Physics doctoral student leads new study about plausibility of exomoons

Monday, Feb 14, 2022 • Greg Pederson :

Oshina Jagtap, UTA doctoral student in physics

For planetary physicists, establishing the existence of exomoons – natural satellites in orbit around extrasolar planets – has been an elusive undertaking. These extraterrestrial moons exist in theory but thus far, that’s all.

Because moons are fairly common in our own solar system – more than 200 at most recent count with Saturn alone accounting for 82 – most astrophysicists are convinced that they exist outside of our solar system as well. Because they are relatively small, the problem has been finding them.

A new paper co-authored by three astrophysicists working at or with ties to The University of Texas at Arlington explores the possibility of exomoons in a planetary system named HD 23079, located in Reticulum, a small constellation in the southern sky. HD 23079 contains a star slightly hotter and slightly larger than the Sun as well as a Jupiter-mass planet in the stellar habitable zone – that is, the area around a star in which a planet can possess liquid water on its surface and possibly support life.

Oshina Jagtap, a UTA first-year doctoral student in physics, is the lead author of a new paper, titled “Updated studies on exomoons in the HD 23079 system,” which was published in Volume 38 of the journal Publications of the Astronomical Society of Australia. 

Co-authors are Billy Quarles, an assistant professor of astronomy and physics at Valdosta State University in Georgia who received his Ph.D. in Physics from UTA in 2012; and Manfred Cuntz, UTA professor of physics and Jagtap’s faculty advisor.

“In the past few decades, scientists have discovered more than 4,000 exoplanets, but for exomoons there are no confirmed detections yet (although there are currently two candidates),” Jagtap said. “Gas giants such as Jupiter can’t host life, but moons of gas giants are interesting candidates to host habitable environments. Some previous works explored an Earth-mass moon around the Jupiter-like planet of the HD 23079 system. We improved upon their calculation of stability of orbits of moon around the Jupiter-mass planet.”

Jagtap and her co-authors used detailed simulations in their study. She added that their analysis modestly reduces the range of stability calculated previously, but despite this, the HD 23079 system holds promise for hosting a moon in the habitable zone.

“Exomoons in the system of HD 23079 are highly plausible for two reasons,” Cuntz said. “The first reason stems from previous theoretical simulations about planet and moon formation in general stellar systems. The second reason stems from a careful analysis of the solar system itself. The poster child in that regard is Jupiter, a host to four planet-size moons (among many other moons), with two of them (Europa and Ganymede) having a significant chance of being habitable.”

In addition to theoretical simulations, Jagtap and her co-authors also forwarded observational constraints on exomoons in the system relevant to future space missions, including missions by NASA.

Jagtap grew up in Indore, India, with an innate curiosity about everything. “I loved asking questions and finding answers to them,” she said.

She excelled at math in school and some of her teachers steered her towards physics. She came to UTA for her undergraduate studies as an engineering major, but when she found out that physics only played a small part in most engineering jobs, she switched majors to physics.

“I realized that physics and especially astrophysics is something I can do all my life without regrets,” she said.

As an undergraduate, she took all the astronomy-related elective courses she could in order to learn more about the different varieties of research being done at UTA. Cuntz and Sangwook Park, UTA professor of physics, along with their graduate students, inspired her to focus on planetary science and to remain at UTA for her doctoral studies.

“The great thing about UTA’s astronomy program is that everyone I meet is encouraging and patient,” Jagtap said. “The astrobiology class taught by Dr. Cuntz that I took introduced me to exoplanets and planetary science.”

Jagtap graduated with her B.S. degree in Physics in May 2021 and began her doctoral studies in August. In addition to her research on exomoons, she is also part of a collaboration with astrophysicists William Danchi and Carol Grady of the NASA Goddard Space Flight Center in Greenbelt, Maryland, which involves the study of stellar disks. 

One of her ongoing projects involves the system AU Microscopii, a young, low-mass star located about 32 light years from Earth and situated in the Southern Hemisphere. It has at least two planets and a circumstellar disk of debris, assumed to be the site of ongoing planet formation.

Cuntz noted that future observations of the system HD 23079 can make use of the new study’s results through a scale factor relative to the currently measured minimum planetary mass. Jagtap and her co-authors are excited to see what future studies of HD 23079 will reveal.

“Although the existence of exomoons in the system HD 23079 is not yet confirmed, the future detection of exomoons in that system is expected,” Cuntz said. “Actually, the detection of any exomoon in that system would be of no surprise; in fact, the surprise would be their absence.”

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