Brace yourselves! Asteroid 2024 YR4, a hefty rock measuring 40 to 100 meters, could threaten Earth in December 2032. While there's only a 2% chance of impact, this “city destroyer” could unleash an explosion equivalent to 8 million tons of TNT. Key at-risk regions include parts of South America, Asia, and Africa. Currently ranked a cautious level 3 on the Torino scale, ongoing monitoring aims to refine its trajectory. However, the UN has activated emergency protocols, and innovative defense strategies are in development, inspired by NASA's successful DART mission.
How should we prioritize asteroid defense strategies given the risks?
Source:
https://www.wired.com/story/asteroid-2024-yr4/
This asteroid might not hit Earth in 2032 after all—here’s how we know
Space agencies have systems in place to spot, track, and forecast the future orbits of potentially hazardous asteroids.
A newly discovered near-Earth asteroid called 2024 YR4 is one possibly perilous object: It’s a 130 to 300-foot long rock that could impact somewhere on Earth on December 22, 2032.
To be clear, there is no need to hurriedly invest in a hardened bunker. This asteroid is certainly worth watching because it could devastate a city with a direct hit—even on the small side of its size estimate. At one point, the rock had a 3.1 percent chance of a violent rendezvous with Earth—the highest ever recorded. The odds have since
fallen to 1.5 percent and will most likely, drop precipitously to zero, as astronomers gather more data on the future orbit of 2024 YR4. (There's also small chance, 0.8 percent, that the rock could hit the moon.)
Observatories all over the world contribute to finding near-Earth objects. And both NASA and the European Space Agency (ESA) have developed automated software programs that can, with extreme precision, track every single potentially hazardous asteroid and comet found to date. One of the key tenets of planetary defense is to find Earthbound asteroids before they find us.
Asteroid scouts and sentries
Any telescope on the planet can contribute to planetary defense: If an astronomer anywhere on Earth spies an object that looks like an asteroid (or comet), they can report its findings to the planetary defense community. But it’s worth noting that NASA
has a network of telescopes around the world dedicated to hunting down undiscovered asteroids and comets. A telescope in Chile—part of one such NASA-funded facility, the Asteroid Terrestrial-impact Last Alert System (
ATLAS)—discovered 2024 YR4, on December 27 last year.
Once an observatory first spots a previously undiscovered asteroid, astronomers report the find to the Minor Planet Center in Cambridge, Massachusetts, a sort of public notice board for astronomers to peruse. Then, interested astronomers can use those initial observations to track it with their own telescopes. When a new object is discovered, NASA and ESA’s asteroid and comet-tracking groups jump into action. NASA has the Center for Near Earth Object Studies (
CNEOS), while ESA has the Near-Earth Object Coordination Centre (NEOCC).
As both essentially do the same thing, let’s focus on CNEOS.
Initially, an automated computer program named
Scout uses the available crop of observations to plot out the object’s likely future orbits. With just a few data points to go on at first, these orbit forecasts have a high level of uncertainty, but Scout’s job is to calculate if there is any chance whatsoever that this object may impact Earth within the next month or so. If the object doesn’t pose an immediate impact risk, and it’s a real asteroid, NASA’s
Sentry program takes the reins. This automated software calculates if there is a chance, high or low, that the asteroid could impact the planet within the next century, using every new observation of the asteroid to continually update its predictions.
Sentry uses the gravitational pulls of the Sun and the solar system’s planets to work out the possible future orbits of an asteroid. It can also determine how a force called the
Yarkovsky effect can gradually change an asteroid’s motion, changing its long-term orbit.
“Thanks to the Sentry results, we can make sure observers track the asteroids that could pose a risk,” says
Davide Farnocchia, a navigation engineer at CNEOS in California. And until an asteroid poses an essentially zero chance of impacting Earth, it remains on the
Sentry Risk List.
Based on early estimates, 2024 YR4 was at the top of that list, though it has since fallen from the top spot.
Additionally, “2024 YR4 will make another close approach with Earth in 2028, at about 20 times the distance between the Earth and the Moon,” says Farnocchia. “Adding two months of tracking will greatly improve the knowledge of its future position in 2032, and it is likely that an impact in 2032 will be ruled out by the end of this observing window.”
Infrared eyes are on the horizon
Infrared astronomy could refine such observations even further. In infrared light, asteroid sizes become clear; a larger asteroid, no matter how reflective or dull its surface is, always
glows brighter in infrared than a smaller asteroid, meaning this can be used to accurately calculate an asteroid’s dimensions.
NASA’s Near-Earth Object Surveyor—an infrared, space-based observatory solely dedicated to hunting asteroids—will be launched in the next few years, to the excitement of many planetary defenders.
In the meantime, researchers have found that the
special infrared filters on the multipurpose James Webb Space Telescope (JWST) can also be used to find small asteroids and precisely determine their size. With optical light telescopes starting to struggle as 2024 YR4 fades from view, “it seems like JWST would be a fantastic fit,” says
Cristina Thomas, an astronomer and planetary defense researcher at Northern Arizona University.
“Asteroids get much brighter in the infrared than in the visible as they move away from Earth, and they are thus easier to detect or track with infrared facilities—JWST being the biggest of all,” says
Julien de Wit, a planetary scientist at the Massachusetts Institute of Technology.
Astronomers—including Rivkin, Farnocchia, Thomas, and de Wit—quickly put forward a
proposal requesting JWST’s use to refine the size of 2024 YR4 and help ensure its monitoring. On February 5, they received a green light, and now, the most expensive space observatory in will soon be used for planetary defense purposes.
The notion that there is even the slightest chance that 2024 YR4 may endanger us may create some anxiety. But thanks to the planetary defenders at NASA, ESA and beyond, the world has never been safer from dangerous asteroids—and with continued investment in their staff and technology, all eight billion of us will remain protected for generations to come.
Source:
https://www.nationalgeographic.com/...itorial::add=Daily_NL_Tuesday_Health_20250225
