Terrestrial (Rocky) Planet Discovered

KilgoryTrout writes "A 'super-Earth' planet was identified in orbit around mu Arae, a star 50 light years away. It orbits at 2 AUs and surface gravity is 14gs. Two gas giants have been detected in orbit about the star. Space.com's article suggests that it is a failed gas giant's rocky core."

Comments

Umm

[MindStalker]

No planet so small has ever been detected around a normal star.

Ummm Mercury, Venus..??
Shrugs.

Re:Umm

[linzeal]

The sun is not a star it is our god, all praise RA! Bring death upon those who would question him.

Re:Umm

[DNS-and-BIND]

There is only ONE god, he is the SUN god!

Ra! Ra! Ra!

Re:Umm

[AKAImBatman]

Well then, it's a good thing I'm running SunONE! Oh wait. No I'm not...

Re:Umm

[rleibman]

The sun is not normal.

Re:Umm

[steep5]

Alittle, no. Blittle, perhaps.

Another...

[cs02rm0]

...person with their 4" piece out?

So..

[Anonymous Coward]

Does this mean everyone that lives there is really short?

Then let's go!

[krinsh]

It may take a couple hundred years to get there; but there's bound to be a group of people eager to go on a long-term mission to this place - bring some kids along and make sure things are mixed up enough so the babies aren't West Virginians after a generation or three - and report back when they get there.

I know it's a lot more complicated than that, but we should. (and I'm from WVa so I'm not really being mean)

Re:Then let's go!

[escher]

Seeing as how the average adult human would weigh over 1000 pounds on that planet, I'm guessing it's not a real good idea to send colonists there.

Re:Then let's go!

[JAD lifter]

We could just give them anti-grav belts... If a colonists anti-grav belt failed, like the batterys ran dead or something, then the gtavity would suddenly affect them and they would just go like squash! and turn to bloody jelly with bits of bone sticking out. It would be cool.

Re:Then let's go!

[escher]

Boy, my astrophysics is bad! After reading through other comments I see that the planet would have to be the same size with that mass for my weight prediction to be accurate. I think someone calculated a little over 2g's so one could safely stand on the surface and not be crushed into a puddle of biology.

Re:Then let's go!

[Anonymous Coward]

Or perhaps the West Virginians really are a good idea after all -- aren't they already used to weighing 1000 pounds?

Re:Then let's go!

[xmas2003]

Given the 14G gravity, I think you need to send a buncha Incredible Hulk's over there if they wanted to be able to even stand up, much less survive.

Interesting for different reasons:

[hoggoth]

This is very interesting, however it isn't the most "Earthlike" planet found yet. There are three planets generally ignored by scientists because they are dead and orbit a neutron star. However they are Earth sized and there is a possibility that in the distant past they may have harbored life.

It would be monumental to find evidence that life on Earth isn't a singleton freak accident, even if we found it on worlds that could never harbor life again.

Re:Interesting for different reasons:

[Shadow Wrought]

It would be monumental to find evidence that life on Earth isn't a singleton freak accident, even if we found it on worlds that could never harbor life again.

I agree that a remenant of life would be just as powerful as full fledged life. I wonder though, if we were to ever find say a fossiled skelaton on Mars, if all the conspiracy nuts would claim it was planted. I have a feeling that the portion of the population that feels that life can only be on Earth will find ways to keep from having to change their beliefs.

Re:Interesting for different reasons:

[FlipmodePlaya]

Well, you also have nuts claiming that civilizations are thriving on the Moon, Mars, comets, etc as we speak. Nuts turning a hill into a monumental statue of a face, and sand dunes into a canyon sized glass worm. No matter what happens, we can assume there will be people whose preachings deviate from the obvious. It's best just to ignore them.

Re:Interesting for different reasons:

[PapaBoojum]

No matter what happens, we can assume there will be people whose preachings deviate from the obvious. It's best just to ignore them.

And suddenly Slashdot disappeared in a puff of logic.

Re:Interesting for different reasons:

[eraserewind]

I think that life is quite likely (almost certain) to exist somewhere other than earth. Multi-cellular-life is significantly (orders of magnitude) less likely. Intelligent-multi-cellular-life significantly less likely again.

Re:Interesting for different reasons:

[Anonymous Coward]

There are three planets generally ignored by scientists because they are dead and orbit a neutron star. However they are Earth sized and there is a possibility that in the distant past they may have harbored life.

I'd say that possibility is nonexistent, if our current theories about the evolution of stars are at least approximately correct.

The neutron star must have once been a red supergiant (which then underwent a supernova explosion). The orbits of these planets are much smaller than the size the star must have had at the supergiant stage. This means these planets must have formed after the star became a neutron star, perhaps from the remains of the supernova.

Re:Interesting for different reasons:

[wikdwarlock]

Forgive me if this is ignorant, but according to this article, a neutron star happens after a supernova. And if I recall correctly, between the swollen, red giant stage, and the devestation to any nearby planets by a supernova, wouldn't the surface of this planet be completely obliterated/mangled to the point that you'd never, ever find evidence of anything from before?

Re:Interesting for different reasons:

[Alsee]

Nah, don't ignore them. It's more fun to play with them. Tell them you found a Golfball on Mars.

-

Is there an astrophysicist in the house?

[eXtro]

If the star in question is roughly equal to our sun and the planet is 2AU away from the sun (which is twice the distance the earth is from the sun) why would it be so hot?

Re:Is there an astrophysicist in the house?

[elendel]

This being slashdot, post has an error - the planet in question is not 2AU away, rather the other planet in the system is. Quoth the aricle:

"the planet had to form inside the orbit of the larger planet in the system, which orbits the star about twice as far as Earth is from the Sun."

The article is a little short on info, but states of the discovered plane "It completes its tight orbit in less than 10 days" so we can assume it is much closer to the sun.

Re:Is there an astrophysicist in the house?

[elendel]

Hrm, someone has been stealing my 't's...

Re:Is there an astrophysicist in the house?

[Anonymous Coward]

It's at 2 AU's. That means it orbits at
TWICE the orbital radius as the Earth
from the sun.

2AU?

[thhamm]

found a bit more here:

http://www.eso.org/outreach/press-rel/pr-2004/pr-2 2-04.html

cant find anything about the 2AU. is that possible? 2AU radius and 10day period?

Re:2AU?

[Wubby]

RTA. The nearby gas giant is at 2AU. The rocky planet is within that orbit, and therefore going faster.

Wrong numbers

[Euphonious Coward]

It says the super-earth is so close to its star that it orbits in 10 days. A nearby gas giant is orbiting at 2 AU. Also, they say the mass is 14 times that of Earth. That would imply a surface gravity of 14G only if it was the same size as
Earth, which could only happen if it were made out of uranium or something.

I guess a radius 2.4 times that of Earth, if it's made of the same stuff, or less if it has more iron and less silicates.

Re:Wrong numbers

[Euphonious Coward]

Assuming radius is 14 ** (1/3) = 2.41 times Earth's, and it's made of the same materials, then surface gravity should be 14 / (2.4 ** 2) = 2.41G also.

Probably it's denser, and radius is smaller, and surface gravity is higher, maybe 3 or 4G, but not 14G.

Re:Wrong numbers

[thhamm]

is it at all possible to measure the "size" (density?) at such a distance?

i thought, these wobble/transit methods are used to just time the orbital period, so you can derive, using the stars mass, the companions mass?

Re:Wrong numbers

[Anonymous Coward]

Okay, I goofed twice over.
First, I interpreted a linear relationship
between mass and gravity, and said 14g's
where I'd read 14 times the mass of the
Earth.

Second, I read that it had to FORM inside the
orbit of a gas giant which orbits at 2 AU's.
That doesn't mean anything about what it's
actual orbital radius is.

My apologies. I still find the story interesting
though.

KilgoryTrout

Re:Wrong numbers

[mopomi]

Ok, here's the math:

g = GM/R^2

g = gravitational acceleration (m/s^2)
G = Universal gravitation = 6.67*10^-11 m^3/kg/s^2
M = mass (kg)
R = radius (m)

So, we are told that the new planet has 14 times the mass of the earth. If we were also to assume that the person who submitted this article is correct and that the gravitational acceleration is 14 times that of the Earth ("14 Gs") [I assume he/she/it meant at the surface of the planet], then we have the following equation for the radius of the newly discovered planet:

R = sqrt (GM/g)

where,
g = 14*9.8 m/s^2
M = 14*6x10^24 kg
G = 6.67*10^-11 m^3/kg/s^2

=> R = 6.4x10^6 m. The same as the Earth (parent stated this correctly, others have not)
[do the algebra before doing the arithmetic, the 14 drops out]

However:
=> Bulk the density of the planet is rho = M/R^3 = 14*6*10^24/(6.4*10^6)^3 = 3.2*10^5 kg/m^3

The density of Iron is about 8x10^3 kg/m^3. This would mean the planet is roughly four times more dense than iron, if its radius is as calculated (unlikely). However, Earth's bulk density is about 2.3x10^4 kg/m^3, so being 3-4 times the uncompressed density of iron is not problematic.

Besides, the star around which it orbits is one which produces more heavy materials than our star, so it's not unreasonable to assume that some greater proportion of its (the planet's) composition is more dense material. According to what we know (and as has already been stated), Iron is most likely to be produced. So, if the star puts out more dense materials in place of the less dense ones and emits roughly the same amount of iron, we may not really have too much of a problem. Especially considering that the radius of this planet is almost certainly somewhat larger than the radius of the Earth.

How you could get 14 Gs

[Engineer-Poet]

The average density of Earth is about 5.5 g/cc, while the surface rocks average 3.5 g/cc. There are two reasons for this:

1. The Earth's core is made largely of iron, which is much denser than rock.
2. The core matter is compressed by the pressure of the overlying material.

If you took Earth and doubled its size with no other changes, you'd have a surface gravity of about 2 G. If you tripled the diameter of the core at the expense of the mantle (more metals in the star, more metals in the planet), you'd increase the density of the mantle zone from ~4 g/cc to 8-10 g/cc; this would give you 6-9 G at the surface. Factor in some additional compression due to the overlying mass, and I could see 14 G surface gravity.

Still doesn't hold a candle to Mesklin.

Re:How you could get 14 Gs

[Euphonious Coward]

OK, if its density is doubled -- i.e., it's all nickel-iron -- then radius is halved, and gravitation squared, you'd get ~9G. There's no way you'd get enough extra compression to bump the gravity to 14G. (Remember the iron in Earth's core is under great pressure already.) You would need to admix uranium or something, as I noted earlier.

Under normal pressures, U is a little more than twice as dense as Fe, and might be a little more compressible; figure 2.5. Then, you get 9 * 2.5 * 2.5 = 56G for a solid uranium planet of 14 Earth masses.

Re:How you could get 14 Gs

[sexylicious]

First, you assume that the material is nickel-iron. It could be mostly osmium for all you know.

Second, if you double the density, the radius doesn't necessarily change. Which means that instead of 1 kg/m^3 of material you have 2 kg/m^3 of material. Which in turn means that the gravitational acceleration will double. As in a_gravity/m1 = G * M_planet / radius_planet^2. The radius doesn't change, G is a constant, but M_planet is twice as much. Thus you have twice as much acceleration.

If most of the planet is solid nickel-iron, rather than the percentage earth is, then I could see 14 g's at the surface.

Also, you can't compress uranium much more than it already is. That's how nuclear explosions occur. Plus, there is a limit to how much uranium you can pack into a space before nuclear reactions start to cascade. It's also most likely that the planet is made of mostly iron because that's where nuclear reaction rates are at their lowest; you can fuse stuff from hydrogen to iron, before it takes too much energy to fuse stuff, and you can split things from the high atomic numbers down to iron before it gets too hard. Iron is at the bottom of that curve.

Re:How you could get 14 Gs

[Engineer-Poet]

It could be mostly osmium for all you know.

No it couldn't. Curve of binding energy peaks at element 26 (Fe); osmium is up at atomic number 76. Osmium is always going to be too rare to make whole planets, as you noted.

... you can't compress uranium much more than it already is.

Au contraire, compression is one of the ways that very sub-critical masses of fissionables are turned into bombs (neutron reflectors are another). Peak densities are several times the STP solid density. Perhaps you never wondered why implosion designs are used for nuclear weapons; that's one reason.

So let's see, we need to pack 56 earth masses into 8 earth volumes. Going from rock to nickel-iron gets you a factor of 2.4 or so, which yields 19.2 masses; if the heat of formation helped to boil off the materials of lower density it wouldn't surprise me. Could compression push the density up by another factor of 3? If conventional explosives can do it in a small package, it seems likely. Are there any high-pressure physicists who can offer a pointer to research here?

Re:How you could get 14 Gs

[sexylicious]

Au contraire, compression is one of the ways that very sub-critical masses of fissionables are turned into bombs (neutron reflectors are another). Peak densities are several times the STP solid density. [google.com] Perhaps you never wondered why implosion designs are used for nuclear weapons; that's one reason.

Exactly the reason you'd not see a planet made of the stuff. Your cross-sections are just too high; meaning your chances of a neutron escaping one atom and hitting another that much more likely. Once you get past a certain mass, you've created a bomb.

From your link:
It would seem that the lower density delta phase has offsetting disadvantages in a bomb, where high density translates into improved efficiency and reduced material requirements, but this turns out not to be so. Delta stabilized plutonium undergoes a phase transition to the alpha state at relatively low pressures (tens of kilobars, i.e. tens of thousands of atmospheres).

Meaning that they used a high density version of pure plutonium because they could get away with less than the critical mass. The extra "mass" needed to initiate the reaction came from the high explosives used to implode the spheriod of plutonium and the shock heating such explosive lenses create.

Re:How you could get 14 Gs

[Markus Registrada]

Oops, I'm wrong. Double the density, and the volume goes down by half, so the radius goes down by just 1/(2**(1/3)), or just 0.79. Surface gravity increases, then, by a factor of 1/(0.79**2), or 1.59, for a total of just 2.41*1.59 = 3.8G. There's no way a 14-Earth-mass planet can pull much more than 4G surface gravity if the heaviest stuff you have to work with is iron, no matter how hard your little planet's gravity squeezes it.

So, your uranium planet (for as long as it would last) would be (1/(2.5**(1/3)))*0.79 = 0.58 the size of one with Earth's density. Its surface gravity would be 1/(0.58**2) times our Earth-density planet, or just 2.41*2.94 = 7G. Still not very close to 14G. (I guess you'd need some unobtainium.)

Re:How you could get 14 Gs

[Engineer-Poet]

Iron isn't fissionable. Neither is nickel. Try again.

Re:How you could get 14 Gs

[sexylicious]

au contrare...

Anything except hydrogen is fissionable. It's just that your energy approaches infinity as you try to do fission on elements on the hydrogen-iron curve. Iron is indeed fissionable, it just takes more energy to split it than you would get out.

Re:How you could get 14 Gs

[Engineer-Poet]

Here's what I was replying to, in case you missed it:

Exactly the reason you'd not see a planet made of the stuff. Your cross-sections are just too high; meaning your chances of a neutron escaping one atom and hitting another that much more likely. Once you get past a certain mass, you've created a bomb.

Regardless of bombardment, iron does not emit neutrons with enough additional energy to cause a chain reaction (which you admitted when pressed), so your statement in the great-grandparent is simply not relevant to the discussion. Compression can increase the density of any material (not just plutonium), and a 3x compression of a very large iron core would be sufficient to create a planet twice the diameter of Earth but 56 times its mass and thus 14 G surface gravity, QED.

(not that pure natural uranium can support a chain reaction either, you have too much fast-neutron-eating U-238 and no moderator.)

Re:How you could get 14 Gs

[sexylicious]

I was replying to this person..

OK, if its density is doubled -- i.e., it's all nickel-iron -- then radius is halved, and gravitation squared, you'd get ~9G. There's no way you'd get enough extra compression to bump the gravity to 14G. (Remember the iron in Earth's core is under great pressure already.) You would need to admix uranium or something, as I noted earlier. Under normal pressures, U is a little more than twice as dense as Fe, and might be a little more compressible; figure 2.5. Then, you get 9 * 2.5 * 2.5 = 56G for a solid uranium planet of 14 Earth masses


Then you came along and pointed out that:
... you can't compress uranium much more than it already is.
Au contraire, compression is one of the ways that very sub-critical masses of fissionables are turned into bombs (neutron reflectors are another). Peak densities are several times the STP solid density. [google.com] Perhaps you never wondered why implosion designs are used for nuclear weapons; that's one reason. So let's see, we need to pack 56 earth masses into 8 earth volumes. Going from rock to nickel-iron gets you a factor of 2.4 or so, which yields 19.2 masses; if the heat of formation helped to boil off the materials of lower density it wouldn't surprise me. Could compression push the density up by another factor of 3? If conventional explosives can do it in a small package, it seems likely. Are there any high-pressure physicists who can offer a pointer to research here?

My text in bold. You can't compress things denser than iron without running into unstable elements being made. As I noted. You can make a fission bomb out of anything that is more dense than iron, but with most of those elements, it will take a lot more energy to sustain the fission reaction than if you chose one of the more highly radioactive ones. When you get to the other side of iron, the energy yeilded from a fission reaction is never enough to sustain it (fast nuetrons can not be produced fast enough).

That's how my statement was relevant.

As for compressing uranium in the case of a planet having a uranium core, you could do it up to a point. Once you pass a certain mass, the planet is essentially becomes unstable because compression is driving the naturally occuring nuclear reactions to create more than enough fast neutrons that it doesn't matter how much U238 you have in there. The mass will eventually explode from heat if it continues to be compressed, or the mass will radiate energy as it transmutates into elements with different (lower) atomic masses. Eventually the entire planet's mass will reach equilibrium and you'll have a gaussian distribution of elements, with a center probably around lead and its neighbors. You can't compress uranium too much, otherwise it will get too hot. As I said in the great-great-great-grandparent post, "If most of the planet is solid nickel-iron, rather than the percentage earth is, then I could see 14g's at the surface."

As for the planet having 3x the compression with twice the mass, most definitely. The equation that you would use to figure this out is similar the hydrostatic equation. You would integrate that over the volume of a sphere to get the force distribution of the matter in the sphere. IIRC, your pressure (compression) would increase linearly with depth. That compression would also heat up the material and you'd get a Rayleigh-Taylor instability if the material below liquified due to the heat. (More dense material (solid) on top of a less dense material (liquid).) You'd end up with a similar situation as what earth has with its tectonic plates. But that's only if the planet's mass is heated enough during compression. And judging from the distance from its parent star, I'd say that there is a significant heat input, so the planet more than likely has a scenario that is like plate tectonics.

Cross-checked numbers

[Engineer-Poet]

It goes something like this:

1. The star's temperature yields its luminosity, and indirectly its mass.
2. The Doppler shift and period of the wobble yields the planet's mass as a fraction of the star.
3. The amount of light blocked by the planet yields its area, and thus its size.
4. From size, you can calculate volume. Density = mass/volume.

If the star is close enough and the planet heavy enough you can cross-check the wobble using astrometry.

This is big!

[Anonymous Coward]

This is big! Even if there is no life, there can be big amounts of liquid water - the essence of life as we know it, and an important temperature regulator (in the inner parts of a solarsystem) to keep a planets climate "stable" over the billions of years.

14 Gs is nothing that suits us, but if the planet contains no life, we must seed it ASAP, and bring life to universe! :)

Re:This is big!

[AragornSonOfArathorn]

With a surface temperature of 1100+ degrees Fahrenheit, i doubt there is much liquid water.

Re:This is big!

[Anonymous Coward]

Hm. I am poster of grandparent, I assumed the planet would be 2AU from its star. However in the article it seemes as if one of the OTHER planets is 2 AU from its star.

With a sun like ours a planet 2 AU from it should not have surface temperatures of 1100 deg F.

It has to be suggested...

[RobertB-DC]

While researchers do not know the full range of conditions under which life can survive, the newly discovered world, with its hot surface, is not the sort of place biologists would expect to find life as we know it.

No, of course not. Life there would posess super-human strength as an adaptation to the enormous gravity. Were inhabitants of this planet to visit Earth, they would be faster than a speeding bullet, and stronger than a locomotive. I wager they'd be able to jump tall buildings with a single bound.

I wonder if anyone's thought of a name for this planet?

(How can there be two dozen comments, but nobody made this connection yet?)

Re:It has to be suggested...

[El]

Uh, it can't be Krypton. Krypton has already been destroyed. Still, it would be interesting to know what the core of the planet is made of!

Re:It has to be suggested...

[dowobeha]

Oh, but has it? I haven't seen Superman flying around, have you? Maybe Krypton hasn't been destroyed yet, and that's why Superman isn't here yet. :)

Re:It has to be suggested...

[D4C5CE]

I wonder if anyone's thought of a name for this planet? (...) Life there would posess super-human strength as an adaptation to the enormous gravity. Were inhabitants of this planet to visit Earth, they would be faster than a speeding bullet, and stronger than a locomotive. I wager they'd be able to jump tall buildings with a single bound.

So since Krypton is already taken and any proposal on /. is bound to pay tribute to the home computer era of the 1980s, from your description of the life forms and their presumable favorite tourist activity on Earth, this planet's most appropriate name would quite obviously have to be... Rampage ;-)

Re:It has to be suggested...

[Anonymous Coward]

Has nobody read the Dosadi Experiment?

A hellish world with high surface
gravity, significant genetic mutations
and/or engineering to adapt the
inhabitants to survive? It'd make a
great little terrarium.

Just don't let the lab rats get out of
the cage; some supermen might be a little
mad about being locked up in it by
weakling earthlings.

It has to be said...

[WarMonkey]

It has to be said...

Weapons of Mass Deduction!

Mu Arae

[thhamm]

Located at only 0.09 AUs from the star (less than one fourth of Mercury's orbital distance in the Solar System), the planet competes an orbit in less than 9.55 +/- 0.03 days and may have a surface temperature of 1,160 Fahrenheit (or 900 Kevin).
The astronomers believe that under the most likely planetary developmental scenario of inner migration from around 3 AUs under the influence of outer giant planet "b" now at 1.5 AUs, this planet is likely to have an "essentially rocky core" with an atmosphere of five to 10 percent of its total mass.

there is also more info on the Mu Arae System itself:
http://www.solstation.com/stars2/mu-arae. htm

now the 0.09AU sounds better. :)

How the hell do they know?

[DesScorp]

Come on, I love Astronomy, but observation is the only method to gather information outside of our solar system in astronomy (well, except for radiation studies), and this "world" is so far away, how the hell do they know it's a gas giant core? We're talking about extreme conjecture here. No photos, no probes, just some evidence that it exists by means of tracking positions of its' star (that's typically how these far-away planets are "found"; observations of SOMETHING pulling agaisnt a star and affecting it's motion).

Re:How the hell do they know?

[Thrymm]

I was also always under the impression a gas giant has no solid core. Am I wrong in my assumption?

Re:How the hell do they know?

[DesScorp]

Gas giants are supposed to have rocky cores, yeah. It's just that most of the planets volume is gas, usually under heavy pressure. So any probe would be crushed and melted long before it had a chance to get to a core.

Keep in mind what I said about conjecture here. The idea that the gas giants have rocky cores just fits the best theories that astronomers have. There's no way to actually bore down and tell for sure at this time.

Must be where the "greys" come from.

[Anonymous Coward]

Consider that a heavy world 2 AUs away from its star (what magnitude is it?) would produce beings that were low in body mass and not enough melanin to darken their skin.

IMO the lower mass would allow functioning limbs in heavier Gs. Stout stoky beings would expend too much energy getting around. ;)

Gravity

[dolphin558]

Density has alot to do with the magnitude of surface gravity. It could be that if this was a core then this "planet" has no mantle/core but is just one big rock with no layers at all. That should "up" the surface gravity considerably.

Re:Gravity

[mopomi]

". . . is just one big rock with no layers at all"

That's not very likely. The gravitational potential energy that would be converted to heat as the planet accreted would be more than enough to melt the entire body, thus allowing the heavier materials to tend to sink to the center of the planet. A planet this size would almost certainly have differentiated.

Besides, it is mass and radius^2 that matter, not specifically density. For example, Jupiter has a bulk density around 1330 kg/m^3 (water is 1000 kg/m^3), but has a large equitorial surface gravity (23.12 m/s^2). Earth is 5.52x10^3 kg/m^3 with g=9.8 m/s^2

Re:Wrong numbers--stupid mistake in my own math!

[mopomi]

Dammit! Dammit! I missed some important numbers in the density calculation. volume of sphere = R^3*Pi*4/3, not R^3. Duh! Ok, so the density is not 3.2x10^5 kg/m^3, but is instead, 3*3.2x10^5/(Pi*4) =~ 8000 kg/m^3. Like iron. Earth, of course, is around 5.6x10^3 kg/m^3. I'm an idiot!

Where the term "Class M" came from

[Anonymous Coward]

Did Star Trek just randomly invent "Class M" meaning "earth-like" or does this designation have some background in fact?

Re:Where the term "Class M" came from

[boy_afraid]

From a Vulcan term: "Minshara-Class"

Class M is the classification used in Star Trek to refer to planets suitable for supporting life as we know it. They usually have oxygen/nitrogen atmospheres and are in a temperature range similar to Earth's.

Many people have complained about how many planets in Star Trek are Class M. The reason for this is simply one of budgets. Scenes taking place on a Class M planet can be easily filmed on Earth. Other planets need detailed sets made in studios.

Well known Class M planets in Star Trek are: Earth, Kronos and Bajor.

On the Star Trek series Enterprise, Sub-commander T'Pol suggests that Class-M stands for Minshara-Class, a Vulcan term.

Other canonical Star Trek planet classifications include Class D planet, Class H planet, Class J planet, Class K planet, Class L planet, and Class Y planet.

Really?

[StarKruzr]

I thought G-type yellow dwarves were fairly commonplace.

A planet of compressed U, huh?

[StarKruzr]

Boy, I bet there'd be some great fishin' on that planet. ... ::runs::

Hmm.

[StarKruzr]

You know far too much about nukular explosions to be a normal, God-fearing American. You must be a terrorist.

Guards! GUARDS!!! HOMELAND SECURITY ALERT!

So I was under the impression that the reason we have a hot, molten core is that the radioactive elements inside it are causing a sustained fission reaction that's generating the heat. I'm guessing what you just said means that's not entirely accurate? I.E., if the threshold ("critical mass," if I understand the term correctly) for a fission reaction WAS crossed, our core would currently be generating well in excess of enough energy to blow the planet apart?

Re:Hmm.

[sexylicious]

As we currently understand atomic physics, that would be the case.

The ratio of iron to fissionable elements is pretty big; in other words, there is much more iron than fissionable materials.

Much of the initial heating of the earth was from compression of the stuff that the planet is made of. Most of that heat was trapped inside, and allowed the most common, dense materials to slowly sink to the center. Because of pressure, the core is believed to be a semi-solid oblong sphere of iron and nickel, with a liquid mantle surrounding the core.

There are enough radioactive materials that they do provide some heating. Most of the heat input is caused by friction which arises from the stresses caused by the moon and sun. But the amount of heat input from friction and radioactive decay is extremely tiny compared to the amount of heat stored in the liquified and semi-solid material inside the earth.

And uh... no comment on who my employer is. ;)

Earth2

[boy_afraid]

So, when do they start staffing the exploration to start the series "Earth 2".

http://epguides.com/earth2/

Small, rocky planets are more dense

[geoswan]

Should we automatically assume that this planet 14 times the mass of the Earth will be denser than the Earth?

If you look at the density of the planets in our solar system you will see that the smaller rocky planets are more dense than the more massive planets.

Most of the Universe is Hydrogen. Hydrogen is very light. That means that hydrogen molecules move more quickly.

It is like Maxwell's daemon. Some of the hydrogen at the edge of the planet's atmosphere will be slower than average, and some will be faster then average. A less massive planet with less powerful gravitational field has a slower escape velocity. If that fast moving hydrogen, at the edge of the atmosphere, is moving at greater than the planet's escape velocity, and it doesn't hit another gas molecule to slow it down, its lost for good.

This is why Earth's atmosphere has no free hydrogen. Ditto Venus, Mars and Mercury. This is why Mars has such a puny atmosphere. If the Earth had formed out near Pluto it may have retained a huge amount of hydrogen.

If the temperature of this 14x planet is not too high, maybe its escape velocity is high enough that it retained a lot of hydrogen and helium too.

However, if it is orbiting its Primary in just ten days, maybe the temperature of its gas is high enough that it will lose its atmosphere as I described above anyhow.