In late January, EarthSky’s Deborah Byrd interviewed asteroid expert Richard Binzel of MIT of MIT – inventor of the Torino Impact Hazard Scale – about a possible strike to Earth by asteroid 2024 YR4. He also talked a lot about the overall picture of how astronomers are keeping Earth safe from asteroid collisions. It’s fascinating stuff. Watch the video here..
UPDATE February 23, 2025. On February 18, 2025, we were up to a 3.1% – or 1-in-32 odds – that asteroid 2024 YR4 would strike Earth on December 22, 2032. But, as of today, the odds have dropped to a 1-in-20,000 chance of a strike. As a consequence, asteroid 2024 YR4 has gone to Level 0 on the Torino Impact Hazard Scale. Meanwhile, the asteroid’s odds of hitting the moon are up! They were at about 1.8% on Sunday, or about a 1-in-56 chance of the asteroid striking the moon’s surface. That would be cool to see, but it’s still highly unlikely.
Inventor of the Torino scale, Richard Binzel, told EarthSky on February 23, 2025:
Asteroid 2024 YR4 has now been reassigned to Torino Scale Level 0: the level for No Hazard. Additional tracking of its orbital path reduces its possibility of intersecting the Earth to below the 1-in-1,000 threshold. That is the established level for downgrading to Level 0. [Editor’s note: Odds of 1-in-1,000 are the threshold for Level 0 for any space object smaller than 100 meters. 2024 YR4 has an estimated size of 50 meters].
2024 YR4 fell to Torino Scale Level 1 (Green ‘Normal’) on February 20, down from Level 3 (Yellow ‘Meriting Attention by Astronomers’).
Level 0 is labeled as the (White) No Hazard zone on the Torino Scale, which considers the two dimensions of impact probability and impact consequence in assigning its Levels. Find the Torino Scale categories full descriptions here.
In detail for the current probability, the NASA JPL Center for Near-Earth Object Studies now lists the 2024 YR4 probability as 0.00005 (0.005%) or 1-in-20,000 for its passage by Earth in 2032.
That’s zero, folks!
Odds of impact increased before dropping
Not long after 2024 YR4’s discovery – in late 2024 – astronomers were saying there was a 1-in-83 chance of a strike. Then the odds went to 1 in 53, then 1 in 43, then 1 in 38, and – at worst – the odds were 1 in 32. That became the new record for an asteroid on the Torino scale, beating the infamous asteroid Apophis in 2004. As we have been saying all along:
It’s likely that the odds will go down to zero with further data.
And now they do appear to be on their way to zero. What has changed? Nothing has changed about this asteroid. It’s still out there, in the inner solar system, pursuing its orbit around the sun. What has changed is our knowledge of the asteroid. Despite the challenge of observing this small object – The asteroid is about 150 feet (46 meters) wide – astronomers have been able to track it and refine our knowledge of its orbit.
That’s despite the fact that asteroid 2024 YR4 is moving away from us now. It’s faint and getting fainter. After another month or so, astronomers won’t be able to track it again until 2028.
The new estimates for 2024 YR4 – showing it is no longer considered a possible threat to Earth – come from NASA’s Center for Near Earth Object Studies (CNEOS) at the Jet Propulsion Laboratory in Pasadena, California.
What about the moon?
Speaking of the moon … scientists have also calculated the odds of the asteroid hitting the moon. Its original rating was smaller than the odds of Earth, at only 0.3%. But then things swung the other way. The odds of it hitting Earth have drastically shrunk. While its odds of hitting the moon have crept up to 1.8% as of February 23, 2025. And think, if it did hit the moon, what a sight that would be!
Asteroid 2024 YR4 is 50 million miles (80 million km) away and getting farther every second. Some observers noticed the asteroid will be somewhat “close” to the Lucy spacecraft, so its team checked to see if 2024 YR4 would be observable by the spacecraft. But – at its closest to Lucy – the asteroid will still be too faint for the spacecraft’s L’LORRI instrument to detect.
Asteroid 2024 YR4 discovered on Christmas Day 2024
Asteroid 2024 YR4 swept into the view of the ATLAS asteroid impact early warning system – with telescopes in Hawaii, Chile and South Africa – on December 25, 2024.
EarthSky spoke with the inventor of the Torino scale, Richard Binzel of the Massachusetts Institute of Technology (MIT), on January 27, 2025. He said:
In all likelihood, this object will fall to Torino Scale 1 and then 0; or directly fall to 0 with more measurements.
2/ The clip below shows ESO’s VLT recent observations of asteroid 2024 YR4, which have helped refine its trajectory. It is estimated to be 40-100 m wide, but more data and analysis are needed to confirm the size, and to refine its trajectory. ? ?
? ESO/O. Hainaut et al.
— ESO (@eso.org) January 29, 2025 at 11:01 AM
An asteroid’s ranking on the Torino scale
The only asteroid ever to have a higher score on the Torino scale was 99942 Apophis. It briefly had a rating of 4 on the Torino Scale in late 2004. And, yes, Apophis caused a stir and earned the nickname of the Doomsday Asteroid. But asteroid Apophis is now just a zero on the Torino scale. That’s because astronomers watched it carefully, refining their knowledge of its orbit. They determined that Apophis has a negligible risk of impact for at least a century.
So, yes, an asteroid’s score on the Torino scale can change – in fact, is likely to change – as astronomers gather more observations of the object and also track its motion around the sun.
If asteroid 2024 YR4 were to strike Earth, it wouldn’t end life on Earth as we know it. It’s not large enough to do that. But it could be locally destructive, depending on where it hits (IF it ever hits). Watch a video of size comparisons in asteroids, here.
So asteroid 2024 YR4 isn’t a world-destroyer. Instead, it’s thought to be similar in size to the object that felled reindeer and flattened some 1,000 square miles (2,600 square km) of forest, in a sparsely populated area near Tunguska, Siberia, in 1908.
What is the Torino scale?
The IAU has been using the Torino Impact Hazard Scale since 1999 to categorize asteroids that could potentially hit Earth. An object – such as 2024 YR4 – with a score of 3 puts it in the yellow zone. This means the object merits attention by astronomers and the public. The description of a score of 3 reads:
A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localized destruction. Most likely, new telescopic observations will lead to reassignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.
In fact, most new asteroids that get listed on the Torino scale have their likelihood of hitting Earth go up with more observations … until it drops to zero. That’s because the uncertain path of the asteroid is wide and more observations shrinks the path, making it look more likely, until the path shrinks enough to show that it will not cross Earth’s. It’s likely that’s what will happen with asteroid 2024 YR4 also.
In 2023, EarthSky spoke with the inventor of the Torino scale, Richard Binzel of the Massachusetts Institute of Technology. He said that we should expect more objects to make the Torino scale as our technology improves, allowing us to see smaller objects we otherwise would have missed.
Asteroid Potential Impact Warning Notification
Because the asteroid passed a slim threshold of hitting Earth, it triggered a Potential Impact Warning Notification on January 29, 2025. That warning came from the International Asteroid Warning Network, a global collaboration of observatories, scientific institutions, and other interested parties, coordinated by NASA.
On January 29, the impact probability was a mere 1.3% as calculated by CNEOS and ESA’s Near Earth Objects Coordination Centre in Frascati, Italy, in cooperation with the NEO Dynamic Site (NEODyS-2), also in Italy.
The notice gives the potential date of impact as December 22, 2032, and lists the possible impact locations (from across the eastern Pacific, northern South America, into Africa and southern Asia). Because it’s currently so dim and far away, size estimates vary from 130 to 300 feet (40 to 90 m). If it were to strike Earth, it would cause “severe blast damage.” Specifically, the blast damage could occur as far as 30 miles (50 km) from the site of impact. And finally, the notice said:
The asteroid will be observable, and information will be updated, through early April 2025 and then again starting in June 2028 when the asteroid will return to the vicinity of Earth.
Asteroid 2024 YR4 presents a challenge
Asteroid 2024 YR4 presents a challenge to observations, however. The potential for an impact is still seven years away, but the asteroid is moving into a position where astronomers will not be able to observe it for about three years. At the moment, the asteroid is exceedingly faint at magnitude 23. It is expected to continue to dim throughout February until it leaves our view.
With the current data astronomers have on the asteroid, they estimate not just one possibility for impact in 2032, but seven possibilities between 2032 and 2079. The first possible impact date is December 22, 2032. Again, as more observations come in, this information will change.
Future observations
What if further observations of asteroid 2024 YR4 did determine that it will collide with Earth on December 22, 2032? To start with, the first potential impact is still years away. And we’ve already sent a mission to hit and move an asteroid as a test of our planetary defense system. That mission was the Double Asteroid Redirection Test (DART), which impacted with an asteroid’s moon named Dimorphos in 2022.
And Dimorphos was much larger than asteroid 2024 YR4, at 525 feet (160 meters) across.
If asteroid 2024 YR4 were to strike Earth, we are (at least somewhat) prepared!
Bottom line: On February 23, 2025, new observations of asteroid 2024 YR4 have led NASA’s Center for Near Earth Object Studies to decrease the odds of the asteroid hitting us in 2032 to 1 in 20,000.
Via:
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