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Alien Skies, Alien Clouds

Exploring the Sandy Clouds of Brown Dwarfs

If you’ve never met Zac Shakespear from Eugene, Oregon, the first thing you might notice about him is his famous last name. Nor is it a misnomer, as Zac is an avid writer—but not of tragic plays like Hamlet. Instead, Zac writes science fiction: “I'm publishing a book at the end of the month and so excited about that!” But that’s not even the tip of the iceberg for the role of science in Zac’s life.

Ever since he was a child, Zac has been awed by science. “I stumbled upon a documentary series called The Universe on Netflix way back in 2011. I binged those episodes, learning about the life cycles of stars, black holes, and dark matter.”

Unfortunately, middle school and high school disappointed him with their nonexistent selection of astronomy classes. Zac read astrophysics books to pass the time until he could finally fulfill his dreams at a university. “So when I came to BYU in the fall of 2018,” he said, “I was thinking, ‘Yes, finally I can do this.’”

To kick off his BYU experience, Zac joined the Late Summer Honors program, a week-long Honors experience the program sponsored until 2019. He smiled as he told the story of meeting his wife during that week: “I commented to her that she had a beautiful alto voice.” Together, they also took an Unexpected Connections class, which focused on astronomy tied with literature like the Chronicles of Narnia. Zac loved that Honors had a “focus on things that I felt actually mattered.”

As a freshman, Zac joined a research group studying blazars (a type of black hole). “I really enjoyed learning how to use robotic telescopes to collect data, as well as the procedures that make the data usable for research, while I was a freshman.”

After he returned from his LDS mission, Zac worked with a couple other professors before joining forces with his Honors thesis advisor, Dr. Denise Stephens. She happened to be one of the professors who had team-taught the Unexpected Connections class he loved, as well as the first BYU female faculty member in Physics.

Zac and Dr. Stephens decided that for his thesis, Zac would analyze data from the James Webb Space Telescope. The telescope is brand new, having launched on Christmas in 2021, and it produces amazing images. Zac said that the James Webb also “looks at a region of the electromagnetic spectrum that a lot of telescopes don't, and we were seeing some interesting things there.” He focused on emissions from brown dwarfs.

Brown dwarfs are too big to be planets, but too small to be stars. They start at about 18 times the size of Jupiter. Studies show that their atmospheres are swirling with silicate (sand) clouds. Emanating from brown dwarfs is a spike and dip in the L prime infrared radiation band, which seems to be explained by the sandy clouds.

However, after analyzing the data, Zac was in for a surprise. “The magnitude of the L prime band was inversely proportional to the strength of the silicate feature,” he said, “which meant that when you had silicates inside of the atmosphere, this spike tended to be a little bit lower. And then when you didn't have it, it ended up being higher.” That was the opposite from what he had expected.

Zac’s theory is that current cloud simulators simply aren’t up to the complicated calculations needed. “The models that I'm familiar with use one number to represent everything about a cloud!” he said.

“Here on Earth, we have lots of different kinds of clouds. You have your really big cumulonimbus clouds, your wispy cirrus clouds, and flat clouds like the ones that I grew up with in Oregon. It's very difficult to show all of that variety when you only have one number. So, my conclusion was that we needed to complicate our models of clouds to really figure out what's going on with this spike inside of the L prime band, and how (or if) it’s related to the silicate feature.”

Based on Zac’s Honors thesis, he and Dr. Stephens will submit a research note to the James Webb telescope. This will serve as a petition for additional telescope time, which is famously difficult to obtain. “The odds are small, but I think that the research that I've done as an undergrad increased our chances. My team put in a proposal for telescope time last year, and it was rejected principally because this research wasn't attached.”

That’s the hope for this summer. This fall, Zac will begin his graduate studies at BYU. He is excited to continue working with Dr. Stephens toward his PhD. Zac has come light years from a kid watching a space documentary, and his future is far brighter than the brown dwarfs he will continue to study.