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1998 KY₂₆
	Three views of a computer model of 1998 KY26, derived from radar observations in 1998
Discovery
Discovered by	Spacewatch; (Tom Gehrels)
Discovery site	Kitt Peak Obs.
Discovery date	28 May 1998; (discovery: first observed only)
Designations
MPC designation	1998 KY26
Minor planet category	NEO · Apollo
Orbital characteristics
	Epoch 31 May 2020 (JD 2459000.5)
	Uncertainty parameter 0
Observation arc	22.54 yr (8,231 days)
Aphelion	1.4819 AU
Perihelion	0.9840 AU
Semi-major axis	1.2329 AU
Eccentricity	0.20192
Orbital period (sidereal)	1.37 yr (500.04 days)
Mean anomaly	359.504°
Mean motion	0° 43m 11.781s / day
Inclination	1.4810°
Longitude of ascending node	84.366°
Argument of perihelion	209.378°
Earth MOID	0.002531 AU (0.985 LD)
Physical characteristics
Mean diameter	30 m (effective diameter); 20–40 m (range)
Synodic rotation period	0.1782 h; 0.1784 h
Geometric albedo	0.12; 0.124 (derived)
Spectral type	X; B–R=0.083±0.070; V–R=0.058±0.055; R–I=0.088±0.053
Absolute magnitude (H)	25.5±0.3

1998 KY₂₆ is a nearly spherical sub-kilometer asteroid, classified as a near-Earth object of the Apollo group. It measures approximately 30 meters (100 feet) in diameter and is a fast rotator, having a rotational period of only 10.7 minutes. It was first observed on 2 June 1998, by the Spacewatch survey at Kitt Peak National Observatory during 6 days during which it passed 800,000 kilometers (half a million miles) away from Earth (a little more than twice the Earth–Moon distance).^[2]^[3]

The object's orbit is well known, since it was recovered in 2002 by the Hawaiian Observatory, and it was most recently observed, from 10 till 15 December 2020, by the Cerro Paranal. La Palma Observatory, and Mauna Kea observatories.^[8]

Orbit and classification

1998 KY₂₆ 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 (374,000 km; 232,000 mi), corresponding to 0.98 lunar distances.^[1]

As a result, it is one of the most easily accessible objects in the Solar System,^[9] and its orbit frequently brings it on a path very similar to the optimum Earth–Mars transfer orbit.^[1] 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.^[10]

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.

1998 KY₂₆ is characterized as a potentially metallic X-type asteroid.^[4] Optical and radar observations indicate that it is a water-rich object.^[10]

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.^[5] As a result, it cannot possibly be a rubble pile, as many asteroids are thought to be, and must instead be a monolithic object.^[6]^[5]^[7] 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 1998 KY₂₆.

Exploration

Animation of Hayabusa2 orbit - Extended mission
Hayabusa2 · 162173 Ryugu · Earth · Sun · 98943 Torifune · 1998 KY26

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 1998 KY₂₆ in July 2031. The rendezvous with 1998 KY₂₆ will be the first visit of a rapidly rotating micro-asteroid.^[11] This will also make 1998 KY26 the smallest object to ever be studied by a spacecraft.^[12]

References

^ ^a ^b ^c ^d ^e ^f ^g "JPL Small-Body Database Browser: (1998 KY26)" (2020-12-12 last obs.). Jet Propulsion Laboratory. Retrieved 1 August 2017.
^ ^a ^b "1998 KY26". Minor Planet Center. Retrieved 1 August 2017.
^ ^a ^b "Spacewatch discovery of 1998 KY₂₆". SPACEWATCH Project. 7 April 2004. Archived from the original on 1 July 2010. Retrieved 1 August 2017.
^ ^a ^b ^c ^d ^e "LCDB Data for (1998 KY26)". Asteroid Lightcurve Database (LCDB). Retrieved 1 August 2017.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Ostro, Steven J.; Pravec, Petr; Benner, Lance A. M.; Hudson, R. Scott; Sarounová, Lenka; Hicks, Michael D.; et al. (June 1999). "Radar and Optical Observations of Asteroid 1998 KY26" (PDF). Science. 285 (5427): 557–559(SciHomepage). Bibcode:1999Sci...285..557O. doi:10.1126/science.285.5427.557. PMID 10417379.
^ ^a ^b Hicks, M. D.; Weissman, P. R.; Rabinowitz, D. L.; Chamberlin, A. B.; Buratti, B. J.; Lee, C. O. (September 1998). "Close Encounters: Observations of the Earth-crossing Asteroids 1998 KY26 and 1998 ML14". American Astronomical Society. 30: 1029. Bibcode:1998DPS....30.1006H.
^ ^a ^b Pravec, P.; Sarounova, L. (June 1998). "1998 KY26". IAU Circ. 6941 (6941): 2. Bibcode:1998IAUC.6941....2P.
^ "MPEC 2020-X181 : 1998 KY26". Minor Planet Electronic Circular. Minor Planet Center. 15 December 2020. Retrieved 16 December 2020.
^ "1998 KY₂₆". Retrieved 25 April 2009.
^ ^a ^b "Astronomy Picture of the Day: Asteroid 1998 KY26". NASA. 19 September 2002. Retrieved 1 August 2017.
^ Gough, Evan (25 September 2020). "Hayabusa2's Mission isn't Over. It has a New Asteroid Target to Visit: 1998 KY26". Universe Today. Retrieved 1 October 2020.
^ "1998 Ky26".