Hi everyone

I don't know if you are already aware but there is an app for ipod touch called Exoplanets  which is free to download and it appears they have found a rocky planet the size of Saturn. I personally thought you couldn't get a rocky planet any bigger than Neptune but according to this app it is a Super Earth and it dwarfs Neptune and Uranus it is huge and it is called
KIC 6185331 b. it is almost exactly the same size as Saturn and It would way 4 times as much and its gravity would be even more stupendous.
you can find it on this site

http://www.planethunters.org

cheers

Karl

Thanks for the information Karl...Jan

Here's the discovery paper, but it doesn't mention a mass or composition:
http://arxiv.org/abs/1109.4621

A rocky planet the radius of Saturn would be more than 4 times as massive.  Earth's density is 8 times that of Saturn, and a larger planet would be denser yet, due to compression.  Even Mars, which seems to have a relatively smaller core than Earth, is 5.7 times as dense as Saturn. 

I suspect that this will turn out to be a gas planet, but it could still be much denser than Saturn.  WASP-14b is clearly a jovian, but it's density is 5.1 g/cm3, almost as dense as Earth. 
http://exoplanet.eu/planet.php?p1=WASP-14&p2=b

N Kalanaga

Nkalanaga, I always enjoy your comments on various thread and we all benefit from them, Thank you!!  Jan

Hi Guys

Glad you liked the info on KIC 6185331.

You may also be interested to know they found a planet bigger than Wasp14-b called CHT something(sorry can't remember its full name but it made Jupiter look like a walnut and it probably is a Brown dwarf due to its size and mass.) the Exoplanets app is free to download for itunes app store(for the ipod touch/iphone/maybe Ipad) the Mac also has an App store but it is really still in its infancy although they now have lots of good art programs on it so if you own a mac you might want to check it out.

Thanks

Karl

I may be wrong, but yes I think it just may be a brown Dwarf.  I believe that there is a limit to the size of any planet be it terrestrial type or gas giants,  when gravity is so great that it draws or compact things, the pressure creates friction creating core heat and you all know the rest...
Jan 

Most papers I've seen agree that Jupiter is about as large as a "cold" planet can get, diameter-wise.  Most wouldn't be more than 10 to 20 percent larger. 

On the other hand, a large brown dwarf can take a long time to cool, and will stay "puffed up" for considerably longer than a smaller BD or jovian.  Also, a gas planet orbiting close enough to be tidally heated is likely to be larger than a cold one.

In general, a brown dwarf will shrink to the size of Jupiter within a couple billion years, even if it's still hot enough to shine feebly.  The slowest to shrink, oddly, are those about 20  J'-masses, as they have less gravity.  They'll likely end up being the largest in diameter.  On the other hand, by 3 to 4 billion years, a 70 J-mass BD will be smaller than Saturn!

This page, from Dr. Adam Burrows,
http://www.astro.princeton.edu/~burrows/dat-html/brown.html
has all kinds of data, but interpreting it can be a chore.  It's all numbers, in scientific notation!  Most important, the radius is in GigaCentimeters!? 

He used to have a Brown Dwarf calculator, which was much handier, but when he moved to Princeton, they wouldn't let him run it there, for whatever reason. 

For artistic purposes, it doesn't really matter, unless you want the BD to be at a particular distance.  The Teff is in Kelvins, and would be more useful.

N Kalanaga

NK, always welcome your input and I didn't know that, thanks....Jan

Agree with Jan, this is a really interesting thread