Small, bright objects discovered at the dawn of the universe baffle scientists

A recent discovery by NASA’s James Webb Space Telescope (JWST) confirmed that bright, very red objects previously discovered in the early universe overturn conventional thinking about the origin and evolution of galaxies and black holes. their supermassive.

An international team, led by Penn State researchers, using the NIRSpec instrument aboard JWST as part of the RUBIES survey, identified three mysterious objects in the early universe, about 600-800 million years after the Big Bang, when the universe was only 5 % of her actual age. They announced the discovery today on June 27 at Astrophysical Journal Letters.

The team studied spectral measurements, or the intensity of different wavelengths of light emitted by the objects. Their analysis found signatures of “old” stars, hundreds of millions of years old, much older than expected in a young universe.

The researchers said they were also surprised to discover signs of large supermassive black holes in the same objects, estimating that they are 100 to 1,000 times more massive than the supermassive black hole in our own Milky Way. Neither of these is expected in current models of galaxy growth and supermassive black hole formation, which expect galaxies and their black holes to grow together over billions of years of cosmic history.

“We have confirmed that these appear to be filled with ancient stars – hundreds of millions of years old – in a universe that is only 600-800 million years old. Amazingly, these objects hold the record for the earliest signs of light from old of the stars.” said Bingjie Wang, a postdoctoral researcher at Penn State and lead author on the paper.

“It was completely unexpected to find old stars in a very young universe. Standard models of cosmology and galaxy formation have been remarkably successful, however, these bright objects don’t quite fit into those theories.”

Researchers first discovered the massive objects in July 2022, when initial data was released by JWST. The team published a paper in Nature a few months later announcing the existence of the objects.

At the time, researchers suspected the objects were galaxies, but followed up their analysis by taking spectra to better understand the objects’ true distances, as well as the sources powering their immense light.

The researchers then used the new data to draw a clearer picture of what the galaxies looked like and what was inside them. Not only did the team confirm that the objects were indeed galaxies near the beginning of time, but they also found evidence of surprisingly large supermassive black holes and a surprisingly old population of stars.

“It’s very confusing,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State and co-author on both papers. “You can make this fit uncomfortably into our current model of the universe, but only if we conjure up an exotic, extremely fast formation at the beginning of time. This is, without a doubt, the most unique and interesting group of objects that I have seen in my career”.

JWST is equipped with instruments with infrared sensors capable of detecting light that has been emitted by the most ancient stars and galaxies. Essentially, the telescope allows scientists to look back in time roughly 13.5 billion years, near the beginning of the universe as we know it, Leja said.

One challenge to analyzing ancient light is that it can be difficult to distinguish between the types of objects that may have emitted the light. In the case of these early objects, they have clear characteristics of both supermassive black holes and old stars.

However, Wang explained, it’s not yet clear how much of the observed light comes from each — meaning these could be early galaxies that are unexpectedly old and more massive than even our own Milky Way, forming much earlier than the models predict, or they could be more normal-mass galaxies with “supermassive” black holes, roughly 100 to 1000 times more massive than such a galaxy would be today.

“Distinguishing between light from material falling into a black hole and light emitted by stars in these small, distant objects is challenging,” Wang said. “This inability to tell the difference in the current data set leaves ample room for interpretation of these intriguing objects. Honestly, it’s exciting to have so much of this mystery to figure out.”

In addition to their inexplicable mass and age, if some of the light is indeed from supermassive black holes, then they are also not normal supermassive black holes. They produce far more ultraviolet photons than expected, and similar objects studied with other instruments lack the hallmarks of supermassive black holes, such as hot dust and bright X-ray emission. But perhaps most surprising, the researchers said , is how massive they look.

“Normally, supermassive black holes pair up with galaxies,” Leja said. “They grow up together and go through all their major life experiences together. But here, we have a fully-formed adult black hole living inside what should be a baby galaxy. It doesn’t really make sense , because these things should grow together, or so we thought.”

Researchers were also puzzled by the extremely small size of these systems, only a few hundred light-years across, roughly 1,000 times smaller than our own Milky Way. The stars are roughly as numerous as our own Milky Way galaxy—somewhere between 10 billion and 1 trillion stars—but contained within a volume 1,000 times smaller than the Milky Way.

Leah explained that if you took the Milky Way and compressed it to the size of the galaxies they found, the nearest star would be almost in our own solar system. The supermassive black hole at the center of the Milky Way, about 26,000 light-years away, would be only about 26 light-years from Earth and visible in the sky as a giant pillar of light.

“These early galaxies would be so dense with stars—stars that must have formed in a way we’ve never seen before, under conditions we’d never expect over a period in which we’d never expect never see them,” Leja said. “And for whatever reason, the universe stopped creating objects like these after only a few billion years. They are unique to the early universe.”

The researchers hope to follow up with more observations, which they said could help explain some of the objects’ mysteries. They plan to obtain deeper spectra by pointing the telescope at the objects over long periods of time, which will help disentangle the emission from stars and potential supermassive black holes by identifying specific absorption signatures that would be present in each of them.

“There is another way we can have a breakthrough and this is the right idea,” Leja said. “We have all these pieces of the puzzle, and they only fit if we ignore the fact that some of them are breaking down. This problem lends itself to a stroke of genius that has so far eluded us, all our collaborators, and the entire scientific community .”