UW assistant professor will use supercomputer to seek answers

2012-07-08T00:00:00Z UW assistant professor will use supercomputer to seek answersSpecial to the
Casper Star-Tribune
The Billings Gazette
July 08, 2012 12:00 am  • 

LARAMIE, Wyo. — Hannah Jang-Condell wasn’t one of those kids who gazed at the stars and dreamed of one day becoming an astromer. It was not even until her senior year at Harvard that she took a modern astrophysics course.

“It made me realize there are so many open questions in astronomy. There were not as many open questions in physics,” the University of Wyoming assistant professor of physics and astronomy said. “Astronomy is where I felt I could make my mark. We were discovering all of these exo-planets and their orbits. These exo-planets, which are planets that orbit around other stars (in a solar system other than Earth’s), range in size from a bit larger than Earth to as much as 10 times the size of Jupiter.”

Jang-Condell’s computational astrophysics research focuses on the theoretical study of the origins of planet formation in our solar system and those around other stars. Specifically, her research investigates how planets form as a byproduct of the creation of stars.

“My group is the first to combine the dynamics of gas flow with heating from the central star,” Jang-Condell said. “I study the motion of gas in disks, and how it responds to the planet being in the disks. The disk is heated up by stellar illumination, a process in which a star shines on a disk and heats it up.”

Our solar system formed from a disk, which is essentially made of materials left over after the formation of the sun, she said. In essence, there is a star at the center of the system and clouds of gas located around the star.

One theory, called core accretion, purports that small planets, such as Earth, form from dust in the disk. The dust collides to form pebbles, which become larger and larger, and eventually form giant planets.

The second theory is called disk instability. In this theory, massive and cold disks gravitationally fragment, forming a clump. The clump collapses into a planet. While the planet is forming, it is orbiting within the disk.

In either case, the planet eventually becomes massive enough to clear a gap in the disk. If the disk is heated by starlight, a shadow will form in the disk’s gap. The shadow will cool, while the far side of the disk will heat up and expand by illumination.

“These differences in the temperature structure of the disk can limit how fast a planet can grow. These are effects I am trying to model,” Jang-Condell said. “How fast is a gap opened? If you have shadow effects, how does it affect the future growth of the planet? After the gas disk phase, planets can scatter off of each other.

“Properly modeling these disks can be quite computationally intensive, since one needs to take into account the dynamics of the disk material, the composition of the disk, the heating of the disk by stellar irradiation and viscous forces,” she continued. “And then we have to understand how all these properties change as planets interact with the disk.”

Jang-Condell is studying planets located in the 5-10 AU range. The 5-10 AU range comprises planets located five to 10 times as far from the sun as Earth. These include planets ranging in mass from Neptune to Saturn, she said.

“Our best theories have planets forming in that (5-10 AU) range,” she said. “We’re studying smaller planets. We’re studying the interactions of planets and disks. Computational time goes into modeling physics.”

NASA has provided $300,000 over three years to fund Jang-Condell’s research.

Desktop computers are good for conducting test simulations, but creating a full-scale computational model will require use of the National Center for Atmospheric Research Wyoming Supercomputing Center, Jang-Condell said. She submitted a proposal for use of 7.8 million core hours on Yellowstone, the supercomputer’s name, in Cheyenne.

The idea is to use the computational models to understand the significance of starlight and shadow effects on disks.

“We can actually image disks around young stars and see gap-forming events,” Jang-Condell said. “We can compare these images with outputs of simulations and see where planets are forming in the disks.”

Jang-Condell believes in the possibility of life on other planets. She points to continuous discoveries of new life forms on Earth — in regions as remote as Antarctica and at the bottom of the oceans — that no one thought previously existed.

“My opinion is, wherever life takes hold, it adapts and survives. I do think that, anywhere there’s a planet that can sustain liquid water on its surface, it is going to have life,” said Jang-Condell, who suggested Mars and Europa may contain microscopic life. “This is my opinion. It has not been confirmed by observation. We are able to detect Jupiter-like planets around other stars, but Earth-like planets are hard to detect.

“Humans are naturally curious about from where we come. Are we alone in the universe?” Jang-Condell continued. “By understanding how planets form, we can begin to understand how common other planets are like Earth. Are there other life forms? Are there others we can contact? We are asking some of the most existential questions humans have.”

Jang-Condell said she will transition from her theoretical research approach to a more observational endeavor this summer. That’s when she will work with a graduate student at the Wyoming Infrared Observatory.

“We have our own 2.4-meter telescope there,” she said. “Even though I’m a theorist, I am starting a project to detect the atmospheres of exo-planets.”

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