The farthest star

Have you ever stood on a bit of land where you could climb no higher, or go no farther in the direction you were travelling? I often wonder when I view the sky how far I can see in a given direction. Using only our eyes, looking toward Sagittarius we run into the dense gas and dust of our galaxy’s plane before we reach its centre, around 26,000 light-years away. Turning to Andromeda and its iconic galaxy, we have 2.5 million light-years to M31, and in Centaurus it’s about five times farther to the brightest radio galaxy, Centaurus A (NGC 5128), possibly the most distant object visible to the naked eye. With binoculars or a telescope the exercise becomes more complex.

Choosing our targets

I recently wondered which is the farthest star that can be seen. It’s not a trivial problem, as many factors, such as experience, site conditions and weather influence the answer. Assuming a clear view to