Images taken with the MIRI infrared camera on the James Webb Space Telescope (JWST) have made it possible to observe the first galaxies in long-wavelength infrared light for the first time. Alongside a recent study published in Astronomy and Astrophysics, these images provide new insights into how the first galaxies formed over 13 billion years ago.
“In the images, we can see the most distant galaxies known to us,” says Göran Östlin, Professor of Astronomy at Stockholm University's Department of Astronomy.
In the study, the research team present their observations of the Hubble Ultra Deep Field (HUDF), the area of the sky that has been observed most frequently by various telescopes, including Hubble and James Webb in space and ground-based telescopes such as VLT and ALMA.
“What is unique about our observations is that they are made in mid-wavelength infrared light and with an extremely long exposure time, close to 100 hours. This allows us to study extremely distant galaxies. They emitted their light more than 13 billion years ago, near the beginning of the universe,” says Göran Östlin.
Closer to the Big Bang
MIRI observations of the first galaxies make it possible to understand how and when their stars formed. Previous observations have only measured the light of newborn stars in these galaxies.
“With MIRI, we can estimate the number of stars that formed even earlier, near the Big Bang. This gives us the opportunity to study how the first galaxies evolved in the early days of the universe,” says Jens Melinder, a researcher in the Department of Astronomy at Stockholm University.
Elements and black holes
Using mid-infrared light, the research team can also study dusty galaxies, some of which contain black holes. These dust-rich galaxies contain large amounts of interstellar dust that absorb blue light from the stars. The light that escapes from these galaxies and reaches us is infrared light.
“MIRI allows us to see through the veil of dust and observe what lies behind. By observing this type of galaxy, we can understand how quickly the heavier elements that the dust is made from formed in the early universe, and how supermassive black holes, surrounded by a ring of hot dust, evolved," says Jens Melinder.
New images and data available
The publication makes all images and measurements available for researchers worldwide to download and use.
“We have contributed brand new data that will be used in future by researchers studying galaxy evolution and the formation of the first galaxies. The HUDF is such an incredibly well-observed part of the night sky that there is great value in making our images available. We expect them to be used by many,” says Jens Melinder.
Facts
- Due to the expansion of the universe, light from distant galaxies is increasingly redshifted. The most distant galaxies known to us were discovered using NIRCam at JWST. These galaxies emit mostly ultraviolet light from newly formed stars, but due to the redshift, JWST and NIRCam are required to detect them in infrared light. MIRI observes longer-wavelength infrared light and allows us to see visible (green-red) light from the galaxies. This makes it possible to measure light from slightly older stars in galaxies.
- Interstellar dust consists of small grains of grit (about 0.1–0.5 micrometres in diameter) that form in material ejected by dying stars and mix with the surrounding gas.
About MIRI
MIRI is a camera and spectrograph co-developed by astronomers at Stockholm University and Chalmers that observes mid- to long-wave infrared radiation from 5 to 28 micrometres. It also features coronagraphs designed specifically for observing exoplanets.
Read more
Find the article, ”MIRI Deep Imaging Survey (MIDIS) of the Hubble Ultra Deep Field: Survey description and early results for the galaxy population detected at 5.6 μm”, in Astronomy and Astrophysics:
https://www.aanda.org/articles/aa/full_html/2025/04/aa51723-24/aa51723-24.html
DOI: 10.1051/0004-6361/202451723
Find the images for downloading:
https://esawebb.org/images/potm2507a/
Research at JWST
The observations are taken as part of the guaranteed time (GTO) allocated to European institutions involved in constructing MIRI by the European Space Agency (ESA). Studies of the most distant galaxies in the universe use some of this time and are carried out by the international research team, the European Consortium for MIRI (EC-MIRI)/MIRI Deep Imaging Survey. At Stockholm University, the research is conducted by Göran Östlin (project leader), Jens Melinder and Arjan Bik, who are all part of the Galaxies group at the Department of Astronomy.
Read more about the research in the Galaxy Group at Stockholm University:
https://www.su.se/english/research/research-groups/the-galaxy-group
Learn more about JWST:
https://esawebb.org
https://webbtelescope.org/home