The James Webb Space Telescope (JWST), scheduled to launch in 2021, is billed as the successor to the Hubble Space Telescope. Unlike Hubble, which orbited Earth, the JWST will orbit the Sun at a distance of roughly 1.5 million kilometers from the Earth, a location known as the second Lagrange point (L2). This position has the benefit of minimizing thermal radiation noise from the Earth and the Sun, allowing the JWST to operate at much lower temperatures, critical for observing infrared radiation.

The JWST is designed primarily for infrared observations, a significant departure from Hubble’s focus on optical and ultraviolet observations. Infrared radiation has much longer wavelengths than visible light, so the JWST can peer through cosmic dust to regions that are hidden from Hubble’s gaze.

One of the most exciting scientific objectives of the JWST is to study the earliest galaxies that formed in the Universe.

According to the current understanding of the Universe, the first galaxies formed during a period known as the cosmic dawn, which occurred around 1 billion years after the Big Bang. These early galaxies are incredibly faint, and so far, only a few have been detected by Hubble. The JWST will be able to detect these galaxies much more easily, and it is expected to discover a vast population of these objects.

Studying these early galaxies will provide valuable insights into the early Universe. For example, the JWST will be able to measure the star formation rates in these galaxies and determine how they evolve over time. It will also be able to study the chemical composition of these galaxies and learn about the first stars that formed in the Universe.

The JWST is a hugely ambitious project, and its construction and launch were beset by many delays and cost overruns. However, if it can successfully overcome these challenges, it promises to revolutionize our understanding of the early Universe and provide insights into the birth and evolution of the first galaxies.

Here are some specific examples of the science that the JWST will be able to do regarding early galaxies:

1. Detect the first stars: The JWST will be able to detect the first stars that formed in the Universe, which are expected to have been extremely massive and luminous. These stars may have been responsible for the reionization of the Universe, which is thought to have occurred around 400,000 years after the Big Bang.

2. Study the formation of the first galaxies: The JWST will be able to study how the first galaxies formed and evolved over time. It will be able to measure the growth of these galaxies and determine the processes that drove their formation. The JWST will also be able to study the interactions between galaxies and how they merge together to form larger structures.

3. Learn about the chemical composition of the early Universe: The JWST will be able to study the chemical composition of the early Universe by measuring the abundance of different elements in the first stars and galaxies. This information will help us understand how the elements were formed and how they were distributed throughout the Universe.

4. Search for signs of life beyond Earth: The JWST will be able to search for signs of life beyond Earth by studying the atmospheres of planets orbiting other stars. It will be able to detect molecules in these atmospheres that are essential for life, such as water, oxygen, and methane. The JWST will also be able to search for exoplanets in the habitable zones of their stars, where liquid water could exist on the surface.