Cometary Activity Begins at Kuiper Belt Distances: Evidence from C/2017 K2

We discuss the development of activity in the extraordinary, distant long-period comet C/2017 K2 over the heliocentric distance range&#160;9 < rH < 16 AU.&#160; C/2017 K2 is an incoming long-period comet with a period so long (~ 3 Myr) that no heat from the previous perihelion can be retained; we can be sure that the observed mass-loss is driven by the current insolation and not by a thermal lag.&#160; The comet is characterized by a steady-state coma of sub-millimeter and larger particles ejected at low (4 m/s) velocity, filling a roughly spheroidal coma with a characteristic scale of 80,000 km.&#160; In a fixed, co-moving volume around the nucleus we find that the scattering cross-section of the coma, C, is related to the heliocentric distance by a power law, C ~ rH-s, with heliocentric index s = 1.14+/-0.05. This dependence is significantly weaker than the rH-2, variation of the&#160;insolation as a result of two effects.&#160; These are, first, the heliocentric dependence of the dust velocity and, second, a lag effect due to very slow-moving&#160;particles ejected long before the observations were taken. &#160; A Monte Carlo&#160;model of the photometry shows that dust production beginning at rH ~ 35 AU is needed to match the measured heliocentric index, with only a slight dependence on the particle size distribution.&#160; Dust mass loss rates at 10 AU are of order dM/dt ~ 103 a1 kg/s, where 0.1 < a1 < 1 is the effective particle radius expressed in millimeters. The expulsion of submillimeter and larger grains, beginning at Kuiper belt distances, is likely the result of the sublimation of near-surface supervolatile ice (probably CO, as suggested by the recent detection of this molecule at 6.7 AU; Yang et al. Ap. J. Letters, in press). Water ice is involatile over the observed distance range and even the energy and gas release triggered by the crystallization of amorphous ice, if present, cannot produce activity at 35 AU.&#160; Comet C/2017 K2 will reach perihelion near Mars' orbit in December 2022.&#160;&#160; &#160; This work is described in D. Jewitt, Y. Kim. M. Mutchler, J. Agarwal, J. Li and H. Weaver (2021).&#160; Astronomical Journal, 161:188 (11pp)&#160;

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C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric Distance

10.5194/epsc2021-638 ◽

2021 ◽

Author(s):

Man-To Hui ◽

Davide Farnocchia ◽

Marco Micheli

Keyword(s):

Heliocentric Distance ◽

Solar Radiation Pressure ◽

Oort Cloud ◽

Pressure Force ◽

Water Ice ◽

Cometary Dust ◽

Long Period ◽

Subsolar Point ◽

Radiation Pressure Force ◽

Period Comet

We report an identification of long-period comet C/2010 U3 (Boattini) active at a new record inbound heliocentric distance of rH &#8776; 26 au. Two outburst events around 2009 and 2017 were observed. The dust morphology of the coma and tail cannot be explained unless the Lorentz force, solar gravitation, and solar radiation pressure force are all taken into account. Optically dominant dust grains have radii of ~10 &#956;m and are ejected protractedly at speeds &#8804;50 m s&#8722;1 near the subsolar point. The prolonged activity indicates that sublimation of supervolatiles (e.g., CO, CO2) is at play. Similar to other long-period comets, the colour of the cometary dust is redder than the solar colours. We also observed potential colour variations when the comet was at 10 < rH < 15 au, concurrent with the onset of crystallisation of amorphous water ice, if any. Using publicly available and our refined astrometric measurements, we estimated the precise trajectory of the comet, propagated it backward to its previous perihelion, and found that the comet visited the planetary region ~2 Myr ago at perihelion distance q &#8776; 8 au. Thus, C/2010 U3 (Boattini) is almost certainly a dynamically old comet from the Oort cloud, and the observed activity cannot be caused by retained heat from the previous apparition. The detailed study is presented in Hui et al. (2019, AJ, 157, 162).

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Cometary Activity beyond the Planets

The Astrophysical Journal ◽

10.3847/1538-4357/ac323b ◽

2022 ◽

Vol 924 (1) ◽

pp. 37

Author(s):

Naceur Bouziani ◽

David Jewitt

Keyword(s):

Carbon Monoxide ◽

Simple Model ◽

Solar System ◽

Heliocentric Distance ◽

Cometary Nucleus ◽

Time Dependent ◽

Slow Increase ◽

Long Period ◽

Cometary Activity ◽

Period Comet

Abstract Recent observations show activity in long-period comet C/2017 K2 at heliocentric distances beyond the orbit of Uranus. With this as motivation, we constructed a simple model that takes a detailed account of gas transport modes and simulates the time-dependent sublimation of supervolatile ice from beneath a porous mantle on an incoming cometary nucleus. The model reveals a localized increase in carbon monoxide (CO) sublimation close to heliocentric distance r H = 150 au (local blackbody temperature ∼23 K), followed by a plateau and then a slow increase in activity toward smaller distances. This localized increase occurs as heat transport in the nucleus transitions between two regimes characterized by the rising temperature of the CO front at larger distances and nearly isothermal CO at smaller distances. As this transition is a general property of sublimation through a porous mantle, we predict that future observations of sufficient sensitivity will show that inbound comets (and interstellar interlopers) will exhibit activity at distances far beyond the planetary region of the solar system.

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Probable Detection of Water Ice in the Coma of the Inbound Long-period Comet C/2017 K2 (PanSTARRS)

Research Notes of the AAS ◽

10.3847/2515-5172/ac0f58 ◽

2021 ◽

Vol 5 (6) ◽

pp. 153

Author(s):

Theodore Kareta ◽

Walter M. Harris ◽

Vishnu Reddy

Keyword(s):

Water Ice ◽

Long Period ◽

Period Comet

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Effect of Storage Conditions on Storability and Antioxidant Potential of Pears cv. ‘Conference’

Agriculture ◽

10.3390/agriculture11060545 ◽

2021 ◽

Vol 11 (6) ◽

pp. 545

Author(s):

Grzegorz P. Łysiak ◽

Krzysztof Rutkowski ◽

Dorota Walkowiak-Tomczak

Keyword(s):

Mass Loss ◽

Strong Influence ◽

Storage Conditions ◽

Quality Parameters ◽

Soluble Solids ◽

Controlled Atmosphere ◽

Postharvest Diseases ◽

Market Prices ◽

Long Period ◽

The Impact

Late pear cultivars, such as ‘Conference’, can be stored for a long period if kept in good storage conditions. A three-year study (2011–2013) compared the impact of six-month storage using four technologies—normal atmosphere, normal atmosphere + 1-methylcyclopropene (1-MCP), controlled atmosphere, and controlled atmosphere + 1-MCP—on the quality parameters of ‘Conference’ pears, such as mass loss, firmness, total soluble solids, acidity, antioxidant capacity, and the incidence of diseases and disorders. Additionally, the study analysed different storage conditions in terms of profitability, based on the market prices for pears in the seasons during which the pears were stored. The storage conditions had a very strong influence on the fruit quality parameters, and were found to affect most visibly the mass loss and the incidence of postharvest diseases and disorders. The storage of ‘Conference’ pears for 180 days in normal atmosphere is not economically viable, even if the fruit is subjected to 1-MCP treatment; at the same time, it is profitable to store ‘Conference’ pears in controlled atmosphere for the same period, no matter whether 1-MCP was applied or not.

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Water Ice on the Satellite of Kuiper Belt Object 2003 EL 61

The Astrophysical Journal ◽

10.1086/503159 ◽

2006 ◽

Vol 640 (1) ◽

pp. L87-L89 ◽

Cited By ~ 44

Author(s):

K. M Barkume ◽

M. E. Brown ◽

E. L. Schaller

Keyword(s):

Kuiper Belt ◽

Kuiper Belt Object ◽

Water Ice

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Beginning of Activity in Long-period Comet C/2015 ER61 (PANSTARRS)

The Astronomical Journal ◽

10.3847/1538-3881/aa63f2 ◽

2017 ◽

Vol 153 (5) ◽

pp. 206 ◽

Cited By ~ 7

Author(s):

Karen J. Meech ◽

Charles A. Schambeau ◽

Kya Sorli ◽

Jan T. Kleyna ◽

Marco Micheli ◽

...

Keyword(s):

Long Period ◽

Period Comet

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The composition of Europa's near-surface atmosphere

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308021856 ◽

2008 ◽

Vol 4 (S251) ◽

pp. 327-328

Author(s):

Mau C. Wong ◽

Tim Cassidy ◽

Robert E. Johnson

Keyword(s):

Solar System ◽

Surface Composition ◽

Near Surface ◽

Water Ice ◽

Model Studies ◽

Surface Atmosphere ◽

Jovian Magnetosphere ◽

Ice Surface ◽

Geophysical Phenomenon ◽

Inorganic Species

AbstractThe presence of an undersurface ocean renders Europa as one of the few planetary bodies in our Solar System that has been conjectured to have possibly harbored life. Some of the organic and inorganic species present in the ocean underneath are expected to transport upwards through the relatively thin ice crust and manifest themselves as impurities of the water ice surface. For this reason, together with its unique dynamic atmosphere and geological features, Europa has attracted strong scientific interests in past decades.Europa is imbedded inside the Jovian magnetosphere, and, therefore, is constantly subjected to the immerse surrounding radiations, similar to the other three Galilean satellites. The magnetosphere-atmosphere-surface interactions form a complex system that provides a multitude of interesting geophysical phenomenon that is unique in the Solar System. The atmosphere of Europa is thought to have created by, mostly, charged particles sputtering of surface materials. Consequently, the study of Europa's atmosphere can be used as a tool to infer the surface composition. In this paper, we will discuss our recent model studies of Europa's near-surface atmosphere. In particular, the abundances and distributions of the dominant O2 and H2O species, and of other organic and inorganic minor species will be addressed.

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Crystalline water ice on the Kuiper belt object (50000) Quaoar

Nature ◽

10.1038/nature03111 ◽

2004 ◽

Vol 432 (7018) ◽

pp. 731-733 ◽

Cited By ~ 163

Author(s):

David C. Jewitt ◽

Jane Luu

Keyword(s):

Kuiper Belt ◽

Kuiper Belt Object ◽

Water Ice ◽

Crystalline Water

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Narrow-band photometry of Long Period Comets with TRAPPIST telescopes in 2019-2020

10.5194/epsc2020-419 ◽

2020 ◽

Author(s):

Youssef Moulane ◽

Emmanuel Jehin ◽

Francisco José Pozuelos ◽

Jean Manfroid ◽

Zouhair Benkhaldoun ◽

...

Keyword(s):

Solar System ◽

Production Rate ◽

Heliocentric Distance ◽

Narrow Band ◽

Maximum Activity ◽

The Sun ◽

Water Production ◽

Dust Production ◽

Long Period ◽

Water Production Rate

Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the center of the Solar system in highly elliptical orbits. In this work, we present the activity and composition evolution of several LPCs observed with both TRAPPIST telescopes (TS and TN) during the period of 2019-2020. These comets include: C/2017 T2 (PANSTARRS), C/2018 Y1 (Iwamoto), C/2018 W2 (Africano), and disintegrated comet C/2019 Y4 (ATLAS). We monitored the OH, NH, CN, C2 and C3 production rates evolution and their chemical mixing ratios with respect to their distances to the Sun as well as the dust production rate proxy (A(0)fp) during the journey of these comets into the inner Solar system. C/2017 T2 (PANSTARRS) is a very bright comet which was discovered on October 2, 2017 when it was 9.20 au from the Sun. We started observing this comet with TS at the beginning of August 2019 when it was at 3.70 au. The comet made the closest approach to the Earth on December 28, 2019 at a distance of 1.52 au and it passed the perihelion on May 4, 2020 at 1.61 au. The water production rate of the comet reached a maximum of (4,27&#177;0,12)1028 molecules/s and its dust production rate (A(0)fp(RC)) also reached the peak of 5110&#177;25 cm on January 26, 2020, when the comet was at 2.08 au from the Sun (-100 days pre-perihelion). At the time of writing, we still monitoring the activity of the comet with TN at heliocentric distance of 1.70 au. Our observations show that C/2017 T2 is a normal LPC. C/2018 Y1 (Iwamoto) is a nearly parabolic comet with a retrograde orbit discovered on December 18, 2018 by Japanese amateur astronomer Masayuki Iwamoto. We monitored the activity and composition of Iwamoto with both TN and TS telescopes from January to March 2019. The comet reached its maximum activity on January 29, 2019 when it was at 1.29 au from the Sun (-8 days pre-perihelion) with Q(H2O)=(1,68&#177;0,05)1028 molecules/s and A(0)fp(RC)= 92&#177;5 cm. These measurements show that it was a dust-poor comet compared to the typical LPCs. C/2018 W2 (Africano) was discovered on November 27, 2018 at Mount Lemmon Survey with a visual magnitude of 20. The comet reached its perihelion on September 6, 2019 when it was at 1.45 au from the Sun. We monitored the comet from July 2019 (rh=1.71 au) to January 2020 (rh=2.18 au) with both TN and TS telescopes. The comet reached its maximum activity on September 21, 15 days post-perihelion (rh=1.47 au) with Q(H2O)=(0,40&#177;0,03)1028 molecules/s. C/2019 Y4 (ATLAS) is a comet with a nearly parabolic orbit discovered on December 18, 2019 by the ATLAS survey. We started to follow its activity and composition with broad- and narrow-band filters with the TN telescope on February 22, 2019 when it was at 1.32 au from the Sun until May 3, 2020 when the comet was at a heliocentric distance of 0.90 au inbound. The comet activity reached a maximum on March 22 (rh=1.65 au) 70 days before perihelion. At that time, the water-production rate reached (1,53&#177;0,04)1028 molecules/s and the A(0)fp reached (1096&#177;14) cm in the red filter. After that, the comet began to fade and disintegrated into several fragments.

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