What this Mini-Lesson Will Cover: 1. How do you interpret the HR Diagram? 2. Where does a star’s energy come from? 3. What are the physical properties of our Sun?

Day 1: What Are Stars? A star is a large celestial body that is composed of hot gas and that emits light; the sun is a typical star The Sun, our closest star, is 93 million miles from Earth. The next closest star is 4.3 lighter years away. By mass, the Sun is 71 % Hydrogen, 27% helium and the rest heavier element. This is similar to the composition of the universe. The Sun is about 4.6 billion years old.

Day 1: Sun’s Energy The Sun, like all stars, are driven by nuclear fusion reactions. The core of a star is extremely hot, extremely dense, and under extreme pressure. Nuclear fusion takes place in the core of a star. The Sun’s nuclear fusion combines the nuclei of hydrogen atoms to form a helium atom. In a nuclear reaction some of the matter is converted in to Energy per the equation E = MC 2

Day 3: Stellar Equilibrium. The Sun is in stellar equilibrium. The inward force of gravity is balanced by the outward force of gas pressure caused by the Sun’s high core Temperature.

Day 2: Hertzsprung-Russell Diagram The H-R diagram is used to classify stars. The vertical line on an H-R diagram indicates brightness in absolute magnitude (true brightness of a star). The horizontal line on the H-R diagram indicates temperature. Most stars appear in a diagonal line called the main sequence (white band on chart). As stars age and pass through different stages, their positions on the H-R diagram change.

Day 2: H-R Diagram 1.Where are most stars located on the HR Diagram? 2.What two properties determines a stars absolute magnitude? 3.Which color stars are the hottest and which are the coolest? 4.From Earth, Sirius is the brightest star on our night sky. How can it appear brighter than Betelgeuse?

Day 3: Interpreting Graphics Base your answers to questions 1 through 4 on the illustration below. Temperature 1. Which of these stars would appear to be brightest if all of them were observed from the same distance? A.Aldebaran B.Canopus C.Sun D.Vega

Day 3: Interpreting Graphics Temperature 2.Proxima Centauri, in the lower left, is the closest star to the Earth. Why is it hard to see from Earth? 3. Which of these stars is most likely to become a white dwarf in the near future? A.Betelgeuse B.Sirius C.Proxima Centauri D.Alpha Centauri

Day 3: Interpreting Graphics Temperature 4. Why does Sirius appear brighter in the night sky than Betelgeuse? A.Sirius is a brighter star than Betelgeuse. B.Betelgeuse is farther from Earth than Sirius. C.Betelgeuse is cooler than Sirius, so it does not emit as much light. D.Sirius has a smaller diameter, so it is a more concentrated light source.

Day 3: Answers 1. B Canopus – it is highest on the absolute magnitude scale. 2. Proxima Centauri is small and has a low temperature compared to other stars. 3. A, The next stage after red giant is a white dwarf. 4. B,