How do scientists measure distances in outer space?

Scientists use different methods depending on the distance involved. For nearby stars, they use parallax, which measures the apparent shift in a star's position as Earth orbits the Sun. The distance is calculated trigonometrically from that angular shift. This works reliably up to a few thousand light-years. For greater distances, scientists use standard candles, which are objects with known intrinsic brightness. By comparing how bright they appear to how bright they actually are, distance can be calculated. Cepheid variable stars and Type Ia supernovae are the most common standard candles. For the farthest galaxies, scientists use redshift, measuring how much a galaxy's light has stretched due to the expansion of the universe, which correlates to distance.