UT Austin Colloquium

Transcript

1. PLANET FORMATION IN
   BINARY SYSTEMS
   How robust is planet formation in
   disturbed environments?
   +
   Meschiari 2012a, 2012b, 2014
   Stefano Meschiari - UT Austin Colloquium September 9th, 2014
   ASTRONOMY EDUCATION & OUTREACH
   Engaging students, teachers & the
   general public through interactive
   astronomy apps.
   

   View Slide

2. PLANET FORMATION IN
   BINARY SYSTEMS
   How robust is planet formation in
   disturbed environments?
   +
   Meschiari 2012a, 2012b, 2014
   Stefano Meschiari - UT Austin Colloquium September 9th, 2014
   ASTRONOMY EDUCATION & OUTREACH
   Engaging students, teachers & the
   general public through interactive
   astronomy apps.
   

   View Slide

3. OUTLINE
   1. Pathways to planet formation in a highly disturbed environment
   Observed census of planets in
   binary systems
   What physics determines the initial
   conditions for planet formation?
   Migration of planets vs. migration
   of solids
   

   View Slide

4. OUTLINE
   1. Pathways to planet formation in a highly disturbed environment
   Observed census of planets in
   binary systems
   What physics determines the initial
   conditions for planet formation?
   Migration of planets vs. migration
   of solids
   2. Outreach, Education & Fun
   Science
   Enabling education, outreach and citizen
   science through scientific code
   

   View Slide

5. OUTLINE
   1. Pathways to planet formation in a highly disturbed environment
   Observed census of planets in
   binary systems
   What physics determines the initial
   conditions for planet formation?
   Migration of planets vs. migration
   of solids
   2. Outreach, Education & Fun
   Science
   Enabling education, outreach and citizen
   science through scientific code
   3. What is the size distribution
   of solids in PPDs?
   A new Monte-Carlo code for collisional evolution of dust
   & planetesimals (if there’s enough time!)
   Bouncing
   barrier
   Fragm
   entation
   region
   Slow
   Fast
   
   (streaming instability)
   

   View Slide

6. PART 1 Why is planet formation so complicated,
   yet so commonplace and resilient?
   commonplace
   to 0-th order, virtually 

   every star
   is a planet host
   complicated
   bridge from μm-sized dust to Jupiter-sized
   planets, jumping through several hurdles with
   poorly understood physics
   (see PPVI, Johansen et al., 

   Testi et al., 2014)
   

   View Slide

7. PART 1 Why is planet formation so complicated,
   yet so commonplace and resilient?
   commonplace
   to 0-th order, virtually 

   every star
   is a planet host
   complicated
   bridge from μm-sized dust to Jupiter-sized
   planets, jumping through several hurdles with
   poorly understood physics
   (see PPVI, Johansen et al., 

   Testi et al., 2014)
   

   View Slide

8. PART 1 Why is planet formation so complicated,
   yet so commonplace and resilient?
   commonplace
   to 0-th order, virtually 

   every star
   is a planet host
   complicated
   bridge from μm-sized dust to Jupiter-sized
   planets, jumping through several hurdles with
   poorly understood physics
   (see PPVI, Johansen et al., 

   Testi et al., 2014)
   

   View Slide

9. PART 1 Why is planet formation so complicated,
   yet so commonplace and resilient?
   commonplace
   to 0-th order, virtually 

   every star
   is a planet host
   complicated
   bridge from μm-sized dust to Jupiter-sized
   planets, jumping through several hurdles with
   poorly understood physics
   (see PPVI, Johansen et al., 

   Testi et al., 2014)
   

   View Slide

10. Circumbinary Planets:
    the darlings of press & science fiction,
    and a beautiful testbed for the
    resilience of planet formation theories.
    Tatoo I
    Tatoo II
    

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13. ASIDE FROM THAT, WHY CARE ABOUT A HANDFUL
    OF CIRCUMBINARY PLANETS?
    

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14. ASIDE FROM THAT, WHY CARE ABOUT A HANDFUL
    OF CIRCUMBINARY PLANETS?
    Circumbinary planets are unique testbeds for planet formation paradigms.
    The few planets found by Kepler are located in extremely dynamically
    harsh regions, which adversely affects some of the more delicate formation
    stages.
    

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15. ASIDE FROM THAT, WHY CARE ABOUT A HANDFUL
    OF CIRCUMBINARY PLANETS?
    Circumbinary planets are unique testbeds for planet formation paradigms.
    The few planets found by Kepler are located in extremely dynamically
    harsh regions, which adversely affects some of the more delicate formation
    stages.
    Kepler 16-b
    Kepler 34-b
    Kepler 38-b
    Kepler 47-b
    PH-1
    Observed circumbinary planets
    (orbits normalized to the instability region)
    Planet-Hunters 1/Kepler 64
    (no orbits are stable here)
    

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16. 1 Neptune mass
    OBSERVED CIRCUMBINARY PLANETS
    Kepler-34
    Kepler-35
    Kepler-38
    Kepler-47 b
    Kepler-47 c
    Planet Hunters-1 / Kepler-64
    1 Jupiter mass
    1 Saturn mass
    1 2 3 4 5
    0.01 0.05 0.50 5.00
    Semi-major axis, normalized to critical radius
    Mass (Jupiter masses)
    Ncb ~ 10-47% of all Kepler eclipsing binaries
    Ease of transit detection
    distance
    Kepler-413 b (2014)
    Kepler-16
    KIC 9632895 (2014)
    Unstable orbits
    

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17. 1 Neptune mass
    OBSERVED CIRCUMBINARY PLANETS
    Kepler-34
    Kepler-35
    Kepler-38
    Kepler-47 b
    Kepler-47 c
    Planet Hunters-1 / Kepler-64
    1 Jupiter mass
    1 Saturn mass
    1 2 3 4 5
    0.01 0.05 0.50 5.00
    Semi-major axis, normalized to critical radius
    Mass (Jupiter masses)
    Ncb ~ 10-47% of all Kepler eclipsing binaries
    Ease of transit detection
    distance
    Kepler-413 b (2014)
    Kepler-16
    KIC 9632895 (2014)
    Unstable orbits
    

    View Slide

18. Circumstellar/circumbinary disks
    Truncated, possible bimodal distribution in mass.
    Disk lifetimes may be quite a bit shorter?
    Artymowicz et al., 1991
    Takakuwa et al. 2012
    Not influenced by binarity inside (outside) the
    dynamically stable region (a ≶ 5-10 aB). If circumbinary,
    migration might stop and rebound from the inner hole.
    Core formation/migration
    Guedes et al., 2008
    Semi-major axis
    Pierens et al., 2007
    Dust coagulation, Planetesimal formation
    Disk is hotter and dynamically excited; grains are vaporized? Not
    clear from observations
    Nelson, 2000
    Planetesimal accretion
    Gravitational perturbations from the binary companion
    stirs and excites the eccentricity of the planetesimals
    Kraus et al., 2012
    Meschiari, 2012
    

    View Slide

19. Circumstellar/circumbinary disks
    Truncated, possible bimodal distribution in mass.
    Disk lifetimes may be quite a bit shorter?
    Artymowicz et al., 1991
    Takakuwa et al. 2012
    Not influenced by binarity inside (outside) the
    dynamically stable region (a ≶ 5-10 aB). If circumbinary,
    migration might stop and rebound from the inner hole.
    Core formation/migration
    Guedes et al., 2008
    Semi-major axis
    Pierens et al., 2007
    Dust coagulation, Planetesimal formation
    Disk is hotter and dynamically excited; grains are vaporized? Not
    clear from observations
    Nelson, 2000
    Planetesimal accretion
    Gravitational perturbations from the binary companion
    stirs and excites the eccentricity of the planetesimals
    Kraus et al., 2012
    Meschiari, 2012
    

    View Slide

20. Circumstellar/circumbinary disks
    Truncated, possible bimodal distribution in mass.
    Disk lifetimes may be quite a bit shorter?
    Artymowicz et al., 1991
    Takakuwa et al. 2012
    Not influenced by binarity inside (outside) the
    dynamically stable region (a ≶ 5-10 aB). If circumbinary,
    migration might stop and rebound from the inner hole.
    Core formation/migration
    Guedes et al., 2008
    Semi-major axis
    Pierens et al., 2007
    Dust coagulation, Planetesimal formation
    Disk is hotter and dynamically excited; grains are vaporized? Not
    clear from observations
    Nelson, 2000
    Planetesimal accretion
    Gravitational perturbations from the binary companion
    stirs and excites the eccentricity of the planetesimals
    Kraus et al., 2012
    Meschiari, 2012
    

    View Slide

21. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
    

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22. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
    Runaway accretion Shattering
    1 km < 1 m/s > 10 m/s
    10 km < 10 m/s > 100 m/s
    Keplerian speed at 1
    AU
    VKep ≈ 29,000 m/s ΔV ∼ e VKep
    • The crux of the problem:
    whether planetesimal growth
    can proceed is largely
    dependent on the encounter
    velocity.
    

    View Slide

23. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
    Low impact speeds,
    dynamically cold
    Single stars
    Runaway accretion Shattering
    1 km < 1 m/s > 10 m/s
    10 km < 10 m/s > 100 m/s
    Keplerian speed at 1
    AU
    VKep ≈ 29,000 m/s ΔV ∼ e VKep
    • The crux of the problem:
    whether planetesimal growth
    can proceed is largely
    dependent on the encounter
    velocity.
    

    View Slide

24. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
    Low impact speeds,
    dynamically cold
    Single stars
    Runaway accretion Shattering
    1 km < 1 m/s > 10 m/s
    10 km < 10 m/s > 100 m/s
    Keplerian speed at 1
    AU
    VKep ≈ 29,000 m/s ΔV ∼ e VKep
    • The crux of the problem:
    whether planetesimal growth
    can proceed is largely
    dependent on the encounter
    velocity.
    Around a binary
    large eccentricity, weak
    aligment
    

    View Slide

25. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
    Low impact speeds,
    dynamically cold
    Single stars
    Runaway accretion Shattering
    1 km < 1 m/s > 10 m/s
    10 km < 10 m/s > 100 m/s
    Keplerian speed at 1
    AU
    VKep ≈ 29,000 m/s ΔV ∼ e VKep
    • The crux of the problem:
    whether planetesimal growth
    can proceed is largely
    dependent on the encounter
    velocity.
    Around a binary
    large eccentricity, weak
    aligment
    Within a circumbinary gas disk
    Eccentricity and phasing are size-
    dependent: velocities can be high
    enough to be destructive!
    

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