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Astronomy 340 Fall 2007

Explore the origins and properties of Kuiper Belt Objects (KBOs) in the outer solar system, including colors, orbital populations, and dynamic history. Learn about classical vs. scattered KBOs, orbital properties, and Neptune migration effects.

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Astronomy 340 Fall 2007

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  1. Astronomy 340Fall 2007 18 October 2007 Class #14

  2. Midterm Review Sheet • MIDTERM  OCT 25 in class • No notes, books, friends • You will get an equation and constants sheet • Blue books or paper? • Format: 2-3 somewhat quantitative questions, 2-3 qualitative questions • Exam will be based on lecture notes, book reading, HW assignments • There are a few hints in the review sheet

  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. 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

  18. But are they really planets?

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