1. Neptune’s tiny moon Naiad was first discovered by Voyager during a fly by in September 1989.
It looked like this. Neptune is two million times brighter than the moon, so it wasn’t the easiest thing to spot.
2. Now, it’s been rediscovered in some data collected by the Hubble Space Telescope. It’s circled in the image below.
Seeing the moon from Earth is equivalent to trying to see something the width of a human hair from 50 feet away, says Dr Mark Showalter, a senior research scientist at the SETI Institute in Mountain View, California.
Naiad’s orbit of Neptune takes seven hours and six minutes, but is slowly decaying thanks to the pull of the planet. It might eventually crash into Neptune’s atmosphere or be torn apart and form a planetary ring.
The new image shows this decaying process is moving faster than anticipated, as the moon wasn’t where scientists expected it to be when the data was taken. But more observations will be needed to work out why this is the case.