Asteroids (minor planets)

1
Asteroids (minor planets)

• Bodes Law suggests a planet between Mars and
  Jup. at 2.8 AU
• 1801 Piazzi (It.) discovers Ceres
• 1804 Juno disc.
• 1807 Vesta disc.
• (these are the largest asteroids)

• Now, many thousands are known to exist near 2.8
  AU, ranging in size from a few km up to 1000km
• Known as the Asteroid Belt

2
The Kirkwood Gaps and Resonances
3
Diversity of Asteroids
4
Asteroid Composition
C - carbonaceous P - dirty ice S - silicate D -
very dark ice M - metal
5
Spectra of Asteroids depends on composition
6
Ida and Dactyl Example of an asteroid with a
moon
7
Phobos, Moon of Mars Likely a captured asteroid
8
(No Transcript)
9
Asteroid Light Curves Effects of shape and
surface patchiness
SHAPE EFFECT
MATERIAL EFFECT
10
(No Transcript)
11
(No Transcript)
12
Share Question

• Holga and Hilda are 2 asteroids. They have the
  same size and shape and are at the same distance
  from Sun. Holga is icy with an albedo of 0.9.
  Hilda is rocky with and albedo of 0.1. Which is
  brighter in visible light?
• a) Holga
• b) Hilda
• c) Both same
• Which is brighter in infrared light?
• a) Holga
• b) Hilda
• c) Both same

13
Asteroid Groups

• Earth crossing
• Atens
• Apollos
• Mars crossing
• Amors
• Asteroid Belt
• Trojans - near Jupiter
• Centaurs
• Kuiper Belt

• Centaurs
• Temporary orbits at 20-50 AU, from Saturn to
  Neptune
• Kuipers
• Stable region
• Around 35,000 objects of size 100-300 km around
  Neptune and Pluto (30-50 AU)
• Belt extends to 400 AU
• A flattened belt!

14
(No Transcript)
15
Kuiper Belt Objects
Outer orbit is Pluto
16
(No Transcript)
17
(No Transcript)
18
Impacts
Evidence points to the idea that impacts
have significantly influenced planets and moons.
19
Tunguska Event

• Siberia, 1908
• June 30, 717 am
• Explosion of large meteorite at 6km altitude -
  deafening bangs and a fiery cloud
• With relevance to today, what should be the
  criteria for informing/warning/alarming the
  public of near collisions?
• How much should be invested toward defending
  planet Earth against impacts?

20
Tunguskan Destruction
21
End of the Dinosaurs
22
Asteroid Detected Hours Before Impact

• A routine search revealed a small asteroid
  hurtling toward Earth
• Rapid international observations predicted the
  objects impact 19 hours later over Sudan
• The fireball from the asteroid breaking up in the
  atmosphere was observed by passing aircraft,
  satellites and residents of Sudan
• This small impact tested NASA warning procedures
  developed for more ominous impact events

2008 TC3
Image of F class asteroid 2008 TC3 in the hours
before it impacted Earth. Exposure time was 6
minutes, so the asteroid appears as a streak.
Image from La Sagra Sky Survey, Spain.
23
Meteorites Found from Asteroid

• The small asteroid was expected to vaporize in
  the atmosphere but a joint NASA-Sudanese team
  undertook a search for fragments
• Surprisingly, 280 fresh-looking meteorites have
  been found spread along TC3s predicted ground
  track
• Analysis of the collected samples enabled
  scientists to determine the asteroids
  composition and type
• Meteorite composition and density suggest TC3 was
  ejected from the surface of a larger asteroid of
  rare type

A meteorite from 2008 TC3 is discovered in the
Nubian Desert of Sudan by staff and students of
the University of Khartoum.
24
Connecting Samples with Sources

• 2008 TC3 was the first asteroid observed from
  space to the ground
• For the first time, scientists can study
  meteorite samples knowing where the meteorites
  came from
• Global cooperation and increasingly widespread
  technology may make these fortuitous events more
  common

Clockwise from top left Telescope of the
Catalina Sky Survey where TC3 was discovered
Detection image of 2008 TC3 Cell-phone image of
luminous trails left in the atmosphere when TC3
disintegrated into dust TC3 meteorite in the
Nubian Desert of northern Sudan
25
(No Transcript)
26
Protecting the Earth, Informing People,
Preventing Panic
27
Destructive Potential