It seems highly unlikely to me that we are anything special. We are only scratching the surface with the Exoplanet discoveries we have made to date. Kepler is only looking at a small area of 'sky' and yet it has found a large number of Exoplanets, and it can only identify a small portion within that area because it requires an exoplanet to pass in front of it's star when seen from the telescope's vantage point. The odds of finding a planet using that method are very slim, and yet many have been found using this way.

Exactly Paul. In a decade I bet we are talking about thousands of exoplanets. This can be the golden age of astronomy where we are actually searching for LIFE! Pour some money into astronomy education and divert some funds from wasteful govt. nonsense and put it into R&D for new generations of Space Telescopes. Let private companies build cargo/people carrying rockets, farm that stuff out, let NASA actually search for that special rock out there with new super powerful instruments. Is the JWST still going to go up?

BTW the Kepler mission is awesome. Amazing data it is pumping out. Who knew there were so many planets out there! I love it.

We need a way to filter out the light from the host star. Make a damn X-Prize for that and we are in business!

Jason

^This.

This is probably the most important photo of a century:
http://hubblesite.org/newscenter/archive/releases/2004/07/image/a/format/zoom/

Those are billions of galaxies.

Remember we are living in the outskirts of only one galaxy, itself consisting of billions of billions of stars, some with and some without planets - but the sheer mass makes the idea of us being the only life (however defined) in the universe a bit unrealistic. Will it be sentient, or will we even manage to see it if we found it - no idea.
The problem is, as Stanislav Lem put it, the "window of contact" in time, and space. Civilizations may develop into something that cannot be found or is not interested anymore in a civilization at our level, or it has already killed itself by wars, or it is so utterly different that we would not even recognize it, with the senses we have. It sound pessimistic, but indeed it's not - imho technology is not developed far enough now to predict or imagine other forms of contact.

Greetings,
Catfish

P.S. 50 new planets discovered in april 2012
http://www.youtube.com/watch?v=GeQkBwQPI-Y&feature=watch_response

"life" as in bacteria/ single cell mould, I'm with Gambit et al. There's been that kind of life on earth for many millions of years, before there was even oxygen (actually they're largely responsable for O2). I think there's a high likelihood.

"life" as in complex life plant/ animated beings... Good probability.

"life" as in higher sentience? I'm closer to Kontakt: Not very likely. Having a big brain is not a very common evolutionary strategy nor has it been a necessary one in previous eons .Cretaceous etc on Earth. I think we're the product of some very lucky coincidences. A very recent product at that.

With the latest data release, there are now 2321 planet candidates, and if you use the
Planet Candidate Explorer http://planetquest.jpl.nasa.gov/kepler
you can see that there are now a small number within your criteria. Check for example
Kepler number 2474:

http://planetquest.jpl.nasa.gov/kepler/detail/2474.01

There will never be many in this range in the Kepler dataset, as
it is right at the edge of this instrument's ability to detect. Particularly, for
a ~5500K star, the planet, to be at the right temp must be so far away, and @ <2M(e),
so relatively small, that the odds of it transiting from our vantage point become
vanishingly small. It is very impressive that there are as many in the dataset as there
are. It suggests that the actual number must be immense.

(This is why there are so many more K&M (orange/red dwarf) star planets seen in the
dataset. The red stars are necessarily small, and low mass, so the planets have
a large relative size and also orbit close in for habitable temperatures, thus
having a much higher likelihood to transit from our viewpoint. The detection method
is strongly weighted toward selecting large planets orbiting close, at high temperature,
around small stars.)

I think this is an important distinction- intelligent life on Earth appears to have evolved very late with perhaps not so much time left that the Earth will remain hospitable before it eventally becomes a Mercury like planet, on geological scales, the window won't last much longer; if Earth-like worlds are so common as is believed, if Earth is the analogy, then we should expect something similar going on with other worlds. In other words, time is not on our side to come into contact with these supposedly common, intelligent life forms given how large and how ancient the univese is, otherwise, why aren't we comming into contact with this already intelligent life that is supposedly so common and right next door? The evidence contradicts the theory- intelligent life is apparently so common, except for one hitch- it apparently is not.

As you state, the conditions that happened here seem pretty chancey- when you take into account the mose successful species in terms of numbers, such as protists, non-vertebrate animals, trees and plants, why should they evolve to be intelligent? Why should that necessarily happen? Selection pressures haven't went that way at all but for the last few million years. That's nothing in the lifespan of our planet.

It would be like a single lottery winner who won the the multi-state Powerball jackpot and says, "Hey I won the lottery, look how easy it is, why don't you win the lottery, too."

It's not a matter of thinking that we're 'special' in a teleological sense, that is, there is purpose or meaning to us alone that makes us special- but rather, just given the age and distances we're talking about, we're special in the sense that intelligent life isn't so common, otherwise, we'd be seeing it by now.

Star Wars and Star Trek give the idea that alien races are all over the place throughout the galaxy, certainly, we don't have that situation going on yet- why? From the supposition that intelligent life is so common and given the amount of time an older, more intelligent race should have evolved, perhaps this should be going on, but from our perspective, it's not, that's not the case. If on the other hand, they are analogous to us in the time it took for conditions to be like us, well then the odds are worse, if they're like us that it took so long for intelligent life to evolve and experience the technological barriers remain that prevent contact on cosmic scales, there's not much time left to find one another.

This is way cool. Let's sort through to find possible life giving planets! How should we sort the list to locate the ones closest to earth type?

I sorted by Temp, but I know its a combination of things. I'm having a little trouble understanding the variables in the downloadable spreadsheet. I have it in excel format now. Does anyone want it and we can plot where to base our first earth colony? LOL Serisouly though, let's have some fun with this.

Jason

I used table format, using the basic help information and the Data Column Names information,
and did a quick filter cobble of "Rplanet<2 AND Tplanet<320 AND 5000<Tstar AND Tstar<6000"

This can be abbreviated "Rplanet<2 & Tplanet<320 & 5000<Tstar & Tstar <6000", but note
that 5000<Tstar<6000 is not legal according to the help (though I didn't try it, actually).

Note also that as noted on http://kepler.nasa.gov/Mission/discoveries/ , the temperature
computed for earth is 255K, assuming a basic rock at equilibrium. It is the greenhouse effect
mainly of water vapour which gives us the actual average temp of 288K.

The sun has a colour temp of 5500K, just greenish of yellow.

I also did a computation a while back on the relationship between gravity, density and radius,
and also found that earth is density rho(ave)5.5, being ~9 for the core and 3.5 for the mantle.
This means it is unlikely but possible to consider a planet with rho(ave) considerably lower
than earth's. The relationship is g=GM/R^2, M=(4/3)*rho*pi*R^3, so g=(4/3)G*pi*rho*R, if I'm doing
this right, and so R goes as g over rho. So I considered rho(ave)=3.5 with g constant, then R
goes *(5.5/3.5)=*1.6, so you would get 1g @ r=1.6Re. I personally wouldn't want a planet with
more than about 1.2g. As g goes as R and as rho, for the 3.5 density planet you could have R=1.9Re,
but for a far more likely density similar to earth's, you wouldn't want more than 1.2Re.

The planet I highlighted is the closest candidate yet; it has T=263K vs earth's 255K, its star
is 5283K vs our 5500K, so a bit on the orange side, and its radius is 1.45 Re, so we might weigh
anywhere from 1.3 to 1.6 times our normal weight on its surface, if it has formed in the manner
of our system's rocky planets. See http://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_size

(The rocky planets and moons of our solar system divide distinctly between those with density around
that of earth @ 5.5, and those (all much smaller) with density ~3.5, such as our moon. The 5.5 density
is consistent with the aggregation of elements in the relative abundances typical of the sun and the
solar system as a whole (after shedding the lighter molecules of gases which cannot be held by these
small objects). The lower density moons have an anomalous elemental distribution which suggests they
may have a history similar to our moon, which is believed to have accreted from upper crustal material
from the earth which was shorn off by a collision, some time after the denser elements had concentrated
out of reach in its core. It is known that at least one planet which was large enough, and existed
long enough to fully differentiate into a crust/mantle and a core, was subsequently shattered, as
this is the source of the metallic meteorites. This would presumably have provided plenty of crustal
and mantle material from which these low density moons could have formed. All of this goes to suggest
that the earth's density is strongly likely to be typical for a planet of its mass or larger, until
the mass gets large enough to retain light elements, and thus no longer being a rocky planet, but a
small gas giant.)