Explore the sky
Four starting points for exploring the universe. Where figures could vary or are hard to be sure of, they are left out.
The Solar System
The Solar System is the Sun and everything held in orbit around it by its gravity.
- The Sun: a star that holds most of the Solar System's mass and provides its light and heat.
- Rocky planets: Mercury, Venus, Earth and Mars, the four planets closest to the Sun.
- Gas and ice giants: Jupiter and Saturn are gas giants; Uranus and Neptune are ice giants.
- Smaller bodies: moons, dwarf planets such as Pluto, asteroids and comets.
Earth has one natural satellite, the Moon.
Stars
A star is a huge, hot ball of gas that shines because nuclear fusion in its core releases energy. Stars differ in size, brightness and colour; hotter stars look bluer and cooler stars look redder.
Stars form in clouds of gas and dust, shine for a very long time, and eventually change as their fuel runs low. How a star ends depends mainly on how massive it is.
Galaxies
A galaxy is a huge system of stars, gas, dust and dark matter held together by gravity. The Sun is one of a very large number of stars in the Milky Way galaxy. Galaxies come in different shapes, including spirals and ellipticals, and there are many galaxies beyond our own.
How to start stargazing
- Find a dark spot: get away from bright lights and let your eyes adjust for several minutes.
- Start with your eyes: you can see the Moon, bright planets and many stars without any equipment.
- Learn a few constellations: patterns of stars are a handy way to find your way around the sky.
- Use a star chart or app: it shows what is above you tonight.
- Try binoculars: they show far more than the unaided eye and are easier to use than a telescope at first.
- Never look at the Sun through binoculars, a telescope or with your eyes. It can cause permanent eye damage.