Psyche
Key facts
- What it is
- Metal-rich main-belt asteroid
- Size
- About 220 km across (on average)
- Discovered
- 1852, by Annibale de Gasparis
- Spacecraft
- Psyche spacecraft, due to arrive in 2029
- Orbit group
- Main-belt Asteroid
- Average distance from the Sun
- 2.93 au (about 440 million km)
- Time to go round the Sun
- 5 years
- Closest and farthest from the Sun
- 2.53 to 3.32 au
- Tilt of its orbit
- 3.1°
- Spins once every
- 4.2 hours
An au (astronomical unit) is Earth's average distance from the Sun, about 150 million km. Orbit figures are from open tracking data, figures last updated 1 Nov 2026.
Psyche stands out among the large asteroids because it appears to be rich in metal. Radar echoes bounce back from it strongly, as they do from iron and nickel, and its surface reflects sunlight in a way typical of the metal-rich M-type asteroids. It is a somewhat flattened, potato-like body averaging about 220 kilometres across.
For a long time Psyche was thought to be the exposed metal core of a small world that had melted, separated into layers, and then had its rocky outer layers stripped away by collisions. If so, it would offer a unique look at the kind of core that lies, out of reach, at the centre of Earth. Iron meteorites are thought to come from cores like this, so Psyche could be a whole parent body of the kind that iron meteorites came from.
More recent estimates of its mass and size give a density lower than solid iron, which suggests Psyche is a mixture of metal and rock, or a metal body with a lot of empty space inside. Some scientists think it may be more like the stony-iron mesosiderites, or that iron may once have erupted onto its surface. The honest answer is that nobody knows yet.
That is why NASA launched the Psyche spacecraft in October 2023. Using electric propulsion and a gravity boost from Mars, it is due to arrive in 2029 and spend many months in orbit, mapping the surface, measuring its gravity and magnetic field, and finally showing what this unusual world is made of.