What is a light year?

A light year is the distance that light travels in one year in the vacuum of space.


1 light year is approximately 9.46 trillion kilometres.

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What is an astronomical unit (AU)?

An astronomical unit is the average distance between the Earth and the Sun, approximately 150 million kilometres.

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How is an astronomical unit used?

Astronomers use the astronomical unit to measure distances within our solar system.

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What is a parsec?

A parsec is a unit of distance used in astronomy, equal to about 3.26 light years.

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What does 'parsec' stand for?

Parsec stands for 'parallax of one arcsecond', a method used to measure distances to objects in space.

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How is a parsec different from a light year or an astronomical unit?

A parsec is much larger than a light year or an astronomical unit, and is used to measure larger cosmic distances.

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Which is the largest unit of distance: a light year, an astronomical unit, or a parsec?

A parsec is the largest unit of distance among these. It is equivalent to about 3.26 light years or 206,265 astronomical units.

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What is the formula that links parallax in seconds of arc (p), and distance in parsec (d)?

p = d1​


p = parallax in seconds of arc

d = distance in parsec

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