James Webb Space Telescope's infrared sensors will mark a major step in astronomy

Webb is about to unlock the redshifted depths of the ancient universe.
Brad Bergan
Webb, in a composite image with Jupiter.Paopano / iStock

The power of what you can't see.

Since the universe formed, it's expanded at an increasing rate, leaving the most distant parts of the universe incredibly difficult to see — leaving much of the universe hidden from the human eye.

But it's there, and could hide the lion's share of secrets of our universe. And, with the James Webb Space Telescope nearing its first science missions — a colossal survey across a 13-billion-year span of universal history, the telescope's infrared capabilities will be crucial.

And a recent video from the European Space Agency (ESA) demonstrates how Webb will reveal new depths of the universe, bringing galaxies that formed at the very dawn of our universe to the initial conditions for life beyond Earth, as stellar waste is pulled together into new planets around young stars.

With the James Webb Telescope, the possibilities are truly limitless.

Webb can explore the depths of the redshifted universe

The visible universe is illuminated by ordinary light — a sliver of energy on the electromagnetic spectrum. But infrared light reveals the heat of the cosmos, and has longer wavelengths than visible light. While the legendary Hubble Space Telescope can detect some infrared and ultraviolet light, it was made for the visible spectrum.

Webb, however, was optimized for the infrared spectrum.

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And this enables the new telescope orbiting beyond Earth at the Lagrange 2 point to pierce unseen vastness of deep time, with unprecedented resolution. This is a crucial tool to study our universe because it's expanding — with more distant galaxies moving farther away at a greater velocity than the ones that are closer. The farther galaxies away are, the more shifted into longer, redder wavelengths they appear.

Redshift is a bit like hearing the siren of a fire truck race by, in a phenomenon of sound called the Doppler effect. Only for electromagnetic radiation, in space.

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Cosmological Redshift
A diagram that depicts the universe's expansion over time, and thus the "stretching out" of wavelengths, and redshift itself. Source: VectorMine / iStock

The James Webb Telescope will unveil the infrared universe

And, critical to Webb's survey of the cosmic infrared spectrum is its Mid-Infrared Instrument (MIRI). "Webb's [MIRI] is special — in the wavelengths it covers, the science it enables, its [technological] challenges, and in the way it was built," said Professor George Rieke of astronomy at the University of Arizona, in conjunction with Director Gillian Wright of the U.K. Astronomy Centre, in a NASA blog post.

"With the other three instruments, Webb observes wavelengths up to 5 microns," they added. "Adding wavelengths out to 28.5 microns with MIRI really increases its range of science. This includes everything from studying protostars and their surrounding protoplanetary disks, the energy balance of exoplanets, mass loss from evolved stars, circumnuclear tori around the central black holes in active galactic nuclei, and a lot more."

There's much to see at the mid-infrared wavelengths, according to the two scientists. "Since anything at room temperature emits mid-infrared light, infrared astronomers working with ground-based telescopes peer through the huge foreground infrared emission of the telescope and atmosphere," they said. "With perseverance, some interesting mid-infrared results have been obtained from ground-based telescopes, but the limitations are severe."

In other words, up until now, the very conditions of life on Earth have prevented astronomers from exploring the full extent of the universe, but Webb will change all of that.

Webb's exploration of our universe will deepen our grasp of the Local Group

"Dramatic results in the mid-infrared have come from telescopes in the vacuum of space, where they are cooled to cryogenic temperatures to eliminate their emission [of heat] and are clear of Earth's atmosphere," added the scientists. Several technical challenges are presented from this. For example, the telescope needed to be kept clear of ice pre-launch.

But all the efforts were worth it.

Mapping the Local Group - "Webb is built on a scale approaching the largest telescopes on the ground, and it will be cold enough to provide the full potential for the mid-infrared," said the scientists. "The sensitivity gains and the image clarity will both be nearly a factor of 100 better than ever before." Of course, the exploration of the unseen universe starts with building a better picture of the local universe — which means the Local Group, a collective of three primary galaxies: our Milky Way, Andromeda, and Triangulum, in addition to roughly 50 dwarf galaxies. Images of that alone will rapidly expand our grasp of the cosmos, but in the long run for the James Webb Space Telescope, it's merely the beginning.