Kamoʻoalewa
Key facts
- What it is
- Near-Earth asteroid and quasi-satellite of Earth
- Size
- Roughly 40–100 m across
- Discovered
- 2016, by the Pan-STARRS survey
- Spacecraft
- Tianwen-2 (arrived 2026)
- Orbit group
- Apollo
- Average distance from the Sun
- 1 au (about 150 million km)
- Time to go round the Sun
- 366 days
- Closest and farthest from the Sun
- 0.9 to 1.1 au
- Tilt of its orbit
- 7.8°
- Closest its orbit comes to Earth's
- 4,500,000 km (12 times the Moon's distance)
- Spins once every
- 28 minutes
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.
Kamoʻoalewa is a small asteroid that seems to keep Earth company. It orbits the Sun, not the Earth, but its orbit is so similar to ours that, seen from Earth, it appears to loop around our planet once a year. Objects like this are called quasi-satellites. Kamoʻoalewa has been in this kind of orbit for about a century and should stay in it for centuries more, never coming closer than about 40 times the distance to the Moon.
It was discovered on 27 April 2016 by the Pan-STARRS survey telescope on Haleakalā, on the island of Maui in Hawaiʻi. Its Hawaiian name comes from a traditional chant and refers to a moving, oscillating fragment of the heavens. It is small, probably somewhere between 40 and 100 metres across, and spins quickly, once about every 28 minutes.
What makes Kamoʻoalewa special is its colour. In 2021 astronomers reported that the light it reflects is reddish in a way that resembles lunar rocks more than typical asteroids. One idea is that it is a piece of the Moon itself, thrown off by a large impact, perhaps the one that made the young crater Giordano Bruno on the far side. Others think it could be an ordinary asteroid weathered in an unusual way. A sample would settle the question.
That is the goal of China's Tianwen-2 mission, launched in May 2025. It reached Kamoʻoalewa in 2026, is studying the asteroid and attempting to collect a sample, and is planned to return it to Earth before continuing to a comet in the main belt.
Coming close to Earth
Its next passes within about 30 million km of Earth, worked out from its orbit. Each one is a safe miss.
| Date | Distance | In Moon distances |
|---|---|---|
| 5 Nov 2026 | 17,000,000 km | 45 |
| 21 Feb 2027 | 26,000,000 km | 66 |
| 7 Nov 2027 | 17,000,000 km | 43 |
| 7 Nov 2028 | 16,000,000 km | 42 |
| 9 Nov 2029 | 16,000,000 km | 42 |
| 9 Nov 2030 | 16,000,000 km | 42 |