Apophis is often called a "near-Earth asteroid," but the phrase is a technical category, not a warning label. Being a near-Earth object says something about an orbit, not about danger. Here is what the term means, how these objects are sorted, and how much of the population we have actually found.
A near-Earth object, or NEO, is an asteroid or comet whose orbit brings it relatively close to the Sun and therefore into Earth's neighborhood. NASA's usual cutoff is a closest approach to the Sun (perihelion) of less than about 1.3 astronomical units. One astronomical unit is the average distance between Earth and the Sun, so 1.3 AU is roughly 30 percent farther out than Earth's orbit.
Most NEOs are asteroids, called near-Earth asteroids or NEAs. Only a small share, on the order of a hundred, are comets. If you are unsure how these words differ, see our guide to asteroids, comets, meteors and meteorites.
Astronomers split NEAs into groups named after a typical member:
Apophis belongs to the Aten group. Its orbit lasts a little under a year, which is part of why it keeps returning to Earth's vicinity.
You may also see the label "potentially hazardous asteroid," or PHA. It has a precise meaning: an asteroid that can come within about 0.05 AU (roughly 7.5 million km) of Earth's orbit and is larger than about 140 meters. It is a screening category used to decide what deserves close monitoring. It does not mean the object will hit us. Many PHAs have orbits that are well known for the next century and show no impact.
The count grows every month. According to NASA's Center for Near-Earth Object Studies (CNEOS), the number of known near-Earth asteroids passed 35,000 in 2024 and, by 2025, the total of known NEOs was above 40,000. Check the live tally on the CNEOS website, because new discoveries are added continuously.
Size matters when reading these numbers:
Surveys supported by NASA have found most of the known objects, with telescopes in Arizona, Hawaii and elsewhere doing the bulk of the work.
For the largest objects, the job is largely done. In 1998 the U.S. Congress asked NASA to find 90 percent of NEOs larger than 1 kilometer, and NASA reported that goal met around 2010. Objects of that size could cause global effects, and we now know where almost all of them are.
The 140-meter class is a different story. NASA has said that estimates put the full population of such objects at roughly 25,000, and that only around 40 percent had been found when that figure was published. The share has risen since, but it is not complete. Closing the gap is the goal of surveys such as NASA's NEO Surveyor space telescope, planned to search from space for objects hard to see from the ground.
Discovery is the first step of planetary defense. An object that has been found can be tracked, its orbit refined and its future checked for decades ahead. An object that has not been found cannot. That is why Apophis, found in 2004 and now tracked with great precision, is considered a well-understood case, as we explain in Is Apophis dangerous?
For what happens after something is found, read how humanity learned to move an asteroid.
"Near-Earth object" is a map label for orbits that wander close to ours. Tens of thousands are cataloged, almost all the kilometer-sized ones are accounted for, and the search for the mid-sized remainder continues. Each new discovery adds to the list; it does not add to the risk.