ELEVEN asteroids with the potential to cause "unprecedented devastation" could hit Earth, astronomers have revealed.
If that didn't worry you enough, experts say Nasa didn't know about these potential impacts until the study was complete.
The asteroids were flagged as potentially destructive by a supercomputer working together with "neural network".
What made life difficult for Nasa was that the objects in question have a "chaotic" orbit – making their paths tricky to track.
Each of the 11 asteroids is wider than 100 metres (330 feet), which means they could cause major damage if they crashed into Earth.
"For perspective, Tunguska object which flattened 2000 square kilometers of forest in Siberia was estimated to have a diameter of between 50 and 80m," the study authors, from Leiden University, wrote.
They developed a system called the Hazardous Object Identifier, or HOI.
It's designed to spot hazardous objects known to scientists – but that weren't previously classed as dangerous.
Amazingly, they discovered that 11 asteroids will come closer than 10 times the distance between the Earth and Moon between 2131 and 2923.
These asteroids range between 100 and 236 metres.
The researchers say they all "have the potential of causing regional devastation unprecedented in human history" based on their size, if they were to impact Earth.
It now means the asteroids can be reclassified as hazardous.
"That these asteroids have not previously been identified as potentially dangerous is because the orbit of these asteroids is so chaotic," Leiden University explained.
"As a result, they are not noticed by the current software from space organisations, which is based on probability calculations that use expensive brute force simulations."
To identify the asteroids, a supercomputer was used to map the orbits of the Sun and its planets forward in time for 10,000 years.
These orbits were then traced back in time, while asteroids were launched from the Earth's surface.
During the backwards calculation, asteroids were included in simulations to study orbital distributions today.
This allowed the experts to create a database of hypothetical asteroids that researchers knew would land on Earth.
And these imaginary asteroids can then be linked to real asteroids we already know about.
Used a supercomputer to integrate the orbits of the Sun and its planets forward in time for 10,000 years
then they traced the orbits back in time while launching asteroids from the Earth's surfaces
during backwards calculation, included asteroids in simulations to study orbital distributions at today's date
this allowed them to create a database of hypothetical asteroids that researchers knew would land on Earth
"If you rewind the clock, you will see the well-known asteroids land again on Earth," said Simon Portegies Zwart, an astronomer and simulation expert with Leiden University.
"This way, you can make a library of the orbits of asteroids that landed on Earth."
The library of asteroids was then used as training material for the neural network, which identified hazardous asteroids in the real world.
What's the difference between an asteroid, meteor and comet?
Here's what you need to know, according to Nasa…
- Asteroid: An asteroid is a small rocky body that orbits the Sun. Most are found in the asteroid belt (between Mars and Jupiter) but they can be found anywhere (including in a path that can impact Earth)
- Meteoroid: When two asteroids hit each other, the small chunks that break off are called meteoroids
- Meteor: If a meteoroid enters the Earth's atmosphere, it begins to vapourise and then becomes a meteor. On Earth, it'll look like a streak of light in the sky, because the rock is burning up
- Meteorite: If a meteoroid doesn't vapourise completely and survives the trip through Earth's atmosphere, it can land on the Earth. At that point, it becomes a meteorite
- Comet: Like asteroids, a comet orbits the Sun. However rather than being made mostly of rock, a comet contains lots of ice and gas, which can result in amazing tails forming behind them (thanks to the ice and dust vapourising)
The good news is that simulations like these can be wrong.
So don't panic just yet: we'll have a much better idea about the potential impact of these asteroids in the centuries to come.
"We now know that our method works, but we would certainly like to delve deeper in the research with a better neural network and with more input," Simon explained.
"The tricky part is that small disruptions in the orbit calculations can lead to major changes in the conclusions."
This research was published in the Astronomy and Astrophysics journal.
In other news, Elon Musk has vowed to send four "space tourists" into Earth's orbit as soon as next year.
A supersonic Nasa X-plane that's as quiet as the "thump of a car door" is nearly ready.
Nasa has unveiled the design of a moon lander that could be taking astronauts back to the lunar surface by 2024.
And Nasa recently revealed a surreal photo of Earth taken from 4billion miles away.
Do you ever worry about an asteroid apocalypse? Let us know in the comments!
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