Cosmic distance ladder

The cosmic distance ladder refers to the methods by which astronomers determine the distances to celestial objects. Each rung of the ladder provides information that can be used to determine the distances at the next higher rung.

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Many of the rungs involve standard candles — objects whose intrinsic brightness is believed known. By comparing the intrinsic brightness with the actual brightness, one derives a distance.

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At the base of the ladder are radar observations of Venus, which allow one to determine the distance between the Earth and Venus and by extension, the size of the orbit of the Earth.

Related Topics:
Radar - Venus

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The succeeding rungs are:

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• Parallax
• Comparison to the main sequence
• Cepheid variables
• Type Ia Supernovae or the Tully-Fisher relation
• Redshifts

The field of astronomy which measures distances is known as astrometry. The field of astrometry has progressed greatly with the launch of space-based observatories such as Hipparcos which can make extremely precise measurements that serve to strengthen the links between the different rungs in the cosmic distance ladder.

Related Topics:
Astrometry - Space-based observatories - Hipparcos

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