1 Stellar Astronomy Spring_2015 Day-18

Course Announcements Exam-2 – Fri. 3/6 Chapters 5 & (some of) 6  I will collect the L-T books at this time. Smartworks Chapters 5: Due Wed. 3/4 Smartworks Chapters 6: Due Mon. 3/16 APSU Research and Creativity Forum April 11-12, 2014 Abstracts are due: 4:30pm Fri., March 21 Mar. 2 – Last day to drop with an automatic “W” Apr. 2 – Last day to drop a class.

Solar Flare

Big and Hot objects have greater luminosity than small cool objects Luminosity is the total energy (light) emitted by an object in each second. Stefan-Boltzmann law Luminosity depends on an surface area (A), and its temperature (T4); Surface Area ∝ R2 Luminosity = 4π R2 T4 Big and Hot objects have greater luminosity than small cool objects

Lecture Tutorial Luminosity: (pg 55) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.

Hertzsprung-Russell Diagram 20,000 10,000 5,000 Luminosity (solar units) Temperature (K) 4 2 1 3 5 10,000 100 10 0.1 0.01 0.001 0.0001 1,000

Which star is Hot and Dim? 20,000 10,000 5,000 Luminosity (solar units) Temperature (K) 4 2 1 3 5 10,000 100 10 0.1 0.01 0.001 0.0001 1,000 Temperature (K)

Which star is Cool and Dim? 20,000 10,000 5,000 Luminosity (solar units) Temperature (K) 4 2 1 3 5 10,000 100 10 0.1 0.01 0.001 0.0001 1,000 Temperature (K)

Luminosity (solar units) Which star is Largest? 20,000 10,000 5,000 Luminosity (solar units) Temperature (K) 4 2 1 3 5 10,000 100 10 0.1 0.01 0.001 0.0001 1,000

Luminosity (solar units) Which star is smallest? 20,000 10,000 5,000 Luminosity (solar units) Temperature (K) 4 2 1 3 5 10,000 100 10 0.1 0.01 0.001 0.0001 1,000 Temperature (K)

Brightness is the amount of light arriving at a particular place. Decreases as the distance from a light source increases, obeying an inverse square law. The light spreads out over a greater area. Fig. 5.23 12

Lecture - Tutorial: Blackbody Radiation (pg. 59) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.

Energy Output per second Star A Star A Star A Star D Energy Output per second Star C Star B V I B G Y O R V I B G Y O R V I B G Y O R Wavelength

Which has the longer peak wavelength? Star C Wavelength V I B G Y O R Energy Output per second Star A Star A Star C Same

Which has the lower surface temperature? Star C Wavelength V I B G Y O R Energy Output per second Star A Star A Star C Same

Energy Output per second Which star looks red? Star A Star C Both Neither Star C Wavelength V I B G Y O R Energy Output per second Star A

Which has the greater energy output? Star C Wavelength V I B G Y O R Energy Output per second Star A Star A Star C Same

Energy Output per second Which star is larger? Star C Wavelength V I B G Y O R Energy Output per second Star A Star A Star C Same

Which star is larger? Star A Star D Same Star A Star D Wavelength V I B G Y O R Star A Energy Output per second

Energy Output per second Try to determine EVERYTHING about how these four stars compare!! Temp, Energy output, color, size (area)….. Object A Wavelength V I B G Y O R visible range Energy Output per second Object C Object B Object D