The European Space Agency (ESA) is Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Find out more about space activities in our 23 Member States, and understand how ESA works together with their national agencies, institutions and organisations.
Exploring our Solar System and unlocking the secrets of the Universe
Go to topicProtecting life and infrastructure on Earth and in orbit
Go to topicUsing space to benefit citizens and meet future challenges on Earth
Go to topicMaking space accessible and developing the technologies for the future
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Absorption Spectra: When light passes through a gas, atoms and molecules in the gas absorb certain colors, or wavelengths, of that light. The result is an absorption spectrum: a rainbow with dark absorption lines.
Emission Spectra: The same gas can glow, giving off very specific colors to form an emission spectrum with bright lines known as emission lines.
Every element has a unique set of absorption and emission lines. The pattern of lines is known as a spectral signature. The absorption and emission spectra of each element are inverses of each other: The wavelengths of a particular element’s absorption lines are the same as the wavelengths of its emission lines. Astronomers can compare the spectrum of a celestial object or material with the spectra of known elements and molecules to figure out what the object or material is made of.