NASA has issued a huge update on the “city-killer” asteroid hurtling in Earth’s direction – and the odds of a collision have jumped drastically.
After being discovered in December, YR4 shot to the top of Nasa’s asteroid risk list – and was judged to have an alarming 1-in-32 chance of smashing into us.
The chance of YR4 smashing into Earth has been adjusted majorly[/caption]
The space rock was pictured in this grainy telescope image[/caption]
If YR4 hits Earth, the collision would be powerful enough to destroy an entire city[/caption]
But the odds constantly changed as scientists analysed the rock – and have done again.
Nasa now believes YR4 has just a 1-in-26,000 chance of striking Earth – meaning there is a 99.9961 per cent chance the rock will sail on past.
It will still pass near Earth in 2028 – around 5 million miles away – and then again in December 2032, which was the approach causing such alarm.
However, scientists now think there will be 167,000 miles of clear sky – and no Christmas collision.
If YR4 – estimated between 40m and 90m wide – did strike Earth, it would pack a punch equivalent to eight billion kilos of TNT, scientists calculated.
It would blow a 1.2mile-across crater into the Earth’s crust, and a terrifying simulation showed what the impact might look like.
YR4 had been graded as level three on the Torino scale – the system used since 1999 to categorize potential Earth impact events.
This emergency level means: “A close encounter, meriting attention buy astronomers. Current calculations give a one per cent or greater chance of collision capable of localised destruction.”
However, the new, much lower chance of collision means YR4 slides back down to level zero.
Any event with a less than 1-in-1000 chance of occurring falls within this band.
Richard Binzel, Professor of Planetary Science at the Massachusetts Institute of Technology (MIT), who created the Torino scale, said: “The NASA JPL Center for Near-Earth Object Studies (CNEOS) now lists the 2024 YR4 impact probability as 0.00005 (0.005%) or 1-in-20,000 for its passage by Earth in 2032.
“That’s impact probability zero folks.”
Another part of the level three description says: “Most likely, new telescopic observations will lead to re-assignment to level zero.
“Attention by public and public officials is merited if the encounter is less than a decade away.”
The chance of an impact is now projected as much less likely[/caption]
So, YR4’s descent to level zero has conformed with the Torino scale’s predictions.
The odds for YR4 striking Earth began at 1-in-83, before steadily reducing to a trough of 1-in-32.
The projected odds have moved around as scientists gathered more data on the speeding asteroid.
The calculations mapping the rock’s path include a lot of mathematical uncertainty, but this is reduced as more data is collected – allowing for more accurate predictions.
Asteroid hunter David Rankin, of the Catalina Sky Survey, knew from the outset the odds of a collision would rise and then fall, and explained why the figures change.
He told Space.com: “Imagine holding a stick that is a few feet long. If you move the stick in your hand a fraction of an inch, you hardly notice any movement on the other end.
“Now imagine that stick is many millions of miles long. Moving your hand a fraction of an inch will cause dramatic changes on the other end.”
The near-certainty that YR4 will pass by without incident will push it out of public conversation, Binzel said, but there are some lessons to take away from the debacle.
Near-Earth asteroid, computer artwork.[/caption]
He told the website: “As 2024 YR4 fades away from the news cycle, I think there is an overall context that is the most important takeaway news.
“An object the size of YR4 passes harmlessly through the Earth-moon neighbourhood as frequently as a few times per year.
“The YR4 episode is just the beginning for astronomers gaining the capability to see these objects before they come calling through our neck of the woods.”
He warned there will be future asteroids that, initially, will be calculated as having a high chance of smashing into Earth.
Binzel added: “But, just like YR4, with a little time and patient tracking, we will be able to rule out entirely any hazard.
“This means that objects with low categories on the Torino Scale are likely to be a common occurrence, of interest to space enthusiasts and astronomers for follow-up, but not particularly newsworthy.”
Binzel concluded: “Rather than making anyone anxious, by finding these objects that are already out there and pinning down their orbits, we are becoming more secure in our knowledge that any sizable asteroid is not likely to take us by surprise.”
