APOD and General Astronomy Discussion Forum
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This type of star system includes a very dense, small member (the white dwarf) and a much larger but less dense member that has begun to swell up and only tenuously holds on to its outer atmosphere (a red giant). The situation is... quite different!Pianosorplanets wrote:Can't think of any mechanism for one body to "siphon off" atmosphere? Maybe I can help. How about a double star system with a white dwarf?
A cheer for Chris! It's fun and interesting to learn the intricate details of how the universe works. Thanks to Chris, just the other day I learned the true solar system escape velocity at Jupiter's orbit. But picking nits just because you can doesn't get us anywhere and getting nowhere does get dull after a while (anybody who's spent a week in the hospital knows how that feels). It's nice to have a grounding force (kind of like gravity) to keep one's thinking and one's speculation in the realms of that which is either productive, build's friendships or is good for a nice chuckle once and again.Chris Peterson wrote:No such agreement is likely, because none of these terms are well enough defined to eliminate ambiguity. Both are reasonably called planets (in which case they are a binary system), Pluto is reasonably called a planet and Charon a moon. It really depends on context. And frankly, it's not all that important which terms we use.
Yes, of course it is. Sorry, I was being a bit glib. Hence my use of the word "Microcosm". More to the point is what space gases might the system pass through as a group and which bodies can and can't hang onto some of it. It seems more likely that that is the mechanism for a commonality in any atmosphere discovered than the chance of Charon actually drafting gas off of Pluto. Quite the long shot, no?geckzilla wrote:This type of star system includes a very dense, small member (the white dwarf) and a much larger but less dense member that has begun to swell up and only tenuously holds on to its outer atmosphere (a red giant). The situation is... quite different!Pianosorplanets wrote:Can't think of any mechanism for one body to "siphon off" atmosphere? Maybe I can help. How about a double star system with a white dwarf?
Meteors, Oort cloud objects, binary stars and space dust no doubt find themselves in a dance with a nearby object. We can't name them all "planets" just because their center of gravity is outside the physical form of either object.Milky Waster wrote:As I understand it, the term "binary planets" is used when two bodies orbit a point outside either of their masses which is what I understand Pluto and Charon do. Students everywhere will no doubt be pleased to learn that it doesn't matter what terms they use. "Everyone gets 100%," said Alison Tudorland.
Nope, not even close. Material transfers between the components of a close binary star system because the two objects overlap- in particular, the surface of one extends beyond the apex of the Roche lobe, allowing transfer across the L1 point. This is only possible with fluid bodies. Rigid bodies can't possibly be that close without tidally disrupting each other.Pianosorplanets wrote:Can't think of any mechanism for one body to "siphon off" atmosphere? Maybe I can help. How about a double star system with a white dwarf?Chris Peterson wrote: I can't think of any mechanism for one body to "siphon off" the atmosphere of the other. No gas molecule on Pluto feels any net gravitational force except downwards, towards the center of Pluto.
Actually, students need to understand that some lines make no sense. It doesn't matter what we call planets. It doesn't matter if there are 9 of them or 1000 of them. Nobody really cares. The definition isn't very important. Whether something on Earth is a "hill" or a "mountain" doesn't interest geologists. What's interesting is if some bump is the product of uplift, or deposition, or extrusion. "Hill" and "mountain" are more useful as informal designations understood in context. The same is true for "planet", which is, in fact, how most astronomers use the word in practice. We care about the physical nature of these bodies, and classify them based on that (terrestrial, gas giant). We care about their origin and formation history, and classify them based on that. We care about their orbital dynamics, and classify them based on that. Lots of categories. Those are what matter, not the loose designation that we can safely use without concern over technicalities.Pianosorplanets wrote:Students need not be told it doesn't matter but be told just how grand the scheme of things really is and that we have to draw the line someplace.
Right, as noted previously Charon can intercept material that diffuses from Pluto. But at that distance, I doubt we're going to have much blown off by the Sun. The atmosphere is already close to a vacuum. Charon's gravity isn't going to retain any stray gas molecules that come its way, so we'd be looking at some sort of adhesion process, I'd think, if anything. But Charon itself is icy. I wouldn't be surprised if it also has an extremely tenuous atmosphere- it may be outgasing more than it receives from Pluto.BMAONE23 wrote:Siphoning isn't required to transfer atmospheric gasses between the two bodies. Solar winds strip some atmospheric gasses and blows them back away from Pluto in a type of tail pointing away from the sun. In just 62 years Charon's orbit will be passing between the sun and Pluto so that, out of every 201 hour orbital period, 24 hours will be spent in the atmospheric tail caused by the solar winds
Committees tend to be very good at that.geckzilla wrote:It doesn't matter, at least, until you get a committee on the job, it seems.
https://en.wikipedia.org/wiki/Parkinson ... triviality
Well, what do you think of the possibility that an atmosphere might contribute to a reddish color of an outer solar system planet or moon? If Charon itself has an atmosphere, that might just possibly explain this planet/minor planet/moon's slightly reddish hue near its dark pole.Chris Peterson wrote:Right, as noted previously Charon can intercept material that diffuses from Pluto. But at that distance, I doubt we're going to have much blown off by the Sun. The atmosphere is already close to a vacuum. Charon's gravity isn't going to retain any stray gas molecules that come its way, so we'd be looking at some sort of adhesion process, I'd think, if anything. But Charon itself is icy. I wouldn't be surprised if it also has an extremely tenuous atmosphere- it may be outgasing more than it receives from Pluto.BMAONE23 wrote:Siphoning isn't required to transfer atmospheric gasses between the two bodies. Solar winds strip some atmospheric gasses and blows them back away from Pluto in a type of tail pointing away from the sun. In just 62 years Charon's orbit will be passing between the sun and Pluto so that, out of every 201 hour orbital period, 24 hours will be spent in the atmospheric tail caused by the solar winds
I generally avoid speculation in the absence of evidence. We see color and surface structure on cold, icy, airless (or nearly airless) bodies caused by sublimation, by internal outgasing, by space weather, by impacts. If Pluto has some sort of internal activity of unknown origin, Charon may, as well.Ann wrote:Well, what do you think of the possibility that an atmosphere might contribute to a reddish color of an outer solar system planet or moon? If Charon itself has an atmosphere, that might just possibly explain this planet/minor planet/moon's slightly reddish hue near its dark pole.
Both 1/10th the size and 1/1000th the size are somewhat ambiguous, but I wouldn't go so far as to say misleading.Bradford wrote:It's misleading and confusing to say "1/10th the size of planet Earth."
You should say 1/10 the diameter, which is closer to 1/1000 the size.
Well that is not bad news... Austell is only a Hercules's stone's throw from Canton! In cosmic resolution, that's as good as dead on.Craine wrote:Not Canton. Austell, GA is.emc wrote: So Canton, GA isn’t the center of the universe!? Dang again! Now I feel even less important. If I were any lower I would be inside a black hole...
Well Ed, I guess that makes you the slightly off center of the universeemc wrote:Well that is not bad news... Austell is only a Hercules's stone's throw from Canton! In cosmic resolution, that's as good as dead on.Craine wrote:Not Canton. Austell, GA is.emc wrote: So Canton, GA isn’t the center of the universe!? Dang again! Now I feel even less important. If I were any lower I would be inside a black hole...
BMAONE23 wrote:Well Ed, I guess that makes you the slightly off center of the universe
ta152h0 wrote:
Now that NH is out there in the vast ocean of nothingness,
are the cameras taking images of the nothingness ahead of
the spacecract [sic] and maybe catch something simply by golly ?
