2.6 - Observing the Universe
Observing from above the atmosphere
- Earth's atmosphere absorbs a lot of the electromagnetic radiation coming from space, so some wavelengths never reach telescopes on the ground, as the graph below shows.
- Placing a telescope on a satellite in space avoids the atmosphere entirely.
- Telescopes in space receive radiation that would otherwise be absorbed, giving a clearer view and more accurate measurements of distant astronomical objects.
Grey shows the wavelengths the atmosphere absorbs; the coloured gaps reach the ground.
Observing across the whole spectrum
- Visible light is only one part of the electromagnetic spectrum.
- Different astronomical objects emit and reflect radiation in different parts of the spectrum, and many can't be detected in visible light at all.
- To build a complete picture of the Universe, astronomers use a range of telescopes that cover the entire electromagnetic spectrum.