Solar System Debris

1
Solar System Debris

• Asteroids, KBOs, and Comets

2
Asteroids and Meteoroids

• Rocky material
• Asteroids gt100m
• Meteoroids lt100m
• Varying densities
• C-type (carbonaceous) about 15
• Contain a large fraction of carbon in their
  makeup
• S-type about 75
• Contain a large fraction of silicate rock
• M-type about 10
• Contain large fractions of nickel and iron

3
Orbital Properties of Asteroids

• Most are found in the Asteroid Belt
• Between 2.1 and 3.3 AU (midway between Mars and
  Jupiter)
• Eccentric elliptical orbits
• More than 200,000 known
• Origin disputed
• Is it the remains of a destroyed planet?
• Probably not not massive enough (less than the
  Moon)
• Is it made of rocks that never accreted to form a
  planet?
• Probably this would be due to Jupiters
  influence

4
(No Transcript)
5
Typical Asteroids

• The largest asteroids are Ceres (940km), Pallas
  (580km), and Vesta (540km)
• All three were at one time classified as planets
• Only two dozen or so are larger than 200km
• Some larger asteroids have their own moons
• Some asteroids are quite solid, while others are
  more like loosely bound rubble

6
(No Transcript)
7
Ida
Dactyl
8
Asteroid Exploration Observation

• Galileo (early 1990s)
• Flew through twice on its way to Jupiter
• NEAR (1997)
• Near Earth Asteroid Rendezvous
• Visited C-type asteroid Mathilde and S-type Eros
• Orbited Eros for a year, then landed on it in 2001

9
Eros
10
Earth-Crossing Asteroids

• A few asteroids have orbits eccentric enough to
  intersect Earths orbit
• Termed Apollo asteroids
• Influenced by the gravity of Mars and/or Jupiter
• Possibly collided with other asteroids
• More than 4400 are known
• More than 800 are classified as potentially
  hazardous, meaning they are larger than 150m
  across
• In June 2002 a 100-m asteroid passed within
  120,000km, but was only detected 3-days later
• In 2029 a 350m asteroid will pass just 23,000 km
  above the surface
• Earth gets hit on average 3 times every million
  years or so

11
Manicouagan Reservoir Quebec, Canada
12
(No Transcript)
13
Trojan Asteroids

• Do not orbit in the Asteroid Belt
• Co-orbital with Jupiter
• Lagrangian Points
• 60 in front (L4)
• 60 behind (L5)
• Clusters of asteroids that are gravitationally
  bound by both the Sun and Jupiter
• Venus, Earth, and Mars also have a small of
  trojan asteroids

14
(No Transcript)
15
The Kuiper Belt

• Kuiper Belt Objects (KBOs)
• Beyond the orbit of Neptune (30-50 AU)
• Estimated to be more than 100,000 objects larger
  than 100km
• Hundreds of times more massive than the Asteroid
  Belt (but still less than Earth)
• Rocky/Icy bodies much like most of the moons in
  the outer solar system

16
(No Transcript)
17
Pluto

• The most well-studied KBO
• Discovered in 1930 by Clyde Tombaugh
• Eccentric orbit (29.7 49.3 AU)
• Sometimes within Neptunes orbit
• Because of resonance the two will never collide
• Orbit inclined 17 degrees to the ecliptic
• About the size of Triton
• 1/500 the mass of Earth

18
(No Transcript)
19
Pluto

• Has at least one moon
• Charon
• A little over half the size of Pluto
• Little is known about Pluto or Charon
• Will be studied in detail in 2015 by NASAs New
  Horizons spacecraft

20
(No Transcript)
21
Comets

• Large chunks of icy rock in highly elliptical
  orbits around the Sun
• Short-period comets (periods less than 200 years)
  originate in the Kuiper Belt
• A KBO gets perturbed by neighboring objects or by
  the gravitational influences of the gas giants
• Long-period comets originate in the Oort Cloud
• Oort cloud ranges from 1000 100,000 AU in
  diameter
• Completely surrounds the solar system

22
(No Transcript)
23
Comet Structure

• Nucleus
• The main body of the comet, usually only a few km
  in diameter
• Coma
• As the nucleus approaches the sun, much of the
  icy material sublimes and creates a diffuse halo
  of dust and evaporated gas
• Can be nearly as large as Jupiter or Saturn
• Tail
• Two types Ion tails (made of ionized gas) and
  Dust tails (made of dust)
• Always points away from the Sun due to the solar
  wind
• Dust tails are often curved
• Can be nearly 1 AU long

24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Meteors

• A bright streak of light caused by friction
  between the meteoroid and the atmosphere
• Shooting stars
• Usually a few are visible per hour each night
• If the meteoroid survives and hits the ground, it
  is called a meteorite
• Most are bodies that have strayed from the
  Asteroid Belt
• Others are pieces of the Moon, Mars, or other
  bodies that were blasted off by impacts long ago

30
(No Transcript)
31
Meteor Showers

• Each time a comet passes near the Sun, it
  vaporizes more
• Eventually it breaks up and the small bits
  (called a meteoroid swarm) disperse along the
  orbit
• If Earth passes through the swarm, a meteor
  shower results
• Sometimes up to 500 meteors per hour
• Occurs at the same time each year
• Named for the radiant (the constellation from
  which they appear)

32
(No Transcript)
33
(No Transcript)
34
(No Transcript)