Astronomy Basics

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What are galaxies?

Back

Large systems of stars held together by gravity. Our solar system is part of the Milky Way Galaxy, which contains about 100 billion stars.

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What is space?

Back

The empty volume between celestial bodies, mostly a vacuum with hydrogen, helium, dust, and radiation.

Front

What tools are available for observing stars and planets?

Back

Apps are available to help observe and identify stars and planets in the night sky.

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What is the Geocentric Model?

Back

Proposed by Ptolemy, it places Earth at the center of the universe. It was accepted for 1,500 years.

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What is the Heliocentric Model?

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Proposed by Copernicus, it places the Sun at the center. Proven by Galileo using a telescope.

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What is gravity?

Back

The force of attraction between masses. It is stronger with larger masses and shorter distances.

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What are neutron stars?

Back

Extremely dense remnants of collapsed stars, with immense gravitational force.

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What properties are used to compare planets and moons?

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Comparison is based on mass, gravity, size, and composition.

Front

What is surface gravity?

Back

It varies with mass and radius relative to Earth's gravity.

Front

What is the composition of inner planets, gas giants, and ice giants?

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Inner planets are rocky, gas giants are mostly hydrogen and helium, and ice giants contain frozen water and gases.