Tiny bright objects discovered at dawn of universe stun scientists

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

An international team, led by Penn State researchers, using the NIRSpec instrument aboard the JWST as part of the RUBIES study, has identified three mysterious objects in the early universe, approximately 600 to 800 million years after the Big Bang , when the universe covered only 5% of the surface area. his current age. They announced the discovery today, June 27 Letters from the astrophysics journal.

The team studied spectral measurements, or intensities 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 signatures of massive supermassive black holes in the same objects, estimating them to be 100 to 1,000 times more massive than the supermassive black hole in our own Milky Way. Neither 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 confirmed that these objects appear to be full of old stars – hundreds of millions of years old – in a universe that is only 600 to 800 million years old. Remarkably, these objects hold records for the earliest signatures of ancient starlight,” said Bingjie Wang, a postdoctoral researcher at Penn State and lead author of the paper.

“It was totally unexpected to find old stars in a very young universe. The standard models of cosmology and galaxy formation have been incredibly successful, but these luminous objects don’t quite fit those theories.”

The researchers first spotted the massive objects in July 2022, when the first JWST dataset was released. The team published a paper in Nature A few months later, the objects’ existence was announced.

At the time, the researchers suspected the objects were galaxies, but continued their analysis by using spectra to better understand the objects’ true distances and the sources powering their immense light.

The researchers then used the new data to paint 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 from around 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 of both papers. “You can make this fit uneasily into our current model of the universe, but only if we conjure up an exotic, insanely fast formation at the beginning of time. This is without a doubt the most peculiar and interesting collection of objects I have seen in my career.” seen.”

The JWST is equipped with infrared sensing instruments that can detect light emitted by the oldest stars and galaxies. In essence, the telescope allows scientists to peer back in time about 13.5 billion years, near the beginning of the universe as we know it, Leja said.

One challenge when analyzing ancient light is that it can be difficult to distinguish between the types of objects that might 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 that it is not yet clear how much of the observed light comes from each of these galaxies. That means they could be early galaxies that are unexpectedly old, even more massive than our own Milky Way, and that formed much earlier than models predict. They could also be normal-mass galaxies with “overmassive” black holes, about 100 to 1,000 times more massive than such a galaxy would be today.

“It is challenging to distinguish between light from material falling into a black hole and light emitted from stars in these small, distant objects,” says Wang. “That inability to tell the difference in the current data set leaves plenty of room for interpretation of these intriguing objects. Frankly, it’s exciting to still uncover so much of this mystery.”

If some of the light does indeed come from supermassive black holes, apart from their unexplained mass and age, then they are not normal supermassive black holes either. They produce many more ultraviolet photons than expected, and similar objects studied with other instruments lack the characteristic features of supermassive black holes, such as hot dust and bright X-rays. But perhaps most surprising, the researchers said, is how enormous they appear to be.

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

The researchers were also stunned by the incredibly small size of these systems, just a few hundred light-years across, about 1,000 times smaller than our own Milky Way. The stars are about as numerous as in our own Milky Way, with somewhere between 10 billion and 1 trillion stars, but they are contained in a volume 1,000 times smaller than the Milky Way.

Leja 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 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 column of light.

“These early galaxies would be so full of stars — stars that would have formed in a way that we’ve never seen before, under conditions that we would never expect at a time when we would never expect them,” Leja said. “And for whatever reason, the universe stopped making objects like these after just a few billion years. They’re unique to the early universe.”

The researchers hope to make more observations, which they say could help explain some of the objects’ mysteries. They plan to probe deeper spectra by pointing the telescope at the objects for longer periods of time, which will help tease apart the emission from stars and the potential supermassive black hole by identifying the specific absorption signatures that would be present in each.

“There’s another way we can have a breakthrough, and that’s just 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 going to break. This problem lends itself to a stroke of genius that has eluded us, all of our collaborators, and the entire scientific community.”