Characteristics of Stars • A star is a _________________________ ___________________________________. • Size varies • Color varies__________________. • Our sun is an average star
Composition • Star composition observed through a spectrometer • Separates light _________________________. • Each color represents a different wavelength • Three types of spectra - - - • Since different elements absorb different wavelengths of light , elements can be determined.
Composition Continued • __________is the most common element. • Surface temperature of a star is indicated by the color • _________are the coolest and _______ are the hottest (Figure 2 on page 776).
Motion • Two kinds of motion associated with stars: • ____________--- just like it sounds! • ____________--- This is motions visible to the unaided eye in a dark sky; due to movement of Earth.
Motion Continued • Some stars create circular trails around a central star (Polaris aka the North Star) - • Different stars become visible during different seasons. • Three actual motions: 1. 2. 3.
Distance • Distance • Light Year = 9.5x1012km; Distance that light travels in one year. • Astronomical Unit (AU) _________ _____________________________ ________________.
Stellar Magnitude • Magnitude:______________________________________________________________. • Apparent magnitude = brightness of a star as it appears to us on Earth • Measure light from star using telescopes • Measurement is then assigned a number Brightest stars have lowest numbers • Dimmest stars have highest numbers • Absolute:___________________________.