Physics against boredom

March 03, 2023

Originally a chemist, Taeho Ryu started studying physics, because he was bored during an extended hospital stay.

What is your research interest at MPA?

The Universe has very creative ways to produce transients – some of these astronomical events last no more than the blink of an eye. In trying to understand these, I have been investigating in particular the formation of transients associated with the disruption of stars by black holes of all mass scales, from stellar-mass black holes (see movie) to supermassive black holes. Since I joined the Stellar Department at MPA, I have become very interested in interacting binaries. My primary methodology is to perform magneto-hydrodynamic simulations of target systems using the moving-mesh code AREPO or the relativistic Eulerian code HARM3D. With the simulations, we also predict the observational signatures of these transients and compare them to actual observations.


Stellar disruptions

This movie shows how binary stars are disrupted by a stellar-mass black hole (pink dot). The three-body dynamical interaction between the binary star system and the black hole was simulated with the AREPO code.

How did you get interested in this topic?

After I got my Ph.D. at Stony Brook University, I was able to gain experience in relativistic magneto-hydrodynamic simulations. The first scientific application were tidal disruption events of stars by supermassive black holes. The fact that stars can be completely disrupted by black holes in a few hours was very scientifically attractive to me. This is generating a flare bright enough to outshine the entire host galaxy! Many aspects of the events are not fully understood, which motivated me further to study these extreme events.

MPA is the perfect institute for me to continue my research on transients. First, there are many experts in various fields closely connected with tidal disruption events, such as stellar astrophysics and stellar dynamics. Second, the computational support and facilities at MPA played a vital role to boost my projects, which require a number of computational simulations.


What made you choose science?

My journey with science started in middle school, where I joined the science club. Back then, I was just a teenager who casually thought about being a scientist. A few members of the club – including me – were allowed to use any experimental instruments or materials in the lab, except for some dangerous chemicals. That was when I realized science was fun! I wanted to be a chemist and I chose chemistry as my undergraduate major.

After sophomore, I enrolled in the Korean army. On duty, I got into a massive car accident one day and spent the next six months in a hospital due to fractures of multiple bones, perforation of the small intestine, and more. I was bored at the hospital, so I started studying physics, once I could read books and write letters – simply because there was nothing else, I could do. This was a life-changing moment for me: I realized that wanted to study physics, not chemistry any more.

After being discharged from the military, I focused on studying physics and then went to the US, where I entered a graduate program majoring in physics. By then, I already knew I wanted to study black holes, but was wavering between astrophysics and string theory. After a few attempts in different fields, I found that Astrophysics was what I wanted to do for the rest of my life; and I am very happy about my decision. Since then, my research interests have been pivoting around black holes as astrophysical objects.


What do you enjoy about working at MPA?

The most significant part of my life in Germany has been doing research, which I undoubtedly appreciate. There are many moments, when I really enjoy doing science. I made the right decision to come to MPA; it is great to have informal discussions with enthusiastic people who are not afraid of throwing around lots of interesting and exciting ideas. Such interactions and a friendly environment are what I had been craving.


How do you like to spend your time outside the institute?

I love all sports and outdoor activities. In particular, I am a big fan of ball games. My current favorite is tennis. Every Saturday, I take a lesson and I play matches in a tennis club.

Other hobbies are Sci-Fi movies and TV shows, such as Star Trek and Expanse, or live music shows. Before going to the US for graduate study, I played the drum in a few rock bands, and I enjoy going to live music shows such as Jazz or Rock.

It is great to live close to a vibrant city such as Munich, but I am actually very much enjoying my life in Garching. Although Garching is not the kind of place that is very dynamic and changes every day, I found it always safe and peaceful. As someone who prefers stability, I appreciate its steadiness. 

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