162173 Ryugu
Color image of Ryugu taken by Hayabusa2, 2018 | |
| Discovery | |
|---|---|
| Discovered by | LINEAR |
| Discovery site | Lincoln Lab's ETS |
| Discovery date | 10 May 1999 |
| Designations | |
| (162173) Ryugu | |
| Pronunciation | /riˈuːɡuː/ Japanese: [ɾjɯːɡɯː] |
Named after | Ryūgū ("Dragon palace") |
| 1999 JU3 | |
| Apollo · NEO · PHA | |
| Orbital characteristics | |
| Epoch 12 December 2011 (JD 2455907.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 30.32 yr (11,075 d) |
| Aphelion | 1.4159 AU |
| Perihelion | 0.9633 AU |
| 1.1896 AU | |
| Eccentricity | 0.1902 |
| 1.30 yr (474 d) | |
| 3.9832° | |
| 0° 45m 34.56s / day | |
| Inclination | 5.8837° |
| 251.62° | |
| 211.43° | |
| Earth MOID | 0.0006 AU (0.2337 LD) |
| Physical characteristics | |
| Dimensions | 1004 m × 876 m |
| 448±2 m | |
Equatorial radius | 502±2 m |
Polar radius | 438±2 m |
| Volume | 0.377±0.005 km3 |
| Mass | (4.50±0.06)×1011 kg |
Mean density | 1.19±0.03 g cm−3 |
Equatorial surface gravity | 1/80,000 g |
| 7.63262±0.00002 h | |
| 171.64°±0.03° | |
North pole right ascension | +96.40°±0.03° |
North pole declination | −66.40°±0.03° |
| 0.037±0.002 0.042±0.003 0.047±0.003 0.063±0.020 0.07±0.01 0.078±0.013 | |
| SMASS = Cg · C · Cb | |
| 18.69±0.07 (R) 18.82 19.2 19.25±0.03 19.3 | |
162173 Ryugu (provisional designation 1999 JU3) is a near-Earth object and also a potentially hazardous asteroid of the Apollo group. It measures approximately 900 metres (3,000 ft) in diameter and is a dark object of the rare spectral type Cb, with qualities of both a C-type asteroid and a B-type asteroid. In June 2018, the Japanese spacecraft Hayabusa2 arrived at the asteroid. After making measurements and taking samples, Hayabusa2 left Ryugu for Earth in November 2019 and returned the sample capsule to Earth on 5 December 2020. The samples showed the presence of organic compounds, such as uracil (one of the four components in RNA) and vitamin B3.