Probing the first stars and galaxies: Herschel's Science Goals

Herschel's mirror deployed in space. (Credit: European Space Agency/AOES Medialab)

Artistic Image of the Herschel Space Observatory

Artist's illustration of the Herschel Space Observatory (Credit: European Space Agency - D. Ducros, 2009)

Herschel was equipped with a 3.5-metres mirror, the largest ever made for a space telescope. With its giant eye, Herschel explored so-called stellar nurseries-regions of space where stars are born-to see how they develop. Since the gases inside these molecular clouds are very dense and opaque, it is impossible to peer into them using visible light. Herschel was able to detect very faint infrared radiation to provide astronomers with more information about the stages leading up to the birth of a star.

Herschel explored how the first galaxies formed and evolved into their present state. It investigated how stars are created and their interaction with the interstellar medium. It observed the chemical composition of comets, as well as the atmospheres and surfaces of planets and satellites, and examined the molecular chemistry of the Universe.

What is infrared light?

Infrared light is a type of light that is not visible to the naked eye. It is very useful to astronomers because it gives them precious information on the amount of heat produced by an object. That means that scientists have access to information that would otherwise be hidden. For example, if you look at the following infrared images of the dog and caterpillar, you can see that the dog is a warm-blooded animal (warm colours indicate heat) while the cold-blooded caterpillar is blue next to the warm hand of the person holding it.

Thanks to infrared light, astronomers can investigate stars, galaxies, and other celestial bodies by peaking through dust clouds and other molecules, which would otherwise obstruct their vision. The pictures shown above show the same image seen in visible light (left) and in infrared light (right). The hand of the person is hidden in visible light, but it is revealed with the infrared light.