UVCS Observation of Sungrazer C/2001 C2: Possible Comet Fragmentation and Plasma‐Dust Interactions

Бемпорад, А.; Poletto, G.; Raymond, J. C.; Biesecker, D. A.; Marsden, B. G.; Lamy, Philippe; Ko, YK; Uzzo, M.

doi:10.1086/427063

Cited by 27 publications

(30 citation statements)

References 34 publications

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“…Most sporadic near-Sun comets are likely to follow the trends observed in the general comet population, if they have a cometary origin. Kreutz comet nucleus sizes, however, have been estimated to be meters to tens of meters in radius by a variety of modeling and observational techniques, e.g., MacQueen and St. Cyr (1991), Raymond et al (1998), Uzzo et al (2001), Iseli et al (2002), Sekanina (2003), Bemporad et al (2005), Knight et al (2010). These sizes are similar to inferred from high resolution imaging with Hubble Space Telescope and/or thermal IR imaging with Spitzer Space Telescope, such as the 25-60 m range inferred for the fragments of split comets D/1999 S4 LINEAR (Weaver et al 2001); the tens of m estimated for 73P/Schwassmann-Wachmann 3-C (Weaver et al 2006;Reach et al 2009), and the inferred 9-30 m range for 332P/IkeyaMurakami (Jewitt et al 2016).…”

Section: Sizesmentioning

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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Section: Sizesmentioning

confidence: 99%

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

et al. 2017

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“…Although it is clear they do not survive their perihelion, the actual distance at and process through which their nucleus is disrupted remain unresolved. Most of the sungrazers dim below detection at around 7 R s and may be completely destroyed by 3 R s , as a handful of UVCS observations suggest (e.g., Bemborad et al 2005). Furthermore, Kimura et al (2002) have suggested that sungrazers should exhibit a second brightness peak at 4-6 R s due to the sublimation of crystalline and amorphous pyroxenes.…”

Section: Science Question 9: 'What Is the Nature Of Dust-plasma Intermentioning

confidence: 99%

The Wide-Field Imager for Solar Probe Plus (WISPR)

et al. 2015

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mission designed to orbit as close as 7 million km (9.86 solar radii) from Sun center. WISPR employs a 95 • radial by 58 • transverse field of view to image the fine-scale structure of the solar corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. WISPR is the smallest heliospheric imager to date yet it comprises two nested wide-field telescopes with large-format (2 K × 2 K) APS CMOS detectors to optimize the performance for their respective fields of view and to minimize the risk of dust damage, which may be considerable close to the Sun. The WISPR electronics are very flexible allowing the collection of individual images at cadences up to 1 second at perihelion or the summing of multiple images to increase the signal-to-noise when the spacecraft is further from the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first 'local' imager providing a crucial link between the large-scale corona and the in-situ measurements.

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“…They imply nucleus sizes on the order of 10 m (Raymond et al 1998;Uzzo et al 2001;Bemporad et al 2005) to hundreds of meters (McCauley et al 2013). Increases in the apparent size of the nucleus imply breakup, providing an estimate of the tensile strength of the nucleus (Uzzo et al 2001).…”

Section: Introductionmentioning

confidence: 99%

Probing the Solar Wind Acceleration Region With the Sun-Grazing Comet C/2002 S2

Giordano¹,

Raymond²,

Lamy³

et al. 2014

ApJ

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Comet C/2002 S2, a member of the Kreutz family of sungrazing comets, was discovered in white-light images of the Large Angle and Spectromeric Coronagraph Experiment coronagraph on the Solar and Heliospheric Observatory (SOHO) on 2002 September 18 and observed in H i Lyα emission by the SOHO Ultraviolet Coronagraph Spectrometer (UVCS) instrument at four different heights as it approached the Sun. The H i Lyα line profiles detected by UVCS are analyzed to determine the spectral parameters: line intensity, width, and Doppler shift with respect to the coronal background. Two-dimensional comet images of these parameters are reconstructed at the different heights. A novel aspect of the observations of this sungrazing comet data is that, whereas the emission from most of the tail is blueshifted, that along one edge of the tail is redshifted. We attribute these shifts to a combination of solar wind speed and interaction with the magnetic field. In order to use the comet to probe the density, temperature, and speed of the corona and solar wind through which it passes, as well as to determine the outgassing rate of the comet, we develop a Monte Carlo simulation of the H i Lyα emission of a comet moving through a coronal plasma. From the outgassing rate, we estimate a nucleus diameter of about 9 m. This rate steadily increases as the comet approaches the Sun, while the optical brightness decreases by more than a factor of 10 and suddenly recovers. This indicates that the optical brightness is determined by the lifetimes of the grains, sodium atoms, and molecules produced by the comet.

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UVCS Observation of Sungrazer C/2001 C2: Possible Comet Fragmentation and Plasma‐Dust Interactions

Cited by 27 publications

References 34 publications

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

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

The Wide-Field Imager for Solar Probe Plus (WISPR)

Probing the Solar Wind Acceleration Region With the Sun-Grazing Comet C/2002 S2

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