Doomsayers, rejoice! Ukrainian astronomers have discovered Earth's new most dangerous space threat - a 410m-wide asteroid that will skim through our region of space twice between on 2032 and 2047.
To keep track of dangerous so-called Near-Earth Objects (or NEOs) there's a standardised ranking system known as the Torino scale. Zero means something isn't a threat, ten means a definite impact is expected. 2013 TV135 - as this terrifying new asteroid has been dubbed - has been bumped up to a whopping one out of ten, making it the joint-most dangerous threat to Earth that we know of. The other asteroid ranked at a danger level of one out of ten (as you can see on Nasa's Near-Earth Object Program site) is 2007 VK184. That one will pass near to Earth four times between 2048 and 2057.
However, before you start shopping for bomb shelters, it's always worth putting discoveries like this in context, especially since the Chelyabinsk meteor last year. That really was a scary event, a once-in-a-few-decades object that, this time, exploded over a heavily-populated area instead of the more usual oceans, deserts and other empty parts of this world where we don't notice.
That meteor is estimated to have been between 17 and 20 metres in diameter, and weighed about 10,000 tonnes. Compared to that, 410 metres sounds absolutely massive, and if it is that big - there's every chance that further readings will reduce that - it will post a serious risk to humanity's existence.
But, consider that its current chance of hitting us is somewhere in the region of one in 63,000. That's not very good. 2007 VK184 has a better shot of of an impact, at one in 1,750, but those are still, quite literally, astronomical odds.
It's very similar to the one in roughly 2,000 chance that the 5km-wide comet ISON had of hitting Mars (as estimated earlier this year), a possibility that left some scientists very excited. The chance to see an enormous bit of ice and rock smash into another planet - one that we have cameras and sensors trained on thanks to rovers and satellites - would have been extremely useful to observe. Even if it missed, a close pass by a comet that big should have looked pretty spectacular, and scientists expected ISON to put on quite a glorious show.
In the end, though, this is what ISON looked like:
See that white speck in the middle of those panels? That's ISON, as it flew past Mars this month. One of the most anticipated comets in years turned out to brighten a lot less than we thought, and the result was, well, that. A speck.
This is all to show that predicting asteroids and comets is a tricky business, but it's something we're getting a lot better at. We tend to spot the really big ones a long way in advance, and the organisations around the world which work to track them - which, along with Nasa, includes everything from the European Space Agency's Gaia mission to the work of the non-profit B612 Foundation and its Sentinel project - are pretty sure that we won't get caught out by anything like the asteroid that is presumed to have killed off the dinosaurs.
The problem is the smaller ones, the ones smaller than 100m. Those ones can knock out cities and towns out of nowhere (see: Chelyabinsk), and we think there are probably around 4,700 of those still out there that we haven't found. Compared to that risk, 2013 TV135 is almost small-fry - and it's a good sign that we've found it so early.