A model of cometary outbursts: a new simple approach to the classical question

Gronkowski, P.; Wesołowski, M.

doi:10.1093/mnras/stv1122

Cited by 40 publications

(14 citation statements)

References 48 publications

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“…This theory argues that cometary nuclei are probably formed by the aggregation of cometesimals of different sizes, which results in the creation of voids in the form of caves among the cometesimals. This hypothesis was recently discussed in Gronkowski & Weslowski (2015) and Ipatov (2012). In this scenario the outburst (dusty jet) is caused by the abrupt opening of a large subsurface cavity containing gas under high pressure.…”

Section: Subsurface Geysermentioning

confidence: 94%

A model of short-lived outbursts on the 67P from fractured terrains

Skorov

Rezac

Hartogh

et al. 2016

A&A

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Aims. We develop a physical model to explain the potent outbursts that occurred in the fractured terrain of comet 67P near perihelion, and predict its temporal characteristics. Methods. The feasibility of the proposed mechanism is studied using a numerical model accounting for the relevant microscopic/macroscopic processes. We rely on the thermophysical, compositional, and geo-morphological data from the published measurements of respective instruments on board Rosetta. Results. The key idea of this novel mechanism is built around observations of fractures/cracks in the region of interest. It is argued that as the stresses on the nucleus increased during the perihelion approach, a crack deepening event occurred reaching the deeper material containing super-volatile ices in equilibrium with the surrounding. This sudden opening lead to a violent sublimation of the super-volatile ices. The time scales and mass release of this process are modeled and reported. In our modeling we pay attention to the question of the existence of super-volatile ices in the deeper interior for a long time, and the thermal equilibrium in the interior. Conclusions. The deepening of pre-existing cracks (fracture) into the material containing highly volatile ices can explain the observed outburst features. The sudden disequilibration of the steady-state reservoir of highly volatile ices results in a violent release of gas and dust. The proposed mechanism also explains the rapid shut down of this activity in accordance with the observations. The proposed mechanism is independent of solar illumination history of a given region, or the pre-existance of large sealed nucleus cavities.

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Section: Subsurface Geysermentioning

confidence: 94%

A model of short-lived outbursts on the 67P from fractured terrains

Skorov

Rezac

Hartogh

et al. 2016

A&A

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“…In general, during an outburst, the comet brightness increases by a factor of ∼2-5 within a few hours. This corresponds to an average mass release of ∼100 kg with speed in the range of ∼0.1-1.0 km s −1 and an average kinetic energy release of ∼10 12±4 J (Whitney 1955;Hughes 1990;Beech & Gauer 2002;Gronkowski & Wesolowski 2015). The largest outburst was detected at comet 17P/Holmes on 24 October 2007, which had a brightness increase of ∼15 mag (Moreno et al 2008;Sekanina 2008a).…”

Section: Introductionmentioning

confidence: 89%

Impact of a cometary outburst on its ionosphere

Hajra¹,

Henri²,

Vallières³

et al. 2017

A&A

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We present a detailed study of the cometary ionospheric response to a cometary brightness outburst using in situ measurements for the first time. The comet 67P/Churyumov-Gerasimenko (67P) at a heliocentric distance of 2.4 AU from the Sun, exhibited an outburst at ∼1000 UT on 19 February 2016, characterized by an increase in the coma surface brightness of two orders of magnitude. The Rosetta spacecraft monitored the plasma environment of 67P from a distance of 30 km, orbiting with a relative speed of ∼0.2 m s −1 . The onset of the outburst was preceded by pre-outburst decreases in neutral gas density at Rosetta, in local plasma density, and in negative spacecraft potential at ∼0950 UT. In response to the outburst, the neutral density increased by a factor of ∼1.8 and the local plasma density increased by a factor of ∼3, driving the spacecraft potential more negative. The energetic electrons (tens of eV) exhibited decreases in the flux of factors of ∼2 to 9, depending on the energy of the electrons. The local magnetic field exhibited a slight increase in amplitude (∼5 nT) and an abrupt rotation (∼36.4• ) in response to the outburst. A weakening of 10-100 mHz magnetic field fluctuations was also noted during the outburst, suggesting alteration of the origin of the wave activity by the outburst. The plasma and magnetic field effects lasted for about 4 h, from ∼1000 UT to 1400 UT. The plasma densities are compared with an ionospheric model. This shows that while photoionization is the main source of electrons, electron-impact ionization and a reduction in the ion outflow velocity need to be accounted for in order to explain the plasma density enhancement near the outburst peak.

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“…As was mentioned in the previous paragraph, the jump in brightness of a comet is produced by ejection of some layers of its nucleus into outer space and due to the sublimation of subsurface layers exposed in this way to the solar radiation. The calculations are based on the Pogson law and were carried out in a similar way as in Gronkowski (, , ) and Gronkowski & Wesołowski (). The numerical technicalities related to the estimation of jump Δ m can be found in these works and the references therein; here we only outline briefly the main formulae that are used.…”

Section: Calculations Of Cometary Outburst Brightness Amplitudementioning

confidence: 99%

“…We assume that the radius of cometary grains, a , obeys the conditions a min ≤ a ≤ a max . The mass of cometary grains, M inc ( t i ), can be also expressed as (Gronkowski , ; Gronkowski & Wesołowski )

M_{inc} ((), t_{i}) = 4 π R_{n}^{2} η ((), t_{i}) χ ((), J_{H_{2} normalO} ((), t_{i}) \frac{R_{coma}}{v_{{normalH}_{2} O}}) .

…”

Section: Calculations Of Cometary Outburst Brightness Amplitudementioning

confidence: 99%

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Visibility of comets during their outbursts and the night sky light pollution—Use the Bortle scale

2017

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In recent decades, light pollution of the night sky has become a burning issue for all humanity. The negative impact of this state of affairs is particularly burdensome for the living organisms such as humans, animals, and plants, as well as for the whole ecosystems. In addition, it has a particularly negative impact on astronomical observations carried out by professional researchers as well as by amateurs. The night sky polluted by artificial electric light makes the observations of faint astronomical bodies very difficult or even impossible. A special type of such faint celestial bodies comprises comets. However, sometimes comets manifest very large, sudden increases in their luminosity called outbursts of brightness. During the outburst of their brightness, there is a chance to record comets, which are normally objects of low brightness. In this paper, we discuss the conditions of observability of comets during their outbursts of brightness in its relation to the light pollution of the night sky. Numerical calculations are carried out for a hypothetical comet belonging to the Jupiter family. The obtained results are consistent with the observations of outbursts of real comets orbiting in the solar system.

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A model of cometary outbursts: a new simple approach to the classical question

Cited by 40 publications

References 48 publications

A model of short-lived outbursts on the 67P from fractured terrains

A model of short-lived outbursts on the 67P from fractured terrains

Impact of a cometary outburst on its ionosphere

Visibility of comets during their outbursts and the night sky light pollution—Use the Bortle scale

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