By early 2026, YR4 was racing away and had become extraordinarily faint. Many astronomers expected it to stay out of sight until 2028. Then a team found two slim chances for Webb to catch it against a relatively uncluttered patch of sky.
The telescope’s view is tiny, so pointing mattered enormously. Researchers used the precise positions of background stars mapped by ESA’s Gaia mission to identify the asteroid’s faint speck and measure it accurately.
Imagine finding one drifting grain of pepper through a drinking straw, using distant porch lights as landmarks. Those observations were enough to forecast a passage just 13,200 miles above the Moon nearly seven years in advance. Not bad work for a dot most of us would never notice.