SPS Colloquium Talk 2011

Comets: Delving Into the Heart of the Matter

By Ryan Laird

PhD Supervisor: Dr Stephen Lowry

School of Physical SciencesPostgraduate ColloquiumFriday 23rd September, 2011 1

Survey of Ensemble Physical Properties of Cometary Nuclei

(SEPPCoN)

Survey of Ensemble Physical Properties of Cometary Nuclei

(SEPPCoN)

Optical ObservationsOptical ObservationsOptical ObservationsOptical Observations

SEPPCoN

S. C. Lowry (UKC) (Supervisor)Y. Fernández (UCF)M. F. A’Hearn (U-Md) J. M. Bauer (JPL) H. Campins (UCF) A. Fitzsimmons (QUB) O. Groussin (LAM) H. Hsieh (QUB) M. Kelley (U-Md) P. Lamy (LAM)

J. Licandro (IAC, UL) C. M. Lisse (JHU/APL) K. J. Meech (UH-IfA) J. Pittichová (UH-IfA, AI) W. T. Reach (Caltech/IPAC) C. Snodgrass (ESO/MPI)I. Toth (K. Obs.) H. A. Weaver (JHU/APL)P. Weissman (JPL)

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SEPPCoNSEPPCoN

School of Physical Sciences Colloquium 2011By Ryan Laird

• SEPPCoN (Survey of the Ensemble Physical Properties of Cometary Nuclei) This is a survey to understand the sizes, albedos, colours, shapes, and spin rates of Jupiter-Family comets - critical for understanding their origins and evolutionary processes as they dynamically evolve from the Kuiper Belt.

• Spitzer Large Proposal – 100 hrs – MIPS & IRS imaging obtained during SST Cycle 3, July 2006 – July 2007

• Ground based optical data (3.5-10m telescopes), ~42 nights – BVRI photometry

School of Physical Sciences Colloquium 2011Ryan Laird

SEPPCoN SEPPCoN –– Ground-Based Optical Campaign Ground-Based Optical Campaign (400-790 nm), CCD imaging

ESO – 8.2m VLT Antu, FORS

(3 nights)

ESO – 3.6m NTT with

EMMI/EFOSC2 (11 nights)

Apache Point Observatory ARC 3.5m, New Mexico

(1.5 nights)

2m Robotic Liverpool

Telescope, La Palma (0.1 night)

Palomar Observatory: 5m Hale Telescope with LFC, California (14.2 nights)

UH 2.2m (2 nights) and Keck 10m (2 nights), Mauna Kea

2.6m, Nordic Optical Telescope, La Palma (0.2 nights)

SOAR 4.1m at Cerro Pachón, Chile (2.8 nights).

4.2m William Herschel

Telescope, La Palma (5

nights)

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Jupiter-Family CometsJupiter-Family Comets

Jupiter-Family Comets

• Orbital period < 20 years

• Direct orbits with inclination < 40 degrees

• Most observationally accessible of the comet groups

• Heliocentric distances 3 AU <Rh< 7 AU

• Tisserand parameter, 2 <TJ< 3 => dynamically distinct group. For a small body with semimajor axis, a, eccentricity, e, and inclination, i, relative to the orbit of a perturbing larger body (Jupiter) with semimajor axis aP


JFCs6P/d'Arrest 7P/Pons-Winnecke 11P/Tempel-Swift-LINEAR 14P/Wolf 15P/Finlay 16P/Brooks 222P/Kopff 31P/Schwassmann-Wachmann 2 32P/Comas Sola33P/Daniel37P/Forbes43P/Wolf-Harrington47P/Ashbrook-Jackson48P/Johnson50P/Arend51P/Harrington-A54P/de Vico-Swift56P/Slaughter-Burnham57P/du Toit-Neujmin-Delporte 62P/Tsuchinshan 168P/Klemola69P/Taylor74P/Smirnova-Chernykh77P/Longmore78P/Gehrels 279P/du Toit-Hartley

89P/Russell 293P/Lovas 194P/Russell 4101P/Chernykh107P/Wilson-Harrington 113P/Spitaler118P/Shoemaker-Levy 4119P/Parker-Hartley 120P/Mueller 1 121P/Shoemaker-Holt 2123P/West-Hartley124P/Mrkos 127P/Holt-Olmstead129P/Shoemaker-Levy 3 130P/McNaught-Hughes131P/Mueller 2132P/Helin-Roman-Alu 2137P/Shoemaker-Levy 2138P/Shoemaker-Levy 7139P/Vaisala-Oterma141P/Machholz 2 143P/Kowal-Mrkos144P/Kushida 146P/Shoemaker-LINEAR148P/Anderson-LINEAR149P/Mueller 4152P/Helin-Lawrence159P/LONEOS

160P/LINEAR162P/Siding Spring163P/NEAT168P/Hergenrother169P/NEAT171P/Spahr172P/Yeung173P/Mueller 5 P/1998 VS24 (LINEAR)P/1999 WJ7 (Korlevic) (203P)P/2000 Y3 (Scotti) P/2001 CV8 (LINEAR) (216P) P/2001 R6 (LINEAR-Skiff)P/2001 YX127 (LINEAR) (228P) P/2002 JN16 (LINEAR) (221P)P/2002 LZ11 (LINEAR) (219P)P/2002 O8 (NEAT) (215P) P/2002 S1 (Skiff) (223P)P/2002 X2 (NEAT)P/2003 HT15 (LINEAR)P/2003 KV2 (LINEAR) (197P) P/2003 O3 (LINEAR)P/2003 S1 (NEAT)P/2003 S2 (NEAT)P/2004 A1 (LONEOS) P/2004 DO29 (Spacewatch-LIN.) P/2004 F3 (NEAT) P/2004 H2 (Larsen)

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Jupiter-Family CometsJupiter-Family Comets

P/2004 T1 (LINEAR-NEAT) P/2004 V3 (Siding Spring) P/2004 V5 A+B (LINEAR-Hill) P/2004 VR8 (LONEOS)P/2005 GF8 (LONEOS)P/2005 JD108 (Catalina-NEAT) P/2005 JQ5 (Catalina)P/2005 K3 (McNaught)P/2005 L4 (Christensen)P/2005 Q4 (LINEAR)P/2005 R1 (NEAT)P/2005 R2 (Van Ness) (213P)P/2005 S3 (Read)P/2005 T5 (Broughton)P/2005 W3 (Kowalski) C/2005 W2 (Christensen)P/2005 Y2 (McNaught)P/2005 XA54 (LONEOS-Hill)


SEPPCoN SEPPCoN –– Survey of Ensemble Physical Properties of Cometary Nuclei Survey of Ensemble Physical Properties of Cometary Nuclei

1. Use complementary ground-based visible-wavelength and thermal-IR observations to derive the nuclei’s geometric albedos and sizes.

2. Test for correlations between the albedos and other properties of the nuclei, such as composition and dynamical age.

3. Compare the cometary albedo distribution with those of Centaurs, TNOs, Trojans, and extinct comet candidates to test the proposed evolutionary processes.

4. Resolve once and for all the question of just how safe it is to assume an albedo for a cometary nucleus. A cautionary tale is the TNO albedo story, where 4% was long assumed and turned out to be very wrong.

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SEPPCoN SEPPCoN –– Survey of Ensemble Physical Properties of Cometary Nuclei Survey of Ensemble Physical Properties of Cometary Nuclei

5. Investigate the colour distribution of JFCs to help constrain the composition and surface processes of JFC nuclei.

6. Determine the rotation and bulk density of JFC nuclei to compare with other minor bodies to investigate any possible trends.

7. Determine the most robust size distribution of JFCs in relation to ascertaining the KBO size distribution.

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Size DistributionSize Distribution

Size and Rotation Period Distributions: • Is it influenced by collisional history? By erosion? By fragmentation? Is it at all similar to Trojans? • Is there a paucity of sub-km objects?• How does the spin-rate distributions compare to KBOs, and what can be learned about their internal structure?• We investigate the size distribution down to ~ 1km. Size distributions truncated < 2km. Most of targets < 2km by observational and theoretical indications (Meech at al. 2004, Samarasinha 2001) so to constrain low end of size distribution is dependent on sample.


One of several size distributions estimated for JFCs (Weissman & Lowry 2003).

Rotation and Bulk Density• We can use the rotation period and elongation of the nucleus to put limits on the bulk density of the nucleus (Pravec & Harris. 2000).

• Time-series photometry and light curve amplitude compared between JFCs and all available data for KBOs and Centaurs.

• Together this can reveal information about the internal structure of minor body populations.

Rotation and Bulk DensityRotation and Bulk Density

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Available cometary nucleus light-curve data (Snodgrass, 2006). Comet data are shown as open circles, KBOs as filled circles and Centaurs as filled triangles. Like comets, KBOs all lie above 0.6 gcm-3 with the exception of the large object 2003 EL61.

Summary of SEPPCoN findings

Summary of SEPPCoN findingsSummary of SEPPCoN findings

To date we have attempted observations of 91% of our sample of 100 JFCs, at least 64 of those were successfully detected. Of those 64 detected comets just 16 showed signs of outgassing. In most cases the comets were at heliocentric distances between 3.0 and 6.5 AU.

Examples of processed optical R-band imaging of three comets successfully detected at the ESO 3.6-m NTT telescope in May 2007. Comet Lovas 1 shows clear signs of activity, whereas comets NEAT and Klemola appear unresolved.

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EPSC Abstract

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Investigating colours allows us to constrain composition and surface properties.

Groupings have been reported between Centaurs and KBOs.

Large scale survey from ESO imply a taxonomy of KBOs based on their composition.

We look for trends in JFC nuclei, developing compositional links with KBOs.

Colour DistributionColour Distribution

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Lamy et al. 2004 – review of 65 ecliptic comets. Albedo range for cometary nuclei narrow, namely 0.02 to 0.06.

Looking for trends in this narrow range is difficult.

Evolutionary processes such as solar-UV, cosmic ray darkening, space weathering, collisions, and resurfacing from outgassing can alter the original albedo of a comet.

Hypotheses show a trend of albedo with time that elapsed since the object left the KBO region.

AlbedoAlbedo

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Size DistributionSize Distribution

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Reflectance Properties: – How good is the 4% albedo assumption?

– What are the colour and albedo distributions?

Thermal Properties: – Do all comets have the same thermal properties (e.g. like Tempel 1) ?

(See Lowry et al. 2008. In The Solar System Beyond Neptune)

SPS Colloquium Talk 2011

Science

Transcript of SPS Colloquium Talk 2011