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View Full Version : Jupiter - 79 moons and counting, and counting, and counting



Roger E. Moore
2018-Jul-17, 07:32 PM
https://www.npr.org/2018/07/17/629396121/galileo-would-be-stunned-jupiter-now-has-79-moons

Point your telescope in a certain direction "just for the heck of it" and you might find another bucket full of moons.

parallaxicality
2018-Jul-18, 10:10 AM
Isn't it time we stopped calling these things "moons"? Wouldn't "captured objects" be more accurate?

Swift
2018-Jul-18, 01:51 PM
I like the suggestion in the article of "mini-moon".

DonM435
2018-Jul-19, 01:27 AM
For most of my younger life, there was but one Moon, and you were supposed to call all the other secondary thingies "satellites."

It seems to have changed with relative swiftness. I wonder just how.

dtilque
2018-Jul-19, 01:46 AM
It's not wrong to call them satellites, although you may want to modify it and call them "natural satellites" to distinguish them from artificial ones.

When I was a kid, Jupiter only had 12 satellites total. Now they find that many in one swoop.

George
2018-Jul-19, 02:26 PM
It's not wrong to call them satellites, although you may want to modify it and call them "natural satellites" to distinguish them from artificial ones. Yes, satellites are often considered as an artificial object, but saying "natural satellites" is a mouthful when used for so many objects that are smaller than our sweet and simple "Moon". Ever since I went outside as a kid to see if I could see the Sputnik satellite passing overhead, "satellite" would always be especially unnatural, so "natural satellite" for me is an oxymoron.:) I too agree with "mini-moons" as it says it nicely and with alliteration. There is also the alliterative hint of "meme" in there too, which is fitting in some respects.

glappkaeft
2018-Jul-19, 02:46 PM
I like the suggestion in the article of "mini-moon".

Moonlet is already in use. So is "mini-moon" but it means a short (a few days long) honey moon.

DonM435
2018-Jul-19, 04:22 PM
Morb. Mountain-in-orbit.

Roger E. Moore
2018-Jul-20, 02:31 PM
Perhaps we can borrow a system used in a recent paper, "PROBABILISTIC FORECASTING OF THE MASSES AND RADII OF OTHER WORLDS", by Jingjing Chen & David Kipping.

https://arxiv.org/pdf/1603.08614.pdf

In determining the smallest-sized "terrestrial" planet to use in establishing a mass-radius table for exoplanets, they said: "A natural lower bound is an object with sufficient mass to achieve hydrostatic equilibrium leading to a nearly spherical shape and thus a well-defined radius (a planemo), which would encompass dwarf planets." They later developed a boundary between: "...the most massive body which is known to not be in hydrostatic equilibrium (Iapetus; 1.8 x 10^21 kg; Sheppard 2016) and the least massive body confirmed to be in hydrostatic equilibrium (Rhea; 2.3 x 10^21 kg; Sheppard 2016). This leads us to adopt a boundary condition of M > 2 x 10^21 kg for all objects considered in this work."

Only the four Galilean satellites, then, are truly "moons" of Jupiter. Everything else from Himalia on down is just a Big Rock, like SF writers of old once called them (e.g., Jack Williamson, "rock rats" referring to asteroid miners, c. 1950). Everything less than 1 km across down to 1 meter across is a Rock, and anything smaller is Debris.

We will ignore the term "irregular natural satellite", as it refers to something a little different.

https://en.wikipedia.org/wiki/Irregular_moon