1998 KY26

Orbit and classification

orbits the Sun at a distance of 1.0–1.5 AU once every 16 months (500 days). Its orbit has an eccentricity of 0.20 and an inclination of 1° with respect to the ecliptic. It has an Earth minimum orbital intersection distance of approximately 0.0025 AU, corresponding to 0.98 lunar distances.

As a result, it is one of the most easily accessible objects in the Solar System, and its orbit frequently brings it on a path very similar to the optimum Earth–Mars transfer orbit. This, coupled with its high water content, makes it an attractive target for further study and a potential source of water for future missions to Mars.

In 2023, was identified as a possible dark comet. Dark comets are asteroids that exhibit comet-like acceleration, but visually appear as asteroids, with no coma or tail. Astronomers who study them believe the acceleration is caused by outgassing on the sunlit side.

Physical properties

The physical properties of this object were measured by an international team of astronomers led by Dr. Steven J. Ostro of the Jet Propulsion Laboratory using a radar telescope in California and optical telescopes in the Czech Republic, Hawaii, Arizona and California.

is characterized as a potentially metallic X-type asteroid. Optical and radar observations indicate that it is a water-rich object.

From light curve photometry in 1998, the object is measured to have a rotation period of only 10.7 minutes, which was considered to be one of the shortest sidereal days of any known Solar System object at the time; most asteroids with established rotational rates have periods measured in hours. As a result, it cannot possibly be a rubble pile, as many asteroids are thought to be, and must instead be a monolithic object. It was the first such object to be discovered, but since 1998, several other small asteroids have been found to also have short rotation periods, some even faster than . Being a rotating body in space, it is subject to the Yarkovsky effect. Observations of the asteroid during a close approach to Earth in 2024 revealed a smaller diameter of 11 meters, a shorter rotation period of 5.35 minutes, and a brighter albedo of 0.52.

Exploration

In September 2020, a mission extension for JAXA's Hayabusa2 asteroid sample return probe was selected to do additional flybys of two near-Earth asteroids: 98943 Torifune in July 2026 and a rendezvous with in July 2031. The rendezvous with will be the first visit of a rapidly rotating micro-asteroid. This will also make the smallest object to ever be studied by a spacecraft. Observations of the asteroid in 2024 cast doubt on if a landing on the asteroid is even possible.

References

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References

1. (18 September 2025). "Hayabusa2 extended mission target asteroid 1998 KY26 is smaller and rotating faster than previously known". Nature.
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3. Seligman, Darryl Z.. (2023-02-15). "Dark Comets? Unexpectedly Large Nongravitational Accelerations on a Sample of Small Asteroids". The Planetary Science Journal.
4. (2025-05-01). "Dark Comets". Scientific American.
5. "1998 Ky26".