ASTR 1200 Announcements Website 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?

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 O Stars of Orion's Belt >30,000 K Lines of ionized helium, weak hydrogen lines <97 nm (ultraviolet)* BRigel 30,000 K- 10,000 K Lines of neutral helium, moderate hydrogen lines nm (ultraviolet)* ASirius 10,000 K-7,500 K Very strong hydrogen lines nm (violet)* FPolaris 7,500 K- 6,000 K Moderate hydrogen lines, moderate lines of ionized calcium nm (blue)* G Sun, Alpha Centauri A 6,000 K- 5,000 K Weak hydrogen lines, strong lines of ionized calcium nm (yellow) KArcturus 5,000 K- 3,500 K Lines of neutral and singly ionized metals, some molecules nm (red) M Betelgeuse, Proxima Centauri <3,500 K Molecular lines strong >830 nm (infrared) *All stars above 6,000 K look more or less white to the human eye because they emit plenty of radiation at all visible wavelengths.

The H-R Diagram Plot of Brightness vs Temperature O Spectral Type Brightness B M A F G K Sun Sirius  Cen B Prox Cen Procyon Rigel Capella Sirius B Main Sequence Giants White Dwarfs

The H-R Diagram

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 increasing size  AT 4 T constant on any vertical line As mass of MS star increases, both R and T increase

Newly Formed Star O Spectral Type M B M A F G K Sun Sirius  Cen B Prox Cen Procyon Rigel Capella Sirius B Main Sequence Giants White Dwarfs Protostar 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 years M in solar masses L in solar luminosities

Some Lifetimes MassLuminosityLifetime in Billion Years Sun1110 Sirius2102 Prox Cen Rigel810, 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