The Structure of the Kuiper Belt from Observations and Simulations

Samantha Lawler Plaskett Fellow NRC-Herzberg, Victoria, BC, Canada Understanding the Structure of the Kuiper Belt

• A Brief History of Kuiper Belt Discoveries • The Scene of the Crime (Spoiler alert: Neptune did it) • Here be Dragons: Observational Biases (and what you can do about them) • Clues from the Detailed Structure • Populations, sub-resonances, beards or trails, Planet 9? • Lingering Mysteries • Warped plane, high pericenter KBOs • Migration in other solar systems? Pluto: The Original KBO

C. Tombaugh

Discovered 62 years before 2nd KBO! Pluto: The Original KBO

C. Tombaugh New Horizons Mission to Pluto New Horizons Mission to Pluto Pluto: Not a planet (neener neener) Pluto: Not a planet (neener neener) Pluto is in a Mean-Motion Resonance

120 kyr integration on Naval Ordnance Research Calculator

Cohen & Hubbard (1964) Pluto is in a Mean-Motion Resonance

Malhotra (1997) The Kuiper Belt is certainly not boring!

Pluto

Minor Planet Center Database The Kuiper Belt is certainly not boring!

1996

Minor Planet Center Database The Kuiper Belt is certainly not boring!

1998

Minor Planet Center Database The Kuiper Belt is certainly not boring!

2007

Minor Planet Center Database The Kuiper Belt is certainly not boring!

yesterday

Minor Planet Center Database Kuiper Belt Structure

Bannister et al, incl Lawler (subm) Moving lots of small planetesimals adds up

proto- Kuiper Belt How to Build the Kuiper Belt

t=0

t=present

Malhotra 1995

Hahn & Malhotra 2005 Smooth Migration How to Build the Kuiper Belt

t=0

t=present

Malhotra 1995

Hahn & Malhotra 2005 How to Build the Kuiper Belt

The Nice Model Tsiganis et al. 2005 But…what about observational biases?

Bannister et al, incl Lawler (subm) Observing biases are important: 10 times farther is 10,000 times fainter Most time spent at farthest distances Observing biases are important: KBOs have diﬀerent distributions on the sky

Gladman, Lawler et al. 2012 Observing biases are important: Where you find KBOs on the sky is just as important as where you look and *don’t* find KBOs Solution: Publish your survey biases! The Outer Solar System Origins Survey (OSSOS): A thoroughly careful way to find KBOs

Mike Alexandersen, Michele Bannister, Susan Benecchi, Ying-Tung Chen, Audrey Delsanti, Wesley Fraser, Brett Gladman, Will Grundy, Aurelie Guilbert-Lepoutre, Stephen Gwyn, Daniel Hestroﬀer, Wing Ip, Marian Jakubik, Lynne Jones, Nathan Kaib, JJ Kavelaars, Pavlo Korsun, Simon Krughoﬀ, Irina Kulyk, Pedro Lacerda, Samantha Lawler, Matthew Lehner, Edward Lin, Patryk Lykawka, Ruth Murray-Clay, Keith Noll, Alex Parker, Jean-Marc Petit, Rosemary Pike, Philippe Rousselot, Meg Schwamb, Cory Shankman, Pierre Vernazza, Kat Volk, Shiang-Yu Wang OSSOS uses the Canada-France-Hawaii Telescope

Megacam is a HUGE, wide-ﬁeld camera. Perfect for KBO surveys. Megacam ﬁeld of view 1 degree

1 degree KBOs move minute-to-minute on the sky, because of Earth’s orbit!

M. Bannister Strategy: -Observe 2 months before “opposition” -Observe at opposition -Observe 2 months after opposition -Need VERY good orbital measurements to not lose them

Parallax: get distance, orbits, precise predictions for next obs. S. Gwyn DebiasingDebiasing Example: Example: Plutinos Plutinos

CFEPS = precursor to OSSOS

Gladman,Gladman, Lawler, Lawler et al.al. (2012)(2012)

Gladman,Gladman, LawlerLawler, et et al. al. (2012) (2012)

Gladman,Gladman, LawlerLawler, et et al. al. (2012) (2012) Debiasing Kuiper Belt Observations

KBOs

Lawler (2014)/Petit et al. (2011) Debiasing the Survey

Every dot represents a real Kuiper Belt Object.

We know the number of Kuiper Belt Objects bigger than 100 km, and statistical distribution. Thanks, OSSOS!

Lawler (2014) Detailed Resonant Structure Holds Clues about Neptune’s Migration

Lawler et al (2014)/Petit et al. (2011) Detailed resonant structure: Population ratios

5:2 Predictions from 3:2 2:1 simulations Hahn & Malhotra (2005); Levison et al (2008); Pike, Lawler et al. (2017)

do not match debiased observations Gladman, Lawler et al (2012); Volk et al, incl Lawler (2016) Grainy migration?

Kaib & Sheppard (2016) Nesvorny et al. (2016) Grainy migration makes “Trails” in simulations

Kaib & Sheppard (2016) Nesvorny et al. (2016)

Nice Model makes“Beards” in simulations

Pike & Lawler (2017) Beards or Trails, which matches debiased data? Beards or Trails, which matches debiased data?

EXTREME

OBSERVATIONALBIASES! What does OSSOS have to say about Planet 9?

Orbits from Minor Planet Center Database

Batygin & Brown (2016) High-q KBOs are aligned by Planet 9 Neptune Sheppard & Trujillo (2016) EXTREME UNPUBLISHED OBSERVATIONAL BIASES!

Neptune Sheppard & Trujillo (2016) Numerical Experiment #1:

What does this HUGE (10 x Earth mass) Planet 9 do to the orbits in the distant Kuiper Belt, and can we detect it with OSSOS? Numerical Experiment #1:

What does this HUGE (10 x Earth mass) Planet 9 do to the orbits in the distant Kuiper Belt, and can we detect it with OSSOS? Orbits are more circular and farther away from Neptune

These would be VERY hard to observe. Always far away = always faint. Lawler et al. (2017) Numerical Experiment #1: What does this HUGE (10 x Earth mass) Planet 9 do to the orbits in the Kuiper Belt?

Many orbits are tilted to high angles, some are RETROGRADE (backwards)

Lawler et al. (2017) Survey Simulator

Lawler et al. (2017) Detectable? Numerical Experiment #1: Big differences in models Can we observe these differences with OSSOS?

Lawler et al. (2017) Numerical Experiment #1: No difference after Survey Simulator!

q [AU]

Lawler et al. (2017)

All the difference is in the faint part. We can’t see it in OSSOS. Bugger. Numerical Experiment #1: We see no orbital alignment by Planet 9 = X Lawler et al. (2017) Numerical Experiment #2:

What does this HUGE (10 x Earth mass) Planet 9 do to the orbits of known KBOs? Shankman et al, incl Lawler (2017a) Numerical Experiment #2:

Planet 9 doesn’t keep KBOs aligned. This was the entire reason it was proposed! Observational Experiment #1:

We discover an equivalent group of distant high-q KBOs using OSSOS

Are they aligned by Planet 9? NOPE.

Shankman et al. (2017b)/Bannister et al. (subm) Observational Experiment #1:

We ﬁnd no evidence high-q KBOs are aligned. OSSOS Planet 9 Summary

Planet 9 does not produce alignment in simulated KBOs

Planet 9 does not keep known KBOs aligned

Newly discovered high-q KBOs are not aligned Lingering Mysteries

The mean plane of the Kuiper Belt is warped at large distances

does not matches match theory theory

Volk & Malhotra 2017

Could be an undiscovered Mars-size body! Lingering Mysteries If no Planet 9, how do you produce high-q KBOs?

= pericenter distance

Shankman et al. 2017a Producing high-q KBOs is hard (but lots of theories)

• an extra planet? (Gladman et al. 2002, Brown et al. 2004, Gomes et al. 2006)

• a rogue: once orbiting, gone now (Gladman & Chan 2006)

• present-day planet: nine? (Brown 2004, Gomes et al. 2006, Soares & Gomes 2013, Sheppard & Trujillo 2014, Batygin & Brown 2016, half the community in 2016-2017)

• capture from another star’s system? (Kenyon & Bromley 2004; Jílková et al. 2015)

• a stellar ﬂyby? (Kenyon & Bromley 2004; Morbidelli & Levison 2004, Kaib et al. 2009)

• perturbations in the Sun’s birth nebula? (Brasser et al. 2012, Brasser & Schwamb 2014)

• self-gravitation in the planetesimal disk? (Madigan & McCourt 2016)

• diffusion from the inner Oort cloud? (Bannister et al. 2017) Connecting the dots: Other solar systems Kuiper Belt in submm

Lawler 2014

Even though 20% of KBOs are in resonances, resonant structure is drowned out by ring Debris disks can tell us about migration history

Lawler (2014) NASA/HST KB “debris disk” is bounded by resonances, not planets. Is this a sign of migration? Is it common? We need to discover (diskcover?) more disk-planet systems. The Structure of the Kuiper Belt • Provides us with a chance to view detailed orbital structure of planetesimals (in other systems can only see dust) • Bewaaaaaare observational biases! • Biases *can* be characterized and accounted for in surveys • What type of migration happened in our Solar System? • What happens in other systems? • Need more disk-planet system discoveries • Exciting discoveries in distant Kuiper Belt are coming • LSST will ﬁnd THOUSANDS of new KBOs