Free Astronomy Magazine November-December 2025

9 ASTRO PUBLISHING NOVEMBER-DECEMBER 2025 A n artist's impression of Japan’s Hayabusa2 space mission touch- ing down on the surface of the aster- oid 1998 KY 26 . New observations with ESO’s Very Large Telescope (VLT) have revealed that 1998 KY 26 is just 11 m wide, almost three times smaller than previously thought, and is spin- ning once every 5 minutes, which is much faster than expected. The image above shows an updated size com- parison between the asteroid and spacecraft. [ESO/M. Kornmesser. As- teroid: T. Santana-Ros et al. Hayabu- sa2 model: SuperTKG (CC-BY-SA)] have revealed that the asteroid is just 11 metres wide, meaning it could easily fit inside the dome of the VLT unit telescope used to ob- serve it. It is also spinning about twice as fast as previously thought: “One day on this asteroid lasts only five minutes!” he says. Previous data indicated that the asteroid was around 30 metres in diameter and completed a rotation in 10 minutes or so. “The smaller size and faster rotation now measured will make Hayabusa2’s visit even more inter- esting, but also even more challeng- ing,” says co-author Olivier Hainaut, an astronomer at ESO in Germany. This is because a touchdown ma- noeuvre, where the spacecraft ‘kisses’ the asteroid, will be more difficult to perform than antici- pated. 1998 KY 26 is set to be the final target asteroid for the Japan- ese Aerospace eXploration Agency (JAXA)’s Hayabusa2 spacecraft. In its original mission, Hayabusa2 explored the 900-metre-diameter asteroid 162173 Ryugu in 2018, re- turning asteroid samples to Earth in 2020. With fuel remaining, the spacecraft was sent on an extend- ed mission until 2031, when it’s set to encounter 1998 KY 26 , aiming to learn more about the smallest aster- oids. This will be the first time a space mission encounters a tiny as-