My Science School

Pluto is the coldest planet of all, which is not surprising, because it is usually the farthest from the Sun. Inside, it is made up of ice and rock, and the planet has a thick layer of ice over the top.

Is it true? Pluto was named after a cartoon dog.

No. Pluto was the name of the Greek god of the underworld. Also, the first two letters of Pluto, ‘P’ and ‘L’ are the initials of Percival Lowell, who first predicted a planet beyond Neptune.

Who found Pluto’s moon?

An American called Jim Christy discovered Pluto’s moon in 1978. He called it Charon, which was his wife’s name, and also the name of the man who ferried people to the underworld in Ancient Greek mythology.

Is Pluto always farthest from the Sun?

Pluto is so far away from the Sun that it takes 248 years just to orbit it once! But Pluto’s orbit is a funny shape. For 20 years of its orbit, Pluto dips in closer to the Sun than Neptune. When this happens, Neptune is the farthest planet in the Solar System.

Amazing! Pluto is smaller than a country. Pluto is a tiny planet - the smallest in the Solar System. At 2,360 km across, it is smaller than the United States or Russia!

Astronomers knew Neptune must be there before they saw it! They could tell something big was pulling Uranus and they were able to predict exactly where Neptune was – almost 4.5 billion kilometres away from the Sun.

 What’s the weather like on Neptune?

Very, very windy! Winds rip across the planet all the time, much faster than any winds on Earth. There are also lots of storms on Neptune, which show up as dark spots. This means Neptune’s appearance is constantly changing.

Is it true? Triton is Neptune’s only moon.

No. Neptune has seven other moons, but Triton and Nereid are the main ones. Triton is the biggest. It is 2,706 km across – about four-fifths the size of our Moon.

Where would you find pink snow?

When the gas nitrogen freezes, it looks like pink snow! There is frozen nitrogen at Neptune’s north and south poles, and at the poles of its largest moon, Triton. So far from the Sun, Neptune and its moons are bitterly cold places.

Amazing! Triton is one of the coldest places ever recorded! The temperature on the ice-covered moon is minus 236°C. That’s just 37°C away from being the lowest possible temperature in the entire Universe!

Picture Credit : Google

Uranus was discovered in 1781. The man, who found it, William Herschel, was not expecting to find a planet at all. He thought he was pointing his homemade telescope at a distant star.

How many moons does Uranus have?

Uranus has at least 17 moons - but there could be more to discover. They are all named after characters from English literature. The main ones are Oberon, Titania, Umbriel, Ariel

and Miranda. Ophelia and Cordelia are the closest.

Amazing! The poles on Uranus are warmer than the equator. Because Uranus is tilted on its side, the poles are the warmest places on the planet. Summer at the South Pole lasts 42 years!

Why is Uranus blue?

The bluish-green is the colour of methane, a stinky gas that makes up part of Uranus’s atmosphere. The other gases in the air there are hydrogen and helium - the gas we use to fill party balloons.

Is it true? Uranus was nearly called George.

Yes. When Herschel discovered the new planet, he wanted to name it after the English king at the time, George III. In the end, it was called Uranus, after the Greek god of the sky.

Picture Credit : Google

Mars was named after the Roman god of war, because of its blood-red colour. The planet looks rusty red because its surface is covered with iron-rich soil and rock. There are no seas on Mars, and it is very cold.

Do Mars have ice at its poles?

Yes. Its south pole is mostly ‘dry ice’, which is frozen carbon dioxide gas. At the North Pole there may be frozen water, mixed with the frozen carbon dioxide. There may be frozen water underground on Mars, too.

Is it true? There is life on Mars.

No. Or at least, there’s no sure sign of any. But long ago, Mars had flowing rivers of water, so there could have been life once, and there may be fossils buried underground.

What are Mars’s   moons like?

Mars’s two tiny moons, Deimos and Phobos, are not round like our Moon. They look more like baked potatoes! They might have been asteroids (space rocks) that Mars captured with its gravity.

Amazing! There’s a record-breaking volcano on Mars. Olympus Mons is about 600 km across and towers over 25 km high. It’s the Solar System’s biggest volcano. Long ago it spurted out runny rivers of black lava.

Picture Credit : Google

It doesn’t really – it’s ball-shaped just like the Earth, but as the Moon travels around the Earth, you see different amounts of its sunlit half. It seems to change gradually from a crescent to a disc, and back again.

Why does the Moon have so many craters?

Because it has been pelted by so many space rocks and has no atmosphere to protect it. One of the biggest craters, called BailIy, is nearly 300 km across. You can make out some of the craters using a good pair of binoculars.

Amazing! You can jump higher on the Moon. The Moon’s gravity is much weaker than Earth’s. This means you would only weigh about a sixth of your Earth-weight there - and you’d be able to jump six times higher!

What is the dark side of the Moon?

It’s the part of the Moon that we can never see from Earth. The Moon takes the same time to orbit the Earth as it does to spin once. This means the same side of the Moon always faces away from the Earth.

Is it true? There are seas on the Moon.

Yes and no. There are dark, rocky plains and craters called maria (Latin for ‘seas’), but they don’t contain water. The first astronauts to visit the Moon landed on the Sea of Tranquility.

Picture Credit : Google

As far as we know, Earth is the only planet in the Solar System that has life. As well as warmth from the Sun, the other main ingredient for life is liquid water. Earth has plenty of water - in total, it covers about three-quarters of the planet’s surface!

Is it true? There was life on Earth from the start.

No. When Earth first formed it was extremely hot and there was no oxygen. Over millions of years, the planet cooled, oceans formed and oxygen was made. The first life on Earth appeared about 3 billion years ago.

What does Earth look like from space?

It looks beautiful - blue with swirling white clouds. Astronauts in space spend most of their free time gazing at it. They can even make out cities, when they are lit up at night with twinkling lights.

Amazing! The Earth is magnetic. At the centre of the Earth is a core of a molten metal called iron, which makes our planet like a giant magnet. This is what pulls the needle on a compass towards the magnetic North Pole.

Why does our sky go dark at night?

Like all planets, the Earth is spinning as it orbits the Sun. When your part of the planet is facing away from the Sun, its light is blocked out. At the same time, it is daytime for people on the opposite side of the Earth.

Picture Credit : Google

When it’s a planet! Venus is sometimes called the ‘evening star’ because it’s so bright it’s one of the first points of light we see shining as it gets dark. Planets don’t make their own light - they reflect the Sun’s light.

Is it true? Venus is bigger than the Earth.

No. Venus is a fraction smaller than the Earth, but not by much. Venus is about 12,104 km across, whereas Earth is about 650 km wider. Venus’s mass is about four-fifths of Earth’s.

How can a day be longer than a year?

A day is the amount of time a planet takes to spin on its axis, and a year is the time it takes to travel around the Sun. Venus spins on its axis very slowly, but orbits the Sun more quickly than Earth. A day on Venus lasts 243 Earth-days, but a year is only 225 Earth-days.

Amazing! Venus is named after a goddess. Venus was the name of the Roman goddess of love and beauty – just right for the planet, which many people think is the most beautiful object in the sky.

Picture Credit : Google

Solar means ‘of the Sun’. The Solar System is centered on the Sun, the shining ball in the sky. It includes the family of nine planets orbiting (travelling around) the Sun, as well as the moons of these planets, and smaller objects, such as comets, asteroids, and bits of space rock. The powerful pull of an invisible force called gravity from the Sun stops these bodies from flying off into deepest space.

Is it true? All planets have one moon.

No. Our planet Earth has one moon, called the Moon. But many of the planets have more than one. Our neighbour Mars, for instance, has two! Only the two planets closest to the Sun - Mercury and Venus - have no moons at all.

Amazing! Saturn’s not the only planet with rings. Saturn’s rings are the easiest to see, but Jupiter, Neptune and Uranus have them, too. Saturn has seven main rings, and then hundreds of thinner rings, called ringlets.

Picture Credit : Google

In deserts here on Earth, heat that has travelled 150 million km from the Sun can be hot enough to fry an egg. The Sun’s surface is a super-hot 6,000°C, and its centre or core is even hotter.

Amazing! The Sun is a star - a gigantic ball of burning gas. It has been shining for about five billion years.

Why must you never look at the Sun?

Not even sunglasses fully protect your eyes from the Sun’s dangerous ultraviolet (UV) rays. UV can burn your eyes and make you blind. If you want to see the Sun safely, ask an adult to show you how to project its image on to a sheet of paper.

Is it true? The Sun has spots.

Yes. The Sun is not the same colour all over. Some areas of its surface are darker. These spots are little pockets that are slightly cooler. Of course, sunspots are only ‘little’ compared to the Sun - some grow to be as large as Jupiter, the biggest planet in the Solar System!

When does the Sun go out?

When there’s a total eclipse. This happens when the Moon’s path takes it between the Earth and the Sun, and the Moon casts a shadow across the surface of the Earth.

Picture Credit : Google

Planet Mercury looks very like our Moon. It’s about the same size and it’s covered in craters, where bits of space rock have crash-landed on its surface. The biggest crater is the Caloris Basin, which is about 1,300 km across. Mercury also has huge plains, rolling hills, deep gorges, chasms, and cliffs.

Is it true? Mercury is the smallest planet.

No. Mercury is only about a third the size of the Earth, but Pluto is even smaller. If you could put them on the scales, it would take 21 Plutos to balance one Mercury.

Is Mercury the hottest planet?

Mercury is the planet closest to the Sun, but its neighbour Venus is even hotter, because it has clouds to keep in the heat.

What is the weather like on Mercury?

Mercury doesn’t have any weather, because it has no air and hardly any atmosphere. That means there are no clouds to shield the surface of the planet from the baking-hot Sun during the day, or to keep in the heat at night. There is no wind or rain on Mercury, either.

Amazing! Mercury is the fastest planet. Mercury zooms around the sun in just 88 days, at an incredible 173,000 kph. That makes it faster than any space rocket ever incented.

Picture Credit : Google