Science Unit 4- Chapter 1

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  1. Celestial object
    A natural object which is located outside of Earth's atmosphere, such as the Moon, the Sun, an asteroid, planet, or star
  2. Astronomer
    Astronomy is a natural science that deals with the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies)
  3. Revolution 
    The action by a celestial body of going round in an orbit or elliptical course; also : apparent movement of such a body round the earth
  4. Rotation
    A rotation is a circular movement of an object around a center (or point) of rotation
  5. Constellation 
    In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms (which themselves are generally referred to in non-technical language as "constellations"), which are patterns formed by prominent stars within apparent proximity to one another on Earth's night sky.
  6. Light-year
    A light-year is a unit of length equal to just under 10 trillion kilometres (or about 6 trillion miles). As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in one year
  7. Apparent magnitude
    The apparent magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth
  8. Asterism
    In astronomy, an asterism is a pattern of stars recognized on Earth's night sky. It may form part of an official constellation, or be composed of stars from more than one.
  9. Pointer stars
    Pointer stars are stars which are used to find an area of the sky
  10. Tides
    Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.
  11. Phases of the moon
    A time when the Moon presents a particular recurring appearancephase. The particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun); "the full phase of the moon"
  12. Lunar eclipse
    A lunar eclipse occurs when the Moon passes directly behind the Earth into its umbra (shadow)
  13. Solar eclipse
    As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and Earth, and the Moon fully or partially blocks the Sun
  14. Why do we have seasons?
    The Earth's axis is tilted at an angle of 23.5 degrees. This means that the Earth is always "pointing" to one side as it goes around the Sun. So, sometimes the Sun is in the direction that the Earth is pointing, but not at other times. The varying amounts of sunlight around the Earth during the year, creates the seasons
  15. Planet (include inner planet & outer planet)
    The inner planets are the first four planets closest to the Sun, which includes Mercury, Venus, Earth, and Mars. The outer planets are Jupiter, Saturn, Uranus, and Neptune. The inner and outer planets are separated by the asteroid belt, which is a region of space where thousands of asteroids can be found.
  16. Solar system
    The Solar System consists of the Sun and its planetary system of eight planets, their moons, and other non-stellar objects
  17. Retrograde motion
    Retrograde motion is the motion of a planetary or other body in a direction opposite to that of other bodies within its system as observed from a particular vantage point.
  18. Astronomical unit [AU]
    An astronomical unit (abbreviated as AU, au, a.u., or ua) is a unit of length equal to exactly 149,597,870,700 metres (92,955,807.273 mi) or approximately the mean Earth–Sun distance.
  19. Orbital radius
    Assuming, though this assumption is a simplification of the truth, that the planets orbit the Sun in a perfect circle the orbital radius is nothing but the distance from the planet to the Sun, or roughly one astronomical unit in the Earth's case
  20. Geocentric model
    In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system), is a description of the cosmos where the Earth is at the orbital center of all celestial bodies.
  21. Heliocentric model
    The heliocentric model is a theory that places the Sun as the center of the universe, and the planets orbiting around it.
  22. Comet
    A comet is an icy small Solar System body
  23. Asteroid
    Asteroids are a class of small Solar System bodies in orbit around the Sun.
  24. Meteoroid
    A meteoroid is a sand- to boulder-sized particle of debris in the Solar System
  25. Meteor
    A meteor is the visible path of a meteoroid that has entered the Earth's atmosphere.
  26. Meteorite
    A meteorite is a natural object originating in outer space that survives impact with the Earth's surface.
  27. Trans-Neptunian object
    A trans-Neptunian object is any object in the Solar System that orbits the Sun at a greater average distance than Neptune.
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Science Unit 4- Chapter 1
2012-12-19 01:49:11
Science Unit Chapter

Science Unit 4- Chapter 1
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