Going unseen and undetected up until Thursday, a 10-metre wide asteroid flew past the Earth very early Saturday morning.
Asteroid 2013 LR6, a hunk of space rock roughly the size of your average garbage truck, made its closest approach to Earth at 12:42 a.m. EDT Saturday morning, coming within about 105,000 kms of the planet, which is roughly one-third the distance from here to the Moon. This space rock was discovered roughly a day earlier by the Catalina Sky Survey, which regularly scans the skies for 'near-Earth objects', both to catalogue them and watch out for ones that might actually hit us.
Spotting asteroids the size of 2013 LR6 isn't easy, though.
As I (somewhat prophetically) wrote about back in February — just one day before a 50-metre wide asteroid exploded over Chelyabinsk, Russia — these asteroid flybys we hear about in the news are just a hint of what's really out there. This latest image from the Armagh Observatory shows a 3D map of the asteroids floating around in our area.
The red oval is not the orbit of the Moon, by the way, but a distance of 10 lunar orbits (3.84 million kilometres). If you click on the image, you will see that 2013 LR6 doesn't even appear on it; that's how new this asteroid is to us. Conversely, you can still see asteroid 1998 QE2 — the 2.7 km-wide rock that flew past us just over a week ago — just 'below' Earth, as it continues to pace us on its way back out beyond Mars. (If the map is hard to read, the lines are there to represent vertical distance. Each line joins the object, shown by the dot, to the plane of Earth's orbit. If the dot is at the top of the line, the object is above our orbit and if the dot is at the bottom of the line, the object is below our orbit. The color is the relative 'threat' that the object represents.)
The scary part is, although astronomers have mapped out where quite a few of the asteroids are, their efforts have only shown us a fraction of what's out there. They estimate that there are up to 1 million asteroids yet to be discovered, and that's only the ones that they figure are the 'potentially hazardous' ones that cross our orbit.
Telescopes on the ground and in orbit constantly scan the skies, but how much warning we have before an asteroid reaches us depends on it size, brightness and distance. The bigger an asteroid is, or the more sunlight it reflects, the easier it is to spot it, and we can find these ones much further away. The smaller an asteroid gets, and the less light it reflects, the harder it is, and we have to wait until it's much closer to pick it up. Some, like the Chelyabinsk meteor, we don't see coming at all until they're exploding above one of our cities.
In that case, part of the problem with detecting it was that it basically pulled an old fighter-plane dogfight strategy, which was to dive at us from out of the Sun. Coming at us from that direction, telescopes would only see its dark side as it tumbled towards us, and pointing the infrared sensors of the WISE telescope (Wide-field Infrared Survey Explorer) towards the Sun would overload them.
That's where private companies like the B612 Foundation are stepping in, with their Sentinel mission. Sentinel will put a space telescope into orbit around the Sun, circling it at roughly the same distance as the planet Venus. This telescope will scan space out towards our orbit and act as a spotter for any asteroids, like the Chelyabinsk meteor, that are headed our way but are hidden from our view by the bright light of the Sun.
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The threat of asteroids is a pretty serious one. We've heard a lot about them in the news lately — like in Chelyabinsk, and concerns over a possible impact by Apophis in 2036, and about the close flyby of 2012 DA14 — and we certainly have evidence of impacts happening in the past (talk to the dinosaurs... oh wait). This isn't something we necessarily have to be living in fear of at all times, but we definitely can't ignore it, as something big is going to hit us again, eventually.
If you want to help, head over to add your support to Planetary Resources' for their ARKYD space telescope. This company plans on mining asteroids, and that could, ultimately, be the best way to defend ourselves against them. This will not only clear out our orbit of these potentially dangerous space rocks, while gaining valuable resources in the process, but also bring into existence a network that will let us intercept any new dangers more easily, and whittle them down to a more manageable size.
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