Transcript Origin of the Solar System

Origin of the Solar System
Astronomy 311
Professor Lee Carkner
Lecture 8
What would be the easiest way to
increase the magnification of your
telescope?
a)
b)
c)
d)
e)
Increase the size of the primary mirror
Increase the size of the secondary mirror
Use an eyepiece with a longer focal length
Use an eyepiece with a shorter focal length
There is no way, the magnification of a
given telescope is fixed
Which of the following types of
electromagnetic radiation are best
studied from space?
a)
b)
c)
d)
e)
Ultraviolet
Radio
X-ray
a and c only
a, b, and c
Quiz 1 Monday
Covers lectures 1-8 and associated readings
About half multiple choice (~20 questions),
half short answer/problems (~4 questions)
Study:
Notes
Can you write a paragraph explaining each major
concept?
Exercises
Can you solve all the exercises with no resources?
Readings
Can you do all the homework with no book and
Quizdom questions with no notes?
Bring pencil and calculator!
No sharing!
The Solar System
Questions

When did it form?

Why does it have structure?
Structure of the Solar System
The solar system has three distinct regions
Inner Region
Mercury, Venus, Earth, Mars, Asteroids

Outer region
Jupiter, Saturn, Uranus, Neptune and Moons

Trans-Neptunian region
Kuiper Belt and Oort Cloud

Where Did the Solar System
Come From?

We can’t look back in time to see how
the Sun and planets formed, but we can
look at young stars that are forming
today
Star Formation
Stars are formed in clouds of gas and
dust when a clump of material starts to
contract

The mutual gravity of the particles in
the clump causes the contraction to
continue

Conservation of angular momentum
makes the clump spin faster
Rapid rotation causes the outer layers to form a
disk
Circumstellar Disks

We also can see them silhouetted
against a bright background in Hubble
images
Disks are common around young stars
From Disks to Planets
Many stars between 1-50 million years
old have disks, but stars slightly older
generally do not
Where does the disk go?

A disk has more surface area than a
group of planets with the same mass, so
it radiates more light

How Do Planets Form?
There are 4 stages to planet formation
1
2  grains stick together to form
planetesimals
3
4  gas and leftover planetesimals are
cleared from solar system
What Was the Solar Nebula
Made of?
Solar Nebula -From studying meteorites and star
forming regions we hope to discover
what the solar nebula was made of
Two basic components
Gas -Dust -- made of rock (silicates), metal
(iron) and ices (water, methane, ammonia,
carbon dioxide)
Solar System Dust Grain
Accretion of Grains
Dust grains are very small (< 1 mm), how do
they form planets?

If dust grains are fractal they may stick together
more easily

At the end of this stage the solar system is
populated by a few thousand planetesimals, such a
system is invisible to telescopes
Disk
Star
High Density
Low
Density
Larger Grains
move to center
Accretion in a Protoplanetary
Disk
Temperature and the Solar
Nebula
Two basic types of dust in solar nebula:
Volatiles -Refractory Material --
Temperatures were higher in the inner solar
system and lower in the outer solar system
Near the Sun the volatiles boiled off leaving
only the refractory material behind

Outer solar system -- icy planetesimals
Rocky
Icy
Gas
Temperature
Regions of Formation
Planetesimals to Planets
Due to gravity and intersecting orbits
the planetesimals collide with each
other

Planet formation happens differently in
inner and outer solar system
Formation of Gas Giants
In the outer solar system you have more
material (both volatiles and refractory
material), so planets are larger

No more hydrogen gas after a few million years
Thus, in the outer system where the
temperatures are lower you have gas giants
Formation of Terrestrial
Planets

Result is small rocky planets with no
large gassy outer layers
Accretion of the Inner Planets
Orbital Evolution

This causes:
Shifting of the orbits of the Gas Giants

Icy planetesimals ejected to form the
Kuiper Belt and Oort cloud
The Final Solar System
Our picture of planet formation is driven
by an attempt to explain our own solar
system and its three regions

Outer or Gas Giant region

We have also found other types of
planetary systems different from our own

Steps in Solar System Formation
1 Inner solar system -- volatiles boil off,
resulting in small rocky planets
2 Outer solar system -- large planet cores
form rapidly from refractory and icy
material, acquire large gas envelopes
3 Edge of solar system -- leftover and
ejected icy planetesimals form Kuiper
belt and Oort cloud