What is the most accurate way to determine the distance to a nearby star?

Question

Owen Atkinson · Accepted Answer

It's called "parallax". Basically you look at how much the star appears to move in the sky as a result of the earth actually moving on its orbit aroun the sun; the more the star seems to move the closer it is.

In order to use parallax, you first need to observe a tree growing directly on the other side of the road. Then, you measure the angle to the tree with respect to the direction straight down the sidewalk, and walk a certain distance down the sidewalk before measuring the angle again. By combining your measured angles with the distance you walked, you can create a triangle and use that to calculate the width of the road geometrically. If you sit on Earth and allow it to orbit the Sun, you can "walk" around a circle with a diameter of 186 million miles, which is a large enough base for astronomers to make their measurements. However, walking a few steps is not helpful when measuring distances to stars.

Lydia Allen · Answer

undefined The most precise method of calculating the distance to a nearby star is to use the parallax method, specifically trigonometric parallax, which measures the apparent shift in the star's position as seen from Earth at different times of the year. This method is based on the fact that the nearby star will appear to shift slightly against the background of more distant stars as Earth orbits the Sun; astronomers can use trigonometry to calculate the distance to the star by measuring this shift and knowing the baseline distance between the Earth at different points in its orbit.