You've lived on the Earth all your life, so you'd think you know plenty about planets. As usual though, the Universe is stranger than we assume, and the planets orbiting other stars defy our expectations. ...

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Hi, that´s my first post. So, greetings to all bautforum members.
As to hot, low density Jupiters: I don´t understand why this obviously seems to be a surprise to experts (which I am not). Shouldn´t all gas-planets pass a low-density stadium during contraction of the gas cloud from which they form?
DHD40

Well yes, but the gas giants are low density for gas giants.

Thank you Ronald,
you said: Well yes, but the gas giants are low density for gas giants

Oh yes, I think I understand. What you´re saying is that they are low density as compared to already known gas giants of the same (similar) size. I wasn´t aware of this.
DHD40

The density of these new worlds is only 0.25 times the density of water. Jupiter is more dense than water, and Saturn is 3/4 the density of water (more or less).

Models that include temperature and contration as a function of time can't figure out what these gas giants are doing, so people are very confused.

There is a neat sorry on these "cork" density planets at NASA.

Thanks for the link to Nasa´s report.
How about extremely high rotational speed of the planet, just not enough to tear it apart. Or is this an absurd idea?

Just found the forums and Astronomy Cast podcasts and listening to the Hot Jupipters podcast I wondered if anyone had yet determined how something made predominantly of gas, as in a Jupiter type planet, could orbit so close to its parent star without it being destroyed or the gas being totally evaporated?

S56