Is a close approach the same as a near miss?

No. A close approach is a scheduled flyby whose trajectory is already known. A near miss implies something almost went wrong; a close approach implies orbital mechanics working exactly as predicted.

NASA lists all approaches within a few lunar distances. Any pass inside about 0.05 AU (~19.5 LD) for a large enough object is significant enough to update the potentially hazardous list.

Do close approaches happen often?

Yes. Small asteroids pass within a lunar distance multiple times a year, and most are only detected days before or even after they pass.

What Does an Asteroid "Close Approach" Mean?

5 min read

A "close approach" is a predicted flyby with a known trajectory — not an emergency and not a near miss.

The phrase close approach shows up in a lot of asteroid headlines, and it's routinely misread as close call. The two are very different. A close approach is a specific, well-defined astronomical event: it's the moment an asteroid or comet reaches the minimum distance between its orbit and Earth's on a given pass.

How NASA defines it

NASA's Center for Near-Earth Object Studies (CNEOS) publishes a rolling table of close approaches — every predicted encounter within a few tens of lunar distances of Earth (and, for context, of other planets and the Moon). For each pass, the table lists:

the object's name and provisional designation,
the calendar date and time of closest approach,
the nominal miss distance in AU, LD, and kilometers,
relative velocity in km/s,
an uncertainty range on the miss distance.

The data comes from the object's orbit solution, refined every time it's observed. For a well-tracked asteroid, the predicted miss distance is essentially exact — good to within a few hundred kilometers at a pass that's millions of kilometers away.

Why "close" doesn't mean "dangerous"

Space is enormous. Even the closest headline-worthy passes usually happen at fractions of a lunar distance — hundreds of thousands of kilometers. Objects that pass inside one LD are notable, but "notable" and "risky" aren't the same thing. Every close approach in the CNEOS table is one that isn't an impact.

When a close approach becomes news

A few things push a close approach up the news cycle:

Size. A pass by a football-field-sized rock draws more attention than a car-sized one, even at the same distance.
Distance. A pass inside 1 LD is uncommon enough for larger objects to be a story.
Discovery timing. When an object is only found days before or after its closest approach — as happens routinely for small ones — that's usually what makes the headline.
Hazard status. If the object is on the PHA list, coverage tends to lean harder on the word "hazardous," even when the actual miss is huge.

How Orbitfall shows close approaches

The Orbitfall tracker lists every close approach NASA's NeoWs feed reports for the range you pick, sorted by default with the most notable pass at the top. Each row shows the miss distance in LD and kilometers, the relative velocity, and an estimated diameter range.

See how the Orbitfall Index works for exactly how "notable" is calculated — and why it's a ranking of interest, not a probability of impact.

Frequently asked questions

Is a close approach the same as a near miss?: No. A close approach is a scheduled flyby whose trajectory is already known. A near miss implies something almost went wrong; a close approach implies orbital mechanics working exactly as predicted.
How close is close?: NASA lists all approaches within a few lunar distances. Any pass inside about 0.05 AU (~19.5 LD) for a large enough object is significant enough to update the potentially hazardous list.
Do close approaches happen often?: Yes. Small asteroids pass within a lunar distance multiple times a year, and most are only detected days before or even after they pass.