Solar system · Earth and Moon

Earth's Quasi-Moons

Asteroids that share Earth's orbit around the Sun and seem to circle us, some for centuries, and the mini-moons Earth captures for a few months at a time.

Earth's orbit To the Sun, 1 AU Kamoʻoalewa: a loop about 0.21 AU long Kamoʻoalewa 2025 PN7: a loop about 0.21 AU long 2025 PN7 Cardea: a loop about 0.27 AU long Cardea 2023 FW13: a loop about 0.35 AU long 2023 FW13 2006 FV35: a loop about 0.76 AU long 2006 FV35 2013 LX28: a loop about 0.90 AU long 2013 LX28 2014 OL339: a loop about 0.92 AU long 2014 OL339 Earth At this scale the Moon's orbit is a dot a few pixels across
Seen from above in a frame that turns with Earth around the Sun, each quasi-moon traces a loop around Earth once a year, moving backward. The more stretched its orbit, the bigger the loop. Loops are drawn from each orbit's eccentricity and simplified: they also drift slowly back and forth along Earth's orbit, and the widest are clipped at the edges.
Quasi-moons
7known
Most stable
Kamoʻoalewaabout 380 years
Newest
2025 PN7found Aug 2025
Mini-moon now
2026 QQ8until about Jan 2027
Sample return
Nov 2027Tianwen-2

Seven asteroids are Earth's quasi-moons: they orbit the Sun but stay near Earth for decades to centuries

A quasi-moon, or quasi-satellite, orbits the Sun in a year, just as Earth does, but on a slightly more stretched or tilted orbit. Seen from Earth it seems to loop around us once a year, moving backward, yet Earth's gravity does not hold it; it would follow almost the same path if Earth were not there. The arrangement lasts decades to thousands of years before the asteroid drifts away. Seven are generally listed; some lists add 2022 YG. Sizes are estimated from brightness, and orbital values are approximate.

Quasi-moonSize, mEccentricityTiltQuasi-moon forNote
Kamoʻoalewa40 to 1000.107.8°about 1910 to 2290The most stable; possibly a fragment of the Moon. China's Tianwen-2 has flown alongside it since July 2026.
2025 PN719 to 300.112°about 1965 to 2083The newest and smallest, found by Pan-STARRS in August 2025.
Cardea160 to 3600.1413.7°a few centuriesFormally 164207 (2004 GU9).
2023 FW1310 to 200.1814.8°about 100 BCE to 3700 CEFound by Pan-STARRS in March 2023; one of the longest-lived.
2006 FV35140 to 3200.387.1°a few thousand yearsFormally 277810; its stretched orbit swings it far from Earth.
2013 LX28130 to 3000.4549.9°about 1,000 yearsTilted about 50° to Earth's orbit.
2014 OL339150 to 3400.4610.2°a few hundred yearsStrays more than 1 AU from Earth on its widest loops.

Kamoʻoalewa may be a piece of the Moon, and China's Tianwen-2 is bringing a sample home

Found by Pan-STARRS in Hawaii in 2016 and named from a Hawaiian chant, Kamoʻoalewa stays 38 to 100 times the Moon's distance from Earth. In 2021 its reddish spectrum turned out to match space-weathered lunar rock, and a 2024 study traced it to the impact that made the Giordano Bruno crater on the Moon's far side 1 to 10 million years ago; other researchers dispute the link. China's Tianwen-2 launched on May 29, 2025, reached it in early July 2026 and is mapping it before collecting a sample. It leaves in April 2027, drops its capsule in the Gobi Desert in November 2027, then heads for the comet 311P/PANSTARRS, arriving around 2035.

Mini-moons are truly captured by Earth, but only for weeks to months

A mini-moon is a small asteroid that Earth's gravity actually captures for a while, usually one of the Arjunas, asteroids on orbits almost the same as Earth's. Most are a meter or two across and stay a few months; models suggest Earth usually has at least one. Only five have been seen:

Mini-moonCapturedSizeNote
2006 RH120September 2006 to June 2007a few metersThe first mini-moon found, by the Catalina Sky Survey; it looped around Earth about four times.
2020 CD3about 2018 to April 20201 to 6 mFound by Catalina in February 2020, weeks before it escaped.
2022 NX11981, and again in 20225 to 15 mCaptured twice, briefly each time.
2024 PT5September 29 to November 25, 2024about 10 mIts spectrum matches lunar rock, so it may be a chip of the Moon.
2026 QQ8April 2026 to about January 20271 to 2 mFound by Krisztián Sárneczky in Hungary in August 2026 and confirmed as natural in October; it next passes close in 2058.

Trojans and horseshoe orbits are other ways to share Earth's orbit

  • Earth trojans lead or trail Earth by 60°, near the L4 or L5 points: 2010 TK7, found by NASA's WISE in 2010, and 2020 XL5, about 1 km across.
  • Horseshoe orbits: 3753 Cruithne, sometimes called Earth's second moon, creeps up on Earth along its orbit, turns back and repeats over centuries. It never loops around Earth, so it is not a moon.
  • Kordylewski clouds, faint clouds of dust at the Earth-Moon L4 and L5 points, were reported in 1961 and again by Hungarian astronomers in 2018; they remain unconfirmed.

The Rubin Observatory should find many more, and they are the easiest asteroids to reach

Quasi-moons and mini-moons are small and faint, and many sit near the Sun in the sky, so few are known. The Vera C. Rubin Observatory and NASA's NEO Surveyor should find many more. Because their orbits are so like Earth's, they take less energy to reach than the Moon's surface, which makes them targets for sample-return missions and for testing asteroid mining. Near-Earth objects · Asteroids · Moons of the planets