Frontiers of Science

Observing the birthplace of stars with a radio telescope

How are Stars and Planets Born? ──

Yoko Oya

Department of Physics, Assistant Professor

June 8, 2022


The Atacama Large Millimeter/submillimeter Array (ALMA), is a radio telescope that uses a network of 66 connected antennas to peer into the distant universe.
Advanced researchers use state-of-the-art telescopes to delve into the mysteries of star and planet formation.

The ALMA observatory in Chile, South America, is home to one of the world’s largest radio telescopes, built by an international collaboration between Japan, the United States, and Europe. It can observe astronomical objects with its 66 antennas and combine the data they receive to achieve the same resolution as a radio telescope with a maximum aperture of 16 km. The higher the resolution, the better we can discern smaller structures in the universe, or in human terms, the better our eyesight.

“We use the ALMA radio telescope to observe newborn stars. The birthplace of a star or planet is in a cloud of cold gas or dust, which is hidden to observation by visible light, but radio waves transmitted through the cloud allow us to see inside. Also, the various molecules in the gas cloud emit radio waves at specific wavelengths, so we can identify the molecules that are present at the birth of stars and planets.

Assistant Professor Oya of the Department of Physics has made a series of groundbreaking achievements in the field of star and planetary system formation.

“In my doctoral dissertation, I described the chemical composition of the protostellar disks that surround protostars. I found that the chemical composition is different from the outside to the inside of the disk.”

A planetary system is eventually formed from such a protostellar disk. The fact that its chemical composition is not uniform throughout will have a significant impact on the composition of the planets that are finally created.

Although Assistant Professor Oya’s research is in the field of astronomy, her affiliation is with the Department of Physics, not the Department of Astronomy, and the research topic of her laboratory is astrophysics. She explains what it means to study astronomical phenomena as a physicist.

“I’m interested in the laws of physics that underlie various astronomical phenomena. My sense is that astronomers tend to focus on the peculiarities of individual phenomena, while physicists try to find the universalities that are common to all phenomena. The two disciplines appear to differ in their approach and perspective.”

Assistant Professor Oya did not originally intend to pursue research in astrophysics. “I’ve loved mathematics and physics since I was in high school, and when it came time to choose the faculty for my studies in third and fourth year (in accordance with the University of Tokyo’s shingaku-furiwake system), I had a hard time deciding between the two. In the end, I chose the physics department. I never once thought about pursuing astronomy as a career.”

She started studying astrophysics when she selected her laboratory for graduate school. “I chose this laboratory because I was drawn to the character of my advisor, Professor Satoshi Yamamoto, whose research interest was astrophysics.”

In the Department of Physics, “Our two years were classroom-based, and the fundamentals of physics were drilled into us thoroughly,” she said.

“Today, I’m still using the basic skills I developed there. I started studying space and astronomy in graduate school, and I feel that I’m now on a par with those who specialized in astronomy. My friends who didn’t go on to graduate school but went to work in the private sector tell me that their physics studies have been very helpful to them.”

Expressing her wishes for the future, Assistant Professor Oya says, “I’d like to understand the fundamental laws underlying the formation and evolution of stars and planetary systems. It’s the enjoyment of science and physics, and the motivation for research that bring us closer to universal laws. I’m currently studying the formation of stars and planetary systems, but I might change my research field in the future. The field may change, the subject may change, but my desire to find simple theories that explain diverse phenomena will never change.”

Interview and text: Masatsugu Kayahara
​Photography: Junichi Kaizuka

Originally published in The School of Science Brochure 2020

Yoko Oya
Department of Physics, Assistant Professor
Graduated from the University of Tokyo in 2013 with a Bachelor of Science in Physics. She obtained her Ph.D. in physics from Graduate School of Science at the University of Tokyo in 2017, and has been in her current position since then. Her specialty is radio astronomy. In 2018, she received the University of Tokyo President’s Award and the Inoue Research Award for Young Scientists.


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