Mid-infrared observations of the nucleus of Comet P/2016 BA14 (PANSTARRS)

Ootsubo, Takafumi; Kawakita, Hideyo; Shinnaka, Yoshiharu

doi:10.1016/j.icarus.2021.114425

Cited by 8 publications

(34 citation statements)

References 40 publications

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“…A similar scenario of somewhat-unplanned direct mid-infrared observations of the nucleus of a comet during close approach is described in the seminal Hanner et al (1985). Ootsubo et al (2021) presented mid-infrared photometry and low-resolution spectra of BA 14 that do not look similar to typical mid-infrared observations of cometary comae (see, e.g., Kelley & Wooden 2009) or the nuclei of more active comets observed at larger heliocentric distances (see, e.g., Kelley et al 2017). Instead of an emission spectrum dominated by emission features from silicates (perhaps most notably the 10 μm excess), the retrieved spectrum appears dominated instead by absorption features due to phyllosilicates and organics.…”

Section: Introductionmentioning

confidence: 66%

“…Perhaps most relevant to the current study is the recent work of Ootsubo et al (2021), which presented and analyzed midinfrared observations of BA 14 just prior to its close approach. Those authors argued that their observations were dominated by emission from BA 14 ʼs nucleus, as opposed to grains in its coma.…”

Section: Introductionmentioning

confidence: 99%

“…While Lisse et al (2006) did find evidence for phyllosilicates in the ejecta of the Deep Impact experiment (A' Hearn et al 2005), the dominant materials (by areal fraction in the retrieved spectral modeling, at least) were amorphous and crystalline silicates. Ootsubo et al (2021) argued that if they did indeed observe the nucleus of BA 14 , then a phyllosilicate-rich surface might be a common surface composition for comets, or at least those on the verge of going dormant. Considering the lack of information about the surface of BA 14 at the wavelengths where comet nuclei are increasingly able to be studied (visible and near-infrared, NIR), it is challenging to ascertain which of these scenarios is more likely, or if BA 14 is an outlier for a reason yet to be considered.…”

Section: Introductionmentioning

confidence: 99%

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Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach

et al. 2022

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The near-Earth comet P/2016 BA14 (PanSTARRS) is a slow-rotating, nearly dormant object, a likely dynamical twin of 252P/LINEAR, and was recently shown to have a mid-infrared spectrum very dissimilar to other comets. Comet BA14 was also recently selected as one of the backup targets for the ESA’s Comet Interceptor, so a clearer understanding of BA14's modern properties would not just improve our understanding of how comets go dormant but could also aid in planning for a potential spacecraft visit. We present observations of BA14 during its 2016 Earth close approach taken with the NASA Infrared Telescope Facility on two dates, both of which are consistent with direct observations of its nucleus. The reflectance spectrum of BA14 is similar to 67P/Churyumov–Gerasimenko, albeit highly phase-reddened. Thermal emission contaminates the reflectance spectrum at longer wavelengths, which we correct with a new Markov Chain Monte Carlo thermal modeling code. The models suggest that BA14's visible geometric albedo is p V = 0.01–0.03, consistent with radar observations; its beaming parameter is typical for NEOs observed in its geometry; and its reflectance spectrum is red and linear throughout the H and K bands. It appears very much like a “normal” comet nucleus despite its mid-infrared oddities. A slow loss of fine grains as the object’s activity diminished might help to reconcile some of the lines of evidence, and we discuss other possibilities. A spacecraft flyby past BA14 could get closer to the nucleus than with a more active target, and we highlight some science questions that could be addressed with a visit to a (nearly) dormant comet.

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Section: Introductionmentioning

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach

et al. 2022

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“…While primarily observed in JFCs, atypical NiI/FeI abundance ratios are also observed in some OCCs, a fact well established for the C 2 /CN abundance ratio that suggests that the reservoirs at the origin of JFCs and OCCs were mixed at some epoch (e.g., Cochran et al 2020). Interestingly, the depletion of simple organics such as C 2 H 6 could be related to their conversion into more complex organics (Roth et al 2020;Ootsubo et al 2020). This is in agreement with the unusual polarization properties observed in comets 21P/Giacobini-Zinner, 73P/Schwassmann-Wachmann 3, and 9P/Tempel 1 that were interpreted in terms of a high number of large particles (Kiselev et al 2000(Kiselev et al , 2015.…”

Section: Discussionmentioning

confidence: 84%

FeI and NiI in cometary atmospheres

Hutsemékers

Manfroid

Jehin

et al. 2021

A&A

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FeI and NiI emission lines have recently been found in the spectra of 17 Solar System comets observed at heliocentric distances between 0.68 and 3.25 au and in the interstellar comet 2I/Borisov. The blackbody equilibrium temperature at the nucleus surface is too low to vaporize the refractory dust grains that contain metals, making the presence of iron and nickel atoms in cometary atmospheres a puzzling observation. Moreover, the measured NiI/FeI abundance ratio is on average one order of magnitude larger than the solar photosphere value. We report new measurements of FeI and NiI production rates and abundance ratios for the Jupiter-family comet (JFC) 46P/Wirtanen in its 2018 apparition and from archival data of the Oort-cloud comet (OCC) C/1996 B2 (Hyakutake). The comets were at geocentric distances of 0.09 au and 0.11 au, respectively. The emission line surface brightness was found to be inversely proportional to the projected distance to the nucleus, confirming that FeI and NiI atoms are ejected from the surface of the nucleus or originate from a short-lived parent. Considering the full sample of 20 comets, we find that the range of NiI/FeI abundance ratios is significantly larger in JFCs than in OCCs. We also unveil significant correlations between NiI/FeI and C 2 /CN, C 2 H 6 /H 2 O, and NH/CN. Carbon-chain-and NH-depleted comets show the highest NiI/FeI ratios. The existence of such relations suggests that the diversity of NiI/FeI abundance ratios in comets could be related to the cometary formation rather than to subsequent processes in the coma.

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“…Any attempts to identify faint troughs of large non-porous silicate particles in remote-sensing observational data would, however, suffer from low signal-to-noise ratios, because a predominance of large particles is likely associated with very weak signals due to their low spatial densities. Nonetheless, silicate emission troughs could be identified in the thermal infrared spectra of cometary nuclei, a successful example of which is comet P/2016 BA14 (PANSTARRS), when they are measured under ideal circumstances of observation with a large telescope at very small geocentric distances (Ootsubo et al 2021). All in all, light-scattering theory, numerical simulation, laboratory experiments, and remote-sensing observations point to the outcome of surface modes that strong silicate emission peaks of particles turn into weak troughs as the size of the particles increases.…”

Section: A Cross-linked Networkmentioning

confidence: 99%

Do twin spectral peaks of olivine particles in the thermal infrared diagnose their sizes and porosities?

Kimura,

Markkanen,

Kolokolova

et al. 2022

Preprint

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A well-established constraint on the size of non-porous olivine grains or the porosity of aggregates consisting of small olivine grains from prominent narrow peaks in thermal infrared spectra characteristic of crystalline silicates is reexamined. To thoroughly investigate thermal infrared peaks, we make theoretical argument for the absorption and scattering of light by non-porous, non-spherical olivine particles, which is followed by numerical verification. Our study provides perfectly rational explanations of the physics behind the small-particle effect of emission peaks in the framework of classical electrodynamics and convincing evidence of small-particle's emission peaks in the literature. While resonant absorption excited by surface roughness on the order of submicrometer scales can be identified even for non-porous olivine particles with a radius of 10 µm, it makes only a negligible contribution to thermal infrared spectra of the particles. In contrast, the porosity of non-spherical particles has a significant impact on the strength and wavelength of the peaks, while the resonant absorption excited by an ensemble of small grains takes place at a wavelength different than one expects for surface roughness. We finally reaffirm that twin peaks of olivine in thermal infrared spectra of dust particles in astronomical environments are the intrinsic diagnostic characters of submicrometer-sized small grains and their aggregate particles in fluffy and porous configurations.

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Mid-infrared observations of the nucleus of Comet P/2016 BA14 (PANSTARRS)

Cited by 8 publications

References 40 publications

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach

FeI and NiI in cometary atmospheres

Do twin spectral peaks of olivine particles in the thermal infrared diagnose their sizes and porosities?

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Mid-infrared observations of the nucleus of Comet P/2016 BA14 (PANSTARRS)

Cited by 8 publications

References 40 publications

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA14 during Its 2016 Close Approach

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA14 during Its 2016 Close Approach

FeI and NiI in cometary atmospheres

Do twin spectral peaks of olivine particles in the thermal infrared diagnose their sizes and porosities?

Contact Info

Product

Resources

About

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach

Near-infrared Spectroscopy of the Nucleus of Low-activity Comet P/2016 BA₁₄ during Its 2016 Close Approach