How Stars are Classfied

1. How Stars are Classfied

2. Star Magnitude • At night we can see thousands of stars but during the day we can only see our one star, the sun. • How bright a star looks depends on two factors: its magnitude and its distance from Earth. • Def: magnitude- brightness perceived • Def: Apparent magnitude- how bright the star seems to be. • Def: absolute magnitude- how bright it really is

3. Types of stars • The color of a star is a clue to it’s surface temperature. • Blue stars are hotter; red stars are cooler. Yellow stars are in between. • Most stars are sorted by a main sequence. Main sequence shows the order of the stars from hottest to coolest, and brightest to dimmest. • About 95% of the stars scientists find and observe can be classified as main sequence stars. • These are the stars that fall on the diagonal line.

4. Observing Stars • Energy of all stars travels in waves. Scientists learn about stars by studying the energy that the stars send into space. Each kinds of wave carries a different amount of energy. • Telescopes can gather more light than the human eye can. • The larger the telescope, the more light it can gather, and the farther into space it can “see”. • Each wave of energy from stars give scientists info about the objects it formed from. • This is how scientists know the sun and most stars are mostly hydrogen and helium.

5. Homework • Do workbook pages 250, 253, 254 AND……finish your graphic organizer