7641 Cteatus
7641 Cteatus (provisional designation 1986 TT) is a large Jupiter trojan asteroid from the Greek camp, approximately 70 kilometers (43 miles) in diameter. It was discovered on 5 October 1986 at the Piwnice observatory by M. Antal.1
| Key fact | Detail |
|---|---|
| Designation | Minor planet number 7641, provisional designation 1986 TT1 |
| Discovery | 5 October 1986, Piwnice, by M. Antal1 |
| Orbit | Semi-major axis 5.2090 au, eccentricity 0.0535, inclination 34.6999°, perihelion distance 4.930 au1 |
| Brightness | Absolute magnitude H = 9.46, phase parameter G = 0.151 |
Orbit and classification
Cteatus is a Jupiter trojan, one of the asteroids that share Jupiter's orbit, staying near one of the stable Lagrange points 60 degrees ahead of or behind the planet. It belongs to the Greek camp at Jupiter's L4 point, the camp conventionally populated with asteroids named after Greek characters of the Trojan War, while the L5 Trojan camp carries Trojan names.2
Its orbit is measured with a semi-major axis of 5.2090 au (779,258,330 km), an eccentricity of 0.0535, and an unusually high inclination of 34.6999° to the ecliptic. The perihelion distance is 4.930 au (737,531,000 km), and the mean daily motion is 0.0829°/day.1 The orbit is well determined: by 2026 the asteroid had been observed in 31 oppositions, with 5,270 observations spanning 1975 to 2026, the most recent dated 24 May 2026.1
Physical properties
Infrared surveys by the IRAS satellite, Japan's Akari satellite, and NASA's NEOWISE mission give a diameter of 68.97 to 75.28 kilometers and a surface albedo of 0.062 to 0.071.
Name
The asteroid is named after Cteatus, a figure from Greek mythology who was born a twin, joined with his brother Eurytus, and became the father of Amphimachus.3 The name follows the tradition, established after the first trojan asteroids were named Achilles, Patroclus, and Hektor, of drawing Jupiter trojan names from characters of the Trojan War.2
Observing circumstances
Cteatus is large enough to be a target for stellar occultation campaigns. A predicted occultation on 5 April 2026 placed the asteroid's shadow path across star TYC 7183−00021−1, with an expected chord duration of 3.4 seconds and a magnitude drop of 5.2.4
References
- Planetka Cteatus (7641), Planety, University of West Bohemia
- How Were the Trojan Asteroids Discovered and Named?, NASA
- Quand (12238) Actor et (7641) Ctéatos se manifestent, Therapyame
- Occultations by major and minor planets – 2026, Royal Observatory of Belgium
Topic: Encyclopedia › Places and geography › Extraterrestrial places › Small bodies of the Solar System › Jupiter Trojans and other dynamical groups › Greek-camp Jupiter Trojans › Argonauts and pre-war heroes
Initially written Oct 20, 2026 · Edited: Oct 25, 2026
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