How the James Webb Telescope’s MIRI and NIRCam are Advancing Cosmic Exploration

In the 1990s, the Hubble telescope captivated the world with breathtaking images of our beautiful universe. But even before its launch, scientists were thinking about what came next (1).

The answer? The James Webb Telescope.

Launched on Christmas Day in 2021, the James Webb Space Telescope (JWST) is the result of a collaborative effort between the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA), and the Canadian Space Agency (CSA). Unlike Hubble, which circled the Earth, the Webb telescope orbits the Sun 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point (L2) (2).

The JWST has captured the attention of the analytical chemistry community thanks to its advanced onboard instruments—the Near Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI)—which offer powerful capabilities for chemical analysis and molecular detection. Since its launch nearly four years ago, the telescope has played a pivotal role in a series of groundbreaking discoveries that have reshaped our understanding of the universe.

Macarena Garcia Marin is an astrophysicist and instrument scientist for the European Space Agency. © Macarena Garcia Marin

Spectroscopy spoke with Macarena Garcia Marin, an astrophysicist and instrument scientist for the ESA and deputy project scientist on the Webb Mission. She highlighted the role of innovative spectroscopy techniques employed by the Webb Mission in expanding our knowledge of cosmic phenomena.

Stay tuned for a special bonus episode of our Analytically Speaking Podcast featuring Garcia Marin.

The Mid-Infrared Instrument (MIRI)

MIRI on the JWST combines imaging and spectroscopic capabilities to observe light in the mid-infrared range (3). Operating between 5 and 28 microns, MIRI is designed to capture detailed views of distant galaxies, forming stars, comets, and Kuiper Belt objects by detecting faint, redshifted light. Its wide-field camera delivers stunning images, building on the visual legacy of Hubble, while its spectrograph offers medium-resolution data that reveal the physical properties of these distant cosmic targets.

“It’s like a treasure trove of spectroscopic information,” Garcia Marin said. “When it comes to spectroscopy MIRI is groundbreaking. Specifically, if you want to study chemical composition, planet-forming discs. It’s really getting so much information.”

MIRI has been instrumental in exploring distant galaxies, galaxy evolution, star formation. It has also been involved in studying supernovas. In July 2023, for example, MIRI captured images of two Type II supernovae—SN 2004et and SN 2017eaw—in the galaxy NGC 6946, about 22 million light-years away (4). These observations revealed significant amounts of dust around the supernovae, lending support to the idea that such stellar explosions were major contributors to the dust present in the early universe.

It's also been instrumental in the exploration of exoplanets, Garcia Marin said, which are planets that orbit around stars other than the sun. Last year, for example, researchers using the Webb telescope reported potentially detecting atmospheric gases around 55 Cancri e, an intensely hot rocky exoplanet located 41 light-years from Earth (5). This finding represents the strongest evidence yet for the presence of an atmosphere surrounding a rocky planet beyond our Solar System. To investigate 55 Cancri e’s potential atmosphere, researchers used NIRCam and MIRI instruments to measure infrared light between 4 and 12 microns. By comparing the system’s brightness when the planet is visible versus when it’s hidden behind the star—a technique called secondary eclipse spectroscopy—the team calculated the infrared light emitted from the planet’s day side. This approach, also used for other rocky exoplanets like TRAPPIST-1 b, helps reveal possible atmospheric features (4).

“Exoplanets weren’t even a thing before Webb was developed,” she said. “With MIRI, you see different parts of the spectra, you see different layers of the atmosphere, and different compositions of this planet.”

The Near Infrared Camera (NIRCam)

Webb’s NIRCam is its main imaging tool, capable of observing infrared light between 0.6 and 5 microns (6). It is designed to study a wide range of cosmic phenomena, from the formation of the earliest galaxies and stars to stellar populations in nearby galaxies, young stars in the Milky Way, and distant objects in the Kuiper Belt. NIRCam also includes coronagraphs, which block out the intense light of bright stars to reveal the much fainter objects around them. This feature enables astronomers to study the properties of exoplanets orbiting nearby stars.

“It’s amazingly sensitive. What you could do with another telescope in 100 hours, you can do with NIRCam in 10,” she said. “You can observe faint objects in a lot of detail. NIRCam has been groundbreaking at observing distant galaxies.”

James Webb space telescope in outer space on orbit of Earth. © dimazel - stock.adobe.com

Last year, NIRCam captured observations of the galaxy GS-NDG-9422, revealing that its light is primarily emitted by superheated gas rather than the stars themselves (7). Astronomers suspect the galaxy’s stars are so intensely hot that they energize the surrounding gas, causing it to shine even more brightly than the stars. This unexpected characteristic may represent a previously unrecognized phase of galaxy evolution within the universe’s first billion years, prompting researchers to search for other galaxies with similar features to gain deeper insights.

“With NIRCam, you can observe all of these deep fields where you can identify distant galaxies,” Garcia Marin said.

MIRI and NIRCam function like a complementary pair of instruments, said García Marín, each contributing unique insights that, together, help unravel the hidden stories of distant galaxies. “We constantly try to highlight the power spectroscopy has,” she said. “It is a very, very powerful tool. It’s our most certain way to understand astronomical objects.”

References

1. Webb Project history, Webb. Webb Space Telescope. (n.d.). https://webbtelescope.org/news/webb-science-writers-guide/webb-project-history
2. James Webb Space Telescope - NASA Science. https://science.nasa.gov/mission/webb/ (accessed 2025-04-21).
3. Mid-Infrared Instrument (MIRI) - NASA Science.
4. Dusty Supernovae (MIRI). https://webbtelescope.org/images (accessed 2025-04-21).
5. Webb Hints at Atmosphere around Rocky Exoplanet. https://www.esa.int/Science_Exploration/Space_Science/Webb/Webb_hints_at_atmosphere_around_rocky_exoplanet (accessed 2025-04-21).
6. NIRCAM - NASA Science. https://science.nasa.gov/mission/webb/nircam/ (accessed 2025-04-21).
7. In Odd Galaxy, NASA’s Webb Finds Potential Missing Link to First Stars | Webb. https://webbtelescope.org/contents/news-releases/2024/news-2024-133 (accessed 2025-04-21).