Characteristics of Stars 21.2

 Parallax is the method used by astronomers to study the distance to relatively nearby stars.  Parallax is the apparent change in position of an object when it is observed from a different place

 The 3 Characteristics used to classify stars are Size, Temperature, & Brightness.

 The Sun is a medium size very ordinary star  Giant Stars are stars much bigger than our star the Sun  A star like Betelgeuse would reach as far as the orbit of Jupiter if it was where our Sun is.  Dwarf Stars are stars that are much smaller than our star  Dwarf Stars are only about 20 kilometers in diameter.

 A stars color tells you its temperature, their color indicates the size of the wavelength.  The spectrum is used to indicate temperature  Red/Orange stars have the longest wavelengths, thus they have the lowest temperatures  Blue/White stars have the shortest wavelength and have the highest temperatures

 How bright a star looks from Earth depends on how close it is and how much light it is actually giving off

 Apparent Magnitude is how bright a star is as seen from Earth  Star’s brightness is compared to all the other stars you see in the sky.  Sirius is the brightest star in our night sky  Absolute Magnitude is how bright the star would be if it were as far away as our sun.  To find the absolute magnitude an astronomer must first find the apparent magnitude of the star and then find its distance.

 It classifies stars according to absolute magnitude (brightness) and temperature (color).  A diagonal band called the main sequence is where 90% of all stars fall.  Giant stars are to the upper right, and dwarf stars are to the lower left.