The Romans named planet Jupiter after the king of the gods; Jupiter was also their god of the sky and thunder.
Jupiter is 5.2 A.U. or 778,500,000 km from the Sun and takes 11.9 earth years to orbit the Sun once.
Jupiter rotates in a near upright position; its angle of rotation, or axial obliquity, is only 3°.
Jupiter rotates faster than any other planet in our solar system- the exact speed of rotation depends on which part of the planet you measure.
On the equator one complete rotation, a jovian ‘day’, takes 9 hours and 50 minutes. Near the polar regions one complete rotation takes 9 hours and 56 minutes- a full six minutes longer.
Differential rotation, where equatorial regions rotate more rapidly than polar regions, is a characteristic of all gas giants.
The rapid rotation, together with the fact that the planet has a massive liquid and gas mantle….
produces a bulge at the equatorial regions that is oblate in shape.
This is what the oblate shaped Jupiter would look like if it were as close to Earth as the Moon.
1,321 Earths could fit inside Jupiter…
yet the planet only has 318 times more mass than the Earth.
Or to explain it another way, Jupiter only has 318 times more stuff inside it than Earth does. (read Understanding Gravity and Mass for an explanation of stuff.)
The gaseous stuff inside Jupiter is far less dense than the rocky stuff inside Earth.
The density of Jupiter’s gaseous stuff ( at 1.33 g/cm³) is less than a quarter of density of Earth’s solid rocky stuff (at 5.52 g/cm³). Jupiter’s gaseous stuff is not that much more dense than liquid water with a density of 1 gram/cm³.
The center of the planet has a rocky core which represents about 5% of Jupiter’s total mass. The core is located 60,000 kms beneath the planet’s ‘surface’.
Above the core lie three layers of hydrogen; gaseous hydrogen, liquid (or ‘molecular’) hydrogen and liquid metallic hydrogen.
This image shows what the sea of liquid hydrogen beneath the layer of gaseous hydrogen might look like.
The simple answer is that this change of state requires changes to gravitational pressure. (For an explanation of gravitational pressure refer to Uranus Planet of Diamonds)
This diagram shows the amount of gravitational pressure required for hydrogen to exist as a gas, liquid or liquid metal inside Jupiter.
Hydrogen can only exist as a higly compressed liquid metal under pressures greater than 4 million bars. Since the extreme pressures inside Jupiter could never be replicated on Earth, we will never see any liquid metallic hydrogen.
Liquid metallic hydrogen may look something like the element mercury, which can exist on Earth in a liquid metallic form.
Liquid hydrogen, comprising atoms of one electron orbiting a proton…..
becomes metallic when, under extreme pressure, electrons become detached from their orbits.
With electrons freed from their orbits, liquid metallic hydrogen possesses the ability to conduct both heat and electricity.
As the liquid metallic hydrogen moves around inside Jupiter it conducts electricity.
The electric currents then supply energy that generates Jupiter’s large magnetic field.
Jupiter’s magnetic field is 20,000 times stronger that Earth’s and is by far the largest of any planet our solar system.
If it were visible from Earth we would be able to see the tail of Jupiter’s magnetic field extending for a distance of 600 million kilometers.
Jupiter’s intense magnetic field traps charged particles from the solar winds. (refer to Earth as a Magnet for an explanation of solar winds)
These charged particles form a lethal radiation belt that would be hazardous to any visiting astronauts. Any astronaut exposed to such hazardous levels of radiation would receive a dose of 400,000 rads, or 1,000 times the lethal dose for humans.
This image shows how the radiation belt moves as Jupiter makes a 10-hour rotation.
When charged particles travel along magnetic field lines they interact with Jupiter’s atmosphere to produce aurora. The light generated by this interaction between charged particles and the atmosphere are the most intense in the Solar System.
It even rains inside Jupiter- not the liquid water rain we see on Earth but liquid helium rain.
In this beaker green colored water has been mixed with oil. The two liquids are immiscible – that is they do not mix. Not only are water and oil immiscible, but water is denser that oil. As a result the water descends through the oil as ‘rain’.
A similar process occurs on Jupiter. Liquid helium and liquid metallic hydrogen are immiscible; liquid helium is also more dense than liquid metallic hydrogen. The liquid helium descends through the liquid metallic hydrogen as helium rain.
Eventually the falling droplets of helium rain reach a higher pressure zone at which point they become metallic. When helium becomes metallic it mixes with the metallic hydrogen.
Jupiter has no solid surface for scientists to use as a starting point for calculating altitude.
Scientists make all calculations of altitude based on the point in the atmosphere where the atmospheric pressure registers 1 bar. 1 bar happens to be the atmospheric pressure at sea level on Earth.
The troposphere, the lowest part of the atmosphere, extends for an altitude of 56 km below 1 bar atmospheric pressure. The troposphere contains three separate cloud decks all of which can be found at different altitudes.
The altitude of the cloud decks depends on the ambient temperature of the troposphere.
Water condenses at a higher temperature than ammonium hydrosulfide or ammonia, so water clouds form the lowest cloud deck.
At a higher altitudes temperatures are low enough for ammonium hydrosulfide to condense to form clouds. Near the top of the troposphere, where temperatures are even lower, ammonia condenses to form clouds.
This image gives an impression of what ammonia clouds, with a deck of ammonium hydrosulfide clouds below, might look like.
It is the different cloud decks of the troposphere that we see when we look at images of Jupiter.
The lighter colored bands are zones; the zones represent regions of high pressure in which gases warm up and rise.
The dark colored bands are belts; the belts represent regions of low pressure in which gases cool down and sink.
The zones and belts lie above regions of upward and downward moving convection currents. How deep these convection currents flow is not yet known.
It is above the upflowing convection currents that ammonia clouds form. When the air is depleted of ammonia after ‘ammonia snow’ falls, we are able to see ammonium hydrosulfide clouds below.
Zones and belts are Jupiter’s equivalents of the high and low pressure systems that drive our weather on Earth. On Earth high and low pressure weather systems are localised.
On Jupiter the high pressure zones and low pressure belts continuously circle the planet.
The prevailing winds in these high and low pressure systems have changed very little in the 300 years that scientists have been studying them.
The long arrows in this image show faster wind speeds. Wind speeds reach 340 mph (547 km/h) in equatorial regions.
Powerful storms also blow in the troposphere. The high pressure storms of the southern hemisphere can be seen as these white ovals.
The great Red Spot is the best known of all storms blowing on Jupiter. Around the edges winds blow at 432 km/h.
Although it appears to be now decreasing in size it…
has been in existence since 1677 when it was first recorded by the Italian astronomer Gian Domenico Cassini.
On Earth large storms form over oceans and may survive for many days. They quickly die after making landfall; land disrupts the storm’s energy and flow patterns that sustain the storm.
Jupiter has no land; once a storm has become established it just keeps on going- so long as it has reached such a size that other storms cannot destroy it.
At its widest the storm blowing in the Great Red Spot is 16,500 in diameter.
Storms are often accompanied by lightning strikes. These images, taken from a distance of 2.3 million kms, show extensive lightning strikes in different regions of the troposphere.
The largest lightning strikes are 5oo kms in width!
As on Earth, jovian storms are caused by a process of convection. Gases, including water vapour, rise from deep within the planet. As they freeze ice particles rub past each other and build a charge which is discharged as lightning.
The storms on Jupiter are more massive and intense than on Earth.
It is the internal source of heat that is responsible for driving the complex weather patterns in the jovian atmosphere; in contrast the primary heat source responsible for driving the Earth’s weather is the Sun.
Most of the heat flowing from the jovian interior is primordial; primordial heat is the heat which is left over from the formation of Jupiter some 4.5 billion years ago.
4.5 billion years ago Jupiter spun even more rapidly than it does today; its shape would have been even more oblate then. The planet has now lost much of its heat and become more spherical in shape.
Jupiter radiates 1.6 times more energy outwards from its interior than it receives inwards from the Sun. The internal heat radiating from the jovian interior can be seen in this infrared image.
Clouds in the high pressure zones look darker under infrared light. These are the same clouds that shine really bright under visible light. Clouds in the zones block the heat generated from deep inside the planet.
In contrast the belts of low pressure are far warmer; when we look at the belts we see far deeper into Jupiter’s atmosphere.
A thin ring system surrounds the planet. Unlike Saturn’s rings, which are clearly visible from Earth, Jupiter’s rings are very difficult to see; they were not discovered until 1979.
Rings form when small projectiles, including meteorites…
strike the surfaces of Jupiter’s inner moons.
The resulting collisions kick up dust….
into orbit, forming rings.
Jupiter has three faint…
…and very narrow rings.
Dust particles inside the rings eventually fall into the planet. Dust needs to be continuously replaced for the rings to continue existing. The lifetime of dust particles inside the rings can be anything up to 1000 years.
Still plenty more to learn about Jupiter!
There is still a great deal that we do not understand about the amazing jovian atmosphere.
Scientists have yet to understand the complex chemical reactions that produce that amazing, subtle range of spectacular colors in the jovian atmosphere….
that make for beautiful jewelry!