More on the Waterworld Goldilocks Planet

goldilocksmission writes with this snippet from Goldilocks Mission: "News spread recently about a super-earth-sized planet that has been recently discovered to contain one of the most essential compounds for life to exist in the universe: water. ... GJ1214b is a massive planet that can house about six earths and is about forty light-years away from us. ... The significant discovery leap of detecting Gliese 581d to the more goldilocks planet oriented GJ1214b is a testament to the advances in the technology of detecting earth-like exoplanets."

Re:Goldilocks?

[Anonymous Coward]

As a serious answer, the Goldilocks zone is the orbital distance that lends itself to an earth-like amount of incident solar energy and (potentially) a higher likelihood of life friendly conditions existing.

The porridge isn't too hot or too cold... it's just right.

Re:something I could not figure out about waterwor

[Anonymous Coward]

"How did they get fuel for the fricking jet skis?"

their home base was an oil tanker.

Higher Ice Phases

[mbone]

A "waterworld" would actually have a fairly shallow ocean, on the order of 75 to 100 km deep for an Earth size planet, as other ice phases would form at the bottom of the ocean [arxiv.org] at depth.

Re:Goldilocks?

[Grishnakh]

Not necessarily. It depends on the planet's density. Of course, given that it's 6 times larger than Earth, it's most likely its gravity is significantly higher, but not necessarily, and not necessarily proportional to its larger size.

Inaccurate article

[plavchan]

Contrary to what the article states, MEarth is not an amateur astronomy group. MEarth is headed by the former Discover Magazine's Scientist of the Year, Harvard professor David Charbonneau. The business of identifying tiny changes in the brightness in the star from among an ensemble of thousands of carefully selected targets is no easy task. That being said, many amateur scientists have been able to follow-up and confirm transiting planets. I say amateur, but many have telescope rigs and detectors costing upwards of $50k (USD). In that sense, the amateur community has contributed greatly to the follow-up of transiting planets. Also, the article mentions GJ 1214 to be 300 times "cooler" than the Sun. It's 300 times less luminous, not cooler (although the stellar surface is cooler by a factor of a few). I will wait for the confirmation of water from transit transmission and absorption spectroscopy.

Re:Goldilocks?

[HappyHead]

Surface gravity isn't just determined by density either - there's also the distance from the center of mass to be considered. I got the impression that the planet's mass was measured at 6 times earth, but it's actual diameter was not determined. Technically, it could be anything from a ball of Uranium half the diameter of earth to a loose saturn-like cloud collection the size of Neptune. (Saturn's average density is less than that of water.) The surface gravity of the Uranium-ball planet would be much higher than that of the cloud, mainly because of the distance from the center of mass, since gravity falls off fast with greater distance. With a mass of 6x earth, there technically _should_ be a diameter at which the planet actually has a surface gravity similar to earth.

Re:Higher Ice Phases

[mbone]

Depends on your point of view. The 6 Earth-mass planet modeled by the Léger et al. paper I referenced has a 5000 km thick water mantle, but only the top 100 km of that would be liquid, which seems pretty shallow to me, considering. All of the higher phases of ice are denser than liquid water, and they form under pressure, so this conclusion seems pretty robust to me.

Re:nothing new here

[Nutria]

It has the feel of a new cult.

Not only that, but they have the inane thought that a planet 1/40th of the distance from Mercury to Sol might actually be habitable because "a red dwarf ... is significantly more than three hundred times cooler than our own", neglecting the inverse square law, and that it would be red light, not the rainbow spectrum we require.

Re:Goldilocks?

[anon mouse-cow-aard]

python says: 6**0.5 = 2.449... So if a planet with 6 times the mass has 2.45 times the diameter at the surface, It's juuussst right!

Re:Actually...

[CrimsonAvenger]

With six times the mass of earth and subsequently higher gravity, any bi-pedal life from that evolves there will most certianly be able to kick your average human's ass.

Umm, no. That particular planet has a surface gravity of 0.9g. Six times Earth's mass, but only 1/3 Earth's density....