How many planets?

[Karlos]

I thought Charon was Pluto's satellite?

[Karlos]

bloodline wrote:

Karlos wrote:
I thought Charon was Pluto's satellite?

If this proposal goes ahead, they will probably become binary planets.

Ok, so what about our moon? Not to mention those of the gas giants?

[Karlos]

blobrana wrote:
Hum,
our moon (under the new rules) would sill be a moon, because the centre of its orbit lies within the Earth. This would be the same as the gas giants moons.

Pluto - Charon  centre of gravity is in the space between them, so they become a binary/double planet.

Ah, so the mass/size/dimension alone are not sufficient for planet labelling, it depends also on where the barycentre lies. Makes sense I suppose.

[Karlos]

nadoom wrote:

Incidentally, with the introduction of new planets we also have to also expand the zodiac. The planet Ceres this week is in the constellation Piscis Australis at about magnitude of 7.62 (at close approach).

its all bollocks any way but wouldnt that mean that all the previous predictions were incorrect?

They probably had to rejig it all anyway when pluto was discovered ;-)

[Karlos]

Surely Pluto ought to be right at home in the planetory "Mickey Mouse" category :-)



*fetches coat*

[Karlos]

Vincent wrote:

@Karlos
Hmmm, starting to post some groaners again eh? ;-)

Moi?

*blink*

[Karlos]

Agafaster wrote:

There is a problem with the definition: 'must have cleared its orbital neighbourhood of other objects' this is done by either swallowing up these objects, or ejecting to another part of the solar system - this falls down when we consider that the earth, mars and indeed Jupiter have objects in their Trojan positions... ie: around the L4 and L5 Lagrange Points. does this now mean these 3 are not planets ?!

Yeah, Jupiter's trojan clusters aren't exactly small either.

[Karlos]

Our moon isn't as large as Ganymede, Callisto, Titan or Io, so it's far from being the largest.

[Karlos]

Venus has the highest atmospheric pressure for any rocky planet. Atmospheric pressure is a somewhat vague concept when applied to gas giants such as Jupiter and Saturn as their atmospheres increase in density as you descend into them until you eventually end up in a layer where the pressure is so immense that the hydrogen has been crushed into a metallic phase. There's no distinct phase change boundary that represents any surface you could land on.

[Karlos]

I dare say its possible to take frozen hydrogen and compress the hell out of it in some very high pressure extrusion type systems (the sort that can fluidize cold steel) but I expect it would stop a long way short of making MH. The sort of pressure needed to make metallic hydrogen would surely have an adverse effect on whatever material you were trying to crush it with.

[Karlos]

@Dandy

I studied chemistry to postgraduate level so phase diagrams are no stranger :-)

I think you are thinking of Helium. Hydrogen's melting point is at 14K and the solid phase is well characterised. Helium, under 1 atmosphere pressure is still liquid as close as anybody has ever gotten to absolute zero (a temperature which is basically impossible to achieve in reality). Helium will solidify under 1.5K if you subject it to at least 26 atmospheres. Below about 4K at normal pressure, Helium (at least He4) switches to it's superfluid phase, which is a highly interesting state where the viscosity of the liquid effectively vanishes and the thermal conductivity becomes immense. It'll creep over any surface and find it's own level within any enclosed space, regardless of the topology. The thermal conductivity means you can't boil it, for example, the heat is dispersed so quickly through it that it simply evaporates to a gas phase.

Crazy stuff.

Going back to hydrogen, under enough pressure and temperature it becomes metallic, and may even be superconducting.

[Karlos]

@Dandy

As far as I understood, they did make it, over the duration of the compression experiment (250ns).

Putting it in a jar, however is an entirely different proposition. The pressure required to keep it metallic is far beyond current material sciences' ability to produce a container for.

[Karlos]

I don't expect a large diamond to exist in jupiter's core. A very large mass of heavily compressed iron, surrounded by a rock mantle up to several earth radii, then atmosphere all the way out, proceeding from metallic hydrogen (sustaining immense electric currents that power the magnetosphere) through a normal liquid phase and eventually gaseous, without any well defined boundaries between each.

[Karlos]

Trust me, if you believe in quantum mechanics at all, electron 'orbits' within atoms are about as different from planetary orbits as it is possible to get ;-) You simply cant apply macroscopic scale physics to the microscopic (as in atom scale) world, it simply breaks. It has been said that macroscopic physics is an approximation of quantum mechanics for where the 'uncertainty' limit is zero, rather than [d]h[/d]/2PI...

There's no real mystery about planetary orbts. Gravity is holding neptune in orbit. The sun's gravitational influence extends a hell of a lot further than that, too. Gravity as 'matter' is an explored idea, do a search for 'graviton' particles.

Regarding diamond, it's a very poor conductor. However, if you dope it with boron, nitrogen or similar atoms you can make semiconductors from it. Diamond has very good thermal conductivity, making it a very good future substrate, though it's expensive to make at the moment.

Having said that, carbon under billions of atmospheres of pressure and at tens of thousands of degrees kelvin, who knows what properties it would have?

[Karlos]

Hyperspeed wrote:

And while I'm off on a tangent here - can anyone explain if our moon, if artificially provided with one, could retain a very thin atmosphere (enough for humans to be able to breathe)?

No. First of all, RMS speed of gaseous nitrogen/oxygen molecules at standard temperatures are above the moon's escape velocity. Secondly theres' no decent magnetic field around the moon which means it takes the full brunt of the solar wind which would rapidly strip away any atmosphere it managed to keep hold of.

It was suggested that atom bombs could be used to melt the ice on Mars to speedily provide the planet with an atmosphere - how long would artificial atmosphere generation take using today's technology and could it be applied to Ozone regeneration on our own planet?

No. The idea on mars is to release the frozen CO2 in the caps, thickening the atmosphere, which is mostly CO2. As much as 1/3 of the atmosphere freezes out into the caps during Mars' winter.

Dropping nukes all over our ice caps would do nothing but make our planet even more screwed up than we managed so far. I suspect if it had any effect on ozone at all, it would deplete it.