Transcript A105 Stars and Galaxies

Welcome to A100
Solar System
Instructor: Caty Pilachowski
Assoc. Instructor: Nathalie Haurberg
Read Preview – Cosmic Landscape
1st Homework due Sept. 12
Today’s APOD
The Sun Today
Where will we start?
– The night sky
– Learning to see with an
astronomical eye
– Size and scale
Where are we going?
• The origin and evolution of planets
and the Solar System
• The Earth’s environment
• Planets around other stars
A100 - Solar System
On the back of note card…
 draw a dot in the center of the paper label it as the Sun
 draw and label the Earth’s orbit around
the Sun, as if you were looking down on the
Solar System from above
 add and label the orbits of as many other
planets and Solar System components as
you can
What’s in
the Solar
System?
• The Sun
• The planets and
moons
• Dwarf planets
(asteroids &
plutoids)
• Cometary bodies
• Meteoroids
• Dust
• Plasma (hot gas)
The
Sun
Radius: 700,000 km
Diameter: 1,400,000 km
(about 100 x the diameter of Earth)
Mass: 300,000 x mass of Earth
Of course, the
PLANETS
Earth
Radius: 6400 km
Distance from Sun: 150,000,000 km
1 AU, 8 light minutes
Moon
¼ Earth’s radius
distance ~400,000 km
Units of Distance
kilometers
for radii of the planets, the Sun, etc.
astronomical units
for distances between solar system bodies
definition: the average distance between the Earth
and Sun (~150,000,000 km = 1.5 x 108 km)
light years
for distances between stars and galaxies
definition: the distance light travels in one year
(~10,000,000,000,000 km = 1013 km = 63,000 AU)
What about
poor Pluto?
• What is a
planet?
• What
must be
considered
to decide
if Pluto is
a planet?
What
defines a
planet?
NOT TO SCALE!!!
Round (enough mass for strong gravity)
Dominant body (tosses smaller bodies
out of the Solar System)
Orbits the Sun
Pluto’s Basic Data
•
•
•
•
Diameter:
Mass
In SS plane?
Circular Orbit?
0.18 Earth diameters
0.002 Earth masses
NO! …orbit tilts 17º
NO! …e=0.25
Other planets
e < 0.2
Other planets < 7º
Guidance from the
Discovery of Ceres
Image from Hubble
• 1801
• Planet suspected between Mars and
Jupiter
• Campaign organized to search the sky
• Ceres - the first (and largest)
asteroid to be found
• A planet…. or not?
Ceres: Not!
• Too small
• Many more asteroids found
shortly thereafter
• Tens of thousands known today
Pallas
Juno
Hubble images
So What
Is Pluto?
One of many
dwarf planets
(plutoids) that
orbit the Sun
outside the orbit
of Neptune
The Outer Solar System
• Our Solar System is
surrounded by a halo
of ice bodies – plutoids
and cometary bodies
What
about that
plasma?
The Solar Wind:
• Energy is released in the form
of light, sub-atomic particles,
and magnetic fields
• The particles are protons,
electrons, and helium nuclei
moving out from the Sun at a
speed of about 500 km/sec
The
Solar
Wind
• The solar wind flows from the Sun and envelopes the
Earth and other planets
• The charged particles distort the Earth’s magnetic field
and produce geo-magnetic storms that disrupt the
Earth’s environment
The
Outer
Limits
Now in the distant solar system, NASA spacecraft
continue to characterize the outer solar system
environment and search for the heliopause
boundary, the outer limits of the Sun's magnetic
field and outward flow of the solar wind
http://vraptor.jpl.nasa.gov/voyager/voyager.html
The
Environment
of the
Solar
System
Outer limits of SS Oort Cloud
The Sun entered an interstellar cloud of mixed
plasma and gas about 103-105 years ago
 The directions of motion of the Sun and the cloud
suggest that our Solar System will be in this cloud for
the next million years
 The surrounding interstellar cloud will shrink the
heliosphere to a smaller radius
 The clouds are so thin that we see right through them

The “Local Bubble”
On a larger scale,
the Sun is
surrounded by a
large bubble of
low density gas,
on the edge of
one the Galaxy’s
spiral arms
Our Sector of the Galaxy
The Sun lies along one of
our Galaxy’s spiral arms,
known as the Orion Arm
View of the
Milky Way Galaxy
Our Milky Way galaxy
contains two hundred
billion stars
The Sun is about
26,000 light
years from the
center
Our Milky Way
Galaxy is part of
a small cluster of
about 3 dozen
galaxies
Our Local Group of
galaxies is part of a
larger Supercluster
of galaxy groups
Virgo
Supercluster
Galaxies and clusters
of galaxies collect
into vast streams,
sheets, and walls of
galaxies
Put these objects in the correct order from
the nearest to the farthest from Earth
a) The Sun, the Milky Way, Alpha
Centauri, Saturn, the Andromeda
Galaxy
b) The Sun, Alpha Centauri, Saturn, the
Andromeda Galaxy, the Milky Way
c) The Sun, Saturn, Alpha Centauri, the
Milky Way, the Andromeda Galaxy
d) Saturn, the Sun, Alpha Centauri, the
Milky Way, the Andromeda Galaxy
Overview
• Organization and
course goals
Who’s in the class?
• Freshmen? Sophomores?
Juniors? Seniors? Other?
• School…?
• Major…?
Science and the
Distribution Requirement
 Science and technology
drive much of modern life
 Jobs!
 Informed voters make
better decisions
Why are you
taking this
class?
Why are you taking this class?
• I need to take a science class and astronomy sounded
easy/fun
• I've always been interested in astronomy
• I had space in my schedule for another course and
thought I'd try astronomy
• I want to be a science teacher
• I'm thinking of minoring/majoring in astronomy
• My friend is taking the class, so I'm taking it with
her/him.
• This is supposed to be an easy course, and I need to
bring up my GPA
• This course was recommended by a friend
• I want to amaze my friends and family with my
knowledge of the night sky.
Course
Organization
Syllabus/Oncourse
Text + Web
Lecture Notes
Written Homework
Quizzes
Observing
Activities
Exams & Final
Office Hours
Caty P.: Thursday, 11-noon
SW 323 + by appointment
Nathalie
Haurberg: Mon. 2:30-3:30, SW313
+ Thurs. 5:30-6:30 PM
@ Starbucks on Indiana Ave
GRADES
 Quizzes (20%, best 8 of 10)
 Homework (20%, best 8 of 10)
 Observing Activities (10%, four
required)
 3 Exams (10% + 10% + 10%)
 Final Exam (20%)
Course Goals
 Science as discovery
 Use real astronomical
data
 Learn about the
process of science
View of Saturn’s Rings
from the Cassini
Spacecraft
One question I’ve always had
about astronomy is…
Kirkwood Observatory Open
TONIGHT
• Great time to see
Jupiter
• 9:30-11:30, weather
permitting
• Call hotline (8557736) to confirm
open
• West end of Dunn’s
Woods
www.astro.indiana.edu/kirk_sch.shtml
Dates
to
ASSIGNMENTS
Remember
this week
 Read “Cosmic Landscape”
 Quiz on essential facts and
scientific notation on Monday
 Rooftop Sky Viewing Sept. 10
 1st HW due Sept. 12