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AST3021 Lecture 01

Lecture 1. AST3021. Accretion disks. AST3021 Lecture 01. Huge accretion disks (AGNs). Accretion disk + Black Hole in the core of elliptical galaxy NGC 4261 (Hubble Space Telescope).

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AST3021 Lecture 01

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  1. Lecture 1. AST3021 Accretion disks AST3021 Lecture 01

  2. Huge accretion disks(AGNs)

  3. Accretion disk + Black Hole in the core of elliptical galaxy NGC 4261 (Hubble Space Telescope) A disk of cold gas and dust fuels a black hole (BH). 300 light-years across, the disk is tipped by 60 deg, to provide a clear view of the bright inner disk. The dark, dusty disk represents a cold outer region which extends inwards to an ultra-hot accretion disk with a few AU from the BH. This disk feeds matter into the BH, where gravity compresses and heats the material. Hot gas rushes from the vicinity of the BH creating the radio jets. The jets are aligned perpendicular to the disk. This provides strong circumstantial evidence for the existence of BH "central engine" in NGC 4261.

  4. ARTIST’S VIEW... BH radius (Schwarzschild radius) R = 2GM/c^2 = 3 km (M/M_sun) e.g., 10 M_sun ==> 30 km(binaries) 3e6 M_sun ==> 3/50 AU (galaxies) 1e8 M_sun ==> 2 AU (AGNs) 1e9 M_sun ==> 20 AU (quasars)

  5. Large disk luminosities L ~ 1e46 erg/s for quasars = = 1e34 erg/s (Sun) * 1e12 Grav.energy release in disk: L_dsk = 50% * GM/R * dM/dt R ~ 2GM/c^2 L ~ 25% * d(M c^2)/dt

  6. Small (circumstellar) disks Spectroscopic tomography of Cataclismic Variables cf. Keith Horne et al.

  7. Accretion disks are often found in close, interacting pairs of stars, such as the cataclysmic variables (CVs). One star, originally more massive, evolves to a compact companion: a white dwarf or perhaps a neutron star (pulsar) or a black hole. The other, originally less massive, star bloats toward the end of its main-sequence life and fills the critical surface called ROCHE LOBE, after which it sends a stream of gas onto a compact companion, creating an accrition disk

  8. Superhumps are distortions (local maxima) of the light curve of the s-called dwarf novae systems, belonging to cataclysmic variables class. The light curve is due to the varying viewing angle of the accretion disk and companion. Superhumps are due to resonances and waves in the disk.

  9. PPM simulation (Piecewise Parabolic Method) VH-1 code Owen, Blondin et al.

  10. z Gas density Smaller disks

  11. Oph Giant Molecular Cloud, 160 pc away contains numerous dark clouds

  12. Dark clouds L57 Barnard 68

  13. From: Diogenes Laertius,  (3rd cn. A.D.), IX.31 The first description of an accretion disk? “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 separatelike to like.” Leucippus, ca. 460 B.C.?

  14. Kant-Laplace nebula ~ primitive solar nebula ~ accretion disk ~ protoplanetary disk ~ T Tauri disk R. Descartes (1595-1650) - vortices of matter -> planets I. Kant (1755) - nebular hypothesis (recently revived by: Cameron et al, Boss) P.S. de Laplace (1796) - version with rings

  15. ALL STARS form in/via such disks! Planets are just a by-product. These protostellar disks are usually seen with mass of gas and dust ~ 0.01 to 0.1 solar masses. They are ~solar- composition. Grain agglomeration is ongoing.

  16. Matthew Bate (2003), Bate and Benz (2003) SPH, 1.5M particles simulation of gravitational collapse of a turbulent gas cloud (Jeans unstable) the cloud forms a stellar cluster including free- floating brown dwarfs and protoplanetary disks.

  17. Flaring shape jets Outflows disappear before the disks do

  18. Observed dM/dt ~ 1e-6 M_sun/yr for ~0.1 Myr time ==> total amount accreted ~0.1 M_sun Observed dM/dt ~ 1e-7 M_sun/yr for ~Myr time ==> total amount accreted ~0.1 M_sun etc.

  19. The smallest disks Planetary rings are also accretion disks, sort of. They are special: their thickness is extremely small: z/r = 10 m/ 66000 km ~ 1e-6, which makes them rather slowly accreting disks.

  20. The sub-compact intro to planetary systems and their evolution

  21. <1 Myr 5 Myr 20 Myr 200 Myr 4567 Myr

  22. T Tauri protostellar protoplanetary Transitional disks beta Pic- type disks Debris disks Zodiacal light now

  23. Giant planets form Disk cleared Debris disks evolve Terrestrials ready Zodiacal Light disk left

  24. -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.

  25. 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

  26. Marcy and Butler (2003)

  27. Like us? NOT REALLY WHY?

  28. Accretion disk theory

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