Two Northeastern researchers helped with a massive effort to pierce into the furthest reaches of the universe and turn back the clock, revealing images of when the universe was just a toddler.
A newly released survey from the COSMOS-Web project provides the biggest ever window into the deepest parts of our universe, including detailed views of almost 800,000 galaxies and a look at the universe when it was essentially a toddler.
The COSMOS-Web is an ongoing survey that makes use of NASA’s ultra-powerful James Webb Space Telescope to peer deep into the earliest days of the universe and see how galaxies form over time. COSMOS2025, the project’s most recent release of publicly available data, is the result of dozens of scientists spending hundreds of hours working with the James Webb Space Telescope’s images. It offers the clearest and largest glimpse of how galaxies like our Milky Way formed.
“There’s a very rich variety of galaxies out there in the universe –– some like our Milky Way, some a little larger, most much smaller –– and they change over cosmic time,” says Jacqueline McCleary, an assistant professor of physics at Northeastern University who assisted on the survey. “They’re not fixed: They grow, they evolve, they die. This process is complicated and mysterious, and the COSMOS project was an attempt to get a handle on this.”
The advanced instruments of the James Webb Space Telescope, which uses the infrared wavelength to spot farther objects, helped COSMOS-Web capture a broader range of galactic history in this survey. The project uncovered a few hundred galaxies that correspond to when the universe was only a few hundred million years old, or less than 4% of its current age.
McCleary says these are, essentially, toddler photos of the universe.
“Imagine having a movie of galaxies from infancy to the modern day,” McCleary says. “The COSMOS-Web grants us this continuous picture.”
The work done by the COSMOS-Web team involved processing about 10,000 images taken by the JWST’s camera and stitching them together into one continuous field of space. Scientists were then able to use that information to figure out things like the distances between galaxies, types and shapes of galaxies, how quickly stars formed, and the age and size of galaxies and stars in the field.
Those results are not just relevant for people studying galaxy evolution but general astronomers as well, McCleary explains.
“Getting a handle on distances to galaxies is one of the most important and challenging pursuits in astronomy, and the COSMOS field offers this information for now 800,000 galaxies, which is incredible,” McCleary says.
McCleary and the other Northeastern collaborator on the project, Eddie Berman, a researcher with the Northeastern University Cosmology Group, helped by mitigating a blurring effect on the telescope’s optics known as point spread function.
Point spread function is a universal quality of all telescope optics. When light passes through a telescope’s mirrors and optics, it creates a diffraction pattern, obscuring the true shape of a galaxy or star.
“The mirrors of the James Webb Space Telescope have this hexagonal tiling pattern, so you can see in an image a sort of footprint or watermark of the camera that took it by looking at the star PSF,” Berman says. “Is [a galaxy] elliptical? Is it spiraling? Is there a bulge in the middle of the galaxy? These are all details we could miss if we don’t properly account for the PSF.”
There are a variety of software tools that help astronomers model point spread function that generally use stars as signposts in the sky. However, Berman developed his own model that was capable of capturing point spread function for a large field of view both quickly and intuitively.
The work done by McCleary, Berman and the rest of COSMOS-Web’s massive team is not only significant in its own right as a window into galactic history. It will also be foundational for countless other astronomical surveys, McCleary says. The high-quality measurements and high-resolution images in COSMOS2025 will inevitably be used to calibrate and train other attempts to model galaxy shapes and distances.
“This data product allows any astronomer, really any person –– it’s not limited to scientists –– to use this catalog to calibrate their own galaxy distance … estimates, to do their own galaxy evolution science, to do cosmology, which is a project Ed and I and some collaborators at Northeastern have been working on,” McCleary says. “Anything you want, it’s yours for the taking.”