What are NEOs?

any small objects in the solar system orbit the Sun coming very near Earth. These objects are named NEOs (Near Earth objects).

In this animation, the solar system is represented (the orbits of planets Mercury, Venus, Earth, Mars and Jupiter are drawn in blue, going from the Sun outward). Laid upon these planetary orbits, is it possible to see, sequentially, the orbits of the asteroids brighter than magnitude 14, the orbits of the asteroids brighter than magnitude 15 and their positions at the date 01-01-2001.

Images courtesy of Giovanni Valsecchi


A first classification of NEOs
NEOs are made of minor bodies of the solar system, or in other words, comets and asteroids which come into the Earth neighborhood following different orbits. A first classification of NEOs can be made studying these orbits.

Observed characteristics of NEOs
Many physical characteristics can be defined and measured for NEOs, both for asteroids and comets (such as brightness, albedo, etc). Measuring these quantities means to answer to some very interesting questions on NEOs such as: how big are they, at what distance from us do they stand, how many NEOs are out there and what are they made of?

Why do we study NEOs?
Some of these objects could possibly collide with our planet, representing a hazard to life on earth. This reason is an impulse for the study of NEOs (click here to go directly to the impact section). Scientific interest in studying these objects is also due to their status of remnant debris from the solar system formation about 4.6 billion years ago. So, NEOs represent the best opportunity we have to investigate extraterrestrial bodies which can give us interesting information about the primitive Solar system and its formation.