An asteroid is a rocky celestial body, smaller than a planet and
bigger than a meteoroid. Most of them orbit between Mars and Jupiter, in the region
of the solar system known as the asteroid belt; others accumulate in
Jupiter's Lagrange points, and most of the rest cross the orbits
of the planets.
The Earth (from the Latin Terra, Roman deity equivalent to Gaea, Greek goddess of
femininity and fertility) is a planet in the solar system that revolves around
of its star—the Sun—in the third innermost orbit. It is the densest and the
fifth largest of the eight planets in the solar system. He is also the oldest of
the four terrestrial or rocky.
The Sun (from Latin sol, solis, 'god Sol invictus' or 'sun', Helios in Greek mythology,
in turn from the Proto-Indo-European root sauel-, 'to shine') is a G-type star
of the main sequence and luminosity class V found in the
center of the solar system and constitutes the largest source of radiation
electromagnetic energy of this planetary system. It is an almost perfect sphere of
plasma, with an internal convective movement that generates a magnetic field
through a dynamo process. About three quarters of the mass of
Sol consist of hydrogen; the rest is mainly helium, with amounts
much smaller elements, including oxygen, carbon, neon and
iron.
The Moon is the only natural satellite of the Earth. With an equatorial diameter of 3476 km, it is
the fifth largest satellite in the solar system, while in terms of size
proportional to its planet is the largest satellite: a quarter of the diameter of the
Earth and 1/81 of its mass. It is also, after Io, the second densest satellite. HE
is in synchronous relationship with the Earth, always showing the same face towards the
planet. The visible hemisphere is marked with dark lunar seas of volcanic origin
between the brilliant ancient mountains and the outstanding astroblemes.