The Catholic Message Board

Obi-Wan Kenobi wrote: ↑Thu Oct 16, 2025 5:16 pm I know. I don't think Eris is what they had in mind with the phrase "neighborhood," although it's not entirely clear what they did have in mind. https://en.wikipedia.org/wiki/Clearing_ ... ghbourhood

Stern, the principal investigator of the New Horizons mission to Pluto, disagreed with the reclassification of Pluto on the basis of its inability to clear a neighbourhood. He argued that the IAU's wording is vague, and that — like Pluto — Earth, Mars, Jupiter and Neptune have not cleared their orbital neighbourhoods either. Earth co-orbits with 10,000 near-Earth asteroids (NEAs), and Jupiter has 100,000 trojans in its orbital path. "If Neptune had cleared its zone, Pluto wouldn't be there", he said.

And that is why many astronomers reject the 2006 declaration, and they note that the IAU represents only 5% of working astronomers, so it is a fair question why they think they have the authority to claim to represent the consensus of astronomers.

Doom wrote: ↑Thu Oct 16, 2025 4:05 pm According to the 2006 definition, a planet has to be "dominant in its immediate neighborhood", dominant meaning "the biggest object", which Pluto is not because Eris is bigger. But the other 8 planets absolutely are the biggest thing in their immediate neighborhood.

Some complain that this part of the definition was added specifically for the purpose of excluding Pluto from the planets. This is true, the IAU had spent years trying to come up with some reason why Pluto would be different from the 8 planets.

So, if Eris is bigger, therefore it is the 9th planet.

Oops.

They didn't go there because..........reasons.

They didn't go there because Eris is basically a large asteroid

Obi-Wan Kenobi wrote: ↑Thu Oct 16, 2025 11:27 am Pluto's biggest moon is Charon, which is about half the diameter and 1/8 the mass of Pluto. It's big enough that both bodies rotate around a point outside of Pluto, but Charon isn't bigger.

This is true for all bodies. They orbit about a barycenter, a common center of mass. As it turns out the barycenter for us is 3/4 of the way from the center of the earth. Because Pluto is not all that big compared with Charon, the barycenter is outside the diameter.

The Sun/Jupiter barycenter is slightly outside the Sun.

Hey, I like the respect for Nuevo Mexico part of this. Can we focus on that a bit more? ¿Podemos?

Oh, and it seems pretty clear that the grey area for planets is pretty wide. BTW, a person who is a member of our local astronomy club who was at the conference which unplaneted Pluto stated that the vote for the status change was held very late on the last day of the conference -- when many attendees were gone. He opined that the Anti-Pluto activists deliberately scheduled and then delayed the vote until that time as the majority of the attendees were PPP (pro-Pluto planet).

The Bolsheviks would have been proud.

No podemos. We're all about barycenters now.

Obi-Wan Kenobi wrote: ↑Tue Nov 11, 2025 9:34 pm We're all about barycenters now.

Does that make me an influencer?

Obi-Wan Kenobi wrote: ↑Tue Nov 11, 2025 9:34 pm No podemos. We're all about barycenters now.

Nice way of sneaking in a reference to Center of Mass.

I'm trying to understand what a barycenter is.
Is it like saying that if a mass at one end of a fulcrum is greater than at the other end, then the fulcrum needs to be moved closer to the larger mass?

if, at rest, you don't want it to flop over on the bigger mass side. If rotating, if you don't want it to fly off in all directions at once.

Riverboat wrote: ↑Tue Nov 11, 2025 10:50 pm

Obi-Wan Kenobi wrote: ↑Tue Nov 11, 2025 9:34 pm We're all about barycenters now.

Does that make me an influencer?

Sure!

anawim wrote: ↑Wed Nov 12, 2025 1:32 pm I'm trying to understand what a barycenter is.
Is it like saying that if a mass at one end of a fulcrum is greater than at the other end, then the fulcrum needs to be moved closer to the larger mass?

Pretty much the same idea, yes.

Obi-Wan Kenobi wrote: ↑Tue Nov 11, 2025 9:34 pm No podemos. We're all about barycenters now.

So hard to lose weight after 50

peregrinator wrote: ↑Sat Nov 22, 2025 7:29 am

Obi-Wan Kenobi wrote: ↑Tue Nov 11, 2025 9:34 pm No podemos. We're all about barycenters now.

So hard to lose weight after 50