Activity in Comets at Large Heliocentric Distance

Roemer, Elizabeth

doi:10.1086/127827

Cited by 37 publications

(20 citation statements)

References 2 publications

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“…Some of them also have tails of distinctive appearance at great distances from the Sun. The tails are featureless, without appreciable broadening with increasing distance from the nucleus, and the length of the tail is several minutes of an arc from the well-condensed head (Roemer 1962). Sekanina (1973Sekanina ( , 1975 was the first to interpret the orientation and general profile of the tails at large heliocentric distances using an approach developed by Finson & Probstein (1968).…”

Section: Resultsmentioning

confidence: 99%

Dust tail of the distant comet C/1999 J2 (Skiff)

Корсун

Chorny

2003

A&A

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Abstract. CCD observations of comet C/1999 J2 (Skiff) were made at the Pik Terskol Observatory on September 15, 1999. The 2-m telescope equipped with the two-channel focal reducer of the Max-Plank-Institute for Aeronomy was used to study the cometary environment. In spite of the large heliocentric distance, 7.24 AU, a straight dust tail with fairly well defined boundaries was recorded. These data provide an opportunity to study the peculiarity of dust, that is not driven by water vapor. To fit the dust tail, a Monte Carlo model was developed. We trace the trajectories of about 10 7 sample grains to construct the detailed brightness distribution in the comet tail. The simulated isophote field and the observed one agree very well. In our model we also take into account the heliocentric dependence of the dust production rate and ejection velocity, and the dust ejection anisotropy. To transform the particle population to brightness in the modelled tail we calculate the scattering cross section of a separate particle using Mie theory. The age, ejection velocity, dust size distribution, minimum and maximum size of the involved dust particles have been derived from the model giving the best fit. The intensity map is in agreement with a flow of the slowly travelling icy grains. It has been determined that the age of the dust tail of comet C/1999 J2 (Skiff) was, at the moment of the observations, about 540 days and that the main reason for its appearance is likely phase transition from amorphous to crystalline water ice activated at the heliocentric distance of 8.6 AU.

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Section: Resultsmentioning

confidence: 99%

Dust tail of the distant comet C/1999 J2 (Skiff)

Корсун

Chorny

2003

A&A

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“…As already pointed out by Roemer (1962), bright comets are the basic source of our knowledge about the physics of these celestial objects. The bright comets are mostly small objects observed at relatively short heliocentric distances during their favourable configuration relative to the Sun and the Earth.…”

Section: Introductionmentioning

confidence: 93%

Observations of Comets C/2007 D1 (LINEAR), C/2007 D3 (LINEAR), C/2010 G3 (WISE), C/2010 S1 (LINEAR), and C/2012 K6 (McNaught) at large heliocentric distances

Ivanova

Neslušan

Krišandová

et al. 2015

Icarus

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Photometric and spectroscopic observations of five nearly parabolic comets with eccentricity larger than 0.99 at heliocentric distances greater than 4 AU were performed. No molecular emission was observed for any studied comet and the entire cometary activity in all cases was attributed to dust production. Upper limits of the gas production rates for the main neutral molecules in the cometary comae were calculated. The derived values of dust apparent magnitudes were used to estimate the upper limit of the geometric cross-section of cometary nuclei (upper limits of radii range from 2 km to 28 km). Due to the poor sublimation of water ice at these distances from the Sun, other mechanisms triggering activity in comets are discussed.

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“…2P/Encke's current aphelion and perihelion distances are 4.09 and 0.34 AU respectively. Early photographic studies of distant comets (i.e., comets at heliocentric distances greater than 3 AU) by Roemer (1962) showed that comets are often active at large distances from the sun. In her observations this activity was obvious in the form of spatially resolved comae and tails.…”

Section: Origin Of the Light Variations Near Aphelionmentioning

confidence: 99%