EVERYTHING YOU NEVER KNEW ABOUT OUR SOLAR SYSTEM

Imagine doing a job that means you get to study the stars, the planets, the universe... That’s what astronomers do. Let’s explore some of what they know about our solar system.

Using super-strong equipment like giant telescopes, astronomers study life beyond the limits of our Earth. But for now let’s just look at our solar system – there’s so much out there that the information would fill a few hundred books, if not more.

All the planets in our solar system orbit (travel round) the Sun. The time it takes for each one to go right round the Sun is a ‘year’ for that planet. Each one also rotates on its own axis (like an imaginary pole going through its centre), and the time it takes to do a full rotation is a ‘day’ for that planet. The Sun is the star of our solar system (‘solar’ comes from the word ‘sol’ which is Latin for sun). All of the planets in our system are bound to the Sun by gravity, which keeps them travelling around it at different speeds and distances. Our solar system is in an outer spiral arm of the Milky Way galaxy, which is that cloudy-looking concentration of several hundred billion stars that we can see in the night sky. It is just one of billions of other galaxies in the universe!

WEIRD AND WONDERFUL
Jonathan Swift wrote about the moons of Mars (Phobos and Deimos) in Gulliver’s Travels 151 years before they were even discovered! A crater on Deimos is named after him.

OUR SOLAR SYSTEM

THE SUN – our source of life
The Sun is one of billions of others like it across the Milky Way galaxy. Without it, there would be no life on Earth. It’s as big as a million Earths, and about 4.5 billion years old. The Sun takes up 99% of all the matter in our solar system. Nearly 150 million kilometres away from Earth, it’s made up of very hot gases (about 92% hydrogen and 8% helium). Even though the Sun is so far away from Earth, the sunlight we see left it just 8 minutes ago!

COMETS
These are ‘snowballs’ containing frozen gas, rock, and particles of dust that orbit the Sun. When they get near the Sun they heat up, leaving a trail of glowing dust and gases.

THE MOON – satellite of love The Moon is the largest and brightest object we can see in the night sky, and it’s the only place other than Earth that humans have visited. It’s also the Earth’s only natural satellite (an object that travels around it). It takes a month to go round Earth. The Moon’s gravity causes ocean tides, and the Moon has the job of keeping Earth steady on its axis.

WALKING ON THE MOON
The first person to stand on the Moon was Neil Armstrong. The Apollo 11 spaceship blasted off from Earth on 16 July, 1969, with three American astronauts – Armstrong, Edwin ‘Buzz’ Aldrin and Michael Collins – on board. Four days later, on 20 June, Neil Armstrong became the very first human to set foot on the Moon. Aldrin also walked on the Moon, while Collins stayed in the spaceship. The three returned safely to Earth on 24 July, 1969.

MERCURY – the ‘quicksilver’ planet
Mercury was named after the Roman messenger god. It’s the smallest planet, and moves the fastest around the Sun, going at a speed of about 47 kilometres per second. It’s the closest planet to the Sun (well, that’s if you think 47,91 million kilometres is close!) and takes 88 Earth days to orbit it. This means one year on Mercury is the same as 88 Earth days – the shortest year of any planet. Even though it’s so close to the Sun, it’s not the hottest planet.

VENUS – planet of beauty
Venus is named after the Roman goddess of beauty – in fact it’s the only planet named after a female deity (goddess), and the symbol of this planet of love and strong women has been adopted as the symbol of womanhood. After the Sun and the Moon, Venus is the brightest object we can see in the sky. It’s also the hottest planet. It takes 225 days to orbit the sun, so one Venusian year is 225 Earth days. The funny thing is that one Venusian day (the time it takes for Venus to rotate on her own axis) is longer than that – it’s about 243 Earth days.

EARTH – 3rd rock from the Sun
Earth is the third rock from the Sun (really), and the only planet, that we know of so far, with life on it. Believed to have formed about 4.5 billion years ago, it’s more water than earth. About 71% of the surface is covered by water, and 29% by land. Asia, the largest continent on Earth, covers about 30% of it, and is home to around 60% of the world’s people.

WHAT CAUSES NIGHT AND DAY?
Earth makes one complete turn on its axis in 24 hours, which is why our days are 24 hours long. Over the 24-hour period, the side of the Earth that’s facing the Sun has daytime, while the other side has night.

MARS – the ‘Red Planet’
The average temperature on Mars is about -60 ̊C – but in winter it can get to around -125 ̊C. Named after the Roman god of war, its symbol is the symbol for the male gender. Mars is home to the tallest volcano in our solar system – Olympus Mons, that’s 21 kilometres high! One rotation, or day, on Mars takes 24.6 hours, much like Earth’s, but it takes 669.6 days on its trip round the Sun.

JUPITER – king of the gods
Jupiter is 318 times the size of Earth! It has a ‘Great Red Spot’, an area with a constant storm that’s been observed since 1830. Named after the Roman god of sky and thunder (the ‘king of the gods’), it turns on its axis once every 10 hours, so the Jovian day is the shortest of all the planets in our solar system, but a year is about 12 Earth years.

SATURN – the ‘Ringed Planet’
Named after the Roman god of harvest and time, Saturn is the planet that’s easiest to recognise, with a system of icy rings around it. Its surface area is about 83 times bigger than our planet, and it’s the second-largest planet after Jupiter. Saturn does a complete rotation on its axis in about 10.6 hours (a Saturn ‘day’), but it takes about 29.5 years to go right round the Sun.

URANUS – formerly known as George
For about 70 years, until 1850, Uranus was known as Georgium Sidus (or George for short), after England’s King George III. Then the name was changed to celebrate the Greek god of the sky, Ouranos. The third biggest planet in our solar system (about 63 times bigger than Earth), it takes 84 Earth years to orbit the Sun – but just 17 hours to turn on its axis. Its temperature is -224 ̊C!

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NEPTUNE – the‘Big Blue Planet’
Neptune is the fourth largest planet in our solar system (17 times the size of Earth), with the strongest wind speeds. It’s the planet that’s furthest away from the Sun, at about 4,8 billion kilometres! Named after the Roman god of the sea because of its bluish, ocean-like colour, Neptune takes 165 years to go around the Sun – but one ‘day’ is just 16 hours.

PLUTO
Pluto used to be called a planet, but was demoted to ‘dwarf planet’ in 2006. Named after the Roman god of the underworld, it’s only about one-sixth the width of Earth. One day on Pluto is around 153 hours, and its trip around the Sun takes 248 of our years.

BLAST OFF!
Engineers at the National Aeronautics and Space Administration (NASA) in the USA are preparing the James Webb Space Telescope for its launch into space on 31 October from French Guiana on the coast of South America. It will be the biggest, most super-powerful space science observatory of all time. Its infrared eyes will be able to see some of the oldest, most distant stars in the universe and one of its jobs will be to search for life on other planets. The plan is for it to spend six months travelling to a ‘gravitationally stable’ spot more than 1.6 million kilometres from Earth.

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FIND THE WAY
Follow the paths – A, B and C – to find out which one will take you to the spaceship. Once you’ve found it, colour in the path with a crayon or coloured pencil.