In this series of posts, we sit down with a few of the keynote speakers of the 230th AAS meeting to learn more about them and their research. You can see a full schedule of their talks here!
Professor Daniel Wang is an observer with the heart and mind of a theorist. A professor at the University of Massachusetts – Amherst, Wang’s research broadly centers on understanding the flow of matter and energy within galaxies. He uses observations across the electromagnetic spectrum to test theoretical predictions on topics ranging from plasma physics to compact objects to black hole accretion. At the AAS Austin meeting, his plenary talk will focus on the gas flows near the supermassive black hole at the center of the Milky Way.
Wang was born in China and grew up during the oppressive period known as the Cultural Revolution. Academic opportunities were extremely limited, but he did ultimately attend college near the end of the Revolution, where he showed an aptitude for and great interest in physics. He then came to the United States on the recommendation of a visiting American professor and attended Columbia University, where he began his graduate work studying viscosity in quark matter. Wang has gracefully pivoted between several topics within high-energy astrophysics over the years, following his curiosity to tackle various interesting problems. During graduate school he ultimately became involved with the Einstein Observatory, the first X-ray imaging satellite, and utilized data from it for his PhD on diffuse hot gas in the Large Magellanic Cloud. As his career continued, he began to incorporate observations at other wavelengths into his portfolio, such as radio to trace magnetic fields and cosmic rays, submillimeter and infrared to trace dust emission, and ultraviolet and optical to trace active star formation. Combining these observations allows him to compare the energy contributions of the various processes in galaxies in order to determine, for example, whether radiation, momentum input from supernovae, or magnetic fields dominate the feedback energy budget within a galaxy.
While on sabbatical at the University of Cambridge, Wang decided to tackle another new topic: gas accretion onto supermassive black holes. It is now believed that virtually all massive galaxies contain such objects at their centers, but not yet understood why a large fraction of them are not emitting bright radiation. Understanding this so-called “silent majority” is one important piece in the puzzle of galaxy evolution. The black hole at the center of the Milky Way, Sagittarius (Sgr) A* (pronounced “A-star”), is one such quiescent black hole, and its proximity makes it the ideal laboratory for testing accretion models. Wang combined analytic theory with x-ray spectroscopy to show that most of the gas infalling onto Sgr A* actually never reaches the very high temperatures predicted for accreting gas by certain theories, meaning that much of the gas must be expelled before actually reaching the black hole. He followed up on this result by conducting simulations to more carefully constrain the physical conditions near the black hole, in particular the angular momentum, and found that the observations could be explained if the powerful winds from the young stars orbiting near Sgr A* were a primary source of the accreting gas. He will talk more about this synthesis of theory, simulation, and multiwavelength observations at his AAS plenary talk.
Wang finds that working across many subfields in astrophysics gives him a unique perspective and reinvigorates his creativity. He also notes that techniques used in one field may be applicable to others, opening up potential discovery space. New observational facilities provide particularly ripe opportunities for groundbreaking science. “I always want to push the boundary of what you can do, or cannot do. Discovery mostly happens at the boundaries.”
His advice to students looking to pursue a career in research? 1. Pursue topics that you find the most interesting and fun; 2. focus on the process, not the results; and, perhaps most importantly, 3. work hard! “Perseverance is very important. Ultimately, success depends on three things: talent, hard work, and luck. But only hard work is [under] your control.”