Small Bodies of the Solar System

1
Small Bodies of the Solar System

• Pluto, Comets, Asteroids,
• Meteors and Zodiacal Light

2
PLUTOGod of the Underworld
3
Pluto Physical Data

• Discovered by Clyde W. Tombaugh in 1930
• Diameter 2294 km (0.18 Dearth)
• Mass 1.2x1025 g (0.002 Mearth)
• Density 1.84 g/cm3
• Rotation Period 6.39 days
• Tilt of Axis 96o (retrograde!)
• Surface Temperature 43 K (-382o F)

4
Pluto Physical Data

• Orbital Semi-Major Axis 39.44 AU
• Orbital Period 247.7 years
• Orbital Inclination 17.2o
• Orbital Eccentricity 0.250
• Surface Gravity 0.06 Earth gravity
• Satellites 1
• Magnetic Field unknown

5
The Discovery of Planet X

• Discovered Feb 8, 1930 by then 24-year old Clyde
  Tombaugh
• Its existence was predicted by Percival Lowell
  using the same techniques that Leverrier used to
  find Neptune

6
The Discovery of Planet X
January 23, 1930
January 29, 1930
The Plates on which Clyde Tombaugh found Pluto
7
Plutos Surface

• This image was taken by the Hubble Space
  Telescope and is the best surface map yet made
• Only contrasts are seen, no features
• Pluto has not yet been visited by spacecraft

8
Plutos Atmosphere

• Very thin atmosphere (when closest to Sun)
• Envelopes its moon too
• Mostly made of Nitrogen and Methane
• Atmosphere condenses and snows to the surface of
  Pluto and its moon when they are farther from the
  Sun

9
Plutos Moon

• CHARON
• Discovered by James Christy in 1978
• Saw a bump move from one side of Pluto to the
  other about every six days
• About half the size of Pluto, orbits retrograde

One of Christys images
10
Plutos Moon

• As seen by Hubble Space Telescope

Charon
Pluto
19,700 km
11
Plutos Strange Orbit

• Plutos Orbit is highly eccentric (0.250), highly
  inclined to the plane of the solar system
  (17.2o), and its orbit crosses Neptunes!
• Since Jan 23, 1979 and until March 15,1999 Pluto
  is closer to the Sun the Neptune!

12
Plutos Orgin

• Since Pluto and Charon are thought to have the
  same composition as Neptunes Triton, it is
  suggested that they might be escaped satellites
  of Neptune (dynamicists say no)
• Or Triton, Pluto and Charon all formed near
  Neptune and only Triton was captured

13
Asteroids
14
The Asteroid Belt

• Theory 1
• Material between Jupiter and Mars tried to form a
  planet when the Solar System was forming, but
  Jupiters gravitational influence wouldnt let it
  happen
• Theory 2
• A planet did form between Jupiter and Mars
  (Asteroidia), and some catastrophic event
  destroyed the planet, leaving the asteroids

15
The Discovery of Asteroids

• On the first day of the 19th C. (Jan 1,1801),
  Ceres (the largest known asteroid) was discovered
  by Giuseppe Piazzi
• By the end of the 19th C., several hundred were
  known
• We now know of more than 7000

16
Particular Asteroids

• CERES
• The largest asteroid by far
• Diameter 914 km
• Contains 25 of the mass of all the asteroids
  combined
• The next largest are Pallas, Vesta, and Hygiea
  which are between 400 and 525 km in diameter
• All other known asteroids are less than 340 km
  across

17
Particular Asteroids
IIDA and DACTYL

• Ida was encountered by the Galileo spacecraft in
  1993
• Ida was found to have a small satellite, Dactyl
• Dactyls size is 1.6 x 1.2 km, and orbits 90 km
  above Ida

18
Comets
Comet West
19
Comet Basics

• Comets are mostly (50) water ice
• Comets are referred to as dirty snowballs
• They are a mixture of water ice, frozen gases,
  and silicate materials
• Comets have very eccentric orbits
• They only have tails when close to the Sun
• The tails are made of gas and dust released by
  the comet.

20
Anatomy of a Comet

Ion Tail
Direction of Comets Motion
Coma
Nucleus
Hydrogen Cloud
Dust Tail
To Sun
21
History of Comets
m
22
Comet Halley

• Orbits Sun every 76 years
• Furthest point in its orbit is just beyond the
  orbit of Neptune
• Nucleus 15 x 8 x 8 km
• Rotates every 7.6 days

23
Recent Comets

• Comet Hyakutake in March of 1996

Image taken by J. De Buizer and J. Radomski of
the University of Florida Department of Astronomy
24
Recent Comets

• Comet Hale-Bopp in March 1997
• Image taken by J. DeBuizer and J.Radomski of
  the University of Florida Department of Astronomy

25
Meteors, Meteorites, and Meteor Showers
26
Meteor Nomenclature

• Meteoroids - interplanetary debris
• Meteor - Also called shooting star
• When a meteorite has entered the
• atmosphere creating a streak of
  light
• Meteorite - Those few meteoroids that make
• it to the Earths surface

27
Types of Meteorites
IRONS

• Mostly made of iron with about 9 nickel

STONES

• Primarily silicates similar to Earth rocks

STONY-IRONS

• Mixture of the above two types

28
Meteor Showers

• Associated with debris left behind by comets
• Typically very small meteoroids, so no meteorites
  are produced during a shower
• Can be as many as 100 meteors per hour in a good
  shower

29
Meteor Impacts

• One catastrophic meteor impact every 26 million
  years
• Might have been responsible for dinosaur
  extinction

Barringer crater in Arizona (1200 m in diameter,
200 m deep)
30
Zodiacal Light and Gegenschein

• Zodiacal light is due to dust, concentrated in
  the plane of the solar system, that reflects the
  light of the Sun towards our eyes
• Reflection from the dust also causes a patch of
  light directly opposite the Sun, called the
  gegenschein

Ecliptic
Zodiacal Light
Horizon
Sun