# Are You Out There, ET? Searches for Habitable Planets Are About to Get a Boost

A Q&A with stellar and planetary scientist Alan Boss about the holy grail of extrasolar planet research--finding Earth-like planets

The Kepler satellite, which will seek out those habitable planets, launches March 6. What do you think it is going to tell us?
I'm betting it's going to tell us that Earths are quite common. Kepler's going to be looking at 100,000 stars for three or four years. We expect that Earth-like planets will have their orbits aligned in such a way that basically one out of 1,000 can be seen by Kepler. So if every single star has one Earth-like planet, that means that Kepler will see roughly 100 Earths. But if it turns out that we're wrong and, say, only one out of 100 stars has an Earth-like planet, then Kepler might find one Earth—if it's lucky—or it might find zero. And if Earths only occur around one out of 1,000 stars, we'd have to be really lucky for Kepler to find anything at all.

So Kepler basically assumes that it should be able to find some Earths as long as they occur at roughly a 1 percent rate or higher. There's a very good chance that Earths are available essentially all the time, but we can be a little bit conservative and say that Kepler should find dozens of Earths.

If Kepler does find a number of Earth-like planets, then we'll know how many there are in general because Kepler will have searched such a large sample. And then we'll know how to go about planning the next phase of the search, which is to search the nearby stars. Kepler's going to be searching stars hundreds of light-years away all in one direction of the sky. It's sort of like after looking at another neighborhood in another city, we want to then look at our own block. Kepler will tell us how many houses we have to search on our block to look for life.

Given that our planet is the only Earth we know of, how can we extrapolate how many Earths there should be out there?
First, if you talk to astronomers who look at young stars, they will tell you that when stars form, they tend to have a little bit of angular momentum, which means that they can't accrete all of their matter and they end up having a disk around them. Such disks are what planetary systems form out of, basically the leftovers from the star-formation process. Essentially all young stars have these disks, so we expect that these young stars at least have the possibility of having planetary systems.

Second, those who worry about planet-formation processes find that it's very hard to stop Earth-like planets, or some sort of large, rocky object, from forming. Earths in some sense are easier to build than Jupiters, but we already know from our extrasolar planet census that Jupiters exist around at least 10 percent, and probably around 20 percent, of stars. So Earths should be even more common than that.

Finally, and even more directly, the planetary searches are already beginning to find a new class of planets called super-Earths with masses maybe five, 10 or 15 times the mass of Earth that orbit a little closer to their star than our planet does. These guys occur on roughly one third of nearby solar-type stars. And these are sort of the oddballs in some sense, which I think are very much just the tip of the iceberg of the spectrum of Earth-like planets. In any theoretical model of planet formation that people talk about, there should be a ton of Earths compared to these oddball super-Earths, so when we do a complete census we should find a lot of Earths. If these oddballs are there 30 percent of the time and the Jupiters are there 20 percent of the time, that means the ones we can't quite see should be there essentially all the time. So it's a very compelling story, and all the evidence from several different directions points toward Earths being quite common.

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1. 1. GLM2001 08:21 PM 2/27/09

Did it ever occur to anyone that sending this stuff out into the heavens might be the equivalent of sending inter-galactic spam? As much as I would love the make contact, I think the chances of encountering another civilization at the same technological level and the same attitudes as ours is too far remote to spend on this effort. The assumption that an intelligent civilization must have technology like ours is very narrow minded. 2/3 of our planet is covered in water, if intelligent life arose in an ocean or in the clouds of a gas giant like Jupiter, of what use would the wheel or fire have been to them. They would develop an intelligence far different from anything we can begin to imagine.

2. 2. GLM2001 08:49 AM 2/28/09

Well, looking at my post above and I see it really has nothing to do with the article. For some reason I was thinking of the SETI project when I wrote the comment.

3. 3. Martinius 08:56 AM 2/28/09

GLM2001, I must disagree with you. Look at the numbers, what if only 1 civilisation is similar in it's tool-making and problem solving skills and has had access to common elements like iron, silicon etc.. like we have. Imagine our civilisation's technology in 100 years: Genetic medicine, nanotechnology, artificial intelligence will have combined to make US biologically immortal at least. Imagine an alien species only 10,000 years more advanced than us. Imagine the possible technologies, imagine their mastery of matter and energy (yes, also imagine their cold, ruthless, alien minds and their alien goals and behaviour if you want). But open your mind and fully appreciate the possibilities. By the way, we're not sending any 'stuff' out there, we're watching and we're listening. All it takes is 1 signal with information (a la "Contact" by Carl Sagan) to change our civilisation for ever. Look at the numbers again - even if we do find nothing that's significant in itself - learning that this 'reality' we perceive is really unique. All the scientific evidence suggests that 14 billion years ago there was a 'big bang' event. The universe has expanded and evolved to a point now where it is aware of itself through us and our minds. By perceiving and thinking, our minds (as small parts of the universe) can become aware of the whole - like I said, the universe is self aware through us. When a human gazes out at Andromeda in the night sky there's a link, a connection made between 2 entities millions of light years apart. That we can even think these things is amazing enough but I think it also gives us good reason not to take things for granted and imagine we know it all. As humans, we're inquisitive and optimistic and brave and cunning. Millions of us travel every year to sit on beaches and stare at the oceans or gaze at the stars or head off into unexplored wildernesses. We keep exploring and enquiring because that's what drives us. I think there's room for a bit more optimism my friend.

4. 4. David Laurie 08:38 AM 3/2/09

It is just my opinion. But we probably need to work on governing ourselves better and not destroying this planet we have been given before we venture out into the Universe. It is important that before we announce ourselves to the Galaxies that we have at least a minimal ability to DEFEND ourselves and this planet. I agree with the other poster, folks, wake up, there could be many countless planets with life and "aliens" with technology that far transcends our abilities to even understand or comprehend. Take time travel and suspended animation and terra forming and throw in Tesla's Death Ray. "It ain't all roses and chocolates out there". Most people would already be digging holes in the Earth to hide in if they even had a clue of what could be out there.

Instead of Mankind standing together as one we fight each other and have petty differences and wars and hate each other because we all have differing beliefs in Supreme Beings or not. We are ruining this planet yet have hopes of finding another. As a species, we cannot even crawl, yet want to peer outside our crib and dream of the possibilities. We are all naieve.

African Americans were enslaved and brought to America. We should focus on the survival of Humankind and be prepared to defend ourselves and we should start today. Being enslaved by "Aliens" or killed by their biological weapons is not something I want my Grandkids to experience.

Personally, I am all for exploring the Galaxies and the stars and finding all of the habitable "M" class planets. But let's take our Phazers guys, just to cover all the bases. All the "I Love Lucy" reruns are already on their way announcing our existence. Time is elusive and the clock is ticking. The difference between the past, present, and future, is only an illusion, however persistent. Albert Einstein 1955.

5. 5. David Laurie 08:49 AM 3/2/09

Have a nice day...

6. 6. Cerebral*Origami 10:32 AM 3/4/09

I seriously doubt we'll ever have any visitors or go visiting ourselves.
The distances are just too vast. The only way any kind of interstellar travel would be feasible is if we were to invent some sort of receiver-less form of teleportation.
As for defending ourselves if we were to be visited by hostile aliens - forget it. We live at the bottom of a deep gravity well on a surface that follows a very well defined path. They could simply send in a decent sized asteroid at .9 c and we could never stop it. The best we could hope for is to have a wide spread space presence throughout the solar system so that a single large scale event (Short of our sun going nova) couldn't wipe out the human race.

While I would love to see us finally start a real space program with manned colonies first we need to get the world in order.

We need to unify the planet.
We moved beyond family groups, then beyond tribes, past city states and grew out of single states to nations, it's time to move beyond nations and become one people looking out for each other, supporting a global revolution to give everyone plenty to eat, safety, good health and a high standard of living.

When we have completed this, when we have gotten our own house in order, THEN we should look outward and launch ourselves from this world as a people united and working together.

7. 7. Kopak 01:48 PM 3/4/09

Hoo-hum and away we go! If you believe in a creator like God or intelligent
life. Then you need not second quess the probability of other advanced intelligence. What would be the purpose in creating dead planets; a whole universe for that matter? What proof do we have that this world isn't being
monitored by higher advanced intelligence? Maybe we aren't ready at the right frenquency. I believe we will discover intelligence else where and that humans do exist in and on other worlds. Once this awakening happens, we will be glade to call Earth our home. The key for opening this new door will be abandoment of selfish and bias double thinking, fears and ignorence. Learning more how to articulate his understanding the universal life principles and energies that govern this universe will be the biggest giant step for mans inlightenment of other worlds and understanding that there are higher intelligent beings waiting to let us know we are not alone.

8. 8. Pacetum 06:31 PM 3/4/09

I believe it is possible to travel between the stars and galaxies. The solution is to use the hyper-space. Through the normal space is not possible. I think that through a very strong electromagnetic field it is possible to distort the space, or you speed up the spaceship for high frequency.
About aliens, they are already around us, from the most ancient civilizations in that Galaxy. They may exist in higher frequency dimensions, like the spirits. I believe that the older religions speak to us about them. This is what the Science must follow.

9. 9. sciencereader104 02:45 AM 3/5/09

There has to be life on other planets. For centuries mankind has put itself at the center of the universe and created our own gods to worship to make us feel so important. The odds of any form of life to be at the current human level I would guess to be very slim. Just a few thousands years of evolution would be make a big difference, let alone millions of years. But just as there are millions different life forms on Earth there has to be millions of life forms on many planets within the "Goldilocks" zone that contains water. We just have to find them to prove it.
As far as never being able to reach them I believe is a wrong conclusion. Merely 500 years ago if you told people that someday you could pick up a small metal device and pushed about dozen buttons you could instantly converse with someone in China, Italy, or almost anywhere in the world they would think that you were crazy. What if 200 years ago you told them that men will soon someday walk on the moon and return safely to earth.
Supposedly nothing can travel faster then the speed of light but someday there may be away to get around that somehow possibly by shrinking the space in which one has to travel just as space was possibly expanded after the Big Bang.

10. 10. LarianLeQuella 06:56 PM 3/9/09

The biggest impediment we have to really understanding the possibility of any intelligent life is that we only have one datapoint for any type of life at all. Most people (scientists fall in that category as well) tend to think all too earthcentrically in this regard. Of course, we are lacking a great deal of information to realistically break out of that particularly centric mode of thought. To cast about for every possibility isn't reasonable either, so we go with what we know.

There is a very interesting discussion going on over at the JREF Forums about this very topic.

Some other things to consider:
- Our "I Love Lucy" episodes may be 60 light years out there, but due to the inverse square law, they would be barely detectable by even our own Ariceibo Observatory if it were located only 4 light years away.
- The volume of our won galaxy that we have actually looked for planets in is less than 0.05%.
- The bias for finding large gas giants close to their respective sun is due to the detection methodology we have available to us right now. If you are only able to see one type of thing, then that's generally what you'll see. ;)
- Keep in mind that Kepler will be looking for transiting planets. If the orientation of a solar system is not lined up to our plane of view, we won't find anything there with this instrument.

Sometimes the three most powerful words in the English language are, "I don't know." Not knowing is what drives us to find out!

11. 11. Sloan 08:36 PM 7/29/09

This is the way I see it . The Cosmic Mayfly From deep under the oceans, far from any sunlight, to high up in spewing volcanoes, life-forms have been found on our planet. Even deep in the arctic ice, life-forms have been found to exist. For life is tenacious, if it can exist it will exist, this is the way of nature. Soon, yes very soon, I’m sure we will find life-forms on other planets in our solar system. Indeed I’d be very surprised if the whole universe, were not teaming with some form of primeval life or another. But will we find intelligent, alien life in the cosmos? This is a very different thing. Yes I’m sure intelligent life has existed in the universe at one time or another, but does it exist right now, at this very moment, in our time? Cosmetologists’ and Mathematicians calculating the endless galaxies’ in the universe, with their countless suns, and infinite solar systems with literally, trillions and trillions of planets, will know-doubt say. By the laws of probability there must be many planets, orbiting far-off Suns not unlike our Earth, where intelligent alien life, could well have evolved. It’s even possible some of these solar systems could have two planets, with intelligent life-forms living on them, though not necessarily during the same time period, nothing is entirely impossible. So why haven’t we heard from any of these, alien intelligences? Is it perhaps, simply down to the vastness of space!, the unimaginable distances between the galaxies. Some star systems are Hundreds, even hundreds of thousands of light years from our own galaxy the Milky Way. In this infinite universe, any forms of signals or transmissions may, barely have left their back yards, or indeed in our case, our own back yard! Life forms, bacteria and Algae, first appeared on our Earth approximately 2 Billion year ago. It’s only in the last 100, two 200,000 years that intelligent man has so very, quickly evolved. With mans rapidly developed technology, and nuclear weapons. I fear we are like monkeys playing with grenades, unable to comprehend the science we have so quickly mastered, and here I think could well lie the clue. Perhaps all intelligent life has a built-in obsolescence. Many alien planets could have had highly developed technologies, only to destroy themselves, when they developed nuclear or biological weapons. If MANKIND could only have watched, some KIND of TIME-LAPSE MONITORING DEVICE, from the very beginnings of the universe. The very moment of creation, just what would we have seen? Yes, Millions of galaxies forming over endless trillion of light years. Expanding, dividing, and colliding, at this very birth of the universe. Taking snapshots every million o-so light-year, perhaps the device would have detected Radio or TV signals, or a nuclear explosion, in some far of constellation, indicating intelligent alien life, had reached an advanced stage of technology. Some snapshots would I’m sure, have revealed many planets with intelligent, evolving life-forms. A snapshot a few million light years later, with very few signs of intelligent evolving life. And this may well be the case right now, at this very moment in our own, small corner of the cosmos. We could really truly be, on our own. 200,000 years of mans existence on our small Planet Earth, is a mere day in the history of the universe. Like the Mayfly that soars in the sky, for its one brilliant day in the warm spring Sunshine. Man could well be the cosmic Mayfly, soaring into space for one brilliant day in the cosmos, only finally to fall back to Earth to die. This may well be mans destiny. The chances of other intelligent life-forms nearby, existing right now at this very moment, in our one-day in the universe, must be reasonably remote. I’m sure in later snapshots of the universe, when man has long become extinct. Intelligent life-forms will be detected in outer space, in some far, or not so far of galaxies. Only to eventually go the same way as man, after their one, or perhaps two, brilliant days in the cosmos.

12. 12. jbm 09:36 AM 9/16/09

Wow! This guy has some faith. We don't even know if life evolved here and he is saying it probably happened all over the universe as if it is as easy as 1 2 3. A planet does not = life. Ours is a privileged planet and the odds of finding another where the conditions for life are just right have got to be low. Then even if there are a bunch of these planets, the odds of life evolving are astronomical as any Origin of Life researcher knows.

There is absolutely no evidence for what he is claiming. All we have are 300+ planets discovered so far and of all of them, only 1 is rocky. And it is a virtual furnace, totally uninhabitable. The evidence seems to point in the opposite direction from his amazing faith. As of now, it must be said that he has blind faith. He is banking on chance. This is not science. I think it is something that deserves further research, but these kind of exaggerated claims do nothing to serve the purpose of science except make sensible people skeptical.

13. 13. jbm in reply to Kopak 09:57 AM 9/16/09

Wow Kopak! Interesting post.

Hoo-hum and away we go! If you believe in a creator like God or intelligent
life. Then you need not second quess the probability of other advanced intelligence. What would be the purpose in creating dead planets; a whole universe for that matter?

Psalm 19:1-4
" 1 The heavens declare the glory of God,
and the sky above proclaims his handiwork.
2 Day to day pours out speech,
and night to night reveals knowledge.
3 There is no speech, nor are there words,
whose voice is not heard.
4 Their voice goes out through all the earth,
and their words to the end of the world. "

You said: "What proof do we have that this world isn't being
monitored by higher advanced intelligence? "

None whatsoever. It is also just as likely that there is a Creator like the Bible says. It seems though like you would rather believe in aliens than a Creator.

"Maybe we aren't ready at the right frenquency. I believe we will discover intelligence else where and that humans do exist in and on other worlds."

Great so you have faith too just like me.

"Once this awakening happens, we will be glade to call Earth our home. The key for opening this new door will be abandoment of selfish and bias double thinking, fears and ignorence."

Why is the abandoment(sic) of selfish and bias double thinking, fears and ignorence(sic) a bad thing? Perhaps those are good things in the alien world? If so, maybe the key to our survival will be just the opposite. Being selfish might be important if we want to survive. Evolution is the survival of the fittest - kind of a selfish system if you ask me. So why in the world would you think that getting rid of selfishness is a good thing? Just curious.

" Learning more how to articulate his understanding the universal life principles and energies that govern this universe will be the biggest giant step for mans inlightenment of other worlds and understanding that there are higher intelligent beings waiting to let us know we are not alone."

OK, that's your opinion. I do agree that there is a higher intelligent being that exists. He has already let us know that we are not alone. He has already revealed His existence to us through His great creation. He has already shown His love to us by sending His Son to this earth. Remembering that the cause must always be greater than the effect, yes, the heavens certainly do proclaim the glory of God!

jbm

14. 14. hartson 05:04 PM 3/31/12

Humanity is passing through the adolescent phase of it's social development.We are coming together as a global community populated with but one race, human. When we have come into this unity, stop squandering our resources on killing each other and use our resources to the development of each person's abilities, then we will be ready for the alien anthropologists to introduce humanity to galactic federation of planets.

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