The Sun

Motion 300 km/s (186 mi/s) Toward a point in the constellation Hercules Travels in an orbit around the center of the Milky Way galaxy About 3/5 of the distance from the center to the edge

Size Diameter is 1.4 million km (868,000 miles) 109 times the diameter of earth The moon looks about the same size because it is 400 times closer to earth Medium size in comparison to other stars Contains 99% of matter in our solar system 330,000 times more massive than the earth 2000000000000000000000000000 metric tons!

Energy 93% of output is in the form of Electromagnetic Waves 7% of output is in the form of Neutrinos (tiny particles that travel at the speed of light and can penetrate matter light-years in thickness) Light is measured in wavelengths (distance from one crest to the next) We see different wavelengths as different colors Some light we can see, but some has wavelengths that are too long or too short for us to detect.

Energy Light from the sun and other stars contains energy of all wavelengths (colors of the rainbow), just different amounts of each color. Color depends on temperature of the star… cooler – red (longer wavelengths) hotter – blue (short wavelengths) Sun is between these extremes – middle color is most intense Humans see yellow light best and the atmosphere allows yellow light to pass through easiest.

Composition Astronomers use a “spectroscope” to fingerprint the light coming from stars and planets. By recording an object’s spectrum (wavelengths that compose the light from an object) the spectroscope allows astronomers to determine what elements are present and how much of each is present. Sun = hydrogen and helium (98%) Helium was found in the sun before it was found on earth (helios in Greek means “sun”)

Spectroscope

Spectroscope An instrument used to identify colors (wavelengths) of light Separate light into its component wavelengths – “spectrum” Wavelengths that are more abundant are brighter Use a diffraction grating to separate wavelengths