P1bL12  Formation of the Solar System

Key Words

Asteroid belt - a collection of rocks and stones in orbit between Mars and Jupiter.

Aurora Borealis - the Northern Lights (in the Antarctic, these are the Aurora Australis)

Gas giants - huge planets with no rocky surface, instead made of gas and dust.

Magnetic Storm - bursts of activity from the sun, including distortions of its magnetic field.

Meteorite - lump of rock from Space falling into the atmosphere

Rocky Planet - planet with a rock surface.

Solar wind - a stream of particles shot out from the Sun.

Grade E

The Solar System formed from a disc of gas and dust that gathered due to gravity.  The largest mass formed the Sun which became a protostar, and finally lit.  The rest of the swirling dust formed a disc, and gathered into planets.

The four inner planets (Mercury, Venus, Earth, and Mars) are rocky.  They consist of a rocky outer layer around an iron and nickel core.

Then there are four gas giants (Jupiter, Saturn, Uranus, and Neptune).  These are basically balls of gas.  Deeper down the pressure is such that the gases are liquid.  In Jupiter, it is believed that hydrogen exists as a metal.  There is a small rocky core.  The density of Saturn is so low that if there were an ocean big enough, Saturn would float.

These eight planets all orbit the Sun in an anticlockwise direction (when viewed from above their North poles).

Pluto is a tiny double planet.  Some scientists have decided it's too small to be a planet; it has been reclassified as a planetoid.

A tenth planet, Sedna, was discovered in 2003.

There is evidence of planets elsewhere in the Universe.                                

Grade C

As the Solar system formed, it started to turn and formed a flattened disc.  Dust particles came together under the pull of gravity to form rocks.  It is believed that the solar wind from the newly lit sun blew the gases outwards.  In the outer reaches of the Solar System, it is cold enough for gases to condense.  The gas giants consist mostly of liquid hydrogen and methane.

The Asteroid Belt consists of lots of rocks and stones.  These are thought to come from a planet that failed to form.  There are larger objects like asteroids that also orbit in the asteroid belt, some of which are several kilometres long. 

Occasionally they get knocked out of orbit because of the action of Jupiter's huge gravity.  They can pass through the Earth's orbit.  A collision with Earth could be catastrophic.

Comets are dirty snowballs that arise in a far distant belt of dust and other particles called the Oort Belt.  Their orbits are highly elliptical and their tails point way from the Sun, because of the solar wind.  Halley's comet comes round every 86 years.  It was last seen in 1986, so you will be pensioners when it comes next time in 2072.

A comet looks like this:

The tails are thought to consist of dust and ionised gas.  The mass of a tail thousands of kilometres long is less than a breath of air.

The Moon is thought to have been formed when a planetoid collided with the Earth.  Both were destroyed, but the debris came back together.  The larger mass of rubble formed the Earth, and the smaller the Moon, which orbits the Earth.

Studies of meteorites show the age of the Solar System to be about 4600 million years.

Grade A

The Sun is very active.  It throws out about 1 million tonnes of material per second in all directions.  This solar wind travels at about 800 km/s.  It consists of charged particles.  It can come in gusts as a result of magnetic storms on the Sun, which result in lots of Sun Spots and massive flares of material.

These flares follow magnetic field lines (a bit like iron filings following the magnetic field of a bar magnet).  You can see the Earth to compare the scale.

The effect of magnetic storms are shown by:

• Aurora Borealis (the northern lights).  Charged particles are caught by the Earth's magnetic field and ionise gases to make them glow.

• Interference with electronic equipment.  Magnetic storms can knock out telecommunications equipment.