The planet

JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is one of the four gas giants, primarily composed of hydrogen, with its mass slightly less than one-thousandth that of the Sun but two and a half times more massive than all of the other planets in our Solar System combined. And because it’s so big Jupiter is on average the third-brightest object in the night sky after the Moon and Venus.

The planet is famous for its Great Red Spot that existed at least since the 17th century when it was first seen by telescope, which is a giant storm caused by counter-rotating cloud bands with wind speeds of 360 km/h. The Red Spot is large enough to contain two or three planets of Earth's diameter. 

Mercury is the fasted around the sun but Jupiter is the fasted around its axis, completing a rotation in slightly less than ten hours, which creates a slight equatorial bulge that is easily seen through a telescope. Mercury is also the closest to the sun while Jupiter is the closest to being a sun itself, which is why astronomers term it a "failed star".

Jupiter may have failed to be a star, it has however its own “solar-system” of about 63 moons, including the four large moons called the Galilean moons that were first discovered by Galileo Galilee in 1610. Ganymede, the largest of these moons, has a diameter greater than that of the planet Mercury.

Because of Jupiter’s essential make-up being similar to the sun it still radiates more heat than it receives from the Sun. This “burning” results in the planet shrinking by about 2 cm each year. When it was first formed, Jupiter was much hotter and was about twice its current diameter.  

But it is still big enough to be called the Solar System's vacuum cleaner, because of its immense gravity and location near the inner Solar System. It receives the most frequent comet impacts of the Solar System's planets.

Flashes of lightning were detected in the atmosphere of Jupiter. These electrical discharges can be up to a thousand times as powerful as lightning on the Earth; very appropriate for the mythological chief, god of rain and thunder.

click here to continue on page 2

further articles from Sieghart:

Imagine you know nothing

A view from beyond the stars

My astrological overview

The astrological language

Responsibility, the ability to will

1968-2008

The hymn of love

The creation of humanity