What will the JWST teach us about galaxies? What were the first sources of light in the Universe, and how and when did galaxies like our own Milky Way form?
Origin and evolution of galaxies
We are on the threshold of being able to see the first luminous objects in the Universe. For the first time in human history we have the opportunity to investigate the origin of galaxies directly.
The term 'Dark Ages' is used to describe the epoch shortly after the beginning of the Universe between the time when the microwave background radiation was emitted and the period when stars and galaxies became common.
This period lasted some 1-2 billion years, but the first objects to illuminate the darkness are too faint to be detected by present day telescopes.
One of the main strengths of the JWST lies in its ability to probe the infrared region of the spectrum with exquisite sensitivity. This will enable it to see further than optical telescopes and catch the feeble, redshifted light from the most distant objects.
The first stars not only lit up a dark Universe, but produced the chemical elements necessary for the formation of planets and, ultimately, for the very existence of life.
The JWST will also enable scientists to face another important problem related to black holes. We know from the nearby Universe that most galaxies host a giant black hole at their core that represents about 1% of their total mass. These black holes cause spectacular phenomena, observable over many different wavelengths from radio waves to X-rays.
However, we do not yet know how these black holes came to be and how their formation is linked to the formation and evolution of stars within galaxies. The JWST will help us to determine what the first galaxies were like.