130 likes | 243 Views
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.
E N D
ASTR 1200Announcements 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 Closed book. 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.
How to Study Knowledge Facts. Multiple Choice Fast. Do these first. Conceptual How things work. Written Answers Calculations Identify and use the formulas. These take longer. Do them last. Homeworks Redo them. Do additional exercises. Lecture Notes Go through each powerpoint slide and make certain you understand. Textbook Background reading of for explanation of individual points. Test yourself to identify weak areas using review sheet and sample exam.
Material Covered Drakes Equation and prevalence of Life in the Universe Scientific Notation Sizes of things Formation of Solar System Position, velocity, acceleration Newton’s Laws Orbits Escape Velocity Surface Gravity Orbital Period Structure of Sun Nuclear Processes Solar Activity
Material Covered Our place in the galaxy Light years and parsecs Parallax Proper Motion Brightness Magnitudes and Absolute Magnitudes Concept only from here on: Electromagnetic Spectrum and its parts Spectroscopy Spectral Types
The Spectral Types Table 15.1 The Spectral Sequence
The H-R DiagramPlot of Brightness vs Temperature -5 Giants Rigel Capella 0 Sirius Brightness Procyon Sun Main Sequence +5 a Cen B White Dwarfs +10 Sirius B Prox Cen +15 K M F G A B O Spectral Type
The Main Sequence Stars Differ By: Mass Age Composition Nothing else! 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!!!
Full, Artistic H-R As mass of MS star increases, both R and T increase increasing size sAT4 T constant on any vertical line
-5 Giants Rigel Capella 0 Sirius Protostar Procyon M Sun Main Sequence +5 a Cen B White Dwarfs +10 Sirius B Prox Cen +15 K M F G A B O Spectral Type Newly Formed Star Large, Low T. Settles down to MS Then sits while burning H
MS Lifetime 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
Some Lifetimes 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