Corey S PowellMar 17

Astronomers have discovered 11 more moons around Saturn, bringing its total to 285--by far the most of any planet in the solar system.

The true number may be unknowable, if you count every ring particle as its own little moon.

https://minorplanetcenter.net/mpec/K26/K26F14.html #space #science #nature #math

Show threadStarkRG
@coreyspowell Yeah, I think we might need a scientifically useful definition of a moon to go with the currently scientifically useless definition of a planet.
Mar 17 at 3:03pmWeb
Show threadDavid W. Jones6d ago
@StarkRG @coreyspowell PLUTO IS A PLANET. Now get off my hill.
Show threadStarkRG6d ago
@dancingtreefrog @coreyspowell I honestly don't care whether the definition include Pluto, I think it probably should, but what I really care about is that it be a *useful* definition, not one mired in legacy. The existing definition is both too narrow (it doesn't include rogue planets or planets orbiting other stars) and too broad (gas giants should absolutely not be in the same category as rocky planets, and ice giants should probably be considered a different category from normal gas giants).
Show threadStarkRG6d ago
@dancingtreefrog @coreyspowell Pluto, Titan, and even Ceres have more in common with Earth than it does with Jupiter or Neptune. Maybe stop using the word "planet" entirely, and use "world" for things you could theoretically go to and walk around on without accidentally reaching escape velocity. World is a perfectly cromulent word and does the job of putting in our mind the idea of a place we could go and exist. Even with floating habitats, Jupiter is different enough to not really be a world.
Show threadDavid W. Jones6d ago

@StarkRG @coreyspowell I agree, although probably many people think of "world" as one that has life.

Also: what about dual planets orbiting each other, or near-duals like the Earth-Moon system?

Show threadStarkRG6d ago
@dancingtreefrog @coreyspowell I dunno, when astronauts walked on the Moon, they often remarked that it was a world with it's own stark beauty. Looking at pictures of the surface of Mars, Titan or Venus always make me think "world." Even if the environment would kill us instantly, we can imagine walking around there. Gas and ice giants much less so, though more than stars. Large enough asteroids and comets could be worlds too. Too small and they're just rocks, even if they're mountain-sized.
Show threadDavid W. Jones3d ago
@StarkRG @coreyspowell I think maybe the concept or feeling of "world" is built directly on personal experience or indirectly on learning about someone else's personal experience?
Show threadStarkRG3d ago
@dancingtreefrog @coreyspowell Is that any different from other words and concepts?
Show threadDavid W. Jones2d ago
@StarkRG
Probably not. Although someone such as a child raised on a "mountain-sized rock" might think of it as a world while an adult might see it as a rock.
@coreyspowell
Show threadDavid W. Jones6d ago

@StarkRG @coreyspowell I agree that rogue planets and planets orbiting other stars should be included. At least categorize them as planets even if we can't specifically classify one as rocky/ice/giant.

I still wonder if there aren't cores of rocky planets hiding within gas giants and ice giants.

Is the difference between gas and ice planet simply their distance from their star?

Show threadStarkRG6d ago
@dancingtreefrog @coreyspowell I think the consensus among astrophysicists is shifting away from Jupiter having a rocky core. I'm not sure about Saturn. But even if they did, the rocky core wouldn't be anything like an actual rocky planet, it would be more like our own solid metal core, pretty much perfectly spherical.