Iblog.dearbornschools.org



29.2 Measuring the Stars46863009969500Groups of StarsConstellationsGroups of stars that form animals, everyday objects and mythological characters in the skyThere are 88 constellations named by ancient peopleSome are visible throughout the year depending on your locationCircumpolar constellations appear to rotate around the North Pole. In the northern hemisphere, the Big Dipper is a circumpolar constellation Some constellations are seen in the northern hemisphere or southern hemisphere, therefore constellations are classified as spring, summer, fall, or winter constellations.Zodiac constellations can be seen in both the northern and southern hemispheres because they lie in the elliptical plane along the same path where planets are seen. They were used by ancient people to determine planting seasons, harvest time and ritual celebrations.548640011303000400050011303000Star clusters A group of stars that are gravitationally bound to each otherStars appear next to each other because the human eye cannot distinguish how far or near the stars areOpen Cluster – stars not densely packed togetherGlobular cluster – start that are densely packed together5829300571500Binary starsWhen only two stars are gravitationally bound together and orbit a common center of mass. Most binary stars appear to be single stars.More than ? the stars in the sky are either binary stars or are part of a multiple star system.Doppler shiftsWhen a star is moving toward the observer, the light emitted by the star shifts toward the blue end of the electromagnetic spectrum.When a star is moving away from the observer, the light emitted by the star shifts toward the red end of the electromagnetic spectrum.This can be used to determine the speed and direction of a stars motion. 16002005461000Light yearThe distance light travels in a year. 9.461 x 1012km or 5,878,790,000,000 mi. 3.261 light years = 1 parsec.4000500000ParallaxThis is the apparent shift in position of a star caused by the motion of the observer. As Earth moves from one side of its orbit to the opposite side, a nearby star seems to be shifting back and forth.The closer the star, the larger the shift.The distance to the star can be determined by measuring the angle of change Basic Properties of StarsThe basic properties of a star are mass, diameter, luminosity and temperature. Apparent magnitudeThis is how bright a star appears to be.The smaller the number, the brighter the star.Absolute magnitudeThis is how bright a star is if it were 32.6 light years for Earth.The only disadvantage of this is you can only calculate the absolute magnitude when the actual distance of the star is known.TemperatureO, B, A, F, G, K, M are the letters used to classify the temperatures of stars. O is the hottest and M is the coolest. Temperatures range anywhere from 50,000°K (89,540°F) for O stars to 2,000°K (3,140°F) for M stars.Hotter stars put out more light than cooler stars. Color also indicates a stars temperature. These are the colors in order from hottest to coolestCompositionAll stars are made up of nearly the same elements. They are 73% Hydrogen 25% Helium 2% of all other elementsH-R diagram – Hertzsprung-Russell diagramThis diagram compares a stars temperature and it’s absolute magnitude.The upper left corner of the diagram is where hot, bright stars are located.The lower right of the diagram is where stars are cooler and dimmer.The middle portion of the H-R diagram is where main sequence stars are located. 90% of all stars including the Sun are main sequence stars.The lower left of the H-R diagram has stars called white dwarfs. These are about the size of Earth. They are small, dim, hot stars but have the mass about as large as the Sun.80010068580000The upper right of the H-R diagram has stars called red giants. They are very bright, but very cool and extremely large. They are 100 more times the size of the Sun. ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download