The Solar System

Warning the Sun is very dangerous
You must never look at the Sun through a telescope or any other optical instrument as it may permanently damage your eyes!

The Sun

At the centre of our solar system the Solar System is a Star we call our Sun which is a yellow G type dwarf Star and was almost certainly responsible for all the Planets and debris that surround it. It’s nearly a million miles across and a long, long way from our Earth – 93 million miles and if you were able to drive there in a car it would take you 180 years to get there. (That means there would be a skeleton in the car time you reached there!)

The Sun is a huge ball of gas that burns by turning Hydrogen into Helium at a loss of 4.3 million tonnes of its mass every second but don’t worry, there is enough fuel to keep it burning that way for at least 5,000 billion years into the future, so our Sun is only half way through its life.

It is fair to say that all the Stars we see twinkling in our night sky are all Suns, most of which make up part our Milky Way Galaxy and look like a band of luminous light that can be seen very clearly if you live in the countryside, unfortunately this cannot be seen from our towns because of light pollution from our street lamps.

The Sun has a surface temperature of 6,000k near the surface and 14 million degrees at its core and a rotation period of 25 Earth days.

The Planets

Mercury is the closest planet to our Sun and at present holds the title of being the smallest since Pluto was demoted to a dwarf planet by The International Astronomical Union in 2006! (See Pluto)

Mercury has a diameter of 4878 km (3000 miles) and orbits the Sun in just 88 days and because of its orbit the surface temperature varies between 100-800 k, so it’s scorching hot in the daytime and very cold at night. Mercury rotates in 59 Earth-days and has no moons. Mercury was named after the Roman messenger God Mercury.

Venus – (Very bright morning or evening Star)

Venus is similar in size to the Earth with a diameter of 12,104 km (Earth = 12,756 km) and has often been hailed as the Earth’s sister planet but that’s as far as the similarity goes. It has been wrongly named the goddess of love; in fact far from being a loving and friendly world it has an atmosphere of carbon dioxide, deadly sulphuric acid rain and temperatures reaching up to 1000 degrees.

Venus rotates once every 243 Earth days and takes 225 Earth days to orbit the Sun, which means its day is longer than its year. Venus has no moons. Nothing outshines Venus apart from the Sun, Moon and the International Space Station when it flies over!


This is our world, the third planet from the Sun; two thirds of the Earth’s surface is covered by its oceans, and it is known as the blue planet when seen from outer space. The Earth has a diameter of 12,756 km and rotates on its tilted axis of 23.5 degrees once every 24 hours (23hrs 56min 4sec) = (1 day).  It is the Earths tilt that gives us the seasons. The Earth takes 365 days and 6 hours to orbit the Sun (1 year) so every 4 years we add up the 6 hrs, 4 x 6 hrs = 24 hrs giving us one extra day and that’s why we have a leap year!

Life exists on Earth because of what is termed as the Goldilocks Effect (a planet that is not too hot and not too cold). The Earth is 93 million miles from the Sun and has an atmosphere composing of approximately 78% nitrogen, 21% oxygen & 1% argon.

The rest is made up of other noble gases, hydrogen and carbon dioxide.  Because of our ocean waters, the Sun’s light and heat and amino acids from comets, this has given the Earth the basic building blocks for life.

The Earth has a solid core of iron/nickel and an inner mantle of 6,000ᵒ c, about the same temperature as the surface of the Sun, (hot enough to melt rock). This makes the Earth’s surface ever changing (plate tectonics) and is responsible for our Earthquakes and Volcanoes!

The Moon

The Earth has one Satellite which we call the Moon. In 1969 NASA launched their great Saturn 5 rocket, (the largest rocket ever built), sending its Apollo 11 astronauts to the Moon.  On the 20th July it successfully landed two astronauts, Neil Armstrong and Edwin “Buzz” Aldrin on the Luna surface in the lunar module lander Eagle, whilst Michael Collins remained in the command module Columbia.


Mars is known as the red planet because it appears as a red star in the night sky.  It was also known by the Romans as the God of War.  Mars has two small satellites (moons) Phobos & Deimos.

Mars has an equatorial diameter of 6,794 km and rotates once every 24 hr 37 min 22.6 sec and takes 687 Earth days to orbit the Sun. Because Mars’ axis is tilted over at 24ᵒ it has 4 seasons just like our Earth but much colder and has much larger pole caps with temperatures of -123ᵒc all year round, 26 ᵒc in the day and -111ᵒc at night for the rest of the planet, so Mars is a very cold world and has dust storms with winds of up to 600 miles per hour.

If you hold a pair of binoculars steady on the back of a chair, garden wall or even better a tripod you will see a round white disk of Jupiter and 4 stars all in a line but those are not stars they are the 4 largest moons of Jupiter and each hour you can watch the moons change position.  Jupiter does have a none reflective ring system that unfortunately cannot be seen from Earth.

In 1994 comet Shoemaker-Levy 9 crashed into Jupiter after Jupiter’s strong gravity force broke the comet up into 23 pieces and put it on a deadly collision course with Jupiter and as the event unfolded the world watched and began to see dark collision marks appear on the surface of Jupiter. It did not cause any harm to Jupiter.

The Asteroid Belt

The Asteroid Belt lies between Mars and Jupiter and believed to be the debris left over from the formation of our Solar-System.  The largest is Ceres with a diameter of 913 km (567 miles).


Jupiter is the fifth major planet from the Sun and the largest planet in the Solar-System.  It is a huge ball of gas, in fact 1,300 Earths would fit inside Jupiter and 3 of our worlds would fit sideways in its giant red spot which is believed to be a vast storm.

Jupiter has over 70 satellites (moons), possibly more and its 4 largest Moons are collectively known as the Galilean Moons Ganymede, Callisto, IO & Europa, Ganymede being the largest, all named by the Italian astronomer Galileo Galilei (1564-1642) who discovered them on 7th January 1610.

Jupiter has a diameter of 142,800 km and rotates in just 9¾ of our Earth hours and orbits the Sun in 11.86 Earth years. Because of its size Jupiter is very easy to observe through a telescope.  It shows up as a bright Star in the night sky and its equatorial belts, red spot and moons will give a good display.

Saturn has a diameter of 120,536 km and a rotation period of just 10 ½ hours and takes 29.5 Earth years to orbit the Sun. Saturn is also classed as a gas ball planet with a density so low that if you could find an ocean big enough, Saturn would float! Saturn’s largest moon Titan has an atmosphere of nitrogen, so perhaps life could form there one day.

Jupiter has a Great Red Spot, Saturn has a Great White Spot, discovered in 1933 by the comedy actor Will Hay who often played the black and white screen part of a tottery old school teacher.

Saturn’s Rings are made up of thousands of chunks of dust, rock and ice, as discovered by NASA’s space craft Voyager’s 1 & 2 during the 1980’s flies by.


Saturn is the sixth major planet from the Sun and is a wonderful sight.  Unfortunately you do need a telescope to see the rings as 10×50 type binoculars will just show as a roundish blob. There can’t be many astronomers amateur or professional that hasn’t said “Wow” at their very first sight of Saturn through a telescope.  Looking for Saturn in the night sky it will show as a bright yellowish Star.

Like Jupiter, Saturn also has its fair share of moons (65 at present) and possibly more! Launched in 1997 NASA’s space probe Cassini spent a seven year journey to reach Saturn but a well worth trip, mapping, measuring and sending back stunning photos of this beautiful world.

It is fair to say that all the Stars we see twinkling in our night sky are all Suns, most of which make up part our Milky Way Galaxy and look like a band of luminous light that can be seen very clearly if you live in the countryside, unfortunately this cannot be seen from our towns because of light pollution from our street lamps.

The Sun has a surface temperature of 6,000k near the surface and 14 million degrees at its core and a rotation period of 25 Earth days.


Uranus is another one of our giant gas ball planets, orbiting 7th place out from the Sun. Uranus was discovered by British

Astronomer William Herschel in 1781 at his home in Bath and he wanted to call it King George who reigned at the time.

Uranus has a diameter of 52,400 km (32,560 miles) and takes 84 earth years to orbit the Sun on an axis that has been tipped over on its side by ninety-two degrees (therefore its poles will spend 42 years in sunlight followed by 42 in darkness). The average temperature is -200ᵒc.

Uranus has 27 known moons (possibly more); Titania being the largest 1,580 km. (980 miles) and the length of a day on Uranus is approximately just over 17hours.

In 1986 NASA’s Voyager 2 was the first spacecraft to visit Uranus.


The furthest and the smallest of the outer gas ball giants with a diameter of 47,150 km (29,297 miles).  It gets its name from the Roman God of the Sea. Neptune orbits at a distance of 4345million km (2,700 million miles) from the Sun, its day is just over 16 hours and its year (once round the sun) is 165 earth years.  Neptune has winds of over 1,300 MPH and an average temperature of -214ᵒc. Neptune has 14 known moons (possibly more) the largest is Triton.

Neptune was discovered in 1846 by Jean LeVerrier and NASA’s Voyager 2 spacecraft was the first to fly by in 1989!

Dwarf Planet Pluto & The Kuiper Belt

Beyond the orbit of Neptune lies the Kuiper Belt, a large swarm of debris left over from the formation of the Solar System in which Pluto was downgraded to in 2006. Pluto then only had 1 moon Charon. However,  in 2015 the NASA space probe New Horizons arrived at Pluto and discovered 4 new moons, so Pluto now has 5 moons altogether, so perhaps it should be upgraded to being one of the main planets in the Solar System again even though our own moon is a lot bigger and the dwarf planet Eris is slightly larger!

Pluto was discovered by American astronomer Clyde Tombaugh in March 1930 at the Lowell Observatory, Flagstaff, Arizona. Tombaugh was given the predictions of such a planet by Percival Lowell and a year into his search he found it.

Pluto has a diameter of 2,379 km and an average temperature of  -233ᵒc and takes 248 earth years to orbit the Sun and a day equal to just over 6 earth days.

As well a Pluto there is other dwarf planets in the Kuiper Belt such as Eris, Haumea & Makemake along with other rocky asteroid type objects and dust from comets.

The Oort Cloud

Far beyond the outer reaches of our Solar System there lies a big swarm of comets called the Oort Cloud named  after Jan Oort who worked out the evidence of its existence in 1950.  Comets might get dislodged by colliding with other comets in the Oort cloud and send them heading in towards us by the gravitational force of the Sun and our Planets.

Our Galaxy

Our Galaxy is called The Milky Way, it is a spiral type Galaxy and looking at it sideways on it would look like two fried eggs stuck back to back and looking down from top it would resemble a firework catherine wheel we light on Guy Fawkes night. Away from city lights it can be seen on a clear night as a faint band of light.

We live on the outer edge of the second spiral arm in which enables us to look out see other Galaxies; unfortunately we cannot see the centre of our own Milky Way Galaxy as its hid up in the dusty star fields of Sagittarius, but it is believed there is a Supermassive Black Hole in the centre of our Galaxy as most other Galaxies seem to abide, so why should ours be any different.