Using the Inner Oort Cloud to Explore the History of the Earth and Sun Nathan Kaib Advisor: Tom Quinn Collaborators: Andrew Becker, Lynne Jones University of Washington

Outline Background 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

Outline Background 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

Classical Kuiper Belt (pre ~1995) Leftover primordial disk Low inclination Low eccentricity

Scattered Disk Objects that have had Neptune encounter Inclinations inflated - ( 0 – ~20 o ) Higher eccentricities - (0.1 – ~1) Source of short- period comets

Outer Solar System Oort Cloud extends to ~200,000 AU (1 pc)

Source of Long-Period Comets

Long-Period Comets

The tide of the Milky Way also perturbs the Oort Cloud (COBE, NASA)

Galactic tide causes perihelion and inclination to oscillateAbout 2x as powerful as stellar passages (Heisler & Tremaine 1986)

Outline Background 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

X

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 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 AU a > 1,000 AU ~

Outline Background 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

SDSS-II SN Survey Observations 2006 SQ 372

SDSS-II SN Survey Observations 2006 SQ 372

SDSS-II SN Survey Observations 2006 SQ 372

SDSS-II SN Survey Observations 2006 SQ 372

Orbit Summary a = 796 AUq = 24.2 AUi = 19.5°

Orbital Evolution Current orbit is transient - unstable after ~200 Myrs!

Two Different Origin Scenarios 1. Scattered Disk semimajor axis perihelion x

Two Different Origin Scenarios 2. Oort Cloud semimajor axis perihelion x OC SD

Simulations Scattered Disk 2,500 particles Orbit distributions based on SDO observations Run for 4.5 Gyrs Oort Cloud 10 6 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)

Results – OC Sim. (10° < i < 30°)

Orbital Residence Map (OC) X 2006 SQ ° < i < 30°

Calibrating Simulation Output For scattered disk simulation, assume: - N JFCs = 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)

Orbital Residence Map (OC) X 2006 SQ ° < i < 30°

P OC /P SD Map SQ 372 For 2006 SQ 372 : P OC /P SD  SQ OO 67 (Kaib et al., 2009)

Origin Implications 2006 SQ 372 is at least 16 times more likely to come from the Oort Cloud compared to the Scattered Disk Which region of the Oort Cloud?

Inner Oort Cloud Origin Semimajor axis drawdown time vs. Perihelion drift time  q = -10 AU  Ejection by Saturn  q = 10 AU  a is fixed

Inner Oort Cloud Origin t q ~ a -2 t a ~ 100 Myrs Sampled by Known LPCs (~2.5%) a < 800 AU 20 AU < q < 30 AU (Kaib et al., 2009)

2006 SQ 372 Summary 2006 SQ 372 and 2000 OO 67 (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

Outline Background 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

How did the Oort Cloud form? Pat Rawlings, NASA

q is ~fixed, but a undergoes random walk Planetesimal Scattering

If q > 40 AU then growth in a stops ~ 10 4 AU Inclination also changes

Semimajor axis (AU) Perihelion (AU) (Kaib & Quinn, 2008) t = 2 Gyrs

Semimajor axis (AU) Perihelion (AU) (Kaib & Quinn, 2008) x x x x t = 2 Gyrs LPCs SD KB OC Sedna 2000 CR 105 Buffy 2004 VN 112

Extended Scattered Disk ~ 10 3 AU If q was always big, orbit should be circular, low i a is too small for current external forces to shift q

Early Strong Perturbations Embedded Cluster Environment (Brasser et al., 2006) Open Cluster Environment (Kaib & Quinn, 2008)

Reproducing ESDOs Median OC Distance (AU) med min Kaib & Quinn (2008) Brasser et al. (2006)

Birthplace Consequences Kaib & Quinn (2008) Inner OC: a < 20,000 AU Outer OC:a > 20,000 AU Sun’s birth environment controls inner Oort Cloud enrichment and radial distribution

Outline Background 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

Comet Showers 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

M * = M Sun v  = 20 km/s, D min = 3000 AU  t = 10 5 yrs 25,000 AU4 AU

Quantifying Shower Strength LPC defined as q < 5 AU M * = 0.8 M Sun v  = 20 km/s D min = 1300 AU

v  = 20 km/s Simulation Results Relative Shower Strength

Use impulse approximation to calculate  v Sun for each stellar passage:  v Sun = (2GM * )/(bv  )

One parameter controls shower strength Relative Shower Strength

Finding Shower Frequency Use Rickman et al. (2008) stellar encounter code to generate ~10 6 passages Find dN(  v Sun )/dt

One parameter controls shower strength Relative Shower Strength

1/  ~ (  v Sun ) -2 Relative Shower Strength

Regions Sampled by LPCs

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)

Summary Inner Oort Cloud objects should be abundant beyond 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

Divide LPC distribution by Oort Cloud distribution  Probability of LPC as a function of a

semimajor axis (AU) perihelion (AU) Random walk In a Random walk In q Duncan et al. (1987)