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.
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.
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
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
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)
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)
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)
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)
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)
10. Circumbinary Planets: the darlings of press & science fiction, and a beautiful testbed for the resilience of planet formation theories. Tatoo I Tatoo II
13. ASIDE FROM THAT, WHY CARE ABOUT A HANDFUL OF CIRCUMBINARY PLANETS?
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.
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)
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
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
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
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
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
21. THE MAIN BOTTLENECK: PLANETESIMAL GROWTH
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.
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.
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
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!