November 08, 2023

【Special INTERVIEW】- Dr. Cui Yuzhu, Graduate of SOKENDAI

Dr. Cui Yuzhu
Postdoctoral researcher of the Zhejiang Lab
Graduate of SOKENDAI, Department of Astronomical Science (2021)

Impact of the press release

  1. First and foremost, Omedetogozaimasu for your press release “Two-decade monitoring of M87 unveils a precessing jet connecting to a spinning black hole “. It has been a great deal of attention worldwide. How do you feel about it?

Dr. Cui : It feels like a dream. I did not expect the impact to be so large. We had 79 co-authors in this paper and around 10 countries and 45 institutions were involved. It's a very international cooperation. Then every co-author tried their best to help us to advertise our work. That's why you can find our press release in various locations, such as Korea, Japan, China, Italy, Malaysia, and across Europe. I didn't expect such a big spread.

Long journey

  1. I am sure you have been researching for a very long time leading up to this press release.

Dr. Cui : Yes. As you may notice from the press release, we started this project from 2017. That means six years ago. That is the time I entered SOKENDAI. When analyzing the EAVN (East Asian VLBI Network), the first set of real observational data, I noticed that the jet direction is different with previous study. From that point, we started to find the answer to the question. It's a long journey.

  1. Six years?

Dr. Cui : Yes, six years for study. The data covers 23 years.

  1. What is the most difficult part of your research? I assume analyzing a huge amount of data might be very tough.

Dr. Cui : Yes, that's one part. But actually, I was enjoying the procedure because we had a very clear question, why M87 jet is precessing, to be answered. So, the only thing we needed to do was to accumulate the data and enlarge the time scale to determine the period more precisely. Maybe the toughest point was to keep the patience. I consider myself fortune to have had Honma-san and Hada-san as my supervisors at SOKENDAI. That was the most important point.

If you check my record in SOKENDAI, you may notice that my course was a three-year PhD course. But I took four and a half years to complete it. That means I began my program in October 2017, but I didn't graduate until December 2021. I had to extend my PhD. There were many reasons like COVID-19 and the time needed to accumulate long-term data. During these years, I had no output. So, I was very disappointed in myself. I wanted to give up my PhD at that time. But luckily, I had Honma-san and Hada-san. They encouraged me very much. When I said I would like to give up the PhD course, Honma-san and Hada-san said, “No, no, no, no. You should not do that. If you do that, the astronomy will lose, we'll lose one star”.

  1. That's a big encouragement.

Dr. Cui : Yes, very encouraging. And if you know Hada-san, he is always perfect. He is a young, smart and very kind person. Everything is so perfect. But he told me some of his failures to encourage me. He said, “Even though you saw me now were very successful, I also came across many failures”. I think he inspired me by telling me about his own failures and I really appreciate it.

  1. In 2019, the Black Hole in the M87 Galaxy was photographed. It might have had a great impact on your research activity. Were you a member of that project?

Dr. Cui : I was involved in this EHT(Event Horizon Telescope) project since 2017, thanks to Honma-san and Hada-san's recommendation. Then, that's also one milestone to encourage me to continue this black hole research. That's really a good memory. We had a big press release in Tokyo.

  1. Dr Hada said that you have contributed not only to Jet’s research but also in promoting collaboration between Japan-China radio telescope network. What was the role in the operation of EAVN?

Dr. Cui : I was the Principal Investigator (PI) for the M87 EAVN project, and the data from that project was used in the Nature paper. Under Hada-san's supervision, I was responsible for writing the proposal, obtaining the observational data, collecting and processing the data, and subsequently, drafting this paper. When I joined SOKENDAI in 2017, one of my tasks was to serve as a bridge between China and Japan, because I'm Chinese and studying in Japan. This role allowed me to facilitate connections to build up cooperation between these two countries.

As a result, we did a good job in this collaboration. We successfully welcomed Chinese telescope joined. My first PI paper was about the evaluation of EVAN's performance which is mainly about the newly included telescopes from China. That was a significant step forward as we integrated the Chinese telescope into KaVA. That was my role within this team.

Exploring the Edge of the Universe

  1. Were you interested in stars from a very young age?

Dr. Cui : Yes, during my childhood, I was so interested in the black expanse of the night sky. We see stars shining but the background is always black. I was curious about the edge of the universe and what was in the black area. But, at that time it was not so clear whether I should become a scientist. It was just a seed in my mind. When I was in master's degree, I realized that astronomy was very interesting for me. I should keep on.

  1. So, you decided to become a researcher when you were in a master's degree program?

Dr. Cui : Yes. It was a quite late stage.

Research life in SOKENDAI

  1. Why did you decide to come to Japan?

Dr. Cui : The decision of studying abroad in Japan was made in 2016. I liked Japanese anime, very much when I was in college. When I graduated with a master’s degree in 2016 and was thinking if I would study abroad, Japan should be the first choice. The first reason was my private interest in Japan. The second one was more professional. When considering the VLBI(Very Long Baseline Interferometry) technology, Japan was very good choice. I knew I could find very professional supervisors and gain many practical experiences in Japan. This was the second reason related to the research. The third reason was that I got some recommendations about Honma-san and Hada-san. I knew that they were very good supervisors. As a result, I didn’t apply to any other schools. I only applied for SOKENDAI, the only one choice I considered in the world. So, I didn’t send any proposal to Chinese colleges or other schools in Japan or abroad. I only focused on SOKENDAI.

  1. Have you heard of SOKENDAI?

Dr. Cui : I learned about it from Hada-san. Before my entering examination, I had the chance to meet Hada-san and Honma-san at an international conference in China. Then, Hada-san told me that he had also graduated from SOKENDAI, and SOKENDAI was a very professional and good university with a very wide range of research fields.

  1. So, how was your experience in SOKENDAI? Was it as you had imagined before entering SOKENDAI?

Dr. Cui : Yes, it was very good. If you had the chance to take a look at my PhD thesis, you would find one sentence “to my good memories in Japan” behind my cover page. That's all because of my choice of SOKENDAI. My SOKENDAI research life was very enjoyable. Even though I was based at the MIZUSAWA Observatory, which is very far from Tokyo and other modern cities, I enjoyed a lot, because SOKENDAI provided me enough financial support and the secretaries, and the administrative staff were kind and warmly supported me. I didn’t have to worry about anything beyond my research. It was so nice. I appreciate it very much.

  1. We strongly believe your talk will fascinate those who are interested in science and aspire to be scientists in the future. Could you tell me what an ideal scientist is for you?

Dr. Cui : Hada-san and Honma-san !

At the EHT press conference in April 2019.
In the center of the photo is Dr. Cui Yuzhu (Mizusawa VLBI Observatory / 2nd doctoral year at SOKENDAI).
On the left is Assistant Professor Kazuhiro Hada and on the right is Professor Mareki Honma.

  1. As a scientist, I think you had so many difficult times, such as sleepless nights, hard work at lab, and so on. You even might have come across giving up on your research. How did you keep your motivation as a scientist?

Dr. Cui : While there are many famous scientists who have very tough minds and very rich experience which can encourage us, in my personal experience the key persons were Honma-san and Hada-san. Although they are not so famous as some Nobel laureates, they are super important to me. When I had difficult times, they offered me to do something different from work. For instance, Hada-san took us to Onsen. Honma-san and Hada-san even took me to the barbecue, a hobby of mine. They always give me good and warm encouragements. So, to me, they are more important than any other famous persons for me.

  1. They changed your life.

Dr. Cui : Yes, almost. I remember when I did the first-time extension. I said it's too tough. I cannot continue.” to Hada-san and Honma-san. I even said, “I just want to change my career to another life, rather than to be a scientist. I can go to a company to do other things”. But Honma-san just kept saying that you had potential to be a scientist.

Why is the black hole so attractive?

  1. May I inquire about the projects you're currently working on in your research field?

Dr. Cui : My primary project is to continue the published paper because that paper is just a start. We just showed the possibility, but there are a lot of unknowns. We need to continue the research on some detailed physical properties. Additionally, I’m involved in a project related to the 500-meter telescope in China, which has an impressive 500-meter diameter. This massive telescope seeks to join the VLBI. So that means many telescopes observe one target together for high-angular –resolution imaging. So that's my second task. Maybe that's enough for me to work for a period.

  1. So, will you continue to focus on M87?

Dr. Cui : Yeah!

  1. Why are black holes attractive to you?

Dr. Cui : Because they are very powerful and energy sources for many systems. Additionally, black holes are the easiest compact component to test the Einstein general relativity. It's simple but complex. So, they are very interesting.

  1. Yeah, it must be exciting to find out new things, explore the unknown world.

Dr. Cui : Yeah.

  1. What are you going to try to find out beyond the exploration of the universe or the unknown world?

Dr. Cui : Theoretical exploration. Actually, I'm a little bit curious about the concept of parallel spaces, such as worm holes. You might be familiar with the idea that once you jump into the black hole, you can enter another parallel space. You have different choices in that space and universe. Many things are connected by the black hole. But we do not know what's inside the black hole. And in theory, we really cannot observe what's inside the black hole. So that's maybe the things beyond real research.

  1. I watched the movie “Interstellar”. In that movie, people dive into the black hole which connects to another world or another time.

Dr. Cui : Yeah, the time machine and something. And some movies also say that we can jump back to some old or future period by black holes.

  1. Is it beyond reality or is something realistic for you?

Dr. Cui : I don't know. My feeling is it's far from the reality. But I hope we can, in future, have this kind of research result. It would be great if we could have some time machines and we had some parallel spaces.


Life is a flat area. You can make any choice.

  1. Can you leave a message for those who aspire to become researchers?

Dr. Cui : Okay. Maybe just keep doing it. Trust yourself and don't be judged by other people. There's one Chinese sentence I was using to encourage myself. 人生是旷野,而不是轨道. In English, “Life is a wilderness,not a track”. You don't need to follow any exact routine to do something. You have many choices in this wilderness. Just every direction which makes you happy is a good choice. So, you just need to keep this thing, but you don't need to force you to do only one routine, like a train.

  1. That's a really good phrase.

Dr. Cui : Whenever I feel very sad, I just think that my current choice is the best choice. So just trust myself.

It's a powerful word. What if you don't feel confident in what you are doing? Do you think you need someone like Hada-san and Honma-san to support you?

But in most cases, we do not have this kind of person surrounding us. In that case, we should find a way to cheer ourselves up to build our confidence. When I was too depressed, I found a way to cheer myself up. The decision to study in Japan was a kind of last chance given by myself to check whether I can become a scientist. At the later part of my PhD period, I had no output and thought I could not do any research. I thought I had better to give up. But Honma Sensei and Hada -san, understood my true willingness of being a scientist was covered by some disappointing things, like no output for a long period and homesickness. They repaired my confidence and encouraged me to continue. I remember there was one sentence said by Hada-san: “If you gave up now, next time when you face any other difficulties, you will always want to give up”. It is my luck to meet Honma sensei and Hada-san. Because of all the experiences before, I can figure out who I am, namely I can learn much from positive persons. Publishing Nature paper or being a scientist might not be so important. Instead, it is very important to find ourselves and be good to people surrounding us.

  1. Thank you very much for your time today.

Dr. Cui : I only have many appreciations to all of you. SOKENDAI is so amazing place. I really appreciate the chance to study Japan offered by SOKENDAI. I also won the MEXT scholarship thanks to SOKENDAI’s recommendation.

General Planning Division, Public Relations Section, Section Chief
GOTO Shinichi