Alejandro Cristian Raga

Mexico

1959-2023

Obituary:

We regretfully mourn the early passing of our friend and colleague Alejandro ("Alex") Cristian Raga on July 20th, 2023. He was born in Buenos Aires (Argentina) on January 15th, 1959.
He obtained his bachelor's degree in physics from the University of Buenos Aires (Argentina, 1982). His postgraduate studies were carried out at the University of Washington (USA), obtaining his master's degree in 1984 and his PhD in 1985. He spent long periods as an academic visitor in the USA (1986-1988), Canada (1988-1991) and the United Kingdom (1991-1992) before taking on a position as a lecturer in Manchester (United Kingdom, 1993-1995). In 1995, he relocated to Mexico, becoming a member of the Institute of Astronomy (IA) of the National Autonomous University of Mexico (UNAM). Later, he joined the Institute of Nuclear Sciences (ICN) at UNAM (2001).
Alex was a restless and brilliant scientist. His main line of work was studying regions of star formation and developing computational tools to solve problems in gas dynamics, radiative transport, and chemical evolution, which were not only applied to astrophysics but were also valuable in geophysics and laboratory plasmas generated by lasers. Among his numerous achievements, Alex's most notable contribution was the development of the theory of variable jets ejected from newborn stars (Herbig-Haro or HH objects), which has become a fundamental framework for understanding these objects. Colleagues worldwide have recognized and utilized his work, publishing hundreds of articles that build upon his ideas and findings. He also actively used observational data from space telescopes (such as Hubble and Spitzer) to study star-forming regions. He was part of an international group to obtain and analyze some of the first observations from the new James Webb Space Telescope.
He took on an impactful and devoted role as a teacher at both the undergraduate and graduate levels at UNAM and other academic institutions. He taught courses on topics such as the Physics of the Interstellar Medium, Numerical Hydrodynamics, Radiative Processes, Stellar Atmospheres, and numerous Research Seminars. His many students throughout the years (including some of us) will never forget the joy and kindness he shared the vast expanse of his knowledge.
On the other hand, Alex has formed a dynamic research group dedicated to numerical astrophysics within the Department of Plasma Physics and Matter-Radiation Interaction at ICN, with strong bonds with many scientists overseas. Alex's unexpected departure leaves behind five researchers and tens of students who will keep this group going.
The outstanding quality and abundance of his research work earned him multiple awards over the years, including the Mexican Academy of Sciences Award (1998), the John Simon Guggenheim Memorial Foundation Scholarship (2000), the National University Award (2010, UNAM) and the TWAS award (World Academy of Sciences, 2018).
In addition to being an excellent scientist, we celebrate his joyful personality, sharp wit and playful humour, and kindness towards students and young researchers, to whom he always offered unwavering support. His friendship has marked us all.
We will miss your laughter, hugs, and advice. Rest in peace, dear Alex.
(Written by Fabio De Colle, Alejandro Esquivel, Ary Rodríguez, Juan Claudio Toledo-Roy, and Pablo Fabián Velázquez)