Tony Farnhamand the many contributors to

the Wirtanen Campaign

Comet WirtanenObserving Campaign

Vincent Cheng

Comet Wirtanen’s Close Approach• Wirtanen is an interesting comet

• Member of hyperactive comet family• Near twin of comet 103P/Hartley 2

• Strong candidate for mission • Close approach to Earth on Dec 16, 2018

• 4 days after perihelion• 0.0775 AU (30 Lunar Distances)• 10th closest approach in modern times

• Few of the others reached naked eye brightness

• Excellent apparition for observing!• Predicted to reach mag 3-8 (Ultimately ~4th)

The Observing Campaign• UMD organized an observing

campaign• Provide a central clearinghouse

for information of all types • Wide range of topics and

audiences• Encourage and facilitate the

acquisition, analysis and interpretation of observations

• Promote collaborations between researcher

• http://wirtanen.astro.umd.edu/• “Practiced” on comet 45P and 41P• Expanded to many other objects

Active Information Dissemination• Workshops at DPS meetings• Contact list of 128 members• Provided status reports on the

comet from recovery through departure

• Posted reports on 16 special interest web pages and social media sites

• ~25,000 members

• Holding a symposium in August to present scientific results

Tried to temper expectations on the predicted brightness

Campaign Observation Log

• Observers submitted their observing plans

• Provide information for planning, complementary observations and collaborations

• Collected information about 83 different Wirtanenobserving programs!

Citizen Science Contributions

• Collaborated with the 4*P Coma Morphology Campaign (NalinSamarasinha)

• Experienced amateurs submit their data• Get to be co-author on papers

• Received Wirtanen data from 18 observers from around the world

Comet ISON data submitted to coma morphology campaign (Samarasinha 2015)

Highlights from specific observing programs

Production Rates

• Narrowband photometry over 4 apparitions

• Water peaks pre-perihelion• Carbon species are roughly

symmetric

• Decrease in all species from apparition to apparition

• Water production gives an active fraction of 55%

• Imaging suggests much of the water comes from icy grains

David Schleicher et al. (in prep)

Pre-perihelion

Post-perihelion

Rotation State

• Phased sequences from 16 epochs • Nov 1, 2018 – Feb 8, 2019• CN coma morphology

• Rotation period ∼ 9.05 hr• Some nights capture full rotation• No evidence of period change• No evidence for NPA rotation

• Multiple CN jets

Matthew Knight et al. (in Prep)

Arecibo Radar Observations

• December 10-18, 2018• Detected the nucleus

• 1.4 x 1.1 km • Detected the large grain

coma - an extensive skirt of > 2 cm sized grains

• Biggest population of any of the recent close approach comets

1.4 hrs of rotation

Ellen Howell / University of Central Florida / Lunar & Planetary Institute

SOFIA - GREAT

• Observed Dec 14-20, 2018

• D/H ratio from HDO/ H218O

transitions• D/H = 1.61 ± 0.65 x 10-4

• Third hyperactive comet to be consisent with Earth’s D/H

Lis et al. A&A 625, 5L, 2019

Transiting Exoplanet Survey Satellite (TESS)

• Wirtanen appeared in TESS Sector 3• Sept 24-Oct 15, 2018 • 935 images at 30 min cadence

• Captured 0.5 mag outburst• 2-phase brightening• 15-20 days to fade

• Found a dust trail > 14∘ long

Tony Farnham et al. (in Prep)Wirtanen nucleus Dust trail

Monitoring for Af𝜌𝜌

0

50

100

150

200

250

300

350

400

-80 -60 -40 -20 0 20 40 60

t -T = - 6.72Afρ = 282 cm

CARA Project

Erik Bryssinck et al Mike Kelley et al

IRTF - SPEX

• Observations Dec 13- Jan 7• Similar spectra for all dates

• No H2O ice detected

• Re-evaluate hyperactivity hypothesis ?

• ∼1 𝜇𝜇m grains with <1% refractory material

• Effectively hides the ice grains at 1-1.5 AU

Silvia Protopapa et al. (in prep)

Keck II – NIRSPEC (Upgraded)

• Mid-December observations• Spatial scale ~7 km/pix

• Spatial profiles of water (H2O) and ethane (C2H6) suggest distinct outgassing sources

• Spatial profiles of coma temperatures are diagnostic of the contribution from icy grains as sources of water Boncho Bonev et al. (in prep)

Additional thanks to….

• Cordiner et al.• Atacama Large Millimeter/Submillimeter Array• Spatial maps of HCN, CH3OH and CH3CN

• Ivanova et al • Telescopes in Slovakia, Thailand, Ukraine, Russia, Tajikistan• Photometry, Spectroscopy and polarimetry

• Jehin et al• TRAPPIST North and South Telescopes • Narrowband photometry

• Venkataramani et al.• Mt Abu Telescope and 2m HCT, Hanle, India• Low- and High resolution Spectroscopy

The A’Hearn Symposium

• 6-8 August 2019 on the University of Maryland campus

• Centers around first results from the Wirtanen Campaign• Other comets and memories of Mike are welcome topics

• For more information: http://wirtanen.astro.umd.edu/symposium/index.shtml

17

New Cometary Insights from the Close Approach of 46P/Wirtanen: A Symposium in Celebration of Mike A’Hearn

Atacama Large Millimeter/Submillimeter Array

• Mid-December 2018• ALMA maps of HCN,

CH3OH and CH3CN rotational emission

• Inner 300 km of coma• First map of cometary

CH3CN

Martin Cordiner et al. (in prep)

HCN CH3OH CH3CN

IRTF - iSHELL

• December 6– Feb 5, 2018• 42 hours on source over

11 nights• Numerous species measured

• Detected: H2O, HCN, C2H2, C2H6, CH3OH, & CO

• Constrained: NH3, CH4, H2CO, & OCS

• Allows testing for potential diurnal/day-to-day compositional changes

Boncho Bonev et al. (in prep)

Ussuri Observatory (Russia)

• Polarimetry studies of the inner coma

• Change in polarization indicates dust is evolving as it expands outward

Oleksandra Ivanova et al.

TRAPPIST North and South

• December 9-10 2018• CN lightcurve• Period 9.2 hr

Mt Abu Telescope and 2m HCT, Hanle, India

• November 28, 2018• Low- and High-resolution

Spectra