are these moons visible from earth?
Yes through a telescope
Galilean moons
The Galilean moons were observed in either 1609 or 1610 when Galileo made improvements to his telescope,
io and europa the inner two of jupiter's four largest moons They include also Ganymede, and Callisto what are these four moons collectively known as? The Galilean moons who discovered them? Galileo Galilei
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Galilean moons [SEP] Introduction
The three inner moons—Io, Europa, and Ganymede—are in a 4:2:1 orbital resonance with each other. While the Galilean moons are spherical, all of Jupiter's much smaller remaining moons have irregular forms because of their weaker self-gravitation. The Galilean moons were observed in either 1609 or 1610 when Galileo made improvements to his telescope, which enabled him to observe celestial bodies more distinctly than ever. Galileo's observations showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye. The discovery of celestial bodies orbiting something other than Earth dealt a serious blow to the then-accepted Ptolemaic world system, a geocentric theory in which everything orbits around Earth.