Distance
Parallax Measurements
Parallax is one of the most important distance measurement methods used by astronomers. It can only be used for nearby stars, but it is very accurate.
Reasons to Measure Distances
Measuring Distances
Knowing the distance to objects in space is important. It is also very hard - you can't just use a ruler!
Astronomers over hundreds of years have worked out new ways to measure the distance to stars and galaxies.