is a main belt asteroid that undergoes recurrent comet-like activity near perihelion, and is now designated comet . This object was discovered on August 29, 2005 by the Near-Earth Asteroid Tracking program at Palomar Observatory. It orbits in the outer main asteroid belt with an orbital period of 5.36 years, a semi-major axis of , and an orbital eccentricity of 0.225, bringing it as close as to the Sun at perihelion. The orbital plane is inclined at an angle of 0.068° to the ecliptic.
On July 7, 2021, was found to be active by the Asteroid Terrestrial-impact Last Alert System survey. Archival imagery showed it had been active during a previous perihelion passage, dated July 22, 2016. This indicates the activity is due to the sublimation of icy volatiles, as is common with comets. At the time that activity was identified, the object displayed a long, dusty tail, much like a comet. Follow up observations found this tail extended more than along its orbital plane. By August 14, 2021, the coma around the nucleus was fading, while the brightness of the tail remained roughly constant.
This asteroid has a mean diameter of , with a low visual albedo of . Its colors are consistent with a taxonomic classification as a dark C-type carbonaceous asteroid, which is a class commonly found in the outer main belt. Dust particles ejected from the object had very low velocities of about . This suggests that the dust emission may have been assisted by rapid spin of the asteroid, which would lower the escape velocity.
The asteroid made perihelion passage on September 3, 2026. Comet-like activity was reported from June 10 onward, becoming the third time it has been observed making an active apparition.
References (JPL#28 Soln.date: 2025-Jul-01)
Further reading
External links
433P/(248370) 2005 QN173 at Seiichi Yoshida's website 433P at Gideon van Buitenen's website