Unformatted text preview: ravels in one year. in One light year is 5.8 trillion miles Stellar Brightness Stellar Factors Factors that control the apparent brightness of stars: 1) How big it is 2) How hot it is 2) 3) How far away it is 3) Magnitude Magnitude This is the measure of a star’s brightness Two types of magnitude: 1) apparent Two magnitude 2) absolute magnitude magnitude Apparent Magnitude Apparent This This is a measure of how bright a star is when viewed from the Earth when The sun has the highest apparent The magnitude magnitude Absolute magnitude Absolute This This is the measure of a star’s true brightness. brightness. Absolute magnitude is based on viewing Absolute the star from a standard distance of 32.6 light years light Hertzsprung-Russell Diagram Hertzsprung-Russell Classifies Classifies stars based on color and surface temperature surface Very hot stars with temperatures above Very 30,000 K appear blue in color 30,000 Very cool stars (temperatures below 3,000 Very K) appear red in color K) Stars like our star sun (temperatures Stars between 5000-6000 K) appear yellow in color color Hertzsprung-Russell Diagram (cont.) (cont.) On On the H-R diagram, stars are grouped according to size, magnitude, luminosity, and surface temperature and Ninety percent (90%) of all stars fall into Ninety the category of “ordinary” stars, also called main sequence stars main The hottest main sequence are usually the The brightest stars and the coolest stars are usually the dimmest usually Hertzsprung-Russell Diagram (cont.) (cont.) Our sun is a yellow, main-sequence star. Our sun is considered to be an average Our star. star. Giants and supergiants Giants Red Red giants:Large, cool stars of high luminosity luminosity Supergiants: Very large stars of higher Supergiants: luminosity than ordinary red giants (example: Betelgeuse) (example: White dwarfs White White White dwarfs are faint, hot stars, much smaller than our sun in size but about the size of our Earth size Not all white dwarfs are white Interstellar Matter Interstellar Nebula: Nebula: A cloud of interstellar cloud and/or dust dust Two types of nebulae: 1) emission Two nebulae and 2) reflection nebulae nebulae Emission nebulae Emission Gaseous Gaseous masses that consist largely of hydrogen hydrogen They absorb ultraviolet radiation given off They by a nearby or embedded hot star by Example: Orion Nebula Reflection Nebulae Reflection Reflects the light of nearby stars Composed of large particles called Composed interstellar dust interstellar Example: The Pleiades star cluster It It is from interstellar matter that stars and planets are formed planets Stellar Evolution Stellar Stars mainly exist because of gravity Stages of stellar evolution (for stars like Stages our...
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- Fall '10
- Solar System, atmosphere atmosphere