Radar Observations of Comet 103p/Hartley 2

Harmon, J. K.; Nolan, M. C.; Howell, E. S.; Giorgini, Jon D.; Taylor, Patrick A.

doi:10.1088/2041-8205/734/1/l2

Cited by 59 publications

(65 citation statements)

References 13 publications

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“…The optimal solution is found at the frequency of 1.310 d −1 (period of 18.32 h) and is indicated by an arrow. (Harmon et al 2011a), and is similar to the periods of 18.7 ± 0.3 h (Knight & Schleicher 2011) and ∼18.8 h (Samarasinha et al 2011) inferred from the repeatability of the CN coma profile.…”

Section: Periodicity In the Cn Datasupporting

confidence: 85%

Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter

Waniak

Borisov

Drahus

et al. 2012

A&A

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Context. In late 2010, a Jupiter family comet 103P/Hartley 2 was the subject of an intensive world-wide investigation. On UT October 20.7, the comet approached the Earth within only 0.12 AU, and on UT November 4.6 it was visited by the NASA EPOXI spacecraft. Aims. We joined this international effort and organized a ground-based observing campaign with three key goals to: (1) measure the parameters of the nucleus rotation in a time series of CN; (2) investigate the compositional structure of the coma by comparing the CN images with nightly snapshots of C 3 ; and (3) investigate the photochemical relation of CN to HCN, using the HCN data collected nearly simultaneously with our images. Methods. The images were obtained through narrowband filters using the two-meter telescope of the Rozhen National Astronomical Observatory. They were taken over four nights about the moment of the EPOXI encounter. Image processing methods and periodicity analysis techniques were used to identify transient coma structures and investigate their repeatability and kinematics. Results. We observe shells, arc-, jet-and spiral-like patterns that are very similar for the CN and C 3 comae. The CN features expanded outwards with the sky-plane projected velocities of between 0.1 to 0.3 km s −1 . A corkscrew structure, observed on November 6, evolved with a much higher velocity of 0.66 km s −1 . The photometry of the inner coma of CN shows variability with a period of 18.32 ± 0.30 h (valid for the middle moment of our run, UT 2010 Nov 5.0835), which we attribute to the nucleus rotation. This result is fully consistent with independent determinations around the same time by other teams. The pattern of repeatability is, however, imperfect, which is understendable given the suggested excitation of the rotation state, and the variability detected in CN correlates well with the cyclic changes in HCN, but only in the active phases. The identified coma structures, along with the snapshot of the nucleus orientation obtained by EPOXI, enable us to estimate the spin axis orientation. We obtain RA = 122 • , Dec = +16 • (epoch J2000.0), neglecting at this point the rotational excitation.

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Section: Periodicity In the Cn Datasupporting

confidence: 85%

Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter

Waniak

Borisov

Drahus

et al. 2012

A&A

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“…Images obtained during the flyby showed a coma of large particles reaching dimensions between 0.1 and 2.21 m, with a few of the largest particles reaching effective radii close to 4 m (Kelley et al 2013), surrounding the nucleus (A'Hearn et al 2011). These individual large chunks move at 0.5-2 m s −1 and had already been detected via radar observations just before the close encounter (Harmon et al 2011). The largest chunks detected from the spacecraft were icy, and dragged from the nucleus with escaping carbon dioxide into the coma: their sublimation provides a large fraction of the total H 2 O gaseous output of the comet (A'Hearn et al 2011).…”

Section: Introductionmentioning

confidence: 93%

Size-frequency distribution of boulders ≥10 m on comet 103P/Hartley 2

Pajola

Lucchetti

Bertini

et al. 2015

A&A

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Aims. We derive the size-frequency distribution of boulders on comet 103P/Hartley 2, which are computed from the images taken by the Deep Impact/HRI-V imaging system. We indicate the possible physical processes that lead to these boulder size distributions. Methods. We used images acquired by the High Resolution Imager-Visible CCD camera on 4 November 2010. Boulders ≥10 m were identified and manually extracted from the datasets with the software ArcGIS. We derived the global size-frequency distribution of the illuminated side of the comet (∼50%) and identified the power-law indexes characterizing the two lobes of 103P. The three-pixel sampling detection, together with the shadowing of the surface, enables unequivocally detection of boulders scattered all over the illuminated surface. Results. We identify 332 boulders ≥10 m on the imaged surface of the comet, with a global number density of nearly 140/km 2 and a cumulative size-frequency distribution represented by a power law with index of −2.7 ± 0.2. The two lobes of 103P show similar indexes, i.e., −2.7 ± 0.2 for the bigger lobe (called L1) and −2.6 +0.2/ − 0.5 for the smaller lobe (called L2). The similar power-law indexes and similar maximum boulder sizes derived for the two lobes both point toward a similar fracturing/disintegration phenomena of the boulders as well as similar lifting processes that may occur in L1 and L2. The difference in the number of boulders per km 2 between L1 and L2 suggests that the more diffuse H 2 O sublimation on L1 produce twice the boulders per km 2 with respect to those produced on L2 (primary activity CO 2 driven). The 103P comet has a lower global power-law index (−2.7 vs. −3.6) with respect to 67P. The global differences between the two comets' activities, coupled with a completely different surface geomorphology, make 103P hardly comparable to 67P. A shape distribution analysis of boulders ≥30 m performed on 103P suggests that the cometary boulders show more elongated shapes when compared to collisional laboratory fragments as well as to the boulders present on the surfaces of 25 143 Itokawa and 433 Eros asteroids. Consequently, this supports the interpretation that cometary boulders have different origins with respect to the impact-related asteroidal boulders.

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“…3). The turn on/off of the curved jet in the eastern direction has been explained as the response of an active area that faces the Sun coinciding with the nucleus spin period (Harmon et al 2011) during October 24-27, 2010. This finding in our data is confirmed by the EPOXI Team when analysing a sequence of images acquired by the HRI and MRI instruments on board.…”

Section: Dustmentioning

confidence: 99%

“…This finding in our data is confirmed by the EPOXI Team when analysing a sequence of images acquired by the HRI and MRI instruments on board. Assuming that on October 27 between 01:42 and 03:33 this active area faced the Sun and that the nucleus spin period is 18.1 h (Harmon et al 2011), the dust coma of 103P would have displayed the same structure on October 29 at ∼07:30 UT i.e. during dawn at the Observatorio El Roque de los Muchachos but unfortunately was not observable.…”

Section: Dustmentioning

confidence: 99%

Comet 103P/Hartley 2 at perihelion: gas and dust activity

Lara

Lin

Meech

2011

A&A

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Context. The comet 103P/Hartley 2, target of the EPOXI mission (NASA), was supposed to be observed for 3 days around its perihelion, from October 27 to 29, 2010, but photometric data were obtained only on October 27 and 29, 2010. On both dates, the comet visibility was not optimal due to its proximity to the Moon, as projected on the plane of the sky, whereas on October 28, the comet could not be observed at all. Aims. The goal of the campaign was to give ground support to the EPOXI mission by establishing a baseline of activity at perihelion to be compared with in situ activity observed by the space mission about 7 days later on Nov. 4, 2010. We aimed to assess gas and dust production rates, to study the gas and dust coma morphology, to investigate the behaviour of the refractory component by analysing the dust colour variations with date and with projected cometocentric distance, ρ, and to determine the slope of the surface brightness profiles, B, as a function of ρ. Methods. Long-slit spectra and optical broad-and narrowband images were acquired with the instrument ACAM mounted on the William Herschel Telescope (WHT) at La Palma Observatory. We investigated the evolution of the dust coma morphology from the images acquired with specific continuum cometary filters (in the blue and red wavelength region) with image-enhancing techniques. We studied (1) the gas and dust production rates; (2) the dust radial brightness profiles; (3) the profiles of the CN, C 2 , C 3 and NH 2 column densities, and (4) the CN and C 3 coma morphologies. The dust and gas profiles were azimuthally averaged, as well as measured in both the E-W direction (∼Sun-antisolar direction) and in a direction defined by the slit orientation at PA 70 to 250 degrees. Results. The morphological analysis of the dust coma reveals only one structure. Aside from the dust tail in the west direction, a bright jet is detected in images acquired on October 27 at 03:00-04:00 UT. This jet turns on and off and it is not clearly detected at any time on the images obtained during October 29. This structure is enhanced by making use of the radial renormalization and the LarsonSekanina method. It is also confirmed by the distortion of the isophotes at the same position angle (PA). The Afρ parameter, a proxy to the dust production rate, and the gas (CN, C 3 , C 2 , and NH 2 ) production rate, Q i , have been measured at perihelion, r h ≈ 1.058 AU. The quotient Q C 2 /Q CN ∼ 1.3 places 103P/Hartley 2 as a typical comet in terms of long-chain hydrocarbon abundance. The gas-to-dust mass ratio is ∼3−6, indicating that 103P/Hartley 2 is a relatively gas-rich comet. At perihelion, Afρ, as measured in a circular aperture of ∼4700 km ranges from ∼60 cm in the blue to ∼110 cm in the red, which indicates an overall change in the optical properties of the dust grains. On the other hand, the Afρ is rather stable in the innermost coma when it is computed from the spectroscopic measurements within several continuum spectral ranges from 482-685 nm. Both 2D dust colour maps...

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Radar Observations of Comet 103p/Hartley 2

Cited by 59 publications

References 13 publications

Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter

Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter

Size-frequency distribution of boulders ≥10 m on comet 103P/Hartley 2

Comet 103P/Hartley 2 at perihelion: gas and dust activity

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Radar Observations of Comet 103p/Hartley 2

Cited by 59 publications

References 13 publications

Rotation-stimulated structures in the CN and C3comae of comet 103P/Hartley 2 close to the EPOXI encounter

Rotation-stimulated structures in the CN and C3comae of comet 103P/Hartley 2 close to the EPOXI encounter

Size-frequency distribution of boulders ≥10 m on comet 103P/Hartley 2

Comet 103P/Hartley 2 at perihelion: gas and dust activity

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Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter

Rotation-stimulated structures in the CN and C₃comae of comet 103P/Hartley 2 close to the EPOXI encounter