A CITY-KILLER asteroid could be hurtling towards Earth but going completely undetected, a space agency chief warned.
Humanity has only just recovered from the near-miss of asteroid YR4, which threatened to blow huge hole into Earth’s crust.
The Chelyabinsk asteroid burned up as it shot through the atmosphere in 2013[/caption]
An ‘city-killer’ asteroid could be heading for Earth – but obscured from view by the Sun[/caption]
If YR4 did hit our planet, it would have packed a punch equivalent to eight billion kilos of TNT, scientists calculated.
But there could be another asteroid like YR4 – or worse – lurking in our blind spot, an astronomer has warned.
The problem is, we still don’t have the tech to let us search the space between Earth and the Sun – because it is simply too bright.
To get around the issue, the European Space Agency (ESA) is building a cutting-edge planet-defence system that will boost our space vision.
Luca Conversi, an ESA scientist, told The Sun there is “a chance that something the size of YR4 is approaching from the Sun, but we just haven’t detected it”.
That’s how the last major asteroid to hit Earth slipped through through the net.
It went “completely undetected, because it came from the direction of the Sun”, Luca explained.
He’s talking about the Chelyabinsk meteor, an asteroid which scorched through Earth’s atmosphere in 2013 and smashed through the icy plains of southern Russia.
Luca said: “It didn’t hit anything – but it triggered a sonic boom which shattered all the windows in the nearby town Chelyabinsk.
“Hundreds of people who were watching through windows in their homes were injured by the shattering glass.”
Despite the Chelyabinsk wakeup call, we “still cannot detect objects coming from the direction of the Sun”, Luca said.
The ESA says: “Hidden in the glare of our sun are an unknown number of asteroids on paths we cannot track, many of which could be heading for Earth, and we just don’t know it.”
But it has plans to change that.
The Chelyabinsk meteor
ON February 15, 2013, an asteroid scorched through the atmosphere above Russia – the largest meteor to reach Earth since 1908.
It disintegrated about 30km above the ground, as most small asteroids do, due to the pressure of pushing through our atmospheric gases.
The meteor was about 66 feet (20 metres) across, and was travelling at about 43,000mph when it entered.
Russian skies were lit up by light from the explosion, which was briefly brighter than the Sun.
It also emitted a shock wave with the same energy as 500,000 tonnes of TNT.
This force damaged many nearby buildings and injured around 1,200 people – who were mainly cut by shattered glass.
However, it also directly knocked people to the floor and brought down walls.
Fragments of rock from the meteor continued to the ground – some large enough to inflict mini craters.
DEFENCE MISSION
The agency is working with Nasa to develop a floating telescope called Neomir that will let us look straight into that Sun-blocked blind spot.
The name stands for near-Earth orbit mission in the infrared.
Luca said: “It will be between our sun and Earth, and it will detect objects using infrared waves, rather than visible light, so we will be able to see objects in the Sun’s direction.”
It will act as a sentry for those asteroids that can’t be seen from the ground – detecting anything larger than 20 metres across.
The Neomir telescopes will sit between Earth and the Sun, allowing us to see asteroids in the blind spot[/caption]
The telescope is expected to launch into orbit around 2032.
But even away from the Sun’s glare, we’re not able to be watching everywhere, Luca warned.
He said: “We know of fewer than one per cent of the objects the size of YR4. We’ve identified around 40,000 near-Earth objects, but there are millions of them.”
“We’ve spotted basically all of them down to a kilometre across, but far fewer of the smaller ones.
“We still cannot see the whole night sky every night. If the telescope that found YR4 had looked at that bit of sky the next day, it wouldn’t have been detected then.”
A hole in the ice of Chebarkul Lake made by the Chelyabinsk asteroid in 2013 which went undetected by astronomers[/caption]
The sonic boom made by the Chelyabinsk asteroid shattered nearby windows[/caption]
To increase our detecting ability, the ESA is also developing a set of “bug-eyed” telescopes called Fly Eye – directly inspired by insects.
A network of up to four “eyes” spread across the globe will “work together to carry out night sky surveys” and “automatically identify” objects that could be on an Earth-bound collision course, according to the ESA.
Just like a fly’s eye, the telescopes will split incoming light into different channels.
Each light channel is then focussed by a second lens onto a separate detector.
This will allow the telescopes to “watch” a much wider area of the sky.
But Luca admitted: “There’s still a long way to go with the technology before we can identify most asteroids.”
WHAT HAPPENED TO YR4?
For a few weeks, the world watched in horror as the probability of a “city killer” asteroid called YR4 hitting Earth crept up and up.
At the height of the anxiety, Nasa reportedly feared the chances of a collision could rise past 20 percent – before it plunged to almost zero.
Luca explained why the probability of YR4 striking Earth changed so dramatically.
He said: “When we are trying to foresee where an object will be in many years time there is a lot of uncertainty.
“The uncertainty shrinks as we take more data.”
Asteroid 2024 YR4 can be made out as the bright white smudge in the latest telescope photos[/caption]
An asteroid threat like YR4 happens about once every 20 years[/caption]
Luca explained that, to begin with, physicists calculated an area of around a million kilometres where YR4 could travel.
Earth took up about one percent of the possible path zone – so the chance of an impact was said to be one percent.
With more calculations the area decreased.
This meant that Earth took up more of the possible path zone – and so the probability of a strike increased.
That continued until the zone shrank even further, and Earth was eventually outside the possible path.
At that point, the probability plunged to virtually nothing.
Luca said: “That is what happens every single time, unless the object is actually going to hit Earth.”
Even though the process was predictable, Luca said YR4 “was not a false alarm”.
He said a threat like YR4 only comes “once every 20 years or so” – so the world was right to take it seriously.
YR4 now has more chance of hitting the moon than Earth – standing at about 1.7 percent.
Luca said: “If that happened it would be a fantastic thing to see, but wouldn’t pose any danger to us.”
