Success: Kepler Lifts Off to Look for Other Earths
Written by Anne Minard
Artist's rendering of the Kepler mission. Credit: NASA
Kepler as it appeared moments prior to launch in Florida. Credit: NASA
NASA's Kepler mission lifted off without a hitch just before 11 p.m. local time Friday from Cape Canaveral Air Force Station in Florida.
The launch was a bit of a nail-biter, coming on the heels of last week's failure of the Orbiting Carbon Observatory, which plummeted into the ocean when its fairing malfunctioned. But everything for the Kepler launch — from the weather to the countdown — went flawlessly. At five minutes to launch, Kepler's rockets sent ribbons of smoke into Florida's 65-degree Fahrenheit (18-degree Celsius) nighttime air under perfectly clear skies. With 30 seconds left, confirmation commands were exchanged with practiced precision. The casing (called the fairing) fell off with grace, and three minutes into the flight, the craft was cruising away from Earth at nearly 7,000 miles (11,265 kilometers) per hour. Each launch event happened within three seconds of its predicted time.
Kepler's engines shut down at 11:45 p.m. U.S. eastern time, and the craft achieved separation just before midnight, about 62 minutes after launch. Now, for the next three and a half years, Kepler will trail Earth in orbit and stare at a single patch of sky in the Cygnus-Lyra region of the Milky Way.
Kepler fires the imagination, as it could finally address the age-old question of whether we Earthlings are alone. William Borucki, NASA's principal investigator for Kepler science, spoke about the mission at a recent NASA press conference and said if Kepler spies Earth-like planets in the habitable zones of other stars, "life may well be common throughout our universe. If on the other hand we don’t find any, that will be another profound discovery. In fact it will mean there will be no Star Trek."
The $500 million Kepler mission will spend three and a half years surveying more than 100,000 sun-like stars in Cygnus-Lyra. Its telescope is specially designed to detect the periodic dimming of stars that planets cause as they pass by.
By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles, allowing astronomers to confirm the presence of planets and use the Hubble and Spitzer space telescopes, along with ground-based telescopes, to characterize their atmospheres and orbits. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm the planets' presence.
Astronomers estimate that if even one percent of stars host Earth-like planets, there would be a million Earths in the Milky Way alone. If that's true, hundreds of Earths should exist in Kepler's target population of 100,000 stars.
Filed under: Extrasolar Planets, Missions, NASA
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March 6th, 2009 at 10:07 pm
HOORAY!!!
March 6th, 2009 at 10:11 pm
Schweeeeeeeeeet!
March 6th, 2009 at 11:52 pm
This is a great mission. <3
I watched the launch at nasa TV, I had it all under my control. :d
March 7th, 2009 at 12:04 am
Cool. Let's see if there's anything around 61 Cygni!
March 7th, 2009 at 12:16 am
(Stops holding breath) Yaaaayyyyyyyyyyyy!! Go, Kepler!!!!
March 7th, 2009 at 12:24 am
thnx for adding the Fahrenheit to celcius and miles to KM conversions, I hate trying to convert Americas measurement system.
March 7th, 2009 at 1:11 am
why Cygnus Lyra? because the Dude from there told us to look! Happy Days Kepler!
March 7th, 2009 at 3:47 am
Game on…
March 7th, 2009 at 4:37 am
The Heavens are filled with the seeds of stars, that form planets, which bring forth life, to evolve intelligence, that make sense of their being.
March 7th, 2009 at 5:20 am
Its a big ask – but will we be able to detect (through perbutations in the movement of these earth size planets) the presence of moons, of a comparible size to our own, orbiting these new earths?
I've always suspected that the moon plays a vital role in the evolution of life on earth – stabilizing our orbit and inclination, giving us tides which might play an essential role in the sea-to-land transition that evolving land based animals require, and (perhaps most importaqntly) helping to keep the planetary core liquified so that the planet has a long lasting magnetic field without which we would have no atmosphere and no protection from solar radiation.
We'll either detect earth-like planets or we won't – Profound implication either way!!.
March 7th, 2009 at 5:36 am
UK David, I don't think that Kepler will detect moons aroun Earth like planets since detecting Earth like plantes is already very hard to do. But science has ways to get new data out of older data in ways we could naver have predicted and hwo knows, some guy comes up with some analysis method that can extract data about moons in the Kepler data in the future.
March 7th, 2009 at 6:19 am
Good luck Kepler!
Hope to hear good news!
March 7th, 2009 at 6:43 am
Can't wait for the first confirmations.
March 7th, 2009 at 6:47 am
I think it's a big ask, to happen across systems aligned with their planetary orbits neatly occulting their primary for three years running. Statistically what are the chances of that happening even if every star had planets?
March 7th, 2009 at 6:50 am
Hooray! Exciting times indeed!!!!
March 7th, 2009 at 6:55 am
EXPECTED RESULTS (from: http://kepler.nasa.gov/about/ ):
Based on the mission described above, including conservative assumptions about detection criteria, stellar variability, taking into account only orbits with 4 transits in 3.5 years, etc., and assuming that planets are common around other stars like our Sun, then we expect to detect:
From transits of terrestrial planets in one year orbits:
About 50 planets if most are the same size as Earth (R~1.0 Re) and none larger,
About 185 planets if most have a size of R~1.3 Re,
About 640 planets if most have a size of R~2.2 Re,
About 12% with two or more planets per system.
These numbers come out substantially higher, when one takes into consideration all orbits from a few days to more than one year.
March 7th, 2009 at 8:00 am
I am excited about this mission but want to know something. Can anyone tell me if the stars they will be observing are A. Sun-like stars(g2v ect.) and B. will they be close enough to even realistically ever get there. I.E. within say 20 light years from earth.
March 7th, 2009 at 8:06 am
Hi,
Watched the launch from 65 miles south and it lit up the night sky and could be seen for about 4 minutes until main engine cut off.
March 7th, 2009 at 8:13 am
Awesome bill!
March 7th, 2009 at 8:54 am
Jason. Yes. Many different types of stars will be observed. The scope will be watching all of them, in it's field, at once. And No, they won't be close enough to get there. Even the closet stars are still beyond our reach. Four of our probes have left the solar system, barely, and it will take them a few tens of thousands of years to reach the equivalent distance of the nearest star.
March 7th, 2009 at 9:01 am
Space…The final frontier…
This is the mission of the space probe Kepler, its 3-1/2 year mission, to explore and find strange new worlds, to seek out…..
Now just waiting to see what the first results will be like, at least the journey has started.
March 7th, 2009 at 9:07 am
I understand all about distance, what I meant was future technologies, I am hoping, will at least get us between 10-20 light years. So I am interested in g2v stars within it's field of view at those distances. I know I will be long dead before anyone ever goes to them but at least it will give me some perspective on that possibility.
March 7th, 2009 at 9:20 am
Shaula Brant wrote
"Now just waiting to see what the first results will be like, at least the journey has started."
Expect hot Jupiters before anything else. These planets are the easy ones to find and confirm.
March 7th, 2009 at 9:29 am
Anyone know a list of G2V stars in it's field of view?
March 7th, 2009 at 10:07 am
Spoodle58 , the first results might take about 3 years. The planet should move in front of the star so it will take at least one revolution, probably more to confirm that it is a planet around the star and not some dark object that moved in font of it that is part of our solar system.
The stars observerd are between Cygnus and Libra so it is only a small part of the sky that will be observerd.
March 7th, 2009 at 10:58 am
woohoo! bring on the detection of terrestrial planets!
March 7th, 2009 at 11:38 am
Sadly, I have little confidence that we will ever make contact with other civilizations, even if they are there. The costs are just too great and I don't see a breakthrough that will let us travel at relativistic speeds.
March 7th, 2009 at 12:57 pm
John M. has a good point. If we actually could determine there was a civilization on one of the not-yet-found planets, we'd have to contact it, wait for the signal to get there, wait for them to process it, wait for it to get back, hope to God in Heaven that they were friendly and then we still have no way to get there unless they can show us something they figured out. In which case they might arrive at our doorstep. That could be very good…. or bad.
Even if we could contact another civilization, you can't simply 'go there'. The risk of contamination is too great. So you're stuck as intergalactic pen pals for a very long time – again, only if they're friendly.
March 7th, 2009 at 1:00 pm
There's no sense in not hoping! With stuff like nuclear propulsion or solar sails or whatever, we could even get spacecraft to stars such as Alpha Centauri well within a person's lifetime.
And simple EM contact, although probably unlikely, doesn't really have many "costs."
And regardless of either of those, Kepler is searching just for detection of terrestrial planets. Which rocks for science and imagination no matter what!
March 7th, 2009 at 1:31 pm
How about some info on why they chose this spot to look at?
Of course there will be a "star-trek" future of some sort, though it may take more centuries than Hollywood imagines. But maybe it is THEY who have to hope that WE are "friendly" !
Maybe these daunting distances will also teach us that the most important answers we seek can be found without leaving home.
The biggest challenge in interstellar exchange is the potential difference in stages of development between peoples, and therefore the importance of keeping appropriate relations. We can only assume that there are already more advanced peoples who must be aware of us, and their behavior would suggest that they are altruistic enough to leave us alone, and perhaps even protect us (while studying us). But I suspect that the biggest reason for our being ignored is simply that life is so common and similar, that we are in no way exceptional.
March 7th, 2009 at 2:12 pm
John M, hope is always there. About 100 years ago it was impossible to put a human on the Moon. Hell, 100 years ago it was impossible to let people fly!
You cannot predict what the future will look like, but it might not be in your lifetime.
But there is also some hope, we have this String Theory that could explain fundamentel parts of the fabrics of the universe and particle. Maybe the string theory is wrong, maybe not, but who knows what they discover by digging deeper into the strin theory and dark matter and dark energy. It could be a start of a whole new area of psychics, just like Einstein changed Newton to the theory of relativity.
There is always hope!
March 7th, 2009 at 3:13 pm
OK, I agree that hope is always there. But I also think too much hope can be a bad thing.
This is what happened with space travel. In the beginning, people assumed that it would develop quickly, that from the early flights it would be a little more than a piece of cake to extend them to the Moon, Mars and the rest of the planets. This excessive optimism, that didn't take into consideration the vastness of interplanetary space and the hard facts about orbital energetic economy, backfired. Strongly. It's the root of most of today's NASA bashing, which is largely undeserved.
The fact is: space travel is serious business, higly problematic, and the longer the travel, the larger the vehicle has to be, and the larger the vehicle, the harder it gets. To go interstellar will raise problems we can't even begin to imagine today. I still believe wi'll do it, eventually, provided we don't screw everything with one of the several global threats that are currently hanging over our heads, but it won't be anytime soon, and will be one the toughest things the species as a whole will ever do.
March 7th, 2009 at 3:37 pm
Actually, project Longshot was expected to get a probe to Alpha Centauri, and doing so with technology available 10 years ago, it was expected to reach Alpha Centauri in about 100 years.
March 7th, 2009 at 3:47 pm
Trippy, project Orion promised the same some 40 years ago. It didn't happen, and many think it couldn't happen.
I'm all in favour of these projects, they're one way to push the boundaries of what's possible and to get to new ideas, but I take their promises with a huge grain of salt. Looking back to history, it's more likely that they overlook some critical factor, than they are able to deliver what they promise.
March 7th, 2009 at 4:44 pm
Yes space business is still serious stuff but we now also have more and more nono-technology, creating new materials.
Even if we cannot do space travel, maybe we could set up a fast stellar communication network using some new technology and physics we do not know it exists yet.
You need somehow an ideal mix of passion and hope to push your bondaries and be realistic enough not to have to high of expectancies you get demotivated.
Dare to dream.
March 7th, 2009 at 5:41 pm
Geoff of Essex comments on the Star Trek issue (in response to Jason at March 7th 8pm).
One year is 8765 hours, or 525945 minutes, or 63138 astronomical units. To get anywhere from here in a reasonable time implies much higher cruise speeds than are currently available. Spacecraft launched between 1973 and 2006 are moving on average in the 4 to 6 AU per year range. To reach the nearest star system (Proxima Centauri at 4.2 light years) would take 15784 years at 4 AU/year and 10523 years at 6 AU/year. Transit velocities 10s, 100s or even 1000s of times faster than currently possible are needed to get anywhere else anytime soon.
How long does it take to reach one light year at various velocities: 40 AU/year takes 1578 years, 400 AU/year takes 158 years, 4000 AU/year takes 16 years. Multiply each by 4 to get to the Centauri system. And at 60 AU/year, 600 AU/year and 6000 AU/year it takes correspondingly less, about 66% of the above figures.
Interestingly these velocities can be translated to light speed by dividing the AU/year figure by 63138; so at 4000 AU/year implies 0.0634 or 6.34% sol (speed of light); and 6000 AU/year implies 9.51% sol.
When these velocities will be reached realistically depends on how quickly on average they can be doubled per period.
Assuming (optimistically) they could be doubled (from the present 4-6 AU/year) each decade then a 1000-fold increase, would require 8 doublings (around 80 years from now, say ~2090) giving ~6% sol (at 4000 AU/year) and ~9% sol (at 6000 AU/year).
If a (more optimistic) view is that velocities could be squared in each decade then around 3.5 doublings will get the average cruise speed to this level, implying ~2035 would see 1000 AU/year reached.
A (less rosy) view that these speeds will take longer to achieve, implies that the period is doubled to get these speeds, so 8 doublings take 160 years to reach 1000 AU/year, or ~2170 to make ~6% sol.
Plug your own figures into these assumptions to come up with your own ideas on when starflight could be realistically expected to start. Short of a “Contact” or “Stargate” device, left to our own efforts it will take some time to reach the capability to “boldly go where [none] have gone before!”.
March 7th, 2009 at 6:39 pm
The 'contact' part is not out of the question here – we'll probably discover some race and have the ability to contact them in the next 50 years. But intermingling with them? Bad idea. Cross-contamination alone makes this a certain disaster and then again, are they going to be friendly?
March 7th, 2009 at 6:40 pm
Jorge:
True, but Project Longshot is a development of Project Orion (development in that it contains considerable advancements), and Project Longshot is an un-manned probe, as opposed to Project Orion which was ended by the partial test ban treaty in 1963.
The main problems cited by the punlishers of the original idea were that advances in micro bomb fusion, AI (fiven the 4 year delay, the system needs to be autonomous), and the infrastructure required to get the components into LEO for assembly and launch.
396 metric tons at launch, with 264 tons of propellant.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19890007533_1989007533.pdf
March 7th, 2009 at 7:03 pm
Ugh, I meant Daedalus, not Orion, although arguably, Daedalus is still a development of Orion.
March 8th, 2009 at 2:24 am
woohoo! bring on the detection of terrestrial planets!
March 8th, 2009 at 7:04 am
"Trippy, project Orion promised the same some 40 years ago. It didn't happen, and many think it couldn't happen."
Orion's problems were more political than technical. Wehn people get bent out of shape over launching probes that contain only enough plutonium for an RTG, you know that a system requiring multiple nuclear detonatons isn't going anywhere. And the Nuclear Test Ban Treaty made no exceptions for nuclear detonatons in space for propulsive purposes.
We haven't been to the Moon since 1972, because Congress wasn't interested in supporting large manned space projects , after the initial Apollo successes. We han nuclear (that word again) thermal rocket technology mostly in hand, but ended the NERVA project because the Mars and advanced Lunar missions where they would've been most useful, noted, wern't going to happen.
Some things are currently out of our technological reach, but some things don't happen because of money/politics.
Simple as that.
March 8th, 2009 at 7:54 am
A couple of nitpicky things:
1) If the estimate of the stars in the milky way is somewhere around 400 billion, and if 1% of the stars has an earthlike planet around it, there could be … 4 billion earthlike planets in our galaxy alone, not 1 million. But if we look at sunlike stars only, and the estimate of 10% of the stars in our galaxy are sunlike, then the number of earthlike planets, at 1% would be: .01 x .10 x 400 x 10^9 = 400 million earthlike planets. I'm wondering where they got the 1 million number from …
2) Kepler won't be just looking at sunlike stars. In the field of view, there will be many small red dwarf stars, and any planets in the habitable zones of those stars won't take 1 year or 3 years to be verified. We could be getting results a lot earlier if we count those.
3) Jupiter sized planets in the habitable zone could potentially have habitable moons. If we find 0 earthlike planets in the habitable zone, but several or many jupiter sized ones (we've already found a few of those), then the potential for habitable worlds still exist, even without exact copies of earth.
4) The section of the sky they are looking at contains 4 to 6 million stars, or about .001 % of the stars in our galaxy. The number of stars in that sample that are edge on to us (so we can see the light dimming as a planet passes in front of us) is estimated to be about 100000. Can we get a statistically significant estimate from such a small sample, significant enough to conclude that if we don't find any earthlike planets, that there aren't any and we are then alone?
March 8th, 2009 at 9:24 am
Great that Kepler launched OK without a glitch. I think we'll find terrestrial planets are "as common as muck".
March 8th, 2009 at 12:44 pm
Even if Kepler doesn't find any Earths, that could just mean they chose the wrong spot in the sky.
I can't WAIT till we find another habitable zone planet and or life on Mars 'cuz I'm getting really tired of hearing this crap of Are we alone? Find SOMETHING already.
To think we are special in this Universe is egotistical, vain and plain ignorant….
March 8th, 2009 at 4:59 pm
McRude, remember just 15 years ago, there were still a lot of the most INTELLIGENT in the scientific community telling us there were no other planets outside our solar system.
March 8th, 2009 at 6:57 pm
3) Jupiter sized planets in the habitable zone could potentially have habitable moons. If we find 0 earthlike planets in the habitable zone, but several or many jupiter sized ones (we've already found a few of those), then the potential for habitable worlds still exist, even without exact copies of earth.
Absolutely. I'm always befuddled on the people who leap on things which at the moment are completely untestable like panspermia – but this obvious possibility of an earthlike world orbiting a gas giant gets practically no coverage. Can you imagine what the sentient beings evolving up under a gas giant like Jupiter's take would be on the planet and it's forever changing patterns? THAT'S a fun mental playground.
March 8th, 2009 at 8:58 pm
I did a calculation some time back to estimate how many Earth-like planets there might be. I got about 10,000. This was based on a Bayesian analysis on Lyapunov exponents for putative 1AU planets that are modeled to exist in known extrasolar G-class systems. A close Jovian would tend to rattle the orbit and cause it to chaotically shift too much.
Of course this does not say much about moons around ~ 1AU Jovians.
The galaxy has about 300 B stars, and 3% of them are stars comparable to the sun, or in the near G category of F or K class. The statistics seemed to indicate that a pretty small fraction of stellar systems are comparable to outs. Of course this is based on incomplete evidence, as most techniques favor finding close in or torch Jovian planets.
Kepler will give a clearer picture of things and better estimates on the number of possible bio-active planets out there.
Lawrence B. Crowell
March 9th, 2009 at 10:15 am
can't wait for first pictures to be shared. Unfurtuanally, looking at a planet 7 billion light years will let us see how the planet was 7 billion years ago. Finding another earth will make me really happy though, I stay really positive; after all this is a 95 megapixel camera!
March 9th, 2009 at 10:25 am
Have read that when our sun becomes a red giant then Titan will have the heat to evolve into habitability so I assume that a star's habitable zone varies with the age, type, and size of the star and thus the orbit of objects within that zone may be quite different than our earth's orbit. Am I wrong, or shouldn't we be focusing our planetary and moon search among habitable zones in all probable life supporting stars, not just those similar to our sun? MOK
March 9th, 2009 at 1:18 pm
(McRude Says: March 8th, 2009 at 12:44 pm “Even if Kepler doesn't find any Earths, that could just mean they chose the wrong spot in the sky”).
As the Chinese say, “the longest journey begins with the first step”.
Kepler is a first of a kind type mission – its search area is reported to be a 10 degree by 10 degree square of the sky. That represents 1 part in 648 as in 180 x 360 = 64800 versus 10 x 10 = 100; or about 0.15% of the sky’s surface area. If nothing is found in that patch there are another 647 similar sized patches of the sky to look in. Not all are equally likely to be suitable for searching in. Doubtless, some kind of analysis, such as led to the picking of this “patch of sky in the Cygnus-Lyra region of the Milky Way” will turn up the better “patches” for the next or the next or the … mission to look over and get “lucky”.
However, if the nearest “Earth-like” planet is 50 or 500 or 5000 light years away, no one is going there anytime soon, so what’s the hurry.
As another poster (miguel Says: March 9th, 2009 at 10:15 am) commented these objects are as they were 50, 500 or 5000 years ago, and if one-way trips take many multiples of the distance in years to get there – who is to say what condition they would be in when anything we can send gets there! Any results, messages etc would then take a similar time to the distance in years to get back.
March 9th, 2009 at 2:16 pm
Another important fact to remember is that if Kepler only detects planetary transits, it means it can look directly at a star with planets but not detect them if they do not pass between the star and the probe (i.e., if Kepler is looking at the star's north or south pole). If it is taking radial velocity measurements as well, that would be much more likely to detect new planets.
And 7 billion light years is a gross exaggeration, the Milky Way is only 100,000 light years across. I don't know about the Cygnus-Lyra region, but there are plenty of stars with planets that are under 100 light years away, such as the famous Gliese 581 (Ymir).
March 9th, 2009 at 4:46 pm
Just a couple of comments to clarify things:
- Kepler only monitors about 100,000 "sun-like" stars (i.e. late-type dwarf stars). These stars have been preselected as targets, since Kepler is not able to send back the entire image from its 95Mpix camera (not enough bandwidth!).
- Kelper targets will be quite bright (V<15), and so it is unlikely they will be more than 3000 light years away. However VERY few would be closer than 100 light years away.
- The chance of an earth-like planet transiting a star of known radius can be worked out geometrically. it is quite low… only a few percent, because the probability drops as the planet is further from its host star.
- since a few percent of earth-like planets transit, 100,000 will be statistically sufficient as it provides a few 1000 systems with the potential for transits (if they host planets!).
Good luck Kepler!
March 9th, 2009 at 5:22 pm
thank you, McRude; I feel the same way. I wish these egostical so-called-scientists and wannabes, like Glover would realize that we are not special. We dont have to send 1/2 BILLION$ ROBOTS into space to know that we are not alone. The cosmos are just too enormous. We'd have to be vain to the core to assume that just because our little machines does not know where to search and that our little robots cannot detect life as we know it…. that we shall assume there is no other life…PLEASE! GET REAL! if we could see some of the life that God has placed out there, it would frighten our little ancient minds out of there skulls. Maybe its best to settle for life here on Earth, feed the hungry, save the whales, nourish the forests, clean the oceans and the atmosphere… there's a good start at finding more life for you.
March 10th, 2009 at 4:58 am
two points:
1. Larger objects are generally far less common than smaller ones, on that basis alone I would expect earth sized objects to be more common than the already found Jupiter + sized planets, (and less common than mercury sized bodies). So I'm expecting Kepler to find many 'Earths' out there!
2. However, If Kepler was 20 light years out there, and looking back into our own solar system – would it consider Venus (as hostile a planet as you can imagine!) a potentially habitable world? Would it be capable of resolving close orbital/mass partners Earth and Venus or would it miss one or both of them?
March 10th, 2009 at 6:15 am
UKDave touches on an aspect of the mission glossed over in several articles & mistakenly repeated in most of these replies. Kepler will be looking for Earth-SIZED planets and not necessarily Earth-LIKE planets. As UKDave alluded to, Venus & Earth share similar diameters & masses, but Venus is anything but Earth-like. Of course, Keplers' discovery of Earth-sized planets will allow intense follow-up by ground & space-based telescopes to tease out any info regarding the atmospheric composition & temperature of these planets. But Earth-sized planets are not necessarily Earth-like.
March 10th, 2009 at 7:05 am
im excited that finally something took off the ground which will stay in the orbits of moon and earth. And hopes are high. Kepler is the biggest hope for Astronomers and for us who r seeking for the answers; that r v really alone?
Let's c wat does Kepler do in it's journey?
March 10th, 2009 at 7:15 am
I wud also add; if Kepler is watching the Milkyway patch targeting Cyngnus-Lyra constellations, then shud we assume that life do exist in Vega, As in Jodie Foster's movie "CONTACT". She caught the signals and Hadden helps her to reach him.
Are all scientists are convinced that there's a minor or maxim chance of habitants in Vega in Lyrae. Is this the reason they chose for Cygnus-Lyrae?
March 11th, 2009 at 7:47 am
Muhammad Tahir Iqbal Says: March 10th, 2009 at 7:15 am
“Are all scientists convinced that there's a minor or maximal chance of habitants in Vega in Lyrae. Is this the reason they chose for Cygnus-Lyrae?”
The reasons for selecting one patch of sky rather than another would have little to do with expectations of life – or otherwise on the part of the selectees. After all conducting science and/or research based on “preconceived ideas” about what is <> is neither science nor research. Why conduct research, if you “know” the answer before hand, that is not research!
The reason for selecting this region appears to be on the so-called Goldilocks principle that the search area should not be too crowded (looking towards the Galactic Centre), nor too sparse (looking towards the Galactic Poles). Taking the “happy” medium of looking towards either 45 degrees above/below the Galactic Equator puts the search area field of view where the stars are not on top of each other (from the line of sight perspective) and also too separated that the field-of-view is being wasted.
Also looking for a Galactic Habitable Zone “Goldilocks” region, it makes sense to look at the local Galactic neighbourhood first, rather than half-way across the galaxy. The sun is located about 27,000 light years from the centre so, if you restrict the initial searches to say ± 5,000 light years from home and do your statistics on that region, this can then be applied (with some confidence) to further areas of search in later missions. Too close to the centre and the cosmic ray radiation may be too high, plus increased risk of supernova blasts and reduced metallicity in stars; too far from the centre out towards the edge and the inverse is thought to be true. Why not stick (at least initially) to the local regions in the mid-ranges of the galaxy away from the bulge and in some of the nearer spiral arms, etc.
March 11th, 2009 at 7:51 am
Regarding my previous comment, the "" word was meant to be "known" – hope this clariies matters.