9 ms·

Distant 'waterworld' is confirmed

71 points by esalazar 15y ago

kijin 15y ago
> 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 15y ago
  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?
  - hartror 15y ago
    It in fact does! The surface gravity is 0.91 g[1]. http://en.wikipedia.org/wiki/GJ_1214_b http://en.wikipedia.org/wiki/GJ_1214_b
  - deleted 15y ago
    [deleted]
  - lbolla 15y ago
    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 15y ago
      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).
      - robdoherty2 15y ago
        So maybe this planet is more like "Bespin" than Waterworld!
      - bdonlan 15y ago
        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.
jwallaceparker 15y ago
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 15y ago
  To what end?
  - Cieplak 15y ago
    It would be pretty freaking awesome, although I wonder if the cost of building and maintaining such a station could be recouped from fees and sponsorship.
    - itsmequinn 15y ago
      Or a theme park. There's whalers on the moon.
  - deleted 15y ago
    [deleted]
  - agravier 15y ago
    Moon station: Undisturbed astronomical observation (minimize earth's interference, take advantage of moon's almost non existent atmosphere)? A robotic station on the other side of the moon with a transmission station on our side?
  - dstorrs 15y ago
    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.
    - 15y ago
losvedir 15y ago
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/0/1 http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all...

71 points by esalazar 15y ago

kijin 15y ago

> 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 15y ago
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?
- hartror 15y ago
  It in fact does! The surface gravity is 0.91 g[1]. http://en.wikipedia.org/wiki/GJ_1214_b http://en.wikipedia.org/wiki/GJ_1214_b
- deleted 15y ago
  [deleted]
- lbolla 15y ago
  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 15y ago
    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).
    - robdoherty2 15y ago
      So maybe this planet is more like "Bespin" than Waterworld!
    - bdonlan 15y ago
      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.

jwallaceparker 15y ago

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 15y ago
To what end?
- Cieplak 15y ago
  It would be pretty freaking awesome, although I wonder if the cost of building and maintaining such a station could be recouped from fees and sponsorship.
  - itsmequinn 15y ago
    Or a theme park. There's whalers on the moon.
- deleted 15y ago
  [deleted]
- agravier 15y ago
  Moon station: Undisturbed astronomical observation (minimize earth's interference, take advantage of moon's almost non existent atmosphere)? A robotic station on the other side of the moon with a transmission station on our side?
- dstorrs 15y ago
  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.
  - 15y ago

losvedir 15y ago

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/0/1 http://arxiv.org/find/all/1/all:+AND+berta+gj1214b/0/1/0/all...