Beyond the Moon

Front

Universe Noun

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[yoo-nuh-vurs]

Back

Universe

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A vast space containing all the matter and energy in existence, which scientists believe is continuously expanding.

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Example: The image shows the Milky Way galaxy, highlighting our Sun's location, illustrating the vastness of the universe.

Front

Big Bang Theory Noun

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[big bang thee-uh-ree]

Back

Big Bang Theory

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The leading scientific theory explaining how the universe began from a single, massive explosion about 13.7 billion years ago.

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Example: The image shows the universe expanding from the Big Bang, illustrating the formation of stars and galaxies over time.

Front

Astronomical Unit (AU) Noun

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[as-truh-nom-i-kuhl yoo-nit]

Back

Astronomical Unit (AU)

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A unit of measurement equal to the average distance between Earth and the Sun, which is about 150 million kilometers.

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Example: The image shows Earth's orbit around the Sun, with distances labeled to explain an astronomical unit.

Front

Light-year (ly) Noun

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[lite-yeer]

Back

Light-year (ly)

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The distance that light travels in one year, which is equivalent to about 9.5 trillion kilometers or 63,000 AU.

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Example: The image shows how far light travels in one year by comparing distances to nearby stars.

Front

Galaxy Noun

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[gal-uhk-see]

Back

Galaxy

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A massive collection of stars, interstellar gas, dust, and dark matter, all held together by gravitational attraction.

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Example: A spiral galaxy showing stars and dust swirling around a bright center.

Front

Spiral Galaxy Noun

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[spahy-ruhl gal-uhk-see]

Back

Spiral Galaxy

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A type of galaxy characterized by a flattened, spinning disk with prominent spiral arms extending from a central bulge.

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Example: The image shows a spiral galaxy with a bright center and spiral arms, illustrating its structure.

Front

Elliptical Galaxy Noun

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[ih-lip-ti-kuhl gal-uhk-see]

Back

Elliptical Galaxy

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An oval-shaped galaxy that contains older stars and has no distinct spiral arm patterns or significant star formation.

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Example: An elliptical galaxy is shown with its smooth, oval shape, highlighting the absence of spiral arms or new star formation.

Front

Star Cluster Noun

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[stahr kluhs-ter]

Back

Star Cluster

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A group of stars that are gravitationally bound to each other, sharing a common origin and moving together.

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Example: A dense collection of stars showing a star cluster, where stars are gravitationally bound.

Front

Nebula Noun

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[neb-yuh-luh]

Back

Nebula

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A large cloud of interstellar gas and dust in space, often serving as a birthplace for new stars.

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Example: A nebula is a colorful cloud of gas and dust in space where new stars can form.

Front

Star Noun

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[stahr]

Back

Star

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A large, hot ball of gas that generates energy in its core through nuclear fusion reactions.

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Example: The Sun, a star, emits energy that travels to Earth.