29 november 2007 class #25 astronomy 340 fall 2007
TRANSCRIPT
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- 29 NOVEMBER 2007 CLASS #25 Astronomy 340 Fall 2007
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- Review Pluto system Odd orbit, 3 moons Possible collision? Triton Neptunes large moon Retrograde orbit likely gravitationally captured
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- A Little History Gerard Kuiper and Kenneth Edgeworth predicted a distribution of small bodies in the outer solar system 1940s Real surveys began in early 90s 70,000 KBOs w/ d > 100 km (estimated) 30 AU < a < 50 AU Range of inclination/eccentricity 1 st KBO is really Pluto!
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- Bernstein et al 2004
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- Properties of TNOs Green stars scattered population Red squares classical KBOs Lines are different power law fits Surface density best fit by two power laws
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- Basic Orbital Properties Classical Low eccentricity, low inclination 40 AU < a < 47 AU Resonant Occupying various resonances with Neptune 3:2, 4:3, 2:1 etc a ~ 40 AU Scattered High eccentricity, high inclination
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- Distribution of TNOs
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- Population Total mass ~ 0.5 Earth masses Total number unknown > 1500 detected via surveys Colors (Tegler et al 2003 ApJ 599 L49) ~100 KBOs with photometry classical KBOs are red (B-R > 1.5) scattered KBOs are grey Largely colorless (flat spectrum) Primordial?
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- Classical KBOs Mostly between 42 and 48 AU Formed via quiet accretion
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- Orbital Populations Reflect dynamical history of the outer solar system Hahn & Malhotra (2005 AJ 130 2392) N-body simulation Neptune migration previously heated disk Populates the 5:2 resonance with Neptune scattered KBOs largely affected by planet migration
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- Orbital Populations Hahn & Mulhatra
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- Scattered KBOs - orbits Trujillo, Jewitt, Luu 2000 ApJ 529 L103
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- Populations (Hahn & Malhotra 2005)
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- Explanation for Colors? Neptune migrates from 25 AU to 40 AU Scatters objects Objects at 40 AU are relatively unperturbed surfaces reflect methane ice
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- KBO colors
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- KBO Colors vs Dynamics
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- Centaurs (Horner, Evans, Bailey 2004) Eccentricity e = 0.2-0.6 Perihelia 4 < q < 6.6 AU 6.6 < q < 12.0 AU 12.0 < q < 22.5 AU Aphelia 6.6 60 AU Mean diameters ~ few hundred km
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- Centaurs Dynamical Evolution Dynamical lifetimes Orbital decay rate N = N 0 e -t ( = 0.693/T 1/2 ) T 1/2 ~ 2-3 Myr scattered via interaction with giant planets No correlation with color
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- Centaurs Dynamical Evolution Dynamical lifetimes Orbital decay rate N = N 0 e -t ( = 0.693/T 1/2 ) T 1/2 ~ 2-3 Myr scattered via interaction with giant planets No correlation with color Origin? scattered TNOs scattered inward Hahn & Mulhatra
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- Sedna
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- How do you measure the diameter? Best fit orbit R = 90.32 AU a = 480 AU e = 0.84 i = 11.927 Perihelion ~ 76 AU in 2075
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- Sedna
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- Quaoar
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- Quaor spectroscopy (Jewitt & Luu) Looks a bit like water ice
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- 2003 UB313 16 years worth of data Orbital properties a = 67.9 AU, e = 0.4378, i = 43.99 Aphelion at 97.5 AU, perihelion at 38.2 AU (2257)
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- But are they really planets?
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- Eris - Spectroscopy Big circles = broadband colors Broad absorption = solid methane Approximate diameter = Plutos Hey, the thing has a moon.
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- Moons, moons everywhere.