How James Webb Will Study Distant Galaxies

As the James Webb team continues step four of mirror alignment, the team continues to check other instruments onboard. This includes the NIRSpec instrument, which will allow James Webb to see the earliest galaxies in the universe, including some of the first stars created after the Big Bang.

Visible vs infrared light photos. The heat from stars behind the Eagle Nebula can be seen in infrared but is absorbed and blocked by the gas and clouds in visible light images. Credit: NASA/Hubble

Since the Big Bang, everything in the universe has been rapidly expanding away from each other. You can think of this as being like raisins in a loaf of bread while it's baking. As the loaf rises, the space between the raisins increases. This is true for nearly all galaxies. As a result of this rapid expansion of the universe, galaxies moving away from us appear to be redshifted.

Redshifting is a process you are already familiar with, whether you realize it or not. If you’ve ever been driving while an emergency vehicle passes, then you’ve probably noticed how to sound changes as passes. This is because of the Doppler Effect. As the emergency vehicle passes, it takes longer for each sound wave to reach your ears. The redshifting process is similar, but with the electromagnetic spectrum. As galaxies move away from us, it takes longer for the light to reach us, stretching out the light wavelengths from our perspective.