Using the Inner Oort Cloud to Explore the History of the Earth and Sun
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Transcript of Using the Inner Oort Cloud to Explore the History of the Earth and Sun
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Using the Inner Oort Cloud to Explore the History of the Earth
and Sun
Nathan KaibAdvisor: Tom Quinn
Collaborators: Andrew Becker, Lynne Jones
University of Washington
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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Classical Kuiper Belt (pre ~1995)
• Leftover primordial disk
• Low inclination
• Low eccentricity
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Scattered Disk• Objects that have had Neptune encounter
• Inclinations inflated
- ( 0 – ~20o)
• Higher eccentricities
- (0.1 – ~1)
• Source of short-period comets
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Outer Solar System
Oort Cloud extends to ~200,000 AU (1 pc)
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Source of Long-Period Comets
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Long-Period Comets
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The tide of the Milky Way also perturbs the Oort Cloud
(COBE, NASA)
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Galactic tide causes perihelion and inclination to oscillateAbout 2x as powerful as stellar passages (Heisler & Tremaine 1986)
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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X
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Jupiter-Saturn Barrier• Comets must have large
perihelion shift to make it past Jupiter/Saturn in one orbital period
• Only weakly bound comets will have large perihelion changes
• Jupiter/Saturn shield inner solar system from inner 20,000 AU of Oort Cloud
25000 AU
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25000 AU• LPCs near Earth only constrain outer Oort Cloud
• LPCs beyond Saturn will sample inner Oort Cloud as well
LPCs and Oort Cloud
a > 20,000 AUa > 1,000 AU~
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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SDSS-II SN Survey Observations2006 SQ372
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SDSS-II SN Survey Observations2006 SQ372
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SDSS-II SN Survey Observations2006 SQ372
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SDSS-II SN Survey Observations2006 SQ372
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Orbit Summary
a = 796 AU q = 24.2 AU i = 19.5°
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Orbital Evolution
Current orbit is transient - unstable after ~200 Myrs!
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Two Different Origin Scenarios1. Scattered Disk
sem
imaj
or a
xis
perihelion
x
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Two Different Origin Scenarios2. Oort Cloud
sem
imaj
or a
xis
perihelion
x
OC
SD
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Simulations
Scattered Disk
• 2,500 particles• Orbit distributions
based on SDO observations
• Run for 4.5 Gyrs
Oort Cloud
• 106 particles• Orbit distributions
based on Kaib & Quinn (2008) sims
• Run for 1.4 Gyrs
Non-symplectic variable timestep integrator based on SWIFT (Levison & Duncan, 1994; Kaib & Quinn, 2008)
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Results – OC Sim.(10° < i < 30°)
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Results – OC Sim. (10° < i < 30°)
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Results – OC Sim.(10° < i < 30°)
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Results – OC Sim.(10° < i < 30°)
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Results – OC Sim. (10° < i < 30°)
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Orbital Residence Map (OC)
X2006 SQ372
10° < i < 30°
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Calibrating Simulation Output
• For scattered disk simulation, assume:
- NJFCs = 250
- Dormant:Active Comet ratio = 2 (Morbidelli & Fernandez, 2006)
•For Oort Cloud simulation, assume:- LPC flux (q < 5 AU) = 1.5 comets/yr (Neslusan, 2007)
- Inner:Outer OC population ratio = 3 (Kaib & Quinn, 2008)
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Orbital Residence Map (OC)
X2006 SQ372
10° < i < 30°
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POC/PSD Map
SQ372
For 2006 SQ372: POC/PSD 16
2006 SQ372
2000 OO67
(Kaib et al., 2009)
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Origin Implications
• 2006 SQ372 is at least 16 times more likely to come from the Oort Cloud compared to the Scattered Disk
• Which region of the Oort Cloud?
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Inner Oort Cloud Origin
Semimajor axis drawdown time
vs.
Perihelion drift time
q = -10 AU Ejection by Saturnq = 10 AU a is fixed
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Inner Oort Cloud Origin
tq ~ a-2
ta ~ 100 MyrsSampled by Known LPCs
(~2.5%)
a < 800 AU20 AU < q < 30 AU
(Kaib et al., 2009)
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2006 SQ372 Summary
• 2006 SQ372 and 2000 OO67 (Elliot et al. 2005) are first detected members of inner Oort Cloud population inside planetary region
• Pan-STARRS, LSST will discover 100’s to 1000’s of similar bodies
• Population statistics will constrain structure and population size of inner Oort Cloud
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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How did the Oort Cloud form?
Pat Rawlings, NASA
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q is ~fixed, but a undergoes random walk
Planetesimal Scattering
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If q > 40 AU then growth in a stops
~ 104 AU
Inclination also changes
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Semimajor axis (AU)
Per
ihel
ion
(AU
)
(Kaib & Quinn, 2008)
t = 2 Gyrs
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Semimajor axis (AU)
Per
ihel
ion
(AU
)
(Kaib & Quinn, 2008)
x
x x x
t = 2 Gyrs
LPCs
SDKB OC
Sedna
2000 CR105
Buffy2004 VN112
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Extended Scattered Disk~ 103 AU
• If q was always big, orbit should be circular, low i
• a is too small for current external forces to shift q
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Early Strong Perturbations
Embedded Cluster Environment
(Brasser et al., 2006)
Open Cluster Environment
(Kaib & Quinn, 2008)
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Reproducing ESDOs
Med
ian
OC
Dis
tanc
e (A
U)
med
min
Kaib & Quinn (2008)
Brasser et al. (2006)
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Birthplace Consequences
Kaib & Quinn (2008)
Inner OC: a < 20,000 AUOuter OC: a > 20,000 AU
• Sun’s birth environment controls inner Oort Cloud enrichment and radial distribution
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OutlineBackground• Outer Solar System primer• Inner vs. outer Oort Cloud
Observations• Candidate inner Oort Cloud objects• Prospects from future surveys
What We Can Learn• Oort Cloud formation and the Sun’s birth
environment• Comet showers and mass extinctions
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Comet Showers
25000 AU• Rare close stellar
encounters (< 5000 AU) are able to perturb more tightly bound orbits
• The Earth is temporarily exposed to the entire Oort Cloud
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M* = MSun v = 20 km/s,
Dmin = 3000 AU t = 105 yrs
25,000 AU 4 AU
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Quantifying Shower Strength
LPC defined as q < 5 AU
M* = 0.8 MSun
v = 20 km/sDmin = 1300 AU
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v = 20 km/s
Simulation ResultsR
elat
ive
Sho
wer
Stre
ngth
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Use impulse approximation to calculate vSun for each stellar passage:
vSun = (2GM*)/(bv)
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One parameter controls shower strength
Rel
ativ
e S
how
er S
treng
th
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Finding Shower Frequency
• Use Rickman et al. (2008) stellar encounter code to generate ~106 passages
• Find dN(vSun)/dt
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One parameter controls shower strength
Rel
ativ
e S
how
er S
treng
th
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1/ ~ (vSun)-2
Rel
ativ
e S
how
er S
treng
th
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Regions Sampled by LPCs
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Effects of Solar Formation Setting
Inner Oort Cloud population very sensitive to formation environment of Sun (Fernadez & Brunini, 2000; Brasser et al., 2006; Kaib & Quinn, 2008)
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Summary• Inner Oort Cloud objects should be abundant
beyond 10-15 AU
• First few objects have been discovered
• LSST and Pan-STARRS will discover 100’s to 1000’s and constrain inner OC
• This will reveal clues about the Sun’s birthplace
• Indicate if comet showers are source of mass extinctions
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Divide LPC distribution by Oort Cloud distribution
Probability of LPC as a function of a
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semimajor axis (AU)
perih
elio
n (A
U)
Random walkIn a
Random walkIn q
Duncan et al. (1987)
30
300
3000
1000
100
1600 2500 4000 6300 1600010000