Galaxies and the Universe

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What is a galaxy?

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A galaxy is a massive system that consists of stars, stellar remnants, interstellar gas, dust, and dark matter, bound together by gravity.

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What is the universe?

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The universe is the totality of space, time, matter, and energy, including all galaxies, stars, planets, and cosmic structures.

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What is the order of cosmic structures from largest to smallest?

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Universe > Local Group/Cluster > Galaxy > Solar System > Planet.

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What is the Big Bang Theory?

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The Big Bang Theory is the leading scientific explanation for the origin of the universe, proposing that it began as a singularity approximately 13.8 billion years ago and has been expanding ever since.

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What is the Local Group?

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The Local Group is a collection of over 54 galaxies, including the Milky Way, Andromeda, and several smaller galaxies.

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What is an irregular galaxy?

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An irregular galaxy is a type of galaxy that does not have a distinct regular shape, often appearing chaotic in form.

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What is a light year?

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A light year is the distance that light travels in one year, approximately 5.88 trillion miles (9.46 trillion kilometers).

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What is a solar system?

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A solar system is a collection of celestial bodies, including a star and the planets, moons, asteroids, comets, and other objects that are bound by gravity to that star.

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What is the Milky Way?

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The Milky Way is the galaxy that contains our solar system, characterized by its spiral shape and a central bulge of stars.

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What is dark matter?

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Dark matter is a form of matter that does not emit light or energy, making it invisible and detectable only through its gravitational effects on visible matter.