Key learning points

1. Telescopes extended what was visible after their invention in the seventeenth century.
2. Images detected by telescopes in space are not distorted by effects of the Earth’s atmosphere.
3. A galaxy is a group of hundreds of billions of stars, and there are many galaxies spread across the universe.
4. A visible spectrum of light emitted from stars or galaxies shows dark lines of frequencies of light.
5. Red shift is the movement of hydrogen lines towards the red end of the visible spectrum.

Common misconception

Keywords

• Space telescope - is a telescope positioned in space to avoid atmospheric interference and observe parts of the spectrum which cannot reach the Earth’s surface

• Galaxy - is a collection of many millions or billions of stars held together by gravitational forces

• Redshift - is the increase in the wavelength of light (and decrease in its frequency) cause by the movement of a star or galaxy away from us