Observing the Universe

A spectrum containing dark lines where specific wavelengths have been absorbed by a cooler gas.

The average distance between the Earth and the Sun (about 150 million kilometres).

A spectrum containing all wavelengths without interruption.

An optical device that separates light into its component wavelengths.

The complete range of electromagnetic radiation, arranged by wavelength or frequency.

A spectrum containing bright lines produced by excited atoms or ions.

A massive collection of stars, gas, dust, planets, and dark matter held together by gravity.

A group of galaxies bound together by gravity.

The highest-energy electromagnetic waves with the shortest wavelengths.

Electromagnetic radiation with wavelengths longer than visible light, often emitted by cooler objects.