162173 Ryugu
Asteroid· orbits the Sun
Ryugu is a dark, spinning-top-shaped near-Earth asteroid sampled by Japan's Hayabusa2 in 2019, which returned pristine grains to Earth in 2020.
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Key facts
Radius
0.448 km
Distance from Sun
1.19 AU
Orbital period
474.7 days
Eccentricity
0.1911
Rotation
7.63 hours
Science
Physical
- Mean radius
- 0.448 km
- Mass
- 4.49 × 10¹¹ kg · 0.00000000000612 Moon masses
- Density
- 1,193 kg/m³ · 1.2× water
- Computed from mass and radius
- Rotation period
- 7.63 hours
Orbital
- Semi-major axis
- 1.19 AU
- From catalogued orbital elements (MPC)
- Eccentricity
- 0.1911
- From catalogued orbital elements (MPC)
- Inclination
- 5.87 °
- From catalogued orbital elements (MPC)
- Orbital period
- 474.7 days
- From catalogued orbital elements (MPC)
- Perihelion
- 0.963 AU
- Computed from the orbital elements
- Aphelion
- 1.42 AU
- Computed from the orbital elements
- Mean orbital velocity
- 27.3 km/s
- Computed from the orbital elements
Discovery
- Discovered
- May 10, 1999
- Discoverer
- the LINEAR survey
Composition
- Make-up
- A C-type rubble pile rich in hydrated minerals and organics; the returned samples contain amino acids.
Radiation & temperature
- Insolation
- 0.705 S⊕ · 71% of the sunlight Earth receives
- Computed from the distance to the Sun (inverse-square; Earth's sunlight = 1), before any atmosphere.
- Geometric albedo
- 0.04
- Geometric albedo ≈ 0.045 — a very dark surface (Hayabusa2).
- Equilibrium temperature
- 252 K (-21 °C)
- Computed from albedo + distance from the Sun (airless black body); uses the geometric albedo as an estimate
Discovery & history
- Discovered
- May 10, 1999
- By
- the LINEAR survey
- Method
- Photographic plates
- Name
- Ryūgū-jō, the undersea Dragon Palace of Japanese folklore — a casket of treasure brought back from the deep.
Ryugu is a dark, carbon-rich near-Earth asteroid found in 1999 and shaped like a spinning top. Japan's Hayabusa2 orbited it in 2018–19, deployed rovers, fired an impactor to expose fresh subsurface material, and returned samples to Earth in 2020 that contain amino acids and water-bearing minerals from the early Solar System.
- 2018Hayabusa2Sample return
Surveyed Ryugu, fired an impactor to expose subsurface material, and returned samples in 2020.
Images
Images from open archives · credit shown per image