Imagine swirling your hands through the heavens as if the cosmos were water, sifting through the secrets of space: luminous massive stars, red dwarfs, dark matter, supernovas, and wondrous grains of interstellar dust.

Swarthmore’s scholars led, and are leading, explorations that continue to change what we know about … everything.

An ethereal formation erupting against a canvas of glittering light, the Eagle Nebula photograph that hangs in the home of Nancy Grace Roman ’46, H’76 is a reminder she helped build a doorway to the universe. The image was captured by the Hubble Space Telescope. Roman, who once studied the stars from Sproul Observatory, is lauded as the “Mother of Hubble.”

As NASA’s first chief of astronomy in the Office of Space Science, Roman was integral in bringing Hubble to life, then to space.

Early in her career, many scientists scoffed at the idea: “They didn’t think you could learn anything from a satellite that you couldn’t learn from the ground.”

Her love of space began early. Roman’s father was a scientist, her mother an amateur stargazer. By elementary school, Roman had started her own astronomy club. When she reached Swarthmore, she took courses by astronomy professor Peter van de Kamp before going on to work at Yerkes Observatory at the University of Chicago. There, she knew she had discovered something important with her study of low dispersion spectra of bright stars.

“I noticed that, compared to the strength of the hydrogen lines, the strengths of the lines of other elements varied from star to star,” says Roman.

When she divided the stars into two groups accordingly, she detected that the stars with stronger lines moved around the center of the Milky Way in circular orbits, similar to the sun.

“The others tended to move in more elliptical orbits and to stray farther from the plane of the galaxy,” she says. “This was the first indication that common stars were not all the same age. These other elements are made in stars and hence increase in abundance as stars die.”

One of many of Swarthmore’s legendary space scientists including astronomer Sarah Lippincott Zimmerman ’42, M’50; astrophysicist Sandra Moore Faber ’66, H’86; and professor of physics Janet Conrad ’85, Roman is so culturally significant that Lego created a figure in her honor, part of a Women of NASA collection that also includes Sally Ride ’72. (Upon its release in November, the set rocketed to No. 1 as Amazon’s best-selling toy and quickly sold out.)

After more than two decades of management at NASA—and having an asteroid, 2516 Roman, named after her—she continues to advocate for young women in the sciences and stays on top of emerging research.

“There’s always an amount of wonder,” says Roman. “Dark energy is a source of energy we don’t even fully understand. We keep discovering things that people never expected to find.”

Stowaways to Other Worlds

In those discoveries, some of what we do find and haul back to Earth—or unintentionally leave behind—poses a potential threat to humanity … and beyond.

The Outer Space Treaty of 1967 created a legal obligation to avoid the harmful contamination of other worlds, says Christopher Chyba ’82, H’03, professor of astrophysical sciences and international affairs at Princeton University. One danger, he says, is viable microorganisms hitching a ride inside our robotic spacecraft.

“There is no question that many of these can survive years freeze-dried in space,” says Chyba. “Were they to reach another world with its own indigenous biosphere, there is a small chance that our stowaways could then contaminate—or even overwhelm—that alien biosphere.”

Taking caution adds cost and potentially slows the pace of exploration, but he believes it’s worth it.

“I’ve always taken preventing forward-contamination seriously,” says Chyba. “It’s the price of admission. It’s why NASA sent the Cassini spacecraft into Saturn’s atmosphere to burn up, to be sure that it could never inadvertently crash-land on the moon Enceladus, which has an ocean of liquid water—and possibly life.”

The search for extraterrestrial life has long fascinated Chyba, although most of his research now is on nuclear and biological weapons arms-control policy. While he was an associate professor at Stanford University, he also held the 

Carl Sagan Chair for the Study of Life in the Universe at the SETI Institute in Mountain View, Calif., a private research group devoted to the study of extraterrestrial life. There are at least three ways to look for it.

“You could land on another world’s surface or fly through its erupting geysers, and directly sample what’s there,” says Chyba. “This is challenging for reasons of payload mass, expense, and engineering, but also because the surface environments are quite harsh.”

Another option would be surveying the atmospheric makeup of planets orbiting other stars.

“We may find biosignatures to make a circumstantial case for life on this or that world,” Chyba says, such as finding molecular oxygen together with methane in the atmosphere, just like on our planet. “We’re only beginning these kinds of atmospheric observations for Earth-sized exoplanets, and it’s going to get much better with new telescopes.”

A third option is searching for signs of technology detectable across interstellar distances, an avenue that doesn’t require any assumptions about biochemistry, he says, but does require the tremendous assumption of the evolution of technical intelligence.

It will likely be a long search, but Chyba’s focused first on detection within our own solar system,“where, if we are lucky, we may find something like microbial life,” he says.

Root of the Tree of Life

Among the 100 billion planets or more in the Milky Way, many will be Earth-like with a similar chemical composition, says Aaron Goldman ’03, assistant professor of biology at Oberlin College. He hopes his work will give astronomers a clearer view of whether life might exist there.

“Understanding how life emerged on Earth can give us a better idea about where else and how often life has originated in our solar system and galaxy,” says Goldman, who developed LUCApedia, a framework for studying the Last Universal Common Ancestor (LUCA) and its predecessors. The database has changed the way research is being done because, beforehand, there was no system of classification for the genomic content of ancient life.

Studying the features of an organism that existed around 3.5–4 billion years ago has presented many surprises.

“Even though this ancestor represents a very ancient form of life, research shows that it was not a simple or primitive one,” he says. “They were strikingly complex with a fully operational genetic code,” including a cellular membrane and many of the elaborate processes seen in organisms today.

Despite his interest in the potential for life beyond Earth, Goldman knows it’s unlikely we will be able to visit these planets any time soon.

“But in the near future, we may be able to examine the chemistry of their atmospheres,” he says. “There are so many more potentially habitable planets and moons in the galaxy than in our solar system that I think this astronomical approach is our best chance of finding extraterrestrial life.”

Bending the Light

She watched the stars and wondered how the planets spun. Space held an early fascination for astrophysicist Jennifer Yee ’07, who nurtured her love of it with two fixed habits. Her father regularly called her outside to look up at streaking comets and brilliant meteor showers.

“And we also watched a lot of Star Trek together,” she says.

At the Harvard-Smithsonian Center for Astrophysics, Yee searches for planets by microlensing, or looking for the effect of their gravity on the light of distant, unrelated stars. With her research team, she’s discovered more than 20 planets and was awarded a Sagan Exoplanet Postdoctoral Fellowship by NASA.

One of her most exhilarating discoveries happened on July 4, 2011. (A true Swarthmorean scholar, Yee had canceled holiday plans because of a very promising microlensing event.) As observations were recorded in Chile, Yee downloaded and analyzed the images.

“I had expected that the star would be getting slowly brighter as a function of time, but I actually saw that it was rapidly getting fainter,” she says. “It was so exciting. That

was the moment when I knew it was possible we would detect a new planet.”

Yee and all the researchers were in luck when her team showed there was indeed a planet, five times the mass of Jupiter, orbiting a star similar to the sun, at a distance similar to that of the Earth.     

The biggest challenge of her research is that microlensing is difficult to detect. Identifying an “event” is a one-in-a-million chance—the lens star has to be nearly perfectly aligned with the background star in order to detect the lensing effect, and timing is critical.

Yee is also working to understand how planetary systems are constructed.

“Jupiter-sized planets can be found at all separations orbiting other stars,” she says. “With transits, we’ve seen systems with five or six Earth-to-Neptune-sized planets, in which the outermost planet is only just beyond the orbit of Mercury, but we have a limited knowledge of what kinds of planets exist on wider orbits.

“Over the next decade, we can expect microlensing to tell us what’s out there at Jupiter-like distances.”

Mining the Dust Streams

Planets, all the rage in contemporary astronomy, came into existence because tiny bits of dust stuck together and grew into planetesimals. The story of that dust, which exists in the space between the stars, turns out to hold mysteries.

Bruce Draine ’69, a Princeton professor of astrophysical sciences, never expected that interstellar dust would become his life’s work.

“When my new supervisor at Cornell assigned me to work on it, I initially thought it seemed uninteresting,” says Draine, who received his Ph.D. there in 1977. “But, in retrospect, I’m very glad he did.”

Turns out, there are many ways to study interstellar dust.

“Faraway dust dims and reddens the light from distant stars, and the starlight energy absorbed by the dust is reradiated in the infrared,” says Draine.

Both the dimming of the starlight and the energy radiated in the infrared can be studied using telescopes in space, or on the ground. 

“This allows us to try to figure out what the dust must be like, but it would be wonderful if we could get some actual samples to study in the laboratory,” says Draine.

In 2006, NASA’s spacecraft Stardust brought back space-debris samples for scientists to study firsthand.

“When the collection panel was exposed, it could also collect interplanetary dust, or particles that came from comets and collisions between asteroids,” he says. “Stardust collected three particles they identified as interstellar, but my own view on this is that those particles are unlikely to have been so.”

There were four microcraters in the collection panel’s frame with residues that could be analyzed spectroscopically, Draine says—except the particles that made the microcraters were destroyed in the impact.

“It’s not easy to capture interstellar grains!” he says. “Some from the time of formation of the solar system ended up trapped in material that arrives at the Earth as meteorites, and these grains-inside-meteorites have interesting stories to tell.”

These stories are significant at the cosmic level, but they’re also important on a more personal level.

“To be human is to be curious,” says Draine. “The 20th century was the first time that human beings figured out how big and how old the universe is, and what it contains. I feel fortunate to be alive in this era. It’s crucial that our civilization keep its eyes open, and keep asking questions.”

Though he can’t say exactly what the next news will be, Draine is sure of a stream of discoveries to come.

“The universe will continue to surprise us,” he says, “as long as we keep looking.”

Carrier of the Word

Part of searching is knowing where to begin. Even though it happened 13.8 billion years ago, John Mather ’68, H’94 desperately wants more people to know the truth about the Big Bang.

“The name ‘Big Bang’ conjures up an image of a giant firecracker,” he says, “which is the exact opposite of the way the universe is behaving.”

He should know—Mather measured it and was awarded the 2006 Nobel Prize in Physics for his work on the Cosmic Background Explorer (COBE) satellite with George Smoot of the University of California, Berkeley. In measuring the pattern of radiation that came from the early universe, their work has been so vital to the study of life and space that astrophysicist Stephen Hawking described it as “the most important scientific discovery of the century, if not of all time.”

“We learned how to do it together,” says Mather. “We measured the cosmic microwave background far better than we had dared to hope.”

He did so by successfully bringing a difficult and innovative satellite project to completion while working with a NASA engineering team.

In addition, Mather’s groundbreaking research on the James Webb Space Telescope (JWST) will give the world views of the universe that could never have been imagined.

“Working with a different NASA engineering team in partnership with the European and Canadian Space Agencies, many aerospace contractors, and an international science team, we are near to completing an even more challenging telescope that will serve all astronomers everywhere, and enable unimagined discoveries,” he says. Mather is as fascinated with relativity and quantum mechanics as he was 50 years ago.

“Now it seems that there may be new ways of looking at them,” he says.

The son of a scientist, he’d been a devoted student since he was a boy in rural New Jersey. At Swarthmore, he excelled at physics.

“Physics dealt with the greatest mysteries known to man,” says Mather, who continues to find true pleasure with each new discovery and the knowledge shared.

“We began it with COBE, but now there’s ‘precision cosmology’ and a standard model of the universe with seven numbers to describe everything,” Mather says. “I never guessed it would happen. I’m still astonished at the power of the idea, the word. None of us knew how to build the COBE satellite when we proposed it; none of us knew how to build the JWST when we proposed it, either. But the objectives were inspiring, and brilliant engineers came from everywhere to contribute. It’s not so personal as it might seem, and I see my role as a carrier of the word.”

Sky the Color of Wine

Linda Vu ’19’s life took an exciting turn the moment she started looking up. “I have the keys to the telescope,” she says, patting her pocket on a walk toward the Science Center. Vu studies the stars at Swarthmore using state-of-the-art equipment in the van de Kamp Observatory. The key-holding responsibility is daunting, but under the guidance of astronomy professor David Cohen, Vu’s getting more comfortable with it. As a child in Washington, D.C., stargazing was limited—light pollution hid the stars.

“Where I live,” she says, “the night sky is the color of red wine.”

Vu had planned to be a writer, not a scientist. She didn’t start wondering about space until high school, where teachers made biology beautiful and astrobiology even more so. 

“This idea of life on other worlds is really cool,” she says, having grown to love astronomy so much that, in her spare time, she analyzes data on exoplanets.

“When I first met Linda,” says Cohen, “she wanted to know about an astrobiology course at Swarthmore, which we don’t have—yet. I offered her a position on our exoplanet research team. Since then, she has been a careful and skilled researcher and leader.” 

For Swarthmorians, the tradition of asking hard questions and breaking boundaries continues today, he says.“We fill a niche in providing real and meaningful research with experiential learning and these are skills that will transfer after our students leave,” says Cohen.

His own research includes studying massive stars. “I’ve always thought massive stars are interesting in their own right -- but since the advent of gravitational wave astronomy in the last couple of years, massive stars have new relevance as the precursor to the black hole binary systems whose mergers generate the strongest gravitational wave signals,” he says. 

Amy Vollmer, Isaac H. Clothier Jr. Professor of Biology, is also a mentor to Vu. “Linda is an extremely thoughtful student and her passion for astrobiology is inspiring,” says Vollmer, who will host her in a lab for her honors thesis research.

Planetary protection is just one urgent question on Vu’s mind. “It's not discussed very much, however, if we're planning to do more space exploration and develop space tourism, we should start questioning the possible repercussions of human impact on space environments.”

Other what-ifs on her list include waste management on space tourism ships.

“It's not a farfetched idea considering how much pollution humans have caused on Earth,” she says. Vu wonders if space litter could take down satellites in collisions, fall back into the Earth and disintegrate into toxic particles in the atmosphere or collect over time to block out patches of the sky. 

“Another aspect of human impact in space that's more commonly explored is the possibility of Earth life forms contaminating other planets and vice versa,” she says. “As science fiction writers have discussed in books like The Andromeda Strain and War of the Worlds, we don't know what could happen when Earth and alien organisms interact. We've seen how easily diseases can spread globally through planes, but how easily might a microbe hitchhike between planets on spaceships and probes? This is an issue that should be considered before we start exploring further into space, not after.”

Working at the van de Kamp Observatory, Vu—a biology major with a minor in astronomy—finds open-house nights especially rewarding. After all, explaining basic astronomy to the public who come to view the night sky through the powerful 24-inch telescope is important.

“What’s the point of scientists doing all this great research if not everyone understands what’s going on?” asks Vu, who hopes to pursue an astrobiology Ph.D. “If people walk away with a deeper love for space at the end of the night, then it was worth it.”   

And it is—for Swarthmore’s space scholars, sharing knowledge they seize from the currents of at least 100 billion roiling galaxies is as thrilling as the first gasp of delight in finding it.