Chapter #7; Glossary Terms

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Chapter #7; Glossary Terms
2013-01-30 17:56:44

Chapter 7 Glossary Terms
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  1. Celestial object
    Any objects that exist in space, such as the Sun, Moon, the stars and the planets. 
  2. Astronomer
    An astronomer is one who studies astronomy, which is the study of the night sky.

    Famous astronomers include Galilei Galileo and Nicholas Copernicus.
  3. Revolution
    A revolution is the time it takes for an object to orbit another object; Earth's revolution around the Sun is 365.24 days.
  4. Rotation
    A rotation is the turning of an object around an imaginary axis running through it; Earth's rotation around its axis is 24h. 
  5. Constellation
    Constellations are a group so stars that seem to form distinctive pattern in the sky. Such as Orion, Ursa Major and Cassiopiea.

  6. Light-year
    The distance that light travels in one year, which is about 9.6x1012 km. 

    It is a measurement of distance not a measurement of time.
  7. Apparent magnitude
    Apparent magnitude is the brightness of a star as seen from Earth. 
  8. Asterism
    Asterisms are a smaller group of stars that form patterns within a constellation, such as the Big Dipper and the Little Dipper.

  9. Pointer stars
    Pointer stars are stars which are used to find an area of the sky. For example the two end stars found in the Big Dipper  are pointer stars because they point towards Polaris, the North Star.

  10. Tides
    Tides are the rising and falling of ocean waters caused by the Moon's and Earth's gravitational pulls.

  11. Phases of the moon
    The monthly progression of changes in the appearance of the Moon that result from different portions of the Moon's sunlit side being visible from Earth.

  12. Lunar eclipse
    The phenomenon in which the full Moon passes into Earth's shadow.

    • This happens at least twice an Earth year.
  13. Solar eclipse
    The phenomenon in which the shadow of the Moon falls on Earth's surface. They occur every 6 months, which is twice in an Earth year. 

    They are only visible at a specific, often remote, location on Earth so humans don't usually see them. 

    Solar eclipses are dangerous to watch because your pupils get bigger to take in more light when it is dark and since the moon is in between the Earth and the Sun it becomes dark outside during the eclipse. There is still a ring of light visible though since the Sun is so much bigger than the Moon so you will take in too much light, which can burn your eyes.

  14. Why do we have seasons?
    We have seasons because the Earth is tilted on its imaginary axis, and it stays tilted as it revolves around the Sun.

    In the northern hemisphere, it is summer during June 21st to September 21st because the NH is tilted towards the sun causing more direct sunlight to hit the areas in the northern hemisphere. And in our winter months it's colder because the Earth is tilted away from the sun.

  15. Planet (include inner planet & outer planet)
    A planet is an object that orbits one or more stars and is not a star itself. Planets are spherical, and do not share their orbit with other objects.

  16. Solar system
    A group of planets that circle one or more stars.
  17. Retrograde motion
    The movement of an object in the sky, usually a planet, from east to west, rather than its normal motion from west to east; this effect is generally produced when Earth is passing the planet in its orbit.

  18. Astronomical unit
    Astrnomical units (AU) is the average distance between the Earth and the Sun; used to tell the distances between planets. One AU is about 150x10.
  19. Orbital radius
    The average distance between the Sun and an object that orbits the Sun. Measured in AU. 
  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.

  21. Heliocentric model
    A model of the solar system in which the Sun is in the centre with the planets orbiting it.

  22. Comet
    A comet is an object composed of rocky material, ica, and gas; Comes from the Kuiper Belt or Oort Cloud.

  23. Asteroid
    An asteroid is an object that ranges in size from a tiny speck, like a grain of sand, to 500km wide; asteroids originate in the asteroid belt between Mars and Jupiter.
  24. Meteoroid
    A meteoroid is a piece of rock moving through space.Ten tons of meteoroids hit earth's atmosphere everyday, most are the size of a grain of sand. 
  25. Meteor
    A meteor is a meteoroid that hits Earth's atmosphere and burns up.  
  26. Meteorite
    A meteorite is 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. 

    Including Pluto and the largest of which, Eris.