“Beyond the solar system where no man has gone before.”

Characteristics of Stars A great deal is known about our universe. Stars and “empty” space radiate energy in all directions. Learning about star characteristics and the universe is dependent on interpreting the radiated energy. Star Color and Temperature

Star Color and Temperature Yellow Blue RED 2,500 6,000 30,000 K Cool stars Hot stars Long wavelengths Short wavelengths R O Y G B I V

I the stars. How is the color of a star related to Discuss with a friend: How is the color of a star related to the temperature of the star? 2. How EM waves related to the temperature of the star? I will get an A on my exams and quizzes.

Light Year How far is far? – Astronomical distances Interstellar space is measured using the light year. Light Year the distance that light travels in one year light travels 186,000 mi/sec (WOW!) Light travels 6 trillion miles in one year. One would have to travel the speed of light for one year to go 6 trillion miles. Nothing in the universe is faster than light... except students when a class has just ended.

How far is far? – distance across a galaxy 100,000 light years across 6 trillion miles X 100,000

Measuring the Brightness of a Star Stellar Brightness Magnitude – the brightness of a star Magnitude is measured using (-) and (+) numbers the more (-) the number, the brighter the more (+), the dimmer the star Apparent Magnitude A star’s brightness as it appears from earth factors controlling apparent magnitude how big the star how hot the star how far away the star Which is brighter: -5 star or 5 star ?

Absolute Magnitude Example: -26.7 +5 32.6 ly measures the “actual” brightness Two stars with the same absolute magnitude will not be the same apparent magnitude. WHY? compare absolute brightness Use a standard distance of 32.6 light years away from earth. Example: Apparent Magnitude Absolute Magnitude -26.7 +5 bright dim Earth 32.6 ly

So, rank stars from biggest to smallest. Distance, Apparent Magnitude, and Absolute Magnitude of Some Stars 32.6 ly View from Earth Star Name Distance Light Years Apparent Magnitude Absolute Magnitude Sun NA -26.7 5.0 4.27 Alpha Centauri 0.0 4.4 Sirius 8.70 -1.4 1.5 -0.1 Arcturus 36 -0.3 Betelgeuse 520 .08 -5.5 1.3 -6.9 Deneb 1600 So, rank stars from biggest to smallest.

The brighter, the bigger the star Brightness scale – Using Absolute Magnitude Deneb Betelgeuse Arcturus Sirius Centauri Sun -7 -5 -3 -1 1 3 5 7 9 Bright Dim The brighter, the bigger the star

I the stars. 3. Describe the difference between Discuss with a friend: 3. Describe the difference between absolute and apparent magnitude. 4. How is a light year defined? 5. How fast does light travel? I will get an A on my exams and quizzes.

Super Giants and Red Giants How are stars classified? – The Hertzsprung-Russell Diagram (HR-diagram) -10 Very Bright -5 Super Giants and Red Giants Absolute Magnitude Main Sequence +5 +10 White Dwarfs Very Dim +20 20,000 14,000 10,000 7,000 5,000 3,000 Surface Temperature (K)

HR-Diagram O B A F G K M Cool, bright Hot, dim Spectral Class The Hotter, the Brighter The Cooler, the Dimmer Hot, dim 20,000 14,000 10,000 7000 5000 3000 Surface Temperature (K)

Oh, Be A Fine Guy (or Gal), Kiss Me Spectral Class Divisions O B A F G K M Oh, Be A Fine Guy (or Gal), Kiss Me Hottest Coolest Sub-divisions O0O1O2O3…O9 B0B1B2B3…B9A0……… What spectral class is our sun? G2 (5,5050 C, 9,9410 F) G2

I the stars. 6. What is the HR-diagram? 7. How is the HR-diagram used to classify stars? 8. How is the spectral class used to 9. What are specific differences between main sequence, red giants, and white dwarf type stars?

HR-Diagram Stellar Evolution Surface Temperature (K) Variable Star Stage Red Giant Stage Dust and gasses Protostar Planetary Nebula Stage Main Sequence Star Black Hole Stage White Dwarf 20,000 14,000 10,000 7,000 5,000 3,000 Surface Temperature (K)

Are we running out of gas? As you can see, the sun begins as a nebula, spends much of its life as a main sequence star, becomes a red giant, planetary nebula, white dwarf, and finally a black hole and dies. So, what phase is our sun? Are we running out of gas?

Final Exam according to Syllabus Each student gets Final Exam –Option-1 Final Exam according to Syllabus Each student gets there own set of three questions Final Exam – Option-2 May 9, 2012- Wednesday-MS2 8:00 am – 9:50 am 50% on Exams 1 & 2 50% on: The Atmosphere Global Winds The Solar System Beyond the solar system NO ESSAY QUESTION