Ch 11 Jennifer Blazejack

Introduction
11.1: Properties of Stars
11.2:  Patterns Among Stars
Conclusion
Introduction
We took the daily quiz at the beginning of class. There were two books presented this week on geology and hurricanes. A slide show was presented on the term paper currently being written and that our term paper is to be five pages. It is due at the end of semester along with the powerpoint on our term paper's subject.
11.1 Properties of Stars
The brightness of a star depends on its distance and how much light it emits. Apparent brightness is the amount of power (energy per second) reaching us per unit area. In the magnitude system refers to this term as apparent magnitude. Luminosityis the total amount of power that a star emits into space. In the magnitude system refers to this term as absolute magnitude.
Apparent brightness has a formula:

apparent brightness   =     luminosity

                                         2 

Luminosity is measured in watts per square. Luminosity can be found by using distance. 
There are two laws called inverse square law and inverse square law for light. We are the measure of everything so we are 1 AU within the circle on page 310. The farther you get out the dimmer the light appears. 
An important term to remember is stellar parallax. Stellar parallax is the small annual shift in a star's apparent position which is caused by the Earth's motion around the Sun. Imagine taking a photo of a friend in front of trees and mountains in the distance. As you move to the right, you are moving faster than your friend-but the trees and mountains are also moving. Parallax angle is the precise amount of a star's annul shift due to parallax. The more distant a star is the smaller parallax angle it will have. 
Temperatures are scaled in a special type graph. It measures hottest to coolest, with O being the hottest and M being the coolest. Remember: "O Be A Fine Girl/Guy, Kiss Me!". Our Sun is in the G special type because it is yellow in wavelength and is in the middle of the temperature ranges. 
Many stars are part of star binary systems. There are three types: visual binary, eclipsing binary, and spectroscopic binary.Visual binary is a pair of stars that we can see with a telescope, eclipsing binary is a pair of stars that orbit in the plane of our line of sight, and spectroscopic binary is how we observe Doppler shifts in its spectral lines (planets). Jupiter is hot enough to move stars.
The Hertzsprung-Russell Diagram is graphed by luminosity (size of the star) and temperature (color of the star). The bigger the size of a star is, the faster it will disappear. Red stars are the coolest while blue stars are the hottest. The graph contains the following:  
main sequence: hydrogen is turned into helium in it's core.
supergiants: are large and very bright
giants: are smaller in radius and lower in luminosity; it has lower temperatures but higher luminosity compared to dwarfs
white dwarfs: are small in radius and appear white because of the high temperatures it has; it has higher temperatures and lower luminosity 
Our Sun is a main sequence star. It's expected lifetime is 10 billion years. Hydrogen fusion determines a star's luminosity- the greater the luminosity the shorter life it will have (because it will run out of hydrogen sooner).
Conclusion
Answered thought questions on the H-R Diagram by determining luminosity, mass, and lifetimes. Briefly discussed 11.3 at the end of class.