An image of Jupiter, captured by the Cassini space probe. Image courtesy http://nasa.gov

Past Mars and the asteroid belt is our solar system’s largest planet: Jupiter.  It has two and a half times the mass of all other planets in the solar system combined!  It can even be seen from Earth.  In fact, only the sun, moon and Venus are brighter. It was known by ancient astronomers and was involved in the religions and myths of many cultures.  It was named after the Roman god of sky and thunder.  He was also the king of the Roman gods.

Jupiter is the first of four gas giants.  It has a thick atmosphere.  Very little sunlight gets through its clouds.  Scientists believe there is an ocean made of liquid hydrogen which may be up to 10,000 miles deep.  The atmosphere is made of hydrogen and a little bit of helium.  Clouds move in swirling bands around Jupiter very fast, causing many great storms.

Jupiter has a large red spot which is a raging storm that has been going on for many years.  The discovery of the Great Red Spot is usually attributed to Giovanni Cassini due to a sketch in 1672.  That means this storm is over 330 years old!  Jupiter has many other spots which are also large storms, but none as big as the Great Red Spot.

Jupiter has at least 63 moons.  The four largest can be seen from Earth with a telescope.  These moons were very important in Galileo’s study of the solar system.  By watching their movement, he realized that the moons were going around Jupiter.  Although Nicolaus Copernicus had already suggested that the planets went around the sun rather than Earth, most people of Galileo’s day still believed the Earth was the center of the universe.  By noticing that the moons went around Jupiter, Galileo realized that not everything in the universe went around the Earth.