What are stars? Glencoe: Chapter 26-2 Outline

Astronomy The study of objects and matter outside the Earth’s atmosphere and of their physical and chemical properties.

I. What are stars? A. Ancient peoples (Greeks) thought that all stars were equal distance from the Earth - They grouped stars into patterns called constellations

What are stars?  depicted characters in mythology

What are stars? - We know now that the stars in a constellation are not necessarily very close together, but appear to be due to our line of sight - Examples – Orion, Ursa Major (Big Dipper)

B. Our sun - Average in size - Average in temperature - Diameter is 110 times the size of the Earth - Mass = 300,000 times that of Earth - Slightly more dense than water

C. Star brightness - Depends on the star’s temperature, size, and distance from the Earth

- Visible light - Electromagnetic radiation at other wavelengths  x-rays, radio waves, ultraviolet waves - Today’s sophisticated telescopes can detect and chart all these types of waves D. We learn about stars by studying their light

E. Star color is related to star temperature - Hotter stars emit more intense light at the shorter wavelengths  more blue light - Cooler stars emit more intense light at the longer wavelengths  more red light

E. Star color is related to star temperature - Color is determined by which color / wavelength is emitted the most *Our sun emits yellow light as its most intense wavelengths - From studying our sun’s light, we have determined that the sun is 90% hydrogen atoms

F. Stars are huge fusion reactors - Hydrogen atoms are fused to make helium atoms and release energy out - Energy then moves through the parts of a star and out into space