Deep Field

Starting

Deep Field
29 September 2026 2518 stories tracked

Glossary · Comets & Asteroids

Near-Earth object

An asteroid or comet whose orbit brings it inside 1.3 astronomical units of the Sun.

There are more than 35,000 known near-Earth asteroids and the count rises weekly as surveys improve. Almost all are small; the ones large enough to end a civilisation are essentially all found and none of them is on a collision course this century. The population that matters now is the 100-to-300 metre range, big enough to destroy a city and small enough to still be mostly undiscovered — which is what NEO Surveyor was built to fix.

Related terms

Asteroid and comet Rock that stays rock, and ice that grows a tail when it gets warm. Coma and tail A comet's atmosphere, and the two separate tails the Sun pushes off it. Oort cloud A shell of icy bodies at the edge of the Sun's influence, inferred rather than observed. Kuiper belt The flat ring of icy bodies beyond Neptune, where Pluto lives and short-period comets come from.

Questions

What is Near-Earth object?

An asteroid or comet whose orbit brings it inside 1.3 astronomical units of the Sun.

Why does it matter?

Almost all are small; the ones large enough to end a civilisation are essentially all found and none of them is on a collision course this century. The population that matters now is the 100-to-300 metre range, big enough to destroy a city and small enough to still be mostly undiscovered — which is what NEO Surveyor was built to fix.

Written and computed by . Corrections and errors to hello@cantinalabs.dev.