68

      1. H.Bob

        Interesting. Was not aware of Yarkovsky Effect though it does seem that effect would be much less significant than the potential gravitational keyholes or asteroid to asteroid impacts.

  2. Lynn

    Hi Bob
    As the asteroid orbits the sun every 324 days can that make any difference to its size etc, in the way that the sun does to comets, and I’m so glad it didn’t have our name on it for the foreseeable future more for our children’s sake.

    1. astrobob

      This is a rocky asteroid (no ices), so it doesn’t grow a tail or shed material. It can be affected by sunlight by the way I described to H.Bob (below). Check out the Yarkovsky Effect link there.

  3. Lynn

    Interesting article Bob on the Yarkovsky effect, I didn’t know that could happen, but when they are working out the trajectory and if any impacts do they take that into consideration. Thanks

  4. Dean

    Apophis can be deflected from an impact with any one of the billions of smaller space rocks, thus sending it into Earth. Aliens in the Milky Way have been known to intentionally alter orbits with precision, sending large meteors such as Apophis into orbits calculated to land on Duluth, perhaps even today!

  5. Giorgio Rizzarelli

    OK.. not 2029, not 2036.. let me calculate.. if it comes 2043, we’ll have the technology to carry it away in a bag like at Macdonald. The bag will indeed have Macdonald logo because of space privatization, or probably Google logo like the future Moon rover. Which means aliens teamed up with Google to take Earth!

  6. Wayne Hawk

    Aloha Astro Bob and Everyone!

    Nothing like a headline to one of your articles with the words, “hit” and “earth” in it to generate a bit of stress amongst the “catastrophist” (love that word!) types, eh?

    I realize you get questions from folks that are practically impossible to answer due to so many variables and am continually amazed that you always manage to take the time to answer them. I was tempted to ask you a question similar to those like, “Now that Apophis is estimated to be at least 1,000 feet across and the meteor/asteroid that made the massive crater in Arizona is estimated to have been only 150 feet across, would that make Apophis large enough to wreak enough havoc on earth to upset the delicate balance of global temperatures?”, but decided not to hold you to answering it since it looks like we only have a “one in a million” chance of that happening in this century. I mean it, don’t waste your time trying to figure anything out as I simply wanted to show folks that you have better things to do with your time than to answer questions to an event where the possibility of it happening are almost non-existent.

    I know, some folks seem to almost “enjoy” speculating the “what would happen” scenario and I’m so happy I now have a word to describe them…”catastrophists”…PERFECT! Did you know this wasn’t a word? If it were it would be listed in the dictionary as a noun (obviously). As usual with most sciences, new words have to be created to fill the void created by current discoveries and facts. Did YOU create this word? Just curious.

    1. astrobob

      Hi Wayne,
      I guess I just created it. Sure sounds like a word. If an asteroid the size of Apophis hit, it would not be large enough to wreak global havoc, but would cause massive local devastation. And if it fell in the ocean, a powerful tsunami would ensue. If it came in at 20 km/sec. at a 45 degree angle and struck sedimentary rock, it would create an approx. 1.2 mile wide crater. You can go to the Asteroid impact calculator page in the links column of the Astro Bob homepage to play around with the possibilities yourself.

  7. Mike

    I haven’t been able to find any post 2036 flyby predictions. Will the close shaves continue? Will Apophis’ passes become progressively farther away? Or is there no way to predict from current data? I’m a Teacher an my students are asking these question.

    1. astrobob

      No doubt there will be other close passes in the future – it is a near-Earth asteroid and these things happen – but “nothing in the foreseeable future” according to NASA. How long that is I can’t say and I’ve seen no numbers. Apophis’ orbit will undergo changes over the long haul from gravitational interactions with the planets as well as the Yarkovsky Effect (absorption and re-radiating of sunlight) which is why astronomers will continue to keep an eye on it.

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