The Universe is everything! It comprises everything we can see, hear, touch and detect. The Universe is enormous – it’s so big that we can’t even see the edge of it, if there even is one. The part of the Universe we can see is at least 93 billion light years across. A light year is the distance light travels in a year (about 9 trillion kilometres). So multiply 9 trillion kilometres by 93 billion and that’s how big the visible Universe is!
The solar system is a system of stars, planets and other objects that are all gravitationally bound to the Sun. In other words, the solar system includes anything that orbits the Sun because the movement of the planet balances with the gravity of the Sun to keep the objects moving around the Sun.
Our solar system consists of the Sun (a star), the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, lots of moons and millions of asteroids, comets and meteoroids.
The Universe is made up of billions of galaxies. A galaxy is a collection of dust, gas, billions of stars and their solar systems. A galaxy is held together by gravity. Galaxies can be all sorts of different shapes, sizes and colours. There are so many galaxies in the universe that we can’t even count them all yet!
The Milky Way is our galaxy. When you look at the stars at night, you are looking at the stars in the Milky Way galaxy. Scientists estimate that there are about 100 billion stars in the Milky Way. Because we are inside the Milky Way, we can’t get a picture of what it looks like from the outside, but scientists think it is a large barred spiral galaxy.
A black hole is a place in space where gravity pulls so much that even light cannot get out. Black holes are invisible because light can’t get out. A special telescope has to be used to find black holes.
Some black holes can be as tiny as an atom but have the same mass as a large mountain. Other black holes, called stellar black holes, can have a mass that is twenty times bigger than the mass of the Sun.
Not everyone agrees on what the definition of a planet should be. The most recent definition of a planet was defined in 2006 by the International Astronomical Union. It says that a planet:
Until 2006, Pluto was considered to be a planet but then its status was changed to ‘dwarf planet’. This is because it does not meet the last of the three criteria – it hasn’t cleared its neighbouring region of other objects because its gravitational force isn’t big enough.
Diameter: 4,878 km
Distance from the sun: 58 million km
Time taken to orbit the sun: 88 days
Time taken to complete one rotation: 1,408 hours
Composition: Rock and metal
Moons: No moons
Interesting facts: Mercury is the closest planet to the sun causing extremes in temperature. Temperatures can reach up to 450°C during the day and -170°C at night.
Diameter: 12,100 km
Distance from the sun: 108 million km
Time taken to orbit the sun: 225 days
Time taken to complete one rotation: 5,832 hours
Composition: Rock and metal
Moons: No moons
Interesting facts: Venus is often mistaken for a star because, after the moon, it is the brightest object in the night sky.
Diameter: 12,800 km
Distance from the sun: 150 million km
Time taken to orbit the sun: 365 days
Time taken to complete one rotation: 24 hours
Composition: Rock and metal
Moons: 1 moon
Interesting facts: Earth is the only planet in which water can exist as a liquid instead of ice or gas due to the distance from the sun.
Diameter: 6,800 km
Distance from the sun: 230 million km
Time taken to orbit the sun: 687 days
Time taken to complete one rotation: 25 hours
Composition: Rock and metal
Moons: 2 moons
Interesting facts: Mars has 24 hour days just like earth, as well as polar caps and an atmosphere. This has caused many scientists to believe that Mars could support extraterrestrial life.
Diameter: 142,980 km
Distance from the sun: 778 million km
Time taken to orbit the sun: 4332 days
Time taken to complete one rotation: 10 hours
Composition: Gas (mainly hydrogen and helium)
Moons: At least 63 known moons
Interesting facts:Jupiter is the largest planet in the solar system. It only takes 9 hours and 55 minutes for Jupiter to rotate on its axis.
Diameter: 120,535 km
Distance from the sun: 1433 million km
Time taken to orbit the sun: 10,756 days
Time taken to complete one rotation: 11 hours
Composition: Gas (mainly hydrogen)
Moons: At least 60 known moons
Interesting facts:Saturn’s rings are made up of billions of ice particles, ranging from micrometres to hundreds of metres in width. Saturn is so light it could float on water.
Diameter: 51,120 km
Distance from the sun: 2873 million km
Time taken to orbit the sun: 30,600 days
Time taken to complete one rotation: 17 hours
Composition: Ice, gas and rock
Moons: At least 27 known moons
Interesting facts:Uranus also has a series of rings which are made up of dust. Uranus is the only planet that spins on its side.
Diameter: 49,530 km
Distance from the sun: 4.5 billion km
Time taken to orbit the sun: 60,100 days
Time taken to complete one rotation: 16 hours
Composition: Gas (mainly methane which gives Neptune its blue colour)
Moons: 13 moons
Interesting facts: Neptune has the strongest winds of any of the planets. Wind speeds can reach up to 2,1OO km per hour. It is also the coldest planet.
We hope you enjoyed our space facts for KS2 children and teachers! There is so much more to find out about space. Why not see what else you can discover!
