Atlas · Gonggong
The moon of Gonggong
Gonggong has one known moon, Xiangliu, noticed in 2016 in Hubble pictures taken years earlier. Its path is clearly stretched: at its nearest it is little more than half as far from Gonggong as at its furthest.
Gonggong and its moon
Gonggong and the orbit of its moon, to scale. The orbit’s direction in space is not known.
The edge of the drawing is 38,000 km from the centre of Gonggong.
How to read it
Nobody knows yet which way this orbit faces in space, so it is drawn flat on the page, as if seen from straight above. Its size and shape are right. Its direction is not shown. Gonggong is drawn to scale with the orbits. The moons are not: at this scale most would be far too small to see, so each is a dot.
- Solid dot. A spacecraft has mapped the whole surface.
- Half dot. A spacecraft has seen part of it.
- Ring. Never seen as more than a point of light.
- Pale line. Goes round the usual way, the way the planets go round the Sun: anticlockwise on these drawings.
- Broken line. For 1 moon we have no run of positions to fit an orbit to, so it has a line and no dot.
Nobody has measured its size. Touch a row to pick out its orbit.
The moon
1 moon
The Hubble pictures fit two mirror-image orbits equally well, tipped opposite ways. The size and shape drawn are those of the one that goes round the usual way; the other differs by about one part in a hundred.
| Moon | Orbit size | One orbit | Tilt | Width | Found | See it in 3D |
|---|---|---|---|---|---|---|
| Xiangliu. Seen only as a point of light.no positions to place it by yet | 24,000 km | 25.22 days | not known | not measured | 2016 |
Where this comes from
- Kiss et al. 2019, Icarus 334, 3 (heat measured by the Herschel telescope)
- NASA/JPL Small-Body Database
Orbit size is the average distance from the centre of Gonggong. Tilt is measured from the plane of the planets, and above 90° means the moon goes round backwards compared with the planets.