\n<\/p>\n
You may hear about a large asteroid headed toward Earth. Don\u2019t panic.<\/p>\n
Just after Christmas Day, astronomers spotted something zipping away from Earth: a rock somewhere between 130 feet and 330 feet long that they named 2024 YR4. Over the next few weeks, they simulated its possible future orbits. They now say, based on the most up-to-date information, that there is a 1.3 percent chance that this asteroid will strike somewhere on Earth on Dec. 22, 2032.<\/p>\n
Should this keep you up at night?<\/p>\n
\u201cNo, absolutely not,\u201d said David Rankin, a comet and asteroid spotter at the University of Arizona.<\/p>\n
The object\u2019s current odds of striking Earth may sound scary \u2014 and it\u2019s fair to say that an asteroid in this size range has the potential to cause harm. Should it strike a city, the damage would not cause anything close to a mass extinction, but the damage to the city itself would be catastrophic.<\/p>\n
But a 1.3 percent chance of a hit is also a 98.7 percent chance of a miss. \u201cIt\u2019s not a number you want to ignore, but it\u2019s not a number you need to lose sleep over,\u201d Mr. Rankin said.<\/p>\n<\/div>\n<\/div>\n
And the odds may diminish over time, as astronomers gather new data about the object.<\/p>\n
For now, experts say, calm is warranted. The asteroid has been spotted several years ahead of its close shave with Earth \u2014 and that\u2019s a good thing.<\/p>\n
\u201cThe international systems we\u2019re putting in place to find, track and characterize \u2014 and, if it comes to it, mitigate the impacts of \u2014 hazardous asteroids and comets are working as intended,\u201d said Andy Rivkin, an astronomer and planetary defense researcher at the Johns Hopkins Applied Physics Laboratory in Maryland.<\/p>\n
Here\u2019s what you need to know about 2024 YR4.<\/p>\n
It was identified by the Asteroid Terrestrial-impact Last Alert System, or ATLAS, four telescopes around the world that hunt near-Earth objects and are funded by NASA. Its telescope in Chile found 2024 YR4 on Dec. 27, just two days after a close approach to Earth.<\/p>\n
It\u2019s now speeding away from the planet and getting fainter by the day.<\/p>\n<\/div>\n<\/div>\n
According to the European Space Agency\u2019s Near-Earth Object Coordination Centre, it is between 130 and 330 feet long. This size range is based on the amount of sunlight it is reflecting. Without knowing exactly how reflective 2024 YR4\u2019s surface is, only a range of sizes can be given.<\/p>\n<\/div>\n<\/div>\n
A more accurate estimate could be made using radar, but that won\u2019t be possible until the asteroid makes another close, but perfectly safe, pass by Earth on Dec. 17, 2028.<\/p>\n
Yes.<\/p>\n
A 130-foot asteroid is comparable to the Tunguska impactor, a meteor that exploded over a remote patch of Siberia in 1908 and decimated an 800-square-mile forest (that\u2019s over twice the size of New York City). A 330-foot asteroid would cause far greater localized damage: A strike on a city would destroy much of it. If the object survives its journey through the atmosphere and strikes the ocean just offshore, the resulting tsunami could devastate nearby coasts.<\/p>\n
The Center for Near-Earth Object Studies, at NASA\u2019s Jet Propulsion Laboratory in California, is home to America\u2019s asteroid and comet cartographers. Using sophisticated software, they track the motion of all known near-Earth objects.<\/p>\n
One of their programs, Sentry, assesses the possible orbits of known near-Earth objects and determines whether they stand even a tiny chance of striking Earth within the next century. Those whose impact odds cannot be confidently reduced to (essentially) zero remain on the Sentry Risk List.<\/p>\n
\u201cThe possibility that 2024 YR4 might impact in 2032 was identified right after discovery,\u201d said Davide Farnocchia, a navigation engineer at the NASA center. But based on just a few observations, the prediction uncertainties for 2032 were initially very large. As the number of observations grew to the hundreds, he said, \u201cthe impact probability has gradually increased over the last month and has now surpassed 1 percent, an important threshold.\u201d<\/p>\n<\/div>\n<\/div>\n
The Torino Scale is a tool for communicating how concerned the public and policymakers should be about an asteroid. It ranges from 0 (the likelihood of a potentially deadly collision is effectively zero) to 10 (a collision is certain and may imperil all of human civilization).<\/p>\n
2024 YR4 currently sits at 3: a close encounter, less than a decade away, meriting attention by astronomers, one that has a chance of 1 percent or greater of a collision capable of localized destruction.<\/p>\n
This is the second-highest rating ever given to an asteroid. Only Apophis, an asteroid once thought to be a threat, briefly reached a 4. But as we learned more about Apophis, we found it had no chance of striking Earth for at least a century.<\/p>\n
What normally happens is that the impact odds plummet to zero as more observations come in and the asteroid\u2019s orbit is better known with more precision.<\/p>\n
The same story will probably unfold with 2024 YR4. \u201cThe most likely outcome is that further observations will rule out an impact,\u201d Mr. Rankin said.<\/p>\n<\/div>\n<\/div>\n
2024 YR4 is getting extremely faint as it travels away from Earth, meaning most telescopes are going to struggle to track it. \u201cHowever, given this is a special case, members of the community have requested (and received) time on some of the larger and more capable facilities,\u201d Dr. Rivkin said. \u201cThose should do OK through April.\u201d<\/p>\n
Astronomers will also have an even greater opportunity to refine their predictions during the December 2028 flyby. But until then, it\u2019s possible that an impact in 2032 won\u2019t be entirely ruled out.<\/p>\n
\u201cWe expect the impact probability to go to zero rather than 100 percent,\u201d Dr. Rivkin said. \u201cBut it may take a few years before we get the data to show that.\u201d<\/p>\n
No, not at present. It\u2019s very likely to miss the planet in 2032.<\/p>\n
And if we find out that it will hit, \u201cwe might be able to do something about it,\u201d Mr. Rankin said.<\/p>\n
One option, if space agencies had enough time to mount an operation, would be to attempt to alter the asteroid\u2019s path by crashing a spacecraft into it.<\/p>\n
If that failed, or wasn\u2019t possible, and governments worked out a precise impact location, they could evacuate people who might be at immediate risk.<\/p>\n