How do deep-field surveys show the early stages of galaxy evolution?

Deep-field surveys, such as those conducted by the Hubble Space Telescope, allow astronomers to observe the universe as it existed billions of years ago. Because light takes time to travel across space, these surveys capture images of galaxies when they were in their infancy, only a few hundred million years old.1

These observations reveal a universe significantly different from the present day. Instead of the large, structured spiral galaxies or elliptical galaxies seen in the local universe, early deep-field images show small, irregular objects that served as the fundamental building blocks for larger galaxies.1

Key insights from these surveys include:
* Galaxy Growth: Evidence suggests that galaxies evolved through the merger and accretion of these smaller, irregular fragments.1
* Star Formation: Early galaxies often exhibit high rates of star formation, characterized by an abundance of excited hydrogen and young, hot stars.1
* Chemical Composition: Stars in these early systems are often deficient in heavy elements, as those elements had not yet been synthesized in significant quantities.1

Modern observatories, such as the James Webb Space Telescope, continue this work by detecting infrared light, which is essential for observing the very first galaxies that formed after the big bang.2