In 1974, NASA's Pioneer 11 spacecraft viewed Jupiter from above its north pole. Image credit: NASA Ames

One might believe something as monumental as discovering a new moon would be the result of efforts from professional astronomers. However, an amateur by the name of Kai Ly discovered a new moon for the planet Jupiter on June 30th. Ly was scanning old datasets from 2003 when it was identified.

'I’m proud to say that this is the first planetary moon discovered by an amateur astronomer,' Ly tells Sky and Telescope. This follows Ly's identification and recovery of 5 lost Jovian moons, including Valetudo, Ersa, and Pandia, using the public archive of images available online.

Jupiter currently has around 80 moons, with new ones being discovered periodically. However, no one expected an amateur to add to this growing list. The data Ly examined was captured with a 3.6-meter Canada-France-Hawaii Telescope (CFHT). David Jewitt and Scott Sheppard of University of Hawai‘i led a group that discovered 23 new moons. Ly suspected more undiscovered new moons were hiding out in the dataset and got to work.

An image of Ganymede, one of Jupiter's moons and the largest in our Solar System, obtained by the JunoCam imager during Juno’s June 7, 2021, flyby of the icy moon. Image credits: https://www.jpl.nasa.gov/news/see-the-first-images-nasas-juno-took-as-it-sailed-by-ganymede

Ly started examining images taken in February, 2003, in early June of this year. While they initially tracked 3 potential moons, there wasn't enough data to recover 2 of them. They were able to confirm that the third, designated EJc0061, was bound to Jupiter. In all 76 observations gathered from an observation period spanning 15.26 years was enough for Ly to conclude that the orbit of this new moon was secured for decades.

This new moon, discovered by Ly, may have company in the coming years. Last year, Edward Ashton, Matthew Beaudoin, and Brett J. Gladman spotted around 4 dozen objects, as small as 800 meters, in Jupiter's orbit. While they didn't prove these objects were Jovian moons, the group suggests that there is a possibility of up to 600 satellites. The development of more sophisticated telescopes in the coming years will help astronomers confirm these possibilities.

Software and services, including Find_Orb orbit, Aladin Sky Atlas and the Canadian Astronomical Data Center's Solar System Object Image Search, are available to anyone including amateur astronomers to make these types of discoveries.