Jupiter The Planet
Largest Planet In The Solar System
Jupiter the planet is fifth from the Sun and the largest planet
in our solar system. Jupiter is so massive it's two and a half times
the mass of all the other planets in our Solar System combined.
A "Jupiter mass" (MJ or MJup) is often used as a unit to describe
masses of other objects, particularly extrasolar planets and brown dwarfs.
The first of the "outer" planets or gas giants, Jupiter is the fastest
spinning of all the planets. Jupiter's day is less than ten Earth hours long.
The year on Jupiter is almost 12 Earth years long. That's less than half the time it takes
Saturn the planet
to orbit the Sun.
Jupiter spins so fast that like Saturn, it creates an equatorial bulge
easily seen through an Earth-based amateur telescope.
Earth overtakes Jupiter every 398.9 days as it orbits the Sun,
a duration called the synodic period. As it does so, Jupiter appears
to undergo retrograde motion with respect to the background stars.
That means for a period Jupiter seems to move backward in the night sky,
performing a looping motion.
Viewing Jupiter the planet can be quite rewarding.
It is visible to the naked eye in the night sky and,
can occasionally be seen in the daytime when the sun is low.
When viewed from Earth, Jupiter can reach an apparent magnitude of -2.94,
making it on average the third-brightest object in the night sky
after the Moon and
Venus the planet.
Mars can briefly match Jupiter's brightness at certain points in its orbit.
Favorable oppositions occur when Jupiter is passing through perihelion,
an event that occurs once per orbit.
As Jupiter approaches perihelion in March 2011, there will be a
favorable opposition in September 2010.
Because the orbit of Jupiter is outside the Earth's, the planet always
appears nearly fully illuminated when viewed through Earth-based telescopes.
Surrounding the planet is a faint planetary ring system, though nothing as
majestic as Saturn's and a powerful magnetosphere.
Jupiter The Planet In Telescopes
Jupiter is thrilling to view in just about any telescope,
even a small department-store refractor
will reveal several cloud belts and its four brightest moons.
The four largest moons, known as the "Galilean moons",
are Io, Europa, Ganymede and Callisto.
These were first discovered by Galileo Galilei in 1610.
Ganymede, the largest of these moons, has a diameter greater
than that of
Mercury the planet.
Jupiter has 63 named natural satellites. Of these, 47 are less than
10 kilometres in diameter and have only been discovered since 1975.
Jupiter is also one of the most dynamic telescopic sights —
you never get the same view twice.
This is partly the result of its rapid rotation.
Although Jupiter is big and bright, it doesn't tolerate high
magnification well. Consequently, you will rarely use more than
40x per inch of aperture.
The four Galilean moons are easily visible with binoculars;
a few bands and the Great Red Spot can be seen with a
small astronomical telescope.
The Great Red Spot is a gigantic storm raging in the atmosphere
of Jupiter. The storm is so large that almost 3 Earths could fit
inside it. That's one huge hurricane.
There are many other storms raging in Jupiter's atmosphere.
Sometimes they even crash into each other and create larger storms.
Jupiter the planet to planets homepage
Constellations and backyard stargazing