Near-Earth Asteroids: How Often Do They Pass Close?

Space is busier than it looks. In any given year, hundreds of asteroids pass close enough to Earth for astronomers to track them carefully, and dozens slip inside the Moon's orbit — closer to us than our own satellite. It sounds alarming, but almost all are small and harmless. This guide uses a live snapshot of NASA's close-approach data to show how often asteroids pass nearby, what "close" really means in space, and how seriously scientists take the risk.

How many asteroids pass near Earth?

NASA's Center for Near-Earth Object Studies tracks every known asteroid that comes within a set distance of Earth. The snapshot above contains more than a thousand close approaches over an roughly 18-month window — and that's only the ones we've found. The scatter plots each object by how close it passes and how big it is. The pattern is reassuring: the overwhelming majority are small, and the genuinely close passes are dominated by tiny objects that would burn up harmlessly if they ever entered the atmosphere.

What counts as a 'close' approach?

Astronomers measure these distances in lunar distances (LD) — multiples of the average Earth–Moon distance, about 239,000 miles. An asteroid passing at 1 LD comes as close as the Moon; many pass at dozens of LD, which is still "close" by cosmic standards but enormously far in human terms. A surprising number, though, do slip inside 1 LD — closer than the Moon. These are almost always small rocks just a few meters across, detected precisely because we now scan the sky so thoroughly.

Are we in danger?

Realistically, no — not from anything on these lists. The objects that pass closest are small enough to disintegrate in the atmosphere, producing at most a bright fireball. A genuinely dangerous asteroid would need to be hundreds of meters across, and NASA has already found and mapped the orbits of the vast majority of large near-Earth objects, none of which threatens Earth for the foreseeable future. The frequent close passes you see here are a sign of how good our detection has become, not of rising danger.

How we track and defend against asteroids

A global network of telescopes constantly scans for new objects, and their orbits are computed years or decades into the future. For the rare object that might someday pose a risk, humanity now has a tested defense: in 2022, NASA's DART mission deliberately crashed a spacecraft into a small asteroid and successfully altered its orbit — the first demonstration that we could nudge a threatening rock off course with enough warning. Early detection is the key, which is why surveys like the one behind this data matter.