2018 CN₂ is a very small asteroid, classified as a near-Earth object of the Apollo group, approximately 5 to 16 meters in diameter. It was first observed by astronomers of the Mount Lemmon Survey at Mount Lemmon Observatory, Arizona, on 8 February 2018, one day prior its close encounter with Earth at 0.18 lunar distances.^[1]

2018 CN₂ is a member of the Apollo asteroids, which cross the orbit of Earth. Apollo's are the largest group of near-Earth objects with nearly 10 thousand known objects.

Based on a high orbital uncertainty, this asteroid orbits the Sun at a distance of 0.63–1.77 AU once every 16 months (482 days; semi-major axis of 1.20 AU). Its orbit has an eccentricity of 0.47 and an inclination of 26° with respect to the ecliptic.^[2] With an aphelion of 1.77 AU, it is also a Mars-crosser, as it crosses the orbit of the Red Planet at 1.666 AU. The body's observation arc begins at Mount Lemmon with its first observation on 8 February 2018.^[1]

The object has an exceptionally low minimum orbital intersection distance with Earth of 11,500 km (0.000077 AU), or 0.03 lunar distances (LD).^[2]

On 9 February 2018, 2018 CN₂ passed at a nominal distance of only 69,900 km; 43,400 mi (0.000466964 AU) from Earth at 7:25 UTC.^[2] This corresponds to 0.18 LD. Based on the body's high orbital uncertainty, all subsequent close encounters in 2022, 2023, 2026, 2027 and 2031, are projected to occur at a distance of more than 15 million kilometers (0.1 AU; 39 LD).^[2]

2018 flyby: Its path across the sky on 9 February was north to south (15 minute positions shown) (left). Seen from space, it passes just outside geosynchronous orbit (right).

The Minor Planet Center estimates a diameter of 5–16 meters.^[3] Based on a generic magnitude-to-diameter conversion, 2018 CN₂ measures between 9 and 17 meters in diameter, for an absolute magnitude of 27.653, and an assumed albedo between 0.057 and 0.20, which represent typical values for carbonaceous and stony asteroids, respectively.^[4]

As of 2018, no rotational lightcurve of 2018 CN₂ has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.^[2]

This minor planet has neither been numbered nor named.^[1]

• List of asteroid close approaches to Earth in 2018

• MPEC MPEC 2018-C76 : 2018 CN2, Minor Planet Electronic Circular, 10 February 2018
• Asteroid 2018 CN2 close approach, International Asteroid Warning Network (IWAN)
• Asteroid 2018 CN2 flew past Earth at 0.18 LD, discovered one day before closest approach, The Watchers, 11 February 2018
• 2018 CN2 at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemerides · Observation prediction · Orbital info · MOID · Proper elements · Observational info · Close approaches · Physical info · Orbit animation
• 2018 CN2 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters