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Lecture L12 ASTC25

Lecture L12 ASTC25. 1. Radiation pressure in action 2. Structures in dusty disks vs. possible reasons including planets 3. Dust avalanches, gas, and the classification of disks 4. Non-axisymmetric features without planets (dust avalanches) * * * 5. Pulsar planets

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Lecture L12 ASTC25

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  1. Lecture L12 ASTC25 1. Radiation pressure in action 2. Structures in dusty disks vs. possible reasons including planets 3. Dust avalanches, gas, and the classification of disks 4. Non-axisymmetric features without planets (dust avalanches) * * * 5. Pulsar planets 6. Radial velocity surveys: ~500 systems w/700 known planets 7. Transiting planets: ~200 planetary systems & 230 planets 8. Clues about the origin of the exoplanets 9. Implications for the solar system origin

  2. Summary of the various effects of radiation pressure of starlight on dust grains in disks: alpha particles = stable, orbiting particles on circular & elliptic orbits beta meteoroids = particles on hyperbolic orbits, escaping due to a large radiation pressure

  3. Radiation pressure coefficient (radiation pressure/gravity force) of an Mg-rich pyroxene mineral, as a function of grain radius s. s

  4. Above a certain beta value, a newly created dust particle, released on a circular orbit of its large parent body (beta=0) will escape to infinity along the parabolic orbit. What is the value of beta guaranteeing escape? It’s 0.5 (see problem 1 from set #5). We call the physical radius of the particle that has this critical beta parameter a blow-out radius of grains. From the previous slide we see that in the beta Pictoris disk, the blow-out radius is equal ~2 micrometers. Observations of scattered light, independent of this reasoning show that, indeed, the smallest size of observed grains is s~2 microns. Particles larger but not much larger than this limit will stay in the disk on rather eccentric orbit.

  5. How radiation pressure induces large eccentricity: = Frad / Fgrav

  6. Weak/no PAH emission Neutral (grey) scattering from s> grains Repels ISM dust Disks = Nature, not nurture! Size spectrum of dust has lower cutoff Radiative blow-out of grains (-meteoroids, gamma meteoroids) Instabilities (in disks) Radiation pressure on dust grains in disks Dust avalanches Quasi-spiral structure Orbits of stable -meteoroids elliptical Dust migrates, forms axisymmetric rings, gaps (in disks with gas) Color effects Enhanced erosion; shortened dust lifetime Short disk lifetime Age paradox

  7. Structure formation in dusty disks

  8. The danger ofoverinterpretation of structure Are the PLANETS responsible for EVERYTHING we see? Are they in EVERY system? Or are they like the Ptolemy’s epicycles, added each time we need to explain a new observation?

  9. FEATURESin disks: (9 types) blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals￭ tails, extensions ￭ ORIGIN: (10 categories) ￭ instrumental artifacts, variable PSF, noise, deconvolution etc. ￭ background/foreground obj. ￭ planets (gravity) ￭ stellar companions, flybys ￭ dust migration in gas ￭ dust blowout, avalanches ￭ episodic release of dust ￭ ISM (interstellar wind) ￭ stellar UV, wind, magnetism ￭ collective effects (radiation in opaque media, selfgravity) (Most features additionally depend on the viewing angle)

  10. AB Aur : disk or no disk? Fukugawa et al. (2004) another “Pleiades”-type star no disk

  11. ? Source: P. Kalas

  12. Hubble Space Telescope/ NICMOS infrared camera

  13. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals￭ tails, extensions ￭ ORIGIN: ￭ planets (gravity)

  14. .

  15. Some models of structure in dusty disks rely on too limited a physics: ideally one needs to follow: full spatial distribution, velocity distribution, and size distribution of a collisional system subject to various external forces like radiation and gas drag -- that’s very tough to do! Resultant planet depends on all this. Beta = 0.01 (monodisp.)

  16. Dangers of fitting planets to individual frames/observations: Vega has 0, 1, or 2 blobs, depending on bandpass. What about its planets? Are they wavelength- dependent too!? 850 microns

  17. HD 141569A is a Herbig emission star >2 x solar mass, >10 x solar luminosity, Emission lines of H are double, because they come from a rotating inner gas disk. CO gas has also been found at r = 90 AU. Observations by Hubble Space Telescope (NICMOS near-IR camera). Age ~ 5 Myr, a transitional disk Gap-opening PLANET ? So far out?? R_gap ~350AU dR ~ 0.1 R_gap

  18. Outward migration of protoplanets to ~100AU or outward migration of dust to form rings and spirals may be required to explain the structure in transitional (5-10 Myr old) and older dust disks

  19. HD141569+BC in V band HD141569A deprojected HST/ACS Clampin et al.

  20. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals￭ tails, extensions ￭ ORIGIN: ￭ stellar companions, flybys

  21. Best model, Ardila et al (2005) involved a stellar fly-by & Beta = 4 H/r = 0.1 Mgas = 50 ME 5 MJ, e=0.6, a=100 AU planet HD 141569A

  22. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals￭ tails, extensions ￭ ORIGIN: ￭ dust migration in gas

  23. Planetary systems: stages of decreasing dustiness In the protoplanetary disks (tau) dust follows gas. Sharp features due to associated companions: stars, brown dwarfs and planets. 1 Myr These optically thin transitional disks (tau <1) must have some gas even if it's hard to detect. Warning: Dust starts to move w.r.t. gas! Look for outer rings, inner rings, gaps with or without planets. 5 Myr Pictoris 12-20 Myr These replenished dust disk are optically thin (tau<<1) and have very little gas. Sub-planetary & planetary bodies can be detected via spectroscopy, spatial distribution of dust, but do not normally expect sharp features. Extensive modeling including dust-dust collisions and radiation pressure needed

  24. v=vK vg Gas pressure force vg v Gas pressure force

  25. Migration: Type 0 • Dusty disks: structure from gas-dust coupling (Takeuchi & Artymowicz 2001) • theory will help determine gas distribution Predicted dust distribution: axisymmetric ring Gas disk tapers off here

  26. Weak/no PAH emission Neutral (grey) scattering from s> grains Repels ISM dust Disks = Nature, not nurture! Size spectrum of dust has lower cutoff Radiative blow-out of grains (-meteoroids, gamma meteoroids) Instabilities (in disks) Radiation pressure on dust grains in disks Dust avalanches Quasi-spiral structure Orbits of stable -meteoroids elliptical Dust migrates, forms axisymmetric rings, gaps (in disks with gas) Color effects Enhanced erosion; shortened dust lifetime Short disk lifetime Age paradox

  27. Dust avalanches and implications: -- upper limit on dustiness -- the division of disks into gas-rich, transitional and gas-poor

  28. FEATURES in disks: blobs, clumps ￭ streaks, feathers ￭ rings (axisymm) ￭ rings (off-centered) ￭ inner/outer edges ￭ disk gaps ￭ warps ￭ spirals, quasi-spirals￭ tails, extensions ￭ ORIGIN: ￭ dust blowout avalanches, ￭ episodic/local dust release

  29. Weak/no PAH emission Neutral (grey) scattering from s> grains Repels ISM dust Disks = Nature, not nurture! Size spectrum of dust has lower cutoff Radiative blow-out of grains (-meteoroids, gamma meteoroids) Instabilities (in disks) Radiation pressure on dust grains in disks Dust avalanches Quasi-spiral structure Orbits of stable -meteoroids elliptical Dust migrates, forms axisymmetric rings, gaps (in disks with gas) Limit on fir in gas-free disks Color effects Enhanced erosion; shortened dust lifetime Short disk lifetime Age paradox

  30. Dust Avalanche(Artymowicz 1997) Process powered by the energy of stellar radiation N ~ exp (optical thickness of the disk * <#debris/collision>) N = disk particle, alpha meteoroid ( < 0.5) = sub-blowout debris, beta meteoroid ( > 0.5)

  31. Ratio of the infrared luminosity (IR excess radiation from dust) to the stellar luminosity; it gives the percentage of stellar flux absorbed reemitted thermally the midplane optical thickness multiplication factor of debris in 1 collision (number of sub-blowout debris) Avalanche growth equation Solution of the avalanche growth equation The above example is relevant to HD141569A, a prototype transitional disk (with interesting quasi-spiral structure.) Conclusion: Transitional disks MUST CONTAIN GAS or face self-destruction. Beta Pic is almost the most dusty, gas-poor disk, possible.

  32. OK! Gas-free modeling leads to a paradox ==> gas required or episodic dust production Age paradox! fIR =fd disk dustiness

  33. Bimodal histogram of fractional IR luminosity fIR predicted by disk avalanche process

  34. source: Inseok Song (2004)

  35. ISO/ISOPHOT data on dustiness vs. timeDominik, Decin, Waters, Waelkens (2003) uncorrected ages corrected ages -1.8 ISOPHOT ages, dot size ~ quality of age ISOPHOT + IRAS fd of beta Pic

  36. transitional systems 5-10 Myr age

  37. Weak/no PAH emission Neutral (grey) scattering from s> grains Repels ISM dust Disks = Nature, not nurture! Size spectrum of dust has lower cutoff Radiative blow-out of grains (-meteoroids, gamma meteoroids) Instabilities (in disks) Radiation pressure on dust grains in disks Dust avalanches Quasi-spiral structure Orbits of stable -meteoroids are elliptical Dust migrates, forms axisymmetric rings, gaps (in disks with gas) Limit on fIR in gas-free disks Color effects Enhanced erosion; shortened dust lifetime Short disk lifetime Age paradox

  38. Grigorieva, Artymowicz and Thebault (A&A 2006) Comprehensive model of dusty debris disk (3D) with full treatment of collisions and particle dynamics. ￭ especially suitable to denser transitional disks supporting dust avalanches ￭ detailed treatment of grain-grain colisions, depending on material ￭ detailed treatment of radiation pressure and optics, depending on material ￭ localized dust injection (e.g., planetesimal collision) ￭ dust grains of similar properties and orbits grouped in “superparticles” ￭ physics: radiation pressure, gas drag, collisions Results: ￭ beta Pictoris avalanches multiply debris x(3-5) ￭ spiral shape of the avalanche - a robust outcome ￭ strong dependence on material properties and certain other model assumptions

  39. Model of (simplified) collisional avalanche with substantial gas drag, corresponding to 10 Earth masses of gas in disk

  40. Main results of modeling of collisional avalanches: 1. Strongly nonaxisymmetric, growing patterns 2. Substantial exponential multiplication 3. Morphology depends on the amount and distribution of gas, in particular on the presence of an outer initial disk edge

  41. FEATURESin disks:(9 types) blobs, clumps ￭(5) streaks, feathers ￭(4) rings (axisymm) ￭(2) rings (off-centered) ￭(7) inner/outer edges ￭(5) disk gaps ￭(4) warps ￭(7) spirals, quasi-spirals￭(8) tails, extensions ￭(6) ORIGIN: (10 reasons) ￭ instrumental artifacts, variable PSF, noise, deconvolution etc. ￭ background/foreground obj. ￭ planets (gravity) ￭ stellar companions, flybys ￭ dust migration in gas ￭ dust blowout, avalanches ￭ episodic release of dust ￭ ISM (interstellar wind) ￭ stellar wind, magnetism ￭ collective eff. (self-gravity) Many (~50) possible connections !

  42. From: Diogenes Laertius,  (3rd cn. A.D.), IX.31 “The worlds come into being as follows: many bodies of all sorts and shapes move from the infinite into a great void; theycome togetherthere and produce asingle whirl, in which,collidingwith one another andrevolvingin all manner of ways, they begin to separate like to like.” Leucippus (Solar nebula of Kant & Laplace A.D. 1755-1776? Accretion disk?) “There are innumerable worlds which differ in size. In some worlds there is no Sun and Moon, in others they are larger than in our world, and in others more numerous. (...) in some parts they are arising, in others failing. They are destroyed by collision with one another. There are some worlds devoid of living creatures or plants or any moisture.” Democritus (Planets predicted: around pulsars, binary stars, close to stars ?) There are infinite worlds both like and unlike this world of ours.For the atoms being infinite in number (...) there nowhere exists an obstacle to the infinite number od worlds. Epicurus (341-270 B.C.)

  43. Pulsar planets: PSR 1257+12 B 2 Earth-mass planets and one Moon-sizes one found around a millisecond pulsar First extrasolar planets discovered by Alex Wolszczan [pronounced volsh-chan]in 1991, announced 1992 Name: PSR 1257+12 A PSR 1257+12 B PSR 1257+12 C M.sin 0.020 ± 0.002 ME 4.3 ± 0.2 ME 3.9 ± 0.2 ME Semi-major axis: 0.19 AU 0.36 AU 0.46 AU P(days): 25.262±0.003, 66.5419± 0.0001, 98.2114±0.0002 Eccentricity: 0.0 0.0186 ± 0.0002 0.0252 ± 0.0002 Omega (deg): 0.0 250.4 ± 6 108.3 ± 5 The pulsar timing is so exact, observers now suspect having detected a comet!

  44. Radial-velocity planets around normal stars

  45. -450: Extrasolar systems predicted (Leukippos, Demokritos). Formation in disks -325 Disproved by Aristoteles 1983: First dusty disks in exoplanetary systems discovered by IRAS 1992: First exoplanets found around a millisecond pulsar (Wolszczan & Dale) 1995: Radial Velocity Planets were found around normal, nearby stars, via the Doppler spectroscopy of the host starlight, starting with Mayor & Queloz, continuing wth Marcy & Butler, et al.

  46. Orbital radii + masses of the extrasolar planets (picture from 2003) Radial migration Hot jupiters These planets were found via Doppler spectroscopy of the host’s starlight. Precision of measurement: ~3 m/s

  47. Example of transit discoveries WASP 10b planet - Jupiter class

  48. Masset and Papaloizou (2000); Peale, Lee (2002) Some pairs of exoplanets may be caught in a 2:1 or other mean-motion resonance

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