science glossary terms chapter 7

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alexisboudreau
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188165
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science glossary terms chapter 7
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2013-01-03 18:18:28
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grade 9 ms day chapter 7 glossary terms
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  1. Celestial object
    • A celestial object is any object that exists in space.
    • eg. stars, planets, moon.
  2. Astronomer
    A scientist who studies astronomy.

    ex. early astronomers believed that a sign such as an eclipse meant that the dieties (gods) were getting restless, and they would do something to please them to return order to the sky
  3. Revolution
    • The time it takes for an object to orbit another object
    • eg. Earth's revolution around the sun is 365.24 days (1 year)
  4. Rotation
    • The turning of an object around an imaginary axis running through it.
    • eg. earth's rotation aroung its axis is 24 hours (1 day)
  5. Constellation
    • A group of stars that seem to form a distinctive pattern in the sky
    • The stars appear to lie close to eachother and at exactly the same distance from earth. They look close together because they lie in the same line of sight.
    • eg. Orion, Taurus, Pisces, Scorpio
  6. Light -year
    • The distance that light travels in 1 year.
    • The speed of light is 300,000 km/s
    • Light travels about 9.5 x 1012 km in a year
  7. Apparent magnitude
    Apparent magnitude is the brightness of a star as seen from earth.
  8. Asterism
    • A smaller group of stars that form patterns WITHIN a constellation.
    • i.e. big dipper, little dipper, summer triangle.
  9. Polaris and the Pointer stars
    • The big dipper's two end stars are called the pointer stars because they point toward polaris (North star)
    • Polaris has been used for thousands of years in northern hemisphere to tell direction
  10. Tides
    The rising and falling of ocean waters caused by the Moon's and Earth's gravity.
  11. Phases of the moon
    The monthly progression of changes in the appearance of the moon, which result from different portions of the moons sunlit side being visible from earth.
  12. Lunar eclipse
    • When the full moon passes into earth's shadow.
    • During a lunar eclipse, the full moon passes through the umbra portion of earth's shadow so the earth is between the sun and the moon.
    • This event occurs twice a year, and is safe to watch
  13. Solar eclipse
    • When the shadow of the moon falls on earth's surface.
    • the moon is between the sun and the earth during a new moon.
    • happens aboutr twice a year, but can usually only be seen from a very specific, often remote, place on earth.
  14. Why do we have seasons?
    • The seasons are a result of the earth's revbolution around the sun, and the rotation around it's axis.
    • in the winter, the northern hemisphere is tilted away from the sun, and in the summer it is tilted toward the sun.
  15. Planet (include inner planet and outer planet)
    • A planet is an object that orbits one or more stars, (and is not a star itself) , is spherical, and does not share it's orbit with another object
    • there are inner and outer planets. the inner, or terrestrial planets, are rocky and small. The outer planets, or gas giants, are made of gasses and are huge in comparison. 
    • INNER PLANETS; Mars, Earth, Venus, Mercury.
    • OUTER PLANETS; Jupiter, Saturn, Uranus, Neptune
    • ;image;
  16. Solar system
    • A group of planets that circle one or more stars.
    • Our solar system is made up of the sun, the planets (mercury, venus, earth, mars, jupiter, saturn, uranus and neptune) and other smaller objects.
  17. Retrograde motion
    • The movement of an object in the sky, usually a planet, from west to east, rather than it's normal motion from west to east.
    • this is because earth moves faster than outer planets, causing to catch up and move between them.
  18. Astronomical unit
    • (AU) The average distance between earth and the sun, about 150 million km, or 1.5 x 108 km.
    • The earth is 1 AU from the sun.
  19. Orbital radius
    Orbital radius is the average distance between the sun and an object orbiting the sun.
  20. Geocentric model
    • A model of the solar system stating that Earth is the centre of all planetary motion, with the planets and sun travelling in perfect circles around Earth.
    • (geo means earth ;)
    • based on the work of Ptolemy, a greek astronomer.
    • model for 1500 years.
  21. Heliocentric model
    • A model of the solar system in which the sun is in the centre with the planets orbiting it.
    • Based on the work of Copericus, a polish astronomer.
    • A german astronomer by the name of J. Kepler demonstrated that the orbits of the planets are ellipses.
  22. Comet
    • An object composed of rocky material, ice, and gas.
    • comes from the kuiper belt, or Oort cloud.
  23. Asteroid
    • An object in space that ranges in size from a tiny speck, like a grain of sand, to 500km wide.
    • most asteroids originate in the asteroid belt between Mars and jupiter
  24. Metioroid
    • A piece of rock moving through space
    • Are said to be chunks of rpock that have broken off of asteroids and planets.
  25. Meteor
    • A metioroid that hits Earth's atmosphere and burns up.
    • A meteor shower occurs when earth passes through an area where there is a lot of excess material, such as debris left over from a comet.
  26. Meteorite
    A meteoroid that is large enough to pass through Earth's atmosphere and reach the ground, without being totally burned up.
  27. Trans-neptunian object
    • Objects that circle the sun beyond the orbit of Neptune.
    • they are located in the Kuiper Belt (disc shaped group of millions of small objects orbiting the sun)

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