No big planets close to the Sun?

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No big rocky planets?

Why are there no big rocky planets - all the big planets are gaseous.
Did big rocky planets get smashed up and end up in the Kuiper belt?
 
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  • #2
Janus
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Why are there no big rocky planets - all the big planets are gaseous.
Did big rocky planets get smashed up and end up in the Kuiper belt?
There simply wasn't enough building material to make large rocky planets. Even if you put all the rocky bodies in the Solar System together, it wouldn't even come close to matching the mass of Jupiter.
 
  • #3
russ_watters
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Well, that plus if there weren't big gaseous planets, there'd be rocky ones in their places - all the giant gaseous planets are believed to have large rocky cores. So maybe a better question would be: why don't the rocky cores in the inner solar system have gaseous planets around them? The answer would be that it was blown away when the sun ignited.

The atmospheric proportions of hydrogen and helium are very close to the theoretical composition of the primordial solar nebula.
http://en.wikipedia.org/wiki/Jupiter

So, it is reasonable to assume that its fraction of heavier elements is also pretty close to the amount in the original primordial solar nebula.

Here's what they think about the core:
There is still some uncertainty regarding the interior structure of Jupiter. One model shows a homogeneous model with no solid surface; the density may simply increase gradually toward the core. Alternatively Jupiter may possess a dense, rocky core with a mass of up to twelve times the Earth's total mass; roughly 3% of the total mass.[21][18] The core region is surrounded by dense metallic hydrogen, which extends outward to about 78% of the radius of the planet.[18] Above lies a transparent interior atmosphere of liquid hydrogen and gaseous hydrogen, with the gaseous portion extending downward from the cloud layer to a depth of about 1,000 km.[18] There may be no clear boundary or surface between these different phases of hydrogen; the conditions blend smoothly from gas to liquid as one descends.[22][23]

The temperature and pressure inside Jupiter increase steadily toward the core. At the phase transition region where hydrogen becomes metallic, the temperature is believed to be 10,000 K and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K and the interior pressure is roughly 3,000–4,500 GPa.[18]
 
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  • #4
Jupiter and the gas planets started out at the size of earth originally, and when the sun blew out most of the nebula when it started nuclear fusion, the outer planets captured a lot of this gas, and thus, that is the reason why they are so big, and also, I believe that the nebula was mostly in the outer regions... I'll need to check up on that.

The reason why some extrasolar planets are gas giants is because they are brown dwarfs, and never became stars, even though some are as much as 5 times bigger than Jupiter, and our instruments so far are not sensitive enough to find Earth sized planets.

Btw, when is that telescope for finding Earth sized planets going to be launched?
 
  • #5
chemisttree
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Well, that plus if there weren't big gaseous planets, there'd be rocky ones in their places - all the giant gaseous planets are believed to have large rocky cores. So maybe a better question would be: why don't the rocky cores in the inner solar system have gaseous planets around them? The answer would be that it was blown away when the sun ignited.
Shouldn't the Sun have the largest and rockiest core of all?
 
  • #6
The reason why some extrasolar planets are gas giants is because they are brown dwarfs, and never became stars, even though some are as much as 5 times bigger than Jupiter, and our instruments so far are not sensitive enough to find Earth sized planets.
Umm, I'm not sure about that. "PSR B1257+12 A" is an exo-solar planet with a mass that is LESS than the earth's (it's only 2x lunar mass).

But that's not all. A possible comet/asteroid may have also been discovered in the same pulsar system that has an UPPER mass limit of 0.0004 Earths!

Exo-solar planets that are less than 8x Earth mass have also been discovered about main-sequence stars.

Btw, when is that telescope for finding Earth sized planets going to be launched?
There are several with similar mission statements. There was one launched in december, the French-led Corot mission.

Then there are the James Webb Telescope, the Terrestrial Planet Finder (launch around 2015), or the Kepler mission (scheduled launch in October 2008).
 
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  • #7
Shouldn't the Sun have the largest and rockiest core of all?
Why do you say that? I would think the intense temperature and pressure in the core would keep it in a gaseous state. Although the core does rotates as a solid body.
 

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