Measurement of submicron grains in the coma of comet hale-bopp C/1995 o1 during 1997 February 15-20 UT

D. M. Williams; C. G. Mason; R. D. Gehrz; T. J. Jones; Charles E. Woodward; D. E. Harker; M. S. Hanner; D. H. Wooden; F. C. Witteborn; H. M. Butner

doi:10.1086/310973

Measurement of submicron grains in the coma of comet hale-bopp C/1995 o1 during 1997 February 15-20 UT

D. M. Williams, C. G. Mason, R. D. Gehrz, T. J. Jones, Charles E. Woodward, D. E. Harker, M. S. Hanner, D. H. Wooden, F. C. Witteborn, H. M. Butner

Minnesota Institute for Astrophysics

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Abstract

We present 1.20-18.5 μm infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small. Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S = T_color/T_BB ≈ 1.84, the peak of the 10 μm silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was ≈0.41 at a scattering angle of θ ≈ 144°. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a ≤ 0.4 μm. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae ("stardust") but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction.

Original language	English (US)
Pages (from-to)	L91-L94
Journal	Astrophysical Journal
Volume	489
Issue number	1 PART II
DOIs	https://doi.org/10.1086/310973
State	Published - 1997

Bibliographical note

Funding Information:
1 NSF Presidential Faculty Fellow. 2 Visiting Astronomer, at the Infrared Telescope Facility, operated by the University of Hawaii, under contract from the National Aeronautics and Space Administration.

Funding Information:
R. D. G, T. J. J., C. G. M., and D. M. W. thank A. Knutson for his efforts in support of our operations at MLOF and J. Lyke for his assistance in the MLOF data reduction. M. Jura lent helpful suggestions. The UM IR Group was funded for these observations by the NSF, NASA, and the UM Graduate School. C. E. W. and D. E. H. acknowledge support from the NSF (AST94-53354), NASA (GRSP NGT2-52218), and the Office of Research, University of Wyoming. H. M. B. and D. H. W. were supported by NASA.

Keywords

Comets: individual (Hale-Bopp C/1995 O1)
Interplanetary medium

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10.1086/310973

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@article{6843fcb3d73241aea751c81081b7b964,

title = "Measurement of submicron grains in the coma of comet hale-bopp C/1995 o1 during 1997 February 15-20 UT",

abstract = "We present 1.20-18.5 μm infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small. Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S = Tcolor/TBB ≈ 1.84, the peak of the 10 μm silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was ≈0.41 at a scattering angle of θ ≈ 144°. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a ≤ 0.4 μm. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae ({"}stardust{"}) but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction.",

keywords = "Comets: individual (Hale-Bopp C/1995 O1), Interplanetary medium",

author = "Williams, {D. M.} and Mason, {C. G.} and Gehrz, {R. D.} and Jones, {T. J.} and Woodward, {Charles E.} and Harker, {D. E.} and Hanner, {M. S.} and Wooden, {D. H.} and Witteborn, {F. C.} and Butner, {H. M.}",

note = "Funding Information: 1 NSF Presidential Faculty Fellow. 2 Visiting Astronomer, at the Infrared Telescope Facility, operated by the University of Hawaii, under contract from the National Aeronautics and Space Administration. Funding Information: R. D. G, T. J. J., C. G. M., and D. M. W. thank A. Knutson for his efforts in support of our operations at MLOF and J. Lyke for his assistance in the MLOF data reduction. M. Jura lent helpful suggestions. The UM IR Group was funded for these observations by the NSF, NASA, and the UM Graduate School. C. E. W. and D. E. H. acknowledge support from the NSF (AST94-53354), NASA (GRSP NGT2-52218), and the Office of Research, University of Wyoming. H. M. B. and D. H. W. were supported by NASA.",

year = "1997",

doi = "10.1086/310973",

language = "English (US)",

volume = "489",

pages = "L91--L94",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

number = "1 PART II",

}

TY - JOUR

T1 - Measurement of submicron grains in the coma of comet hale-bopp C/1995 o1 during 1997 February 15-20 UT

AU - Williams, D. M.

AU - Mason, C. G.

AU - Gehrz, R. D.

AU - Jones, T. J.

AU - Woodward, Charles E.

AU - Harker, D. E.

AU - Hanner, M. S.

AU - Wooden, D. H.

AU - Witteborn, F. C.

AU - Butner, H. M.

N1 - Funding Information: 1 NSF Presidential Faculty Fellow. 2 Visiting Astronomer, at the Infrared Telescope Facility, operated by the University of Hawaii, under contract from the National Aeronautics and Space Administration. Funding Information: R. D. G, T. J. J., C. G. M., and D. M. W. thank A. Knutson for his efforts in support of our operations at MLOF and J. Lyke for his assistance in the MLOF data reduction. M. Jura lent helpful suggestions. The UM IR Group was funded for these observations by the NSF, NASA, and the UM Graduate School. C. E. W. and D. E. H. acknowledge support from the NSF (AST94-53354), NASA (GRSP NGT2-52218), and the Office of Research, University of Wyoming. H. M. B. and D. H. W. were supported by NASA.

PY - 1997

Y1 - 1997

N2 - We present 1.20-18.5 μm infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small. Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S = Tcolor/TBB ≈ 1.84, the peak of the 10 μm silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was ≈0.41 at a scattering angle of θ ≈ 144°. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a ≤ 0.4 μm. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae ("stardust") but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction.

AB - We present 1.20-18.5 μm infrared (IR) spectrophotometric measurements of comet C/1995 O1 (Hale-Bopp) during 1997 February 15 and 20 UT. The spectral energy distribution (SED) was dominated by scattering and thermal emission from submicron sized dust grains that were unusually small. Hale-Bopp's surprising brightness may have been largely a result of the properties of its coma grains rather than the size of its nucleus. The thermal emission continuum from the grains had a superheat of S = Tcolor/TBB ≈ 1.84, the peak of the 10 μm silicate emission feature was 1.81 mag above the carbon grain continuum, and the albedo (reflectivity) of the grains was ≈0.41 at a scattering angle of θ ≈ 144°. These are the highest values for these empirical parameters ever observed in 20 years of optical/IR measurements of bright comets. The observations indicate that the optically important grains dominating the visual scattering and near-IR emission from the coma had an average radius of a ≤ 0.4 μm. The strong silicate feature is produced by grains with a similar size range. These dust radii are comparable to the radii of the grains that condense in the outflows of some novae ("stardust") but still about 10 times larger than the average radius of the grains that produce the general interstellar extinction.

KW - Comets: individual (Hale-Bopp C/1995 O1)

KW - Interplanetary medium

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U2 - 10.1086/310973

DO - 10.1086/310973

M3 - Article

AN - SCOPUS:33646980080

SN - 0004-637X

VL - 489

SP - L91-L94

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 PART II

ER -

Measurement of submicron grains in the coma of comet hale-bopp C/1995 o1 during 1997 February 15-20 UT

Abstract

Bibliographical note

Keywords

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