

Distant 'waterworld' is confirmed - esalazar
http://www.bbc.co.uk/news/science-environment-17117030

======
losvedir
It never ceases to amaze me what information we can glean about things so far
away from us.

Zach Berta in the article is my friend, so it's neat to see this article here
on HN. :-) When the article was accepted for publication we all watched
Waterworld and he gave a high level overview of the research to me (as a non-
astrophysicist).

How I understood it is: When the orbiting planet crosses between its star and
us, it blocks some of the light, and the decrease in brightness can be used to
calculate the diameter of the planet. In addition, the planet orbiting the
star makes it wobble a bit, and from that you can calculate its mass. These
two things limit the possibilities of the planet's composition, and a
watergiant is the most likely scenario. In the papers on the Arxiv[1], it
looks like there's finer grained observations than those, though, so maybe
that was just what caused them to give it a closer look.

[1]
[http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all...](http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all/0/1)

------
jwallaceparker
I'm kinda surprised that it's 2012 and humanity still hasn't created a space
station on the moon, Mars or some other planet.

~~~
blario
To what end?

~~~
dstorrs
1) Building out sufficient solar power collectors to solve the Earth's energy
problems forever.

2) Manufacturing medicines, alloys, and materials that can only be produced in
micro-gravity.

3) Protecting humanity against social breakdown and/or extinction in case of
massive asteroid strike / global pandemic / etc.

4) Because every dollar that has been spent on space development in the US has
put $7 back into the economy by way of spinoffs, technical advances, etc.

~~~
blario
If bullet number 4 is correct, it sounds like a good idea. I would have to see
proof that bullets 2 and 4 are correct in order for me to agree though.

3) is far fetched and would be catastrophic regardless, and 1) may not be
viable because the 15 days of the month where the far side of the moon is
facing the sun, it isn't facing the earth. If placed on the other side, 50% of
the month, earth would be blocking out the sun on the moon's surface, and the
other 50% of the month, the near side of the moon wouldn't be facing the sun.

------
kijin
> _It is about 2.7 times the Earth's diameter, but weighs almost seven times
> as much._

2.7^3 = 20 times the volume. But only 7 times the mass. So its density would
be only 35% of Earth's density. Earth's density is 5.5g/cm^3. That makes this
planet's density 1.9g/cm^3, which looks about right for an object that is
partially rock and partially water.

But this ain't a waterworld, it's a steamworld. Imagine the greenhouse effect
from all that water vapor!

~~~
geuis
Does the density & mass calculation affect what the surface gravity would be?
If the planet is more massive than Earth, but less dense, would someone
standing on the surface experience a greater weight than we do here?

~~~
lbolla
Gravity depends on m/r^2 where m is the mass of the planet and r its radius.
Compared to Earth's, m = 7 m_earth and r = 2.7 r_earth, which gives you a
gravity 0.96 times the gravity on Earth. Remarkably similar... But I wonder,
if the temperature is 200 degrees, there must be a massive pressure, in order
to have liquid water. Where does the pressure come from? Heavy atmosphere?

~~~
kijin
Pressure is nothing other than gravity pulling down everything that lies above
you. So if you go deep enough, there will be enough gas above you to create
enough pressure to make water liquid, or even solid.

I wonder whether it will be possible to build a floating city somewhere in the
middle of that massive atmosphere. Air conditioning will probably take up the
majority of the city's energy consumption, but hey, if you've got water, you
can get oxygen, and if you've got _boiling_ water, you can make electricity.
Actually, it might be easier to live on this planet than to live on Venus
(450C, all CO2).

~~~
bdonlan
Boiling water doesn't give you electricity. A temperature gradient gives you
electricity. Having a hot, steamy planet won't help you if the air is just as
hot as the water.

