STARS

There are MORE than 200 billion, billion stars in a universe. Most stars contain mainly hydrogen and helium.

Color of a star: tells what the surface temperature of the star is HOTTEST STAR: shines with a blue-white light COOLEST STAR: shines with a red light

Star Temperatures http://www. eudesign. com/mnems/startemp Star Type Temperature Color K ◦C ◦F O > 25,000 > 24,727 > 44,540 blue B 11,000 – 25,000 10,727 – 24,727 19,340 – 44,540 A 7,500 – 11,000 7,227 – 10,727 13,040 – 19,340 white F 6,000 – 7,500 5,727 – 7,227 10.340 – 13,040 yellow G 5,000 – 6,000 4,727 – 5,727 8,540 – 10,340 3,500 – 5,000 3,227 – 4,727 5,840 – 8,540 red M < 3,500 < 3,227 < 5,840 OUR SUN

Absolute Magnitude Apparent Magnitude II. Magnitude: star’s brightness (luminosity) Absolute Magnitude The actual brightness of a star How bright it IS Apparent Magnitude The brightness of a star as viewed from Earth How bright it SEEMS

Apparent magnitude affected by: Distance Size Temperature

H-R Diagram --illustrates the relationship that exists between the average surface temperature of stars and their absolute magnitude. As absolute magnitude(brightness) increases, surface temperature increases.

Star Brightness vs Temperature