Šteins
Key facts
- What it is
- Rare E-type main-belt asteroid
- Size
- About 5 km across
- Discovered
- 1969, by Nikolai Chernykh
- Spacecraft
- Rosetta fly-by, 2008
- Orbit group
- Main-belt Asteroid
- Average distance from the Sun
- 2.36 au (about 350 million km)
- Time to go round the Sun
- 3.6 years
- Closest and farthest from the Sun
- 2.02 to 2.71 au
- Tilt of its orbit
- 9.9°
- Spins once every
- 6 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.
Šteins is a small asteroid with an unusual make-up. It belongs to the rare E-type asteroids, which are very bright because their surfaces are rich in a pale, iron-poor mineral called enstatite. E-types are linked to the aubrites, a group of meteorites made mostly of enstatite, which formed in very oxygen-poor conditions.
The European Space Agency's Rosetta spacecraft flew past Šteins on 5 September 2008, on its long journey to the comet Churyumov–Gerasimenko, passing at a distance of about 800 kilometres. The images showed a body about 5 kilometres across with a shape often compared to a cut diamond or a gemstone.
A large crater, about 2 kilometres wide, sits at one end, enormous for a body this small. A chain of smaller pits runs across the surface, which may mark places where loose surface material drained into cracks underneath. Scientists think Šteins is probably a rubble pile, and that its diamond shape came from sunlight. The gentle push of absorbed and re-emitted heat, called the YORP effect, can slowly speed up the spin of a small asteroid, and loose material then shifts towards the equator, giving it a bulge.
Šteins was discovered in 1969 by the Soviet astronomer Nikolai Chernykh and named after Kārlis Šteins, a Latvian astronomer.
Because E-type asteroids are uncommon, Šteins was a valuable target. It gave a rare close look at the kind of body that may have produced the aubrite meteorites.