Asteroid Close-Approach Tracker
Follow upcoming Earth approaches using NASA/JPL distance and relative-speed data.
How to use this tracker
One lunar distance (LD) is the average Earth–Moon distance. A close approach does not by itself mean an impact risk.
Astronomical “close” does not mean collision course. The live tool organizes NASA/JPL close-approach data so you can compare encounter date, nominal distance, speed and size context while keeping uncertainty and scale visible.
What a close approach means
Near-Earth objects follow orbits that bring them into Earth’s broader orbital neighborhood. From time to time, their predicted trajectories pass relatively near our planet. In astronomical work, “close” can still mean millions of kilometres.
The encounter distance shown in the tracker should therefore be read quantitatively, not emotionally. Converting to lunar distances gives a familiar scale and helps avoid misleading language.
Nominal distance and uncertainty
The nominal close-approach distance is the most likely value from the current orbital solution. Measurements are not perfect, so NASA/JPL can also publish uncertainty information around the predicted geometry. As new observations improve an orbit, the uncertainty can shrink and the predicted values can be refined.
A minimum possible close-approach distance derived from an uncertainty region is not automatically a predicted impact. It is one part of a statistical orbital solution.
Relative speed and estimated size
Relative encounter speed tells you how fast the object is moving with respect to Earth near closest approach. It is not the object’s total heliocentric orbital speed. Estimated asteroid size may come from brightness and assumed reflectivity when direct diameter measurements are unavailable, so a range is often more scientifically appropriate than a single exact number.
Close approach versus impact monitoring
NASA/JPL source
The authoritative source is NASA/JPL CNEOS. Its NEO Earth Close Approaches table defines nominal distance, minimum distance, uncertainty, relative velocity and diameter fields. TagBuilder Space reformats provider data for easier exploration without inventing missing measurements.
Frequently asked questions
Does a close approach mean the asteroid will hit Earth?
No. Many objects pass at several lunar distances or more with no predicted impact.
Why can the predicted distance change?
New astrometric observations can refine the orbital solution and reduce uncertainty.
What does LD mean?
LD means lunar distance, a convenient comparison with the average Earth–Moon separation.
Is an estimated diameter exact?
Not always. When diameter is inferred from brightness, assumptions about reflectivity can produce a size range.