Astronomer Oleg Gnedin *99 Models Galaxies and Stars

This is a mock image of a simulated galaxy at high redshift, showing stars (yellow dots), cold molecular hydrogen gas (pink).

A mock image of a simulated galaxy at high redshift, showing stars (yellow dots), cold molecular hydrogen gas (pink) that Gnedin’s team believes fuels the formation of stars, and the other neutral hydrogen gas (blue) that does not directly participate in star formation.

Courtesy of Oleg Gnedin *99

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By Paul Vachon

Published March 3, 2022

3 min read

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This is a headshot photo of Oleg Gnedin *99.

Courtesy of Oleg Gnedin *99

Growing up in Leningrad (now St. Petersburg), Russia, as the son of a respected astronomer Oleg Gnedin *99 recalls listening to fascinating conversation between his father and his colleagues. Yuri Gnedin was known for his work in quantum electrodynamics. The inspiration stuck. 

In 2004, Oleg Gnedin was part of a team that accurately modeled the energy transfer within cosmic gas, developing the first widely accepted solution to the “missing satellites” problem in large galaxies. The term refers to the absence of dark matter halos that should surround some galaxies but are not currently observable. 

He went on to become a professor in the University of Michigan’s Department of Astronomy, where he has  taught since 2006. There he has continued his work with other researchers to construct mathematical models to address how galaxies and star clusters form and evolve over millions of millennia — processes that are influenced by gravity, cosmic gas, and radiation. To demonstrate these changes, the mathematical models he has developed in collaboration with colleagues have advanced to yield 3D simulations. 

His team analyzes a particular area of the sky to generate 3D structures that display changes over time. Since the areas being modeled are made up almost entirely of empty space (since gravity forces structures to collapse), astronomers concentrate their focus on the low density of stars or “resolution elements.” “The tiniest fraction of space is taken up by the densest objects that form stars and galaxies,” Gnedin said. “The totality is known as the cosmic web.”

A progression of Gnedin’s modeling from the largest to smallest cosmic scales: simulated cosmic web to a simulated galaxy to an observed star cluster. They are working on making predictions for the last step.

A progression of Gnedin’s modeling from the largest to smallest cosmic scales: simulated cosmic web to a simulated galaxy to an observed star cluster. They are working on making predictions for the last step.

Courtesy of Oleg Gnedin *99

Achieving a visual representation is exceedingly difficult, he says. But since much of human learning is done visually, representing these concepts graphically has the potential to be more instructive than reading words or equations.   

“But how to visualize it makes a big difference,” says Gnedin. He points out that the same object viewed from various angles under various conditions can appear quite different. The limited resolution of a telescope can also affect an image’s accuracy. To circumvent this problem, his team has produced a series of computer-generated renderings of objects being studied. 

In addition to conducting research, Gnedin teaches an undergraduate course on the search for extraterrestrial life. It begins by defining extraterrestrial life, then examines its potential evolution through the disciplines of astrobiology and geology. It also surveys the ongoing efforts to search for and potentially contact such life. Gnedin presented on the topic at a November dinner hosted by the Princeton Club of Michigan.

As more sophisticated telescopes come online, the images they yield can be compared to their computer-generated counterparts, like those created by Gnedin, and compared for accuracy. Gnedin is eagerly anticipating data likely to come from the new James Webb Space Telescope, which was in development for more than two decades and launched on Christmas Day.

This is a logo image of a program Gnedin ran at the Kavli Institute of Theoretical Physics in Santa Barbara in May 2020, which focused on the formation of the earliest galaxies and star clusters. It shows one triangle of the modeled cosmic web (dark matter density), and the other triangle of an observed region in the sky that has formed young stars. An image of an old globular cluster is in the middle, connecting our understanding of them.

This is a logo image of a program Gnedin ran at the Kavli Institute of Theoretical Physics in Santa Barbara in May 2020, which focused on the formation of the earliest galaxies and star clusters. It shows one triangle of the modeled cosmic web (dark matter density), and the other triangle of an observed region in the sky that has formed young stars. An image of an old globular cluster is in the middle, connecting our understanding of them.

Courtesy of Oleg Gnedin *99

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