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Exploring Pluto's Unique System and the Trans-Neptunian Objects

This review examines the peculiarities of the Pluto system, considering its odd orbit and three moons, along with the potential for future collisions in the broader context of the outer solar system. We delve into the dynamics of trans-Neptunian objects (TNOs), including the classifications of classical and scattered KBOs, influenced by Neptune’s migration. The research highlights the discoveries surrounding the populations of TNOs, their color distributions, and implications for the origins of these distant icy bodies.

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Exploring Pluto's Unique System and the Trans-Neptunian Objects

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  1. Astronomy 340Fall 2007 29 November 2007 Class #25

  2. Review • Pluto system • Odd orbit, 3 moons • Possible collision? • Triton • Neptune’s large moon • Retrograde orbit  likely gravitationally captured

  3. 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 • 1st KBO is really Pluto!

  4. Bernstein et al 2004

  5. 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

  6. 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

  7. Distribution of TNOs

  8. 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?

  9. Classical KBOs Mostly between 42 and 48 AU Formed via “quiet accretion”

  10. 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

  11. Orbital Populations Hahn & Mulhatra

  12. Scattered KBOs - orbits Trujillo, Jewitt, Luu 2000 ApJ 529 L103

  13. Populations (Hahn & Malhotra 2005)

  14. Explanation for Colors? Neptune migrates from 25 AU to 40 AU Scatters objects Objects at 40 AU are relatively unperturbed  surfaces reflect methane ice

  15. KBO colors

  16. KBO Colors vs Dynamics

  17. 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

  18. Centaurs – Dynamical Evolution • Dynamical lifetimes • Orbital decay rate  N = N0 e-λt (λ = 0.693/T1/2) • T1/2 ~ 2-3 Myr  scattered via interaction with giant planets • No correlation with color

  19. Centaurs – Dynamical Evolution • Dynamical lifetimes • Orbital decay rate  N = N0 e-λt (λ = 0.693/T1/2) • T1/2 ~ 2-3 Myr  scattered via interaction with giant planets • No correlation with color • Origin? • “scattered” TNOs  scattered inward Hahn & Mulhatra

  20. Sedna

  21. Sedna • 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

  22. Sedna

  23. Quaoar

  24. Quaoar

  25. Quaor spectroscopy (Jewitt & Luu) Looks a bit like water ice

  26. 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)

  27. But are they really planets?

  28. Eris - Spectroscopy • Big circles = broadband colors • Broad absorption = solid methane • Approximate diameter = Pluto’s • Hey, the thing has a moon….

  29. Moons, moons everywhere….

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