ASTR 1200 Announcements. Exam #1 in class, next Tuesday, October 7 Have posted review sheet and sample exam Help room: Mondays 3-5,Duane G2B90 Review Today Josh review/help session today after class?. Website http://casa.colorado.edu/~wcash/APS1200/APS1200.html. Structure of the Exam.
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Exam #1 in class, next Tuesday, October 7
Have posted review sheet and sample exam
Help room: Mondays 3-5,Duane G2B90
Josh review/help session today after class?
Calculators strongly recommended. (Check batteries!)
Pencils are a good idea for the calculations. (but not necessary)
Formulae and constants you need will be provided.
Just like the sample exam.
Will not be a test of time. Should be finished in under one hour. But will have full 75minutes to complete it.
Facts. Multiple Choice
Fast. Do these first.
How things work. Written Answers
Identify and use the formulas.
These take longer. Do them last.
Do additional exercises.
Go through each powerpoint slide and make certain you understand.
Background reading of for explanation of individual points.
Test yourself to identify weak areas using review sheet and sample exam.
Drakes Equation and prevalence of Life in the Universe
Sizes of things
Formation of Solar System
Position, velocity, acceleration
Structure of Sun
Our place in the galaxy
Light years and parsecs
Magnitudes and Absolute Magnitudes
Concept only from here on:
Electromagnetic Spectrum and its parts
The Spectral Sequence
a Cen B
Stars Differ By:
And composition doesn’t vary
Age and Mass only.
Those on main sequence are all
burning H so age drops out.
MS is function of MASS only!!!
As mass of
MS star increases,
both R and T
on any vertical
a Cen B
Spectral TypeNewly Formed Star
Then sits while
What determines amount of time a star stays on Main Sequence?
Just like a kerosene heater: Amount of fuel and rate of burn.
More Mass = More Fuel
More Luminosity = Greater Burn Rate
We can scale from the Sun: M = 1M L = 1L
Sun lasts 1010 years
M in solar masses
L in solar luminosities
Mass Luminosity Lifetime in Billion Years
Sun 1 1 10
Sirius 2 10 2
Prox Cen .4 .001 4000
Rigel 8 10,000 .008
Dinky little stars like Prox Cen will last trillions of years
Huge stars like Rigel are gone in a few million
There aren’t many large stars out there, because they don’t last.
10,000 O stars of the 100,000,000,000 Milky Way stars