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.
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.
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.