How do astronomers know for sure that stars are really as far away as they state?
Thank you for writing the “Ask a High-Energy Astronomer” service with your question. The methods astronomers use to measure distances to the stars is a piece of fundamental and active work in astronomy with important implications for how we understand the Universe around us. Measuring the distances to stars is kind of like a house of cards: we use one method to get nearby stars, use a new method for further away stars which depends on our first measurements of nearby stars, then yet another method at further distances, and so on. The first method astronomers use to measure distances to stars is called parallax. If you hold your finger in front of your face and close one eye and look with the other, then switch eyes, you’ll see your finger seem to “shift ” with respect to more distant objects behind it. The effect is called parallax. Astronomers can measure parallax by measuring the position of a nearby star very carefully with respect to more distant stars behind it, then measuring tho
