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Bill S.
2003-Jun-24, 06:10 PM
No, not a place where Kryptonians hail from, but literally gigantic planets.

Are they possible? Let me qualify my statement by defining planet as all solid or mostly-solid manner, like the earth, not a gas-giant like Jupiter or Saturn.

So, is it physically possible for a jupiter-sized, all-solid planet to exist?

eburacum45
2003-Jun-24, 06:43 PM
Well, the question is really- 'if there are large rocky planets, how deep will their atmospheres be?'

please correct me if I am wrong, as I am not an astronomer...
Jupiter probably has a rocky core, perhaps 10 times as massive as Earth; if you imagine a rocky planet say 30 Earth Masses, the atmosphere of such a planet would be even thicker- and the planet would b a bigger Jupiter;
with a rocky core a hundred times Earth mass the planet would be a brown dwarf or even a red dwarf... in which case the rocky core would probably be present as mettalicity throughout the gaseous body of the planet, and the core would be actively fusing deuterium or hydrogen.

Now imagine a large gas giant near the star (as at 51 Pegasi)... a 'Hot Jupiter';
the heat from the star can cause a large proportion of the atmosphere to boil off, like a comet-
the Hubble recently discovered such a planet, complete with tail.

so it might be possible that in some systems the rocky cores of old gas giants have been exposed by long evaporation, or even by irregularities in the star itself.
I can imagine such a planet, near a star, stripped of it's gas envelope by superflares from the central star... ten, twenty, times Earth's mass, baked solid by the heat from its irregular sun;
If the star has exploded in a nova or supernova and remains as a white dwarf or other remnant, the hyperplanet core might even be cool enough to walk on and perhaps colonise.

There are many different types of planet up there, and we have not seen or even imagined all the possibilities yet.

The Supreme Canuck
2003-Jun-24, 07:05 PM
Jupiter has a rocky core? I thought it would be liquid due to the heat and pressure, much like Earth's core.

Glom
2003-Jun-24, 08:20 PM
Jupiter has a rocky core? I thought it would be liquid due to the heat and pressure, much like Earth's core.

Quite the reverse. The high pressure increases mp and bp. That's why Jupiter has metallic hydrogen generating its powerful magnetic field. Only under such high pressure could hydrogen be made to become metal. Remember, in mountainous areas, making a cup of tea is difficult because at the lower atmospheric pressure, the boiling point of water is lower.

The Supreme Canuck
2003-Jun-24, 10:34 PM
Hmmm... didn't think that the pressure would be quite that high... guess you learn something new everyday!

Karthesios
2003-Jun-24, 11:05 PM
It's the same kind of heat and pressure that makes Earth's inner core solid.

The Supreme Canuck
2003-Jun-25, 12:31 AM
Really? I thought that was because the denser materials sunk to the centre. Wait a minute... dense doesn't always equal higher melting point... ah nuts. :D

PS: See how my mind works? This explanation may not even make sense to you!

Karthesios
2003-Jun-25, 07:48 AM
Dense = high melting point? Nah. Tell that to someone who works with gold or lead (both melt at pretty low temps)

Mainframes
2003-Jun-25, 09:30 AM
Dense = high melting point? Nah. Tell that to someone who works with gold or lead (both melt at pretty low temps)

Add mercury to that list, liquid at room temperature and damned dense!

Karthesios
2003-Jun-25, 09:55 AM
Add mercury to that list, liquid at room temperature and damned dense!

Cripes, I should've picked that one out...so obvious.

hits self in head repeatedly with stale loaf of bread

The Supreme Canuck
2003-Jun-25, 05:05 PM
Can I borrow the bread? I need a good wack in the head after that one...

Karthesios
2003-Jun-25, 11:07 PM
*tosses bread to The Supreme Canuck

*HEADS UP!!*

Anonymous
2003-Jun-25, 11:23 PM
How about “super-terrestrial”? Any object (composed of mostly silicates) with a mass above ~3 Earth masses. To distinguish such objects from “naked gas giant cores” we’d probably have to slap in a provision that the planet must not possess a Jupiter like atmosphere. Or, indeed, ever possessed such an atmosphere.

Next hurdle….how massive could such an object grow? I don’t doubt that a typical proplyd (proto-planetary-disk) contains hundreds of Earth-masses of dust. The problem is that in most nascent star-systems, accretion is competing with other efficient mechanisms of dust removal. In the pre-T Tauri phase, Frank Shu’s “X-wind” mechanism would be ejecting enormous amounts of dust, perhaps as much as 10% of the available dust. (Which would also provide a neat mechanism for “dumping” angular-momentum)

From here, diagram found near bottom of page for the impatient;

http://www.thecore.nus.edu.sg/natureslaw/unl2203/chanterm.html


Another mechanism for dust removal would the wholesale ejection of planetesimals and embryos through gravitational interaction.

While we’re at it, how many “goners” can a proplyd produce? (proto-planets absorbed by the proto-star)

Then there’s the T Tauri phase with extremely powerful stellar winds to sweep dust from the inner regions of a star system.

On second thought, even with multiple mechanisms absorbing or ejecting the available dust, I can’t find anything which would definitely prohibit super-terrestrial formation. The geological processes of a 10 Earth mass terrestrial would certainly be interesting.

But a 300 Earth mass terrestrial? I cant quite wrap my mind around that one. The good news is that such an object should differ spectroscopically from gas giants. Now, if our ability to detect will just catch up with our imaginations.

Russ
2003-Jun-25, 11:24 PM
I can't remember where I read/heard it but I'd swear that the way Jupeter works is the atmosphere gets more and more dense until the hydrogen turns to metal and then there is no distinction between it and silica based material such as rock. Therefore, while there may be silica/iron/other based core, it would be this unstratified oleo of material indistinguishable from the "atmosphere".

Does anyone know if this is accurate or....what?

freddo
2003-Jun-26, 12:45 AM
Add mercury to that list, liquid at room temperature and damned dense!

Cripes, I should've picked that one out...so obvious.

hits self in head repeatedly with stale loaf of bread

How dense is the bread? What's it's melting point? :lol: :lol: :lol: :lol:

Bill S.
2003-Jun-26, 01:24 AM
How about “super-terrestrial”? Any object (composed of mostly silicates) with a mass above ~3 Earth masses. To distinguish such objects from “naked gas giant cores” we’d probably have to slap in a provision that the planet must not possess a Jupiter like atmosphere. Or, indeed, ever possessed such an atmosphere.


The problem lies in that if such an object formed in a solar system that works somewhat like ours, it would by default have a giant atmospheric layer, yes? I mean, due to the unimaginable gravity of such a "solid" object. Then, by default, that atmosphere would be correspondingly larger...at which point you might well get stellar ignition due to the volumes of H involved (assuming that there was enough H in the system to begin with, which is practically dicated by universal constants...)



Next hurdle….how massive could such an object grow? I don’t doubt that a typical proplyd (proto-planetary-disk) contains hundreds of Earth-masses of dust. The problem is that in most nascent star-systems, accretion is competing with other efficient mechanisms of dust removal. In the pre-T Tauri phase, Frank Shu’s “X-wind” mechanism would be ejecting enormous amounts of dust, perhaps as much as 10% of the available dust. (Which would also provide a neat mechanism for “dumping” angular-momentum)

From here, diagram found near bottom of page for the impatient;

http://www.thecore.nus.edu.sg/natureslaw/unl2203/chanterm.html


Another mechanism for dust removal would the wholesale ejection of planetesimals and embryos through gravitational interaction.

While we’re at it, how many “goners” can a proplyd produce? (proto-planets absorbed by the proto-star)

Then there’s the T Tauri phase with extremely powerful stellar winds to sweep dust from the inner regions of a star system.

On second thought, even with multiple mechanisms absorbing or ejecting the available dust, I can’t find anything which would definitely prohibit super-terrestrial formation. The geological processes of a 10 Earth mass terrestrial would certainly be interesting.


Providing it didn't crush itself, of course. And providing that it didn't have a dense superatmosphere, something I can't concieve. Unless...somehow the superplanet was ejected from the solar system before it had a chance to accrete the soup of hydrogen, methane, and other gases...

A supernova might cause this - it might even help with blowing off the already accumulated atmosphere.



But a 300 Earth mass terrestrial? I cant quite wrap my mind around that one. The good news is that such an object should differ spectroscopically from gas giants. Now, if our ability to detect will just catch up with our imaginations.

Ah, we can hope. Can you imagine the press release on that one? I call dibs!

A "silveyoid" type planet. No, sounds too much like "sillyoid". Hm. Williamoid? Billoid?

Karthesios
2003-Jun-26, 02:28 AM
Add mercury to that list, liquid at room temperature and damned dense!

Cripes, I should've picked that one out...so obvious.

hits self in head repeatedly with stale loaf of bread

How dense is the bread? What's it's melting point? :lol: :lol: :lol: :lol:

We couldn't get conclusive evidence as to the melting point of the bread (it burst into flames at about 450F). We concluded its density to be roughly 0.96 g/cm^3, and its Mohs hardness index to be between 2 and 3. It was one STALE loaf.

The Supreme Canuck
2003-Jun-26, 02:50 AM
Thanks Karthesios.

*WHACK!!!*

eburacum45
2003-Jun-26, 11:45 AM
Heathen wrote
The geological processes of a 10 Earth mass terrestrial would certainly be interesting.

Yes, indeed.
If it contains an Earth-like core, with a similar level of radioactive decay keeping the internal temperature up, the smaller surface area per volume will no doubt cause the crust to have a higher throughput of energy.
In other words, volcanoes, tectonics, earthquakes...

Kaptain K
2003-Jun-26, 12:31 PM
I'm pretty sure that a supermassive terrestrial planet could not form in any normal stellar system. As the mass of the rocky core increases, so does the amount of gaseous atmosphere. In our own system, Mercury has no atmosphere, Mars is somewhat larger and has some atmosphere, the Earth (a lot) and Venus (too much) have plenty of atmosphere. The gas giants have large atmospheres because their large gravity accreted a lot of gas.

zwi
2003-Jun-26, 04:32 PM
Glom said


Remember, in mountainous areas, making a cup of tea is difficult because at the lower atmospheric pressure, the boiling point of water is lower.


Actually the water will boil sooner, but the tea will not be as hot as it should be.

I grew up in Johannesburg South Africa where water boils at 94.5 C. English tea tastes better. In Florida I have to import good teas

Anonymous
2003-Jun-27, 03:45 PM
Quote from Bill S.


“a solar system that works somewhat like ours”


Ah, there’s the rub. I view our solar system as neither rare nor typical. I submit that the apparent glut of massive planets around other stars is probably best explained by our observational bias. In particular, our methods of observation are currently limited to detecting giants rather than little terrestrials (such as Earth).


However, at least a few traits should be ubiquitous. The “snow line” for example. Determined by the temp of the primary and the overall mass and composition of the proplyd (high or low metalicity). A fuzzy boundary pre-ignition which becomes a distinct boundary post-ignition.


http://www.astro.lsa.umich.edu/users/cowley/lecture28/


Of course, the stellocentric distance of the snow line will vary from system to system. The important thing here is that there will be at least two distinct zones of planet building (possibly several) within each star system. . I take as a given that even minute differences in the initial conditions may result in drastic differences in the development of star systems. Specifically, drastic differences in the development of secondary bodies within those systems. (ie hot Jupiters)



“it would by default have a giant atmospheric layer, yes?”


Perhaps. If the object formed beyond the snow line (as our own gas giants apparently did), then yes. I was thinking more of a “true” terrestrial. So, if said object forms inferior to the snow line and after the initiation of T Tauri winds, then no, it would not necessarily possess a giant atmospheric layer. It would be limited to an out-gassed, secondary atmosphere. Depending on how intense the environment is, it may even lose its out-gassed atmosphere over time. (like Mercury)



“Then, by default, that atmosphere would be correspondingly larger...at which point you might well get stellar ignition due to the volumes of H involved (assuming that there was enough H in the system to begin with, which is practically dicated by universal constants...)”


If the object formed beyond the snow line and had a sufficient reservoir of mass to work with, then yes. Let’s see, lower limit for fusors is maybe 18 Jupiter masses and 1 Jupiter mass is around 318 Earth masses……..then…..5,724 Earth masses required for fusion. For clarity, this is not the type of scenario I had in mind. Again, I was thinking of inner system, true terrestrials. (as opposed to gas giants which have migrated in-system, then evaporated, leaving behind their silicate cores)


Quote from Kaptain K.


“I'm pretty sure that a supermassive terrestrial planet could not form in any normal stellar system. As the mass of the rocky core increases, so does the amount of gaseous atmosphere. In our own system, Mercury has no atmosphere, Mars is somewhat larger and has some atmosphere, the Earth (a lot) and Venus (too much) have plenty of atmosphere. The gas giants have large atmospheres because their large gravity accreted a lot of gas.”


Perhaps we should side-step what a normal stellar system is……at least for the time being. I think we’re on the same page. I guess we have to determine upper and lower mass limits first. For the purposes of this thread, let’s say an object of 1 to 3 Earth masses qualifies as “giant terrestrial” and an object of 3 to 10 Earth masses (or higher) qualifies as “super terrestrial”. I’m reluctant to go much higher than 10 E m. (at least until such a thing is actually discovered)


For clarity, let’s double back for a sec.


“As the mass of the rocky core increases, so does the amount of gaseous atmosphere.”


For the earliest stages of accretion, while the nebula is still fairly cool, I agree. Post ignition is another matter. Direct acquisition from the nebula becomes problematic as the volatiles are swept out of the inner system. I’m convinced that any of the lighter gasses (H-He) which may have formed primordial atmospheres of the inner planets are also swept out several A Us.

Using our own terrestrial planets as a yardstick, it seems clear that all the inner planets have lost their primordial atmospheres. Additionally, I’m convinced that each of the inner planets has lost a good deal of whatever volatiles made up their out-gassed, secondary atmospheres. I view the current atmospheres of the inner planets as tertiary.


“The gas giants have large atmospheres because their large gravity accreted a lot of gas.”


Yes. I forget the exact figure, but I think the gas giant embryos needed to acquire about 8-10 Earth masses before run-away growth commenced. From that point onward, the only limitation to their growth was the amount of material in or near their “feeding zone”.

eburacum45
2003-Jun-27, 10:53 PM
The outgassing by a superterrestrial would be considerable, assuming that it had a radioactive core like the Earth; the heat would be trying to escape from a smaller surface area per cubic kilometer of volume.

So the atmosphere would be volcanic gases, CO2, sulphur compounds; more like a supervenus than a superterrestrial.