One of the confounding things about astronomy is that simple dust is an obstacle that astronomers must work hard to overcome. In a Universe that contains beguiling things like supermassive black holes, amino acids on the surface of comets, and puzzling, powerful bursts of extragalactic radio waves, it’s somewhat humbling that simple dust particles require so much effort to deal with. One of the reasons the powerful JWST was built is to deal with this dust.
One of the struggles facing cosmologists who want to identify and study the Universe’s earliest galaxies is that dust can mimic redshift. Dust can make a not-so-ancient galaxy appear ancient. This is especially critical when it comes to the JWST and its science objectives. One of the reasons the space telescope was built was to peer back in time to the earliest stars and galaxies to understand how they formed.
The MINERVA (Medium-band Imaging with NIRCam to Explore ReVolutionary Astrophysics) observing program will re-examine galaxy fields already observed by the JWST, but this time in wavebands not used before. MINERVA hopes to overcome the dust problem to find rare and unusual galaxies obscured by dust in other observations. Outliers and one-offs often hold important clues.
The details of the MINERVA survey are in a new research article titled “MINERVA: A NIRCam Medium Band and MIRI Imaging Survey to Unlock the Hidden Gems of the Distant Universe.” The lead author is Adam Muzzin from York University. Danilo Marchesini, professor of physics and astronomy at Tufts, is co-principal investigator of MINERVA.
By combining MIRI observations with NIRCam observations, MINERVA will build more fine-tuned observations than either instrument can alone. These observations will uncover more dust-obscured objects.
“High-quality multi-wavelength imaging has been essential in nearly all major breakthroughs in the modern study of galaxy formation,” the authors write. “While spectroscopy remains the quintessential tool for more detailed studies of galaxies, most spectroscopic studies are pre-selected from photometric catalogs.” Multi-wavelength photometric catalogs are essential to advance our understanding of galaxies and their formation, and MINERVA will create one of these catalogs. The authors say it will facilitate “spectroscopic follow up for decades to come.”
“The idea here is to get the ultimate multi-wavelength dataset for extragalactic astronomy science,” Marchesini said in a press release. MINERVA will target four extragalactic fields already observed by JWST: UDS, COSMOS, AEGIS and GOODS-N. It will use a total of about 387 hours of observing time, some concurrently, to perform its survey. JWST observing time is in high demand, explaining why these types of datasets are rare.
This image shows the four extragalactic fields covered by MINERVA. They’ve all been observed before by the JWST, but not with the same depth. Image Credit: Muzzin et al. 2025/MINERVA
“JWST has already revealed significant populations of sources previously invisible to HST and Spitzer,” the authors write. “Some exotic objects may even be dark to NIRCam and only visible in MIRI,” they explain, emphasizing the strength of multi-wavelength observations.
With the new data they’ll be gathering “comes very precise knowledge of the properties of those galaxies and their stellar populations—the stellar mass of the galaxy, how many stars that galaxy is forming every year, and its star formation history,” Marchesini said.
The imaging in MINERVA will allow astronomers to tell the difference between emission sources. They’ll be able to differentiate between supermassive black holes, fully formed stars, and regions of intense star formation. MINERVA will also discriminate between a quiescent, quenched galaxy that isn’t forming stars, and an active star-forming galaxy that’s obscured by dust. There are other multi-wavelength datasets, but MINERVA will increase by about a factor of ten the extragalactic fields with multi-wavelength datasets for astronomers to work with.
“The area is important, because what we’re also after are rare objects,” said Marchesini. “You need to sample a larger volume of the universe to find very exciting, rare objects, especially if you go to those galaxies where they’re either the first galaxies that formed or these very exciting quiescent galaxies in the first billion years of cosmic history.”
“One of the goals of the Webb telescope is to find the first stars, the first galaxies,” Marchesini said. “With MINERVA, there’s a lot of different things that we want to find, and one is looking for very robust candidates of galaxies in the first 300 million years, or redshift above 13.”
An artist’s illustration of the first stars forming during the Cosmic Dawn. Image Credit: N.R. Fuller, National Science Foundation
This timeframe is called the Cosmic Dawn, when the first stars, galaxies, and even black holes formed. This period represents a profound transition in the Universe. Prior to the first stars, the Universe was dominated by neutral hydrogen. In the Cosmic Dawn, things transitioned from a cold, dark expanse to the star-filled Universe we see around us today.
The Cosmic Dawn planted the seeds for the galaxies and large-scale structure in the modern Universe. Examining these early Universe’s can explain how everything turned out the way it is, and can also give us important tests of our theories about the fundamental physics of the Universe, including dark energy and dark matter.
A critical part of this effort is to differentiate between highly redshifted galaxies and those that are obscured by dust. Dust-obscured light is much fainter, which mimics higher redshifts. The JWST’s powerful instruments and filters allow it to spot the difference.
MINERVA will also address one of the JWST’s puzzling finds. The space telescope made headlines when it discovered the Little Red Dots (LRD). LRDs are small, red-tinted cosmic objects that date back as early as only 600 million years after the Big Bang. While there’s much conjecture, there’s no agreement on what they actually are. The leading theory is that they’re a type of primordial galaxy that contain supermassive black holes (SMBH) and have active galactic nuclei.
One of the puzzling Little Red Dots detected by the JWST. The space telescope found 341 of them, and though there are proposed explanations for what they are, there’s no widely-held conclusion. Image Credit: Jorryt Matthee et al 2024 ApJ
“MINERVA certainly will enable us to identify little red dots in a much more robust way,” said Marchesini, “pinning down the evolution of the number density of little red dots—and of the central supermassive black hole we think are generating them. This is really important to understand how, for example, supermassive black holes grew in the universe, and how they connect with the host galaxy that they live in.”
Multiple competing theories attempt to explain SMBHs, and only more observational evidence can strengthen or weaken them. MINERVA began its effort to find answers on July 25th, and will run for about one year.
“When complete, MINERVA will become an integral part of the treasury deep field imaging datasets, significantly improving population studies with well-understood completeness, robust photometric redshifts, stellar masses, and sizes, and facilitating spectroscopic follow up for decades to come,” the authors write.