Scott Jay Kenyon

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Scott Jay Kenyon
Born
Scott J. Kenyon
NationalityAmerican
Alma materArizona State University (1978)
University of Illinois Urbana-Champaign (1983)
Scientific career
FieldsAstrophysics:
star formation and planetary formation
InstitutionsSmithsonian Astrophysical Observatory
Doctoral advisorRonald 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 Urbana-Champaign in 1983. His doctoral dissertation is titled The Physical Structure of the Symbiotic Stars[1] and was expanded into a book, The Symbiotic Stars.[2] After postdoctoral work at the Center for Astrophysics | Harvard & Smithsonian, 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, Karen Strom & 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.

  • Kenyon, S. J.; Webbink, R. F. (1984). "The Nature of Symbiotic Stars". Astrophysical Journal. 279: 252. Bibcode:1984ApJ...279..252K. doi:10.1086/161888.
  • Kenyon, S. J.; Hartmann, L. (1987). "Spectral energy distributions of T Tauri stars - Disk flaring and limits on accretion". Astrophysical Journal. 323: 714. Bibcode:1987ApJ...323..714K. doi:10.1086/165866.
  • Kenyon, S. J.; Hartmann, L.; Strom, K.M.; Strom, S.E. (1990). "An IRAS survey of the Taurus-Auriga molecular cloud". Astronomical Journal. 99: 869. Bibcode:1990AJ.....99..869K. doi:10.1086/115380.
  • Kenyon, S. J.; Hartmann, L. (1995). "Pre-Main-Sequence Evolution in the Taurus-Auriga Molecular Cloud". Astrophysical Journal Supplement. 101: 117. Bibcode:1995ApJS..101..117K. doi:10.1086/192235.
  • Hartmann, L.; Kenyon, S. J. (1996). "The FU Orionis Phenomenon". Annual Review of Astronomy and Astrophysics. 34: 207. Bibcode:1996ARA&A..34..207H. doi:10.1146/annurev.astro.34.1.207.
  • Kenyon, S. J.; Luu, J. X. (1998). "Accretion in the Early Kuiper Belt II. Fragmentation". Astronomical Journal. 118 (2): 1101. arXiv:astro-ph/9904115. Bibcode:1999AJ....118.1101K. doi:10.1086/300969. S2CID 15956172.
  • Kenyon, S. J.; Bromley, B.C. (2004). "Collisional Cascades in Planetesimal Disks II. Embedded Planets". Astronomical Journal. 127 (1): 513. arXiv:astro-ph/0309540. Bibcode:2004AJ....127..513K. doi:10.1086/379854. S2CID 14759834.
  • Brown, Warren R.; Geller, M. J.; Kenyon, S. J.; Kurtz, M. J. (2005). "Discovery of an Unbound Hypervelocity Star in the Milky Way Halo". Astrophysical Journal Letters. 622 (1): L33. arXiv:astro-ph/0501177. Bibcode:2005ApJ...622L..33B. doi:10.1086/429378. S2CID 14322324.
  • Kennedy, G.M.; Kenyon, S. J. (2008). "Planet Formation around Stars of Various Masses: The Snow Line and the Frequency of Giant Planets". Astrophysical Journal. 673 (1): 502. arXiv:0710.1065. Bibcode:2008ApJ...673..502K. doi:10.1086/524130. S2CID 2910737.

References[edit]

  1. ^ Kenyon, S. J. (1983). "Physical Nature of the Symbiotic Stars". NASA Astrophysics Data System: 8. Bibcode:1983PhDT.........8K. {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ Kenyon, S. J. (1986). The Symbiotic Stars. Cambridge University Press. doi:10.1017/CBO9780511586071. ISBN 9780511586071.
  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 (3–4): 402. Bibcode:1988SSRv...47..402S. doi:10.1007/BF00243559. S2CID 189788657.
  7. ^ Stickland, D. (August 1987). "Book Review: The symbiotic stars". The Observatory. 107: 170. Bibcode:1987Obs...107..170S.
  8. ^ Chochol, D. (1988). "Book review: The symbiotic stars". Bulletin of the Astronomical Institutes of Czechoslovakia. 39 (2): 128. Bibcode:1988BAICz..39..128C.
  9. ^ a b Bertout, C. (1989). "T Tauri Stars-Wild as Dust". Annual Review of Astronomy and Astrophysics. 27: 351. Bibcode:1989ARA&A..27..351B. doi:10.1146/annurev.aa.27.090189.002031.
  10. ^ a b Reipurth, B. (1990), "FU Orionis eruptions and early stellar evolution", Flare Stars in Star Clusters, 137: 229, Bibcode:1990IAUS..137..229R
  11. ^ Malbet, F.; et al. (1998). "FU Orionis Resolved by Infrared Long-Baseline Interferometry at a 2 AU Scale". Astrophysical Journal. 507 (2): L149. arXiv:astro-ph/9808326. Bibcode:1998ApJ...507L.149M. doi:10.1086/311688. S2CID 14528716.
  12. ^ a b Clarke, C.; G. Lodato; S. Y. Melnikov; M. A. Ibrahimov (2005). "The photometric evolution of FU Orionis objects: disc instability and wind-envelope interaction". Monthly Notices of the Royal Astronomical Society. 361 (3): 942–954. arXiv:astro-ph/0505515. Bibcode:2005MNRAS.361..942C. doi:10.1111/j.1365-2966.2005.09231.x. S2CID 15471280.
  13. ^ Bell, K. R.; D. N. C. Lin (1994). "Using FU Orionis outbursts to constrain self-regulated protostellar disk models". Astrophysical Journal. 427: 987. arXiv:astro-ph/9312015. Bibcode:1994ApJ...427..987B. doi:10.1086/174206. S2CID 118898339.
  14. ^ Bastian, U.; R. Mundt (1985). "FU Orionis star winds". Astronomy and Astrophysics. 144: 57. Bibcode:1985A&A...144...57B.
  15. ^ Reipurth, B. (1985). "Herbig-Haro objects and FU Orionis eruptions The case of HH 57". Astronomy and Astrophysics. 143: 435. Bibcode:1985A&A...143..435R.
  16. ^ a b Chiang, E. I.; P. Goldreich (1997). "Spectral Energy Distributions of T Tauri Stars with Passive Circumstellar Disks". Astrophysical Journal. 490 (1): 368–376. arXiv:astro-ph/9706042. Bibcode:1997ApJ...490..368C. doi:10.1086/304869. S2CID 5938719.
  17. ^ Whitney, Barbara A.; Lee Hartmann (1992). "Model scattering envelopes of young stellar objects. I - Method and application to circumstellar disks". Astrophysical Journal. 395: 529. Bibcode:1992ApJ...395..529W. doi:10.1086/171673.
  18. ^ Burrows, Christopher J.; et al. (1996). "Hubble Space Telescope Observations of the Disk and Jet of HH 30" (PDF). Astrophysical Journal. 473: 437. Bibcode:1996ApJ...473..437B. doi:10.1086/178156. S2CID 51756708.
  19. ^ Stapelfeldt, Karl R. (1998). "An Edge-On Circumstellar Disk in the Young Binary System HK Tauri". Astrophysical Journal. 502 (1): L65. Bibcode:1998ApJ...502L..65S. doi:10.1086/311479.
  20. ^ Padgett, Deborah L.; et al. (1999). "HUBBLE SPACE TELESCOPE/NICMOS Imaging of Disks and Envelopes around Very Young Stars". Astronomical Journal. 117 (3): 1490–1504. arXiv:astro-ph/9902101. Bibcode:1999AJ....117.1490P. doi:10.1086/300781. S2CID 16498360.
  21. ^ Cotera, Angela; et al. (2001). "High-Resolution Near-Infrared Images and Models of the Circumstellar Disk in HH 30". Astrophysical Journal. 556 (2): 958. arXiv:astro-ph/0104066. Bibcode:2001ApJ...556..958C. doi:10.1086/321627. S2CID 14354548.
  22. ^ a b c McKee, C. F.; Offner, S.R.R. (2010), "The Luminosity Problem: Testing Theories of Star Formation", Proceedings of the International Astronomical Union, 6: 73–80, arXiv:1010.4307, Bibcode:2011IAUS..270...73M, doi:10.1017/S1743921311000202, S2CID 118314634
  23. ^ Dunham, M.M. (2010). "Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Toward Reconciling Models and Observations". Astrophysical Journal. 710 (1): 470–502. arXiv:0912.5229. Bibcode:2010ApJ...710..470D. doi:10.1088/0004-637X/710/1/470. S2CID 14156633.
  24. ^ a b Offner, S. S. R.; McKee, C. F. (2011). "The Protostellar Luminosity Function". Astrophysical Journal. 736 (1): 53. arXiv:1105.0671. Bibcode:2011ApJ...736...53O. doi:10.1088/0004-637X/736/1/53. S2CID 118784638.
  25. ^ Kennedy, G.M.; M.C. Wyatt (2010). "Are debris disks self-stirred?". Monthly Notices of the Royal Astronomical Society. 405 (2): 1253. arXiv:1002.3469. Bibcode:2010MNRAS.405.1253K. doi:10.1111/j.1365-2966.2010.16528.x. S2CID 55055925.
  26. ^ Goldreich, P.; Lithwick, Y.; Sari, R. (2004). "Planet Formation by Coagulation: A Focus on Uranus and Neptune". Annual Review of Astronomy and Astrophysics. 42 (1): 549–601. arXiv:astro-ph/0405215. Bibcode:2004ARA&A..42..549G. doi:10.1146/annurev.astro.42.053102.134004. S2CID 5177936.
  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.

External links[edit]

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