What are the apparent motions of celestial objects
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What are the apparent motions of celestial objects? PowerPoint PPT Presentation

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What are the apparent motions of celestial objects? . Celestial Object. Anything beyond our atmosphere . Constellations. Constellation. a region of space There are 88 constellations a group of stars that forms a pattern is an Asterism. 3. Examples:. Virgo Orion Sagittarius Taurus

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What are the apparent motions of celestial objects?

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What are the apparent motions of celestial objects?

Celestial Object

  • Anything beyond our atmosphere



  • a region of space

  • There are 88 constellations

    a group of stars that forms a pattern is an Asterism

3. Examples:

  • Virgo

  • Orion

  • Sagittarius

  • Taurus

  • Cancer

  • Aquarius

  • Pisces

  • Scorpius

  • Aries

  • Leo

  • Ursa Major

Star Trails

Traces of light left on a photographic record of stars (long exposure)


A view of the GEMINI North dome soon after sunset showing star trails from a time-lapse exposure. Also seen are trails from vehicle headlights as they drive passed the GEMINI dome.


What apparent motions do we observe?

  • Arcs

  • Most stars and planets rise in the East and set in the West

  • The stars positions change throughout the night (except for Polaris) because Earth rotates and Polaris aligns with the spin axis.

Polaris’ nightly position

  • North, stationary, and its altitude is equal to the observer’s latitude

Circumpolar stars

  • circle Polaris counterclockwise





What causes the apparent motion of celestial bodies?

  • Earth’s rotation causes this apparent motion

  • 360⁰/24 hrs or 15 ⁰/hr


These star trails were photographed in south Texas at 30 degrees north latitude. Orion is in the center, as in the previous image. Latitude explains why these trails are slanted. Near the equator, in East Africa, stars in the eastern sky trail directly up and over your head. At higher latitudes, as here, you are tilted with respect to the rotating "sphere" of the sky. At either pole the stars would go around the horizon. This sky is blue, photographed with the same lens as the previous image and on the same emulsion (Provia 100), processed by the same photo lab.


View East at Equator

Southern Hemisphere sky


This picture shows the Magellan Telescopes with the backdrop of the northern sky. The star trails here represent a one-hour exposure. What you are seeing is the rotation of the Earth, apparently causing the stars to move!



South Pole

This is another picture of the South Pole, but shorter. Two nearby galaxies are visible in this image. The large fuzzy one, just above the roof of the Commons Building, is the Large Magellanic Cloud, and the smaller fuzzy patch near the top of the image is the Small Magellanic Cloud. These galaxies are 200,000 light years away, yet easily visible to the naked eye in dark skies!


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