Donald D. Clayton

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Donald D. Clayton

Donald Delbert Clayton (born 1935) is an American astrophysicist. His published works lay foundations for five subfields of astrophysical research: (1) the assembly by nuclear reactions inside of stars of the nuclei of the chemical elements from hot atoms of hydrogen and helium; (2) astronomy of gamma-ray lines emitted by radioactive atoms ejected by exploding stars; (3) growth of the galactic abundances of the chemical elements, especially of their radioactive nuclei, owing to birth and death of stars during the aging of the Milky Way galaxy; (4) predicting new astronomy based on the relative abundances of the isotopes of the elements measured in solid dust grains that condensed from hot gases while those gases were being ejected from stars; (5) condensation of solid carbon grains within hot, radioactive supernova gases containing more oxygen than carbon atoms. Clayton spearheaded these subfields of astronomy. He published his research works from positions at California Institute of Technology(1956–63), Rice University (1963-89), Cambridge University (1967–74), Max-Plank Institute for Nuclear Physics (1977–83), and Clemson University (1989-2014) during an international academic career spanning almost six decades (1956–2014). In 2007 Clayton retired, becoming Emeritus Professor of Physics and Astronomy at Clemson University. He remains an active researcher with two new published research papers in 2013.[1][2] Clayton has also authored three books outside of pure science : a novel The Joshua Factor (1985), a parable of the origin of mankind and the mystery of solar neutrinos; a late-career science autobiography, Catch a Falling Star;[3] and an early-career memoir The Dark Night Sky,[4] of interest because Clayton has said that he conceived of it in 1970 as layout for a movie[3]:249 with Italian filmmaker Roberto Rosselini [5] about the cosmological life (See PERSONAL below). On the web Clayton has published Photo Archive for the History of Nuclear Astrophysics from his personal photographs and researched scientific captions, recording history as he lived it doing research in nuclear astrophysics.[6]

National honors[edit]

Clayton was elected to Phi Beta Kappa during his third year as a student at Southern Methodist University. He was awarded many supporting fellowships: National Science Foundation Predoctoral Fellow (1956–58); Alfred P. Sloan Foundation Fellow (1966–68); Fulbright Fellow (1979–80); Fellow of St. Mary's College, Durham University (1987);[14] SERC Senior Visiting Fellow, The Open University, Milton Keynes, U.K. (1993). In 1993 Clayton was named Distinguished Alumnus of Southern Methodist University,[15] 37 years after his BS degree there.

Early life and education[edit]

Donald D. Clayton was born on March 18, 1935 in a modest duplex on Walnut Street in Shenandoah, Iowa while his parents were there seeking work during the Great Depression. They were temporarily away from their family farms near Fontanelle in Adair County in southwestern Iowa, farms to which they returned often during the next five years. Clayton thereafter spent much of his childhood on those farms, and he has rhapsodized over his love of the farm.[3]:1–6 Young Clayton attended public school in Texas, however, after his father's new job moved them to Dallas in 1940 to pilot for Braniff Airlines. Fortunately, his parents obtained a home in the already renowned Highland Park School System, providing him an excellent education. Clayton's own words describing his advantage from High School are here.[16] He graduated third in his 1953 class of 92 students[17] from Highland Park High School. The first among his entire extended relations, including his father, to attend any university, Clayton matriculated and excelled in physics and mathematics, graduating from Southern Methodist University summa cum laude in 1956. At his professor's urging he was accepted as a physics research student by California Institute of Technology (Caltech), which he attended bearing a National Science Foundation Predoctoral Fellowship. In the 1957 nuclear physics course at Caltech Clayton learned from William Alfred Fowler about a new theory that the chemical elements had been assembled within the stars by nuclear reactions occurring there. He was captivated for life by that idea. Nuclear reactions within stars and their structure became his muse.[4]:112–114 During 1961 Clayton completed his Ph.D. Thesis on the abundance evolution of the elements owing to slow capture of free neutrons, the s process, in stars. At Caltech, Clayton and his wife Mary Lou [18] played a small role in producing The Feynman Lectures on Physics by converting the taped audio of Feynman's lectures to written prose. At Caltech Clayton had the chance to meet and become a lifelong friend of Fred Hoyle, British cosmologist and creator of the nuclear theory of chemical-element formation inside of stars. Clayton's collaborations with Fowler (1983 Nobel Laureate in Physics) as Fowler's[19] research student (1957–60) and as Fowler's post-doc (1961–63) launched Clayton's scientific career. Clayton established himself while at Caltech as a post-Hoyle leader of nucleosynthesis within the stars by calculating the first time-dependent models of both the slow and the fast neutron-capture chains of heavy-element nucleosynthesis and of the nuclear abundance quasiequilibrium that establishes the abundances between silicon and nickel during silicon burning in stars. He came onto the field early, at a time when nucleosynthesis was a vibrant, modern topic. Citations to this work are in the Nucleosynthesis section below.

Academic history[edit]

Following a two-year (1961–63) postdoctoral research fellowship at Caltech, Clayton claimed an Assistant Professorship as one of the four founding faculty members in Rice University's newly created Department of Space Science (later renamed Space Physics and Astronomy). There he initiated a graduate-student course explaining nuclear reactions in stars as the mechanism for the creation of the atoms of the chemical elements. His textbook based on that course ( Principles of Stellar Evolution and Nucleosynthesis, McGraw-Hill 1968) earned ongoing praise. Today, 47 years after its first publication, it is still in common usage[20] in graduate education throughout the world. Clayton was awarded the newly endowed Andrew Hays Buchanan Professorship of Astrophysics at Rice in 1968 and held that endowed professorship for twenty years until moving to Clemson University in 1989. At Rice University in the 1970s, Clayton guided Ph.D. theses of many students who achieved renown, especially Stanford E. Woosley, William Michael Howard, H. C. Goldwire, Richard A. Ward, Michael J. Newman, Eliahu Dwek, Mark Leising and Kurt Liffman. Senior thesis students at Rice University included Bradley S. Meyer and Lucy Ziurys, both of whom forged distinguished careers in the subjects of those senior theses. Good historical photos of several students can be seen on Clayton' s photo archive for the history of nuclear astrophysics.[21]

In 1966 letters from W.A. Fowler's office unexpectedly invited Clayton to return to Caltech in order to coauthor a book on nucleosynthesis with Fowler and Fred Hoyle. In his autobiography Clayton quotes these letters.[22] He accepted; but while resident at Caltech Clayton was invited by Hoyle to Cambridge University (UK) in spring 1967 to advise a research program in nucleosynthesis at Hoyle's newly created Institute of Astronomy. The award to Clayton of a prestigious Alfred P. Sloan Foundation Fellowship (1966–68) facilitated leaves of absence from Rice University for this purpose. Clayton exerted that research leadership in Cambridge during 1967-72 by bringing his research students from Rice University with him. That prolific period ended abruptly by Hoyle's unexpected resignation in 1972.[23] Clayton was during these years a Visiting Fellow of Clare Hall. S.E. Woosley, W.M Howard and Raymond J. Talbot accompanied Clayton from Rice to Cambridge during this period, and joined there William David Arnett, who was assuming in 1969 at Rice University his first faculty position. During 1969-74 Arnett, Woosley, Howard and Clayton published jointly numerous innovative studies on the topic of explosive supernova nucleosynthesis.[24] During his Cambridge years Clayton proposed[25] radioactive gamma-ray-emitting nuclei for gamma-ray astronomy of line transitions from radioactive 56Ni nuclei with coauthors (Stirling Colgate, Gerald J. Fishman, and Joseph Silk). The detection of these gamma-ray lines two decades later provided the decisive proof that iron had been synthesized in supernovae in the form of radioactive nickel isotopes rather than as iron itself, as Fowler and Hoyle both advocated. That paper was designated one of the fifty most influential papers in astronomy during the twentieth century[26] by the American Astronomical Society.

During the seven-year period (1977–84) Clayton resided about 1/3 time at the Max Planck Institute for Nuclear Physics in Heidelberg as Humboldt Prize awardee on multiple academic leaves from Rice University. There he joined the Meteoritical Society seeking audience for his newly published theoretical picture[27] of a new type of astronomy based on relative abundances of the isotopes of the chemical elements within interstellar dust grains. He hoped such interstellar grains could be discovered within meteorites;[28] but he also advanced a theory that he called cosmic chemical memory [29] by which the effects of stardust can be measured in meteorites even if stardust itself cannot be found. Clayton designated the crystalline component of interstellar dust that had condensed thermally from hot and cooling stellar gases by a new scientific name, stardust. Stardust became an important component of cosmic dust. Clayton has described[30] the stiff resistance encountered from meteoriticist referees of his early papers advancing this new theory. He nonetheless established that research program at Rice University, where he continued guiding graduate-student research. Following laboratory discovery of stardust bearing its unequivocal isotopic markers, Clayton was awarded the 1991 Leonard Medal, highest honor of the Meteoritical Society, sixteen years after the refereeing battles of his first papers on stardust. Feeling vindicated,[31] Clayton exulted in Nature "the human race holds solid samples of supernovae in its hands and studies them in terrestrial laboratories".[32]

In 1989 Clayton surprised academia by accepting a professorship at Clemson University in order to develop and guide a graduate research program in astrophysics there.[33] This academic segment of his career (1989–present) focused initially on hiring three young astrophysicists [34] and their joint research with the Compton Gamma Ray Observatory, which was launched in 1991 after several delays and whose instruments successfully detected gamma rays identifying several of the radioactive nuclei that Clayton had predicted in exploding stars. Clayton had already been named Co-Investigator on the NASA proposal for the Oriented Scintillation Spectrometer Experiment OSSE, one of the four successful instruments carried into orbit by Space Shuttle Atlantis. Simultaneously Clayton developed at Clemson his program of stardust research featuring annual workshops.[35] The initial NASA sponsored workshop at Clemson University in 1990 was so lively that it was repeated the next year jointly with Washington University (St. Louis) cosponsorship, and in later years sponsored also by the University of Chicago and by the Carnegie Institution of Washington. These workshops featured the excitement of new discoveries, but also helped participants focus their ideas for annual personal submission of abstracts to NASA's Lunar and Planetary Science Conference. Otherwise their discussions were not shared or publicized. Yet another new goal for Clayton became to assemble from his large personal collection of professional photographs a web based display of an archive for the history of nuclear astrophysics[36] and to donate the originals [37] to the Center for the History of Physics.[38] Following his retirement from academic duties in 2007, Clayton published a scientific autobiography,Catch a Falling Star.[3] Although autobiography is frowned upon by professional historians as reliable scientific history, it can nonetheless offer unique insights into life on the science frontier, as is the case here. Clayton claims to have taken precaution in his autobiography against the known human weakness for rewriting memories to better fit one's evolving self-image, stating: "I try to diminish its force by heavy reliance on my diaries and on my photo albums".[39] Clayton's published refereed research papers are listed at


Clayton married three times, first in 1954 in Dallas[40] to Mary Lou Keesee (deceased 1981, Houston) while they were students at SMU;[41] second, in 1972 in St. Blasien he married in Germany a young German woman, Annette Hildebrand, while residing in Heidelberg (divorced 1981, Houston).[42] Clayton remarried in 1983 in the Rice University Chapel the former Nancy Eileen McBride,[43] who was trained in art and in architecture and is today an artist.[44] Clayton's life as Assistant Professor at Rice University 1963-66 was devoted to buying a family home, schooling for his children, and to building his academic experience and credentials.[45] He was promoted through the academic ranks at Rice, until 1989 when he transferred to a professorship at Clemson University in South Carolina, residing today with Nancy in historic G. W. Gignilliat House (1898) in Seneca, South Carolina (pop. 8,000), seven miles from the city of Clemson. They jointly have one son (Andrew), born in 1987 in Houston. Clayton's three previous children arose from his earlier marriages. A son (Donald Douglas Clayton b.1960, Pasadena CA) lives in Houston and a daughter (Alia Clayton Fisher b.1977, Houston) lives with her husband and four children in Longmont, Colorado. Another son, Devon Clayton (b. 1961 Pasadena), died in 1996 in Seneca SC. Clayton has one brother and two sisters, each still resident in Texas, two of them also born in Iowa. Clayton's mother was born on a farm in Fontanelle IA to parents (Kembery and Keisel)[46] that had lived their entire lives on Fontanelle farms. Their own parents had immigrated to Iowa near 1850, one from England (Thomas Kembery) and one from Germany (William Keisel). Clayton's father was also born on a Fontanelle farm to English parents (Paul Clayton and Verna Porter) having one Dutch grandparent (Yerkes). Two of Clayton's great grandfathers (Kembery and Clayton) fought in the Civil War (North). Robert M. Clayton fought in Sherman's Army at the battle of Atlanta.[47] In 1969 at Rice University Clayton was introduced by patron of the arts Dominique de Menil to Italian filmmaker Roberto Rosselini, and they conceived of a film about one scientist's deepening realizations during a cosmological life, a sequence of experiences which Clayton proposed [48] to provide for that project. In summer 1970 he spent two weeks in Rome working daily with Rosselini [5][49] on that effort, which failed owing to insufficient financial support or to insufficiently theatrical plan.[50] Clayton's published memoir "The Dark Night Sky: a personal adventure in cosmology"[51] laid out his plan for that film.

Citations of research leadership[edit]

Donald D. Clayton's research innovations in astrophysics and planetary science lay in the following five disciplines. The location of Clayton's written history of each within his autobiography, Catch a Falling Star,[52] is referenced at the ends of each. The references within each discipline are to noteworthy seminal published papers by Clayton (names of his co-authors are in his publication list),[53] or to supporting facts. Clayton's independent style is evident from his publication list, being author of an unusual 120 single-author research papers, the latest in 2013.[54] Sole-author research papers are relatively rare in astrophysics.

Nuclear physics origin of the chemical elements (Nucleosynthesis)[edit]

Clayton calculated the evolution in time of isotopic abundances owing to irradiation by free neutrons for both the S-process and the R-process of heavy-element stellar nucleosynthesis defined by B2FH.[55] His two 1960s papers showed that the known abundances require that they were created as mixtures of distinct abundance patterns caused by differing intensities of neutron irradiations.[56] They established Clayton in nucleosynthesis by providing standard models that were useful for four decades of progress on neutron-capture processes. In 1967 Clayton turned to the supernova origin of the abundances of the elements that can be created in stars from only their hydrogen and helium. Those primary nucleosynthesis nuclei having atomic weights between silicon and nickel (A=28-62) are much more abundant than s-and-r process nuclei. To rationalize the abundance structure of this mass region he advanced a new conceptual tool that he named nuclear quasiequilibrium during silicon burning.[57] That concept explained the observed numbers of isotopes in the A=28-62 mass range, which had previously been a mystery.[58] Of extreme importance to the future of astronomy, Clayton demonstrated that supernovae, within which the quasiequilibrium occurs, should be profoundly radioactive because nucleosynthesis between atomic weights A=44-62 is overwhelmingly of radioactive nuclei.[59] Quasiequilibrium maintained that even the mountain-like abundance peak at iron was synthesized as radioactive nickel parents in the supernovae explosions rather than as iron directly.[60] This discovery initiated Clayton's long and productive focus with radioactive isotopes ejected from supernovae, leading to his predictions of both gamma-ray line astronomy [61] and of radioactive grains condensed from hot supernova gases.[62] Experimental confirmation about fifteen years later of those predictions spurred two new fields of astronomy and brought Clayton high honors. A prolific five years with Rice University colleagues W. David Arnett, Stanford E. Woosley and W.Michael Howard studied explosive nucleosynthesis caused by the supernova shock wave.[63] Scientific leadership of nucleosynthesis appears to have shifted by 1975 from Hoyle in Cambridge and Fowler at Caltech to Rice University. During the years 1967-72 Clayton resided half time in Cambridge U.K. at Hoyle's invitation[64] to advise a nucleosynthesis program at Hoyle's newly constructed Institute of Theoretical Astronomy. Clayton did this during 1967-72 by bringing his graduate students at Rice with him to Cambridge. Hoyle later made three research visits with Clayton at Rice University [65][66] following his dramatic 1972 resignation from Cambridge University. After Clayton's 1989 move to Clemson University, his research with Bradley S. Meyer showed how the uniquely puzzling 48Ca isotope of calcium had become so abundant in the Galaxy [67] owing to a relatively rare form of Type Ia supernovae in which the appropriate neutron-enriched quasiequilibrium occurs. That collaboration later explained how the odd-mass A=95 and A=97 isotopes of the element molybdenum had become dominant in supernovae stardust,[68] thereby explaining a riddle in the observed stardust isotopic abundances. Clayton published in book form a spirited glimpse of nucleosynthesis for scientists outside of nucleosynthesis research.[69] Fred Hoyle's creation of the theory on nucleosynthesis in stars was overlooked and forgotten after he fell into science disfavor over his views of interstellar biology; therefore Clayton published two historical papers reestablishing consciousness of Hoyle's great achievement.[70] See chapters 7, 9 and 18 in Catch a Falling Star

Gamma-ray-line astronomy of radioactive nuclei in supernovae[edit]

Clayton and coworkers' discovery motivating gamma-ray-line astronomy [71] as an empirical test of explosive nucleosynthesis in stars was recognized in the American Astronomical Society Centennial Volume [13] as one of the 50 most influential astrophysics papers of the 20th century. Observational discovery of those gamma rays not only confirmed nucleosynthesis theory but also recast mankind's understanding of the radioactive nature of supernovae. It is probably the innovation for which Clayton is best known. His NASA-funded research exploring that theme at Rice University during the 1970s uncovered several additional nuclear prospects for that high-energy spectroscopic astronomy, which is based on the recognizable energies of gamma rays emitted by radioactive nuclei that are being ejected from supernovae. Today it has blossomed with observational results after quickly becoming a goal for future space astronomy missions, especially when Compton Gamma Ray Observatory was being proposed to NASA in 1977 (launched by shuttle Atlantis in 1991). Hopes were raised by optical astronomers' discovery in February 1987 of a nearby supernova called SN1987A, hopes described by Clayton from his 1987 sabbatical office at Durham University owing to mounting excitement generated by observed X-ray emission from its supernova surface.[72] Supernova 1987A was to provide several exciting detections of gamma-ray lines, thereby establishing this new field of astronomy. CGRO, the space gamma-ray telescope that detected several of those predicted gamma-ray lines, was the second of NASA’s Great Observatory missions. In 1977 Clayton was named Co-Investigator for the NASA-approved proposal for the OSSE instrument on CGRO. Clayton summarized in 1982 the physical expectations for several gamma-ray-line emitting young nuclei.[73] Key to the most intense radioactivity was Clayton's discovery that rapid-silicon-burning nucleosynthesis between silicon and nickel was dominated by abundances of radioactive alpha-particle nuclei, those synthesized nuclei having equal numbers of protons and neutrons.[74] Clayton has quipped that SN explosions are "the largest nuclear accidents of all time". Even abundant iron of our world was synthesized as a daughter of radioactive nickel.[75] Modern studies of supernovae are dominated by their intensely radioactive natures. His pioneering leadership earned for Clayton NASA's 1992 Exceptional Scientific Achievement Award. Both the OSSE instrument and the Comptel instrument aboard CGRO confirmed predictions.[76] Clayton's earlier research of this field in 1965 had derived from an idea based on the r process;[77] but r-process radioactive nuclei are much less abundant in supernovae than are the radioactive nuclei fused during silicon-burning. So it was the latter that became a stronger source of radioactive nuclei. These discoveries inspired by Clayton's publications changed forever the study of supernovae. Chapters 8, 11, 17 and 18 in Catch a Falling Star.

Astronomy of Stardust[edit]

Clayton introduced a new astronomical discipline based on the relative abundances of the isotopes of those atoms of chemical elements that had condensed into tiny solid grains within the hot gases leaving stars. Clayton named these solids stardust,[78] a component of Cosmic dust found a decade later to be distributed within meteorites. Stardust inherited its unusual isotopic compositions from the evolved nuclear composition of the host stars within which they condensed. His arguments became foundational because they guided the creation of a new field of astronomy after stardust was experimentally discovered. Clayton's 1970s papers [79] predicted isotopic abundance ratios to be expected in stardust, which Clayton envisioned as being ubiquitous among the interstellar dust grains and subsequently, perhaps, found within meteorites or other samples of interstellar matter. Most breathtaking were Clayton's predictions of excessive isotopic abundances within supernova-condensed solid stardust grains of the daughters of the abundant radioactive nuclei within the supernova ejecta gases.[80] These papers initially encountered incredulity in the field of cosmochemistry; nonetheless, R.W. Walker and E. Zinner at Washington University undertook instrumental development that might prove capable of measuring isotope ratios in such tiny solids.[81] Almost two decades of experimental search were required before intact stardust grains, (also called presolar grains by meteoriticists), were successfully isolated from the vast remainder of other presolar dust particles.[81] These tiny grains were successfully extracted from meteorites and measured by precision laboratory techniques, especially by Secondary ion mass spectrometry (SIMS), for the isotopic compositions of their chemical elements. Such dramatic experimental discoveries in the 1990s, led primarily by Ernst Zinner and his colleagues at Washington University (St. Louis)[82] confirmed the stunning reality of this new astronomy; namely, solid particles that condensed within stellar gases, gases that had cooled long before the earth was created, are today handled in laboratories on earth. These tiny stones are quite literally solid pieces of long dead stars. The discovery experiments dispelled skepticism that had surrounded Clayton's predictions, causing him to be awarded [8] the 1991 Leonard Medal of the Meteoritical Society. Main themes of this astronomical science have been summarized in 2004 by Clayton & Nittler.[83] To debate the meaning of the frequent new discoveries, Clayton at Clemson University initiated in 1990 an annual series of workshops cosponsored jointly[84] with Ernst Zinner and his colleagues at Washington University (St. Louis), where presolar stardust particles were being documented in the laboratory by SIMS.[85] Clayton remains a leader in the interpretation of stardust.[86] He has interpreted the puzzling silicon isotope ratios in the presolar Asymptotic giant branch stars, the stars that have demonstrably been the donors of the known presolar mainstream silicon carbide stardust grains to the solar cloud, as having been born from a merger of the Milky Way gas with the interstellar gas in a smaller satellite galaxy possessing a lower gaseous isotopic abundance ratio for 30Si/28Si [87] owing to its lesser degree of galactic abundance evolution. Chapters 14 and 15 and pages 504-508 in Catch a Falling Star

Galactic abundance evolution of radioactive nuclei[edit]

Clayton devised key concepts for the interstellar abundances of radioactive nuclei in the Galaxy. In 1964 Clayton discovered a new method for measuring the age of interstellar nuclei based on the larger than expected observed abundances of the stable daughters of radioactive nuclei.[88] The decays of rhenium-187 to osmium-187 and of uranium and thorium to three differing isotopes of lead (Pb) defined the new cosmoradiogenic chronologies. Merging his method with an earlier method based only on the abundances of uranium and thorium themselves[89] still did not yield a precise galactic age, however. Clayton reasoned[90] that the main discord arose from inadequate treatments of both the history of star formation in the Galaxy and of the rate of infall of pristine gas onto the young Milky Way, compounded by a prevailing but erroneous technique for computation of the radioactive abundances within interstellar gas. Clayton argued that existing stars contained older nuclei on average than those in the interstellar gas, which contains higher concentration of younger radioactive nuclei than do the stars. With that insight, Clayton invented in 1985 new mathematical solutions for the equations of galactic abundance evolution that for the first time rendered these relationships transparent.[91] Clayton calculated an age of 13-15 billion years for the oldest galactic nuclei,[90] which would necessarily be approximately equal to the age of our galaxy. Radioactive cosmochronology has recently diminished in importance as more accurate techniques for determining the age of the Milky Way have been discovered; but agreement confirmed correctness of radioactivity treatment in astronomy. Clayton's mathematical models demonstrated that the concentration of short-lived radioactive nuclei in the interstellar gas had routinely been theoretically underestimated by a factor 1/(k+1), where k is an integer near 2 or 3 that measures the steepness of the rate of decline of the infall of pristine gas onto our galaxy.[92] Meanwhile, the identities and initial abundances of the shorter-lived radioactive nuclei that were still alive at varying levels within the interstellar gas cloud that formed the early solar system but which are now dead has grown in importance with more experimental discoveries of such nuclei within meteorites. These are called extinct radioactivities. Simultaneous solution for the abundances of each became the guiding principle for a new discipline of galactic abundance evolution that focuses on nucleosynthesis near the solar interstellar cloud during the billion years preceding solar birth.[93] In 1983, at a time when astrophysicists were considering only a uniform model of a well mixed interstellar gas, Clayton introduced a new aspect of the ISM that is essential for understanding the abundances of the extinct radioactivities. He advocated the importance of time required for isotopic mixing between the ejecta of freshly synthesized atoms from supernovae and the distinct physical phases of interstellar gas. He showed that owing to those time delays allowing decay of radioactive nuclei, each phase of interstellar gas contains a distinct average concentration of each of the extinct radioactive nuclides, but that the early solar system radioactivities reflected the dense molecular-cloud phase[94] in which the solar system was born. In the 21st century many researchers have begun to present their own calculations of the effect of interstellar inter-phase mixing,[95] sometimes not citing Clayton's (1983) paper owing to intervening decades. These aspects of phase mixing will remain important for decades to come while astronomers probe the circumstances of solar birth using the precious data revealing the abundances of the extinct radioactive nuclei. Clayton therefore gave emphasis to extinct radioactivity in the Glossary of his 2003 book on isotopes in the cosmos.[96] See also Chapters 16 and 17 of "Catch a Falling Star".

Condensation of carbon solids from oxygen-rich supernova gas[edit]

Clayton advocated that supernova carbon stardust (which in 1977 he had named [97] SUNOCONs (for SUperNOva CONdensates) had assembled from gaseous isotopes that required this component of the known presolar grains to have condensed from hot supernova gases containing more oxygen than carbon. Meteoritic chemists and astrophysicists doubted that possibility on intuitive chemical grounds, expecting that abundant hot oxygen gas would oxidize all carbon atoms, trapping them within chemically inert CO molecules. Clayton countered those doubts by stressing that very abundant and energetic electrons produced by scattering of the gamma rays emitted by radioactive cobalt would continuously replenish the abundance of free carbon atoms in the supernova interior by breaking apart those abundant CO molecules. Clayton championed continuous liberation of free carbon from CO molecules as the key to carbon condensation in supernova explosions. This bold position on supernova chemistry was published throughout a 15-yr period (1998-2014) during the latest phase of Clayton’s broad career.[98] Highlights of that thesis were summarized in a 2011 review paper[99] in which Clayton advanced "New Rules" for carbon condensation in oxygen-rich supernovae gases. The kinetic chemical reaction model underlying all of these works was initially devised by Clayton, Weihong Liu and Alexander Dalgarno[100] and later expanded by Clayton and colleagues.[101] They showed how very large dust grains (micrometers in radius) in comparison with average interstellar-medium dust sizes can grow within the oxygen-rich supernova expansion and cooling owing to the action of Population Control.[102] Rapid oxidation abets large-grain carbon condensation by keeping the population of carbon solids small so that those few can grow large by accreting the continuously replenished free carbon. This topic establishes another new aspect of carbon's uniquely versatile chemistry. Chapter 18 of Catch a Falling Star


  1. ^ Clayton, Donald D (2013). "ANALYTIC APPROXIMATION OF CARBON CONDENSATION ISSUES IN TYPE II SUPERNOVAE". The Astrophysical Journal 762 (5). Bibcode:2013ApJ...762....5C. doi:10.1088/0004-637X/762/1/5. 
  2. ^ Yu, Tianhong; Meyer, Bradley S; Clayton, Donald D (2013). "FORMATION OF Cn MOLECULES IN OXYGEN-RICH INTERIORS OF TYPE II SUPERNOVAE". The Astrophysical Journal 769 (38). Bibcode:2013ApJ...769...38Y. doi:10.1088/0004-637X/769/1/38. 
  3. ^ a b c d Clayton, Donald D (2009). Catch a Falling Star: A Life Discovering Our Universe. iUniverse. ISBN 9781440161032. 
  4. ^ a b Clayton, Donald D (1975). The Dark Night Sky: A Personal Adventure in Cosmology. New York: Quadrangle. ISBN 0812905857. 
  5. ^ a b "1970 Clayton and Rosselini in Sardinia". Clemson University. Retrieved 27 August 2014. 
  6. ^ "PHOTO ARCHIVE IN NUCLEAR ASTROPHYSICS". Clemson University. Retrieved 27 August 2014. 
  7. ^ "NASA Headquarters Exceptional Scientific Achievement Medal". Clemson University. Retrieved 6 November 2013. 
  8. ^ a b "Leonard Medal of Meteoritical Society". Clemson University. Retrieved 6 November 2013. 
  9. ^ "OSSE Meeting at Northwestern University April 1993". Clemson University. Retrieved 6 November 2013. 
  10. ^ "Jesse W. Beams Medal, American Physical Society Southeastern Section". Clemson University. Retrieved 6 November 2013. 
  11. ^ "South Carolina Governor's Award for Excellence in Science". Clemson University. Retrieved 6 November 2013. 
  12. ^ "Alexander von Humboldt Senior Scientist Award". Clemson University. Retrieved 6 November 2013. 
  13. ^ a b "Donald Clayton". Clemson University. Retrieved 6 November 2013. 
  14. ^ "Arnold Wolfendale and Donald Clayton". Clemson University. Retrieved 27 August 2014. 
  15. ^ "SMU President Kenneth Pye and Clayton". Clemson University. Retrieved 6 November 2013. 
  16. ^ Clayton, Donald D. "Highland Park High School 1950-53". Catch a Falling Star: A Life Discovering Our Universe (PDF). Retrieved 27 August 2014. 
  17. ^ Catch a Falling Star op cit , p. 84
  18. ^ Note: Mary Lou Clayton was hired by Mathew Sands on the Ford Foundation project for these lectures. Donald Clayton contributed time to help identify the physics vocabulary that Feynman used. See Catch a Falling Star, p. 142
  19. ^ "Star Catcher" (PDF). Retrieved 20 September 2014.  |chapter= ignored (help)
  20. ^ University of Chicago Press, reprint 1983
  21. ^ "Photo Archive In Nuclear Astrophysics: Photo List". Retrieved 2013-10-06. 
  22. ^ Catch a Falling Star Chap. 9, p. 179-183. "Star Catcher" (PDF). Retrieved 20 September 2014.  |chapter= ignored (help)
  23. ^ Fred Hoyle, Home is where the wind blows (University Science Books, Mill Valley CA 1994) p. 372-376
  24. ^ Arnett, W.D. (1970). "Explosive Nucleosynthesis in Stars". Nature 227: 780–784. Bibcode:1970Natur.227..780A. doi:10.1038/227780a0.  jointly with Clayton
  25. ^ Astrophysical Journal 155, 75 (1969); Astrophysical Journal 158, L43 (1969)
  26. ^ American Astronomical Society Centennial Issue, Astrophysical Journal 525, 1-1283 (1999)
  27. ^ “Extinct radioactivities: Trapped residuals of pre-solar grains”, Astrophys. J., 199, 765-69, (1975); “22Na, Ne-E, Extinct radioactive anomalies and unsupported 40Ar”, Nature, 257, 36-37, (1975); “Cosmoradiogenic ghosts and the origin of Ca-Al-rich inclusions”, Earth and Planetary Sci. Lett., 35, 398-410, 1977; “An interpretation of special and general isotopic anomalies in r-process nuclei”, Astrophys. J., 224, 1007-1012, (1978); “On strontium isotopic anomalies and odd-A p-process abundances, Astrophys. J. Lett., 224, L93-95, (1978); “Precondensed matter: Key to the early solar system”, The Moon and Planets, 19, 109-137 (1978)]
  28. ^ Clayton, Catch a falling star, op cit, p. 354-57, p. 387-395
  29. ^ Cosmic chemical memory: a new astronomy (1981 George Darwin Lecture of the RAS), QJRAS 23, 174-212 (1982)
  30. ^ Chapter 14 of his autobiography Catch a Falling Star
  31. ^ Clayton's own words in Catch a falling star op cit attest to his sense of vindication over this issue:(1) The telephone rings in s-process stardust, p 400-401; (2)"Comic battle over the Leonard Medal, p. 489-491
  32. ^ Donald D. Clayton, Nature 404, 329 (2000)
  33. ^ Catch a Falling Star, Chap. 18
  34. ^ Catch a Falling Star photo p. 494
  35. ^ "Presolar Grain workshop 2012". Retrieved 2013-10-06. 
  36. ^ "Photo Archive In Nuclear Astrophysics". Retrieved 2013-10-06. 
  37. ^ [1]
  38. ^ Center for History of Physics is a wing of American Institute of Physics. It can be reached on the web at and clicking on History Programs
  39. ^ Introduction p. vi, Catch a Falling Star
  40. ^ Catch a Falling Star, photo on p. 99
  41. ^ Donald Clayton, Catch a falling star op cit p. 98-100
  42. ^ Catch a falling star op cit p.300-301
  43. ^ Donald Clayton, Catch a falling star, op cit, p.412-413
  44. ^ "Nancy Clayton - Arclay Art- Web Page". Retrieved 2013-10-06. 
  45. ^ Catch a Falling Star, Chap. 7
  46. ^ Catch a Falling Star, p. 6-9
  47. ^ National Archives, Muster Roll, 43rd Company, Army of Ohio Infantry
  48. ^ p. 245-249 in Catch a Falling Star. The wiki article on Dominique de Menil documents the interaction of the de Menils with Rosselini through the Rice University Media Center
  49. ^ "PHOTO ARCHIVE IN NUCLEAR ASTROPHYSICS". Retrieved 20 September 2014. 
  50. ^ No documentation exists for this failure, so this conclusion is based on Clayton's memory of it.
  51. ^ Quadrangle/The New York Times Book Co. (1975): A book columnist for Washington Post wrote on March 21, 1976:"Altogether more personal, The Dark Night Sky alternates cosmology with affable reminiscence. Clayton knows the rapture of astronomy and uses it to shuttle engagingly back and forth between Copernicus, Einstein, Stonehenge, the Milky Way and punts on Cambridge's Cam. A brooding, ecumenical enthusiast, Clayton dreads the vacant interstellar spaces as much as he loves galaxies, Texas, and the maple tree he planted a quarter of a century ago. His is a book of brainy charm."
  52. ^ "Donald D. Clayton". Retrieved 20 September 2014. 
  53. ^ "Donald D. Clayton Journal Publications". Retrieved 20 September 2014. 
  54. ^ Analytic Approximation of Carbon Condensation Issues in Type II Supernovae, Astrophys. J. 762, 5 (2013)
  55. ^ Burbidge, Burbidge, Fowler & Hoyle RMP 29, 547 (1957)
  56. ^ ["Neutron Capture Chains in Heavy Element Synthesis" Annals of Physics, 12, 331-408 (1961); "Nucleosynthesis of Heavy Elements by Neutron Capture" Ap. J. Suppl. 11, 121-166 (1965)]
  57. ^ [“Nuclear quasi-equilibrium during silicon burning”, Phys. Rev. Letters, 20, 161, (1968); Astrophys. J. Suppl. No. 148, 16, 299, (1968);Chapter 7 of Clayton's 1968 textbook, Principles of Stellar Evolution and Nucleosynthesis]
  58. ^ The B2FH review "Synthesis of the Elements in Stars" RMP 29, 547 (1957)had little correct to say in explanation of this mass region. The B2FH review focussed more on isotopes that can be converted in stars to other isotopes, the secondary processes
  59. ^ Phys. Rev.Letters 20, 161 (1968); Astrophys. J. 16,299 (1968)
  60. ^ Astrophys. J.155, 75 (1969); Woosley, Arnett & Clayton, Astrophys. J. Suppl. 26, 231-312 (1973). See Radioactive Progenitors on p. 286-87
  61. ^ Astrophys. J.155, 75 (1969); Astrophys. J. 188, 155 (1974); Astrophys. J. 198, 151 (1975)
  62. ^ Astrophys. J. 199, 765 (1975);Nature 257,36 (1975); Moon & Planets 19, 109 (1978)
  63. ^ ["Explosive nucleosynthesis in stars, Arnett & Clayton, Nature 227, 780-84 (1970); “Thermonuclear origin of rare neutron-rich isotopes”, Phys. Rev. Letters, 27, 1607, (1971) and Astrophys. J., 175, 201, (1972); “The explosive burning of oxygen and silicon”, Astrophys. J. Supplement Series, 26, 231-312, (1973)]
  64. ^ Donald Clayton, Catch a falling star op cit p. 210-212
  65. ^ "Photo Archive In Nuclear Astrophysics". Retrieved 2013-10-06. 
  66. ^ "Photo Archive In Nuclear Astrophysics". 1985-04-24. Retrieved 2013-10-06. 
  67. ^ [“48Ca Production in Matter Expanding from High Temperature and Density”, Astrophys. J., 462, 825-838 (1996)]
  68. ^ [“Molybdenum Isotopes from a Supernova Neutron Burst”, Astrophys, J. Letters, 540, L49-L52 (2000)]
  69. ^ [Donald D. Clayton, "Handbook of Isotopes in the Cosmos", Cambridge University Press (2003)]
  70. ^ Donald D.Clayton "Hoyle’s Equation" Science 318, 1876-77 (2007); Donald D. Clayton "Fred Hoyle, primary nucleosynthesis and radioactivity" New Astronomy Reviews 52, 360-63 (2008). Younger scientists who never knew Hoyle were overlooking what his 1954 paper achieved
  71. ^ ["Gamma-ray lines from young supernova remnants", Clayton, Colgate & Fishman, (1969) ApJ, 155, 75-82]
  72. ^ Hard X rays imply more to come, Nature 330, 423 (1987)
  73. ^ Donald Clayton, "Cosmic radioactivity: a gamma-ray search for the origins of atomic nuclei, in ESSAYS IN NUCLEAR ASTROPHYSICS, Barnes, Clayton & Schramm, eds., pp. 401-426 (Cambridge University Press, 1982)
  74. ^ Phys. Rev. Lett. 20, 161 (1968); Principles of Stellar Evolution and Nucleosynthesis, Chap. 7 (1968); "Explosive Burning of Oxygen and Silicon" Astrophys. J. Suppl. 26, 231 (1973)
  75. ^ "Radiogenic Iron", Donald Clayton, Meteoritics and Planetary Science 34, A145-A160 (1999)
  76. ^ “The 57Co Abundance in Supernova 1987A”, Astrophys. J. (Lett.), 399, L141-L144 (1992); “Hard X rays from Supernova 1993J”, Astrophys. J. (Letters) 431, L95-L98, (1993); F. Iyudin et al. Astron. & Astrophys. 284, L4 (1994); “CGRO/OSSE Observations of the Cassiopea A Supernova Remnant”, Astrophys. J., 444, 244-250, (1995)
  77. ^ [“Radioactivity in supernova remnants”, Astrophys. J., 142, 189-200, 1965]
  78. ^ Precondensed Matter: Key to the Early Solar System, Moon & Planets 19, 109 (1978)
  79. ^ [ “Extinct radioactivities: Trapped residuals of pre-solar grains”, Astrophys. J., 199, 765-69, (1975); “22Na, Ne-E, Extinct radioactive anomalies and unsupported 40Ar”, Nature, 257, 36-37, (1975); "Grains of anomalous isotopic composition from novae", Clayton & Hoyle, Astrophys.J. 203, 490 (1976); “Cosmoradiogenic ghosts and the origin of Ca-Al-rich inclusions”, Earth and Planetary Sci. Lett., 35, 398-410, 1977; "s-Process studies: xenon isotopic abundances" Astrophys. J. 224, 1000-1006 (1978), initially submitted in 1975; “An interpretation of special and general isotopic anomalies in r-process nuclei”, Astrophys. J., 224, 1007-1012, (1978); “On strontium isotopic anomalies and odd-A p-process abundances, Astrophys. J. Lett., 224, L93-95, (1978); “Precondensed matter: Key to the early solar system”, The Moon and Planets, 19, 109-137 (1978)]
  80. ^ “Extinct radioactivities: Trapped residuals of pre-solar grains”, Astrophys. J., 199, 765-69, (1975); “22Na, Ne-E, Extinct radioactive anomalies and unsupported 40Ar”, Nature, 257, 36-37, (1975)
  81. ^ a b K. D. McKeegan, Met. and Planetary Sciences, 42, 1045 (2007) reviews this history
  82. ^ but also by scientists in Chicago, Pasadena, and Mainz
  83. ^ Annual Reviews of Astronomy and Astrophysics 42, 39-78 (2004)
  84. ^ "Presolar Grain workshop". Retrieved 20 September 2014. 
  85. ^ "Presolar Grain workshop 2012". Retrieved 2013-10-06. 
  86. ^ [“Placing the Sun in Galactic Chemical Evolution: Mainstream SiC Particles”, Astrophys. J., 483, 220-227 (1997); “Placing the Sun and Mainstream SiC Particles in Galactic Chemodynamic Evolution”, Astrophys. J. Letters, 484 , L67-L70 (1997); “Type-X Silicon Carbide Presolar Grains: SNIa Supernova Condensates?”, Astrophys. J., 486, 824-834 (1997); “Molybdenum Isotopes from a Supernova Neutron Burst”, Astrophysical Journal Letters, 540, L49-L52 (2000); “Supernova Reverse Shocks and Presolar SiC Grains”, Astrophys. J. 594, 312-25 (2003)
  87. ^ “A Presolar Galactic Merger Spawned the SiC-grain Mainstream”, Astrophys. J. 598, 313-24 (2003)]
  88. ^ [“Cosmoradiogenic chronologies of nucleosynthesis”, Astrophys. J., 139, 637-63, (1964)]
  89. ^ W.A. Fowler and Fred Hoyle, Annals of Phys. 10, 280(1960)
  90. ^ a b Nuclear cosmochronology within analytic models of the chemical evolution of the solar neighborhood, Mon. Notices Roy. Astron. Soc., 234, 1-36 (1988)
  91. ^ [“Galactic chemical evolution and nucleocosmochronology: A standard model”, in Challenges and New Developments in Nucleosynthesis, W. D. Arnett, W. Hillebrandt, and J. W. Truran, eds., University of Chicago Press (Chicago), 65-88 (1984); “Nuclear cosmochronology within analytic models of the chemical evolution of the solar neighborhood”, Mon. Notices Roy. Astron. Soc., 234, 1-36 (1988); “Isotopic anomalies: Chemical memory of galactic evolution”, Astrophys. J., 334, 191-195, (1988)]
  92. ^ [op cit.; “On 26Al and Other Short-lived Interstellar Radioactivity”, Astrophys. J. (Letters) 415, L25-L29 (1993)]
  93. ^ [“Short-lived Radioactivities and the Birth of the Sun”, B.S. Meyer & D.D. Clayton, Space Science Revs., 92, 133-152 (2000)]
  94. ^ “Extinct radioactivities: A three-phase mixing model”, D. Clayton, Astrophys. J., 268, 381-384, 1983
  95. ^ “Short-lived Radioactivities and the Birth of the Sun”, B.S. Meyer & D.D. Clayton, Space Science Revs., 92, 133-152 (2000); Jacobsen, S.B., 2005. The birth of the solar system in a molecular cloud: evidence from the isotopic pattern of short-lived nuclides in the early solar system. In: Krot, A.N., Scott, E.R.D., Reipurth, B. (Eds.), Chondrites and the Protoplanetary Disk. In: Astron. Soc. Pac. Conf. Ser., vol. 341, pp. 548–557; Huss, G.R., Meyer, B.S., Srinivasan, G., Goswami, J.N., Sahijpal, S., 2009. Stellar sources of the short-lived radionuclides in the early solar system. Geochim. Cosmochim. Acta 73, 4922–4945; E.D. Young "Inheritance of solar short- and long-lived radionuclides from molecular clouds and the unexceptional nature of the solar system" Earth and Planetary Science Letters 392 (2014) 16–27
  96. ^ Donald Clayton, Handbook of isotopes in the cosmos , Cambridge University Press 2003), p.285-289
  97. ^ Moon & Planets 19, 109(1978)
  98. ^ [“Condensation of Carbon in Radioactive Supernova Gas”, Science 283, 1290-1292 (1999); Astrophysical Journal 562, 480-493 (2001); “Supernova Reverse Shocks and Presolar SiC Grains”, Astrophys. J. 594, 312-25 (2003); "Growth of Carbon Grains in Supernova Ejecta”, Astrophys. J 638, 234-40 (2006); "Formation of Cn Molecules in Oxygen-Rich Interiors of Type II Supernovae", Astrophys. J. 769, 38 (2013)]
  99. ^ [“A New Astronomy with Radioactivity: Radiogenic Carbon Chemistry”, New Astronomy Reviews , 55, 155-65 (2011)]
  100. ^ Science 283, 1290-92 (1999)
  101. ^ Astrophys. J. 562, 480 (2001); Astrophys. J. 594, 312-325 (2003); Astrophys. J. 638, 234-240 (2006)
  102. ^ [New Astronomy Reviews 55, 155-65 (2011), section 5.5, p. 163]