Asteroid 2012 DA14 is almost certainly not going to hit the Earth next February

[pokerfan]

Asteroids have us in our sight. The dinosaurs didn't have a space program, so they're not here to talk about this problem. We are, and we have the power to do something about it. I don't want to be the embarrassment of the galaxy to have had the power to deflect an asteroid, and then not and end up going extinct. (Neil DeGrasse Tyson on NPR)

Phil Plait, Bad Astronomy, March 4th, 2012:

A small near-Earth asteroid was discovered in late February by astronomers at the Observatorio Astronómico de La Sagra in Spain, less than two weeks ago. Designated 2012 DA14, it’s estimated to be about 45 meters (150 feet) in diameter, and has an orbit that is similar to Earth’s.



Next year, on February 15, 2013, DA14 will actually get pretty close to Earth. It will pass us at a distance of about 27,000 km (17,000 miles) — well beneath many of our own orbiting satellites! To the best of my knowledge, this is the closest pass of a decent-sized asteroid ever seen before the actual pass itself.

However, let’s again be very clear: it will miss. In astronomical terms, 27,000 km is pretty close, but in real human terms it’s a clean miss.

http://blogs.discovermagazine.com/badastronomy/2012/03/04/no-asteroid-2012-da14-will-not-hit-us-next-year/

[Kber]

1. That's a relief!

[Systematic Chaos]

2. I was thinking more along the lines of, "that's ALMOST a relief."

[pennylane100]

3. I believe the speed of light is 186,000 miles per second.

Not sure if the asteroids travel at that speed but if they do, it will come really, really close.

[muriel_volestrangler]

8. No, they don't travel at anything like the speed of light

They are in orbit round the Sun, and travel at similar speeds to the Earth and other planets.

The NASA page that Phil Plait links to actually gives their estimate of the relative speed of Earth and the asteroid at the Feb 2013 near approach - about 8.1 km/s. That is marginally more than the 7.8 km/s of satellites in low earth orbit.

In fact, that's not that much more than the escape velocity at that distance (27,000 km) - which is 5.43 km/s according to this. So it would seem to me that Earth will have quite a significant effect on the asteroid's orbit when it comes that close.

[Owlet]

3. Which begs the question

just how close to Earth would an asteroid have to be to be drawn in by it's gravitational pull? And just how accurate is this 17,000 mile estimate? This is an event that is 11 months out. Sheesh, they can't even accurately predict the weather here much more than 72 hours in advance. I'm probably displaying my total ignorance of astronomy or astrophysics or whatever, but I'm anything but relieved at this latest information.

[pennylane100]

5. Well this posting has certainly brought new information to me about astronomy.

First, I have learned that it is different from astrology, lol. I also just read that the distance of the earth's gravitational pull is .determined by its size and its distance from the earth However, I am sure I will forget this new information quicker than the time it would take for it to hit the earth.

[pokerfan]

6. I don't believe it's necessarily as simple as simple proximity

as the object's velocity, which determines its momentum and energy, is also a factor. Gravity extends to infinity so it's not like the Earth suddenly reaches out and grabs an object that just because it's close. A very fast moving object could pass close by and hardly be influenced by the increased gravitational force where as a slower object could certainly be affected but it's more likely that it would manifest itself in the form of a change to its orbit and not getting sucked in.

That said, there is a phenomenon called a gravitational keyhole: A small region of space that could alter the course of a passing asteroid due to a planet's gravity in a way that could cause such an asteroid to collide with that planet on its next orbital pass. The word "keyhole" contrasts the vastness of space with the relatively tiny region through which a body might pass, and is not a reference to its shape.
http://en.wikipedia.org/wiki/Gravitational_keyhole

[Posteritatis]

7. Ballistics and atmospheric weather are completely different creatures

These days they can call the location of an asteroid in interplanetary space to within a few miles decades in advance. There's just not enough acting on them to make that anything other than incredibly predictable.

That said, every planet - actually, every object out there - has a "gravitational keyhole." The size, location, etc., of the keyhole depends on a lot of things, the main one being the mass of both objects (or just the Earth's in this case, as any meteor is irrelevant by comparison). If something hits the keyhole, and the keyhole can be very, very small, it will be deflected enough to hit the planet either now or in a subsequent pass.

Most of the uncertainty in asteroid prediction is in weather they're going to bulllseye that very specific location. There's a lot of precision involved there; Apophis' keyhole is less than a kilometer in diameter, for instance, which translates to only a few hundred feet wider than the asteroid itself. If something misses the keyhole, 27,000km might as well be 27,000,000km.

And asteroids have gotten very close indeed at times - they can actually bounce off the atmosphere without impacting if they come in at a shallow enough angle (e.g., missing the planet by hundreds of kilometers instead of tens of thousands).

[krispos42]

13. It depends on angles and velocity.

If the angle and velocity isn't right, it will whip past Earth. Earth will definitely affect its orbit, maybe even making a fairly radical change to the asteroid's path. But a collision is not mandatory.

And the trajectories of astronomical bodies are much more predicable than weather. Fewer interdependent variables!


The space probe Voyager 2 was launched in 1977 on a complex course to take it past Jupiter, Saturn, Uranus, and Neptune.

Voyager 2 whipped past Jupiter in 1979, changing course and picking up speed for Saturn. It came within 350,000 miles of Jupiter.

In 1981, it sailed past Saturn, bending course for Uranus.

In 1986, it arched past Uranus, bound for Neptune. It came within 51,000 miles of the planet.

In 1989, it flew past Neptune and is heading out of the Solar System. It brushed past a mere 3,000 miles above the planet's atmosphere.

Twelve years and a few billion miles of flight with very little control over trajectory... and they still managed to come within 3,000 miles of a planet.

[damyank913]

9. Damn, guess I'm gonna have to continue paying my mortgage...

...please don't think less of me.

[Thor_MN]

10. February 2013, who cares?

Everyone knows that the world is ending December 21, 2012, so...

[Ter]

11. 150 feet isn't much to worry about anyway

Maybe if it hits a large city, but not world threatening.

[Posteritatis]

12. Something that could wreck a city warrants a little concern. (nt)

[NYC_SKP]

14. So they Mayans were off by a few weeks?