Largest-ever map of the universe reveals 800,000 galaxies

In a major step toward open science, an international team of researchers has released what is now the largest and most detailed map of the universe ever created.

The project is called COSMOS-Web, and it captures nearly all of cosmic history in one expansive dataset. Created using data from the James Webb Space Telescope (JWST), the newly released map includes images and a catalog of nearly 800,000 galaxies.

The scientists behind this effort are from UC Santa Barbara and the Rochester Institute of Technology. The team has constructed a panoramic view of the universe that challenges long-standing ideas about how the earliest galaxies formed.

“Our goal was to construct this deep field of space on a physical scale that far exceeded anything that had been done before,” said Professor Caitlin Casey, who co-leads the COSMOS-Web collaboration alongside Jeyhan Kartaltepe of the Rochester Institute of Technology.

“If you had a printout of the Hubble Ultra Deep Field on a standard piece of paper, our image would be slightly larger than a 13-foot by 13-foot-wide mural, at the same depth. So it’s really strikingly large.”

Peering into the early universe

The image captures the universe as it appeared roughly 13.5 billion years ago. Given that the universe itself is about 13.8 billion years old, this map spans approximately 98% of cosmic history.

The team wanted to do more than spot distant galaxies. The goal was to place these objects within their environments. The researchers hoped to understand where and how the first stars, galaxies, and black holes formed and evolved.

“The cosmos is organized in dense regions and voids,” Casey explained. “And we wanted to go beyond finding the most distant galaxies; we wanted to get that broader context of where they lived.”

More galaxies than anyone expected

Before JWST began its observations, astronomers had made predictions based on older instruments like the Hubble Space Telescope. They thought galaxies within the first 500 million years after the Big Bang would be extremely rare.

“It makes sense – the Big Bang happens and things take time to gravitationally collapse and form, and for stars to turn on. There’s a timescale associated with that,” noted Professor Casey.

“And the big surprise is that with JWST, we see roughly 10 times more galaxies than expected at these incredible distances. We’re also seeing supermassive black holes that are not even visible with Hubble.”

“And they’re not just seeing more,” she added. “They’re seeing different types of galaxies and black holes.”

More questions than answers

The new data may be one of the most detailed views of the early universe ever made, but it doesn’t tie up loose ends. In fact, according to Professor Casey, it’s raising more questions than it answers.

“Since the telescope turned on we’ve been wondering ‘Are these JWST datasets breaking the cosmological model?'”

“Because the universe was producing too much light too early; it had only about 400 million years to form something like a billion solar masses of stars.”

“We just do not know how to make that happen. So, lots of details to unpack, and lots of unanswered questions,” said Professor Casey.

Sharing the universe map

This project marks more than just a scientific milestone – it signals a shift in how astronomy is done. By releasing the largest map of the universe and making its data public, the team hopes to spark new discoveries by astronomers worldwide.

“A big part of this project is the democratization of science and making tools and data from the best telescopes accessible to the broader community,” Casey said.

While the data was released almost immediately after collection, it was initially in raw form. That format was only useful to experts with the skills – and computing power – to process it.

Over the past two years, the COSMOS collaboration has worked to convert that raw information into accessible images and catalogs. Now, even undergraduate students and independent researchers can explore the early universe.

“Because the best science is really done when everyone thinks about the same data set differently,” Casey said. “It’s not just for one group of people to figure out the mysteries.”

Future research directions

But the exploration doesn’t end here. The COSMOS team is returning to the deep field to continue mapping and studying what lies beyond.

“We have more data collection coming up,” noted Professor Casey. “We think we have identified the earliest galaxies in the image, but we need to verify that.”

The researchers will use spectroscopy, a method that breaks light into its component colors, to determine just how far away – and how ancient – these galaxies truly are.

“As a byproduct, we’ll get to understand the interstellar chemistry in these systems through tracing nitrogen, carbon and oxygen,” said Professor Casey. “There’s a lot left to learn and we’re just beginning to scratch the surface.”

The COSMOS-Web image is available to browse interactively.

The full study was published in the journal Astrophysical Journal and Astronomy & Astrophysics.

Image Credit: ESA/ NASA/ JWST

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