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Astronomers Discover 12 New Moons Orbiting Jupiter - One on Collision Course With the Others (theguardian.com)
One of a dozen new moons discovered around Jupiter is circling the planet on a suicide orbit that will inevitably lead to its violent destruction, astronomers say. From a report: Researchers in the US stumbled upon the new moons while hunting for a mysterious ninth planet that is postulated to lurk far beyond the orbit of Neptune, the most distant planet in the solar system. The team first glimpsed the moons in March last year from the Cerro Tololo Inter-American Observatory in Chile, but needed more than a year to confirm that the bodies were locked in orbit around the gas giant. "It was a long process," said Scott Sheppard, who led the effort at the Carnegie Institution for Science in Washington DC. Jupiter, the largest planet in the solar system, was hardly short of moons before the latest findings. The fresh haul of natural satellites brings the total number of Jovian moons to 79, more than are known to circle any other planet in our cosmic neighbourhood. A head-on collision between two Jovian moons would create a crash so large it would be visible from earth, astronomers said.
If we can demote planets (Ceres too was once counted as a planet), it is time to tighten up the definition of moon.
Jupiter has four moons, and a bunch of rocks making up a 1/300 of one percent of the total mass in orbit.
And Mars, sorry.
The expression "on collision course" should be reserved for an event like this, where the moment of the collision can be calculated. The current title is click bait.
If we can demote planets (Ceres too was once counted as a planet), it is time to tighten up the definition of moon.
Exactly what do you think is loose about the definition? I'm not opposed to the idea but what do you find confusing or misleading about the current definition?
We should be redefining things with some regularity as we learn more. We probably should have different categories for different types of planets. Jupiter is a far different sort of object than Earth. Pluto and Eris probably are a separate category of object as well. Call them a planet if you like (I don't care) but then you have to say what kind of planet. Otherwise it's like saying a lion and your house cat are the same thing when they clearly are not.
Jupiter has four moons, and a bunch of rocks making up a 1/300 of one percent of the total mass in orbit. And Mars, sorry.
If my count is right at least 13 of Jupiter's moons are larger than either of the moons of Mars. Relative size definitions don't really make much sense. Absolute size definitions seem to be pretty arbitrary. How would you propose changing the definition to account for something not currently accounted for?