New Zealand astronomers use different wavelengths of light to reveal information about stars and galaxies and to find new planets.

This resource provides explanations of the key concepts encountered when exploring our Solar System and the work by astronomers – the ‘basics’ that every student should understand.


A ball of gas that creates heat and light by nuclear reactions. Stars look different, depending on such things as their size, temperature and age.


A ball of rock or gas that orbits the Sun and has cleared the neighbourhood around its orbit. Planets do not make their own light.

Extrasolar planet

A planet in orbit around a star other than our Sun. Extrasolar planets are too far away to know what shape they are, or if they have cleared space around them.

Solar System

The Sun (a star) and everything orbiting it, including planets and their moons, dwarf planets, asteroids and comets.


A collection of stars, gas and dust held together by gravity. Our Solar System is in the Milky Way galaxy. Galaxies can have many billions of stars.

Galaxy cluster

A large collection of galaxies held together by gravity. The galaxies are surrounded by hot gas.

Galaxy group

A small collection of galaxies. Our Milky Way galaxy is in a Local Group with the Andromeda galaxy and several smaller ones, including the Large and Small Magellenic Clouds.

Optical telescope

An instrument to magnify and collect light from the visible part of the electromagnetic spectrum. Optical telescopes use mirrors or lenses to focus the light from distant objects.

X-ray telescope

An instrument that magnifies and collects light from the X-ray part of the electromagnetic spectrum. Most X-ray telescopes are placed in orbit, because X-rays cannot get through the Earth’s atmosphere.

UV telescope

An astronomical tool for magnifying and collecting ultraviolet radiation from hot objects in space.

Radio telescope

An instrument that uses a ‘dish’ to collect and focus radio waves from stars and galaxies. The dishes need to be large, because radio waves are the longest and weakest in the electromagnetic spectrum.

    Published 1 April 2009