Download 16.6 NOTES How do astronomers measure distance? Objective

16.6 NOTES
How do astronomers measure distance?
Objective: Identify two methods astronomers use to measure distances in space
Most astronomers have found that distances to stars are so great that the
numbers are too large to work with easily. For example, Proxima Centauri is the
closest star to earth other than the Sun, and is 40,000,000,000,000 km from
Earth.
Special units are used to measure distances in space. A light year is equal to the
distance light travels in one year (about 10 trillion km). Light from the Sun
reaches Earth in a little more than 8 minutes. Light from the North Star (Polaris),
reaches earth in about 700 years.
Astronomers can use parallax to find out distances to the closer stars. Parallax is
the apparent change in the position of a distant object when seen from two
different places.
An astronomical unit is the average distance from Earth to the Sun. It is equal to
about 150 million km. An astronomical unit, or AU, can also be used to measure
distances in space, especially distances between the planets in the solar system.
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