Asteroids (1) : Earth (2) – Welcome to the Interplanetary Shooting Gallery

Rocks are being thrown at us, but we haven’t noticed

Artist impression of an asteroid impact - don't worry, this doesn't happen very often... (Getty Images)
Artist impression of an asteroid impact - don't worry, this doesn't happen very often... (Getty Images)

On October 7th, a small asteroid called 2008 TC3 exploded in the skies above Sudan. On October 9th, a metre-wide asteroid named 2008 TS26 buzzed Earth’s atmosphere by only 7000 km. Then on the 21st (Tuesday) a slightly bigger piece of rock called 2008 US missed us by 25,000 km. It sounds like it’s getting dangerous out there, especially when considering the last recorded object (2004 FU162) to come screaming past the Earth (at 6500 km) happened in 2004.

But don’t be concerned. Small asteroids are being thrown at us all the time; asteroid hunters are just getting better at spotting them…

We’re getting better at spotting asteroids, and we expect many more discoveries in the future,” said Gareth Williams, associate director of the Minor Planet Center. Indeed, discovering an asteroid the size of a small desk is an incredible achievement, but it has only been possible since the 1.5 metre telescope at the Mount Lemmon Survey in Arizona was renovated. Now, asteroid hunters can detect and track small objects with stunning accuracy.

Although there could be some improvement on the amount of time before an asteroid impacts Earth (the 2008 TC3 impact was predicted only a few hours before it hit us; 2008 TS26 and 2008 US were discovered after they passed Earth), but at least we had a warning about 2008 TC3 – the first time an asteroid impact has ever been predicted. In the case of 2008 TC3, the location of impact was accurately predicted, and if it were any bigger or predicted to hit the atmosphere above a populated area (like, say, London), at least we’d have some notice.

These advances are essential when tracking near-Earth asteroids, especially ones travelling from inside Earth’s orbit. Both 2008 TS26 and 2008 US were detected after they had passed infront of the Earth because they were travelling from a sunward direction. For the same reason why you have to drop the sun shade in your car when the evening sunlight dazzles you in the windshield, asteroid hunters have an ominous blindspot when trying to see asteroids coming at us at lower orbits.

Fortunately, on discovering the larger asteroids, we can track their orbits, so we know when they might come at us from our blind spot. But asteroid hunters will be keeping their eyes open for any object that might come too close for comfort, if only to predict where the next atmospheric impact fireworks will happen (we might be able to get some photographs next time).

Source: Short Sharp Science (New Scientist)

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