Astronomers peering through some of the world’s most advanced observatories, including the European Southern Observatory’s Very Large Telescope (ESO’s VLT), have taken a closer look at a mysterious little rock racing through space: asteroid 1998 KY26. What they found has astonished scientists. This small asteroid, once believed to be about 30 meters wide, is in fact nearly three times smaller—just 11 meters across. To put that into perspective, it could fit comfortably inside the dome of one of the telescopes that helped study it.
But size isn’t the only surprise. 1998 KY26 is spinning at a breathtaking pace. A full rotation—a single “day” on this tiny world—lasts only about five minutes. That’s twice as fast as earlier data suggested, making it one of the speediest rotators ever observed among near-Earth asteroids.
These revelations, recently published in Nature Communications, are more than just scientific curiosities. They carry enormous importance for the future of space exploration. In just six years, Japan’s Hayabusa2 spacecraft is set to pay a visit to this tiny, tumbling rock in one of the most ambitious asteroid missions ever attempted.
Hayabusa2’s Grand Journey
Hayabusa2, a spacecraft developed by the Japanese Aerospace eXploration Agency (JAXA), already holds a place in space history. Launched in 2014, it rendezvoused with the 900-meter asteroid Ryugu in 2018, successfully collecting samples and returning them to Earth in 2020. That feat was groundbreaking, offering scientists pristine pieces of early solar system material to study.
But Hayabusa2’s mission didn’t end there. With fuel still in its tanks, JAXA charted a bold extended mission. The spacecraft would venture onward, setting its sights on an entirely new kind of target: the tiny asteroid 1998 KY26, with an encounter planned for 2031. This will be humanity’s first close-up look at such a small asteroid, an object only slightly larger than the space probe itself.
The challenge is immense. As Olivier Hainaut of ESO puts it, “The smaller size and faster rotation now measured will make Hayabusa2’s visit even more interesting, but also even more challenging.” A controlled touchdown maneuver—where the spacecraft briefly “kisses” the asteroid to collect data or samples—becomes vastly more difficult when the surface is spinning so quickly.
A Window Into the Smallest Worlds
Why risk such a difficult mission for a rock barely bigger than a house? The answer lies in what these tiny asteroids represent. Unlike their larger cousins, which have been studied by previous missions, small asteroids like 1998 KY26 are relatively unexplored. Yet they are crucial to our understanding of the solar system.
Tiny asteroids are thought to be remnants of violent cosmic collisions, fragments from larger bodies that once roamed the early solar system. Studying them offers insights into how planets and larger asteroids formed billions of years ago. Because of their small size, they are also more common than large asteroids—and, importantly, they pose unique hazards to Earth.
The Chelyabinsk event of 2013 is a chilling reminder. That year, a 20-meter asteroid exploded over Russia, shattering windows and injuring more than 1,000 people. 1998 KY26 is barely larger than that impactor. By studying such objects up close, missions like Hayabusa2 may help us better prepare for potential future threats.
The Science Behind the Discovery
Unveiling the secrets of an object as small and faint as 1998 KY26 is no easy task. It required precise timing, patience, and some of the most powerful telescopes on Earth. Because the asteroid spends much of its orbit far from our planet, astronomers had to wait for it to pass close enough to Earth to observe.
Using ESO’s Very Large Telescope in Chile’s Atacama Desert—one of the darkest, clearest skies on Earth—astronomers combined new observations with older radar data. What they found shocked them: instead of being a rubble pile loosely held together, as some had suspected, 1998 KY26 appears to be a solid piece of rock with a bright, reflective surface. Still, researchers can’t completely rule out the possibility that it might be a cluster of smaller rocks sticking together.
Toni Santana-Ros of the University of Alicante, who led the study, expressed both excitement and awe: “The amazing story here is that we found that the size of the asteroid is comparable to the size of the spacecraft that is going to visit it! And we were able to characterize such a small object using our telescopes, which means that we can do it for other objects in the future.”
A Glimpse of the Future
The implications of this research extend far beyond a single mission. If astronomers can successfully study an asteroid as small and faint as 1998 KY26 from Earth, they can apply these methods to other near-Earth objects—particularly those that might one day cross paths with our planet. This capability could revolutionize how we prepare for asteroid defense strategies, exploration missions, and even future asteroid mining ventures.
As Hainaut notes, “We now know we can characterize even the smallest hazardous asteroids that could impact Earth, such as the one that hit near Chelyabinsk.” This knowledge doesn’t just deepen our understanding of the solar system—it could help safeguard our planet.
Humanity’s Next Step Into the Unknown
There’s a poetic quality to this mission. A spacecraft, born from human ingenuity, is set to rendezvous with a cosmic pebble hurtling through the void—an encounter between two tiny travelers in the immensity of space.
For scientists, 1998 KY26 represents a chance to answer fundamental questions about the nature of small asteroids. For humanity, it symbolizes our growing ability to reach out and touch the universe, to transform distant specks of light into places of study, wonder, and perhaps one day, survival.
When Hayabusa2 finally meets its minuscule, fast-spinning target in 2031, it will not only be a triumph of engineering but also a testament to the unrelenting human desire to explore the unknown.
More information: Hayabusa2 mission target 1998 KY26 preview: decametre size, high albedo and rotating twice as fast. Nature Communications (2025). DOI: 10.1038/s41467-025-63697-4
