25 Asteroids
Nasa has given Earth the all clear on the chances of an asteroid called Apophis hitting our planet any time in the next century, having worried space scientists for over 15 years.
The 340-metre (1,100ft) chunk of space rock hit the headlines in 2004 after its discovery led to some worrying forecasts about its orbit. It became a “poster child for hazardous asteroids”, according to one Nasa expert.
It was supposed to come frighteningly close in 2029 and again in 2036. Nasa ruled out any chance of a strike during those two close approaches a while ago, but a potential 2068 collision still loomed.
But new telescope observations mean that collision has been ruled out and Apophis has been officially taken off the US space agency’s asteroid “risk list”.
Apophis will come within 32,000km (20,000 miles) of Earth on Friday 13 April 2029, enabling astronomers to get a good look. That is about one-tenth of the distance to the moon and closer than the communication satellites that encircle the Earth at 36,000km.
Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there. Apophis belongs to a group known as the Aten family. These do not belong to the asteroid belt and spend most of their time inside the orbit of the Earth, placing them between our planet and the sun.
That makes them particularly dangerous because they spend the majority of their orbit close to the sun, whose overwhelming glare obscures them to telescopes on Earth – rather like a second world war fighter ace approaching out of the sun.