Chapter 27 Stars and Galaxies Section 1

27.1 Characteristics of Stars A star is a body of gases that gives off a tremendous amount of radiant energy in the form of heat and light. A star is a body of gases that gives off a tremendous amount of radiant energy in the form of heat and light. Stars vary in size, color, and mass Stars vary in size, color, and mass Some have a diameter as small as 20 km Some have a diameter as small as 20 km Others have diameters as big as 1 billion km Others have diameters as big as 1 billion km

27.1 Characteristics of Stars A spectrometer is a device that separates light into different colors, or wavelengths A spectrometer is a device that separates light into different colors, or wavelengths Starlight passing through a device for separating light produces a display of colors and lines called a spectrum

27.1 Characteristics of Stars An apparent shift in the wavelength of light emitted by a light source moving toward or away from an observer is known as The Doppler Effect A star moving toward the earth would display a blue shift A star moving away from the earth would display a red shift

27.1 Characteristics of Stars Light from the sun takes about 8 minutes to reach the earth. Light from the sun takes about 8 minutes to reach the earth. So the sun is 8 light-minutes from the earth So the sun is 8 light-minutes from the earth The apparent change in the position of an object resulting from a change in the angle or in the position from which it is viewed is called parallax.

27.1 Characteristics of Stars The apparent magnitude of a star is a measure of its brightness as it appears from the earth. The faintest star that can be seen by the unaided eye has an apparent magnitude of +6. The faintest star that can be seen with a telescope has an apparent magnitude of +29

27.1 Characteristics of Stars The brightest star in the night sky has an apparent magnitude of The brightest star in the night sky has an apparent magnitude of The sun has an apparent magnitude of The sun has an apparent magnitude of So, an apparent magnitude of -30 would be the brightest and +30 would be the faintest So, an apparent magnitude of -30 would be the brightest and +30 would be the faintest

27.1 Characteristics of Stars Main-sequence stars are visible in the night sky and the sun Main-sequence stars are visible in the night sky and the sun A large, bright star that is cool is called a giant A large, bright star that is cool is called a giant Super-giants are just larger versions of giants Super-giants are just larger versions of giants A very hot but small and dim star is called a white dwarf A very hot but small and dim star is called a white dwarf