Optical spectropolarimetry of binary asteroid Didymos-Dimorphos before and after the DART impact

Stefano Bagnulo; Zuri Gray; Mikael Granvik; Alberto Cellino; Kolokolova Ludmilla; Karri Muinonen; Olga Muñoz; Cyrielle Opitom; Antti Penttila; Colin Snodgrass

doi:10.3847/2041-8213/acb261

Optical spectropolarimetry of binary asteroid Didymos-Dimorphos before and after the DART impact

Stefano Bagnulo^*, Zuri Gray, Mikael Granvik, Alberto Cellino, Kolokolova Ludmilla, Karri Muinonen, Olga Muñoz, Cyrielle Opitom, Antti Penttila, Colin Snodgrass

^*Corresponding author for this work

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

We have monitored the Didymos-Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modelling purposes. Before impact, Didymos exhibited a linear
polarization rapidly increasing with phase angle, reaching a level of ∼ 5 % in the blue and ∼ 4.5 % in the red. The shape of the polarization spectrum was anti-correlated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization dropped by about
1 percentage point (pp) in the blue band and about 0.5 pp in the red band, then continued to linearly increase with phase angle, with a slope similar to that measured prior to impact. The polarization spectra, once normalised by their values at an arbitrary wavelength, show very little or no change over the course of all observations, before and after impact. The lack of any remarkable change in the shape of the polarization spectrum after impact suggests that the way in which polarization varies with wavelength depends on the composition of the scattering material, rather than on its structure, be this a surface or a debris cloud.

Original language	English
Article number	L38
Pages (from-to)	1-9
Number of pages	9
Journal	Astrophysical Journal Letters
Volume	945
Issue number	2
DOIs	https://doi.org/10.3847/2041-8213/acb261
Publication status	Published - 21 Mar 2023

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@article{748b883667c04010aff86f027d717d19,

title = "Optical spectropolarimetry of binary asteroid Didymos-Dimorphos before and after the DART impact",

abstract = "We have monitored the Didymos-Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modelling purposes. Before impact, Didymos exhibited a linearpolarization rapidly increasing with phase angle, reaching a level of ∼ 5 % in the blue and ∼ 4.5 % in the red. The shape of the polarization spectrum was anti-correlated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization dropped by about1 percentage point (pp) in the blue band and about 0.5 pp in the red band, then continued to linearly increase with phase angle, with a slope similar to that measured prior to impact. The polarization spectra, once normalised by their values at an arbitrary wavelength, show very little or no change over the course of all observations, before and after impact. The lack of any remarkable change in the shape of the polarization spectrum after impact suggests that the way in which polarization varies with wavelength depends on the composition of the scattering material, rather than on its structure, be this a surface or a debris cloud.",

author = "Stefano Bagnulo and Zuri Gray and Mikael Granvik and Alberto Cellino and Kolokolova Ludmilla and Karri Muinonen and Olga Mu{\~n}oz and Cyrielle Opitom and Antti Penttila and Colin Snodgrass",

note = "Funding Information: Based on observations obtained with the FORS2 instrument at the ESO Telescopes at the La Silla Paranal Observatory under program IDs 109.23GL.001 and 109.23GL.002 for Didymos–Dimorphos and 092.C-0639, 095.C-0925(A), and 097.C-0853(A) for the other asteroids shown in Figure . All raw data and calibrations of FORS2 are available at archive.eso.org . This work was supported by the DART mission, NASA contract No. 80MSFC20D0004 and NASA PSP grant 80NSSC21K1131. We are thankful for the great support received during observations by the VLT staff. Research by K.M., A.P., and M.G. is supported in part by Academy of Finland grant Nos. 336546 and 345115. Publisher Copyright: {\textcopyright} 2023. The Author(s). Published by the American Astronomical Society.",

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doi = "10.3847/2041-8213/acb261",

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T1 - Optical spectropolarimetry of binary asteroid Didymos-Dimorphos before and after the DART impact

AU - Bagnulo, Stefano

AU - Gray, Zuri

AU - Granvik, Mikael

AU - Cellino, Alberto

AU - Ludmilla, Kolokolova

AU - Muinonen, Karri

AU - Muñoz, Olga

AU - Opitom, Cyrielle

AU - Penttila, Antti

AU - Snodgrass, Colin

N1 - Funding Information: Based on observations obtained with the FORS2 instrument at the ESO Telescopes at the La Silla Paranal Observatory under program IDs 109.23GL.001 and 109.23GL.002 for Didymos–Dimorphos and 092.C-0639, 095.C-0925(A), and 097.C-0853(A) for the other asteroids shown in Figure . All raw data and calibrations of FORS2 are available at archive.eso.org . This work was supported by the DART mission, NASA contract No. 80MSFC20D0004 and NASA PSP grant 80NSSC21K1131. We are thankful for the great support received during observations by the VLT staff. Research by K.M., A.P., and M.G. is supported in part by Academy of Finland grant Nos. 336546 and 345115. Publisher Copyright: © 2023. The Author(s). Published by the American Astronomical Society.

PY - 2023/3/21

Y1 - 2023/3/21

N2 - We have monitored the Didymos-Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modelling purposes. Before impact, Didymos exhibited a linearpolarization rapidly increasing with phase angle, reaching a level of ∼ 5 % in the blue and ∼ 4.5 % in the red. The shape of the polarization spectrum was anti-correlated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization dropped by about1 percentage point (pp) in the blue band and about 0.5 pp in the red band, then continued to linearly increase with phase angle, with a slope similar to that measured prior to impact. The polarization spectra, once normalised by their values at an arbitrary wavelength, show very little or no change over the course of all observations, before and after impact. The lack of any remarkable change in the shape of the polarization spectrum after impact suggests that the way in which polarization varies with wavelength depends on the composition of the scattering material, rather than on its structure, be this a surface or a debris cloud.

AB - We have monitored the Didymos-Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modelling purposes. Before impact, Didymos exhibited a linearpolarization rapidly increasing with phase angle, reaching a level of ∼ 5 % in the blue and ∼ 4.5 % in the red. The shape of the polarization spectrum was anti-correlated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization dropped by about1 percentage point (pp) in the blue band and about 0.5 pp in the red band, then continued to linearly increase with phase angle, with a slope similar to that measured prior to impact. The polarization spectra, once normalised by their values at an arbitrary wavelength, show very little or no change over the course of all observations, before and after impact. The lack of any remarkable change in the shape of the polarization spectrum after impact suggests that the way in which polarization varies with wavelength depends on the composition of the scattering material, rather than on its structure, be this a surface or a debris cloud.

U2 - 10.3847/2041-8213/acb261

DO - 10.3847/2041-8213/acb261

M3 - Article

SN - 2041-8205

VL - 945

SP - 1

EP - 9

JO - Astrophysical Journal Letters

JF - Astrophysical Journal Letters

IS - 2

M1 - L38

ER -

Optical spectropolarimetry of binary asteroid Didymos-Dimorphos before and after the DART impact

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