The universe is expanding faster than we thought, Webb Space Telescope shows
Jun 5, 2024

The universe is expanding faster than we thought, Webb Space Telescope shows

Astrophysicist Adam Riess and his team at Johns Hopkins University have been using data from the Hubble and Webb space telescopes to study the behavior of our universe and satisfy humanity's curiosity.

NASA’s Hubble Space Telescope has been exploring the cosmos for the past three decades, helping scientists understand how fast the universe is expanding and with that, its age. In December 2021, NASA launched the James Webb Space Telescope to further that research. The bonus: All those stunning images from outer space.

Marketplace’s Lily Jamali spoke with Adam Riess, a physicist at Johns Hopkins University who shared the 2011 Nobel Prize in physics. He said the Webb telescope has confirmed what Hubble first pieced together: Our universe is expanding faster than first predicted.

The following is an edited transcript of their conversation.

Adam Riess smiles wearing a blue collared shirt and a black suit jacket.
Adam Riess (Courtesy Johns Hopkins University)

Adam Riess: We’ve completed several studies using JWST’s enhanced resolution and sensitivity to pick out pulsating stars to gauge the present expansion rate of the universe, the same way a ship captain would look at a lighthouse from their ship to gauge their distance from the rocky shore and make sure they’re far enough away. Now, these new measurements are confirming those made with the Hubble Space Telescope. Simply put, the universe appears to be expanding faster than we would have expected based on the way it started and the physics of its composition, the physics of the universe. Now, most of that composition is in pretty mysterious forms: dark matter and dark energy, which make up 96% of the universe and whose physics we don’t fully understand. So, in this case, surprises may not be that surprising, after all.

Lily Jamali: And dark matter was one of the main things you focused on in your research that ultimately won you the Nobel Prize, if I’m understanding it correctly.

Riess: It was actually dark energy.

Jamali: Dark energy. Tell me the difference, why don’t we start there?

Riess: So, dark matter is, as the name says, matter that probably clumps, but it doesn’t emit light. So it may be a different kind of particle. Dark energy is more mysterious. It kind of looks like a background energy in the deep parts of space. It’s everywhere, even between galaxies. And it seems to be accelerating the expansion of the universe, which was a big surprise and something that we struggle to understand to this day.

Jamali: And talk to me about the technology that’s in these telescopes, first Hubble and now the James Webb Space Telescope, that’s expanded our understanding of what’s going on in the universe. How does the tech work there?

Riess: The main technology, I would say, is just being above the atmosphere of the Earth. So when we look out in space, it’s sort of like, if you’ve ever sat at the bottom of a pool and looked out at things, everything looks swimmy and blurry. And that is, in our case, caused by the turbulence in the atmosphere, when we look out from telescopes on the ground. So by putting telescopes like Hubble and JWST above the blurring effects, we get crystalline, sharp images. So that’s already pretty fantastic. And so the Hubble Space Telescope gave us pristine views over the last few decades. Now, JWST takes that even further, both because it’s a much bigger telescope, so it allows us to collect fainter light. It’s also a very cold telescope, which is important because we are looking at very faint, distant objects. And so if the telescope itself had any heat, the glow of the telescope would produce a kind of a noise or background that would make it difficult to see those distant objects. And this, sort of, is the, the main superpowers, I would say, of JWST that is allowing us to see farther and with this kind of razor-sharp precision.

At the center of these side-by-side images is a special class of star used as a milepost marker for measuring the universe’s rate of expansion — a Cepheid variable star. The two images are very pixelated because they are a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the universe’s expansion rate and age. (Courtesy NASA, ESA, CSA, STScI, Adam Riess (JHU, STScI))

Jamali: And the James Webb Space Telescope, when it first launched, you came on our show and said it would be a tool “to help look back into the beginning of time.” So, a couple years in now, what have you learned from looking into the cosmic past?

Riess: Right. So it is a kind of a time machine. And as all telescopes are time machines, this one is allowing us to go further back. And so it is allowing us to test our models and our understanding, and happy to say the universe is exceeding our expectations, both the rate at which it is forming complex structures in the universe and in our case, the thing I studied, the rate at which it expands. Now, I would caution people that these are early days for JWST, we’re only in the second year of data collecting. If you look at this same point in time in the history of the Hubble Space Telescope, the best was yet to come. And that will certainly be the case for JWST. But the good news is it’s operating better than expected. It has fuel for decades. And I would say, overall, it’s a really good time to be an astronomer.

Jamali: And what are some other cosmic riddles that we can expect the James Webb Space Telescope can help solve, or what are you most excited about when it comes to these next few years?

Riess: So a whole other area that’s quite fascinating is the study of exoplanets. And that is already underway with JWST, and it’s beginning to reveal the composition of the atmospheres of exoplanets. These are planets well outside our solar system, but these are planets that are orbiting other stars. And these are the baby steps that humanity is really taking on our quest to find evidence of life elsewhere. So we are looking for kind of chemical disequilibrium in these atmospheres that could provide evidence of organic compounds, plants, animals, things like that. And as I said, these are baby steps right now, but that is the process that’s underway with JWST right now.

Jamali: I love how you keep coming back to this analogy of “like a child, like the precocious child, baby steps.”

Riess: I mean, when you look at us, we are these creatures sitting on this pale, blue dot, as we say, the third rock from the sun. And it’s remarkable that we can build these facilities and study something as vast and as sort of old and … timeless as the universe itself. I think we are like the ultimate children with a kind of fascination to know what’s out there. And it’s remarkable that in this time period, we are really sort of opening our most powerful eyes to come to understand what is out there. And I think it’s just been through the tremendous ingenuity and efforts of engineers and NASA and our humanity’s curiosity that provides the resources to do this.

Jamali: And I think the response we saw on social media when the James Webb Space Telescope first started bringing back pictures, beaming back pictures to us, reflected just how much interest there is in the mainstream, and I think we needed that, actually.

Riess: I think so. You know, I think when we’re kids many of us become fascinated by dinosaurs and space. And space is something that we keep learning about at a tremendous clip. And I think for many of us, we never really lose that fascination that we have about space. And so it’s really a privilege and honor to be able to bring these pictures to the world, to really see what’s out there at sort of unprecedented high definition.

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The team

Daisy Palacios Senior Producer
Daniel Shin Producer
Jesús Alvarado Associate Producer
Rosie Hughes Assistant Producer