Apophis the asteroid edges closer

Near earth objects that get a bit close for comfort, and what we can do about them
24 November 2020

Interview with 

Adam Murphy


An image of a spiral galaxy


On Friday the 13th of November - yes really! - an 11m asteroid skimmed through our outer atmosphere. But astronomers only spotted 2020 VT4 the following day! There was also news out this week that the Sun is pushing another asteroid, called Apophis, closer to us over the next 50 years than we’d like. Adam Murphy has been looking at objects in space like these that come a little too close for comfort...

Adam - Space is big. Really, really big. And it's also, as you might've noticed at night, pretty dark. That means there's a lot of room for things to be hiding out there in the black of space. Some of those things are asteroids and comets, and some of those often get closer to earth than you might think. Objects that get near to earth are called, imaginatively, Near-Earth objects, and they can get close. In 2004 an asteroid about five meters across shot by us, flying below some of our satellites. And if they were to hit, they could cause some real damage. It was an asteroid that killed the dinosaurs after all. And in 2013, a bus-sized object exploded in the skies near Chelyabinsk in Russia. It blew out windows and caused tens of millions of pounds of damages. So it's important to be vigilant.

Many of these objects come from the asteroid belt, which is a belt of asteroids that sits between Mars and Jupiter. Usually, those rocks are content to just sit out there, but sometimes there are big collisions between them and those collisions can send some pretty big pieces of debris our way. Once they've been knocked out of the asteroid belt they continue to orbit the sun, but in long loopy, very oval-shaped orbits. And those orbits can intersect with the Earth's orbit. The gravity of the earth and the sun can even help bring the asteroid back around, like a wasp that refuses to leave you alone on a summer's day. And because space is really dark, we don't always see these things. In 1989 another asteroid call 4581 Asclepius was as close as 700,000 kilometres away, which is about twice the distance between the earth and the moon. But if it had hit, it would have devastated the planet and we didn't detect it until it was nearly on top of us.

One asteroid, in particular, has been on our radar for quite some time and will be ignoring Earth's personal space on several occasions in the next few decades. It's called 99942 Apophis. Supposedly it's called that because the discovers were fans of the Stargate SG-1 TV show, and named it after one of the big baddies. It's certainly how I know the name anyway! It's about the size of the Eiffel tower, and in 2029, will pass under some of our satellites. And it will get close again in 2036, and then again in 2068, although the further into the future you go, the less certain the details are. For a while, this was looking like the most likely contender to hit the planet and cause some damage. At one point, it ranked a 4 on what's called the Torino scale where 1 is "we're fine and there's nothing to worry about", and 10 is "we should prepare for everything to turn into Madmax now."

But there are plans to deal with anything coming our way. The old plan was to just blow it up with a nuclear device but as the general says in one of my favourite movies, Independence Day, that risks turning one dangerous object into many. The new plan is to just give them a push. NASA has a mission planned called the double asteroid redirection test, which will launch in the middle of next year and is going to a pair of asteroids called 65801 Didymos, to test our rock pushing capabilities. Severe asteroid impacts are only predicted to happen once every hundred thousand years, but if we should win the worst galactic lottery and that's going to happen soon well, because I don't know about you, but I wouldn't last too long in a post-apocalyptic wasteland.


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