Please find your nametag near the door and sit with a partner Good Morning! Please find your nametag near the door and sit with a partner

How Do We Classify Stars?

Pre-Evaluation Put your name on the worksheet. Answer as many questions as you can. When you are finished, raise your hand so I can collect the paper. You have 5 minutes to complete the work. http://www.timeanddate.com/timer/

How are Stars Born? http://www.youtube.com/watch?v=9EnBBIx6XkM

Properties of Stars

Properties of Stars Size Temperature (color) Apparent magnitude (brightness) Luminosity (absolute brightness)

HR Diagram http://www.timeanddate.com/timer/

Temperature Measured in kelvins (1 K = --456° F) Red Supergiants: 4940° F Blue Giants: 53540° F A very hot, orange fire is just 2000° F in comparison! The temperature of stars are often determined by the color of the stars, not the other way around! Colors tell us energy, which we can relate to temperature

Luminosity How much energy a star releases over a certain amount of time Tells us the “absolute magnitude”—how bright stars REALLY are If all the stars are the same distance away, how bright would they appear? The fact that luminosity depends on time is very important. Not only is luminosity the energy given off by a star, it’s the energy given off by a star over a certain amount of time.

Size Diameter measured in kilometers Largest star is the red hypergiant VY Canis Majoris 1,800 times larger than the sun Diameter: 1,975,000,000 km

Apparent Magnitude How bright stars appear to be from earth Actual brightness of stars gets distorted because of distance Closer stars look brighter than they actually are, farther stars look dimmer than they actually are

Colors of Stars Determined by temperature

Absolute Magnitude v. Luminosity

Post-Evaluation http://www.timeanddate.com/timer/ Please put your name on the paper and answer the questions to the best of your ability. You are to work alone. When you have finished please raise your hand and I will come collect your paper. Please remain seated and quiet, even if the bell rings, until I have dismissed you.

Thank you for being a great class!