Astronomical spectroscopy is used to measure three major bands of radiation in the electromagnetic … See more

Newton used a prism to split white light into a spectrum of color, and Fraunhofer's high-quality prisms allowed scientists to see dark lines of an unknown origin. In the 1850s, Gustav Kirchhoff and Robert Bunsen described t… See more

The spectra of galaxies look similar to stellar spectra, as they consist of the combined light of billions of stars.
Doppler shift studies of galaxy clusters by Fritz Zwicky in 1937 found that the galaxies in a cluster … See more

The interstellar medium is matter that occupies the space between star systems in a galaxy. 99% of this matter is gaseous – hydrogen, helium, and smaller quantities of other ionized elements such as oxygen. The other 1% is … See more

Stars and interstellar gas are bound by gravity to form galaxies, and groups of galaxies can be bound by gravity in galaxy clusters. With the exception of stars in the Milky Way and the galaxies in the Local Group, … See more

Planets, asteroids, and comets all reflect light from their parent stars and emit their own light. For cooler objects, including Solar System planets and asteroids, most of the emission is at infrared wavelengths we cannot see… See more