Primary Science Workshops

Primary school science workshops with a WOW!

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The Planets of our Solar System

The Solar System is now officially made up of eight unique planets, although it used to contain a ninth planet, Pluto, which we’ll come to in a moment.  At the centre of these is The Sun which holds all the planets around it in an orbit with its immense gravity.   In order from The Sun, the planets are as follows: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.


A good way of remembering the names of the planets in our solar system is with mnemonics (yes it’s spelt weird, say it like nu-mon-ick), like ‘My Very Easy Method Just Speeds Up Naming Planets’ if you include Pluto.

the planets of our solar system

What are the names of The Planets in the Solar System? 

Hmmm, This is a tricky one and one that takes a lot of explaining in our school space workshops. Pluto lives in a place called the Kuiper belt at the very furthest edge of the Solar System where a lot of similar (though smaller) objects also exist.  As science is based on facts, we have to recognise the findings of a group of scientists called the International Astronomical Union who came together in 2006 and redefined what being a planet meant.


It took a lot of complicated science and debate, but basically they concluded that Pluto simply wasn’t big enough to be a planet on its own.  They also thought that Pluto’s gravity wasn’t strong enough for it to be called a planet so they called it a dwarf planet instead.  

So is Pluto a planet?


However, many people are not happy with this decision, partly because they’ve grown up all their lives with Pluto as a planet and also because Pluto’s spherical shape and five moons make it look very much like the other planets of our solar system.  It might also be because writing the “My Very Easy Method..” mnemonic doesn’t make sense with Pluto missing from the end! What do you think? Should Pluto be classed as a Solar System planet or not?

Starting with the largest planets we have the gas giants, Jupiter, Saturn, Uranus and Neptune. These are absolutely gigantic and much bigger than the earth.  For example, the largest planet, Jupiter, would take 1321 earths to fill it up even though it only weighs 317 times as much because it is mostly gas.  This gas is mostly made up of light elements like hydrogen and helium.   Also, two of the planets, Uranus and Neptune, are called the ice giants, because they’re much cooler than the others.


Then we have the other four planets called terrestrial planets.  In other words, planets with a hard surface.  These are Mercury, Venus, Earth and Mars, with Earth the biggest of these. The smallest, Mercury, is closest to The Sun so is very hard to see, while Venus is the hottest (even though it is not the nearest to The Sun) because it has an atmosphere that holds in solar heat.





All of the planets orbit The Sun, which means they spin around it very fast, most in a circle but some, like poor old Pluto, are more of a squashed circle shape. In fact, there are times that Pluto is closer to The Sun than Neptune! Earth takes 365 and a quarter days to orbit The Sun fully, which is where we get the length of our years from, with an additional ‘Leap year’ day added every four years on 29th February to make up for the quarter of a day.  


Earth also takes one day to spin around on something called its 'axis', which is as if a stick has been inserted into the Earth from the top to the bottom for it to spin around on. This takes 24 hours, which is where we get our days and nights from. Then there’s The Moon, which takes approximately 27.5 days to orbit us. This lunar cycle is why we get moons of different shapes, like full moons and crescent moons.   In our school space workshop we use models of the earth and moon to demonstrate this.

How big are the planets?

What are the orbits of The Planets?

(Teachers, this is covered in much more detail in our Rockets to Rovers school space workshop)

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