Each star in the Milky Way shines its light upon at least one companion planet, according to a new analysis that suddenly renders exoplanets commonplace, the rule rather than the exception. This means there are billions of worlds just in our corner of the cosmos. This is a major shift from just a few years ago, when many scientists thought planets were tricky to make, and therefore special things. Now we know they're more common than stars themselves.
"Planets are like bunnies; you don't just get one, you get a bunch," said Seth Shostak, a senior astronomer at the SETI Institute who was not involved in this research.
"So really, the number of planets in the Milky Way is probably like five or 10 times the number of stars. That's something like a trillion planets."
Of course there's no way to know, at least not yet, how many of these worlds could be hospitable to forms of life as we know it. But the odds alone are tantalizing, Shostak said.
"It's not unreasonable at this point to say there are literally billions of habitable worlds in our galaxy, probably as a lower limit," he said. "Maybe they're all sterile as an autoclave, but it doesn't seem very likely, does it? That would make us very odd."
Other astronomers maintain that we are odd indeed, and that increasing the known planet population does not increase the odds of finding intelligent life on any of them.
"The numbers are huge by any human standard, but we are still looking at only a tiny bit of our galaxy," said John Gribbin, an astronomer and science writer who just published a book called "Alone in the Universe." "[This research] does further our understanding of how things like planets form and how stars form, but there is a long way to go before we can say there is life on any of these planets, and further to go before we get to civilization."
The new planetary plenitude is derived from a six-year survey of millions of stars studied with an international network of southern hemisphere telescopes. Astronomers used a delicate detection method called gravitational microlensing, which is one of three trusty ways to find extrasolar planets. Kepler uses the transit method, detecting blips in star brightness as planets cross in front of them. Other observatories use the radial velocity method, measuring the wobble caused by the gravitational tug of a planet on its star. Both of these are helpful for finding planets that are either huge or hug tightly to their stars. But the gravitational microlensing method can be used to find planets over a wider mass range and a wider orbital distance.
It works by using the host star and its putative planets as a lens. The gravitational field of the host solar system magnifies the light of a star in the background. If the host star does have a planet, the planet essentially widens the lens, and this is an effect that can be measured. Such an alignment is incredibly rare, so an international team of researchers examined 100 million stars every night and noted ones with promising light curve amplifications, examining them in higher resolution. From 2002 to 2007, the team observed 500 such stars. In 10 cases, they could directly see the lensing effect of a planet. A statistical analysis showed one in six of the stars studied hosts a planet of similar mass to Jupiter, half have Neptune-mass planets and two thirds have super-Earths. Combining the results suggests that the average number of planets around a star is greater than one, the astronomers say in a new Nature paper.
"Together, the three methods are, for the first time, able to say something about how common our own solar system is, as well as how many stars appear to have Earth-size planets in the orbital area where liquid what could in principle exist as lakes, rivers and oceans — that is to say, where life as we know it from Earth could exist," said Uffe Gråe Jørgensen, head of the Astrophysics and Planetary Science group at the Niels Bohr Institute at the University of Copenhagen and an author of the paper.
With so many planets, it could be easy to assume the odds have just gotten much better for alien life hunters, but it's not necessarily the case because scientists still don't know what's necessary for life to form, said Paul Davies, a cosmologist and astrobiologist at Arizona State University.
"How much real estate is out there doesn't matter," he said. "My guess is there would be some hundreds of millions of Earth-like planets in the Milky Way, but that is no good to you if the probability of life forming on one of them is one in a trillion."
The lack of knowledge hasn't stopped scientists from making educated guesses, however — take the Drake equation, devised by astronomer Frank Drake in 1961, which seeks to estimate the number of intelligent civilizations based on an equation of assumptions.
"All of the work that has been done since 1961 when this equation was concocted has gone in the same direction, namely, that our situation here is not so weird, not so strange, not so bizarre, not so special," Shostak said. "We're not unique, at least astronomically."
We're just one in millions.
Incredible. My worry is that a civilization more advanced than ours will find us. Then we had better hope they are peaceful. Also, if the universe is infinite then how are we able to estimate the number of stars there are? How can we be sure there is not an infinite number of stars?
160 billion planets in our Milky Way galaxy, using our solar system as a model of average planet positioning if 1/8th of them have a planet in the habitably zone then there could be 20 billion rocky planets in the habitably zone in our galaxy or over 2 x 10²¹ rocky planets in the habitably zone in our universe.
Lower luminosity stars than our sun, Venus would be in the habitably zone, even lower luminosity stars such as red dwarfs Mercury would be in the habitably zone. Higher luminosity stars Mars would be in the habitably zone, even higher luminosity stars Jupiter may be in the habitably zone.
Sure we found gas giant planets orbiting their local stars closer in then our gas giants in our solar system but they may most likely have a number of planet size moons orbiting them like the planet size moons of Jupiter and Saturn's -- as a result even if the gas giants are taking the place of a rocky planet in a habitable zone of another star their rockier moons may be habitable.
Note by using 1/8 number as an average number of all the stars in our galaxy, although our star is an above average star it is still a more conservative number then 1.6. I am sure that 1.6 number will change to a higher number as soon as we get better instruments to see more earth size planets in our galaxy. The total amount of stars in our galaxy also changes according to who you talk to from 100 billion to over 200 billion...
I've been saying this sort of thing for years. This universe is too huge for our planet and species to be anywhere near unique. This mathematical probability just backs that up. Somewhere out there are millions of worlds that are similar to this one. Others that are completely different. All of which would harbor simple, complex, non-sentient, and sentient life.
And, to think, not too long ago in the 1990s when I read astronomy books, none really talked about planets outside the solar system to include the fact that scientists believed most stars to form without planets making ours and Proxima Centauri a bit special.
"Imagine what you know tomorrow."
Hold on a second cowboys... I think some of us are getting way ahead of ourselves. Just because all systems are thought to have at least one planet, doesn't really change the astronomical odds that have allowed complex life to form on our planet. Here are a few reasons why our earth has been extremely lucky, in a way that allows for complex life:
We are thought to be in the galactic habitable zone. If our solar system was too close to the center of the galaxy it would be in a much more dangerous place, with much more x-ray and gamma ray radiation, neutron stars, etc. Those things are typically very deadly for life as we know it. And if we were farther out in the galaxy, our planet might not have enough metal content for the formation of a rocky planet, much less one with a liquid core.
We have a great star. Our sun is not very large. The larger a star, the faster it lives... and dies. The cycles of stars going nova has to happen for enough time to create heavier elements in order for a system like ours to even exist around a sun like ours. If the universe really is 13 billion years old, it is likely that the first half (at least) of that history would have been impossible for complex life to form anywhere, as there were just not enough heavy elements in the universe for it. Not only do we have a great star, but we're in the "Goldilocks" zone around it, getting just enough heat and radiation and solar wind, but not too much.
We have a solar system structure that provides earth with some great lead blockers. The large jovian gas planets do a good job of sweeping the solar system of many of the comets and meteors and other junk that could otherwise continue to bombard an inner planet for so long that life could never develop (much less complex life) before the star runs through its life cycle.
Our planet is well-sized. If it was significantly smaller, it would have a much harder time holding on to an atmosphere. A smaller atmosphere would result in much more radiation on the planet, as well as a large amount of temperature variability. A smaller planet would also cool faster, limiting the life of (or preventing altogether) plate tectonics, which as essential for complex life.
We have a nice large moon, which no other rocky planet in our system has. It is theorized to be the result of an impact with a mars-sized body. That impact provided the earth's axis tilt and spin velocity. The the rotation velocity is fast enough to decrease the variability in temperature. If the planet only spun a quarter as fast as it now does, the temperature ranges from day to night would not be a nice 20-30 degrees, but 80-100 degrees per day. Hard to have complex life evolve if all the water on the planet freezes again each day. And the axis tilt provides us with our seasons, which provide added variability for evolutionary processes to occur. The large moon also provides for good tidal forces and is thought to have initiated (or contributed to) the large scale mantle convection that is so crucial to life.
Plate tectonics and core convection are important and rare. They only occur where there is the right chemical composition in the planet providing enough radioactive decay in the interior to keep the heat on, and where there is enough water in oceans to lubricate the process. The planet's magnetic field is produced by convection currents in the Earth's core and the field is absolutely crucial to life on a planet. Without it, the planet would quickly lose atmosphere (Mars lost all of it when they lost their magnetic field, possibly due to the core solidifying) and everything here would be as dead as it is on Mars.
So in the end, we're the benefactors of being in a great galaxy, in an acceptable place in the galaxy, far enough down the universe's lifespan, in a system with a small cool star that lives long enough for life to develop, in a system with big planets to clear away most of the junk, with lots of comets to bring our planet lots of water, impacted by a planet that gave us just the right tilt, spin, and the all important large moon, etc.
That is a LOT of very fortuitous factors, each of which has a relatively small set of odds of happening in any given place. But to have them all happen in the same place? I'm sorry, but I think that planets that can actually produce life as we know it are going to be extraordinarily rare. I'm not going to say that earth is unique, but I'm thinking that one tens of billions or one in hundreds of billions would not be a surprising number. Just guess (conservatively) the odds of each of the many factors, and multiply them all out...
Thats only the half of it, as stated above as we find more rocky worlds near their local star we are going to increase that number, but as I said before a habital world for life may not be near a star and as blessed as we are but hiding deep in interstellar space between stars:
Are we alone in the Universe, that’s a question that was asked since the first humans walked on the surface of the earth and still perplexes scientist today. Today other relatively new question modern humans have asked with more powerful scientific tools available is “If we look for life in our universe where would we find it?”
Currently scientists are zeroing in on a place called the habitable zone, a narrow location from a planets local star for water to form and run for billions of years similar to earth's history. The location of a rocky water world like earths would be restricted to a narrow zone away from a star. The model location of a habitable zone potential life barring planet would be dependent on several variables which include the local stars size, mass, age, radiation, organic availability and intensity for life to prosper there, or so it goes.
Jupiter and Saturn if viewed from another star system 20 light years away would be considered by us outside the habitable zone as humans has thought for hundreds of years before Pioneer, Voyager, Galileo, and Cassini. We now know that these planets moons have the most probable chance for life outside of earth in our solar system yet if we viewed them from 20 light years away using our current understanding of habitable zone we would dismiss them as a non-factor because of their location from our local star. Yet these potential life bearing worlds have something that all things with mass have, gravitational influences which create tidal forces on their neighboring worlds. Strong tidal forces causes friction added to the natural radioactive decay of its interior which promotes the heating of these worlds internally, in the case of these outer solar system worlds is enough heat to replace the external heating from a close stars solar energy.
What makes these outer solar system worlds so unique is that most of them don’t have much of an atmosphere or external heat source because they are far away from the suns solar influence. In the current idea of a perfect place to look for a world teaming with life is one that has an atmosphere that can support water on its surface. In our outer solar system water cant form on the surface because of the extreme cold surface temperature as a result we may only find life two of three places. Lack of a substantial atmosphere on most of these worlds restricts our search to finding life in the oceans below the ice cover and subterranean life in the muck below the ocean. On Earth life can be found everywhere we search, high mountains to the bottom of the oceans, two miles underground and even in the Antarctica.
The one ingredient we find in our outer solar system that these worlds are teaming with is organic chemistry where the inner planets other than earth barely have organic chemicals that can be traced on its surface, this is important because all life on earth are carbon base life forms. This lack of organics is partially blamed on the intense radiation coming from the sun, the earth's magnetosphere blocks most of the solar wind while it atmosphere blocks the intense UV’s, low energy neutrons, and x-rays.
Our moon and our sun tidal forces has been blamed by some scientist for keeping the earth iron core heated up. The moon is 384,000 kilometers from earth which makes its actual tidal effect on earth about ½ the gravitational field on Phobos, a relatively small moon of Mars. In fact IO the hottest localized heated world in our solar system is gravitationally locked by Jupiter but hundreds of thousands of kilometers away its other Jovian moons tidal tug of war such as Ganymede, Callisto, Europa with Jupiter have been blamed on the volcanic effect on IO through tidal heating.
There are some signs of a brown Dwarf star or Jupiter size planet in our Ort cloud slinging into our inner solar system 20 percent of the comets that we view as predicted by John Matese of the University of Louisiana at Lafayette with approximately a mass of 1.4 times than Jupiter. Although this hypothesis hasn't been validated by the scientific community yet the new space telescope, WISE, launched Dec. 14 2009 should be able to spot it if there is one of that size out there. Imagine if there are planet size moons of this hypothesis Jupiter size world like the ones orbiting Jupiter the tidal heat source could support an ice covered water world similar to Europa or Enceladus that scientist claim is the most likely place in our solar system to find life. In fact Europa or Enceladus gets more radiated heat from the surface of Jupiter and Saturn than they get from our sun. These two ice covered water worlds are just two of the many of our solar systems planetary moons now postulated to have liquid water inside their rocky ice covered cocoon.
In other words where there is strong enough tidal forces to cause a continuous heating of moons or planets there could be life. We may not find it on the surface but covered up under several kilometers of ice like extremophiles in the oceans below the North Pole. Tidal forces can occur anywhere even out in interstellar space between stars all it takes is one to two large objects, or two objects sufficient close enough to cause internal heating orbiting each other like Pluto and Chiron. Therefore we may find an abundance of life on other worlds on our way to these yet to find habitable zone planets and not find life on the habitable planet once we got there.
Remember intelligent life on another world may be aquatic marine life not surface dwellers like us. The obstacle to transition for aquatic life form to explore our universe would be much more difficult then surface dwelling creatures like humans, but if they have billions of years evolving then that bearer can be broken just like humans breaking the obstacle of space to explore the moon, from air to vacuum. We humans had it easy, Aquatic life forms in our outer solar system would have to go several steps further.
Most all the evidence for life bearing organic compounds are in our outer solar system. Except for earth, most all the water and water ice that exist is in our solar system. We have discovered several different ice covered water worlds in our outer solar system. We know that tidal forces can heat these worlds so oceans can lay beneath a sheet of surface ice such as Europa. We now know that you don't even need tidal forces to heat a world, internal nuclear furnaces have been found to heat small asteroids far away from large tidal effecting gravity wells and the sun causing volcanism on worlds so small that gravity can't hold the material on it once it erupts.
So to find intelligent life off this pebble we call earth look for all the markers of life as we know it, organic compounds and water. Where do you find that outside earth, far away from the sun in our outer solar system...
The two comments above are awesome, if you have the time to spare; I suggest you read on! Thx marcoreid and rlb2
Feed this into your Drake Equation.
So according to this our closest star Alpha Cenutri has planets yet we haven't been able to see them with Hubble. I've heard the brown dwarf in the ort cloud theory but don't really believe it. It would've been found ALTHOUGH I have heard that it is theorized that we did in fact have another gas giant in our solar system at one time. From what I've heard the model of our solar system works best when another gas giant is put in the model for formation.
Think about though, if the Milky Way has 160 billion planets the odds are very good that there are at least a few other planets where all the right conditions exist. When you consider that there billions of galaxies and if each galaxy has billions of planets, then I would say its safe to say that the conditions are certain to exist elsewhere. As I once heard, we are proof conditions exist. Think about it, on some other planet, they are having this same discussion as us.
Althouh marine life on another planet could be intelligent, I don't think they'd necessarily be more advanced. Imagine what life would be like if we didn't have fire. Nothing we have now would exist. Last time I checked fire didn't burn under water.
Science always asks "can we," but doesn't seem to ask "should we."
from BBC news "Every star twinkling in the night sky plays host to at least one planet, a new study suggests.
That implies there are some 10 billion Earth-sized planets in our galaxy."
they dont explain how they get to the 10 billion earth sized planets since we have only confired a handfull.
and I see TONS of sepulitive number that I am not really sure where they are getting them from.
"using our solar system as a model of average planet positioning if 1/8th of them have a planet in the habitably zone then there could be 20 billion rocky planets in the habitably zone in our galaxy or over 2 x 10²¹ rocky planets in the habitably zone in our universe. "
they have only found, what 2 out 1000+ planets in the "goldy locks" zone if I am correct. 1/8 is a WAY out of proportion. and our solar system is ANYTHING but avearge. for starters our star is in the lower 10th percentiles of size and energy.
I agree with marcoreid
while I am sure there is life out there. the condtiions on earth are rare as far as we have observed. like he said.
"Plate tectonics and core convection are important and rare." bingo!
"We have a nice large moon, which no other rocky planet in our system has. It is theorized to be the result of an impact with a mars-sized body. That impact provided the earth's axis tilt and spin velocity. The the rotation velocity is fast enough to decrease the variability in temperature...." bingo!!!
not to mention they think that the tides that the moon creates in the ocean "mixed" oceans required for the "creation" of life.
statistically life should be out there. but I think a lot of you are using REALLY wishful thinking and numbers.
also not sure if some one pointed this out. or the article (sorry I read two other versions not this one)
On AVERAGE, Every Star Has At Least One Planet, New Analysis Shows
well. look at our solar system. we have what 8 planets. sorry I have lost the current count. I am sure some out there have 20 or more!!!! remember we have a very small star. that still means that MOST have NONE!!!!
When and if humans find a civilization similar to ours on another planet in my lifetime my mind will be blown. We could finally throw out religion for ever.
"If Christ were here now there is one thing he would not be – a Christian"
I do not mind those people who wish to toss out religion. To me, religion is a human invention and is flawed as humanity itself.
Though, I still believe in God, Jesus and the Holy Spirit and the idea of spirituality. I do take ownership of my beliefs and I do not force them on you.
Enjoy your own life and take care.
See life in all its beautiful colors, and
from different perspectives too!
Science seems to finally be discovering what I , and so many others, somehow always "knew".
My whole life, theres never been any doubt that the universe is teeming with planets, just as I've never had a doubt that life is just as commonplace, as science will "prove" sooner or later.
That being said, its never taken away from my same knowing of God. Religion is simply a formal way of following God, and explaining in terms anyone could grasp. Why so many people try to use science as a means of disproving the existence of God, is to science, as those that kill in the name of religion, are to religion.
No one should use science as a way to dismiss God or religion any more than someone of one religion should feel threatened by another. Science and religion are more similar disciplines than most care to see.
I have no respect for people who believe in a fantasy and live their lives based on fairy tales.
"If Christ were here now there is one thing he would not be – a Christian"
Boka - I'm terribly sorry to hear that you have no respect for yourself... thats so very sad.
Whats even more tragic is your fear of the unknown combined with your blind faith in your own idea of science. The hypocrisy of your situation is truly astounding.
The objections/ prohibitions/ exceptions and possible exceptions stated are all subject to statistics. And if this piece is correct, the sample size was just increased dramatically. So if nothing else is learned, the potential for similar or nearly identical earths located in the anthropic zone has increased as well.
Your assumption is based on the concept that there is not a uniformity to the existence of the universe. How else would you explain celestial body formation, classification, and life cycles? Everything is not random in science. A good deal of it is uniform. For that matter, while the dynamic environment of any given solar system is unique, the necessity for life to form (as we do or do not know it) may not be so complex as the necessity of jovian worlds in a particular number, the type of star at the center of the system, the existence of a natural satellite by whatever means (transition and capture, impact event, or coalescing), or the size of the planet in question. It may be as simple as having a world in the right zone for the type of star it circles, the proper chemical mix to allow for the formation of a thick atmosphere and liquid bodies (water or not), and a strong enough magnetic field to protect against the bombardment of solar and cosmic radiation.
I'm inclined to believe we are not that special in the universe, let alone this galaxy. If that were the case, we'd have a greater measure of power and capabilities in our existence from the inception of our creation. In point of fact, on a galactic scale, we're probably about as unique as bacteria, and we're bound to find that anywhere in the universe, as we have found them existing in the most diverse of environments on this planet alone.
"Whether or not God exist is not as important as the belief of whether or not God exist."
It's not a matter of fairy tale or fantasy, but a matter of strength in faith. People put their faith in just about anything, which can be considered just as fallible as concrete devotion to sacred religious text. All things we put our faith in are of our own creation and thus fallible. Regardless, what you put your faith into should be strong enough to sustain you and keep you strong in this mortal coil. However, god (or at least the concept) is real. The fact that you are aware of the concept and a spoken word and idea for it is proof of that. Of course this is not to put emphasis on the dogmatic vision of an omnipresent, omniscient, incorporeal being from an ethereal realm. It is the concept born from the human psyche in our most primitive point of existence (which is argueable to say that we are still in) that has given us the structure for logic and a moral center, and thus a civilization and sentient status. By maintaining this mindset, we maintain the sentience of humanity necessary for our civilization (and thus continued existence). Without it, we regress back to an animal state and stagnate our ability to survive, much like the other species on this planet. Einstein said once "There is no darkness, only the absence of light... There is no evil, only the absence of God." as an issue of mindset. This can be applied to anything that you put your faith into that strengthens the foundation of human sentience. It's not necessarily about which religion is right or wrong, but rather people are aware of a central voice from within that gives them the intelligence, wisdom, and humanity we ultimately need to survive (that one's spirituality; a practice devoid of adherence to any particular religion). If we took this into consideration more often than who's religion is right, and what lifestyle you should live according to ancient sacred text, the concept of God would not be such a contreversial and frowned upon thing in the scientific community.
Another way to look at it; without the presence of what we call God residing in our minds giving us a conscience, the scientific community might be filled with a bunch of Josef Mengeles, without the promise of any real progress for the greater good of all humanity.
That is absolutely correct.
Boka is a life sucker. If you engage in conversation with him, later you will be wishing for the spent time you gave back.... you have been warned.;)
Science sees no further than what it can sense.
Religion sees beyond the senses.
Why would scientists ever think that our solar system was special? What were they comparing it to?
If our own star is the only example they had then it clearly shows that stars have many planets, and those planets have moons.
Now that we can detect planets around other stars it should just be confirmation of what we had only been guessing previously.
Also who says only one intelligent species ever evolved on our planet? Although (so far as we know) only one survived to become technologically advanced.
Why wouldn't intelligent life be as plentiful on other habitable planets as it has been on earth?
If all we are interested in is advanced civilizations, then yes, there may be very few or none at all near by.
But it makes no sense to continue thinking we are special when all evidence suggests we are not, and our own fossil records prove we were not the first people on this planet.
@ pheonix1012 - well said, could not agree more with your post.
@ killerT - Our own planet shows that life can, and does, exist in a multitude of environments. From areas such as volcanic vents at the bottom of the ocean, to the arctic.
Nature has shown us that it repeats itself everywhere, like a mathematic fractal. You look in the sky and see stars, around those are more planets, beyond that more galaxies with more stars, etc, etc. In fact, it very well may be that it works in both directions, both larger and smaller, no limit in either direction.
ever since was a kid i expected this theory to be true. the universe doesnt waste energy so no surprise that there are at least one planet for every star.
"religion is like a prison for the seekers of wisdom"
"When and if humans find a civilization similar to ours on another planet in my lifetime my mind will be blown. We could finally throw out religion for ever."
What shall we do about the religions that have always contended that there are innumerable planets like our own scattered about the universe? Or do you only pine for the debunking of the foundation of the religion that you abandoned?
Another thing worth noting:
This new finding don't begin to tell the whole story. Yes there is the drake equation but a part of the drake equation estimates the number of planets in our galaxy as being a fraction, hence the new finding 1.6 times that of all the stars in our galaxy. This being a good guess by current methods of detecting planets however that number will most probably change on the upside in a few years. Most all the extrasolar planets found thus far are gas giants larger than Jupiter. Jupiter has 2 planet size moons, Ganymede and Callisto and 62 smaller moons orbiting it. The second largest gas giant in our solar system Saturn has one planet size moon, Titan, and 60 smaller moons orbiting it.
We are mixing apples with oranges here but our current definition of a planet varies from as small as Mercury to as large as Jupiter, we haven't installed into this equation the planet size moons of gas giants. We also know from observation of our solar system that the more massive the gravitational well the more moons orbit our local gas giants. Jupiter is a gas giant that didn't make it as a dwarf star, it has 2 planet size moons and Saturn has 1 planet size moon. Most stars in our galaxy are dwarf stars, main sequence stars, that are much more massive than Jupiter and has a much larger gravity well. If using this analogy as a beginning point then dwarf stars, the smallest of all the stars projected gravity wells, should have 4 or more planet size objects orbiting them.
Our sun which is much more massive star than a main sequence dwarf star with a much larger gravity well has 8 planets orbiting it not 1.6??? Add to that we live in the outback part of the Milky Way galaxy where there are less area for planet formation and more area for planet size objects that may be lost in interstellar space in between stars...
Let's start at the beginning of the end. Rib2 says: "Jupiter has 2 planet sized moons". What happened to Europa? Hmm? Perhaps our most exciting and anticipated exploration gimmick is to find out if there is life in the sub-surface ocean of Europa! While the Drake equation goes a long way to debunk the theory behind this article, further supposition might modify the Drake equation to give us a better number than (N=10). While killerT's mention of our solar system being "special" does hit home with me (there are an awful lot of stars in the universe), maybe we are special to a certain degree. Yes we live in a habitable zone within the solar system, and our solar system is within a "galactic habitable zone", that still leaves a really LARGE number of stars within the habitable zone of the Milky Way. Now go the next step. The rough estimate of the number of stars in the Milky Way varies somewhat. (~250,000,000,000-400,000,000,000) Now the approx range of the GHZ in out about 8 kiloparsecs (25,000 ly) from the center of the Milky Way, with an approx width of 2 kps (6,000 ly). Andromeda has an estimated 1,000,000,000,000. ONE TRILLION!!! C'mon!? There is a neat calculator at http://www.quarkweb.com/civ/civcalc.html
that will let you play with some numbers. It's just a fun tool, but it does get you to thinking. Some numbers: based on a guesstimate of 10^12 stars in Andromeda, that gets you approx 33.6 BILLION stars in the GHZ that could be wet planets in the GHZ. Of those, 16.9 BILLION are in the realm of having physical conditions to sustain multicellular life. 804,000 would be around a star with favorable metallicity and chemical properties. Thinking about INTELLIGENT life, 51.5 are purported to have a chance for evolutionary success. While this number is infinitesimal re: the 10^12 number of stars in Andromeda, this is still higher than many would believe would be the case saying that our solar system is "special". And that's not even including the probability that life might require a different biological foundation to survive. Si instead of C based life; needing an O based atmosphere to breathe instead of, say Ar or N; or say, maybe even needing a corporeal form to even exist. So, it's silly at best to say that we are "special" or "unique" in the universe and that life most likely doesn't exist elsewhere. The are just too darn many stars in the universe to doubt that we are alone. Just ask Enrico Fermi. To paraphrase Carl Sagan: if we are alone in the universe, it sure is a terrible waste of space. Happy hunting!
I've tossed out human religions, but I do believe in God. The universe could have been random and chaotic, and some may argue that it is, but what I'm really talking about is the fact that things just seem to work. Bonding one carbon and two oxygen atoms gives you CO2. Lithium's amount of protons and electrons give it its distinctive properties. There doesn't seem to be any logical reason the universe would assemble itself in such a way, let alone any logical reason that this matter could have formed from literally nothing in the first place. Just my two cents, not trying to push my beliefs or anything. I look forward to the discovery of ever more astronomical wonders, new technologies, and hopefully the answer to the big question: Is there more life out there?
"The tides will come and go, witnessed by no waking eye"
We are dealing with time and space, and how long since then were these lands walked upon by dinosaurs? Our individual lives are little more than a blink of the eye. The trick has always been to survive long enough as a species until our light reaches them or until they reaches us.
inb4 ET built the pyramids: no u! lol :P
Musgeek wrote - Let's start at the beginning of the end. Rib2 says: "Jupiter has 2 planet sized moons". What happened to Europa? Hmm?
rlb2 reply - According to the accepted thory of planet size moons are those that are close to the size of Mercury or larger of which the three mentioned above are. Europa is also a favorite candidate of mine for possibility of having life it isn't however considered a planet size moon, it is even smaller than our moon. That being said if you're looking for an object big enough to harbor life any small satellite of Saturn's or Jupiter would do.
I'll bet that finding a star without a planet will be the hard thing to do.
So, rib2, not only can the IAU dictate what a planet can be (poor Pluto) but what size a moon has to be to be catagorized able to support life? This is really atrocious! If, for whatever reason, it can hold an atmosphere capable of supporting life, what does it matter how big it is and what they (IAU) call it?