(4179) Toutatis
(4179) Toutatis is a near-Earth asteroid about 4.6 km long whose orbit crosses Earth's. China's Chang'e 2 flew past it on 13 December 2012 at 10.73 km/s, 770 m from its surface, and photographed it as it moved away.
Key facts
Science
Physical
- Mean radius
- 1.22 km
Orbital
- Semi-major axis
- 2.54 AU
- From catalogued orbital elements (MPC)
- Eccentricity
- 0.6246
- From catalogued orbital elements (MPC)
- Inclination
- 0.45 °
- From catalogued orbital elements (MPC)
- Orbital period
- 4.06 years
- From catalogued orbital elements (MPC)
- Perihelion
- 0.955 AU
- Computed from the orbital elements
- Aphelion
- 4.13 AU
- Computed from the orbital elements
- Mean orbital velocity
- 18.7 km/s
- Computed from the orbital elements
Discovery
- Discovered
- January 4, 1989
- Discoverer
- Christian Pollas (Caussols)
Composition
- Make-up
- A stony asteroid (Sk in Bus's taxonomy, JPL Small-Body Database). Radar images from Goldstone show that it does not spin about one axis: it rolls about its long axis every 5.41 days while that axis circles every 7.35 days on average, and its dimensions along its principal axes are 1.92, 2.40 and 4.60 km (Hudson and Ostro 1995). Chang'e 2's pictures, of the side that was lit, measure it at 4.75 × 1.95 km, give or take 10% (Huang et al. 2013). It is drawn with the radar shape, without turning. Its mass has not been measured.
Radiation & temperature
- Insolation
- 0.155 S⊕ · 15% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
- Geometric albedo
- 0.41
- Geometric albedo 0.41 ± 0.14, from NEOWISE's infrared measurements (Masiero et al. 2017) — an uncertain figure.
- Equilibrium temperature
- 153 K (-120 °C)
- Computed from albedo + distance from the Sun (airless black body); uses the geometric albedo as an estimate
Discovery & history
- Discovered
- January 4, 1989
- By
- Christian Pollas (Caussols)
- Name
- Named after Toutatis, the Gaulish god who protected the tribe, known from the Astérix books of Goscinny and Uderzo, whose villagers fear only that the sky may fall on their heads. The discoverer's citation added that, as the Apollo asteroid with the smallest inclination then known, it was a good candidate to fall on ours one day.
Christian Pollas found it on 4 January 1989 on plates taken at Caussols, in southern France, by A. Maury and J. D. Mulholland. Goldstone radar images from 1992 to 1996 gave its shape and showed that it tumbles (Hudson and Ostro 1995). On 13 December 2012 Chang'e 2 passed it at 10.73 km/s, 770 ± 120 m from its surface by the mission team's analysis, and photographed it as it moved away.
Photographed Toutatis at 10.73 km/s: 770 m from the surface by the team's measurement, 3.2 km in the first official figure.
Images
Images from open archives · credit shown per image