Engaging Stories—Stars, Population Stats | Cornell Research

In the second installment of our two-part story on academicians, we take a look at the work of a demographer and an astronomer. They are among researchers and lecturers who make tremendous contributions to Cornell’s world-class reputation—part of Cornell’s extreme talent. Their research and teaching help bring academic excellence to their fields.

The Stuff Between the Stars

Studying the cosmos, then passing on what he’s learned to students is a passion for Thomas Nikola, research associate in Astronomy. Nikola studies the interplay between the interstellar medium, the stars, and galactic nuclei. Working with Gordon J. Stacey, Astronomy, Nikola helps build instruments to observe the gas and dust between stars, known as the interstellar medium (ISM), and analyzes data the instruments collect once they are deployed.

“When the radiation from stars hit the surrounding ISM, the gas heats up,” he explains. “It cools by emitting radiation at very specific wavelengths from various elements. Heating and cooling balances, and the gas settles at a specific temperature. Our instruments allow us to observe these emission lines generated by the elements.”

Nikola is helping to develop and build Prime-Cam—the main instrument for the Cornell-led observatory project in Chile, CCAT-prime. He’s also working on an instrument for the National Aeronautics and Space Administration (NASA), building special filters known as Fabry-Perot Interferometers for the High-Resolution Mid-Infrared Spectrometer (HIRMES). The filters will be installed on NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA)—a modified jet that carries an infrared telescope. The instrument will allow researchers to peer into part of the infrared wave spectrum of the universe with more precision than ever before.

While HIRMES is optimized to observe cooling lines from protoplanetary disks, revealing the beginning of planet formation, Nikola will also use the instrument to study the ISM in nearby galaxies. “It’s amazing what you can learn from just a handful of emission lines,” he says. “Each one is slightly different with different sensitivities to temperature and gas densities.”

The researchers gather all kinds of data that reveal a host of stellar information by combining emission lines. “By observing the elements in the gas, we can say what kind of stars we have right now,” Nikola says. “For instance, we can look at age. Most massive stars, which only live a few million years, have the strongest effect on their surroundings. Certain known gas emission lines are caused by the radiation from these massive stars. Finding the emission lines tells us that the age of the star formation producing these stars must be less than the full lifetime of massive stars.”

The researchers use emission lines to pinpoint the abundance of certain elements in the ISM to help them chart the history of the universe, as well. “The universe created hydrogen and helium within its first few minutes; carbon, oxygen, and other elements are only created in stars later,” Nikola explains. “Not all these elements are produced in a single cycle of star formation. When stars die, the elements are recycled into the gas that forms the next stars. This happens repeatedly and increases the element abundance. We can trace these emission lines for various elements way back in time to see how the elemental abundance has changed over the history of the universe.”

“The universe created hydrogen and helium within its first few minutes; carbon, oxygen, and other elements are only created in stars later…When stars die, the elements are recycled into the gas that forms the next stars.”

Passing Knowledge on to Students

Nikola especially enjoys the combination of tool-building and astronomy he’s able to do at Cornell. Over the 20 years that he’s been part of the Stacey lab, he has helped build six instruments for world-class telescopes and develop new technology for future instruments.

“I first met Gordon when I was a graduate student in Germany,” he says. “I was working on an instrument at the Max Planck Institute, and he was the co-investigator. I came to Cornell to work with him. There aren’t many groups who do exactly this. Many focus solely on observations, but few also build the instruments that allow you to carry out research at state-of-the-art observatories.”

Both graduate and undergraduate students come to the Stacey lab to take part in the lab’s cutting-edge work. Supporting and teaching them, Nikola says, is an important part of his work. He emphasizes, “We do everything with the students—programming, electronics, optics, and mechanical hardware. I try to teach them from my experience, especially the undergraduates.”

Nikola continues, “I pass knowledge on to them, and hopefully that knowledge will make it out into the field and possibly out into politics, too. Maybe in their future careers, the students will even influence politicians who decide what kind of science will be done.”

A Population’s Age Composition and Socioeconomic Wellbeing

As a land grant university, Cornell emphasizes research with a public purpose. For Sarah C. Giroux, lecturer and research assistant, Development Sociology, that mission fits perfectly. As the child of teachers, she had an early curiosity about how education impacts people’s lives, including their status and mobility.

“Reading David Grusky’s reader on inequality was a key moment for me. There were so many compelling but seemingly contradictory explanations of how some people and communities get ahead while others lag behind,” she says. “Resolving these theoretical conundrums spurred my interest in social science research that could empirically sort out these questions.”

Her interests in inequality led her to the field of demography, which has traditionally embraced a rich interdisciplinary approach to analyzing questions of social change and development. More recently, Giroux has focused her work on the intersections between demographic forces and social transformations.

“Demographic transition theory holds that countries go from having high fertility and high mortality rates, to a point where mortality declines and fertility is still high, to ultimately a low fertility and low mortality rate,” Giroux explains. “As fertility declines, countries have this one-time window of opportunity when there are a lot of working-age people but not a lot of dependent elderly or children. They have the potential for their citizens to invest and save more. Most sub-Saharan countries are entering this period. The question is, can these countries translate this into something that can boost economic growth, improve people’s livelihoods, and set the course for positive development outcomes?”

Giroux looks at how population age structure impacts a country’s socioeconomic wellbeing. She wants to estimate the size of a country’s socioeconomic dividends when families have fewer children and more resources are freed up for other purposes. “If all these extra resources can be saved, they can potentially be invested in things like business, health, and education,” Giroux says. “But they could also be spent on conspicuous consumption. So policy decisions about how to effectively leverage this opportunity matter. We’re trying to work with policy makers in these countries to understand this one-time opportunity. Once the age structure shifts again, there will be a lot of elderly people who will need to be taken care of.”

The impact of fertility decline on inequality also interests Giroux. “How fertility decline unfolds is going to play a really important role in equitable growth,” she says. “As fertility goes down in sub-Saharan Africa, there is a widening fertility inequality. The fertility of high-income groups declines faster than the fertility of low-income groups.” This disparity means the lower-income groups may stay poor while the higher become even richer.

Research Informs Teaching

Giroux ties her research experience and interests into the courses she teaches. Her favorite class is an undergraduate course on research methods. She helps her students understand the broad implications of scientific evidence and how to conduct research with a public purpose.

“We talk about things like how to form a good research question, how to think about research design, and how to evaluate evidence,” she says. “Achieving sustainable development goals is all about having robust empirical evidence. The more we have that evidence driving the research, the more likely we are to reach our goals.”

Giroux has won the North American Colleges and Teachers of Agriculture (NACTA) Award and the Cornell College of Agriculture and Life Sciences Teaching Award of Merit. She is also the recipient of the Merrill Presidential Scholar Recognition Award, nominated by Merrill Presidential Scholar Kathleen Donnelly Moran ’18, who cited Giroux as the Cornell faculty member who most inspired her during her time at Cornell.

Part One: Captivating Stories, Ways of Doing Science

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