Hayabusa2 faces challenge as asteroid 1998 KY26 spins faster than expected

An artist’s impression shows Japan’s Hayabusa2 spacecraft landing on asteroid 1998 KY26. (Image: ESO/M. Kornmesser. Asteroid: T. Santana-Ros et al. Hayabusa2 model: SuperTKG/CC-BY-SA).

Astronomers have discovered surprising details about asteroid 1998 KY26. Observatories worldwide, including ESO’s Very Large Telescope, studied the asteroid carefully. The findings will help Japan’s Hayabusa2 mission prepare for its 2031 encounter.

How Small and Fast Is 1998 KY26?
New observations reveal the asteroid is only 11 metres wide. That is almost three times smaller than previously estimated. It rotates extremely fast, completing one spin in just five minutes. Earlier measurements suggested a rotation period of roughly ten minutes.

“This asteroid is very different from previous descriptions of it,” says Toni Santana-Ros, University of Alicante astronomer. He led the study, published in Nature Communications today.

What Challenges Will Hayabusa2 Face?
Hayabusa2 visited the 900-metre asteroid Ryugu in 2018, returning samples to Earth in 2020. The spacecraft is now on an extended mission until 2031. Touching down on 1998 KY26 will be difficult because of its small size and fast rotation.

“The smaller size and faster spin will make landing more challenging,” says Olivier Hainaut of ESO, co-author of the study. The spacecraft and asteroid are now comparable in size.

What Did Observations Reveal About the Asteroid?
1998 KY26 has a bright surface and appears solid, made of rock. It may have originated from a planet or larger asteroid. However, researchers cannot rule out the possibility of a rubble-pile structure. Studying such a small object required a close approach to Earth and large telescopes in Chile’s Atacama Desert.

“We have never seen a ten-metre asteroid in situ before,” says Santana-Ros. “We can now characterise tiny objects for future missions or asteroid mining.” The methods could also help track hazardous asteroids that might hit Earth.

Why Is This Discovery Important?
The asteroid is similar in size to the spacecraft visiting it. Scientists hope the study will improve knowledge of near-Earth asteroids. Even very small asteroids, like the one near Chelyabinsk in 2013, can cause significant damage. Understanding these objects is crucial for planetary defence and future exploration.

“The amazing part is we characterised such a tiny object from Earth,” adds Santana-Ros. “This will guide the Hayabusa2 mission and future asteroid research.”