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Jupiter Now Has 69 Moons
The planet Jupiter is a beast: Three-hundred-and-seventeen times the mass of the Earth, mostly made of metallic hydrogen, and at the center of an astonishing collective of orbiting natural bodies.
In fact, Jupiter's satellites form a shrunken version of a full planetary system: from the tightly bound larger Galilean moons (orbiting in their Laplacian mean-motion resonances, akin to places like TRAPPIST-1) to the remarkable array of smaller moonlets that encircle this world out to more than 30 million kilometers.
These bodies circle Jupiter in anywhere from about 7 hours to an astonishing 1,000 days.
Until recently the cataloged satellites totaled 67 in number. But only the innermost 15 of these orbit Jupiter in a prograde sense (in the direction of the planet's spin). The rest are retrograde, and are likely captured objects - other pieces of the solar system's solid inventory that strayed into Jupiter's gravitational grasp.
That population of outer moons is mostly small stuff, only a few are 20-60 kilometers in diameter, most are barely 1-2 kilometers in size, and increasingly difficult to spot.
Now astronomers Scott Sheppard, David Tholen, and Chadwick Trujillo have added two more; bringing Jupiter's moon count to 69.
The planet Jupiter is a beast: Three-hundred-and-seventeen times the mass of the Earth, mostly made of metallic hydrogen, and at the center of an astonishing collective of orbiting natural bodies.
In fact, Jupiter's satellites form a shrunken version of a full planetary system: from the tightly bound larger Galilean moons (orbiting in their Laplacian mean-motion resonances, akin to places like TRAPPIST-1) to the remarkable array of smaller moonlets that encircle this world out to more than 30 million kilometers.
These bodies circle Jupiter in anywhere from about 7 hours to an astonishing 1,000 days.
Until recently the cataloged satellites totaled 67 in number. But only the innermost 15 of these orbit Jupiter in a prograde sense (in the direction of the planet's spin). The rest are retrograde, and are likely captured objects - other pieces of the solar system's solid inventory that strayed into Jupiter's gravitational grasp.
That population of outer moons is mostly small stuff, only a few are 20-60 kilometers in diameter, most are barely 1-2 kilometers in size, and increasingly difficult to spot.
Now astronomers Scott Sheppard, David Tholen, and Chadwick Trujillo have added two more; bringing Jupiter's moon count to 69.
