Space Chapter 7

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  1. Celestial Oobject
    Any object that exists in space, such as a planet, a star or the Moon.
  2. Astronomer
    A scientist who studies astronomy, which is the study of the night sky.
  3. Revolution
    • The time it takes for an object to orbit another object (a year); Earth’s revolution around the Sun takes 365.24 days (an Earth year).
    • Mars’ year is 1.88 Earth years, Jupiter's is 11.86, Neptune's is 164.8, etc.
  4. Rotation
    • The turning of an object around an imaginary axis running through it.
    • Earth’s rotation takes 24 hours, Jupiter's takes 10 hours, Venus' takes 244 hours, etc.
  5. Constellation
    • A group of stars that seem to form a distinctive pattern in the sky.
    • E.g., Orion, Ursa Major, Libra
  6. Light-year
    The distance that light travels in a year, about 9.5*1012 km
  7. Apparent magnitude
    • The brightness of a star as seen from Earth.
    • A magnitude scale devised by the Greek astronomer Hipparchus; 1 being the brightest star you can see and 6 being the faintest, with 2 = 1/2 of 1, 3 = 1/3 of 1, 4 = 1/4 of 1, etc.
    • Today the scale goes from the brightest being-26 which is the Sun to even dimmer than 6.
  8. Asterism
    • Smaller groups of stars that from patterns within a constellation or a group of stars within multiple constellations.
    • E.g., the Big Dipper (part of Ursa Major), and the Summer Triangle (part of Aquila, Cygnus, and Lyra).
  9. Pointer stars
    • Two stars that when you make a line between them, the line points to another star.
    • E.g., the two end stars of the Big Dipper point to Polaris/the North Star.
    • Displaying 2013-12-16_20-56-34.png
  10. Circumpolar
    • A constellation that is seen in the sky year-round.
    • E.g., Cassiopeia, Cepheus, Ursa Major, Ursa Minor, and Draco.
  11. Zenith
    • The constellations that you would see if you looked straight up.
    • This varies depending on time of night, time of year, and viewing latitude.
  12. Tides
    The rising and falling of ocean waves as a result of the Moon’'s gravity and the Earth'’s gravity.

    Displaying 2013-12-16_20-55-54.png
  13. Phases of the Moon
    The monthly progression in the appearance of the Moon, which is the result from different portions of the Moon’s sunlit side being visible from Earth.Displaying 2013-12-16_20-53-32.png
  14. Lunar eclipse
    • The phenomenon in which the full Moon passes into the
    • Earth’s shadow.
    • This happens during a full moon since this is when the Moon is behind Earth, it occurs roughly twice a year, the reason this doesn't happen every full moon is that the Moon’s orbit is tilted approximately 5° to Earth’s orbit around the Sun.
    • Displaying 2013-12-16_20-50-43.png
  15. Solar eclipse
    The phenomenon in which the shadow of the Moon falls on Earth’s shadow. This occurs an average twice a year when the moon comes between the Sun and Earth. The shadow of the Moon is quite small so you have to be in a very specific place to see it (umbra) otherwise you will only see a partial solar eclipse (penumbra).Displaying 2013-12-16_20-47-06.png
  16. Why do we have seasons?
    Since Earth is tilted 23.5° from the flat plane of Earth’s orbit different parts of Earth tilt towards the Sun at different times of the year. During June, July, and August the northern hemisphere is tilted towards the Sun so the sunlight is more concentrated and the temperature is hotter, this is what causes summer. The opposite goes for December, January, and February. During spring and autumn the Equator faces the Sun so day and night are equal; this is what causes spring and autumn.Displaying 2013-12-16_21-19-32.png
  17. Planet
    • An object that orbits one or more stars (and is not a star itself), is spherical, and does not share its orbit with another object.
    • In our solar system there are the inner planets; Mercury, Venus, Earth, and Mars, which are smaller, have less mass, and mainly composed or rock and metal, and the outer planets; Jupiter, Saturn, Uranus, and Neptune, which are a lot larger, have a lot more mass, and are mainly composed of gases.
  18. Solar system
    A group of planets that circle one or more stars.
  19. 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.Displaying 2013-12-16_20-42-34.png
  20. Astronomical unit
    The average distance between Earth and the Sun, about 1.5 * 108 km (150 million kilometres).
  21. Orbital radius
    The average distance between the Sun and an object that is orbiting the Sun.
  22. Geocentric model
    A model of the solar system that stated the Earth was the centre of all planetary motion and that the Planets and the Sun orbited the earth in perfect circle. This originated in ancient Greece and was the accepted model for 1500 years.
  23. Heliocentric model
    A model of the solar system that stated that the Sun was the centre of the solar systems and that all the planets orbited around it. Originally stated that the orbits were perfect circles but later revised to be ellipses.
  24. Comet
    • An object composed of rocky material, ice, and gas; they usually come from the Kuiper Belt or Oort Cloud.
    • Some comets are periodic meaning they orbit the sun while others only visit our solar system once and continue their journey through space.
    • A comet’s tail is caused by radiation from the Sun releasing gas and particles inside the comet, the solar wind then carries these away from the sun, and finally light reflects off these particles and that’s what you see as the tail.
    • Displaying 2013-12-16_20-40-56.png
  25. Asteroid
    • A small object 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.
    • Asteroids generally orbit a star.Displaying 2013-12-16_20-37-55.png
  26. Meteoroid
    A piece of rock moving through space.
  27. Meteor
    A meteoroid that hits Earth’s atmosphere and burns up.
  28. Meteorite
    A meteoroid that is large enough to pass through Earth’s atmosphere and reach the ground, without being totally burnt up.
  29. Trans-Neptunian object
    • An object that circles the Sun beyond the orbit of Neptune. They are located in the Kuiper belt.
    • E.g., Pluto, Dysomnia, Sedna, etc.
Card Set
Space Chapter 7
My glossary terms for space chapter 7.
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