- Technology & Science
- Kenneth P. Dietrich School of Arts and Sciences
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Update: Since this story was published, the James Webb Space Telescope successfully launched, unfolded and traveled to its destination about 930,000 miles from Earth.
On Dec. 22, NASA will launch into space the successor to its Hubble telescope, a highly sensitive and astronomically expensive tool capable of seeing objects that are farther and fainter than ever before. It’ll unfold its 21-foot mirror and in a few months will begin beaming down the first of many captivating images, along with data that will keep scientists busy for years to come.
At least, that’s what Pitt astronomers hope. Four are among the researchers who have been granted highly sought-after time using the telescope in its first year in operation.
“It’s kind of a Hail Mary, but it’s a super exciting one,” said Physics and Astronomy Assistant Professor Rachel Bezanson in the Kenneth P. Dietrich School of Arts and Sciences. “This has been a very, very long time coming.”
The astronomy community has been waiting for NASA’s James Webb Space Telescope for decades, and Bezanson is more invested than most.
The project she co-leads, which she compares to the Hubble “deep field” program that produced arguably the telescope’s most iconic image, will point the Webb telescope at a particular patch of space for 30 hours, creating what a photographer might recognize as long-exposure shots of distant galaxies. What would make less sense to that photographer is that Bezanson’s team will look for faint, distant objects in a part of the sky area littered with close, bright galaxies.
“A huge collection of mass warps space so much that the light that travels through that space gets bent like a lens,” Bezanson said. “So we’re basically using that foreground collection of mass to boost the brightness of the things behind it and see even fainter objects than we otherwise would.”
Along with managing the project, Bezanson and her team at Pitt will transform the data delivered by the telescope into a form that’s usable for scientists. The images that emerge from that data will be one of the farthest glimpses Webb will reveal in its first year.
“We’re going to have the best chance of finding the most distant, craziest objects,” Bezanson said. As for what those objects will be? “Let’s be totally honest, we have no idea: We have never probed anything in these wavelengths at this kind of resolution before. We just haven’t had any kind of comparable tool.”
Searching for galactic winds
Before the telescope can start looking for galaxies, it has to launch into space. And that’s just the beginning of its precarious journey: Unlike its predecessor, Webb will revolve around Earth in an orbit so distant that it can’t be serviced by astronauts.
“There are 344 single-point failures,” Bezanson said — as in, 344 different ways the mission could go wrong. “It’s not just in the launch; it has to unfurl five layers of thin films the size of a tennis court.”
But that complexity, along with its distance from Earth and size, is what will lend Webb an unprecedented power and sensitivity to see far-away objects.
Its other superpower is the kind of light it can detect.
In the same way that an ambulance’s siren sounds deeper as it drives away, distant celestial objects look more red than they actually are because the space between them and the Earth is expanding. This effect is even more dramatic for the farthest objects: By the time their light reaches Earth, it’s been stretched past the red part of the light spectrum and into the infrared, invisible to the naked eye. Webb is designed to detect those infrared waves — and because the light from those distant objects has spent billions of years traveling to us, the new telescope will be able to show us regions of space as they existed when the universe was young.
That’s an especially exciting prospect to Evan Schneider, an assistant professor in Pitt’s Department of Physics and Astronomy. “The Milky Way is sort of a nice stable disc; it’s puttering along making one star every year,” she said. “But at much earlier cosmic epochs, everything was way more dramatic.”
The project Schneider is a part of, led by Susan Kassin of the Space Telescope Science Institute, will use Webb to study these early galaxies. Schneider, an expert on the theory of how galaxies evolve over time, is particularly interested in the gas that galaxies shoot out early in their evolution, a feature called galactic winds.
In the past few decades, Schneider said, researchers have come to believe that as galaxies form they constantly shoot out gas due to the force of exploding stars. Armed with both Webb’s power to peer into the early universe and its ability to tease apart light waves into their component parts, researchers will be able to tell how much gas the galaxies were ejecting in their early days. That should let them confirm whether their recent theorizing has been on the right track.
“We think that in really early times, everything was much more chaotic — all of this bursty star formation and feedback was going on,” Schneider said. “But we haven't been able to actually measure these things at early times, because you need a telescope like James Webb to do it.”
‘At the mercy of these exploding stars’
Rather than staring deeply at one patch of space, Department of Physics and Astronomy Associate Professor Carles Badenes is part of a project that will sneak in minutes throughout the telescope’s first year. There’s a simple reason for that: They don’t yet know where they’ll need to look.
“A typical supernova explodes in a matter of seconds, and then half a year later, the supernova has faded quite a bit. That is when you want to catch them,” Badenes said.
Badenes studies a poorly understood process that happens when cooled-off stars known as white dwarves explode. By the time one of these explosions has dimmed, it has also spread out enough that a telescope can peer right through it, giving them the moniker “see-through supernova.”
It’s blink-and-you’ll-miss-it astronomy, and a unique chance for scientists to see the inner workings of a stellar phenomenon. Wielding Webb’s ability to split apart light waves, Badenes and his colleagues, led by Saurabh Jha at Rutgers University, will be able to understand the chemical composition of these exploding stars. They’ll even be able to measure how quickly supernovae eject material into their surroundings.
“We know these are exploding white dwarves of some kind, but we don’t understand exactly the why and exactly the how,” Badenes said. Webb will give them a chance to answer those questions. Hopefully.
“We’re all at the mercy of these exploding stars,” Badenes said. “They have to go off. If they don’t, then no luck.”
Other programs in Webb’s first year are less concerned with specific phenomena and more aimed at getting as much mileage out of the telescope as possible — like PRIMER, a project that includes Department of Physics and Astronomy Professor Jeffrey Newman.
“The strategy for PRIMER is to cover as much sky as we can,” Newman said.
One problem with staring into an unknown part of space is that the patch of sky you choose might just be a dud. “If you look at a small area of the universe, you may be lucky or unlucky,” Newman said. “That region may have been a high-density part of the universe or low-density part of the universe.”
Newman’s role in PRIMER is to help determine how best to use Webb, minimizing the chance that they’ll find nothing at all of interest. They’ll look to collect data on a broad cross-section of early galaxies in many different wavelengths of light across two patches of sky. The search will provide a bigger picture of how galaxies looked a when the universe was much younger.
And as researchers pore through the resulting information, they’ll find intriguing objects to follow up on later. “But first, we need to find the interesting ones,” Newman said. “PRIMER is really intended to be the discovery engine that allows us to do that.”
Projects like Bezanson’s and Newman’s are poised to produce so much data that the team’s researchers couldn’t possibly analyze it all themselves. It’s one of the many extremes of science that researchers are pushed to, due to the competitive nature of applications for time with Webb. All are large teams with painstakingly economical plans for using the telescope’s precious minutes, and generous plans for making their data available to the public.
If you want a crack at a state-of-the-art telescope, there’s no room for hoarding what you find.
“This is in the DNA of astrophysics: We share our tools,” said Bezanson. “I’m really interested to see what some other group will do with the same dataset, because the way they ask the questions is inevitably going to be different. That combination gives you a rich understanding.”
And the projects Pitt scientists are a part of are only a fraction of the science that will happen in the telescope’s first year. Making sense of what Webb beams back to Earth will be a global effort — and one that won’t stop anytime soon.
“These things have longevity because there are just a million questions you can ask once you have lots of imaging,” Bezanson said. “This will set the field up for decades.”
— Patrick Monahan