zodiacal cloud: the local circumstellar disk sumita jayaraman
TRANSCRIPT
PSI Why do we study the Zodiacal Cloud?
Yields information on the formation and evolution of the interplanetary dust disk in our Solar System.
For the Solar System
For Exo-zodi Disks and Planetary For Exo-zodi Disks and Planetary SystemsSystemsDirect application to the structure of Direct application to the structure of
exo- zodi disks and planetary exo- zodi disks and planetary detection.detection.
PSI
Structures in the zodiacal cloud• Earth’s Resonant Ring
• Dynamical Asymmetries
• Dust Bands
Structures in Exo-zodiacal disks
Contents
PSI
Structures in the zodiacal cloud
• Earth’s Resonant Ring• Dynamical Asymmetries
• Dust Bands
Structures in Exo-zodiacal disks
Contents
PSI Zodiacal Peak-Flux Variation (COBE-DIRBE)
Average Trailing: 70.26 MJ/Sr
Average Leading: 68.5 MJy/Sr
Ring Flux : 1.7 MJy/Sr
(~2.5%)
PSI
At Spitzer Launch…
…After 2 years
Estimated Ring Flux: ~ 5.5 MJy/Sr (8% of Zody)
All-Sky View of RingTrailing Leading
PSI
Goals of the Spitzer Project
• Track measurements of the Earth’s Resonant Ring as Spitzer traverses it.
• Monitor variations in the Ecliptic Pole flux.
• Measure the absolutely calibrated zodiacal flux and estimate background radiation levels during the mission.
• Obtain very high resolution images of the asteroidal dust bands.
PSI Spitzer Zodical Obs.
Obs. Mode Direction of Obs. Instrument
Fast Scan-Map
~ -6 ° to +6 ° Ecliptic Latitude
MIPS
TPM Poles +90 ° and -90 ° IRAC & MIPS
TPM Ecliptic
(Trailing and Leading)
0 ° Ecliptic Latitude
ε =70 °, 90 °, 110 °
60 ° Ecliptic Latitude
ε =90°
IRAC & MIPS
PSI
Ring: Model vs Observations
EarthRing Model:
10 micron particles into
First order resonances
Spitzer Earthring Observations
2004: None
2006: 10% increase of in the NEP Flux at the maximum point
2004: None
2006 (May): 6% (1.1MJy increase in the NEP Flux)
PSI
Next Steps
• Analysis of Ecliptic Plane Observations (predicted increase in ring flux from 2.5%(1.7 MJy/Sr) of zody to 8% (5.5 MJy/Sr) of zody)
• Multiple Wavelength observations (3.6 and 70 microns) from IRAC, MIPS as well as IRS Peak-up mode.
PSI
Science Questions
• What is number density of particles in the ring?• What is the background number density required
to produce the flux variations?• What is the efficiency of capture into resonance
by an Earth-mass planet?• How do we distinguish a feature like trailing dust
cloud in ring from the planetary perturber in an exozodiacal disk?
PSI
Structures in the zodiacal cloud• Earth’s Resonant Ring
• Dynamical Asymmetries• Dust Bands
Structures in Exo-zodiacal disks
Contents
PSI Dynamical Asymmetries in the Zodiacal cloud
• Off-center shift of the zodiacal cloud shown by the pole observations.
• Warps in the cloud due to the inclination and shift measured by the variations in peak flux.
PSI
Structures in the zodiacal cloud• Earth’s Resonant Ring
• Dynamical Asymmetries
• Dust BandsStructures in Exo-Zodiacal disks
Contents
PSI
Structures in the zodiacal cloud
• Earth’s Resonant Ring
• Dynamical Asymmetries
• Dust Bands
Structures in Exo-zodiacal disks
Contents
PSI Dynamical Effects in Circumstellar Disks
• Resonant trapping – determined by the number and co-rotation of the clumps
• Recent planetesimal collisions in the disk – young dust bands
• Planetary perturbations on the disk due to one or more planets causing an inclined and off-center disk.
PSI Planetary Signatures in Observed Disks
• Resonant Rings caused by larger Planets - ε Eridani
• Off-center disk – HR4796A• Gaps in the disk due to Resonant
Trapping and scattering due to Large Planet – β Pictoris ?
• Warps in the disk due to planetary perturbations - β Pictoris.
• Bands due to stochastic collisions.
PSI What do the structures tell us?
• Location of the planet(s), eccentricity of the orbit
• Mass of the planet(s)
• Size of the dust particles (lower limits)
PSI
ε Eridani
(Quillen & (Quillen & Thornedike, Thornedike, 2002)2002)
e = 0.3
M = 10- 4 MSun
A = 40 A.U.
PSI HR 4796A (Wyatt et al. 2002)
Estimate of Planet Mass > 10 Mass of Earth with e >0.02
Flux Asymmetry ~ 5%