These red dots could change everything we think we know about how galaxies form

As It Happens6:17These red dots could change everything we think we know about how galaxies form

Scientists have peered billions of years into the past and discovered something that could fundamentally change what we think we know about how galaxies form.

Images from the James Webb Space Telescope (JWST) show six bright red dots, which are believed to be distant galaxies as they would have appeared more than 13 billion years ago.

But if they are indeed galaxies, then they are unlike any galaxies that scientists have previously observed. That's because they're impossibly large and dense for their relatively young age.

"The first thing I said was, 'There's no way that's right. That's insane,'" astronomer Katherine Suess told As It Happens host Nil Köksal.

Suess, a cosmology fellow at Stanford University and UC Santa Cruz, is one of the authors of a study describing the discovery, which was published last week in the journal Nature.

What is a galaxy and how is it formed?

A galaxy is a collection of gas, dust, dark matter, stars and their solar systems, all held together by gravity. According to NASA, most are between 10 billion and 13.6 billion years old.

Because light takes time to travel from one place to another, telescope images are snapshots of the past. These mysterious red dots were photographed as they would have appeared about 500 to 700 million years after the Big Bang created the universe 13.8 billion years ago.

And yet, already, they have mass and density far beyond what scientists thought possible in that timeframe — rivalling our own Milky Way, which is believed to 13.6 billion years old, not much younger than the universe itself.

That flies in the face of how scientists believed galaxies formed in the early universe, Suess says.

"So there's the Big Bang, which is the beginning of everything — you know. It's the beginning of all of space, all of time, all of matter, all of energy. And then we think it takes some amount of time for things to grow. You know, so galaxies have to gobble up all of this gas and form it into stars before we can see them," she said.

"And we thought this process took billions of years. But instead we found this huge galaxy less than 500 million years after the Big Bang — which sounds like a lot, but it's like only three per cent of the total age of the universe. So it's really, really fast."

One of these potential galaxies has an equivalent mass as our Milky Way galaxy does today.

"I have a two-year-old nephew, so it's like if I went to go wake my nephew up from a nap, and instead of being my two-year-old nephew, he was like 40," Suess said. "It's not what you think you're going to find."

Is this the real deal? Only time will tell

Canadian extragalactic astronomer Sarah Gallagher, who was not involved in the research, says the findings are "intriguing," but also "something that needs to be checked out."

In order to confirm their findings, the researchers will use spectroscopy data — an in-depth look at the absorption and emission of light — which will give a better picture of what these red dots really are made of, as well as how old and large they really are.

It's possible that these red dots aren't galaxies at all, but rather some other source of light like a supermassive black hole or a quasar, the researchers say.

Or it's possible, says Gallagher, that they are galaxies, but the scientists made some incorrect assumptions about them — for example, the mass of the stars that are emitting the light.

"The thing is, a galaxy in the very early universe is not at all like a galaxy like our Milky Way today," said Gallagher, the director of Western University's institute for Earth and Space Exploration in London, Ont.

"We have a very good understanding of how galaxies like our Milky Way form stars and evolve over time. But we don't really know what those very, very young galaxies were like."

But the other possibility, says Gallagher, is that these are, indeed, massive baby galaxies, and the universe simply works differently than we had assumed.

"It just means that basically we thought we understood the story of how galaxies form in the early universe, and we were wrong. And you know what? That's pretty cool," she said.

"I mean, that's why you put telescopes like James Webb out there, because you don't know the answer to these questions. And so we'll have to change our understanding."

In that case, Suess says, it means the Milky Way isn't the only way.

"Our Milky Way probably formed much later in the universe, and so we thought that was standard. But it turns out that some things can really form extremely, extremely quickly," she said. "It implies that there's this really large diversity of ways that galaxies can grow."

If there's anything we've learned since JWST launched in December 2021, it's that there's a lot we still don't know.

"With this new telescope, we've opened this whole new view into the distant universe. And it's the very first time we can look at these earliest aspects of the cosmos in this much detail," she said.

"I think right now it's basically the most exciting time in extragalactic astronomy since the launch of Hubble more than 30 years ago. And so, you know, I think the next couple of years will be filled with discoveries like this."