Methods of observation
Observing the sky is the basis of astronomy. Over time, researchers have developed ever more sophisticated methods to obtain information about the universe, either directly or indirectly.
Observing electromagnetic waves
Over the centuries, astronomers have developed ever better telescopes to gather information about the universe. Today, telescopes are located in observatories on Earth and travel through space on satellites. The latter can also be used to capture images of extremely distant objects such as (nascent) galaxies. The main difference between telescopes is the wavelength of electromagnetic radiation they use for observations. With the human eye, we can only detect a very limited part of the electromagnetic radiation that is present in space, namely light with wavelengths of 380 to 780 nanometres.
- Radio astronomy works with wavelengths ranging from a few millimetres to hundreds of kilometres.
- Optical astronomy works in the range of visible light from 380 to 780 nanometres.
- Infrared astronomy observes wavelengths between 700 nanometres and 300 micrometres.
- Ultraviolet astronomy observes wavelengths between 10 and 380 nanometres.
- X-ray astronomy and gamma astronomy: X-ray astronomy detects radiation with wavelengths between 10 picometres and 10nm, while gamma astronomy detects anything smaller than 10 picometres.
Researchers can only observe optical, infrared and radio waves from Earth. The Earth's atmosphere absorbs all other rays. Telescopes on satellites are required to, for example, observe ultraviolet, gamma or X-ray radiation.
Telescopes look very different, depending on the wavelength for which they are intended. While we can focus optical radiation with glass or plastic lenses, for example in a telescope, large parabolic antennas are needed for radio wavelengths. Specially arranged mirrors are required for X-rays and gamma radiation.
Examining particles
In addition to electromagnetic waves, researchers can also investigate particles that reach us from space, these being known as cosmic radiation. Cosmic radiation consists mainly of protons and electrons and individual atomic nuclei. Supernova explosions also produce cosmic neutrinos that reach the Earth.
Depending on the wavelength with which the Milky Way is mapped, we receive different information. We are most familiar with the visual representation in the centre, as it corresponds to what our eyes perceive.