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Matías S. Zavia
WriterAerospace and energy industries journalist at Xataka.
Alba Mora
WriterAn established tech journalist, I entered the world of consumer tech by chance in 2018. In my writing and translating career, I've also covered a diverse range of topics, including entertainment, travel, science, and the economy.
The James Webb Space Telescope has recently observed its smallest object in history: asteroid 2024 YR4. There’s a good reason why the space telescope is closely monitoring it. Earlier this year, NASA and the European Space Agency’s (ESA) planetary defense systems flagged 2024 YR4 as potentially hazardous.
Initial measurements. Webb’s Near Infrared Camera captured images showing reflected light from the asteroid. Meanwhile, the Mid-Infrared Instrument measured its thermal light.
These observations have enabled astronomers to determine that 2024 YR4 has a diameter of 200 feet, roughly equivalent to the height of a 15-story building. Notably, the asteroid exhibits thermal characteristics similar to larger celestial bodies, likely due to its rapid spin or the absence of regolith (fine sand) on its surface. Instead, it seems to comprise rocks the size of a fist or even larger.
It won’t hit the Earth. The initial observations from Webb, which began on March 8, have confirmed NASA and ESA’s previous calculations: 2024 YR4 poses no threat to our planet. The probability of the asteroid crossing paths with Earth in December 2032 is now just 0.0011%.
This is a significant drop from an earlier probability of 3.2%, when there wasn’t enough data to narrow down the asteroid’s trajectory. As a result, the United Nations won’t need to coordinate with space agencies for potential diversion or evacuation efforts.
It might hit the Moon, though. Webb has confirmed that there’s a 3.8% chance of the asteroid 2024 YR4 colliding with the Moon. This is a small probability, with a 96.2% chance that it won’t occur. Interestingly, astronomers are actually hopeful for the impact.
Should the asteroid hit the Moon, it wouldn’t pose any danger to humans. Instead, it would provide an opportunity for astronomers to observe the impact in real time. They could study its effects on the lunar surface and analyze the material that’s ejected as a result.
Natural asteroids colliding with the Moon aren’t uncommon. However, predicting their impacts can be challenging, especially when their mass and velocity are unknown. In contrast, asteroid 2024 YR4 offers a unique chance for a controlled experiment due to the extensive data scientists have already collected about it.
Hoping for a Moon hit. “Part of our motivation to continue observing this asteroid specifically is to figure out, is that number gonna go up or is it also going to go to zero,” astronomer Andrew Rivkin told New Scientist. Rivkin is among several Johns Hopkins University scientists who requested observation time on the James Webb Space Telescope for 2024 YR4.
Astronomer Alan Fitzsimmons from Queen’s University Belfast in the United Kingdom echoed this sentiment. “We’ve got our fingers crossed for a moon impact. It would have no effect on Earth, but would allow us to study the formation of a lunar crater by a known asteroid for the very first time,” he explained.
Images | NASA | NASA/ESA/CSA
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