Close approach is a distance calculation
A row in the asteroid tracker describes an object passing Earth on a listed date. The miss distance is the separation at closest approach. It is not the distance the asteroid will travel through the atmosphere, and a close-approach listing is not an impact prediction.
Compare distances using the same unit. One lunar distance is approximately 384,400 kilometres, based on the average Earth–Moon separation. In an illustrative example, a pass at five lunar distances is about 1.92 million kilometres away. This example is a unit conversion, not a live prediction for a particular asteroid.
Why the size comes as a range
Many asteroid diameters are estimated from brightness and assumptions about how reflective the surface is. A darker object needs a larger surface to reflect as much light as a brighter one. Until more measurements constrain the object, a size interval is more informative than a single precise-looking number.
Our tracker displays the supplied minimum and maximum diameter and may use their midpoint for a compact comparison. That midpoint is a display summary; it is not a separate measurement. Keep the range in mind when comparing an asteroid with a building or another familiar object.
Potentially hazardous does not mean about to hit
NASA’s potentially hazardous asteroid classification uses orbit geometry and an absolute-magnitude threshold: an Earth minimum orbit intersection distance of 0.05 astronomical units or less, and absolute magnitude H of 22 or less. This is a screening category for objects warranting attention, not a countdown to a collision.
The classification concerns an orbit’s proximity to Earth’s orbit. The miss distance in a particular approach concerns where the two objects will be at that encounter. Read those fields separately. Use CNEOS Sentry for impact-monitoring information rather than interpreting the coloured label on a close-approach card as a probability.
A useful order for checking a listing
First note the object designation and approach date. Next check the distance and its unit. Then read the diameter range and the hazard classification. If you need to investigate further, use the exact designation on the CNEOS close-approach table so you do not confuse similarly named objects.
Our list comes from NASA NeoWs and is limited to the requested date interval. A missing row or an unavailable feed cannot establish that no asteroid approaches exist. Orbital estimates can change as new observations arrive, so keep the observation context with any number you share.