Jupiter is the fifth planet from the sun and also the largest in the solar system (11 times larger in diameter than Earth). Because of it's size Jupiter is the fourth brightest object in the sky following the Sun, the Moon, and the planet Venus.
Since people have been looking up at the stars Jupiter has been visible and was known as the "wandering star". This all changed when Galileo first 'discovered' Jupiter as a planet and it's four largest moons - Io, Europa, Ganymede and Callisto.
He also observed that the moons orbited the planet itself. This may seem like an obvious discovery today, but in those times the Earth was KNOWN to be the center of the universe. This simple observation was the very first proof of a center of motion not centered on the Earth. It was very hard to ignore this observation because it absolutely supported Copernicus's heliocentric theory of the motions of the planets. Meaning that the Earth was NOT the center of the universe....the sun was. This was such a controversial subject that Galileo's outspoken proof and support of the Copernican theory got him in trouble with the Inquisition. Today anyone can repeat Galileo's observations using an inexpensive telescope.
One of Jupiter's most interesting features is called the Great Red Spot, a huge storm of swirling gas that has lasted for hundreds of years. To give you a good idea of the size of Jupiter in comparison of Earth - here's a fun fact...three Earths would fit within the boundaries of the Great Red Spot alone! Pretty impressive huh!
The Romans were so impressed by this giant that they named this planet after their most powerful god "Jupiter", also known as Zeus to the Greeks. Jupiter is the Roman god of light and sky, and protector of the state and it's laws. The Romans worshipped him especially as Jupiter Optimus Maximus (all-good, all-powerful).
The 300 year storm...…
This planet is unique among it's rocky neighbors because it's a gas planet. That means that except for it's smaller solid core (something like 10 to 15 Earth-masses) the planet is made up entirely of gases! Jupiter is a ball of dense hydrogen, helium, water, nitrogen and other gases. This makes the environment on the planet very volatile. Lightning and hurricane like storms are caused by the powerful winds that dominate the atmosphere. The Red spot is a storm that has been raging for over 300 years and is almost 2 Earth diameters wide!! Jupiter takes about 12 years to orbit the sun and the planet itself rotates in about 10 hours giving it a very short 10 hour day. This short Jupiter "day" is amazing since the planet is roughly 11 Earth diameters wide.
Hot! Hot! Hot!
Jupiter radiates more energy out into space than it actually receives from the Sun. Jupiter's core is probably about 20,000 K. The heat is generated by the slow gravitational compression of the planet not like the sun that generated heat by nuclear fusion. Jupiter is much too small and is too cool to ignite nuclear reactions.
How many moons?!?
Jupiter is the most dense planet. It's a full 71% of the total matter found in the entire solar system! Jupiter's mass is so dense that it's gravity pulls very strongly, trapping objects in it's orbit. In fact, most of it's moons were captured because of it's gravity rather than forming at the same time that Jupiter itself was formed. At this time it has 60 known moons, with more being confirmed every year. As you can imagine, not all the objects simply start orbiting the planet, many crash to it's surface. Scientists watched in awe as the comet Shoemaker-Levy 9 broke up and smashed into Jupiter making explosions the size of the Earth.
Jupiter Quick Facts
- Jupiter has rings! Yup, Jupiter has five known rings, including the most recently discovered one that has a backward rotation.
- Jupiter takes about 11.86 Earth years (4330 Earth days) to orbit the sun.
- Jupiter's oribit takes only 10 hours compared the Earth's 24 hours.
- Jupiter with is roughly 11 times the Earth's diameter wide!
- Io, Europa, Ganymede and Callisto are Jupiter's four main moons.
- Jupiter is about the same age as our sun: 4.5 billion years old
- J Ganymede, a Galilean moon, is the largest moon in our solar system (larger than even the planet Mercury), and is the first moon known to have its own magnetic field.
Learn More About The Rest of The Planets: