Download - Welcome to 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 Radius: 6400 kmDistance from Sun: 150,000,000 km
1 AU, 8 light minutes
MoonRadius: ¼ Earth’s radiusDistance from Earth:
384,000 km
TheSun
Radius: 700,000 kmDiameter: 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: 0.18 Earth
diameters• Mass 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
• 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?
Image from Hubble
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 theMilky 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.
Virgo Superclust
er
Our Local Group of galaxies is part of a larger Supercluster of galaxy groups.
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
ReadingLecture NotesWritten
AssignmentsProjectsQuizzesObserving
Office Hours
Caty P.: Thursday, 11-noonSW 315
Tara Angle: Tues. 11-noonWeds. 2-3 PMSW 313
GRADESQuizzes (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…
ASSIGNMENTSthis week
Read units 1, 2, 3, 4.1Essential Facts Worksheet
due Thursday1st News Quiz next Tues.