 |
| Margaret Burbidge, linocut, 11" x 14" by Ele Willoughby, 2025 |
The #printerSolstice2425 prompt this week is iron, so after talking last week about how certain numbers of nucleons are "magic" as you grow increasingly large nuclei, this week, we're talking about how you do that: how you grow nuclei from a single proton to the largest naturally-occurring transuranic elements. Astrophysicist Margaret Burbidge is one of the people instrumental in building our understanding stellar nucleosynthesis, how nuclei are produced in stars and you and I are all stardust. She was the first author of a monumental scientific paper Synthesis of the Elements in Stars, which became known as B2FH from the initials of its authors: Margaret Burbidge, Geoffrey Burbidge (her husband), William A. Fowler and Fred Hoyle. The landmark paper, one of the most-influential in astronomy and nuclear physics, reviewed everything then known stellar nucleosynthesis, how elements are made, backed up the theory with astronomical and laboratory data and in further explained how elements heavier than iron are made and the abundances of the various elements. Generations of astronomers apparently used to joke that "the early Universe made hydrogen and helium, Burbidge, Burbidge, Fowler and Hoyle made all the rest." Elements up to iron can be built up by nuclear fusion, both slow and rapid neutron-capture, in stars and B2FH also explained how heavier elements are made. At the base of my print is a stellar absorption spectrum of the sort she gathered and used in arguments presented in B2FH and a cross-section of a supergiant star and how nucleosynthesis leads to a nested series of shells where increasingly heavy elements are burned as fuel producing new elements through fusion. The shells from outermost in are: hydrogen (H), helium (He), carbon (C), neon (Ne), oxygen (O), silicon (Si) and iron (Fe). Behind her is space with stars and galaxies to represent her observations.
Born in Davenport, UK, she was the sort of clever child who deduced that she was born exactly 9 months after the November 11 Armistice which ended the first world war, and concluded she was likely conceived when it was announced. Her father Stanley John Peachey was a lecturer in chemistry at the Manchester School of Technology (now part of the University of Manchester) and her mother Marjorie Stott Peachey had been one of his students. As a small child her father got a patent related to the vulcanization of rubber, which made him enough money to move to the family to London where he set up his own industrial chemistry lab. She was "star-struck" on a ferry trip over the English Channel at the age of 4, away from the bright lights of London, and by 12, she was reading astronomy textbooks by James Jeans, a distant relative of her mother. She and her younger sister Audrey were expected to pursue education and careers. She gained experience working in her father's lab, before his death when she was 17. She passed the university entrance exams a year early and thus had an extra year at her high school, taken under the wing of the science teacher, where she was given the run of the physics laboratory to perform her own experiments in electricity, magnetism and optics. This was a unheard of opportunity for a young woman in the mid-30s. She went to University College London (UCL) to study astronomy, where she graduated with her undergraduate with first class honours to little celebration with war looming in 1939. She studied spectroscopy at Imperial College and then she proceeded to pursue graduate school at the University of London Observatory. She split her time between her studies and fabricating optical instruments for the armed forces. Her 1943 thesis was on the spectrum of the star Gamma Cassiopeiae. Many of the men in the department were busy with war work, so she was granted more independence and responsibility than might otherwise have been the case. She made observations at Mill Hill observatory, in the cramped space, in the cold under the open dome while German bombs fell nearby. She never complained, being determined always in her work. “Those nights, standing or sitting on a ladder in the dome of the [J. G.] Wilson reflector [at Mill Hill] . . . fulfilled my early dreams,” she later recalled. Upon seeing a photographic plate of a spiral galaxy for the first time, she said it felt almost sinful to be enjoying astronomy so much and be employed as an astronomer.
Since women were denied access to Mount Wilson Observatory, (on the basis there was no women's bathroom), Margaret's 1945 application to use the telescope was rejected. She wrote about the experience that a “guiding operational principle in my life was activated: If frustrated in one’s endeavor by a stone wall or any kind of blockage, one must find a way around — another route towards one’s goal. This is advice I have given to many women facing similar situations.” She stayed on in London as Assistant Directory of the observatory.
She met theoretical physicist Geoffrey Burbidge who was in grad school at UCL in 1947 and the two were married in 1948. Their personalities and persons contrasted; Geoff was a large guy who enjoyed arguing pugnaciously whereas Margaret was petite and known for her demure, friendly but quiet demeanour. But he was supportive, loyal and good friends even with colleagues with whom he disagreed and her quietness hid her steely resolve. They were a good match and proved a symbiotic team. Her passion for astronomy was so strong she convinced him to switch to theoretical astrophysics and the two collaborated regularly throughout their subsequent careers. They moved to the US for jobs at observatories at Harvard and the University of Chicago (where Margaret was excited to attend a workshop held by Harold Urey and Maria Goeppert Mayer on the abundance of the elements), before returning to the UK. Seeking two positions and telescope accessed required them to move repeatedly. Willy Fowler recalled a "wonderful Charles Laughton replica," that is Geoff looking and sounding like the famous British-American actor, walked into his office, where he was on sabbatical at Cambridge and said, "why don't you work on problems important for astrophysics?" Hoyle had been working on nuclear reactions in stars since before WWII. When Fowler returned to the US he recommended the Burbidges accompany him; Fred Hoyle was already a frequent visitor. Margaret could work at the Mount Wilson Observatory and Geoff at CalTech. But the Director of Mount Wilson wrote to say the single toilet precluded hiring a woman, still, ten years after her application to do a post-doc there. So, ever-pragmatic, they swapped jobs; Geoff took the Mount Wilson job and Margaret the one at CalTech. She had to pose as Geoffrey's assistant every time he purported went to Mount Wilson and live on a separate cottage on the grounds, as a means to gain access. Geoff worked in the dark room and smoked cigars while Margaret did the observing at night. It took until 1965 for Mount Wilson to officially allow women observers. Once in California they worked on their famous 108-page paper with Fowler and Hoyle, after having first collaborated while at Cambridge. The Burbidges had been looking at spectra of stars with unusual surface conditions; these could be due to upward mixing of nuclear reaction products and proved useful in the paper. They suspected neutron-capture. Fowler's nuclear physics group had been calculating cross-sections of reactions necessary to build heavier elements. Margaret wrote the paper while pregnant. The paper showed how elements were formed at various stages of the lifecycle of stars, explained the existence of of all but the lightest elements (which we now know were in fact formed in the Big Bang) and showed how we, and everything but some of those lightest elements are made of stardust.
They had a daughter, Sarah, in 1956. In 1962 they were both hired by UCSD; to get around anti-nepotism rules, Geoffrey was hired by the physics department and Margaret was hired by the chemistry department, until the rule was changed and she too joined the physics department.
Though her observations helped provide evidence of the Big Bang, Margaret and Geoffrey both followed Fred Hoyle into the "steady state" camp, and were skeptical of the Big Bang theory. Hoyle in fact had derisively coined the term "Big Bang" to poke fun at the idea. His idea was that maker was more or less continuously in a steady state. created and density remained constant. Nonetheless, the name Big Bang stuck and the theory is now become accepted by the field at large. Though Margaret, the observational astronomer, unlike Geoff, rarely commented on theoretical matters, so she is not strongly associated with choosing the wrong side of the Big Bang versus Steady State cosmology debate. She rather worked to keep an open mind.
In the '50s and '60s she measured flat rotational curves for spiral galaxies based on optical observations. Later Vera Rubin got similar results and was able to infer the existence of dark matter galactic haloes. In the '60s and '70s she worked on galaxies and quasars, helping to determine their distance, luminosity and internal processes, finding the most distance object then known (which remained the most distant known object for a decade). With access to the Lick Observatory telescope she was in the right place to join the race to find new and more distant quasars, and known for literally racing to work in the couple's 1961 Jaguar Mark II. Geoff on the other hand never learned to drive, though they both loved that car. Margaret's work on quasars was very important and lead to advancements like the understanding that galaxies have black holes at their centres. The shear distance to these objects was another blow to Geoff's favoured Steady State model; the expansion of the universe due to the Big Bang was needed to explain objects at the cosmological distances.
In 1972 she declined the American Astronomical Society's Annie Jump Canon Medal because it is only awarded to women. She wrote, “It is high time that discrimination in favor of, as well as against, women in professional life be removed.” This sparked conversation and forced the AAS to look into discrimination on the basis of sex for the first time and lead eventually to the formation of the AAS Committee on the Status of Women in Astronomy. They also changed the rules of the Annie Jump Canon Medal, awarding it only to early career women who choose to apply for it.
Burbidge was director of the Royal Greenwich Observatory (1972–1973), She was the first woman in any of these roles. She was notably, the first director of the Royal Greenwich Observatory in 300 years who was not made the Astronomer Royal (and the title was bestowed instead on one of her male peers). At various times she attributed this to sexism or a political desire to reduce the influence of the Royal Greenwich Observatory; either way she resigned after 18 months. She was president of the American Astronomical Society (1976–1978), and following her election, she took US citizenship. As president, she got to introduce the first woman to receive the Russel Lecture Award for lifetime excellence in astronomical research: Cecelia Payne-Gaposchkin. Burbidge herself later received the award in 1984. When the US Equal Rights Amendment (ERA) was introduced, but failed to pass in the required minimum of 38 states, Margaret proposed that AAS meetings be banned in states which had not passed the ERA. The proposal was contentious but she succeeded in having it passed. In the '80s and '90s she worked on the development and use of the Faint Object Spectrograph on the Hubble Space Telescope. She was president of the American Association for the Advancement of Science (1983). In 1983, Fowler received the Nobel Prize for his work on stellar nucleosynthesis and expressed his surprise that Burbidge was not included; she of course was circumspect and did not comment. She was the first female president of the International Astronomical Union's commission on galaxies. She was the first woman to win the Bruce Medal. She was awarded the Medal of Science by President Reagan in 1985, was a fellow of the Royal Society, and the Gold Medal from the Royal Astronomical Society. Burbidge was the first director of the Center for Astronomy and Space Sciences at UCSD and worked there until retirement in 1988. Fowler died in 1995. Hoyle died in 2001. Geoffrey died in 2010. Margaret was the sole surviving author of B2FH, until her death at age 100 in 2020 after a fall. She had been one of the great observational astronomers of the 20th century, a role model and trail blazer for women in the field and a strong voice for eliminating bias against women that she had faced in her career.
References
Alpha process, Wikipedia, accessed January, 2025
B2FH, Wikipedia, accessed January, 2025
Burbidge, E. Margaret, Geoffrey Burbidge, William A. Fowler, and Fred Hoyle, Synthesis of the Elements in Stars, Reviews of Modern Physics, vol 29, 4, October, 1957.
Clark, Stuart. Margaret Burbidge Obituary. The Guardian. April 22, 2020.
Cohen, Adam D. In Memoriam: Margaret Burbidge, Pioneering Astronomer and Advocate for Women in Science. American Association for the Advancement of Science, April 8, 2020.
Dillon, Cynthia. Trailblazing astronomer Margaret Burbidge turns 100 years old. University of California. October 17, 2019.
Margaret Burbidge, Wikipedia, accessed January, 2025
OstrikerFreeman Kenneth ; Eleanor Margaret Burbidge. Physics Today 1 September 2020; 73 (9): 60. https://doi.org/10.1063/PT.3.4575
Rubin, Vera C. E. Margaret Burbidge, President-Elect. Science. Vol. 211, Issue 4485, pp. 915-916, DOI: 10.1126/science.7008193 February 21, 1981.
2021Eleanor Margaret Burbidge. 12 August 1919—5 April 2020Biogr. Mems Fell. R. Soc.7111–35http://doi.org/10.1098/rsbm.2021.0017Skuse, Ben. Celebrating Astronomer Margaret Burbidge, 1919-2020. Sky & Telescope. April 6, 2020
Smith, Harrison. Margaret Burbidge: Pioneering astrophysicist who showed we are all made of stardust. The Independent. April 22, 2020.
Stellar nucleosynthesis, Wikipedia, accessed January, 2025
Trimble, Virginia. E. Margaret Burbidge (1919-2020). Nature. April 27, 2020.
No comments:
Post a Comment