OrbitalHub

Wikipedia dixit:

“Near-Earth asteroids are objects in a near-Earth orbit without the tail or coma of a comet. NEAs survive in their orbits for just a few million years. They are eventually eliminated by planetary perturbations, causing ejection from the Solar System or a collision with the Sun or a planet. With orbital lifetimes short compared to the age of the Solar System, new asteroids must be constantly moved into near-Earth orbits to explain the observed asteroids. The accepted origin of these asteroids is that main-belt asteroids are moved into the inner Solar System through orbital resonances with Jupiter. The interaction with Jupiter through the resonance perturbs the asteroid’s orbit and it comes into the inner Solar System. The asteroid belt has gaps, known as Kirkwood gaps, where these resonances occur as the asteroids in these resonances have been moved onto other orbits. New asteroids migrate into these resonances, due to the Yarkovsky effect that provides a continuing supply of near-Earth asteroids. Compared to the entire mass of the asteroid belt, the mass loss necessary to sustain the NEA population is relatively small; totalling less than 6% over the past 3.5 billion years. The composition of near-Earth asteroids is comparable to that of asteroids from the asteroid belt, reflecting a variety of asteroid spectral types.

A small number of NEAs are extinct comets that have lost their volatile surface materials, although having a faint or intermittent comet-like tail does not necessarily result in a classification as a near-Earth comet, making the boundaries somewhat fuzzy. The rest of the near-Earth asteroids are driven out of the asteroid belt by gravitational interactions with Jupiter.

Many asteroids have natural satellites (minor-planet moons). As of March 15, 2017, 66 NEAs were known to have at least one moon, including three known to have two moons. The asteroid 3122 Florence, one of the largest PHAs with a diameter of 4.5 km (2.8 mi), has two moons measuring 100–300 m (330–980 ft) across, which were discovered by radar imaging during the asteroid’s 2017 approach to Earth.”

Credits Video: ESA