Page 17 - Curriculum Visions Dynamic Book

From its size and density we can also tell what the pressure is like in the centre of this giant planet.
It is probably something like 50–100 million
Earth atmospheres.
We are used to hydrogen being a gas, but
at this enormous pressure hydrogen turns
into a substance that looks like a metal. The
centre of Jupiter is thus mainly metallic
hydrogen. We say “mainly” because if the
core were entirely hydrogen, it would have
to be a lot bigger in order to explain its
mass. So there must be other—and heavier— elements there too. The most likely element is helium, in a ratio of about 1 part helium to 14 parts hydrogen. That is what is found in the Jovian atmosphere.
Does this metallic liquid go to the very centre of Jupiter? Almost. Most people think that there is a relatively tiny solid rock core, perhaps between one and ten Earth diametres in size. Of that, however, we have no evidence at all except to say that all planets are thought to begin as rocky cores, and then some develop huge atmospheres.
The formation of Jupiter
Jupiter is such a vast planet that its origin has to be very different from the other planets in the solar system. The core probably formed at an early stage by the sweeping up of dust in the solar system.
As the planet formed, gases would have been released. That provided the early atmosphere. More gas could have been pulled in from space by gravity in much the same way as happened with the Sun. This process caused the atmosphere to get thicker and thicker.
Jupiter is almost big enough to have formed into a sun. Instead, it remains a distant, cold planet. So where does all
of the heat come from? Some is perhaps left over from the time the planet formed (as on Earth), and some is perhaps produced as gases like helium condense to liquid due to the vast pressures near the core. If this were true, the explanation
Metallic hydrogen
 The structure of Jupiter.
aurora A region of illumination, often in the form of a wavy curtain, high in the atmosphere of a planet.
core The central region of a body. density A measure of the amount of
matter in a space.
gravity The force of attraction between bodies.
hubble space telescope An orbiting telescope (and so a satellite) that was placed above the Earth’s atmosphere so that it could take images that were far clearer than anything that could be obtained from the surface of the Earth.
mass The amount of matter in an object. pressure The force per unit area.
ultraviolet A form of radiation that
is just beyond the violet end of the visible spectrum and so is called “ultra” (more than) violet. At the other end of the visible spectrum is “infra” (less than) red.
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