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Jang-Condell’s Research Focuses on Planet Formation In Solar System, Around Stars


June 7, 2012 — Hannah Jang-Condell was not 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," says the University of Wyoming assistant professor of physics and astronomy. "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 that of Earth), range in size from a bit larger than Earth to as much as 10 times the size of Jupiter."

Unlocking the mysteries of planet formation

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 says. "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 says. 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.

Computing the planets

"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 says. "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 says. "And then we have to understand how all these properties change as planets interact with the disk."

For her research, Jang-Condell is studying planets located in the 5-10 AU range. The 5-10 AU range means planets that are located five to 10 times as far from the sun as Earth. These include planets ranging in mass from Neptune to Saturn, she says.

"Our best theories have planets forming in that (5-10 AU) range," she says. "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 NCAR-Wyoming Supercomputing Center (NWSC), Jang-Condell says. She says 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 are on disks.

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

Predicting the age of disks is complicated, she says, comparing it to predicting a child's age based on height. Such a correlation doesn't always provide a direct measurement.

"When you measure a child's height, it gives us an indication of how old they are. But you can have a tall 3-year-old and a short 7-year-old. Height can be one indicator," Jang-Condell says. "If you identify a star as part of a cluster of stars (as opposed to one), you can get better statistics on age. In general, getting the age of stars is difficult. The star disk systems I'm looking at are around 1 million years old, which is considered young."

Is Anybody Out There?

Jang-Condell says she 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," says 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 says. "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 says 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 (WIRO)

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

The NWSC is the result of a partnership among the National Center for Atmospheric Research (NCAR); the University of Wyoming; the state of Wyoming; Cheyenne LEADS; the Wyoming Business Council; Cheyenne Light, Fuel and Power; and the University Corporation for Atmospheric Research. NCAR is sponsored by the National Science Foundation (NSF).

The NWSC will contain some of the world's most powerful supercomputers (1.5 petaflops, which is equal to 1.5 quadrillion computer operations per second) dedicated to improving scientific understanding of climate change, severe weather, air quality and other vital atmospheric science and geo-science topics. The center also will house a premier data storage (11 pet bytes) and archival facility that holds irreplaceable historical climate records and other information.

Photo:
Hannah Jang-Condell, a UW assistant professor of physics and astronomy, will use the NWSC supercomputer to enhance her research, which focuses on investigating how planets form as a byproduct of the creation of stars.


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