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Centaurs

  • Objects in orbits between Jupiter and Neptune.
  • Over 100 Centaurs known.
  • Orbits are unstable; will either collide with Jovian planets or be ejected from the solar system.
  • Likely sourced from the Kuiper belt.
  • Gravitational interactions by Neptune disrupt orbits.

Asteroids - Titius-Bode Law

  • Discovered by Johann Titius in 1766.
  • Relationship between planet distances from the Sun; series 0, 3, 6, 12, 24, 48, 96, 192 corresponds to planetary distances after adding 4.

Asteroids - First Sightings

  • Ceres discovered on January 1, 1801, by Guiseppe Piazzi.
  • Additional objects discovered later: Pallas, Vesta, Juno.

Asteroids - Orbits

  • Over 300,000 known asteroids today.
  • Main asteroid belt located between Mars and Jupiter.
  • Near-Earth asteroids (red dots) and Trojan asteroids share Jupiter's orbit.
  • NASA Lucy mission to visit 6 Trojan asteroids and 2 main belt asteroids.

Asteroids - Gaps

  • "Kirkwood Gaps"; regions with few asteroids due to orbital resonances with Jupiter.

Asteroids - Composition

  • Ceres as a dwarf planet and asteroid; largest in the asteroid belt.
  • Asteroids are primarily rocky; Centaurs and Kuiper belt objects are icy.

Dawn Mission

  • Launched in 2007; studied Vesta (arrived July 2011) and Ceres (arrived February 2015).
  • Vesta has a differentiated structure; includes the Rheasilvia crater.
  • Ceres has a weak atmosphere and signs of cryovolcanism.

Asteroid Families

  • Groups of similarly composed asteroids thought to arise from collisional events.
  • Vesta family is an example of a surviving parent asteroid.

NEAR Shoemaker Mission

  • Targeted the near-Earth asteroid Eros.
  • Eros’s dimensions: approximately 33km long, 13km wide; has numerous craters.

Near-Earth Asteroids

  • Notable for their proximity to Earth; at least one 50m object passes between Earth and Moon weekly.
  • Many in unstable orbits; potential for collision with Earth.
  • Not currently known of any certain impacts in the next 100 years.

Notable Near-Earth Asteroids

  • Itokawa studied by JAXA's Hayabusa mission; revealed water and minerals.
  • Ryugu and Bennu visited by Hayabusa2 and OSIRIS-Rex missions, respectively; both returned samples.