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Old 17 Dec 2009, 01:28 AM   #89988 / #1
Goodchild
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Default Scientists discover Earth-like, water-rich planet

http://news.yahoo.com/s/afp/20091216...ienceastronomy

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Astronomers have discovered a new Earth-like planet that is larger than our own and may be more than half covered with water, according to a study published Wednesday in the science journal Nature.

The so-called "super Earth" is about 42 light years away in another solar system and has a radius nearly 2.7 times larger than that of our planet, according to the study by the Harvard-Smithsonian Centre for Astrophysics.
It may not be life-hospitable, but to find such a wet planet so relatively close seems a huge find.
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Old 17 Dec 2009, 02:55 AM   #90002 / #2
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Yeah! Lets go visit!
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Old 17 Dec 2009, 01:15 PM   #90084 / #3
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2.7 times the size of the earth, but with approximately the same density? That will give higher surface gravity, but probably be tolerable. It orbits its sun once every 38 hours, though....that's crazy.
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Old 17 Dec 2009, 03:20 PM   #90117 / #4
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Makes me happy. We might get out there someday yet!
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Old 17 Dec 2009, 03:51 PM   #90125 / #5
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Not hospitable to "life as we know it"?

I suppose the guy does not know about extremophiles.
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Old 17 Dec 2009, 04:32 PM   #90131 / #6
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Quote:
Originally Posted by Worldtraveller View Post
2.7 times the size of the earth, but with approximately the same density? That will give higher surface gravity, but probably be tolerable. It orbits its sun once every 38 hours, though....that's crazy.
Don't fancy trying to land a space shuttle on a planet travelling at that speed.
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Old 17 Dec 2009, 04:59 PM   #90145 / #7
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Don't fancy trying to land a space shuttle on a planet travelling at that speed.
Oh, that's easy. Once you match the vector of its movement, it would be as easy as landing on Earth.


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Old 17 Dec 2009, 07:40 PM   #90204 / #8
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I think the small issue of traveling 42 million light years is a bit more technically challenging right now than landing.
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Old 17 Dec 2009, 07:50 PM   #90206 / #9
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It's 42 light years, not 42 million, but still beyond our civilization's capabilities for the foreseeable future.

Landing would also be problematic, especially if the entire planet is covered by a very deep ocean (the article says more than half covered with water, but the scientists say roughly 50% water by mass; also, in this article, it's described as "composed of extraordinarily deep oceans, surrounding a rocky core").
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Old 17 Dec 2009, 10:56 PM   #90278 / #10
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PZ Myers, the Pharyngula blogger, has stated that a good question to ask is "How do you know this?" I will describe how this planet was discovered, and how much one can expect from the observational techniques.

I tracked down a primary source:
[0912.3229] A super-Earth transiting a nearby low-mass star

If that's too technical for you, try
CfA Press Room: Astronomers Find Super-Earth Using Amateur, Off-the-Shelf Technology

It was detected as part of an extrasolar-planet search effort, MEarth: small stars, rock!

MEarth is a system of 8 automated small telescopes that regularly observe 2000 nearby red dwarfs for evidence of planets crossing in front of them (transits). The MEarth team decided on red dwarfs because they are relatively small and dim, making it relatively easy for Earthlike planets orbiting them to become visible in this fashion. They'd cover up much less of a Sunlike star, and they'd orbit a Sunlike star so far away that it would be very improbable for their orbits to be aligned to produce transits.

The MEarth team has observed several transits of GJ 1214 by its planet GJ 1214 b, and that has been enough to determine that planet's orbital period, 1.5804 days, and its relative size. The planet causes a dip of 1.5% in the star's observed brightness each time it transits the star, implying a relative size of 0.12.

For further information, we have to learn about the star itself.

From its spectrum, one can find its surface temperature, which is about 3000 K (5400 F). By comparison's, the Sun's is 5800 K (9900 F). That star's surface is thus as hot as an incandescent light bulb's filament.

One can measure its distance with parallax, watching its direction change as the Earth moves around the Sun. It is 13 parsecs or 42 light-years away, with an uncertainty of 7%.

Turning to its brightness, its apparent magnitude is 14.7, meaning that you need a telescope to see it.

From these results, its luminosity is about 1/300 that of the Sun and its radius 1/5 that of the Sun. Its planet's radius is thus about 2.7 times the Earth's, or 17,000 km (27,000 mi).

One can estimate the star's mass from the masses of stars with similar luminosities and spectra, and it's about 0.16 times the Sun's. One then uses Newton's version of Kepler's Third Law to find that the planet is about 15 stellar radii away from the star. The star would look 8 degrees across from its planet, about the size of your fist at arm's length.

From these results, one can get the planet's temperature. If the planet absorbs all the light it receives, then its average temperature will be 555 K (280 C, 540 F). The Moon is close to that state, absorbing 78% of the light it receives. But if the planet reflects 75% of the light its receives, as Venus does, then its average temperature will be 393 K (120 C, 248 F).

To measure the planet's mass, one need additional information, and one can get it by studying the star's spectrum very closely. Both the star and the planet pull on each other, and one can watch the star move toward us and away from us as the planet orbits it. One can find the planet's mass from that, and it's about 6.6 times the Earth's. Putting the mass and the radius together gives an average density of 1.9 g/cm^3.

Comparing to some planetary-structure calculations gives a possible composition of 75% water and 25% rock. The planet would thus be a water world with an ocean extending about half the way down.


Finally, this star is in the constellation Ophiuchus, about halfway between Vega and Antares, two stars easily visible in the northern-hemisphere summer. The GJ in its name refers to the Gliese-Jahreiss star catalog, and the 1214 means that it's the 1214'th star in it.
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Old 18 Dec 2009, 09:59 AM   #90365 / #11
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Quote:
Originally Posted by Angra Mainyu View Post
Landing would also be problematic, especially if the entire planet is covered by a very deep ocean
What precisely would be the difficulty of landing in water? That would be easier than landing on land.


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Old 18 Dec 2009, 04:08 PM   #90461 / #12
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Quote:
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Quote:
Originally Posted by Angra Mainyu View Post
Landing would also be problematic, especially if the entire planet is covered by a very deep ocean
What precisely would be the difficulty of landing in water? That would be easier than landing on land.


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You mean, putting a vehicle on the surface of the water?

I suppose a problem would be how much the water moves; if not much, then that wouldn't be particularly problematic.

However, I thought the question was about astronauts (i.e., a manned ship), and then I don't see how they could do it: on the surface, there is (liquid) water, not solid ground. At the bottom, the pressure is probably too much.

I guess the astronauts could remain on board, but in that case, I'm not sure what the point of sending astronauts to the surface would be. Robots could do the job just as well (though if we had the technology to get there, robots might be able do the job just as well even if there is solid ground).

Last edited by Angra Mainyu; 18 Dec 2009 at 04:20 PM.
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Old 19 Dec 2009, 07:09 AM   #90788 / #13
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I'll now consider what sort of atmosphere GJ 1214b must have.

From cosmochemical considerations, it must also have sizable quantities of nitrogen and carbon, most likely as ammonia and methane.

Ammonia will get photodissociated into nitrogen and hydrogen, and the hydrogen will escape, but ammonia may be replenished from the planet's interior.

Something more interesting will happen to the methane. It will form a photochemical smog, much like what Saturn's big moon Titan has. This haze layer will form in the upper atmosphere, and block off much of the light. Titan's Bond (Wikipedia)albedo is about 0.27 (ScienceDirect - Icarus : The albedo of Titan), and using that figure for the planet gives an average cloud temperature of about 513 K (240 C, 464 F).

Using the (Wikipedia)Antoine equation for water, it will have a vapor pressure of about 34 bars. This is lower than the pressure for the (Wikipedia)critical point (thermodynamics) of water, which is 221 bars. That point's temperature is 647 K (374 C, 705 F).

Thus, water will have well-defined liquid and gas phases, though the planetary ocean surface will be too far down to see.

From this page on Titan's atmosphere, the maximum haze occurs at 250 km altitude, at a pressure of 0.3 millibars and a temperature of 540 K.

Assuming that this planet's haze forms at the same density, it would form at a pressure of 1 millibar.

One can find the height of the haze above the ocean with the help of the planet's atmosphere's (Wikipedia)scale height. Its surface gravity is about 8.9 m/s2, about 0.9 of Earth's, and combined with its temperature, gives a scale height of about 16 km. Putting the pieces together, the haze is about 160 km above the ocean.
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Old 19 Dec 2009, 07:30 AM   #90791 / #14
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It would be interesting if the reason for SETI's failure is that Earth-like planets tend to be covered entirely in ocean, and so when life evolves perhaps it never does manage to get past the octopus collecting coconut halves level of technology.

So how about naming the planet? I'm thinking either Aquarius (the water-bearer) or R'lyeh.


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Old 19 Dec 2009, 08:59 AM   #90802 / #15
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Aqua for short then but

190 degrees Celsius that is a bit warm for a swim.

Are we alone in our part of the Galaxy?

Was it just some 20 light years away?

Could we send laser pulses like binare code maybe?

Radio maybe drown in the noise? How powerful transmitter is needed?
Okay a good parabol antenna helps some dB but the earth turn all the time so get fast out of focus
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Old 20 Dec 2009, 08:36 AM   #91162 / #16
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Looks like there are lots of ways how a planet can be composed...

All the more reason to suppose that some are able to support complex biospheres. Even if they are comparatively rare, there are many stars in a galaxy, let alone the universe.
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Old 20 Dec 2009, 09:35 PM   #91354 / #17
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Here's an interesting take on what the surface of the planet might be like:

http://www.dailykos.com/storyonly/20...0/-Water-World
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Old 21 Dec 2009, 09:11 PM   #91588 / #18
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Quote:
Originally Posted by Angra Mainyu View Post
It's 42 light years, not 42 million, but still beyond our civilization's capabilities for the foreseeable future.

Landing would also be problematic, especially if the entire planet is covered by a very deep ocean (the article says more than half covered with water, but the scientists say roughly 50% water by mass; also, in this article, it's described as "composed of extraordinarily deep oceans, surrounding a rocky core").
we used to land on water in the 60s and 70s. Indeed it is likely that the new Orion capsule will land on water. As others have pointed out, once you're in the same orbit around the star as a planet, you're going at the same speed, and so landing is no harder than landing on earth. The difficult bit tends to be the differential between the orbital velocity around the planet and the rotation of the planet.
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Old 21 Dec 2009, 09:56 PM   #91603 / #19
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Quote:
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Quote:
Originally Posted by Angra Mainyu View Post
It's 42 light years, not 42 million, but still beyond our civilization's capabilities for the foreseeable future.

Landing would also be problematic, especially if the entire planet is covered by a very deep ocean (the article says more than half covered with water, but the scientists say roughly 50% water by mass; also, in this article, it's described as "composed of extraordinarily deep oceans, surrounding a rocky core").
we used to land on water in the 60s and 70s. Indeed it is likely that the new Orion capsule will land on water. As others have pointed out, once you're in the same orbit around the star as a planet, you're going at the same speed, and so landing is no harder than landing on earth. The difficult bit tends to be the differential between the orbital velocity around the planet and the rotation of the planet.
That's not the kind of scenario I was considering (I addressed that here).

Of course, there are other problems with landing on this planet, like the heat - and first and foremost, the problem of getting there in the first place.
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Old 21 Dec 2009, 11:06 PM   #91625 / #20
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wonder what the surf's like.
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Old 22 Dec 2009, 12:21 AM   #91648 / #21
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E.T. don't surf.
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Old 22 Dec 2009, 03:45 AM   #91690 / #22
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Lpetrich, do you have any ideas what sort of weather it would have? Being a water world, it wouldn't surprise me if endless cyclonic storms marched around and around the equator. As close to its primary as it is, I suppose it might be tidally locked, wouldn't it? That might produce a single unmoving superstorm.
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Old 22 Dec 2009, 03:47 AM   #91691 / #23
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wonder what the surf's like.
If it is tidally locked, there wouldn't be any.

In fact, even if it isn't locked, there wouldn't be any tidal wave action, maybe, with no continents to churn the tidal bulges. But I wouldn't be surprised if there were some hellacious storm-generated waves.
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Old 22 Dec 2009, 03:55 AM   #91693 / #24
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^I wrote those posts before reading the DailyKos article. Interesting!
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Old 22 Dec 2009, 10:48 AM   #91736 / #25
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Suppose I live say 5 years or 10 years or at most 15 years more.

Voivoi what I miss most is to die without knowing if Humanity make it or if they totally destroy all the diversity on earth and what if there is no life on any other planet and this one was the only one that by lucky circumstance had the chance to spread life all over the Galaxy and we blew it forever by being careless?
I want to know how it goes before I die! childish of me
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