When it will definitely did, Galileo was amazed to see Jupiter wasn’t alone. There have been a number of small, pinprick stars flanking it — two on one aspect, one on the opposite — all bathed within the brilliant planet’s metallic glare. Like several good observer, Galileo recorded what he noticed, contemplated on it for some time, then seemingly swung his telescope to different targets.
However on subsequent clear nights, Galileo returned to Jupiter many times, every time seeing unusual companions near it. Intriguingly, their numbers modified from evening to nighttime, as did their association. On some evenings, as many as 4 companion stars have been seen, organized in pairs on both aspect of Jupiter, or three on one aspect and one on the opposite, and even all 4 on the identical aspect.
There was just one clarification, Galileo surmised: The “companion stars” have been objects going round Jupiter. However that meant that Jupiter didn’t go across the Earth, as everybody had thought, and Earth wasn’t actually the middle of the universe.
The Galilean moons come into focus
4 centuries later, we all know that these factors of sunshine seen fluttering within the eyepiece of Galileo’s telescope have been, in actual fact, the moons Io, Europa, Ganymede, and Callisto — the 4 largest of Jupiter’s prolonged household of moons.
For a few years, Jupiter trailed behind Saturn for the record number of moons. However in January 2023, researchers introduced the invention of a dozen new moons round it. That Brough Jupiter’s total number of moons to 92, sufficient for the king of planets to leapfrog over Saturn ultimately. However of all Jupiter’s many dozens of moons, the 4 found by Galileo nonetheless stay probably the most noticed, in addition to probably the most fascinating. Astronomers and observers alike collectively discuss with these 4 moons because the “Galilean satellites,” or “Galilean moons.”
And at the moment, we all know a lot about every Galilean moon that they’re nearly thought of planets in their very own proper.
