Astronomy is the study of stars, planets & the universe. It gained recognition as a science during Europe’s ______ or revival of learning. Astronomers have divided the sky into constellations to make sense of its patterns. They also use a system of coordinates that’s similar to the latitude & longitude codes used on Earth.
The astronomical unit (symbol: au, abbreviated “AU”) is a standardized measurement of distance in the Solar System and around other stars. It is a fundamental component of the definition of another astronomical unit, the parsec.
Until 2012, the astronomical unit was defined as the average of the distance between Earth and the Sun during one transit of Venus across its face (as calculated using Kepler’s third law of planetary motion). This definition did not depend on the heliocentric gravitational constant G or the mass of the Sun, which cannot be measured accurately. It was therefore practical for the calculation of ephemerides, but it was not consistent with the frame of reference of general relativity.
In 2012, the astronomical unit was redefined to be exactly equal to 149,597,870,700 meters. This new definition was based on a frame of reference that does not depend on the heliocentric gravitational force and the speed of light. The astronomical unit is now the preferred unit of length for astronomical measurements.
The astronomical unit is much too small a measure to be used outside our Solar System, but the Speed of Light gives us a way to calculate the relative distances of astronomical objects. Astronomers also use the term light year to describe distances between stars, galaxies & cosmic structures such as galaxy clusters. The Universe is
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CELESTRON StarSense Explorer DX 130AZ Smartphone App-Enabled Telescope – Works with StarSense App to Help You Find Stars, Planets & More – 130mm Newtonian Reflector – iPhone/Android Compatible
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