spaceSpace and PhysicsspaceAstronomy

Amateur Astronomer Has Discovered A Moon Of Jupiter For The First Time


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockJul 26 2021, 12:01 UTC
Majestic Jupiter

Majestic Jupiter. Image Credit: NASA, ESA, A. Simon (Goddard Space Flight Center), and M.H. Wong (University of California, Berkeley)

Kai Ly is an amateur astronomer with a fantastic record. They not only found four lost moons of Jupiter, but they have also become the first amateur to discover a brand spanking new one. Thanks to this find, the biggest planet in the solar system has a whopping 80 known moons orbiting around it.

First things first! How do you lose several moons? Well, it is not carelessness. Many of these moons are small, faint, and orbit the planet far away. Their orbits are tracked for a while but limited observations put major uncertainty onto their celestial path, so after a while, astronomers can no longer find them where they should be.


With a fair amount of hard work and patience, Ly went through years of observations of Jupiter, tracking down where some of these missing moons should be. They were able to find observations from four of them and have now found a brand new one.

EJc0061 = S/2003 J 24, as it is currently known until a new designation has been approved, was tracked by Ly over 76 observations spanning 5,575 days. The moon orbits Jupiter every 694 days going the other way compared to the rotation of the planet, a motion known as retrograde. Many of the most distant moons move like that.

“I'm proud to say that this is the first planetary moon discovered by an amateur astronomer! Other than that, there really isn't anything remarkable about this Jovian moon—it's just a typical member of the retrograde Carme group,” Ly said in a communication on the Minor Planet Mailing List board.

The data that set Ly on this discovery comes from the 3.6-meter (11.8-foot) Canada-France-Hawaii Telescope (CFHT) from 2003. They then found the moon in other data from CFHT, the Subaru Telescope, and the Cerro Tololo Inter-American Observatory that allowed them to track its motion and tighten the constraints on its orbit all the way to 2018.


In their initial analysis, Ly reports also the detection of other two candidate moons but two of them were “unrecoverable either due to their faintness or were obstructed by CCD gaps in subsequent observations.” It is possible that there are more moons out there just waiting to be discovered.

Of the now 80 moons, only 53 have official names, with the other 27 awaiting to be called something more interesting than a string of letters and numbers. A few years ago, researchers asked for the public's help in naming (according to the strict criteria of naming space objects) five of them, and the public put forward some excellent names. The winning ones were Eupheme, Philophrosyne, Eirene, Ersa, and Pandia.

[h/t: Sky & Telescope]

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