Asteroid Will Safely Pass Earth in 2040

Bad Astronomy
The entire universe in blog form
Dec. 22 2012 8:00 AM

Phew! One Less Asteroid Impact to Worry About

Asteroid 2001 AG5 as seen in October 2012 by the Gemini telescope.
Asteroid 2001 AG5 as seen in October 2012 by the Gemini telescope. A concern for a short time, we now know it will miss the Earth in 2040.

Image credit: Gemini Observatory

Yay! Asteroid 2011 AG5 will not hit us in 2040! Up until now, I couldn’t say that with perfect certainty.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

Here’s the scoop: Last year, a 140-meter rock was discovered on an orbit that takes it very near the Earth. Projecting the orbit forward in time showed that it had a small but non-zero chance of impacting the Earth in the year 2040. That would be bad: It would explode upon impact with a yield of more than 100 megatons, far larger than even the biggest nuclear weapon ever detonated on Earth. While that wouldn’t cause a worldwide extinction event—this is no dinosaur-killer—an explosion equal to blowing up 100 million tons of TNT is something to be avoided.

Advertisement

The odds of impact were only about 1 in 500, but that’s still too high to rest easy. The problem is that initially, the asteroid’s orbit was difficult to determine well enough to predict where it would be more than a few years in the future. The analogy I like is pretending you’re an outfielder in a baseball game, and as soon as the batter hits the ball, you have to close your eyes. How do you know where the ball will be when it comes down? If you can only get a second to look at it after it’s hit, you only have a vague idea where it will land. But the longer you can track it, the more accurately you can see where it’s headed. Track it long enough and you can catch it.

It’s the same with asteroids. Earlier in 2012 only a few observations of AG5 could be made before it got too close to the Sun to see. Those allowed the crude estimate of where it would be in 2040, and that big fuzzy volume of space included the Earth.

Old and new orbital calculations for 2011 AG5.
Old (top) and new (bottom) orbital calculations for 2011 AG5. At first there was a small chance of Earth impact, but the new observations have eliminated that possibility.

Image credit: NASA/JPL/Paul Chodas

However, new observations taken with the monster Gemini telescope in Hawaii allowed a far better orbit to be calculated. The path of the asteroid in 2040 was found, and now clearly does not include the Earth. It will be a clean miss, by about 900,000 kilometers (550,000 miles). This is more than twice the distance to the Moon, if that helps.

The diagram above shows this: The upper picture shows the uncertainty in the region of space the asteroid would pass in 2040, and Earth is in that region. The lower picture shows the new calculations, with the asteroid missing us entirely.

I reported on this asteroid back in March 2012. At the time, with the impact risk of 0.2 percent, some people were concerned about AG5. One of those was Apollo 9 astronaut Rusty Schweickart, who is now with the B612 Foundation, a group dedicated to understanding and preventing asteroid impacts. He urged NASA to work on a plan to do something about the asteroid, should further observations make the odds for an impact higher.

Part of the problem at the time was that the asteroid was too close to the Sun to observe, and while there was a short window to observe in October 2012, it wouldn’t be until September 2013 that AG5 would be clear enough from the Sun to easily observe it. Schweickart didn’t want to lose a whole year should the asteroid prove dangerous.

Eventually NASA did perform an initial investigation into this, but now, happily, it won’t be needed. The October window worked out, the orbit refined, and now we know it’ll miss.

But this exercise was hardly a waste of time. The lessons learned were important. There are more asteroids out there, and given enough time the odds climb to certainty that we will be hit if we do nothing. The good news is we are looking for them, and hopefully, should we find one with our name on it, we’ll have enough time to be able to do something about it.

As for what we can do, stay tuned. I’ll have more about that shortly.

Tip o’ the Whipple shield to AsteroidWatch on Twitter.

TODAY IN SLATE

Politics

Smash and Grab

Will competitive Senate contests in Kansas and South Dakota lead to more late-breaking races in future elections?

Stop Panicking. America Is Now in Very Good Shape to Respond to the Ebola Crisis.

The 2014 Kansas City Royals Show the Value of Building a Mediocre Baseball Team

The GOP Won’t Win Any Black Votes With Its New “Willie Horton” Ad

Sleater-Kinney Was Once America’s Best Rock Band

Can it be again?

Technocracy

Forget Oculus Rift

This $25 cardboard box turns your phone into an incredibly fun virtual reality experience.

One of Putin’s Favorite Oligarchs Wants to Start an Orthodox Christian Fox News

These Companies in Japan Are More Than 1,000 Years Old

Trending News Channel
Oct. 20 2014 6:17 PM Watch Flashes of Lightning Created in a Lab  
  News & Politics
The World
Oct. 20 2014 1:50 PM Why We Shouldn’t Be Too Sure About the Supposed Deal to Return the Abducted Nigerian Schoolgirls
  Business
Moneybox
Oct. 20 2014 7:23 PM Chipotle’s Magical Burrito Empire Keeps Growing, Might Be Slowing
  Life
Dear Prudence
Oct. 20 2014 3:12 PM Terror Next Door Prudie advises a letter writer whose husband is dangerously, violently obsessed with the neighbors.
  Double X
The XX Factor
Oct. 20 2014 1:10 PM Women Are Still Losing Jobs for Getting Pregnant
  Slate Plus
Tv Club
Oct. 20 2014 7:15 AM The Slate Doctor Who Podcast: Episode 9 A spoiler-filled discussion of "Flatline."
  Arts
Brow Beat
Oct. 20 2014 9:13 PM The Smart, Talented, and Utterly Hilarious Leslie Jones Is SNL’s Newest Cast Member
  Technology
Future Tense
Oct. 20 2014 4:59 PM Canadian Town Cancels Outdoor Halloween Because Polar Bears
  Health & Science
Medical Examiner
Oct. 20 2014 11:46 AM Is Anybody Watching My Do-Gooding? The difference between being a hero and being an altruist.
  Sports
Sports Nut
Oct. 20 2014 5:09 PM Keepaway, on Three. Ready—Break! On his record-breaking touchdown pass, Peyton Manning couldn’t even leave the celebration to chance.