THE 2002/2003 APPARITION OF 67P/CHURYUMOV-

GERASIMENKO

THE 2002/2003 APPARITION OF 67P/CHURYUMOV-

GERASIMENKO

Mark R. Kidger

Instituto de Astrofísica de Canarias

Introduction• 67P/Churyumov-Gerasimenko is the probable

new target of the ROSETTA mission after the failure of ROSETTA to meet the strict launch window for an Ariane-boosted encounter with 46P/Wirtanen.

• 67P is a comparatively recent visitor to the inner solar system having had q=4.0AU prior to 1840 and q>2.75AU until a Jupiter encounter in 1959.

• Its high level of activity is a potential risk for ROSETTA which must survive in the cometary environment for 2 years.

Introduction• The recent large downward jumps in perihelion

distance are the drivers of 67P/Churyumov-Gerasimenko's high level of activity.– The jump in “q” leads to increased pressure from

sublimation of volatiles that “blows off” the insulating layer of surface dust that suffocates activity in evolved comets and causes thermal inertia.

• The light curve, photometric evolution and morphology of the comet during the 2002/2003 apparition are studied through the observations of the international Spanish language "Observadores_cometas" group.

46P/Wirtanen v 67P/Churyumov-Gerasimenko

• 46P/Wirtanen– Discovery, 1947 Dec. 02– 10 apparitions, 9 observed (1980 missed)– Period 5.44 years, q=1.06AU

• 67P/Churyumov-Gerasimenko– Discovery, 1969 Sep. 11 (initially mistaken for 32P Comas-Solá)– 6 apparitions– Period 6.57 years, q=1.29AU

• 67P is a much larger object. Tancredi et al. (2000, A&AS, 146, 73) estimate radii of:– 46P, 0.7km, H46P, 0.7km, H00=18.4=18.4– 67P, 2.5km, H67P, 2.5km, H00=15.6=15.6– Both are high-quality Q=1, multi-return estimatesBoth are high-quality Q=1, multi-return estimates.

The light curves• 67P has shown outbursts at perihelion

– 1996, at T-5d., amplitude 1.5 mags.– 2002, at T-1(?)d, amplitude 1.5 mags.– Seiichi Yoshida finds post-perihelion fits of

• 1996: m1 = 9.3 + 5 log + 11.5 log r• 2002: m1 = 9.3 + 5 log + 15.0 log r

• 46P may have shown a 3 magnitude outburst in late September 2002 (but not but not supported by Spanish/Italian CCD datasupported by Spanish/Italian CCD data)– Seiichi Yoshida finds post-perihelion fits of

• 1996: m1 = 8.5 + 5 log + 27.0 log r• 2002: m1 = 8.4 + 5 log + 25.0 log r

• Both comets have rather consistent light curves between the last two returns.– Their activity for the ROSETTA encounter in 2014

should be predictable.– We should expect a new outburst of 67P at

perihelion in early 2009 prediction for an outburst during the encounter (exciting science!!exciting science!!).

• 46P/Wirtanen shows a much larger decrement with “r” it is a much more evolved object with a thicker surface mantle and thus high thermal inertia.

Know 67P!

• There is an international campaign to observe and characterise 67P in preparation for ROSETTA.

• The “Observadores-Cometas” group has targeted 67P in a effort to provide valuable data.– Observers in 6 countries who observe with

standard methods (see Saturday’s talksee Saturday’s talk).

67P: Morphology

67P shows a faint tail even at perihelion. It gets brighter with time, but note that the November image has 3 times as much exposure!

December 28th 2002: Ramón Naves & Montse Campàs

The gas tail seems offset, but this is due to an extension of the comaa to the south-west.

Note how the coma becomes more difuse as “r” increases.

Spanish CCD lightcurve: 2002/2003

• Maximum brightness is after perihelion.

• Small outburst at the end of December 2002?

67P/Churyumov-Gerasimenko10

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181-8-02 31-8-02 1-10-02 31-10-02 1-12-02 31-12-02 31-1-03 2-3-03 2-4-03 2-5-03

R

10"

20"

30"

40"

60"

Perihelion

Spanish CCD lightcurve: 2002/2003

• Outburst at or a few days after perihelion.

• Sharp change of slope in mid-December 2002 (T+120d).

67P/Churyumov-Gerasimenko9

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171-8-02 31-8-02 1-10-02 31-10-02 1-12-02 31-12-02 31-1-03 2-3-03 2-4-03 2-5-03

R -

5 lo

g D

elta

10"-5log Delta

20"-5log Delta

30"-5log Delta

40"-5log Delta

60"-5log Delta

Perihelion

Spanish CCD lightcurve: 2002/2003

• Initial rapid fade with “r” in 10” aperture: n=15.5.

• Slope change at r=1.85AU n=6.7 (10” d=11500km).

67P/Churyumov-Gerasimenko9

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r (AU)

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og

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10"-5log Delta

20"-5log Delta

30"-5log Delta

40"-5log Delta

60"-5log Delta

2 3 4 5

Large change in 10” aperture at 1.85AU important change in gas emission from nucleus, but it is increasingly less defined with increasing aperture.

For 30-60”, n7 (<1.85AU), and n6 (r>1.85AU).

The coma profile

• The coma profile shows a steeper brightness index with radius further from perihelion.

67P/Churyumov-Gerasimenko: Coma profiles corrected for Delta

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Aperture (")

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5-4-03

The coma profile (II)

• The coma radial brightness index decreases from 1.5 at perihelion to 3.3 at T+240 days.

67P/Churyumov-Gerasimenko

R2 = 0.5553

-4.0

-3.5

-3.0

-2.5

-2.0

-1.5

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1/8/02 31/8/02 1/10/02 31/10/02 1/12/02 31/12/02 31/1/03 2/3/03 2/4/03

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ma

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ex

Increasing Degree of Condensation

The coma profile (III)

• The amount of light in the centre of the coma decreases considerably with time much less “dust” close to the nucleus.

67P/Churyumov-Gerasimenko: Mean coma profile fits

R = 14.73*Aperture-0.063

r2 = 0.9878

R = 19.87*Aperture-0.098

r2 = 0.9983

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Aperture (")

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Potencial (18-8-02)

Potencial (4-4-03)

Conclusions• The light curve of 67P seems to be rather

constant between returns.• The last two returns have shown a 1.5 mag

outburst at T5 days Exciting science for Exciting science for ROSETTAROSETTA.

• The activity of the nucleus shows a major breakpoint at r1.8AU within radius=5700km.

• The degree of condensation of the nucleus declines rapidly after perihelion.