Astronomers Confirm a Hot and Steamy Exoplanet 66
The Bad Astronomer writes "The extrasolar planet GJ 1214b was discovered in 2009 orbiting a nearby (40 light year distant) red dwarf star. The planet was quickly found to have a thick atmosphere, but it wasn't known at the time if the composition was water vapor or a hazy shroud of particulates. New Hubble observations confirm the atmosphere of the exoplanet is rich in water, comprising up to 50% of the atmosphere's mass (PDF). At 230 degrees Celsius, this means the planet is shrouded in steam."
The observations don't "confirm" anything (Score:5, Informative)
Actually, they do nothing of the sort. They just make water a more probable explanation for the observations. It says as much in the article.
These [harvard.edu] abstracts [arxiv.org] both state that the data indicates an atmosphere high in hydrogen and helium, but (taken from the second abstract):
Re:The observations don't "confirm" anything (Score:4, Informative)
From the linked PDF, last of section 5.1 on page 15:
In the meantime, we adopt an atmosphere with at least 50% water by mass as the most plausible model to explain the WFC3 observations.
Re:What about the poles? (Score:4, Informative)
75 times closer to a Star five times smaller than the sun. I'm not gonna do the math if it's more complex than the apparent 5/4 ratio but it's important to consider the size of the Star if you're gonna talk about wide angle. And there might be a matter of brightness of the star too.
Anyway, the planet apparently does get more light, since its temperature is about 200C
Waterworld ! (Score:5, Informative)
With a density of 2 gm /cc, this is likely to be a true water world - a world where a rocky interior is surrounded by thousands of miles of ice (not "our" ice, but Ice XI, X, VII), probably a few 100 km of hot liquid (kept from boiling by pressure), and then a steam bath. Look at this phase diagram [lsbu.ac.uk], and remember that you are starting at 500 K or so, and the pressure increases greatly at depth, so going down into the planet means you are probably following a nearly vertical (but tilted to the right) line on the phase diagram.
Re:It won't stay that way for long (Score:4, Informative)
Where did you learn physics? Gravity is NOT a result of mass divided by volume. It's 1/r^2. That's mass divided by the surface area of the enclosing sphere.
Re:It won't stay that way for long (Score:5, Informative)
Low density? Density doesn't enter into the equation here - gravity is a function of mass, not density. Here, look at this
Note, the inner rocky planets are WAY more dense than the gas giants - hell Saturn would float if you could find a bathtub big enough to throw it in. Saturn and Jupiter have no problem holding onto H2.
This planet is 6.5 the mass of earth. Uranus, the smallest gas giant in our own system is 14 times the mass of earth and has half the density of this planet.
This isn't surprising. This planet seems to occupy a transition zone between rocky planet and gas giant. Uranus & Neptune are primarily Methane.
I wonder if it turns out that most planets of a certain mass range are mostly water - earth being on the one end and this new planet on the other side of the curve. After a point the gases in the planet transition to methane for some reason, then finally to just diatomic hydrogen in the case of the largest gas giants, and finally stars.
We already know that Jupiter is about as large as a planet can get by volume - any larger and the density starts increasing again, until fusion occurs and you get a star somewhere around 50 Jupiter masses. (Some astronomer please correct me on that).