The Dust Environment of Main-Belt Comet P/2012 T1 (Pan-STARRS)

Moreno, F.(1); Cabrera-Lavers, A.(2,3,4); Vaduvescu, O.(2,5); Licandro, J.(2,3); Pozuelos, F.(1)

(1): Instituto de Astrofísica de Andalucía, CSIC, Granada(2): Instituto de Astrofísica de Canarias(3): Universidad de La Laguna, Tenerife(4): Gran Telescopio Canarias (GTC Project)(5): Isaac Newton Group of Telescopes, La Palma

EPSC London, September 10th, 2013

MBCs:• New comet reservoir ?• Most are dynamically stable ≈100 Myr• Recurrent activity• Earth’s water contribution

P/20

13 P5

New !!

• Characterize a new Solar System family, the MBCs, by in situ investigation

• Understand the physics of activity on MBCs • Directly detect water in the asteroid belt• Test whether MBCs are a viable source for Earth´s

water• Use MBCs as tracers of planetary system formation

and evolution

CASTALIA: A MISSION TO A MAIN-BELT COMET

A mission proposal is being prepared to be submitted to the next ESA’s M4 call:

See poster by Boehnhardt et al.

OBSERVATIONS OF P/2012 T1 (PANSTARRS)Roque de los Muchachos Observatory, La Palma

DATE (UT) DAYS AFTER PER. 

Tp=2012/09/10.9INSTRUM./TELESC. RESOLUTION m(1,1,0)

2012 Nov 13.1 63.2 PFIP/WHT 4.2m 265.8 km/px 16.9±0.2

2012 Nov 20.0 70.1 OSIRIS/GTC 10.4m 274.8 km/px 17.0±0.2

2012 Dec 13.9 94.0 OSIRIS/GTC 10.4m 307.1 km/px 17.3±0.2

2013 Jan 17.9 129.0 OSIRIS/GTC 10.4m 385.4 km/px 17.7±0.2

2013 Feb 17.9 160.0 OSIRIS/GTC 10.4m 466.4 km/px 18.9±0.2

2013 Feb 27.9 170.0 LIRIS/WHT 4.2m 485.0 km/px KS ≥22.8±0.1

2013 Feb 27.9 170.0 ACAM/WHT 4.2m 485.0 km/px --

Seeing conditions: 0.9”-1.1”

GTCWHT

P/2012 T1 (PANSTARRS)                                                                                           OSIRIS@GTC                                                                                                                                       PFIP@WHT                                                                                                                                       Red bandpasses  

Moreno et al. ApJL 2013 in press

Nov 13, 2012 Nov 20, 2012

Feb 18, 2013

Dec 14, 2012 Jan 18, 2013

Moreno et al. 2013

MONTE CARLO DUST TAIL/COMA MODEL (Moreno et al.)

DYNAMICAL/RADIATIVE CODE

- COMPUTE POSITION IN THE SKY PLANE OF PARTICLES EJECTED FROM NUCLEUS- CALCULATE TAIL BRIGHTNESS FROM LIGHT SCATTERING PROPERTIES OF DUST GRAINS

MODEL PARAMETERS:

1)EJECTION VELOCITY OF GRAINS AS FUNCTIONS OF SIZE: V(1-µ,t)=v1(t)(1-µ)1/k, k≥22)SIZE DISTRIBUTION: n(r)=Cr-α, GRAINS DISTRIBUTED IN SIZES FROM µm TO cm 3)MASS LOSS RATE4)EJECTION PATTERN

COMPARE SYNTHETIC TAIL WITH OBSERVATIONS AND COMPUTE STANDARD DEVIATION

ObservationModel

P/2012 T1(PANSTARRS)

ISOTROPICMODEL

Moreno et al. 2013

Nov.13 Nov.20

Dec.14 Jan.18

mR(Observed) mR(Model)

Oct. 11 19.8* 19.5

Feb.17 22.6 22.6*L. Buzzi (Wainscoat et al. 2012)

ObservationModel

P/2012 T1(PANSTARRS)

ANISOTROPICMODEL

I=80°Φ=260°

Moreno et al. 2013

Nov.13 Nov.20

Dec.14 Jan.18

ACTIVE AREA AT LATITUDES [-90°,-45°]

ObservationModel

(Equivalent to north hemisphere conf.)

        ISOTROPIC           ANISOTROPICP/2012 T1 (PANSTARRS) on Dec. 14th, 2012

<2.2 kg/s Water production rate from HERSCHEL/HIFI (O’Rourke et al 2013)

Moreno et al 2013

 Nov

 13, 2012

 Dec 14, 201

2

 Nov

 20, 2012

 Jan 18

, 2013

 Feb

 18, 201

3 Feb

 28, 201

3

Broad size distribution, µm to cm rangePower index -3.5Terminal velocity v 1/r1/2 ȣ

MBC P/2010 R2(La Sagra)

Moreno et al. 2011

10.9 Oct 2010 16.0 Oct 2010 26.9 Oct 2010

04.8 Nov 2010 09.8 Jan 2011

ISOTROPIC  EJECTION  MODEL  FOR  P/2010 R2 (La Sagra)

Moreno et al. 2011

Obs.Model

10.9 Oct 2010 16.0 Oct 2010 26.9 Oct 2010

04.8 Nov 2010 09.8 Jan 2011

ANISOTROPIC  EJECTION  MODEL  FOR  P/2010 R2 (La Sagra)

Moreno et al. 2011

Obs.Model

CONCLUSIONS FROM P/2012 T1 (PANSTARRS) MODELING 

- CLEAR SUSTAINED ACTIVITY PATTERN WITH DURATION 4-6  MONTHS, UNKNOWN MECHANISM, LIKELY WATER-ICE-DRIVEN ACTIVITY.

- TOTAL EJECTED MASS: 5-30×106 kg

- PARTICLE SIZE SIZE DISTRIBUTION (µm TO cm) WITH POWER LAW α = -3.5

- AN ANISOTROPIC EJECTION PATTERN WITH ACTIVE AREA AT LATITUDES [+45°,+90°] INTERVAL, OR  [-90°,-45°] IS FAVORED 

- FOR THE ANISOTROPIC PATTERN, ROTATING AXIS IS NEAR THE ORBITAL PLANE, POINTING NEAR PERIHELION DIRECTION

- SIMILAR PATTERN AS MBC P/2010 R2 (LA SAGRA)

More details: Moreno et al., ApJ, 770, L30 (2013)