Today’s Factismal: The asteroid 2012 DA14 will come within 17,000 miles of Earth today.
If it is night, go outside and look up. See anything unusual? You probably won’t, but there is something very interesting happening right now. The Earth is having its closest encounter with a large asteroid in more than a century.
At 7:24 PM in London (1:24 PM in Chicago, 10:24 AM in Tokyo, 3:25 AM in Cape Town), the asteroid 2012 DA14 will make its closest approach to Earth. There is no chance that this asteroid will hit us this time around, but it will pass so close to Earth that it will actually pass below some satellites. It will curve in toward Earth, falling into our gravity well and then slingshot off into deep space once again.
Though it is headed out into space, the asteroid will return. It practically has to; its orbit lies between Venus and Earth, and so it passes near us every few years. In 2019, it will actually approach Earth twice, once within 44 million miles and once within 17 million miles. And we’ll have encounters with it again in 2020, twice more in 2026, and then again in 2033.
And 2012DA14 isn’t alone out there. Astronomers have found some 9,668 asteroids in orbits like 2012DA14’s. 1373 of them are in orbits that might hit Earth someday, and 861 are larger than a half mile across. 2012DA14 is much smaller than the big guys; it is only about the size of a ten story building. Based on the light that it reflects, it appears to be made out of rock similar to basalt or granite.
Based on its orbital characteristics and composition, if 2012DA14 were to hit Earth, it wouldn’t actually hit Earth. Instead, it would come barreling into the atmosphere. As it compressed and heated the air, the rock would be subject to enormous forces; bit and pieces would break apart, creating a massive fireball. Once it had dug deeply enough into the atmosphere, the pressures would become too great and the asteroid would shatter into thousands of pieces, creating an air blast as strong as a hydrogen bomb and raining rocks over a large area.
If that sounds scary, just remember that it has happened before and will happen again. Tunguska in 1908 was probably an event like this (nobody is sure because nobody was there when it happened). And Chixulub back at the end of the dinosaurs was probably like this only with a much larger rock (about 6.2 miles across). On average, the Earth is hit by an asteroid or comet this large every 40 years.
If you’d like to help discover more asteroids like this, then why not join the OSIRIS-Rex crew as they Target Asteroids!
Update: A second meteorite has just exploded over a remote village in Russia. As many as 1,000 people were hurt by falling bits of meteorite rock (none of them are expected to gain superpowers). The Russian meteorite was about the size of a dishwasher before it exploded. It weighed ten tons and was made of loose rock. More details as I get them.
You can see the shockwave of the meteorite as it enters the Earth’s atmosphere in this seismogram:
Update 2: There has been yet another meteor, this time over California near San Francisco. This meteor is unrelated to either of the other two. We just seem to be going through a very crowded part of the skies right now.