Relating Changes in Cometary Rotation to Activity: Current Status and Applications to Comet C/2012 S1 (Ison)

Samarasinha, Nalin H.; Mueller, B. E. A.

doi:10.1088/2041-8205/775/1/l10

Cited by 36 publications

(66 citation statements)

References 46 publications

(43 reference statements)

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“…It is not surprising that the change for 67P is similar to that for 9P, a comet of similar size and activity level, although with a considerably longer rotation period (41 h). Samarasinha & Mueller (2013) compared the four comets with observed spinrate changes and their activity level, and found that an approximately constant factor (within a factor of two) links them and allows the change of rotation rate to be predicted based on the size, period, and orbit of the comet, and that the changes should be independent of the active fraction of the surface area. The measurement for 67P is two to three times larger than this analysis predicted (Samarasinha, priv.…”

Section: Discussionmentioning

confidence: 99%

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Mottola¹,

Lowry

Snodgrass

et al. 2014

A&A

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Aims. Approach observations with the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) experiment onboard Rosetta are used to determine the rotation period, the direction of the spin axis, and the state of rotation of comet 67P's nucleus. Methods. Photometric time series of 67P have been acquired by OSIRIS since the post wake-up commissioning of the payload in March 2014. Fourier analysis and convex shape inversion methods have been applied to the Rosetta data as well to the available ground-based observations. Results. Evidence is found that the rotation rate of 67P has significantly changed near the time of its 2009 perihelion passage, probably due to sublimation-induced torque. We find that the sidereal rotation periods P 1 = 12.76129 ± 0.00005 h and P 2 = 12.4043 ± 0.0007 h for the apparitions before and after the 2009 perihelion, respectively, provide the best fit to the observations. No signs of multiple periodicity are found in the light curves down to the noise level, which implies that the comet is presently in a simple rotation state around its axis of largest moment of inertia. We derive a prograde rotation model with spin vector J2000 ecliptic coordinates λ = 65• ± 15• , corresponding to equatorial coordinates RA = 22• , Dec = +76• . However, we find that the mirror solution, also prograde, at λ = 275• ), is also possible at the same confidence level, due to the intrinsic ambiguity of the photometric problem for observations performed close to the ecliptic plane.

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Section: Discussionmentioning

confidence: 99%

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Mottola¹,

Lowry

Snodgrass

et al. 2014

A&A

View full text Add to dashboard Cite

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“…Possible explanations for the runaway mass loss include the loss of icy glue holding sections of the nucleus together, build up of subsurface pressure which was eventually released through one or more catastrophic outbursts, or splitting via rotational spin-up (Samarasinha & Mueller 2013). Significant mass loss was not likely triggered by tidal forces, which should not have become significant until the day of perihelion (Knight & Walsh 2013).…”

Section: Discussionmentioning

confidence: 99%

Observations of Comet Ison (C/2012 S1) From Lowell Observatory

Knight

Schleicher

2014

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We observed the dynamically new sungrazing comet ISON (C/2012 S1) extensively at Lowell Observatory throughout 2013 in order to characterize its behavior prior to perihelion. ISON had "typical" abundances for an Oort Cloud comet. Its dust production, as measured by r Af , remained nearly constant during the apparition but its CN gas production increased by ∼50 ×. The minimum active area necessary to support observed water production rates exceeded the likely surface area of the nucleus and suggests a population of icy grains in the coma. Together with the flattening of the dust radial profile over time, this is consistant with ejection of a large quantity of slow moving dust and icy grains in the coma at large heliocentric distance. The dust morphology was dominated by the tail, but a faint sunward dust fan was detected in March, April, May, and September. We imaged multiple gas species in September, October, and November. All gas species were more extended than the dust coma, although only CN had sufficient signal-to-noise for detailed morphological study. Excess CN signal was observed in the sunward hemisphere in September and early October. In November the excess CN signal was in the tailward hemisphere and two faint CN features appeared approximately orthogonal to the tail with position angles varying by about ±20°from night to night. Using numerical modeling, we best reproduced the orientation and shape of these features as well as the bulk brightness with a pole oriented approximately toward the Sun and a single source located within ∼35°of the equator. Variations in position angle and relative brightness of the CN features from night to night suggest a rotation period shorter than 24 hr. The production rates and coma morphology suggest a nucleus that was active over nearly its entire sunward facing hemisphere in September and October but which underwent a significant mass loss event, potentially including fragmentation, shortly before November 1. Significant subsequent mass loss likely continued at the same site over subsequent days/weeks and may have catastrophically weakened the nucleus prior to perihelion.

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“…Other observations, e.g., SOHO-UVCS or STEREO-SECCHI EUVI imaging spectroscopy, are of too short duration and of comets in an even harsher solar environment, and are therefore less likely to reveal rotation periods. Samarasinha and Mueller (2013) showed that near-Sun comets can have their rotation periods significantly altered and can be excited into non-principal axis rotation by the high outgassing rates near perihelion. Drahus (2014) argued that increasing coma optical depth could mitigate this to some extent, but nonetheless found that rotational disruption might explain the high frequency of destruction of long-period comets with q < 0.5 AU noted by Bortle (1991).…”

Section: Rotation Ratesmentioning

confidence: 99%

“…These events are not well explained but one leading explanation is rotational break-up due to spin-up from asymmetric outgassing on the nucleus, which may have been responsible for C/2012 S1 ISON's apparent breakup prior to perihelion (e.g., Samarasinha and Mueller 2013). Sekanina (2000Sekanina ( , 2002a used the motions of pairs of temporally clustered Kreutz comets to argue that non-tidal fragmentation occurs at very large heliocentric distances (tens of AU) in addition to tidal fragmentation near perihelion.…”

Section: Other Potential Influencesmentioning

confidence: 99%

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

et al. 2017

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This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all ob- jects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun's centre, equal to half of Mercury's perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground-and space-based facilities that will allow us to address those science topics.

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Relating Changes in Cometary Rotation to Activity: Current Status and Applications to Comet C/2012 S1 (Ison)

Cited by 36 publications

References 46 publications

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

The rotation state of 67P/Churyumov-Gerasimenko from approach observations with the OSIRIS cameras on Rosetta

Observations of Comet Ison (C/2012 S1) From Lowell Observatory

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

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