* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Earth in space
Corona Australis wikipedia , lookup
Outer space wikipedia , lookup
Constellation wikipedia , lookup
Definition of planet wikipedia , lookup
Copernican heliocentrism wikipedia , lookup
Astrobiology wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
History of astronomy wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Extraterrestrial skies wikipedia , lookup
Perseus (constellation) wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Chronology of the universe wikipedia , lookup
Observable universe wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Geocentric model wikipedia , lookup
Astronomical unit wikipedia , lookup
H II region wikipedia , lookup
Hubble Deep Field wikipedia , lookup
Planetary habitability wikipedia , lookup
Stellar kinematics wikipedia , lookup
Malmquist bias wikipedia , lookup
Observational astronomy wikipedia , lookup
Star formation wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Cosmic distance ladder wikipedia , lookup
Earth in space Topic 3 in Review Book I. Celestial observations All of the objects in our sky appear to be located on a dome (hemisphere) that encircles the earth This dome is referred to as the celestial sphere a. General Terms 1. The horizon: the imaginary line where the earth appears to meet the celestial sphere 2. The zenith: the point on the celestial sphere directly above an observer… 90º above the horizon 3. 4. Altitude: a vertical angle… the angular distance above the horizon Declination: celestial lines of latitude The celestial equator is the reference point + declination = north - declination = south Azimuth: a horizontal angle: the angular distance measured clockwise from due north. 6. Right Ascension: celestial lines of longitude 5. Right ascension is labeled in units of time… it is given in hours (h), minutes (m) and seconds (s) and ranges from 0h 0m 0s to 24h 0m 0s 7. a. Constellations: groups of stars that appear to form a pattern in the sky Some stars and constellations are circumpolar… they seem to move in circles around Polaris… when photographed, they create circular star trails Circumpolar motion occurs because Polaris is directly above our axis of rotation. The farther north an observer is located, the greater the number of circumpolar stars Circumpolar motion b. c. Stars/constellations change their position in the sky nightly due to the rotation of the earth and… seasonally because of the revolution of the earth We’ll talk more about these motions in the next unit…so stay tuned! d. Some Constellations you should know: i. The Big and Little Dippers: Seen on the horizon in the fall at the zenith in the spring The B.D. contains the pointer stars to Polaris ii. Orion: We only see it in the winter during “prime time” viewing iii. Summer Triangle: We only see it in the summer during “prime time” viewing The Big Bang B. Origin of the universe The Big Bang theory: There is scientific evidence that supports that approximately 14 billion years ago, the universe was a dense concentration of matter that expanded explosively… At this time: all matter and space was created and moved outward in all directions at the speed of light (300 million m/sec), masses of gas cooled and condensed and… stellar systems formed. Evidence of the Big Bang includes: 1. The uniform age of all of the galaxies 2. Weak electromagnetic radiation from the explosion (cosmic background radiation) has been detected C. The fate of the universe In 1929, Edwin Hubble examined the spectra of distant galaxies He compared the spectral lines of far away galaxies to those of nearby stars Hubble knew that when a light source is moving away from an observer it’s wavelength becomes longer… This results in a shift of its spectrum towards the red end conversely, when a light source moves towards an observer, there is a shift towards the blue end of the spectrum He found that the nearby stars had spectral lines similar to those expected. But he found that the distant galaxies showed spectral lines shifted to the red end of the spectrum The shift towards the red end of the spectrum indicated that distant galaxies are moving away from the earth… If the shift had been towards the blue end of the spectrum, the galaxies would be moving towards the earth Hubble’s law Galaxies are retreating from us at a speed proportional to their distance from us The expanding universe theory proposes that the universe is expanding so that objects (galaxies) move away from one another The galaxies aren’t expanding…just the spaces between them D. Classification of stars Stars are classified based on spectral analysis of their light This information is organized on a chart called a Hertzsprung-Russell diagram See ESRT page 15 The H-R diagram is based upon the relationship between the luminosity (brightness) of a star and its temperature In general…hot stars tend to be blue/white and bright… cool stars tend to be red/yellow and not as bright When a star varies from this generalization, an inference can be made regarding where it is in its life cycle E. The Life of A Star Stars begin as clouds of gas or dust that gets pulled together by a developing force of gravity. As the force of gravity builds, and the star becomes hotter, fusion begins to take place. Fusion creates an outward force that is in opposition to the inward pull of gravity. These forces, and how balanced they are, determine the life of a star. Smaller stars last longer than massive stars… Bigger stars are hotter and undergo fusion much faster … therefore, the balance between the forces is upset sooner. Nova Nebula Red Giant White dwarf Main Sequence Star Black Hole Super Giant Protostar Once fuel begins to diminish, the equilibrium Is disrupted Super Nova F. Distances to Stars The sun is the closest star to earth It is 150,000,000 km away This distance is equal to 1 Astronomical Unit (AU) The next nearest star is Alpha Centauri It is ~ 40 trillion km away This would be ~ 266,666 AU To make stellar distances more manageable, we convert distances to light years This is the distance light travels in one year!!! Light 12 9.5x10 travels km/year Which is 9,500,000,000,000 (9.5 trillion) km/year Alpha Centauri is 4.35 ly from Earth It takes the light from the sun 8 minutes and 20 seconds to reach Earth Another unit of distance is a parsec Parsec stands for 1 second of parallax Parallax is the apparent shift in the position of one star in relationship to another star This is equal to 3.26 ly G. Stellar Brightness 1. Luminosity is the actual (true) brightness of a star This is dependent upon size: the larger the star, the more luminous it tends to be and temperature: The hotter the star, the more luminous it tends to be 2. Apparent magnitude is how bright a star appears to an observer on Earth This is influenced by the distance between a star and the observer As distance increases, the apparent brightness decreases This is reported as a numerical value: Brighter stars have lower apparent magnitudes. Apparent magnitude can be reported in negative numbers A star with an apparent magnitude of 6 is the faintest that can be seen with an unaided eye 3. Absolute magnitude is the brightness a star would have if it was located 32.6 ly from Earth This eliminates the effect that distance has on the apparent magnitude of a star This is a comparative brightness and can be used to determine the relative distances between stars and the earth. H. Galaxies and the Universe A galaxy is a system that contains billions of stars There are at least a billion billion galaxies in our universe The sun is located in the Milky Way galaxy and is only one star among 100 billion stars! Neighboring Galaxies Magellanic Clouds the closest galaxies They are only visible from the Southern Hemisphere Andromeda Galaxy the closest galaxy visible from the Northern Hemisphere 1. Types of galaxies Galaxies are classified based upon their shape Spiral galaxies: consist of a central nucleus with “arms” that trail behind while the galaxy rotates The Milky Way is a spiral galaxy 100,000 ly across ii. iii. Elliptical galaxies: range in shape from nearly spherical to lens shaped Irregular galaxies: do not have any specific shape. The stars are spread unevenly throughout the galaxy II. Our solar system Consists of: 1 star 8 planets 61 (and counting) natural satellites thousands of asteroids millions of meteoroids numerous comets Which all travel through space in paths called orbits that are ellipses with the sun at one of the foci a. Models of the universe 1. Geocentric model: Earth-centered Proposes that the earth is stationary at the center of the universe and all of the celestial objects (sun, moon, planets, stars) revolve around it. 2. Heliocentric model Sun-centered In 1543, Copernicus published a paper proposing that the sun was stationary and everything revolved around it. Galileo supported this theory through telescopic observations 3. Evidence of heliocentrism a. Circumpolar motion of stars: provides evidence of the earth’s rotation. If the earth did not rotate, star trails would not be created b. Foucault pendulum: Also provides evidence of the earth’s rotation. Jean Foucault created a free-swinging pendulum that knocked down standing pegs which led to his conclusion that the earth rotates Foucault Pendulum Foucault pendulum 2 c. Coriolis Effect The deflection of a freemoving substance to the right in the Northern Hemisphere and to the left in the Southern Hemisphere due to the rotation of the earth d. Retrograde motion: The apparent backwards motion of a planet against the backdrop of stars. This is due to the variations in rates of revolution III. Orbital geometry A. Kepler’s laws of planetary motion describe the motions of the planets in their orbits around the sun. 1. First law The planets move in orbit around the sun in a path that is an ellipse with the sun at one of the foci An ellipse is a closed curve that ranges in shape from a perfect circle to a straight line. Eccentricity is a measure of the “out-of-roundness” of an ellipse It ranges in value from 0 (perfect circle) to 1 (straight line) As the distance between the foci increases, eccentricity increases and the ellipse becomes more oval Length of the major axis Distance between the foci Now you try! Calculate eccentricity: f 3.7 cm 9.2 cm f E = dbf lma E = 3.7 cm 9.2 cm E = 0.40 2. Second law An imaginary line joining the planet to the sun will sweep out equal areas in equal amounts of time Since the orbit of each planet is an ellipse with some degree of eccentricity, the distance between the planet and the sun will vary throughout its revolution Kepler’s law says that the areas covered each day by the planet will be the same, but the distance traveled will differ This results in variations in the velocity of revolution When the planet is closer to the sun, the distance to travel is greater, so the velocity has to be greater When the planet is farther from the sun, the distance to travel is less, so the velocity is less In summary Orbital velocity is Greatest when the planet is closest to the sun and least when the planet is farthest from the sun D C A B A = perihelion = closest to the sun C = aphelion = farthest from the sun 3. Third law A planet’s period of revolution is directly related to its distance from the sun as distance from the sun increases period of revolution increases This difference in rate of revolution results in retrograde motion which is seen when the earth passes a planet farther from it causing it to look like it is going backwards B. Gravitational attraction Sir Isaac Newton stated Every object in the universe is attracted to every other object in the universe. This attraction is called gravity Force of gravity α m1 m2 d2 Changing distance would have the greatest effect on gravity Increasing mass Increases gravity Increasing distance Decreases gravity