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 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 star birth and death during the aging of the Milky Way galaxy; (4) astronomy based on 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 from hot gases of solid carbon grains within radioactive supernova gases containing more oxygen than carbon atoms. Clayton spearheaded these subfields of astronomy. He published his research works from positions at five institutions [1] 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.[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[5] with Italian filmmaker Roberto Rosselini [6] about the cosmological life (See PERSONAL below). On the web Clayton has published a large photo archive of his personal photographs and scientific captions recording history as he lived it doing research in nuclear astrophysics.[7]

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);[15] SERC Senior Visiting Fellow, The Open University, Milton Keynes, U.K. (1993). In 1993 Clayton was named Distinguished Alumnus of Southern Methodist University,[16] 37 years after his BS degree there.

Early life and education[edit]

Donald D. Clayton was born at home in 1935 in Adair County in southwestern Iowa to farming families during the Great Depression. He has rhapsodized over his love of the farm.[17] Young Clayton attended public school in Texas, however, after his father moved their family 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.[18] He graduated third in his 1953 class from Highland Park High School. The first among his entire extended relations, including his father, to attend any university, Clayton excelled in physics and graduated from Southern Methodist University summa cum laude in 1956 and 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.[19] Clayton completed his Ph.D. Thesis on the s process in stars in 1961. At Caltech Clayton and his wife Mary Lou [20] played a modest role in producing The Feynman Lectures on Physics by converting the taped audio of Feynman's lectures to written prose. At Caltech Clayton met and became a lifelong friend of Fred Hoyle, creator of the nuclear theory of chemical-element formation inside of stars. Clayton's collaborations with Fowler (who 25 years later became 1983 Nobel Laureate in Physics) as Fowler's[21] research student (1957–60) and as Fowler's post-doc (1961–62) 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 the nuclear abundance quasiequilibrium that establishes the abundances between silicon and nickel during silicon burning in stars. He came on the field at a time when nucleosynthesis was a vibrant, modern topic. See citations to his work 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, 45 years after its first publication, it is still in common usage[22] 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 theses included Bradley S. Meyer and Lucy Ziurys, both of whom forged distinguished careers launched by those senior theses. Good historical photos of these students can be seen on Clayton' s photo archive for the history of nuclear astrophysics.[23]

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.[24] 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 many 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.[25] 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, as did William David Arnett, who assumed his first faculty position in 1969 at Rice University. During 1969-74 Arnett, Woosley, Howard and Clayton published jointly numerous innovative studies on the topic of explosive supernova nucleosynthesis, emphasizing the rapid increase of nuclear reaction rates that occur there as a result of the sudden increase in interior stellar temperature caused by the supernova shock wave.[26] During this same period Clayton published the initiating papers[27] on gamma-ray astronomy of line transitions emitted following decay of 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 in the form of iron isotopes, as Fowler and Hoyle had advocated. That paper was designated one of the fifty most influential papers in astronomy during the twentieth century[28] by the American Astronomical Society.

During a later 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 academic leaves from Rice University. There he joined the Meteoritical Society seeking audience for his newly published theoretical picture[29] of a new type of astronomy based on relative abundances of the isotopes of the chemical elements in interstellar dust grains. He hoped such interstellar grains could be discovered within meteorites; but he also advanced a theory that he called cosmic chemical memory [30] 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 presolar grains. Clayton has described [31] 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,[32] Clayton exulted in Nature "the human race holds solid samples of supernovae in its hands and studies them in terrestrial laboratories".[33]

In 1989 Clayton surprised academia by accepting a professorship at Clemson University in order to guide a graduate research program in astrophysics there. This academic segment of his career (1989–present) focused initially on his 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 could be detected after months in exploding stars. He was 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.[34] The initial NASA sponsored workshop at Clemson University in 1990 was continued jointly with Washington University (St. Louis), later sponsored also by the University of Chicago and by the Carnegie Institution of Washington. These workshops helped participants focus their ideas for annual personal submission of abstracts to NASA's Lunar and Planetary Science Conference. A new goal for Clayton became to assemble from his personal collection of professional photographs an archive for the history of nuclear astrophysics[35] and to donate the originals [36] to the Center for the History of Physics.[37] In 2009 Clayton, following his retirement from academic duties, published his scientific autobiography," Catch a Falling Star".[3] Although autobiography is frowned upon by historians as scientific history, it can nonetheless offer unique insights into life on the science frontier, as is the case here. Clayton defended his autobiography against the known weakness for human rewriting of memories to better fit one's self-image by writing: "I try to diminish its force by heavy reliance on my diaries and on my photo albums".[38] Clayton's published refereed research papers are listed here.[39]

Personal[edit]

Clayton married Mary Lou Keesee (deceased) while they were students at SMU[40] and in 1972 he married a German woman, Annette Hildebrand, while residing in Heidelberg (divorced).[41] Clayton remarried (1983) the former Nancy Eileen McBride,[42] who was trained in art and in architecture and is today a watercolor artist.[43] They reside 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 two previous children arose from earlier marriages. A son (Donald Douglas Clayton) lives in Houston and a daughter (Alia Clayton Fisher) lives with her husband and four children in Longmont, Colorado. Another son, Devon Clayton, is deceased. Clayton has one brother and two sisters, each still resident in Texas, two of them also born in Iowa. His mother was born to parents that immigrated to Iowa near 1850, one from England (Kembery) and one from Germany (Keisel). His father was born to English parents having one Dutch grandparent (Yerkes). Both of Clayton's great grandfathers fought in the Civil War (North). Robert M. Clayton fought in Sherman's Army at the battle of Atlanta. 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 which Clayton proposed [44] to provide for that project. In summer 1970 he spent two weeks in Rome working daily with Rosselini [6][45] on that effort, which failed owing to insufficient financial support or to insufficiently theatrical plan.[46] Clayton's published memoir "The Dark Night Sky: a personal adventure in cosmology"[47] laid out his plan.

Citations of research leadership[edit]

Donald D. Clayton's research innovations in astrophysics and planetary science lay in five disparate disciplines. The location of Clayton's written history of each topic within his autobiography, Catch a Falling Star,[48] is referenced at the ends of each of the following five research disciplines. The references within each discipline are to noteworthy seminal published papers by Clayton (names of his coauthors are in his publication list [49]) 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.[50] Sole-author research papers are relatively rare in astrophysics.

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

Using two physical correlations between known abundances of the isotopes and their nuclear properties described in the celebrated B2FH review paper,[51] Clayton created the first calculable time-dependent mathematical models of both the S-process and the R-process of heavy-element stellar nucleosynthesis by neutron captures. Those two 1960s papers showed that details of the known abundances of the heavy chemical elements require that they were created as mixtures of distinct abundance patterns caused by differing intensities of neutron irradiations.[52] They established Clayton in nucleosynthesis by formulating standard models 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. These 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.[53] This concept explained the observed numbers of isotopes in the A=28-62 mass range, which had previously been a mystery.[54] 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.[55] 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.[56] 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 [57] and of radioactive grains condensed from hot supernova gases.[58] Experimental confirmation about fifteen years later of those predictions spurred two new fields of astronomy and brought Clayton high honors. A prolific period of contributions with Clayton's Rice University colleagues W. David Arnett, Stanford E. Woosley and W.Michael Howard showed that partial quasiequilibrium was also active earlier in stars' nuclear evolution, during explosive oxygen burning.[59] Scientific leadership of nucleosynthesis had by 1975 shifted 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[60] 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 [61][62] 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 [63] 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,[64] thereby explaining a riddle in the observed stardust isotopic abundances. Clayton then published a spirited glimpse of nucleosynthesis for scientists outside of nucleosynthesis research.[65] See also chapters 7, 9 and 18 in Catch a Falling Star

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

The motivation for gamma-ray-line astronomy [66] as an empirical test of explosive nucleosynthesis in stars was recognized in the American Astronomical Society Centennial Volume [14] as one of the 50 most influential astrophysics papers of the 20th century. It is the innovation for which Clayton is best known. This high-energy spectroscopic astronomy, which is based on the specific energies of gamma rays emitted by radioactive nuclei that have been ejected from supernovae, has blossomed with observational results. It quickly become a goal for future space astronomy missions, as it was when Compton Gamma Ray Observatory was being proposed to NASA in 1977 and launched by shuttle Atlantis in 1991. Following astronomers' serendipitous discovery in February 1987 of nearby supernova 1987A, Clayton analyzed the mounting excitement generated by observed X-ray emission from SN 1987A in Nature [67] from his sabbatical office at Durham University. Supernova 1987A provided many exciting detections of gamma-ray lines, thereby establishing this theory as a new field of astronomy. CGRO, which detected several of the predicted gamma-ray lines, was the second of NASA’s Great Observatory missions. Clayton was a Co-Investigator for the NASA-approved proposal for the OSSE instrument on CGRO. Clayton had predicted expectations for several gamma-ray-line emitting young nuclei.[68] Key for those predictions was understanding why nucleosynthesis between silicon and nickel was dominated by abundances of radioactive alpha-particle nuclei.[69] Electric repulsion between protons within nuclei renders the silicon-burning quasiequilibrium nuclei highly radioactive, causing supernova explosions to be profoundly radioactive events.[70] Even abundant iron of our world was synthesized as a daughter of radioactive nickel.[71] Today studies of supernovae are dominated by their radioactive nature. This pioneering work earned NASA's Exceptional Scientific Achievement Award to Clayton. The OSSE instrument and the Comptel instrument both confirmed Clayton's predictions.[72] Clayton's aborted initial research of this field in 1965 had derived from an idea based on the r process;[73] but r-process radioactive nuclei are much less abundant in supernovae than are the radioactive nuclei in the silicon-burning quasiequilibrium. So the latter proved to be a much better radioactive source. 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 chemical elements as they would have condensed into solids from the hot gases leaving stars. Clayton named these solids stardust[74], a component of Cosmic dust found later to be distributed within meteorites. Stardust inherited its unusual isotopic compositions from the nuclear evolution 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 discovered. Clayton's 1970s papers [75] laid out seminal ideas of isotopic abundance ratios predicted to exist in stardust, which Clayton envisioned as being a ubiquitous in interstellar dust and subsequently, perhaps, found within meteorites or other samples of interstellar matter. Most breathtaking was Clayton's predictions of excessive abundances within supernova-condensed solid stardust grains of the daughters of the abundant radioactive nuclei within supernova ejecta gases.[76] These papers 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.[77] Almost two decades of experimental search were required following Clayton's 1975 predictions before intact stardust grains (presolar grains) were successfully isolated from the other presolar dust particles.[77] These were extracted from meteorites and measured by precision laboratory techniques, namely by Secondary ion mass spectrometry (SIMS), for the isotopic compositions of their chemical elements. These dramatic experimental discoveries in the 1990s, led primarily by Ernst Zinner and his colleagues at Washington University (St. Louis), but also by scientists in Chicago, Pasadena, and Mainz 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. These discovery experiments dispelled skepticism that surrounded Clayton's predictions, causing him to be awarded [9] the 1991 Leonard Medal of the Meteoritical Society. Main themes of this astronomical science have been summarized in 2004 for astronomers by Clayton & Nittler.[78] To accelerate rapid new knowledge Clayton at Clemson University initiated in 1990 an annual series of workshops cosponsored jointly[79] with Ernst Zinner and his colleagues at Washington University (St. Louis), where presolar stardust particles were being documented in the laboratory by SIMS, utilizing ions that are ejected by sputtering bombardment from individual stardust grains following energetic ion bombardment of stardust particles.[80] The 22nd annual Clemson workshop was held at Carnegie Institution of Washington in January 2014.Clayton continued to provide leadership of the interpretation of stardust.[81] Clayton's has interpreted the puzzling silicon isotope ratios in the presolar Asymptotic giant branch stars, the stars that donated the known presolar mainstream SiC stardust grains to the solar cloud, as being 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 [82] 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 several key concepts for the interstellar abundances of radioactive nuclei in the Galaxy. In 1964 Clayton introduced 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.[83]. 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[84] still did not yield a precise galactic age, however. Clayton reasoned[85] 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[86]. Clayton calculated an age of 13-15 billion years for the oldest galactic nuclei[87], 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 benefiicial understanding of galaxies and abundances has been permanent. 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[88]. 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 has grown in importance with more experimental discoveries of such nuclei within meteorites. These are called "the 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.[89] Clayton advanced an essential aspect for extinct radioactivities, advocating the importance of the time delay required for isotopic mixing between the distinct physical phases of interstellar gas. He showed that each phase contains a distinct average concentration of each extinct radioactive nuclide[90]. These aspects will remain important for decades to come while astronomers question the circumstances of solar birth. Clayton therefore gave emphasis to extinct radioactivity in the Glossary of his 2003 book on isotopes in the cosmos[91]. See also Chapters 16 and 17 of his autobiography, "Catch a Falling Star".

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

For many years Clayton advocated to skeptics that supernova stardust (which in 1977 he had named [92] "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, expecting that abundant hot oxygen gas would oxidize carbon atoms, trapping them in chemically inert CO molecules. Clayton countered 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 the abundant CO molecules there. Clayton championed continuous liberation of free carbon from CO molecules as the key to carbon condensation in supernova explosions. This position was published throughout a 15-yr period (1998-2014) during the latest phase of Clayton’s broad career.[93] Key points are summarized in a 2011 review paper [94] in which Clayton advanced his "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 [95] and expanded by Deneault, Clayton and Meyer (2006). They showed how very large dust grains (micrometers in radius) in comparison with average interstellar-medium dust sizes can grow within the supernova expansion and cooling owing to the action of Population Control.[96] Oxidation keeps 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

References[edit]

  1. ^ California Institute of Technology(1956-63); Rice University (1963-89); Cambridge University (1967-74); Max-Plank Institute for Nuclear Physics (1977-83); Clemson University (1989-2014)
  2. ^ Astrophys. J. 762, 5; Astrophys. J. 769, 38
  3. ^ a b "Donald D. Clayton". Claytonstarcatcher.com. Retrieved 2013-10-06. 
  4. ^ Quadrangle, New York (1975)
  5. ^ Donald Clayton, Catch a falling star op cit p. 249
  6. ^ a b http://www.clemson.edu/ces/astro/NucleoArchive/PhotoList/1970s/70CRosselini1.html
  7. ^ http://www.clemson.edu/ces/astro/NucleoArchive/
  8. ^ "Donald D. Clayton". Clemson.edu. Retrieved 2013-10-06. 
  9. ^ a b "Donald D. Clayton". Clemson.edu. Retrieved 2013-10-06. 
  10. ^ "Photo Archive In Nuclear Astrophysics". Clemson.edu. Retrieved 2013-10-06. 
  11. ^ "Donald D. Clayton". Clemson.edu. Retrieved 2013-10-06. 
  12. ^ "Donald D. Clayton". Clemson.edu. Retrieved 2013-10-06. 
  13. ^ "Donald D. Clayton". Clemson.edu. Retrieved 2013-10-06. 
  14. ^ a b "Photo Archive In Nuclear Astrophysics". Clemson.edu. Retrieved 2013-10-06. 
  15. ^ http://www.clemson.edu/ces/astro/NucleoArchive/PhotoList/1980s/87WolfendaleCb.html
  16. ^ "Photo Archive In Nuclear Astrophysics". Clemson.edu. Retrieved 2013-10-06. 
  17. ^ Donald Clayton, The Dark night Sky op cit p. 1-6
  18. ^ http://claytonstarcatcher.com/files/documents/Chap4.pdf
  19. ^ Donald Clayton, "The Dark Night Sky" (Quadrangle, New York 1975) p.112-114
  20. ^ Mary Lou 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.
  21. ^ http://claytonstarcatcher.com/files/documents/Chapter%207.pdf
  22. ^ University of Chicago Press, reprint 1983
  23. ^ "Photo Archive In Nuclear Astrophysics: Photo List". Clemson.edu. Retrieved 2013-10-06. 
  24. ^ http://claytonstarcatcher.com/files/documents/Chap9.pdf
  25. ^ Fred Hoyle, Home is where the wind blows (University Science Books, Mill Valley CA 1994) p. 372-376
  26. ^ W.D Arnett & D.D.Clayton, "Explosive Nucleosynthesis in Stars" Nature 227,780-784 (1970)
  27. ^ Astrophysical Journal 155, 75 (1969); Astrophysical Journal 158, L43 (1969)
  28. ^ American Astronomical Society Centennial Issue, Astrophysical Journal 525, 1-1283 (1999)
  29. ^ “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)]
  30. ^ Cosmic chemical memory: a new astronomy (1981 George Darwin Lecture of the RAS), QJRAS 23, 174-212 (1982)
  31. ^ Chapter 14 of his autobiography "Catch a Falling Star"
  32. ^ 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
  33. ^ Donald D. Clayton, Nature 404, 329 (2000)
  34. ^ "Presolar Grain workshop 2012". Presolar.wustl.edu. Retrieved 2013-10-06. 
  35. ^ "Photo Archive In Nuclear Astrophysics". Clemson.edu. Retrieved 2013-10-06. 
  36. ^ https://photos.aip.org/taxonomy/term/253
  37. ^ https://photos.aip.org/history-programs/niels-bohr-library/photos
  38. ^ Introduction p. vi, Catch a Falling Star
  39. ^ http://www.claytonstarcatcher.com/files/documents/JournalPub.pdf
  40. ^ Donald Clayton, Catch a falling star op cit p. 98-100
  41. ^ Catch a falling star op cit p.300-301
  42. ^ Donald Clayton, Catch a falling star, op cit, p.412-413
  43. ^ "Nancy Clayton - Arclay Art- Web Page". Arclay.us. Retrieved 2013-10-06. 
  44. ^ 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.
  45. ^ http://www.clemson.edu/ces/astro/NucleoArchive/PhotoList/1970s/70Clayton.html
  46. ^ No documentation exists for this failure, so this conclusion is based on Clayton's memory of it.
  47. ^ 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."
  48. ^ [1]
  49. ^ http://claytonstarcatcher.com/files/documents/JournalPub.pdf
  50. ^ Analytic Approximation of Carbon Condensation Issues in Type II Supernovae, Astrophys. J. 762, 5 (2013)
  51. ^ Burbidge, Burbidge, Fowler & Hoyle RMP 29, 547 (1957)
  52. ^ ["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)]
  53. ^ [“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]
  54. ^ 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
  55. ^ Phys. Rev.Letters 20, 161 (1968); Astrophys. J. 16,299 (1968)
  56. ^ Astrophys. J.155, 75 (1969)
  57. ^ Astrophys. J.155, 75 (1969); Astrophys. J. 188, 155 (1974); Astrophys. J. 198, 151 (1975)
  58. ^ Astrophys. J. 199, 765 (1975);Nature 257,36 (1975); Moon & Planets 19, 109 (1978)
  59. ^ [“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)]
  60. ^ Donald Clayton, Catch a falling star op cit p. 210-212
  61. ^ "Photo Archive In Nuclear Astrophysics". Clemson.edu. Retrieved 2013-10-06. 
  62. ^ "Photo Archive In Nuclear Astrophysics". Clemson.edu. 1985-04-24. Retrieved 2013-10-06. 
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