welcome to astronomy! introduction to the universe astro 1105/1107 prof. julia kregenow
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Welcome to
Astronomy!
Introduction tothe
Universe
Astro 1105/1107Prof. Julia Kregenow
A large, glowing ball of gas that generates heat and light through nuclear fusion
Star
GalaxyA great island of stars in space, all held
together by gravity and orbiting a common center
M31, The Great Galaxy in Andromeda
Universe
The sum total of all matter and energy; that is, everything within and between
all galaxies
Your Goals: Brief Survey
What do you want to learn about astronomy?
Write down a few things.
My Goals: on Syllabus
On course website: www.astro.cornell.edu/academics/courses/astro105/
Please read it carefully!
Homework for TOMORROW
• Read Syllabus online -- quiz tomorrow!– The syllabus is our CONTRACT
• Register on “MasteringAstronomy” website – Instructions on our course webpage www.astro.cornell.edu/academics/courses/astro105/
– Enroll in our course: (ID# given on syllabus)
• First online assignment due tomorrow 10:30am– “Introduction to MasteringAstronomy” (see HW page)
SOME REALLY BIG IDEAS
ScienceLight
Lookback timeGravity
Star stuffExpanding universe
Space is big. And empty.
Chapter 1Our Place in the
Universe
How did we come to be?
Pg. 4
The Universe is Dynamic
Everything is moving
Some terminology:
Expansion
Revolve vs. Rotate
What motion does the Earth undergo?
What motion does the Sun undergo?
There are over 100,000,000,000 stars in our galaxy.
??
Thought QuestionSuppose you tried to count the more than 100 billion stars in our galaxy,
at a rate of one per second…
How long would it take you?
Unit Conversion
Convert 100 Billion seconds to years
Seconds -> Minutes -> Hours -> Days -> Years
Lookback Time
• We see objects as they were in the past:
• Light travels at a finite speed (300,000 km/s).
• The farther away we look in distance, the further back we look in time.
• Allows us to study the history of the Universe.
Example: Our nearest neighbor.
This photo shows the Andromeda Galaxy as it looked about 2 1/2 million years ago.
Question: When will be able to see what it looks like now?
M31, The Great Galaxy in Andromeda
Fig. 1.4
Light-year: the distance light travels in one
year.
(But how far is that?)
• Scientific Notation
• Multiply and Divide powers of 10
• Convert Units
• Rearrange an equation to solve for another variable
• Plug numbers in for variables in an equation and calculate
Math Skills Summary
• Scientific Notation– e.g. 300,000,000 = ?– e.g. 4x10-5 = ?
• Multiply and Divide powers of 10– e.g. 108 / 10-5 = ?
• Convert Units– e.g. How many inches in a mile?
• Rearrange an equation to solve for another variable– e.g. b = L / 4d2. Solve for d.
• Plug numbers in for variables in an equation and calculate– e.g. L = 3.8x1026 watts, d = 1.5x1011 m, b = ?
Math Skills Summary
(show coolpics.ppt)