We are saddened to report the passing of our colleague Frank Shu on April 22, 2023, age 79, at home in Atherton, CA.

He was born in Kunming, China, in 1943, and emigrated to the U.S. With his family at age 5, he graduated from M.I.T in 1963 and obtained his PhD from Harvard in 1968. After a brief period at Stony Brook University, Shu joined the faculty at the University of California, Berkeley in 1973. A University Professor Emeritus at the University of California, Berkeley, and University of California, San Diego, Shu was best known for proposing the density wave theory with his PhD advisor C.C. Lin, to explain the structure of spiral galaxies and for initiating a new paradigm of star formation in molecular clouds. He also made important contributions in the areas of close binary star systems, the origin of meteoritic building blocks in the solar system, and spiral structure in planetary rings. Most recently, Shu focused his efforts on issues related to climate change and developed new concepts using molten salt technology to process waste biomass into biocarbon products and designs for nuclear reactors.

As an educator, Shu mentored a large number of graduate students who have gone on to successful careers in astronomy and related fields. His introductory textbook The Physical Universe and graduate-level textbook Physics of Astrophysics have become classics. Shu served as chair of the Astronomy Department at U. C. Berkeley, chair of the Center for Astrophysics and Space Sciences at U.C. San Diego, preparation-committee chair for the establishment of the Institute of Astronomy and Astrophysics Academia Sinica, president of the American Astronomical Society, president of National Tsing Hua University in Hsinchu, Taiwan, and senior fellow of the Hong Kong Institute for Advanced Study at the City University of Hong Kong. For his contributions, Shu was elected to the American Academy of Arts and Sciences, U.S. National Academy of Science, American Philosophical Society, and Academia Sinica, and has received many awards, including the Helen B. Warner Prize for astronomy, the Brouwer Award in dynamical astronomy, the Dannie Heineman prize in astrophysics, and the Henry Norris Russell lectureship, from the American Astronomical Society, the Shaw prize in astronomy, and the Bruce Medal from the Astronomical Society of the Pacific.

For his contributions, Shu was elected to the American Academy of Arts and Sciences, U.S. National Academy of Science, American Philosophical Society, and Academia Sinica, and has received many awards, including the Helen B. Warner Prize for astronomy, the Brouwer Award in dynamical astronomy, the Dannie Heineman prize in astrophysics, and the Henry Norris Russell lectureship, from the American Astronomical Society, the Shaw prize in astronomy, and the Bruce Medal from the Astronomical Society of the Pacific.

I am deeply saddened to hear about the passing of Frank. Frank was such a visionary scientist and a great educator. Though he has left us, his contributions to science and education will be always remembered by us. I particularly appreciate his leadership role in shaping the development of the Institute of Astronomy and Astrophysics at Academia Sinica and his contributions to the development of molten-salt energy. Dear Frank, our thoughts are always with you and your family.

Time runs fast, and we cannot stop it. For that reason alone, life should be filled with happiness as much as we can. Frank, at the behest of Typhoon, had brought a group of overseas Chinese astronomers to come back to Taiwan to restart astronomical research in a more substantial way. In the 1990’s, astronomy in Taiwan was concentrated at the National Central University, and we were working on how to make the research efforts grow bigger and faster. I remember vividly that after many meetings with senior leaders in science and education in Taiwan, we have been discouraged by the lack of progress. Frank held a meeting with a group of us at the Academia Sinica, and he said we could all return home and continue to write our papers for the next ten years, or we can keep working to see how we can make real changes in Taiwan for the better. It was inspiring and motivating, and classic Frank in vision and purpose. He was talking about impact in our lives. But what he achieved over the last thirty years were the impact on the lives and careers of so many students and so many young people and colleagues, not only in Taiwan but even beyond. I think every moment spent with Frank has always been filled with laughter, happiness, and sense of purpose. His presence will continue in the fabrics of the lives of all those who have had the privilege of meeting and working with him. It has been a very meaningful 30’years.

It has been said that your future is shaped by the people you meet: Frank was definitely a strong influence for me. Initially, it was based on our common scientific interests in stellar astrophysics involving interacting binary star systems, which later evolved to working on the evolution of protostars.

The second phase, lasting greater than a quarter of a century, involved developing astronomy in Asia with an initial goal of establishing a preparatory office in astronomy and astrophysics within Academia Sinica. In so doing, Frank articulated and espoused a vision fostering its development and exploring pathways toward establishing the ASIAA as an institute whose mission was to conduct forefront and fundamental research at the international level. This would lead to the development of the human resources for the future generations of astronomers. Many discussions were held, some behind the scenes, taking place on various occasions over countless meals and venues.

We returned to collaborative research in the most recent decade as Frank shifted his focus to the issue of climate change. In one development, Frank promoted the use of molten salts to torrify biomass into biocarbon products in an oxygen free environment. In another, he developed new ideas for the design of small modular molten salt reactors for clean energy and nuclear waste management.

Throughout our journey in these various phases, I valued Frank’s guidance, advice, insight, and forward thinking which forged our future. He was always generous with his time, and I treasure our years of friendship and collaboration. He is sorely missed, but his spirit will be with us. His memory will guide us as we strive to continue his traditions of excellence in science and work toward the greater good of humanity in climate change mitigation. In humble gratitude, my family and I thank Helen, his esteemed partner and spouse, for sharing him with us.

Frank had a profound and positive influence on my career, as he did on the careers of most if not all of his PhD advisees. I have many fond memories of the numerous hours that we spent together in his office, discussing theories, working out calculations on the blackboard, and talking science in general. Sometimes the discussions veered off into other directions, always interesting and occasionally profound.

Frank and I also played softball together for the Berkeley Astronomy Department intramural team, the Spiral Arms. In the picture I took of him batting, you can see how intensely Frank concentrated. He enjoyed playing and was, not surprisingly, quite competitive. One game that we played on astroturf (a hard surface), while running the bases, he made a head-first dive into 3rd base. The next day, when we were meeting in his office, he told me that he was bruised and thought he was too old to play!

Frank sometimes used baseball (and other) analogies in science. It was important to hit singles and doubles to keep in good standing in the profession and to maintain research grant funding, but one is remembered for those few home runs. And to get a home run, the first thing was to choose your pitch (problem to work on), keep your eye on the ball, take a strong swing, connect, and then run around the bases. Frank hit far more home runs (in astronomy) than almost everyone else, and also was a great batting coach.

I am deeply saddened by the departure of Frank Shu. I really wanted to see him again! He has been such an inspiration and such a joy to talk to. I will never forget when he came to see my first poster and, after 30 seconds of reading, turned to me and asked: “what’s next?”. Of course, I did not expect this question, so I had to think very fast about my answer. But, I have to say, these words (“what’s next”) have always resonated in my mind and I keep hearing them every time I finish some work. Thank You Frank for all your insight, genius, joy, and friendly smiles.

Frank Shu being unconvinced by an argument from Lee Hartmann, at the IAU XXVth GA in Sydney, 2003.

Frank, I can never thank you enough for the recognition you gave me and the physical insight you instilled in me as a young observational astronomer at a small liberal arts college. I have carried these gifts with me throughout my career, along with fabulous memories of star formation workshops at Santa Cruz, Berkeley, and later Wellesley. I just wish I had had the courage to play poker with you. You are missed

Frank was an essential part of the Center for Star Formation Studies, a consortium of astrophysicists (faculty, students, postdocs) from UC Berkeley, UC Santa Cruz, NASA Ames and Lawrence Livermore Laboratory. It existed from 1985 to about 2003, met almost monthly for all day workshops, and gave many summer weeklong workshops in various locations, including Harvard and Taiwan, but mostly at UC Santa Cruz. Frank contributed greatly to efforts in star formation, disk evolution, and planet formation at the Center, not only through his own work with collaborators, but with his incredibly stimulating comments and suggestions at the workshops. In addition, his humor (often teasing Doug Lin!), organization of poker games and supervision of the food at Chinese restaurants led to highly entertaining and pleasurable sessions. The photo is of the Center Exec Council: Peter Bodenheimer, Doug Lin, Chris McKee, Richard Klein, Frank and me.

I actually met Frank way back in the summer of 1963 at an astronomy summer school at Columbia University for undergraduates, sponsored by NASA and the Goddard Institute there. However, I really got to know him at Berkeley where I had the extreme pleasure of working on a project with Frank, Susana Lizano, and Doug Johnstone. He and I shared an interest not only in astrophysics, but climate change, nuclear power, turning organic waste to char, baseball, poker, and good food. But of course, he was a master in all of these, and taught us all so much. It is a cliché but so true “He will be missed!”

Like several others, I was very fortunate to have been a graduate student for Frank Shu. He had an amazing way of explaining things very clearly. He knew just what the limits were of my knowledge of astronomy as a physics graduate student. Our work together had great influence on how I approached problems throughout my career. He had a way of making progress by analyzing the fundamental elements of a project and making just a few well justified assumptions. This is a challenging way to approach complex issues in astronomy. But Frank was an expert at dealing with such challenges which led him to make major advances in several areas. He had very powerful intuition. He would sometimes correctly guess a result before going through the detailed steps. He was helpful, supportive, and provided very valuable advice throughout my career. I always enjoyed dinner at Frank and Helen's homes. He was a great friend who I will miss.

Frank Shu was a giant in the field of star formation. He had a tremendous impact on the careers beyond those of many students and colleagues, including mine.

Frank Shu has been a great source of inspiration to me in many ways. My introduction to basic astronomy stemmed from his book "Physical Universe," which impressed me by its style, by not catering to the "lowest common denominator" and instead challenging "even the brightest undergraduate students". I have tried to adopt this philosophy in my own teaching. I also used his two books "Physics of Astrophysics" to teach graduate classes. I still remember some of his lectures that I attended, and was impressed by his passion and sense of joy ("the chondrule... gone with the wind".) When I shared my works on the stability of the inside-out solution and the corotation amplifier with him for feedback, he offered detailed comments and encouragement, which meant a great deal to me.

In 2002-2003, I had the opportunity to visit the National Tsing Hua University, where Frank had just become the president and wanted to establish a theoretical astrophysics center. I ended up in a car ride with him from Taipei to Hsinchu one evening, during which we had a conversation that left a strong impression on me. Frank said that the goal of theoretical astrophysics is not to explain all observations, but to gain insight. He gave an example: even if one could create a massive computer simulation that explains every detail of the Crab Nebula's spatial structure and emission, it would not be very useful because little would be learned. This comment has left long-lasting influence on my own research every since.

As a graduate student at the University of California at Berkeley, i was fortunate to be assigned an office next to Frank's corner office. He was not my thesis advisor, but for several years I had more interactions with him than with anyone else on the faculty. When he suddenly had an idea about his research (nearly every day), Frank had the habit to run out to the first available person to bounce it off to see if it made sense. Often, that was me. It didn't matter that I was "only" a grad student. We engaged in conversation about the idea, and he worked out some of the details with me. As a result, some of my first publications were with Frank and his student Steve Lubow (who has also contributed to this memorial). We developed a friendship over those years, and I always felt welcome in his office and home.

I was saddened to learn of Frank Shu's passing. We were dorm mates at MIT where we both participated in a number of activities including card playing and intramural sports. When one of the members of his badminton team became unavailable, Frank took me aside and taught me how to play competitive badminton. And I won my match! Even in badminton, Frank was an excellent teacher. Then I went over to watch Frank's match against a very good player from Indonesia. Frank lost.

I also remember Frank looking forward to the Jewish holiday of Passover. There were a lot of Jewish students in our dorm, so matzoh was available in our dorm's cafeteria during the holiday. It turns out Frank loved matzoh, which he called "matzoh crackers".

Frank was also very bright but in a very congenial way. Most people at MIT were very bright but many were not congenial.

After MIT, I lost touch with Frank, even though we both went to Harvard for our doctorates and earned them in the same year [1968], his in astronomy, mine in chemistry. We did not reconnect until 2013, by which time I had retired and Frank was pursuing research involving molten salt processes for carbon sequestration and nuclear energy. These projects involved a lot of chemistry, so our interests had converged! I served as his unpaid consultant until shortly before Frank's death.

Frank hadn't changed. It was a pleasure working with him. Frank had the rare gift of clarity of thought. He could make difficult concepts understandable.

He will be missed.

Frank played a huge role in the modern study of star formation. Before his work with Fred Adams, Susan Terebey and others, we had no real theoretical underpinning for our increasingly detailed observations. His models, with clear physical reasoning and testable predictions, provided a shaft of illumination into a dark area. While we know that things are more complex, his models are still relevant (I am running radiative transfer on a TSC model to compare to JWST data right now). But what we remember most about Frank was his enthusiasm, humor, and friendship. He was always ready to make fun of himself, as when he pretended to preach the gospel as the Rev. Sun Moon Shu at a meeting. The memory I like best, however, is Frank peeking at his cards, held close to his chest, as he prepared to relieve Doug Lin of his poker chips.

In Memory of My Dear Friend Frank Shu, Yuk Yung, 17 May 2023

I'm deeply saddened by the recent passing of my dear friend, Frank, at the age of 79. Our paths intersected several times throughout our lives, creating a unique bond between us.

1. A Distinguished Family from Wenzhou

Firstly, Frank and I both have roots in Wenzhou, a city located in China's Zhejiang province, approximately 300 miles south of Shanghai and 200 miles northwest of Taipei. The people of Wenzhou, known as the Wenzhounese, have a long history of emigration, establishing significant communities in many countries, including the United States, Italy, France, Spain, Australia, the Netherlands, Canada, and more recently in Africa.

Renowned for their entrepreneurial spirit, the Wenzhounese have thrived in business, particularly within retail and wholesale trade sectors. In Italy, they've significantly influenced the leather goods and textiles industries. In the United States, they're recognized for their involvement in a variety of businesses, from restaurants to retail shops. Language, a unique aspect of the Wenzhounese diaspora, has helped maintain tight-knit communities overseas. The Wenzhounese dialect, a variant of Wu Chinese, is particularly challenging for non-native speakers, including those from other parts of China.

Although Frank was born in Kunming, Yunnan province, during the War of Resistance against the Japanese, he didn't speak Wenzhounese. His family, however, held a distinguished status in Wenzhou. His grandfather served as acting mayor during the Republic of China (ROC). His father, a renowned scholar and math professor at Purdue University, later became the founding director of Taiwan's famous industrial park, the Hsinchu Science Park. Also known as Taiwan's Silicon Valley, it became a hub for the country's semiconductor and electronics industries, fostering the growth of major companies like TSMC and UMC. Frank, as we'll see, followed closely in his family's footsteps.

2. Academia Sinica Institute of Astronomy and Astrophysics (ASIAA)

During the 1992-1993 academic year, Frank and I both took sabbatical years in Taiwan. Frank focused his efforts on establishing ASIAA, while I assisted the Institute of Earth Science with Global Climate Change. We shared many experiences, from meals at the Academia Sinica Visitor Center's cafeteria to intense ping pong matches in the building's basement. Despite my best efforts, I could rarely best Frank, who was an exceptionally skilled player.

Frank's dedication to creating ASIAA was unparalleled. He tirelessly navigated challenges, negotiating with the President of Academia Sinica, a high-ranking government official, the Chair of the Physics Department at the National Taiwan University (NTU), and the overseas Chinese astronomers. His dedication was most evident in his commitment to teaching an Astronomy course at NTU based on his own classic textbook – and all in Chinese. His lectures, delivered with the precision and skill of a kung-fu master, were a highlight of my sabbatical year.

3. President of Tsinghua University

Frank's appointment as president of Tsinghua University (THU) was hardly surprising, given his father's previous tenure in the same role. I regret never having visited his Taiwan Institute of Advanced Research in Astrophysics (TIARA) during his presidency.

4. Energy

Frank's fascination with the nuclear energy that powers the sun (fusion) and Earth (fission) was palpable. He passionately explored nuclear and solar power as alternatives to fossil fuels. In 2011, I invited him to give a seminar on "Climate Change and Energy Solutions" at Caltech, during which he proposed a myriad of innovative ideas, from nuclear power to bamboo power. His talk was a resounding success, filling the large lecture hall in Cahill (Department of Astronomy) to capacity. As always, his approach was reminiscent of Bruce Lee's: deriving everything from fundamental principles. His lecture (attached) is a treasure trove of innovative ideas on energy.

Frank's vision was to create a Silicon Valley for Energy, a hub that could revolutionize our world's energy needs. The world needs these innovative and forward-thinking ideas more than ever.

Rest in peace, my dear friend! Your visionary contributions to academia and society have left an indelible mark, and you've helped put our beloved hometown of Wenzhou on the map. Your memory will continue to inspire and motivate us all.

當我剛升上大學時非常幸運，有機會參加吳健雄科學接受大師們學術洗禮。其中，徐遐生院士是那個營隊的講座大師。徐院士的演講讓我深刻體會到天文學之美及其背後的物理機制，啟發了我對天文研究的興趣和決心。他親自在我所穿的營隊T恤上寫下成為一位優秀科學家所必備的條件（並繪上一個恆星形成系統），這些條件一直是我努力追求的目標。多年過去了，我仍然牢記著徐院士的勉勵。雖然親愛的徐院士已離世，回歸宇宙、與他最愛的星星共處，然而他的智慧之光將永遠照耀著我們。作為後輩，我們將承接他留下的火炬，繼續探索宇宙的奧秘。

The first year Harvard astronomy grad students of Fall 2002...

I began to know Frank in the beginning of 2005, the 2nd half stint for him as president of Tsing Hua U, working in a very elegant office located at the heart of the campus site, 8F, known as TIARA, acronym for Theoretical Institute for Advanced Research in Astrophysics. Some years passed then he had a group of engineering people working on molten salt technology, also located on Tsing Hua campus, in a tin roof shelter, where he turned himself from a master theoretician to a head of engineers working on a construction site. There are so many stories in those years. One time, when the shooting team from the US was in Taipei on the road to Hsinchu. The molten salts pump was clogged and ceased to operate. We were supposed to do a demo, turning biomass to biochar in 20 minutes. Frank alone figured out the possible cause for the show stopper, the impurities of the industrial-grade salts from overheating. Tashun and Pofu worked around the clock, adding acetic acid little by little. Frank stayed in a Hsinchu hotel with them for several nights. Finally we did the demo successfully for the shooting team just in time. The video link is here. I can still remember the smiles Frank had and all the team members had, smiles in tears. There were other voices saying that we do all over. Against all odds, Frank insisted on staying with the existing salts. God stood on Frank's side. I try to imagine what it was like for Frank, leaving his well-established, world-known astronomy to bio-carbon research. He made a difficult decision, a seldom-trodden road.

我跟徐遐生院士的緣分

Frank Shu 於2023年4月22日逝於美國，他的學術成就，在大學時期就參與優秀的研究，從密度波，恆星形成，到晚期核反應器、碳中和技術，都面對大問題而有傲人成果，這些眾所周知。這裡我只記錄個人的接觸。徐院士比我長15歲，是學術巨擘，感覺上前輩很多，但平常還是以 Frank 稱呼。

跟Frank的第一道緣分是紐約石溪大學 (Stony Brook University)，當時全名是紐約州立大學石溪分校。我念博班的時候，就知道他1968年拿到哈佛大學博士後，就去石溪任教，查了網路說直到1973年，而我1983年才去，沒能當成他的學生。

Frank 在 UC Berkeley 時期，帶領一批海外華人天文學家規劃臺灣的天文學發展，從一張白紙開始，仿效美國的「十年規劃白皮書」(decadal planning), 找出課題優先順序，選定電波干涉術切入，這策略非常獨到，因為干涉儀可以逐步增加天線數量，卻大為提高觀測效率，讓臺灣快速進入領域的前沿。這批「顧問」建立了中研院天文所，英文 Academia Sinica Institute of Astronomy and strophysics 縮寫為 ASIAA, 念起來就是 ASIA-A，亞洲第一。我從博班末期開始參與，直到1992年中央大學成立天文所，我有了工作回到臺灣。當時亞洲鄰國都羨慕我們有海外學者，有如此卓越的領域規劃。後來 ASIAA 參與 BIMA、SMA、ALMA 一路下來，奠立了我國天文界在世界的口碑。

很多這些優秀的天文學者不只是 lip service，而有實際貢獻，例如當時已經在國內的 Typhoon Lee（李太楓）大力推動，以及後來中研院歷屆所長 Fred Lo （魯國鏞）、Paul Ho（賀曾樸）、Sun Kwok（郭新）、You-Hua Chu（朱有花），都功不可沒。

我從一個小老弟，站在這些巨人肩上，只怪自己跳不高，終究沒能看得遠。在中央大學跟著同事發展可見光與紅外天文觀測。當時 Frank 等人規劃除了電波天文設備，也「妥協」在鹿林放兩座兩米望遠鏡 Twin Optical Telescopes，一座進行光度測量，另一座取光譜，現在想起來就是 time domain astrophysics 的利基，可惜後來沒有實現。1992年當時中大劉兆漢校長，打電話到美國，跟我說要是我答應協助兩米望遠鏡計畫，他就簽聘書。多年後他在中研院當副院長，找我去院裡演講，開場就說這個故事，說還欠我個兩米望遠鏡。現在耽誤了多年的兩米望遠鏡並非當年那一個，我也從一開始就不贊成，因為深知上鹿林的工程實在艱鉅，直到目前還在找出路。碰到有人問「兩米望遠鏡怎樣了？」，我都說「還是兩米呀！」

我當老師第一年在1993年夏天帶學生去無錫參加恆星形成學校，那是我第一次去大陸，那個從小到大的禁地。那次活動請了很多大咖，把上課內容出書，成了經典教科書。結果學生跟我去程在香港轉機時遇到颱風，在候機室等了兩天。好不容易到了無錫，還沒享受完大師洗禮，就因為有個學生生病，必須立刻回台，除了機位問題，我需要額外現金，結果跟 Frank 「搶劫」了美金300元，算是他演講的代價。

Frank 還在美國的時候（他後來說一共退休了三次），趁來臺灣時我們合開恆星形成的系列課程，他教理論，我講觀測，值得我拿來說嘴。Frank 後來在清大當校長，從一開始有如孩童的中文，到後來可以演講。在我熟悉的恆星誕生領域，他跟博後、學生發展出來的學說成了經典。2008年我請他來所裡演講，他當時關注能源議題，鼓吹安全的核反應器，也思考如何從大氣中回收碳。聽他演講非常享受，除了幽雅英文，還有清晰思路，以一貫天文物理學者的訓練，用第一原理推論風力、水力、潮汐發電的極限，例如地表就這麼多風，這裡風被攔截用來發電，下風處就沒得用。真是做什麼、像什麼，令人佩服。

有次碰到 Frank，他說在這裡當了校長後，終於瞭解了臺灣教授受到的限制，也拍拍我的肩膀說發展自己的設備真的重要。他在美國去世後，我馬上想寫這篇文章，但記得有幾張（跟）他的照片，居然找了幾天沒找到。只有這兩張2012年他來中央大學演講。再來就是2021年，疫情期間我找理由問他核子反應器計畫進行得怎麼樣了，並沒有收到回信。去年審一個學術案子，讀到他寫的推薦信，算是最後聽到他的消息。幾個月前聽說他重病，所以知道哲人遠去，不算意外，但還是唏噓。

Frank一路好走

看到臉友Ken Chen的訊息，知道Frank Shu已經離開，去擁抱他最喜歡的宇宙。 我跟Frank在工研院時互動很多， 他是綠能領域的前指會委員，每半年要對他報告一次。他對我很客氣，意見都從基本物理出發， 很斯文聰明的一個人。

Frank大學部在麻省理工跟林家翹教授（CC Lin)做學士論文，一下子就一炮而紅。那是探討星雲螺旋結構的問題。 他後來的發展我不清楚，但回清大當校長，父子檔都在清華當過校長，一時成為美談。 聽說他不會中文，批閱公文十分不方便，大學校長當一任就不當了。

他在工研院給過一次演講，從物理的角度出發談綠能，結論好像是挺原子能的。只是後來他在清華成立公司，做生質能源，改作化工的工作，後來如何不得而知。

他是個溫文儒雅的學者，意見中肯，有時雖尖銳，但就事論事，挺讓人懷念的。希望他放在俗事，RIP，繼續擁抱星星。

後記： 臉友好奇為何這件新聞小。 我說這世界人來人往，彗星也來來去去，多少人在乎呢？ 許多時候，再有名，也沒那麼重要，地球得照轉，太陽得繼續升起。因此。在世間的一天，自己得快活一天，不要太糾結。