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M. Kornmesser / ESO
A cartoon view of the Milky Way shows stars bristling with planets. The planets, their orbits and the sizes of their host stars are all vastly magnified in the cartoon.
A statistical analysis based on a survey of millions of stars suggests that there's at least one planet for every star in the sky, and probably more. That would add up to 160 billion planets or so in the Milky Way.
"We conclude that stars are orbited by planets as a rule, rather than the exception," an international research team reports today in the journal Nature.
The estimate may sound amazing: Just a year ago, the world was wowed by the claim that at least half of the 100 billion or more stars in the Milky Way possessed planets, yielding a figure of 50 billion planets. The latest survey now suggests that there's an average of 1.6 planets per star system, which would work out to 160 billion. But perhaps the most amazing thing about the findings is ... astronomers don't find them amazing at all.
"I am not surprised by the numbers," Didier Queloz, a planet-hunter at the Geneva Observatory who was not involved in the survey, told me in an email. Back in 2008, Queloz was part of a different research team that concluded one-third of the stars like our sun harbored super-Earth-size planets — the kinds of planets that could support life.
Over the past couple of years, findings from a variety of planet-hunting missions — including NASA's Kepler space telescope, the European Space Agency's COROT telescope and ground-based telescope surveys — have reinforced the view that planets are plentiful.
"Results from the three main techniques of planet detection are rapidly converging to a common result: Not only are planets common in the galaxy, but there are more small planets than large ones," Caltech astronomer Stephen Kane, a member of the team behind the findings reported in Nature, said in a news release from the Space Telescope Science Institute. "This is encouraging news for investigations into habitable planets."
Six years' worth of data
The new findings draw upon six years' worth of data from two wide-field surveys known as PLANET and OGLE. These surveys use a network of telescopes around the world, scanning the night sky for very rare events in which the light from one star system is amplified by the gravitational-lensing effect of another star (and perhaps a planet) passing in front of it. This particular planet-hunting method is known as microlensing, as opposed to the transit method (which looks for telltale dips in starlight as a planet crosses its parent star's disk) or the radial-velocity method (which looks for the slight gravitational wobble in a star that has a planet in orbit).
A. Feild / STScI / NASA / ESA
This graphic explains how microlensing is used to detect planets. Click on the image for a larger version.
During their six years of searching, the microlensing researchers identified only three actual planets. But they combined those detections with seven earlier detections, plus all the data about non-detections, to arrive at an estimate of how probable it is that planets of different types would be found around a star.
They estimated that about 17 percent of the stars in the Milky Way should host planets in the Jupiter range (0.3 to 10 times as massive as Jupiter), 52 percent should have planets in the Neptune range (10 to 30 times Earth's mass), and 62 percent should have super-Earth-size planets (five to 10 times Earth's mass).
All these figures are surrounded by wide bands of uncertainty. For example, the researchers say their estimate of 1.6 planets per star system could actually be anywhere between 0.7 and 2.5. But the lead author of the Nature study told me that his team's estimate is the best guess yet.
"The average number we find is higher than estimates derived by other methods," said Arnaud Cassan, an astronomer at the Institut d'Astrophysique de Paris. That's because the microlensing method can detect planets as small as five times Earth's mass up to 10 times Jupiter's mass, in orbits ranging from 0.5 to 10 times as wide as Earth's. Other methods aren't that sensitive, Cassan said.
"If they could detect planets with a range farther out, our guess is that they would find more planets," Cassan said.
What are the chances?
The big issue would have to do with how precise the statistical analysis can be with such a small sample of actual detections. Microlensing events are so rare that coming upon even one is like winning the lottery, and that makes the numbers difficult to crunch. But after reviewing the Nature paper, Queloz told me that Cassan and his colleagues conducted "a very good statistical analysis of the microlensing surveys."
Whether the actual number of planets in the Milky Way is 70 billion or 250 billion, it's a big, big number — 10 to 30 planets for every human on Earth. And the number doesn't even count worlds that are less than five times as big as Earth (such as Mercury, Venus, Mars and our own planetary home), inside the orbit of Venus or beyond the orbit of Saturn (such as Uranus, Neptune and the icy dwarfs on the solar system's edge).
Still more revelations about planets beyond our own solar system are coming up this week, but the bottom line for all this is that there's a big cosmos out there — with plenty of opportunities for planets and even life to develop. And that'll always be amazing.
"We used to think that the Earth might be unique in our galaxy," Daniel Kubas, a colleague of Cassan's at the Institut d'Astrophysique de Paris and a co-author of the Nature paper, said in a news release from the European Southern Observatory. "But now it seems that there are literally billions of planets with masses similar to Earth orbiting stars in the Milky Way."
More about the planet quest:
- Three newfound worlds are smaller than Earth
- Flash interactive: How other worlds are found
- Two new 'Tatooine' planets with two suns
- SETI researchers check signals in exoplanet study
- Microlensing turns up rocky, low-mass world
- Cosmic Log archive on planets
In addition to Cassan, Kubas and Kane, authors of the Nature paper, "One or More Bound Planets Per Milky Way Star from Microlensing Observations," include J.-P. Beaulieu, M. Dominik, K. Horne, J. Greenhill, J. Wambsganss, J. Menzies, A. Williams, U. G. Jørgensen, A. Udalski, D.P. Bennett, M.D. Albrow, V. Batista, S. Brillant, J.A.R. Caldwell, A. Cole, Ch. Coutures, K.H. Cook, S. Dieters, D. Dominis Prester, J. Donatowicz, P. Fouqué, K. Hill, N. Kains, J.-B. Marquette, R. Martin, K.R. Pollard, K.C. Sahu, C. Vinter, D. Warren, B. Watson, M. Zub, T. Sumi, M.K. Szymanski, M. Kubiak, R. Poleski, I. Soszynski, K. Ulaczyk, G. Pietrzynski and L. Wyrzykowski.
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.
Leave a Comment:
So we discover our solar system is not unique and that the universe is perhaps teeming with life...and that somehow proves there is no God? Really? Seems quite a bit premature to me. Sure it expands upon the Earth centric views of early religion just as Columbus expanded on the flat-Earth views of early science. There is probably very little science could figure out that would convince me there is no God. I find it takes just as much faith to believe science can explain everything as it does to believe in God. In the end it seems a matter of personal choice. I chose God. Atheists, knock yourself out with your faith in science.
Computers aren't in the bible. I guess the science that created them, and the internet, is just bs and you don't believe in it. Awesome!
This is what I believe. In the beginning, God created all the heavens and earth. The entire universe and all life in it. The universe is probably teeming with life some as we know it and as we do not. However, I think that the Genesis account is most likely a metaphor. It was not meant to be a scientific text. It is a guide for man to learn about God. The bible tells us how to go to heaven. But science can tell us how the heavens go. There is no reason why science and religion must be at odds. All that we know about the universe is what we can see through telescopes, space probes and theoretical models. We still have much to learn. May God lead us on our journey of discovery.
I'll put my faith in science over my faith in a collection of short stories any day.
Of course Genesis is a metaphor, written by men to explain what they don't understand. Some people are smart enough to get this, yet they still cling to the belief in some sort of magical "afterlife". Humanities power of delusion amazes me. "Yes I know the bible isn't really true, but I still believe it"
The existence of life elsewhere won't prove the existence of a deity(ies) one way or another...though it would be interesting to know if they observe such things themselves.
The nature of science is such that 'faith' is not involved. 'Science' isn't a body of knowledge alone, but the process by which we narrow our areas of ignorance, and always subject to change. Concepts that can't be falsified are outside its domain.
The only thing that science takes 'on faith' is the assumption that the Universe is understandable. So far it's been a safe assumption. But in a manner similar to Gödel's incompleteness theorem, it's possible that there are scientific questions that aren't answerable within the scientific method. That would become a matter of Philosophy, instead.
Science isn't in the business of proving there is no God, it's in the business of discovering what is knowable.
"It is said that men may not be the dreams of the Gods, but rather that the Gods are the dreams of men." ... Carl Sagan
http://www.youtube.com/watch?v=RJLc6J4Uz-M
http://www.youtube.com/watch?v=W1GUhTBBUGM&feature=artist
@Ad'M
Great quote ..... thanks )
God bless America
there's only "one true living God"
Well, well well, the statistical analysis makes me think star trek.
Actually, it is more realistic to start a moon base before thinking about going to mar.
We have data on how human adjust to sub-zero gravity while in the International Space Station. ALthough our shuttle program has come to an end, ISS still stands. We can still get valuable data on the subject matter. With those data, we should be better able to determine whether a manned moon base would be the next step forward in space exploration, an effort among many others as we venture out to other parts of the solar system and within the galaxy.
Space race is still on, with china rising, and we are depending on Russia to go back and forth between the earth and the ISS, we better do something to get back into the race.
God bless america
Oh look, a fascinating article about astronomy. Let me get a comment in before the religious and anti-religious a**holes start beating their drums.
Oops, too late.
I don't see why this has to knock religion - religion just needs an update. If there is a God, he built a universe, not just a planet. If I were religious, I'd be pretty impressed by that and respect God even more.
God created the stars, too. Job tells us, "... Canst thou bind the sweet influences of Pleiades, or loose the bands of Orion? Canst thou bring forth Mazzaroth in his season? or canst thou guide Arcturus with his sons?..."
Yes, we should respect the Creator.
These always crack me up. Even if we did find something in the universe it will be the biggest let down to all the Green Martian flying saucer freaks. The non-believers will then claim that by finding some organism in space proves something (just because an astronut lost a booger back in 1985 that he picked inside the shuttle, lost in space, and found next week, doesn't mean life exists in space). Columbus wasn't some great explorer either, so toss out the history book made by Disney. He was looking for treasure so he could get wealthy, just like every space agency on Earth. Wake up, and find the truth.....and stay away from my planet cause I found it first!
The latest astronomical findings and the latest scientific findings are in no business of disproving the existence of the biblical God as of yet. I say this because the Bible is the only religious book with the God that claimed to had created the universe.
NOW:
There is a recent concept called the multiverse - the idea that there could be more than one universe. That's not new-new because heard about the concept at the imagine level. But my point to express is that multiverse is the only concept I know of that is not consistent with what the bible claims. {The bible did not say God created multiple universe} It will take generations and hundreds of years to figure out whether there is a validity to the concept.
Yeah.....and some guys (a**holes) have multiple families that dont know about each other....yet they were created. You know what you need to son. You know what you need too....
Where's my flying saucers freaks at?
Yeah and I know one planet that is extremely screwed up.
Crazy thought :-) Maybe the energy/soul/spark that makes life as it is can't "live" in this dimension. Maybe it has to clothe itself in an "astronaut suit" of sorts (an extremely sophisticated one that has blood vessels and evolves.) That "suit" could take on lots of different forms and live in many different dimensions. We may not be able to see other life even if it is close to us. Maybe in life we can sense by smell, touch, etc..... after we shed our earthly suit we become one with everything giving a more "4D" experience on many different levels.....
Well said! Make sure you take care of business wearing your earthly "suit" so when you shed it you can take your spark to the good 4D experience and not the hot 4D experience :-)
and what strain are you smoking for your pain.
Will do! :-)
Remember that the Milky Way is just ONE galaxy and the estimates are that there are billions of galaxies, and on every planet in every galaxy there is an OBAMA promising to give you more freebies if you will just give him your vote.
Okay,,, you just went on ignore.
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...
This is mind boggling news! Hoipefully humanity can get it's act together and stop the petty wars and work together. If we could all just come together and stop this competition based society and begin a collaborative one, where we all work together for the common good. Then and only then we can litterally reach for the stars.
The vast size of space is mind boggling i wouldn't doubt that there are other living things out there.
Give me supra-light speeds and then ... Pin-Ball!
And God Created EVERYONE with His Own Hand.!!!!!!!
What does this have to do with the article and space.
branxoz
And you believe this is true because your parents and other adults in your life told you that it was true when you were a child, and that is good enough for you. Never mind that the book Genesis was written approximately 3000 years ago by a person whose name none of us knows anything about, including his name (but I am pretty sure it was not "Genesis"). It took about 1500 years before some men got together and decided what old writings they were going to call "The Holy Bible" and that it was the "word of God". And, oh yeah, if you don't believe all of that, even the parts that defy the laws of nature, you are condemned to eternity in Hell and denied everlasting life and entrance to Heaven.
..... we humans have got everything screwed up here on Earth , why not go into space and screw up other solar systems ?
Or put another way about 1 trillion trillion trillion planets in the universe. Just THIS universe and there are trillions of universes. Oh god will just say this is blasphemy! Yes god you are.
Some people say that intelligent life on other planets, if it exists, must be demonic. UFOs are the "chariots of the gods," or the chariots of demons and the Antichrist, some people say. The Word of God does not mention intelligent life on other planets, after all, so ...
.... We barely have intelligent life here on Earth..... why else would anyone making less than $100,000.00 a year vote Republican ?
Easy, all those $100,000. people help pay my bills when i do work for them. It's called capitalism and it works for me, very nicely thank you!!
Shandril, are kangaroos and the duck-billed platypus mentioned in the Bible?
We can thank our lucky stars we lived during the best of times ever. Most of us are yet to explore our own backyards.
Space is waste. So called "space exploration" to date, has been all about military endeavors. Everything leads down a black hole. Space is wank.
Yes! And all the trillions of dollars spent on the study of space and other planets would have improved this little blue planet.
You can thank the space exploration effort for a lot of the technology which we now take for granted, most significantly for the internet by which you and I are now communicating.
this doesn't surprise me at all, as a matter of fact i think the numbers are much higher.
Once again,,,, how do we get there.
I say lets gather 10 percent of the useless people on earth and aim them towards one of the super earths.
That would just about cover the politicians all over the planet.
i want their job so i can use terms like seems, conclude, probably,estimate, perhaps,our guess , etc..... and still get paid big bucks whether their THEORIES pan out or not or if anyone will ever really know.hmmm... i guess i'm correct, now wheres my payday so i can keep concluding on various subjects about the universe? captain kirk knows more about outer space than these morons.think your employer would pay you for superfluous responses such as those?
There are no other humanly habitable planets anywhere in the galaxy. To prove me wrong you would have to turn 99% of this world into a complete pauper. If there are any advanced worlds out there capable of receiving our signals, by now they would have made up their minds.
It stands to reason that most stars would have several planets orbiting them, and at least one of them where life exist. Unfortunately, all these planets are liable to suffer many big disasters during their existence that don't allow the development of highly advanced civilizations that would be capable of roaming through space for the prolonged periods of time necessary for interstellar interaction.
☞ ♭♥ † ♪ ♫ ♪ ♫ " For the director of music. ᖯ ᖰ ᖱ ᖲ ᖳ A psalm of David. ♩ ♪ ♫ ♬ ♭ ♮ ¡¡The heavens declare ♩ ♪ ♫ ♬ ♭ ♮ the glory of God; ♪ ♫ ♥ †♫ ♬ ♭ the skies proclaim ☺ † ♪ ♫ ♪ ♫ the work of his hands!!!" ♪ ♫ ♪ ♫ ♪ ♫ ♪ ♫ ♥ † ♥ † ♥ ḮḗṡṳṢ loves You ☺☺☺ † † † †
ψαλμὸς τῷ δαυιδ, PSALM ❶❾:❶
Since it appears there are numerous (billions) of planets out there, perhaps we should look for a star and solar system with several planets that are still young enough, that by the time we arrive it will be mature enough to let us move right in! We could arrive in a dinosaur age and be the supreme beings of said planet. All we would need to do is sleep a really, really long time in a preserved state and hope our aim is true. However sleep is highly overrated. There better be decent satellite TV, HBO or cable in my dreams if I'm going to sleep for that long to get there. -max out