The James Webb Telescope will help unlock the evolution of habitable worlds

In star systems less than 100,000 years old.
Brad Bergan
An artist's impression of Webb in space (left), and a rendering of a protoplanetary disk (right).1, 2

If you want to understand the evolution of planets, it helps to spot them young.

The alignment of the James Webb Space Telescope's near-infrared instruments entered its "chilling" stage of the Mid-InraRed Instrument (MIRI) — where it will continue to become colder until its temperature drops to less than 7 kelvins (-447 degrees Fahrenheit).

While the scientific world anxiously awaits Webb's initial study of the first stars and galaxies of the early universe, there's more to expect beyond these benchmarks: Webb will also explore the Milky Way — specifically, where planets and stars come into being.

As our picture of the galaxy grows deeper, so will our understanding of how Earth-like planets form — and, perhaps, even alien life.

James Webb could detect stars less than 100,000 years old

"In the first year of science operations, we expect Webb to write entirely new chapters in the history of our origins — the formation of stars and planets," said Webb Project Scientist Klaus Pontoppidan of the Space Telescope Science Institute, in a press release from NASA's Goddard Space Flight Center.

"It is the study of star and planet formation with Webb that allows us to connect observations of mature exoplanets to their birth environments, and our solar system to its own origins," added Pontoppidan. "Webb's infrared capabilities are ideal for revealing how stars and planets form for three reasons: Infrared light is great at seeing through obscuring dust, it picks up the heat signatures of young stars and planets, and it reveals the presence of important chemical compounds, such as water and organic chemistry."

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Pontoppidan emphasized how commonly scientists speak about infrared light passing through dust (which obscures it). "In fact, mid-infrared light, as seen by MIRI, can pass through 20 times thicker clouds than visible light," he explained. Since young stars form in a short cosmic timespan — sometimes as few as 100,000 years — "their natal clouds have not had time to disperse, hiding what is going on in this critical stage from visible view."

And Webb's capabilities to observe the infrared spectrum will enable scientists to study precisely these "natal" stages of solar systems; when gas and dust are "actively collapsing to form new stars," said Pontoppidan.

Protoplanetary Disk Spectrum
A simulated spectrum from MIRI of a protoplanetary disk. Source: NASA / STSscl.

Webb's infrared instrument can reveal the evolution of new stars and planets

"The second reason has to do with the young stars and giant planets themselves," added Pontoppidan. "Both begin their lives as large, puffy structures that contract over time." It's known that young stars grow hotter as they begin to mature, while giant planets cool down — but this means they both "emit more light in the infrared than at visible wavelengths."

And this puts Webb in an ideal position to detect new young stars and planets, while also unlocking the key features of the beginnings of their evolution. "Previous infrared observatories, like the Spitzer Space Telescope, used similar techniques for the nearest star-forming clusters, but Webb will discover new young stars across the galaxy, the Magellanic Clouds, and beyond," said Pontoppidan.

As MIRI continues its cool-down process, scientists continue to prepare for the great discoveries that await, once it is put to the test. Beyond studying the commonalities in early star and planet formation, MIRI may only need one trace of waste heat from another world, to confirm a sign of alien intelligence.

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