Near-Earth object watch · Asteroid 2024 YR4
Daily notes, observations, and context as we track asteroid 2024 YR4.
The quick version
About YR4
YR4 is a space rock roughly as wide as a 15-to-20-story building—and on December 22, 2032, it will sweep through the Earth–Moon neighborhood. Early observations gave astronomers a real reason to calculate a possible Earth impact, while later measurements revealed an extraordinary close flyby: about 173,000 miles from Earth and just 13,200 miles above the Moon. It is a rare chance to watch planetary science unfold in real time.
- Expected Earth flyby
- About 173,000 miles 278,000 km from Earth's center
- Chance of hitting Moon
- 4.3% → 0% Webb observations now rule out impact
- Estimated size
- 174–220 feet wide 53–67 meters
Field log
Latest observations
38 reports in the archive
How a Nearly Invisible Rock Rewrote the Planetary‑Defense Playbook
Webb’s faint detection of 2024 YR4 not only ruled out a 2032 lunar strike but showed that space telescopes must now be part of routine follow‑up for the faintest hazards.
Read reportYR4’s 2032 Double Flyby Comes Into Focus
YR4 will thread through the Earth–Moon system in 2032, passing roughly 173,000 miles from Earth and…
Read reportWhat Makes YR4 a Near-Earth Asteroid?
YR4’s stretched orbit carries it back through Earth’s neighborhood, setting up a particularly close…
Read reportWhen YR4’s Earth-Impact Odds Reached 2.8%
For a brief period, real observations put YR4’s 2032 Earth-impact probability at 2.8%, focusing…
Read reportWebb Measured a Speck Smaller Than a City Block
Webb used reflected light and heat to size up YR4—the smallest asteroid it had targeted—ahead of the…
Read reportYR4 and Tunguska: Two Rocks in the 60-Meter Class
The Tunguska object may have occupied the same broad size range as YR4, giving astronomers a rare…
Read reportChelyabinsk Was Smaller—and Still Made a Big Entrance
YR4 is roughly three times wider than the object behind the 2013 Chelyabinsk airburst, making its…
Read reportHow Astronomers Pinned Down YR4’s 2032 Flyby
Hundreds of carefully timed observations turned a moving dot into a forecast for a close passage…
Read report