New ESO observations reveal that asteroid 1998 KY26, Hayabusa2's 2031 target, is three times smaller than previously estimated and rotates on its axis in just five minutes – making the landing mission even more challenging
New observations using telescopes around the world, including the European Southern Observatory's (ESO) Very Large Telescope (VLT), reveal that asteroid 1998 KY26 – the target of the Japanese Hayabusa2 spacecraft's extended mission in 2031 – is almost three times smaller than previously estimated and is rotating twice as fast.
The asteroid, considered the final target of Hayabusa2, was discovered to be a body with a diameter of only 11 meters, compared to previous estimates of about 30 meters. Furthermore, it completes a full rotation on its axis in just five minutes – not ten minutes as previously thought. “The reality of the object is completely different from what we have previously described,” said Dr. Tony Santana-Ross of the University of Alicante in Spain, who led the study published inNature Communications..
Professor Olivier Hayno from ESO added that the new findings will make Hayabusa2’s visit even more fascinating – but also particularly challenging. “The landing maneuver, where the spacecraft ‘kiss’ the asteroid’s surface, will be more difficult to perform,” he noted.
Hayabusa2, launched in 2014 by the Japanese space agency JAXA, previously explored the 900-meter-diameter asteroid Ryugu, from which it returned samples to Earth in 2020. With fuel remaining, it was sent on an extended mission to 2031 to explore tiny asteroids – and this will be the first time a spacecraft has encountered such a small asteroid.
The team used large telescopes to characterize 1998 KY26, which is so small that it is very faint in observations. The results show that its surface is bright, and it is likely a solid block of rock – possibly broken off from another planet or asteroid. However, it cannot be ruled out that it is composed of a loose pile of rocks.
"The amazing thing about this is that the asteroid is almost the same size as the spacecraft that will visit it," Santana-Ross said. "We were able to characterize such a small object using our telescopes, which suggests that we can do this for other objects in the future. These methods could have implications for near-Earth asteroid exploration programs and even for mining resources from space."
According to Heino, the new ability to characterize extremely small asteroids may also improve preparedness for future hazards – such as a meteorite with a diameter of only a few dozen meters, such as the one that exploded over Chelyabinsk, Russia, in 2013.
