Measuring Distances Beyond the Solar System Introduction In unit eight, you learned about the astronomical unit (AU) which is used to measure distances within the solar system. However, they are too small to measure beyond the solar systems, therefore scientists use a larger unit of distance to measure the distance between stars - the light year. Although the light year sounds like a unit that measures time, it measures distance. A light year is the distance that light travels in empty space for one year. Light travels at a constant speed of 300 000 km/s, which means one light year is approximately equal to ten trillion kilometres. Light years (cont’d) As aforementioned, the primary units that astronomers use to measure the distances between celestial bodies are called light years. On top of one light year being approximately 10 trillion km ((9.46 × 1012 km). The light year can tell us how long light from a star takes to reach Earth. For example, the star Alpha Centauri is 4.37 light years (ly) away which means that light from it takes 4.37 years to reach us. This means that when we observe Alpha Centauri from Earth, we are seeing it 4.37 years in the past. Other light units are also derived from the light year, such as a light second, a light minute or even a light century. These units have the same …show more content…
The measurement of a parallax relies on geometry. Larger parallaxes are easier to measure. To measure a parallax a baseline is necessary. The baseline is typically the length of the Earth's diameter. Parallaxes are used to calculate the distance between stars using triangulation. This measurement uses the principle that if one side and two angles of the triangle is known, the rest of the dimensions can be calculated. since stars are such a great distance away from Earth, astronomers measure a parallax from very spread out