Understanding the Universe

List and explain the three shapes of galaxies. Who came up with the classification of galaxies?

What is the shape of our galaxy? What is our galaxy called?

What is the purpose of a model?

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The distance between a central object and its circling object.

• Orbital radius
• Planetary radius

Explain how an object’s orbital radius can alter the time it takes to move around a central object.

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Explain apparent retrograde motion. In your description refer the planets Earth and Mars. Show your understanding of celestial bodies, astronomical bodies, and orbital radius.

All objects in space.

• Astronomical Bodies
• Celestial Bodies

All objects visible in the sky.

• Astronomical Bodies
• Celestial Bodies

Billions of stars held together by gravitational force.

• Solar System
• Universe
• Galaxy

A star and all the astronomical bodies affected by the star's gravity.

• Solar System
• Universe
• Galaxy