on a Planet for complete information & more pictures
solar system consists of a star we call the Sun, the
It also includes the Small
Bodies or Satellites
of the planets, comets, asteroids, and meteoroids. The Sun
is the source of electromagnetic energy (mostly in the
form of heat and light) in the solar system. The
solar system, together with stars visible on a clear
night, orbits the center of our galaxy, a spiral disk of
200 billion stars we call the Milky Way.
The planets revolve around the Sun in
the same direction, in nearly circular orbits. When
looking down from above the Sun's north pole, the planets
orbit in a counter-clockwise direction.
planets closest to the Sun - Mercury, Venus, Earth, and
Mars - are called the terrestrial planets because they
have solid rocky surfaces. The four large planets beyond
the orbit of Mars - Jupiter, Saturn, Uranus, and Neptune -
are called gas giants. Tiny, distant, Pluto has a solid
but icier surface than the terrestrial planets.
Nearly every planet - and some of the moons - has an
atmosphere. Earth's atmosphere is primarily nitrogen and
oxygen. Venus has a thick atmosphere of carbon dioxide,
with traces of poisonous gases such as sulfur dioxide.
Mars' carbon dioxide atmosphere is extremely thin.
Jupiter, Saturn, Uranus, and Neptune are primarily
hydrogen and helium. When Pluto is near the Sun, it has a
thin atmosphere, but when Pluto travels to the outer
regions of its orbit, the atmosphere freezes and
"collapses" to the planet's surface. In this
regard, Pluto acts like a comet.
are more than 100 natural satellites (also called moons)
around the various planets in our solar system, ranging
from bodies larger than our own Moon to small pieces of
debris. Many of these were discovered by planetary
spacecraft. Some of these have atmospheres (Saturn's
Titan); some even have magnetic fields. Jupiter's moon Io
is the most volcanically active body in the solar system.
An ocean may lie beneath the frozen crust of Jupiter's
moon Europa. Some planetary moons may actually be
asteroids that were captured by a planet's gravity.
the planets also have magnetic fields which extend into
space and form a "magnetosphere" around each
planet. These magnetospheres rotate with the planet,
sweeping charged particles with them. The Sun has a
magnetic field, the heliosphere, which envelops our entire
are a few more facts on our solar system
are some related links