There was something surprisingly familiar about the way UCSC professor of astronomy and astrophysics Brant Robertson described galaxies in our recent interview. I’d talked with him for two previous stories as the James Webb Space Telescope launched and started sending data back to Earth. But in this particular conversation, a few phrases he used summoned an unexpected nostalgia.
He listed some of the new questions that JWST allows astronomers to ask. “What’s the diversity in the population of galaxies at these times?” and “what impact do they have on their surroundings?” were among them.
I commented that those sounded more like the topics I used to explore as an ecology student than what I would expect to hear in astronomy. He nodded with a smile.
“It’s indeed often called galaxy ecology,” he said. “Galaxies—they live and grow, and they die off, but they do so in the environment of other things.”
To understand the lives of these faraway galaxies—not simply their distance from us or their age, but the details that define them—requires incredible technical precision and power. It’s one example of how JWST is changing science, and UCSC researchers are at the forefront.
In part three of our JWST series, UCSC scientists talk about significant discoveries, changes in scientific culture and revelations to come.
TELESCOPE’S-EYE VIEW
After years of delays and uncertainty, the most powerful telescope was launched into space in December 2021. It flew to a predetermined point about a million miles from Earth and successfully unfolded its 21-foot-diameter mirror and tennis court-sized sunshield. In the year since, it spent several months calibrating four main instruments and began sending highly anticipated data back to Earth.
“Already, Webb has touched on almost every aspect of astronomy,” UCSC distinguished emeritus professor Garth Illingworth says. It changes how we see everything from the birth of ancient galaxies to planets in our own solar system.
“The telescope performs better than all the requirements we had on it,” Illingworth adds. And because of its excellent launch, it has enough fuel to operate for 20 years.
But it hasn’t all been smooth sailing. It took months of calibrating and discussions to tease out the exact sensitivity of each instrument onboard. On top of that, instrument shutdowns delayed observations and threw wrenches in schedules.
At one point in December, the entire telescope shut down, says Illingworth. Booting it back up took two days.
Sometimes the malfunctions come from cosmic rays that pass through the telescope and confuse the electronics. Other times software bugs cause the issues. Either way, the result is a scramble to make up for lost time in the tightly packed observation schedule.
Illingworth is the U.S. lead for the PRIMER program, which studies the formation of some of the earliest galaxies in the universe. Because of the instrument shutdowns, the team had a shorter window to make observations and now must wait until November to fill in the gaps.
“So, we have a map of a region of the sky with holes in it, which is very frustrating,” Illingworth says. “But that’s just the way it goes.”
Hiccups aside, he says the excitement of discoveries and seeing the universe in a new way makes it “amazingly fun” to be a scientist.
Three days after the first data was released, Illingworth and colleagues wrote a paper about a puzzling discovery. They had expected to find small, dim galaxies from early in the universe. But “there’s much more of these than expected, and they’re much brighter than expected,” says Illingworth.
Some scientists have suggested that this discovery could point to flaws in our understanding of cosmology and the early universe. Illingworth thinks it’s more likely that we just don’t understand the galaxies’ formation. Others suggest that the galaxies might not be as old or far away as proposed.
“We shall see,” Illingworth says.
AT THE EDGE OF THE UNIVERSE
Light from the earliest galaxies travels billions of light-years across an expanding universe before it reaches our solar system. When it touches our solar system, the wavelengths have stretched into the infrared in a phenomenon called redshift. Infrared light is outside the range we can see, but JWST’s instruments are designed for it.
One of the instruments, called the near-infrared spectrograph (NIRSpec), works like a prism, spreading out light and allowing researchers to study the individual colors in light from stars and galaxies. This technique, called spectroscopy, helps scientists more accurately measure the distance of galaxies. In November, Robertson and an international team, JWST Advanced Deep Extragalactic Survey (JADES), used spectroscopy with four of the oldest-known galaxies. The paper is currently under consideration for peer review.
Two galaxies were known from Hubble Telescope data, and two were newly discovered using JWST.
“Those two turned out to be the two most distant galaxies that we know about,” says Robertson. Other faraway galaxies have been found, but their distances have not yet been confirmed with spectroscopy.
The distance and timescale are impossible to grasp. The light has traveled for 13.5 billion years before reaching us, meaning these galaxies existed in the universe’s infancy, less than 400 million years after the Big Bang.
These early galaxies behave very differently than our Milky Way. They’re around a thousand times smaller in the area but only about a hundred times smaller in mass.
“The density—how much stuff you fit into a small space—actually controls the timescale on which things happen,” says Robertson. “So, it’s like the clock is running faster in some ways in these galaxies.”
For example, scientists believe that galaxies form stars about a hundred times quicker relative to their mass than the Milky Way.
To better understand these earliest galaxies, researchers need more examples. With hundreds of hours of assured telescope time in their future, the JADES team expects to have plenty more to study soon.
“We’re just getting started,” says Robertson.
THE SEARCH FOR HABITABLE PLANETS
While sensitive enough to see the galaxies at the edge of the visible universe, JWST is also “powerful enough to see the tiniest molecules in the smallest planets very close to us,” says UCSC professor of astronomy and astrophysics Natalie Batalha.
Batalha leads the Transiting Exoplanet Community Early Release Science Program. The group, made up of around 300 scientists from around the world, studies the atmospheres of planets outside our solar system.
Most scientists don’t expect JWST to be able to detect life, but learning about exoplanet atmospheres provides a starting point for studying their habitability.
UCSC is at the forefront of this research. The Astrobiology Initiative, directed by Batalha, is an interdisciplinary effort to study the origins and distribution of life in the universe. UCSC also draws visiting astronomers over the summer for the Other Worlds Laboratory (OWL).
When a planet passes in front of its star, some of the starlight filters through the atmosphere before reaching the telescope, Batalha explains. By observing a star before, during and after a planet crosses in front of it, scientists can measure changes in the light. Using spectroscopy, they can then identify molecules in the atmosphere of the planet that absorb light at specific wavelengths.
“When you’re trying to observe an exoplanet atmosphere, you’re trying to tease out a small number of photons from the star that have been affected by the atmosphere,” Batalha says. “And for that, you need really, really high precision.”
In August, the team published findings of carbon dioxide in the atmosphere of WASP-39 b, a Saturn-mass planet that orbits a star about 700 light-years from Earth. Data from Hubble had hinted at the presence of CO2; this was the first confirmation of it in an exoplanet atmosphere.
In the same planetary spectrum, the researchers found sulfur dioxide, the same gas responsible for the smell of burnt matches.
“It was pretty shocking,” says fourth-year Ph.D. student Nicholas Scarsdale. Scarsdale models the atmospheres of exoplanets and then matches those models to the spectra.
The presence of sulfur dioxide excited scientists because it forms through photochemistry—chemical reactions influenced by light.
“The ozone in the upper atmosphere that protects us from ultraviolet radiation is actually produced by photochemistry,” Batalha says.
It means the atmosphere is not in equilibrium. Scarsdale says that so-called disequilibrium processes are widespread in the universe but not as common in models because of their complexity.
“Life is a disequilibrium process,” he continues. “At equilibrium, we are dust in the wind.”
Scarsdale says that photochemistry is particularly interesting; all Earth life relies on it through photosynthesis.
WASP-39 b is a “hot Jupiter” and not considered habitable, but it can still offer clues about how stars influence their planets’ atmospheres.
“A lot of the planets that we think of as being in the habitable zone have very different stars from our own,” he says. “So, understanding what that different light profile does to the chemistry in their atmospheres is really important for understanding whether they’re habitable at all.”
A STARRY-EYED FUTURE
WASP-39 b is one of three exoplanets the early release science program is studying. The other two are WASP-18 and WASP-43. All three are bigger than the class of planets Batalha and Scarsdale are most excited to study: sub-Neptunes and super-Earths. These planets are ubiquitous in the Milky Way, but we don’t have one in our solar system.
“I want to know if any subset of those planets represents new real estate for the possibility of life,” says Batalha. She’s working with her daughter, NASA astronomer Natasha Batalha, to study those planets and expects to get back the first observations in the next two weeks.
UCSC also led the process of imaging an exoplanet using JWST. Aarynn Carter, a postdoctoral scholar who works with UCSC professor of astronomy and astrobiology Andrew Skemer, spearheaded the data analysis for imaging exoplanet HIP-65426 b.
“I’ve spent the last five years preparing for these observations, and seeing them not only succeed but exceed expectations is exhilarating,” Carter said in a press release. “I think what’s most exciting is that we’ve only just begun.”
With two decades of spectacular images and discoveries ahead of us, the stars are aligning for a new age of astronomy.
