Cometary Activity beyond the Planets

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.

Download Full-text

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.

Download Full-text

The Kuiper Belt

Symposium - International Astronomical Union ◽

10.1017/s007418090004643x ◽

1994 ◽

Vol 160 ◽

pp. 31-44

Author(s):

Jane Luu

Keyword(s):

Solar System ◽

Kuiper Belt ◽

Cometary Nucleus ◽

Outer Solar System ◽

Short Period Comet ◽

Short Period ◽

Lower Limits ◽

Period Comet

The existence of a belt of comets in the outer solar system (the “Kuiper belt”) has been postulated for a variety of reasons, including the need for a source for the short-period comets. The existence of the belt seems supported by the discoveries of the trans-Neptunian objects 1992 QB1, 1993 FW, 1993 RO, 1993 RP, 1993 SB, and 1993 SC. If these objects are members of the Kuiper belt, crude lower limits on the belt population can be established from the discoveries. The Kuiper belt comets are likely to be primordial remnants of the disk from which the solar system accreted. According to the current theories of cometary nucleus evolution, these objects are expected to possess mantles (“irradiation mantles”) which are different from mantles of comets which have been heated to the point of sublimation (“rubble mantles”). Kuiper belt comets on their way to short-period comet orbits may exist among the Centaur objects.

Download Full-text

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

10.5194/epsc2021-327 ◽

2021 ◽

Author(s):

David Jewitt ◽

Yoonyoung Kim ◽

Max Mutchler ◽

Jessica Agarwal ◽

Jing Li ◽

...

Keyword(s):

Mass Loss ◽

Heliocentric Distance ◽

Kuiper Belt ◽

Near Surface ◽

Water Ice ◽

Distance Range ◽

Long Period ◽

Effective Particle ◽

Lag Effect ◽

Period Comet

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;

Download Full-text

Dynamical interactions of the solar system with massive nebulae

International Astronomical Union Colloquium ◽

10.1017/s0252921100083780 ◽

1985 ◽

Vol 83 ◽

pp. 31-41

Author(s):

W.M. Napier

Keyword(s):

Solar System ◽

Molecular Clouds ◽

The Sun ◽

Natural Consequence ◽

Long Period ◽

Close Encounters ◽

Spiral Arm ◽

Qualitative Discussion ◽

Large Disturbance ◽

Period Comet

AbstractThe effects of encounters with massive nebulae on the long-period comet population are examined, paying particular attention to the uncertainties in the data. An earlier conclusion, that the long-period comet system is dynamically unstable, is upheld. Whether replenishment by unbinding from a dense inner comet cloud is a viable hypothesis awaits detailed modelling, but a qualitative discussion is given which argues tentatively against it. If comets occur in molecular clouds, however, their capture into temporarily bound Solar System orbits is a natural consequence of close encounters for realistic velocities and potentials. A large disturbance or capture may have occurred a few Myr ago as the Sun emerged from the Orion spiral arm.

Download Full-text

The Rosetta mission orbiter science overview: the comet phase

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2016.0262 ◽

2017 ◽

Vol 375 (2097) ◽

pp. 20160262 ◽

Cited By ~ 35

Author(s):

M. G. G. T. Taylor ◽

N. Altobelli ◽

B. J. Buratti ◽

M. Choukroun

Keyword(s):

Remote Sensing ◽

Solar System ◽

Cometary Nucleus ◽

Rosetta Mission ◽

Interstellar Material ◽

The Relationship ◽

Mission Operations ◽

Comet 67P ◽

Cometary Activity

The international Rosetta mission was launched in 2004 and consists of the orbiter spacecraft Rosetta and the lander Philae. The aim of the mission is to map the comet 67P/Churyumov–Gerasimenko by remote sensing, and to examine its environment in situ and its evolution in the inner Solar System. Rosetta was the first spacecraft to rendezvous with and orbit a comet, accompanying it as it passes through the inner Solar System, and to deploy a lander, Philae, and perform in situ science on the comet's surface. The primary goals of the mission were to: characterize the comet's nucleus; examine the chemical, mineralogical and isotopic composition of volatiles and refractories; examine the physical properties and interrelation of volatiles and refractories in a cometary nucleus; study the development of cometary activity and the processes in the surface layer of the nucleus and in the coma; detail the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System; and characterize asteroids 2867 Steins and 21 Lutetia. This paper presents a summary of mission operations and science, focusing on the Rosetta orbiter component of the mission during its comet phase, from early 2014 up to September 2016. This article is part of the themed issue ‘Cometary science after Rosetta’.

Download Full-text

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).

Download Full-text

Comets : A Key to Solar System Formation

Zeitschrift für Naturforschung A ◽

10.1515/zna-1989-1001 ◽

1989 ◽

Vol 44 (10) ◽

pp. 867-876

Author(s):

Horst Uwe Keller

Keyword(s):

Solar System ◽

Heliocentric Distance ◽

Planetary System ◽

Cometary Nucleus ◽

Interplanetary Dust ◽

Dust Particles ◽

Interplanetary Dust Particles ◽

The Earth ◽

Comet Halley

Abstract Four lines of information on comets are discussed: their orbits, their relation to other bodies of the planetary system, their physical state and chemical composition, and implications of recent observations of the nucleus of comet Halley. The in situ measurements during the flybys of comet Halley strongly support the assumption that comets are members of the solar system and were created during its formation. The region (heliocentric distance) of their formation is, however, still difficult to assess. The size, shape, and topography of the cometary nucleus suggest that it was formed from relatively large subnuclei in a region of the primordial solar nebula where relative velocities were sufficiently small. There are indications that some of the interplanetary dust particles in the Earth atmosphre may originate from comets.

Download Full-text

Unusual polarimetric properties for interstellar comet 2I/Borisov

Nature Communications ◽

10.1038/s41467-021-22000-x ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

S. Bagnulo ◽

A. Cellino ◽

L. Kolokolova ◽

R. Nežič ◽

T. Santana-Ros ◽

...

Keyword(s):

Solar System ◽

Physical Characteristics ◽

Dust Particles ◽

The Sun ◽

Large Telescope ◽

European Southern Observatory ◽

Long Period ◽

Very Large Telescope ◽

Cometary Activity

AbstractSo far, only two interstellar objects have been observed within our Solar System. While the first one, 1I/‘Oumuamua, had asteroidal characteristics, the second one, 2I/Borisov, showed clear evidence of cometary activity. We performed polarimetric observations of comet 2I/Borisov using the European Southern Observatory Very Large Telescope to derive the physical characteristics of its coma dust particles. Here we show that the polarization of 2I/Borisov is higher than what is typically measured for Solar System comets. This feature distinguishes 2I/Borisov from dynamically evolved objects such as Jupiter-family and all short- and long-period comets in our Solar System. The only object with similar polarimetric properties as 2I/Borisov is comet C/1995 O1 (Hale-Bopp), an object that is believed to have approached the Sun only once before its apparition in 1997. Unlike Hale-Bopp and many other comets, though, comet 2I/Borisov shows a polarimetrically homogeneous coma, suggesting that it is an even more pristine object.

Download Full-text

Models of comets with strongly variable nongravitational effects

International Astronomical Union Colloquium ◽

10.1017/s0252921100031705 ◽

1999 ◽

Vol 173 ◽

pp. 381-387

Author(s):

M. Królikowska ◽

G. Sitarski ◽

S. Szutowicz

Keyword(s):

Cometary Nucleus ◽

Spin Axis ◽

Reactive Force ◽

Orbital Elements ◽

Cometary Nuclei ◽

Short Period ◽

Basic Parameters ◽

Polar Radius ◽

Cometary Activity ◽

Nongravitational Effects

AbstractThe nongravitational motion of five “erratic” short-period comets is studied on the basis of published astrometric observations. We present the precession models which successfully link all the observed apparitions of the comets: 21P/Giacobini-Zinner, 31P/Schwassmann-Wachmann 2, 32P/Comas Solá, 37P/Forbes, and 43P/Wolf-Harrington. We used the Sekanina's forced precession model of the rotating cometary nucleus to include the nongravitational terms into equations of the comet's motion. Values of six basic parameters (four connected with the rotating comet nucleus and two describing the precession of spin-axis of the nucleus) have been determined along the orbital elements from positional observations of the comets. The solutions were derived with additional assumptions which introduce instantaneous changes of modulus of reactive force,Aand of maximum of cometary activity with respect to perihelion time. The present precession models impose some contraints on sizes and rotational periods of cometary nuclei. According to our solutions the nucleus of 21P/Giacobini-Zinner with oblateness along the spin-axis of about 0.32 (equatorial to polar radius of 1.46) is the most oblate among five investigated comets.

Download Full-text

Covering of cometary nucleus by refractory crust and its evolution into asteroid-like body

International Astronomical Union Colloquium ◽

10.1017/s0252921100031675 ◽

1999 ◽

Vol 173 ◽

pp. 365-370

Author(s):

Kh.I. Ibadinov

Keyword(s):

Laboratory Experiments ◽

Cometary Nucleus ◽

Sublimation Rate ◽

Cometary Nuclei ◽

Short Period Comet ◽

Short Period ◽

Brightness Decrease ◽

Crust Thickness ◽

Ice Sublimation ◽

Period Comet

AbstractFrom the established dependence of the brightness decrease of a short-period comet dependence on the perihelion distance of its orbit it follows that part of the surface of these cometary nuclei gradually covers by a refractory crust. The results of cometary nucleus simulation show that at constant insolation energy the crust thickness is proportional to the square root of the insolation time and the ice sublimation rate is inversely proportional to the crust thickness. From laboratory experiments resulted the thermal regime, the gas productivity of the nucleus, covering of the nucleus by the crust, and the tempo of evolution of a short-period comet into the asteroid-like body studied.

Download Full-text