Download Outline Ch.6 Solar System

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Quiz for Ch. 6 has been posted and is due
next Mon. night (as usual)
Outline Ch.6 Solar System
(Different from Book’s outline)
I.
Overall Properties of Solar System
and its Formation
II. Extrasolar Planets
Outline Ch.6: Solar System
(Different from Book’s outline)
I.
Overall Properties of Solar System:
1.
2.
3.
4.



Nearly co-planar orbits (disk-shaped)
All planets orbit Sun in same direction as Sun’s
rotation
MOST (but not all) planets rotate in same
direction as their obits around Sun
Planets:
Small dense terrestrial planets in inner SS
Large, low density, Jovian planets in outer SS
Pluto is exception
(Cont.)
Outline Ch.6 (Cont.)
I.
Overall Properties (cont):
5.
6.
7.
In general: closer to Sun, larger density
Hot near Sun cold far away
Composition of Solar Nebula
The planets are tiny compared to the distances between them (a
million times smaller than shown here), but they
exhibit clear patterns of composition and motion.
The patterns are more important than numbers, names, and other
details
What have we learned?
• What does the solar
system look like?
 Our solar system
consists of the Sun,
nine eight planets
-----and their moons, and
vast numbers of
asteroids and
comets. Each world
has its own unique
character, but there
are many clear
patterns among the
worlds.
Clues to the Formation
of Our Solar Sytem
Our Goals for Learning
• What features of our solar system provide
clues to how it formed?
• What theory best explains the features of
our solar system?
What have we learned?
• What features of our solar system provide clues to how it
formed?
 Four major features provide clues:
(1) Planets all orbit the Sun in same direction as Sun’s
rotation (counterclockwise when seen from North), most
planets rotate in same direction as their orbit.
(2) The major planets divide clearly into two groups: terrestrial
and jovian (Jupiter-like).
(3) The solar system contains large numbers of asteroids and
comets.
(4) There are some notable exceptions to these general
patterns.
What have we learned?
• What theory best explains the features of our
solar system?
 The nebular theory, which holds that the
solar system formed from the gravitational
collapse of a great cloud of gas.
Slowly rotating
interstellar cloud of
gas and dust collapses
to form the Solar
Nebula
Solar Nebula:
rotating, disk-shaped
cloud out of which
Sun and planets
formed
I. Overall Properties (cont):
7. Composition of Solar Nebula:
98% Hydrogen & Helium, 2% all other
elements
Condensation of solids from nebula:
 Inner part is hot, only high density
materials (metals and silicates) can
condense
 Outer regions cooler, can condense lower
density materials like water ice and other
ices
Condensation of Solids from Solar Nebula
(not exactly like the book)
Asteroids and
comets
accreted at
different
distances
from the Sun,
resulting in
different ice
contents
What have we learned?
• Where did the solar
system come from?
 The cloud of gas that
gave birth to our solar
system was the product
of recycling of gas
through many
generations of stars
within our galaxy. This
gas consisted of 98%
hydrogen and helium
and 2% everything else
combined.
What have we
learned?
• What caused the orderly
patterns of motion in our
solar system?
 A collapsing gas cloud naturally
tends to heat up, spin faster, and
flatten out as it shrinks in size.
Thus, our solar system began as
a spinning disk of gas. The
orderly motions we observe
today all came from the orderly
motion of this spinning disk of
gas.
Question 1
 What factors do you think might have
contributed to the difference between
Terrestrial and Jovian Planets:
a) Temperature (hotter near Sun and colder far from
Sun)
b) Size of Orbits (larger orbits can “sweep” more
material)
c) The composition of the Solar Nebula
Question 1
 What factors do you think might have
contributed to the difference between
Terrestrial and Jovian Planets:
a) Temperature (hotter near Sun and colder far from
Sun)
b) Size of Orbits (larger orbits can “sweep” more
material)
c) The composition of the Solar Nebula
d) All of the above
Question 2
 How did the composition of the Solar Nebula
affect the composition of the planets?
1. Metals and Silicates can condense at higher
temperatures than water and other gases
2. Hydrogen, helium, and oxygen were more
abundant than metals and silicates
3. The higher the mass a planet has, the larger the
atmosphere it can retain.
The correct answer is
A. 1 and 2
C. 3 only
B. 1 only
D. 1, 2 and 3
Question 2
 How did the composition of the Solar Nebula
affect the composition of the planets?
1. Metals and Silicates can condense at higher
temperatures than water and other gases
2. Hydrogen, helium, and oxygen were more
abundant than metals and silicates
3. The higher the mass a planet has, the larger the
atmosphere it can retain.
The correct answer is
A. 1 and 2
C. 3 only
B. 1 only
D. 1, 2 and 3
I. Overall Properties (cont):
7. Composition of Solar Nebula:
98% Hydrogen & Helium, 2% other elements
Condensation of solids from nebula:


Inner part is hot, only high density materials (metals and silicates)
can condense
Outer regions cooler, can condense lower density materials like
water ice and other ices
Near Sun: terrestrial planets
Far from: Sun Jovian planets
Question 3
 If I tell you a planet has many moons is it
likely to be
a)
b)
c)
d)
Terrestrial
Jovian
Pluto
an asteroid
What have we learned?
• Why are there two types of planets?
 Inner solar system: high temperatures, only metal
and rock could condense.
 Outer solar system: cold temperatures, more
abundant ices condense along with metal and rock.
What have we learned?
• How do we explain the
• Where did asteroids existence of our Moon and other
and comets come
“exceptions to the rules”?
from?
•Most of the exceptions
 Asteroids are the
probably arose from collisions
rocky leftover
or close encounters with
planetesimals of
leftover planetesimals,
the inner solar
especially during the heavy
system, and
comets are the icy bombardment that occurred
early in the solar system’s
leftover
history. Our Moon is probably
planetesimals of
the result of a giant impact
the outer solar
between a Mars-size
system.
planetesimal and the young
Earth.
What have we learned?
• When did the planets form?
 The planets began to accrete in the
solar nebula about 4.6 billion years
ago, a fact we determine from
radioactive dating of the oldest
meteorites.
6.5 Other Planetary Systems
Our Goals for Learning
• How do we detect planets around other
stars?
• What have other planetary systems taught
us about our own?
Outline Ch.6 (Cont.)
(Different from Book’s outline)
II. Extrasolar Planets
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Are there planets around other stars?
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Have we “seen” them?
Outline Ch.8 (Cont.)
II. Extrasolar Planets
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Are there planets around other stars?
YES, about 1000!
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Have we “seen” them?
Outline Ch.8 (Cont.)
II. Extrasolar Planets
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Are there planets around other stars?
YES about 1000!
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Have we “seen” them?
We have not seen most of them (not
directly), we have “seen” only a few so far
Outline Ch.8 (Cont.)
II. Extrasolar Planets
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About 1000 detected so far

We have not “seen” most of them yet, they
are detected indirectly using radial velocity
and transits in front of stars
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Types of planets: all strange (because
those are the only ones we can detect)
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No Earth-sized extraterrestrial planet yet
More than 1000 known
extrasolar planets as of
Feb. 2011
•Most are more massive
than Jupiter and closer to
their star than Earth is to
Sun
•Are revisions to the
nebular theory are
necessary? Some
•Planets can apparently
migrate inward from their
birthplaces.
Orbits of 3 planets around star Upsilon
Andromeda
Is Earth Unusual?
 Only 5 Earth-like
planets found so far
 Observations are
not good enough to
tell if they are
common or rare
 Available methods
can detect mainly
BIG planets so far.
What have we learned?
• How do we detect planets around other stars?
 We detect extrasolar planets primarily indirectly
by observing the planet’s effects on the star it
orbits.
 Most of the discoveries to date have been made
with the Doppler technique, in which Doppler
shifts reveal the gravitational tug of a planet (or
more than one planet) on a star.
 A a few planets have been observed to “transit” in
front of their star.
What have we learned?
• What have other planetary systems taught
us about our own?
 Planetary systems exhibit a surprising
range of layouts, suggesting that jovian
(Jupiter-like) planets sometimes
migrate inward from where they are
born. This lesson has taught us that
despite the successes of the nebular
theory, it should be refined.