7.5 - 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.

Light pollution, air pollution and siting

Ground-based telescopes are limited by two main factors:

1. Light pollution - Artificial light from street lamps and buildings makes faint objects hard to see.
2. Air pollution - Pollutants reflect and absorb light coming from space.

Getting the best view from the ground

• Place the telescope on top of a mountain, where there's less atmosphere above it.
• Place it in a dark location far from cities to minimise light pollution.