Planetary data merge shows three Earth-like planets in close star system Astronomers are spending more and more time looking for planets in the "Goldilocks Zone," meaning those orbiting at just the right distance from a sun that it's neither too hot nor too cold for liquid water. Now they've found three orbiting a single star that's not too far away in galactic terms. The Gliese 667C star, found 22 …
"...ten times the mass of our home planet."
Goldilocks had better have some muscular calves if she wants to be sauntering around that neck of the woods.
I don't know about you guys, but for me, that little spec deviation knocks the 'habitability' of these rocks right down to around "Detroit" level.
My friend, Mr E. Coli, disagrees with you.
Rather more seriously: my definition of "habitable" would be more stringent than yours (1-2 terrestrial masses, not tidally locked, must have a moon, must be in a conservative habitable zone on a star that has stable output over billions of years, must have an orbital period of order 12 months and a rotational period of order 24 hours - basically "identical to earth"). That's why looking for life on Mars and further out in the solar system is important: we need to understand whether those constraints are pessimistic. And if we find life on Europa, we need to understand why it's not evolved into something we can have a conversation with.
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For two objects of the same density, then the surface gravity is proportional to the radius of the object, not it's mass (gravity follows the inverse-square law). It is thus proportional to the cube root of the mass. Therefore the surface gravity is about twice Earth's (assuming similar composition). Which is entirely survivable for fit humans.
"Fortunately, we know that this state can still support life." In theory, surely? It's not as if there is any hard evidence of life discovered on tidally-locked worlds yet. If one side resembles Riddick's Crematoria and the other side is more like Hoth at midnight it might be harder to colonise since the habitable zone might be a bit narrow...
Fortunately, we know that this state can still support life.
If it is a theory! I was going to post a similar comment, but mine was going to be much more conspiracy based along the lines of...
..They slipped up they have revealed they have found alien life and are harbouring secret discussions with ten armed worms that talk through their arses!
But then I would look crazy, wouldn't I?
Well, you have to consider that gravity doesn't just get cancelled out just because you're under water. Don't forget that you need to add up the total weight of the atmosphere *and* the liquid water above you. Some forms of life on Earth can tolerate extremes of pressure, but who knows if life could actually have started under such conditions.
Also, to be totally pedantic, just saying the planet is 10 times more massive isn't the whole picture. We also need to know what the planet's radius is. If it's large enough, the surface might have a tolerable gravitational force.
When the aquatic organism is mostly water anyway, I don't see why the pressure alone would be a problem (within reason; I guess at some pressure the water would turn into solid). Diving humans have problems because we have gas-filled cavities, but in watery organisms living in the depths, the pressure from the surrounding water is countered by the pressure of the water inside the organism.
"We also need to know what the planet's radius is. If it's large enough, the surface might have a tolerable gravitational force."
I think the clue is in Earth sized rather than massed. I'd guess they normally refer to surface gravity when they give numbers like this.
IIRC bigger sized planets EG Jupiter sized, would have been spotted much sooner.
I'd guess they normally refer to surface gravity when they give numbers like this.
In this case, it would be problematic. We're talking about the Keck's HIRES program, which detects planets by looking at the wobble of a star (radial velocity) via the Doppler effect. This is being reduced to the classical problem of two bodies (amended Kepler's laws) to obtain the rough estimates of the masses, along with the orbital data. There is no way you can determine the size of a planet in here though. You need another method, like eclipsing or transiting the star by a planet. A (relative) size can be estimated along the orbital data, plus you might be able to tell what materials the planet is made of and say something about the atmosphere. If you also are able to find the mass via star's wobble, you get the g and density.
Otherwise, by only transiting method alone, the mass cannot be estimated reliably unless the planet is pretty big (a giant mostly made of hydrogen) and is pretty close to its star. I presume here, you need to have the temperature as well, to get an idea of how much it is squeezed by the gravity, e.g., a brown dwarf more massive than Jupiter would likely have a smaller radius.
Surface gravity? Do you mean acceleration due to gravity on the surface?
As was pointed out by Colin Miller above, assuming the equal densities (and spheroid shapes) of two planets makes the g on the surface of a planet be proportional to the radius of the planet, i.e., to the cubic root of the mass. Since
g ~ M/R^2 and M ~ R^3 yielding g ~ R ~ M^(1/3),
where R and M are the mass and the radius of the planet, resp. Hence we get 10^(1/3) \approx= 2.1544. So it's 2.15g .
Psst...it says "up to" 10 times the mass of Earth. The other 2 both have lower masses.
In fact, the prime candidate, planet f, is only 5.68 times the mass of the earth. If the diameter of the planet is 2.4 times that of the Earth, it would actually be slightly LESS than 1G.
Unfortunately, it may be awhile before we know the actual size of the planet. Especially to any certainty. However, this clearly shows that as it stands right now, it's a great candidate for life.
As zemeric points out a bit bigger (and I think that might be in the "experimental error" range) could still give 1g (it's "little" g, not big G we're talking about).
And 22 LY is a lot closer than most of these candidates (IIRC the last one was 100LY+ away) so perhaps close enough for some people to start asking "What's it take to do this?"
Thumbs up for a positive use for data mining.
And 22 LY is a lot closer than most of these candidates (IIRC the last one was 100LY+ away) so perhaps close enough for some people to start asking "What's it take to do this?"
I say we send a ship called Icarus, commanded by someone named Taylor.
What could possibly go wrong?
Henry VIII ordered the planting of the new forest so that his successors 200-300 years down the line would have enough material to build their ships. Now, in the end it didn't exactly turn out that way, but +100 points for the long-term thinking.
Same here - rig up something Voyager-like and send it on it's way. Sure, maybe there won't be any results for a few hundred years, or maybe never at all, but the development and knowledge gained to get it done and to see what happens as it leaves the solar system and goes interstellar would still be worth it.
I have sometimes wondered if there could be a X-Prize type thing for a "space dragster"? The goal would be to accelerate some macroscopic object (even if only the size and mass of a pea) to a relativistic speed in space, let's say c/10. Any propulsion method allowed. The only requirements are that the probe must contain a radio transmitter of sufficient power, so that it can be tracked and the final speed verified, and the top speed must be achieved within some reasonable time, like five years.
Why not send a number of probes out on slightly diverging vectors, forming a very long baseline optical/radio telescope, with the center probe aimed at the system.
Then we would start to get massively improved resolution very quickly, and first hand data 22 years after the center probe got close.
It would make the mission a lot more compelling, don't you think?
Peter
They’re dangerous places liable to get hit by flying objects or be damaged by the local star having a fit, subject to wild climate swings, etc.
Instead, build our own worlds inside large, spinning asteroids. Start with Larry Niven’s idea of “blowing” an asteroid by filling a tunnel full of bags of water, spinning it and directing sunlight from mirrors onto it enough to make it molten. Once it expands, let it cool off and then make it into an inhabitable worldlet similar to the “Stone” from Greg Bear’s book Eon (without the hyperspace tunnel, of course!). You can have any length of day or “gravity” (from centrifugal force) that you like. If the sun gets testy or a swarm of flying objects are coming your way, you can move it. Wouldn’t take any more technology than we’d need to build ships capable of relativistic speeds, and we can do it right here. And, if you can make it self-sustaining for long enough and come up with a drive, you could convert some of these into starships –even use a multi-generational model that takes hundreds of years to reach a destination.
`Wouldn’t take any more technology than we’d need to build ships capable of relativistic speeds'
If only you really were trolling. The one is far closer to practicability than the other ... can you guess which? Sure, that might change if the right trick that works on the right (as in macro) scale is found or donated/left behind by aliens, fantasy territory, not that some writers haven't used some deus ex machina to good effect.
The self-proclaimed boffin who, apparently straight-faced, claims that we have proof of the possibility of life on tidally locked worlds really needs some fantasy cake to live on for a bit.
Sorry, I don’t see how making a habitat more difficult than making a starship.
Radiation? You have that in space, either way. A habitat as I describe would have walls many meters thick. Plenty of shielding. Can you put that much shielding on a starship? (And unless you have working “deflector shields”, let’s leave those out of the discussion.)
Ecosystem? How fast could the fastest starship we could build now go? An Orion with a top speed of maybe .03 c? Well, let’s be generous and say .1 c. So it’s 40 years one way to Alpha Centauri. How were the astronauts (taikonauts, etc.) going to breathe, eat, etc.? You’d need SOME SORT of ecosystem on that ship. And a habitat as I describe would be a lot bigger than your typical starship, so you’d have more room to spread out which would likely help with the issues we have with artificial habitats. Yes, the closed ecosystem issue is a large one and needs A LOT of work, I agree. But it’s an issue that needs to be solved with habitats or ships, barring some magic “warp drive.”
Unless we discover some new physics that makes FTL travel practical, I think the human race will build habitats throughout the solar system, and eventually, some of them will go to other stars.
So from where does the energy to drive a large object with thick rock walls into interstellar space come?
Without the sudden discovery or gift (neither very likely IMHO) of a new technique to get immense spatial displacement for little cost in energy. it has to be incremental, until people can at least work out how to run a viable and largely non-dependent outpost under the relatively known and benign conditions of Mars.
Meanwhile, thanks to a large and irresponsible arc from Afghanistan, throgh Bangladesh to South Africa, and, including India, the exponential population growth continues apace, as does the profligate waste by the privileged everywhere (stand up Al Gore, the Google management, and UAE high-ups on this point, just as three choice examples, the reader's own wealthier neighbours might do just as well).
Population of 8,000 million is not far off.
There will be a breaking point, when it is clearly visible and how much remains possible after that is impossible to predict, to paraphrase Lovelock, if this situation collapses, no sites will have oil bubbling to the surface, no readily extractable bodies of metal will remain.
Sure and all, garbage mining will have its day.
Good luck with getting out into the solar system after the human population hits say, 10 or 11 thousand million, neither too distant if present trends continue, and there's nary a hint that they won't.
BTW, don't take my comment in the wrong way, I'm strongly in favour of humanity making viable habitats off our our still-lovely home world, but three factors remain insurmountable:
radation and protection against that
no closed human-made ecosystem so far has survived for long (yes, I am aware that somewith exclusively aquatic organisms, and a very limited set of species have done alright, but not indefinitely). Withhumans and many otherterrestrial species in the mix, failure has always been too quick for use in a viable outposton Mars.
many elements of humanity being led by atavistic pseudo-religious leaders who treat everytning as a demographic war and invasion (and no, I'm not talking about the Catholic Church,nor the Iranian state).
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