43212 Katosawao

43212 Katosawao (provisional designation 2000 AL₁₁₃) is a Jupiter Trojan asteroid discovered on 5 January 2000 at Socorro by the LINEAR survey.^{1 • 7} With a semi-major axis of 5.2890 au, eccentricity of 0.0593, inclination of 6.4748°, and an orbital period of 12.164 years, it is estimated to be about 19 km in diameter with an absolute magnitude of 12.38.^{3 • 7 • 3} It is a member of the Eurybates collisional family, the only major one known among the Jupiter Trojans.⁵ The asteroid is named for Sawao Katō, the Japanese gymnast who won eight Olympic gold medals, with the name announced in WGSBN Bulletin Volume 1, #1, dated 14 May 2021.^{1 • 2}

Discovery and orbit

Its orbit was secured well enough for the object to receive the permanent number 43212 and, later, a name².

The orbit places it firmly among the Jupiter Trojans, asteroids trapped near Jupiter's L4 or L5 Lagrange points, a class defined by a semi-major axis between 4.6 and 5.5 au and an eccentricity below 0.3⁴. At the epoch of 21 November 2025, the orbital solution gives a semi-major axis of 5.2890 au, an eccentricity of 0.0593, and an inclination of 6.4748° to the ecliptic; perihelion lies at 4.976 au and aphelion at 5.603 au, and one revolution takes 12.164 years (4,442.9 days)³. The Jupiter Tisserand parameter, a quantity that measures how strongly an orbit is controlled by Jupiter, is 3.0³.

The solution rests on 1,289 observations collected over 27 oppositions between 1977 and 2026, a long observational arc that constrains the orbit tightly³. The absolute magnitude of 12.38, together with the 19 km diameter estimate, describes a mid-sized Trojan body³.

The Eurybates family

Hubble Space Telescope observations of Eurybates and its satellite Queta showed that Eurybates is the parent body of the only major collisional family among the Jupiter Trojans, and its low density of 1.1 ± 0.3 g/cm³ suggests it is a typical member of the Trojan population⁵. Family membership links Katosawao to a single ancient disruption event rather than to an unrelated background object that happens to share Jupiter's orbit.

Name and the Trojan naming tradition

The name was announced by the International Astronomical Union's Working Group Small Bodies Nomenclature in the first issue of its new bulletin, WGSBN Bulletin Volume 1, #1, dated 14 May 2021, which lists (43212) Katosawao = 2000 AL₁₁₃².

The honoree is Sawao Katō (加藤沢男), the Japanese gymnast who, as the new captain of Japan's male gymnastics team at the 1968 Olympics, brought Japan its third consecutive team gymnastics victory and also won the all-around title; he kept the all-around title in 1972, becoming the third gymnast in history to do so, and his final Olympic competition was in 1976. Across the three Games he won eight gold medals, a total that remains an unbroken record for Olympic male gymnasts, and he was inducted into the International Gymnastics Hall of Fame in 2001¹.

The name departs from the tradition that governs most Trojan names. Jupiter's L4 asteroids are conventionally named after Greek characters and L5 asteroids after Trojan characters from the Iliad, so the two swarms are called the Greek camp and the Trojan camp⁶. Katosawao sits in the Greek camp but carries the name of a modern athlete; it belongs to a group of asteroids honoring Olympic athletes, announced alongside seven larger Trojans that were named under the traditional Greek-mythology convention¹.

References

1. Modern Heroes Find a Home in the Trojan Asteroids, Lucy Mission, Southwest Research Institute
2. WGSBN Bulletin, Volume 1, #1 (14 May 2021), IAU Working Group Small Bodies Nomenclature
3. Planety: Planetka (43212) Katosawao, orbital elements and derived data
4. SBDB Filter Parameters, JPL Small-Body Database
5. The orbit and density of the Jupiter Trojan satellite system Eurybates-Queta, arXiv:2106.02079
6. How Were the Trojan Asteroids Discovered and Named?, NASA
7. (43212) Katosawao – asteroid discovered 2000 | AsteroidName

Initially written Oct 21, 2026 · Edited: Oct 25, 2026

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