Transcript A105 Stars and Galaxies

Welcome to A105
Stars and Galaxies
Instructor: Caty Pilachowski
Assoc. Instructor: Tara Angle
Today’s
APOD
Read units 1, 2, 3, 4.1
Essential Facts Worksheet
due Thursday
Earth
Moon
Radius: 6400 km
Distance from Sun: 150,000,000 km
1 AU, 8 light minutes
Radius: ¼ Earth’s radius
Distance from Earth:
384,000 km
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
Is Pluto
a Planet?
o What is a
planet?
o What must be
considered to
decide if Pluto
is a planet?
Pluto – Basic Data
• Diameter:
• Mass
0.18 Earth diameters
0.002 Earth masses
• Inclination
17 degrees
(other planets 7 degrees or less)
• Eccentricity
0.25
(other planets less than 0.2)
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
What
defines a
planet?
o Round (enough mass for strong gravity)
o Dominant body (tosses smaller bodies
out of the Solar System)
o Orbits the Sun
First News Quiz
• In Class QUIZ - Sept. 5
• Astronomy Magazine article on Pluto:
www.astronomy.com/asy/default.aspx?c=a&id=4474
Use the “News Quiz” link on
Oncourse to find the article
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.
Where will we start?
– The night sky
– Learning to see with
an astronomical eye
– Size and scale
Where are we going?
• Modern Astrophysics
– A little physics
– Tools
– Understanding the Universe
The
Nearest
Stars
The closest star to our Sun is Proxima
Centauri, about 4 light years distant.
Most of the stars
we see in the sky
are within 250
light years
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.
The Visible
Universe
On the largest
scales, the
universe seems
to be more or
less uniform
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
Course
Organization
Syllabus/Oncourse
Text
Assigned Reading
Lecture Notes
Written
Assignments
Projects
Quizzes
Observing
Office Hours
Caty P.:
Thursday, 11-noon
SW 315
Tara Angle:
Tues. 11-noon
Weds. 2-3 PM
SW 313
GRADES
Quizzes (100 pts)
Homework Assignments (100 pts)
Observing Activities (100 pts)
Project (100 pts)
Exams (2 x 200 pts)
Final Exam (200 pts)
Course Goals
 Science as discovery
 Use real astronomical
data
 Learn about the process
of science
Nova GK Per, known as the
“Firework Nebula” exploded in
1901. The star lies 1500 light
years away, in the direction of
the constellation Perseus.
One question I’ve always had
about astronomy is…
ASSIGNMENTS
this week
Read units 1, 2, 3, 4.1
Essential Facts Worksheet
due Thursday
1st News Quiz next Tues.