Announcements

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Announcements
Brooks Observatory tours (March 16 - 18)
730 - 830 p.m. extra credit Weather
permitting Will look at Saturn, Jupiter, Orion
Nebula Bring back your ticket with your name on
the back
Homework "Temperature and Formation of Our
Solar System" exercise in the tutorial workbook,
pages 57-58.  Read chapter 7.
Midterm 2 March 23
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Chapter 10

• Remnants of Rock and Ice

• Asteroids
• Meteorites
• Comets
• Pluto and its moon

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Remnants of the Solar Nebula
Small bodies remain virtually unchanged since
their formation 4.5 billion years ago They carry
history of the Solar system in their
compositions, locations, and numbers.
Asteroid means starlike, a rocky leftover Comet
means hair (Greek), an icy leftover Meteor a
thing in the air (falling star) Meteorite any
piece of rock than fell to the ground from the sky
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Finding Asteroids
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Asteroid Vesta
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Asteroid Eros
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Comet Halley
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Comet 1993a Mueller
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Comet Hale-Bopp
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Nucleus of Comet Borrelli
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Meteor
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Leonid Meteor Shower
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Asteroids
Undetectable to the naked eye (a.k.a. minor
planets) The first asteroid Ceres was discovered
by Piazzi in 1800 in an attempt to find the
missing planet between Mars and Jupiter Ceres
has a diameter of 500 km (half of Pluto) There
are more than 100,000 asteroids larger than 1 km
in diameter The asteroid belt lies between 2.2
and 3.3 A.U.
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Missing planet
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Origin and evolution of the Belt
The most likely reason for the belt existence is
orbital resonances
A resonance occurs if an objects orbital period
is a simple ratio of anothers object period
(1/2, 1/4,etc.) Asteroids with resonance periods
will be pushed out of their orbits by large
planets (e.g., Jupiter)
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Asteroid belt
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Evolution of the Belt
Early in the history of the Solar system, the
belt contained enough planetesimals to form a
planet.
Gravitational tugs from Jupiter created the
gaps. Some pieces of the unformed planet were
kicked out and either crashed into a planet or
left the system.
Two stable zones (11 resonance) along Jupiters
orbit host two families of asteroids (Trojans).
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Jupiters Trojan Asteroids
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Meteorites
Meteorites are pieces of rock falling from the
sky. Meteorites are real Seen as fireballs
(sometimes with sound) May cause damage, but
most fall into oceans
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Types of Meteorites
Primitive meteorites composed of a random mix of
flakes from the solar nebula. They contain pure
metals, which are bound in minerals on Earth
Processed meteorites parts of a larger
object. Younger than primitive ones. Some
resemble the Earths core, others are similar to
the Earths crust and mantle.
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Primitive Meteorites
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Processed Meteorites
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The Origin of Meteorites
Primitive meteorites may be either rocky or
carbon-rich These 2 types are formed at
different distances from the Sun
Processed meteorites can be removed from the
surface of a planet by an impact. There are
meteorites from Moon and Mars found on Earth.
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Comets
Comets contain information about the outer solar
system Most of them visit the inner part only
once, a few are regular guests
One of the most famous comets is Halleys
comet. It was discovered by Edmund Halley in
1682. Its orbital period is 76 years. The last
appearance in 1986.
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Comet Structure
Comets are basically dirty snowballs where ice
mixes with rocky dust. Their mean size is a few
kilometers across.
Comets change appearance when they approach the
Sun. The comet body is called nucleus. Sublimating
ices create coma. A tail pointing away from the
Sun appears. There are two tails plasma tail and
dust tail.
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Comet Orbits
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The Origin of Comets
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Comet Hale-Bopp
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Sun Grazing Comets
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Pluto
Pluto was discovered in 1930 by Claude Tombaugh.
Its radius is 1,195 km and mass is 0.0025 Earth
mass. Its orbital period is 248 years. It was
closer to the Sun than Neptune in 1979
1999. At aphelion it is 50 AU from the Sun. Its
moon Charon was discovered in 1978.
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Pluto and Charon
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Plutos Orbit
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Pluto and Charon
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Charon, Plutos Moon
Pluto has a bump that moved from side to side
with a period of 6.4 days The discovery of
Charon enabled astronomers to determine Plutos
mass (Keplers 3rd law).
Plutos rotation axis is tipped 118o relative to
its orbit ? it rotates backwards relative to most
of other planets (except Venus and Uranus)
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Charon
Diameter more than half Plutos. Mass 1/8 the
mass of Pluto. Average distance from Pluto
20,000 km.
Charon could have formed by a giant
impact. Charon is visible from only one side of
Pluto. It neither rise nor set in Plutos skies.
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Cosmic Collisions
Meteor showers result of the Earths passing
through a comet orbit Meteors are single pieces
of comet dust 25 million meteors enter Earths
atmosphere every day Meteor showers get their
names after constellations from which they appear
to radiate
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Large Impacts
The larger the impactor, the more rare the impact
Meteor crater in Arizona formed 50,000 years
ago. A large impact occurred 65 million years
ago perhaps caused the dinosaur extinction. In
1908, an unusual explosion occurred in Siberia.
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Meteor Crater in Arizona
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Tunguska Meteorite
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Tunguska Meteorite
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Summary
Asteroids and comets are the best evidence of how
the solar system formed The small bodies are
significantly affected by planets
gravity. Impacts with comets and meteorites are
spectacular events, but may even alter
life. Pluto has more similarities with the
Kuiper belt comets.