By Deborah Byrd | EArthSky.org
It’ll pass within the moon’s distance from Earth – closer than the orbits of geosynchronous satellites. But it won’t strike us in 2013.
A near-Earth asteroid – called 2012 DA14 by astronomers – is passing very close to Earth today (February 15, 2013). Astronomers estimate that, when it’s closest to us, it’ll be within the orbit of the moon (which averages about a quarter million miles away), and closer than some high-orbiting communications satellites. 2012 DA14 will be about 17,200 miles (27,680 kilometers) away. Reuters is reporting than a meteorite has struck in Russia, injuring 500 people. It has not been confirmed whether the meteorite is associated with asteroid 2012 DA14, but astronomers do known that asteroids sometimes are accompanied by moon, or travel in swarms.
Asteroid 2012 DA14 won’t be visible to the eye, but you can watch the February 15 asteroid flyby online, in real-time.
The main asteroid – 2012 DA14 – is not expected to strike us in 2013, NASA says. There was a remote possibility it might strike us in 2020, but that possibility has been ruled out also.
What will happen when Asteroid 2012 DA14 passes closely in 2013?
Most of us won’t see the large asteroid 2012 DA14 or be aware of its passage, in any way. 2012 DA14 is not large enough to alter the tides. It won’t cause volcanoes. It’ll just sweep closely past us – as millions of asteroids have done throughout Earth’s four-and-a-half-billion-year history – some in your own lifetime. It appears, however, that asteroid 2012 DA14 was accompanied by another object, which astronomers did not detect until it struck in Russia, injuring hundreds.
Asteroid 2012 DA14 will be within range for small telescopes and solidly mounted binoculars, used by experienced observers who have access to appropriate stars charts. Indonesia is favored for viewing, because it will be the middle of the night there when the asteroid is closest. Europe and the Middle East will also be in a location to view the asteroid, potentially. But this will be a challenging observation. Even those familiar with using binoculars and telescopes will need some experience to track the object as it moves rapidly across the sky.
What do we know about asteroid 2012 DA14?
Asteroid 2012 DA14 is a little guy, compared to some asteroids. It is thought to be about 45 meters across (nearly 150 feet across), or about the length of half an American football field. Its estimated mass is about 130,000 metric tons.
If a space object 150 feet wide were to strike our planet, it wouldn’t be Earth-destroying. But it has been estimated that it would produce the equivalent of 2.4 megatons of TNT. How does that compare with other known impact events on Earth? In 1908, in a remote part of Russia, an explosion killed reindeer and flattened trees. But no crater was ever found. Scientists now believe a small comet struck Earth. That event has been estimated at 3 to 20 megatons. So 2012 DA14 is in the same approximate realm as the Tunguska comet (which, actually, might have been an asteroid instead). It would not destroy Earth, but it could flatten a city.
Of course, about 70% of our world is covered by oceans. That means the most likely landing spot of any incoming asteroid is in the water – not on a city or other populated area.
Astronomers at the Observatorio Astronómico de La Sagra in Spain discovered 2012 DA14 in early 2012. We know 2012 DA14′s orbit is similar to that of Earth. That is one reason the asteroid eluded astronomers until recently. You can be sure that many astronomers are carefully tracking 2012 DA14 now.
The orbit of 2012 DA14 is an inclined ellipse. In other words, it’s tilted sightly with respect to Earth’s orbit around the sun, and, like Earth’s orbit, it’s not circular but elliptical – like a circle that someone sat down on. According to Bad Astronomer Phil Plait, who appears to have used a computer program to look at its orbit:
The asteroid spends most of its time well away from our planet. However, the path of the rock does bring it somewhat close to the Earth twice per orbit, or about every six months. The last time it passed us was on February 16 , when it was about 2.5 million km (1.5 million miles) away, equal to about 6 times the distance to the moon. That’s usually about the scale of these encounters — it misses us by quite a margin.
Will 2012 DA14 strike Earth in 2020?
No. In March 2012, when a collision between 2012 DA14 and Earth in 2020 was still remotely possible, I asked astronomer Donald Yeomans to clarify the risk. Yeomans is, among other things, manager of NASA’s Near-Earth Object Program Office at NASA’s Jet Propulsion Laboratory. In March 2012, he told EarthSky that a 2020 collision between Earth and asteroid 2012 DA14 was …
… approximately one chance in 83,000, with additional remote possibilities beyond 2020. However, by far the most likely scenario is that additional observations, especially in 2013, will allow a dramatic reduction in the orbit uncertainties and the complete elimination of the 2020 impact possibility.
It turned out they didn’t have to wait until 2013. By May, 2012, astronomers had ruled out even the remote possibility of a 2020 collision.
Still, 2012 DA14 and asteroids like it are sobering.
Bottom line: The near Earth asteroid 2012 DA14 will have a very close pass near Earth on February 15, 2013. It will sweep approximately 21,000 miles from us – much closer than the moon’s orbit and closer than geosynchronous satellites. Its orbit around the sun can bring it no closer to the Earth’s surface on February 15, 2013 than 3.2 Earth radii. Meanwhile, a meteorite has struck in Russia, early in the day on Friday, February 15, 2013. Although asteroids do sometimes have moons, or travel in swarms, NASA now says the meteorite is not associated with asteroid 2012 DA14.