Scott Jay Kenyon

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Scott Jay Kenyon
Born Scott J. Kenyon
Nationality United States American
Fields Astrophysics:
star formation and planetary formation
Institutions Smithsonian Astrophysical Observatory
Alma mater Arizona State University (1978)
University of Illinois, Champaign-Urbana (1983)
Doctoral advisor Ronald F. Webbink

Scott Jay Kenyon (born 1956) is an American astrophysicist. His work has included advances in symbiotic and other types of interacting binary stars, the formation and evolution of stars, and the formation of planetary systems.

Career[edit]

Kenyon received a B.S. in physics from Arizona State University in 1978 and a Ph. D. in astronomy from the University of Illinois at Champaign-Urbana in 1983. His doctoral dissertation is entitled The Physical Structure of the Symbiotic Stars[1] and was expanded into a book, The Symbiotic Stars.[2] After postdoctoral work at the Harvard-Smithsonian Center for Astrophysics, including a CfA Fellowship, he joined the scientific staff at the Smithsonian Astrophysical Observatory.[citation needed]

Kenyon is a Fellow of the AAAS, a Fellow[3] of the American Physical Society, and is included in the Web of Knowledge index of highly cited researchers.[4]

Scientific work[edit]

Kenyon has worked extensively on symbiotic binary stars.[5] His book The Symbiotic Stars was the first to summarize observations and theories for these interacting binaries.[6] The book reviews the general state of knowledge in this field c. 1984 and contains case histories of well-studied binaries[7] and complete references to all papers published on symbiotic stars before c. 1984.[8] With more than 350 citations,[5] the book is a standard in the field.

Kenyon and Lee Hartmann first worked out detailed accretion disk models for pre-main-sequence stars and applied these models to optical and infrared spectra of FU Orionis objects.[9] Aside from explaining many details in the spectra of FUors,[9][10] observations of the size of the disk in FU Orionis match model predictions.[11] Observations of long-term variability in FUors also generally match model predictions.[12][13] Kenyon and Hartmann used photometric observations and disk models to show that the disks of FUors are surrounded by infalling envelopes with a bipolar cavity.[12] The bipolar cavity is a result of a wind[14] from the disk, which interacts with the surrounding material to produce a bipolar outflow and (perhaps) a Herbig–Haro object,[10] .[15]

Kenyon and Hartmann later developed the first flared accretion disk model to explain the large infrared luminosities of T Tauri stars.[16] In this model, each concentric annulus of the disk is in hydrostatic equilibrium. The surface of the disk then flares upward like the surface of a shallow bowl. A flared disk intercepts and re-radiates more light from the central star than a flat disk, producing a larger predicted infrared luminosity which agrees with observations of T Tauri stars.[16] Theoretical images[17] of edge-on flared disks look identical to actual images,[18][19][20] taken with the Hubble Space Telescope, illustrating direct evidence for flared disks.[21]

In 1990, Kenyon, Hartmann and Karen & Steve Strom identified the luminosity problem: protostars in the Taurus-Auriga star-forming region are approximately 10 times less luminous than predicted by star formation theory.[22] In this theory, protostars form by gravitational collapse of a cloud of gas and dust. Over their lifetimes, protostars radiate a total energy comparable to their binding energy. With apparent lifetimes of about 100,000 yr, they have expected luminosities of 10-20 larger than the solar luminosity. Recent observations of larger numbers of protostars with the Spitzer Space Telescope confirm that protostars have typical luminosities closer to the solar luminosity .[23] Kenyon and colleagues identified several possible solutions to this luminosity problem. Adopting larger ages allows protostars to radiate the same amount of energy over a longer time, reducing their average luminosity. If protostars spend a small fraction of their lifetimes at much higher luminosity, as in the FU Orionis stars, then their average luminosity can be much larger than their typical luminosity. McKee & Offner note that ejecting material in a bipolar outflow reduces the expected luminosity of protostars but does not resolve the luminosity problem.[22] Data from Spitzer resolve the luminosity problem by deriving better estimates for the time spent in a high luminosity state and larger ages of 300,000 yr for protostars.[24] This resolution leads to an improved understanding of the early life histories of stars.[22][24]

Kenyon has developed numerical models for planet formation and applied these calculations to the formation of debris disks[25] and Kuiper belt objects.[26] Kenyon and Ben Bromley have suggested that the dwarf planet Sedna in the outer solar system might be an exosolar object captured during a close encounter with another planetary system when the Sun was only a few million years old.[27][28][29] This capture mechanism might also explain other unusual [dwarf planets] such as (2004) XR 190[30]

Publications[edit]

Here is a cross-section of Kenyon's publications with more than 100 citations.

References[edit]

  1. ^ Kenyon, S. J. (1983). "Physical Nature of the Symbiotic Stars". NASA Astrophysics Data System. p. 8. Bibcode:1983PhDT.........8K. 
  2. ^ "The Symbiotic Stars". Cambridge University Press. Retrieved 18 October 2012. 
  3. ^ "2013 APS Fellows". Retrieved 9 February 2014. 
  4. ^ "Index of Highly Cited Researchers". Web of Knowledge. Retrieved 25 October 2012. 
  5. ^ a b "S. Kenyon publications on symbiotic stars". 
  6. ^ Selvelli, P. L. (1988). "Book Review: The symbiotic stars". Space science reviews 47: 402. Bibcode:1988SSRv...47..402S. 
  7. ^ Stickland, D. (August 1987). "Book Review: The symbiotic stars". The Observatory 107: 170. Bibcode:1987Obs...107..170S. 
  8. ^ Chochol, D. "Book review: The symbiotic stars". Bull. Astr. Inst. Czech. 39: 128. Bibcode:1988BAICz..39..128C. 
  9. ^ a b Bertout, C. "T Tauri Stars-Wild as Dust". Ann. Rev. Astr. & Astrophys. 27: 351. Bibcode:1989ARA&A..27..351B. doi:10.1146/annurev.aa.27.090189.002031. 
  10. ^ a b Reipurth, B., FU Orionis eruptions and early stellar evolution, Bibcode:1990IAUS..137..229R 
  11. ^ Malbet, F.; et al. "FU Orionis Resolved by Infrared Long-Baseline Interferometry at a 2 AU Scale". Astrophys. J. 507: L149. arXiv:astro-ph/9808326. Bibcode:1998ApJ...507L.149M. doi:10.1086/311688. 
  12. ^ a b Clarke, C.; G. Lodato; S. Y. Melnikov; M. A. Ibrahimov. "The photometric evolution of FU Orionis objects: disc instability and wind-envelope interaction". MNRAS 361: 942. arXiv:astro-ph/0505515. Bibcode:2005MNRAS.361..942C. doi:10.1111/j.1365-2966.2005.09231.x. 
  13. ^ Bell, K. R.; D. N. C. Lin. "Using FU Orionis outbursts to constrain self-regulated protostellar disk models". Astrophys. J. 427: 987. arXiv:astro-ph/9312015. Bibcode:1994ApJ...427..987B. doi:10.1086/174206. 
  14. ^ Bastian, U.; R. Mundt. "FU Orionis star winds". A&A 144: 57. Bibcode:1985A&A...144...57B. 
  15. ^ Reipurth, B. "Herbig-Haro objects and FU Orionis eruptions The case of HH 57". A&A 143: 435. Bibcode:1985A&A...143..435R. 
  16. ^ a b Chiang, E. I.; P. Goldreich. "Spectral Energy Distributions of T Tauri Stars with Passive Circumstellar Disks". Astrophys. J. 490: 368. arXiv:astro-ph/9706042. Bibcode:1997ApJ...490..368C. doi:10.1086/304869. 
  17. ^ Whitney, Barbara A.; Lee Hartmann. "Model scattering envelopes of young stellar objects. I - Method and application to circumstellar disks". Astrophys. J. 395: 529. Bibcode:1992ApJ...395..529W. doi:10.1086/171673. 
  18. ^ Burrows, Christopher J.; et al. "Hubble Space Telescope Observations of the Disk and Jet of HH 30". Astrophys. J. 473: 437. Bibcode:1996ApJ...473..437B. doi:10.1086/178156. 
  19. ^ Stapelfeldt, Karl R. "An Edge-On Circumstellar Disk in the Young Binary System HK Tauri". Astrophys. J., 502: L65. Bibcode:1998ApJ...502L..65S. doi:10.1086/311479. 
  20. ^ Padgett, Deborah L.; et al. "HUBBLE SPACE TELESCOPE/NICMOS Imaging of Disks and Envelopes around Very Young Stars". Astron. J. 117: 1490. Bibcode:1999AJ...117.1490P. doi:10.1086/300781. 
  21. ^ Cotera, Angela; et al. "High-Resolution Near-Infrared Images and Models of the Circumstellar Disk in HH 30". Astrophys. J. 556: 958. Bibcode:2001ApJ...556..956C. doi:10.1086/321627. 
  22. ^ a b c McKee, C. F.; Offner, S.R.R., The Luminosity Problem: Testing Theories of Star Formation, arXiv:1010.4307, Bibcode:2011IAUS..270...73M, doi:10.1017/S1743921311000202 
  23. ^ Dunham, M.M. "Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Toward Reconciling Models and Observations". Astrophys. J. 710: 470. arXiv:0912.5229. Bibcode:2010ApJ...710..470D. doi:10.1088/0004-637X/710/1/470. 
  24. ^ a b Offner, S. S. R.; McKee, C. F. "The Protostellar Luminosity Function". Astrophys. J. 736: 53. arXiv:1105.0671. Bibcode:2011ApJ...736...53O. doi:10.1088/0004-637X/736/1/53. 
  25. ^ Kennedy, G.M.; M.C. Wyatt. "Are debris disks self-stirred?". MNRAS 405: 1253. arXiv:1002.3469. Bibcode:2010MNRAS.405.1253K. doi:10.1111/j.1365-2966.2010.16528.x. 
  26. ^ Goldreich, P.; Lithwick, Y.; Sari, R. "Planet Formation by Coagulation: A Focus on Uranus and Neptune". ARA&A 42: 549. arXiv:astro-ph/0405215. Bibcode:2004ARA&A..42..549G. doi:10.1146/annurev.astro.42.053102.134004. 
  27. ^ Quandt, Matthew (December 2004). "Two Young Stars Scuffle". Astronomy. 
  28. ^ Gugliotta, Guy (13 February 2005). "Distant object could hold secrets to Earth's past". Washington Post. 
  29. ^ Overbye, Dennis (2 December 2004). "Sun Might Have Exchanged Hangers-On With Rival Star". New York Times. 
  30. ^ Spotts, Peter (19 December 2005). "How to explain a mini-planet's odd orbit?". Christian Science Monitor. 

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