So Much for Earth Being Special: There Could Be 20 Billion Just Like It

A new estimate of Earth-like worlds in the Milky Way yields good news in the hunt for extraterrestrial life

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Babek Tafreshi / SSPL / Getty Images

The planet-hunting Kepler Space Telescope is deservedly celebrated for some of its more dramatic discoveries: a world with two suns, for example, a planet half-shrouded with clouds, a planet whose size and composition are a near match to Earth’s. But the ship is in some ways a pretty prosaic machine — a robot census taker, no more, no less, hanging in space and counting heads, to determine how many stars other than our own are home to planets. Like a census taker too, however, it has to make some pretty elaborate inferences.

It’s not possible to detect and count every single planet in the Milky Way, any more than it’s possible to shake the hand and take the name of every single person living in the U.S. In both cases, a sort of statistical sampling is often involved. When you know enough about most of the people living in any one town, county or state, you can make accurate inferences about the rest. The same goes in space, where Kepler is trying to determine the frequency of certain types of exoplanets. What percentage of stars host Jupiter-size worlds? How many have Neptunes? And most crucially for the search for extraterrestrial life, how many Earth-size planets orbit in their stars’ habitable zones, the regions in which temperatures are hospitable for living creatures?

Kepler has been chipping away at this question since the probe was launched in 2009, but a new report in Proceedings of the National Academy of Sciences has now moved scientists a giant step closer to the ultimate answer. According to the new analysis, a whopping 22% of sunlike stars have planets more or less the size of Earth in their habitable zones. That adds up to about 20 billion Earths in our galaxy alone, says lead author Erik Petigura, of the University of California, Berkeley. That in turn means that an Earth-like world is likely to be just 12 light-years away, and that its parent star is visible to the naked eye. “It’s really amazing when you think about it,” Petigura says.

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It’s not just amazing, though: it’s crucial to the search for life. If the fraction of stars with life-friendly Earths was much smaller (a few years ago, says Petigura, some estimates put it as low as .0001%), the nearest one might easily be too distant to study for signs of biological activity, even with the most advanced telescopes currently on the drawing boards. If there’s one practically next door, as the new study suggests, that kind of remote analysis should be comparatively easy.

The new estimate of plausibly habitable planets is based on an intensive search through Kepler’s massive database — but not a comprehensive one. The satellite has been monitoring more than 150,000 stars, looking for the almost imperceptible dimming caused when a planet moves in front of its parent star. Many of these targets are anything but sunlike: they’re the smaller, redder, dimmer stars known as M-dwarfs. Astronomers already know that some M-dwarfs harbor Earth-size planets. A study earlier this year, in fact, suggests that the nearest of these is about 13 light-years away.

But it’s by no means certain that Earths around M-dwarfs could be habitable. Among other things, the planets always keep the same face toward their stars, the way the moon does to Earth, meaning one side could be a lot hotter than the other. So Petigura and his colleagues limited their search not to Kepler’s full target list, but to a subset of about 40,000 stars that range from .7 to 1.2 times the size of the sun. They’re not all perfect copies of our home star, but, says co-author Geoff Marcy, also at Berkeley, “if you flew past them in a spaceship you wouldn’t be able to tell the difference.”

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In the end, the researchers turned up ten approximately Earth-size planets circling their stars at a distance at which water could exist in liquid form, which biologists think is essential for life—at least the kind of life we can imagine.  To make the leap from ten to 20 billion, the astronomers had to extrapolate. For example, they had to take into account that many Earth-size planets got missed because their orbits didn’t happen take them directly in front of their stars.

They also realized that some of the planets that did pass in front of their stars would be missed as well, because their signals were too weak to emerge from the visual static that bedevils such high-precision observations. So Petigura created fake planets with weak signals, and by noting how many the software missed, he could tell how many real planets had probably escaped detection as well. And, of course, the researchers had to factor up from the 150,000 stars in Kepler’s field of view to the 300 billion or so that make up the Milky Way.

Taken together, these adjustments yielded the new 20 billion Earth-like planet estimate. “I do have to add a note of caution,” says Petigura. “These planets are only Earth-like in terms of their size and the amount of energy they receive from their stars. We don’t know if they have rocky compositions, oceans of water, plate tectonics or life.”

(MORE: Most Distant Galaxy Found — and Yes, It’s Far, Far Away)

To answer the ultimate question of whether life exists beyond Earth, astronomers will have to go beyond statistics to identify an actual mirror Earth in our cosmic neighborhood, then scrutinize its atmosphere for gases like oxygen and methane, which could be telltale signs of biological activity. Those observations won’t be possible for years.

But at least they know they’re not looking for something so vanishingly rare, we’d never be likely to stumble on it. The Milky Way is evidently teeming with balmy, Earth-size planets. And unless nature is far more perverse than anyone expects, there’s got to be life on at least some of them.

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8 comments
notLostInSpace
notLostInSpace

Maybe there is another "exceptional" country on one of these planets like ours?

Adam_Smith
Adam_Smith

"In the end, the researchers turned up ten approximately Earth-size planets circling their stars at a distance at which water could exist in liquid form, which biologists think is essential for life—at least the kind of life we can imagine."

Another story today at Phys.org explains how a favorable temperature zone is not enough to guarantee a useful amount of water. If there is too much carbon it takes up the oxygen preventing the formation of water -- producing a world that might actually be abundant with diamonds but seriously lacking in water. Unfortunately, no estimate was given for how much this lowers the odds for a world being wet enough to be suitable for life.

http://phys.org/news/2013-11-carbon-worlds-waterless-nasa.html

BabuG.Ranganathan
BabuG.Ranganathan

CATCH-22 FOR EVOLUTIONARY ORIGIN OF LIFE

What many don't realize is that although oxygen is necessary for life's processes, the presence of oxygen would prevent life from coming into being. This is because oxygen is destructive unless there are mechanisms already in place to control, direct, and regulate oxygen such as what we find in already existing forms of life. What about water? Remember, water is part oxygen.

Evolutionists must assume that the early earth had no oxygen. But, then that would mean there was no ozone layer in the atmosphere to protect from harmful radiation that would destroy life or even any budding form of life. Ozone is made-up of oxygen. It's a Catch-22 situation for evolutions. In fact, there are numerous Catch-22 situations for evolutionists when it comes to the origin of life issue.

The latest scientific evidence from geology shows that there, indeed, was oxygen in the earth's earliest atmosphere.

In addition to all this, millions of molecules making up a cell would have to come together in the right sequence (just like letters in a sentence). Every scientist knows that this can't happen by chance. The probability of just a single protein molecule arising by chance is 10 to the 65th power.

Mathematicians have said any event in the universe with odds of 10 to 50th power or greater is impossible!

Even the simplest cell has millions of such molecules. And, the cell would have to come into existence and be living all at once. It could not have gradually evolved. A partially evolved cell would quickly disintegrate under the effects of random forces of the environment, especially without the protection of a complete and fully functioning cell membrane. A partially evolved cell cannot wait millions of years for chance to make it complete and living! In fact, it couldn't have even reached the partially evolved state.

Of course, once there is a complete and living cell then the code and mechanisms exist to direct the formation of more cells. The problem for evolutionists is how did the cell originate when there were no directing code and mechanisms in nature. Natural laws may explain how a cell or airplane works but mere undirected natural laws could not have brought about the existence of either.

Natural selection you say? Natural selection doesn't create or produce anything. It can only "select" from what is produced that has survival value. Natural selection can only "select" from variations that are possible. If a variation occurs that helps a species survive, that survival is called " natural selection." It's a passive process. There's no conscious selection by nature, and natural selection only operates in nature once there is life and reproduction and not before, so it would not be of assistance to the origin of life.

Science can't prove we're here by chance or design. Neither was observed. Both are positions of faith. The issue is which faith is best supported by science. Let the scientific arguments of both sides be presented.

Read my popular Internet articles: SCIENCE AND THE ORIGIN OF LIFE, ANY LIFE ON MARS CAME FROM EARTH

Visit my Internet site: THE SCIENCE SUPPORTING CREATION

Babu G. Ranganathan*

(B.A. Bible/Biology)

Author of the popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

*I have given successful lectures (with question and answer period afterwards) defending creation before evolutionist science faculty and students at various colleges and universities. I've been privileged to be recognized in the 24th edition of Marquis "Who's Who in The East" for my writings on religion and science.

ojoprieto
ojoprieto

I hope they are smarter than we are.

DeweySayenoff
DeweySayenoff

Given the unique qualities of the planet earth, it's very questionable whether another "mirror Earth" exists with intelligent life.  Mars and Venus are rocky planets in our habitable zone and neither are candidates for life today.  If any existed on Mars, it's almost certainly long extinct. If there is life on Mars, and our instruments couldn't detect what little life there may be today from a mere 32 million miles away, let alone 32 LIGHT YEARS, life has to be pretty abundant to be detected at all.

But even with magnetism, plate tectonics, a temperature/gravity balance that lets us keep an atmosphere AND liquid water plus the stabilizing influence of the Moon on our rotation (precession would make the earth tumble around adding to environmental instability without the Moon keeping us more or less "upright" all the time), intelligent life didn't rise up on earth until the last 0.0044% of the time the earth has existed.  And given our proclivities, we aren't likely to last in the future as long as we've lasted as a species so far.

Is there "life" on other earth-like worlds?  Sure.  Almost without any doubt.  Is there any INTELLIGENT life in our galaxy?  Presuming that we are intelligent to begin with, the answer to THAT question still remains highly doubtful given the time scales involved.  There likely WAS intelligent life before us somewhere in our galaxy.  Today, it's hard to say if it went extinct or still exists, but I'm betting on extinction and here's why: Intelligent life protects its weak.

We as a species rose not because we protected our weak, but because we didn't.  We let the "unfit" die.  We didn't have the technology or knowledge to save them, BUT WE WANTED TO SAVE THEM.  Evolutionarily speaking, letting the "unfit" breed weakens a species.  It makes the species less adaptable, more prone to deadly adaptations and mutations and other factors that threaten the existence of an intelligent species.  Yes, tehcnology can overcome much of it, but nature has a way of adapting because we become the environment other species must adapt to.  And by doing so, they become stronger, and our ability to cope with them weakens.  Look at MRSA and "flesh eating" bacteria outbreaks as examples.  They adapted to new factors in their environment and came back stronger and better able to survive.

So this presents an interesting, and potentially frightening, set of possibilities:

First, intelligent life de-evolves and re-evolves over and over (provided it doesn't go extinct in the process) because at some point, the technology breaks down and can't sustain the majority of a species and there's a mass die-off.  At that point, without technology, the unfit begin to die again and the species emerges stronger, re-invents a new technology and the cycle starts over again.

Second: Intelligence is based on survival and "short-sighted sentimentality" is eventually discarded, mandating sterilization for those who aren't seen as "fit enough to breed."  We did this in the Nazi era (eugenics was big in the early 20th century), but we aren't bright enough to do it without some political agenda calling the shots.  Maybe another species will do the same.  Some of those sci-fi movies where Earth is invaded by eugenics-controlling Nazis may not be off the mark, but I'd expect they'd just exterminate us for our resources - what little of them we have left - if they thought it was worth the bother.  With billions of "earth-like" planets to exploit, why mess with one that's already occupied by a belligerent, war-like species?

Third: Intelligence is fatal to a species.  No intelligent species lasts long enough to survive its own technological childhood.  They kill themselves off before they ever begin to de-evolve.

Fourth: An emotionless, pragmatic intelligent species has no sentimentality to begin with and cooperates only because it is beneficial for the whole at the expense of the individual.  By the way, this describes ants and other colony-type life forms.

Fifth: Intelligence of mind without technology.  Aquatic creatures (as an example) will never develop technology because they can't use fire.  But there's nothing that says they can't be intelligent.  The trouble with this is that they will never develop the means to avoid their own extinction by natural phenomenon like asteroids or plagues.  If technology doesn't get them, it's pretty certain nature eventually will.

There are certainly others.  That's just off the top of my head.  And none of this takes into account that it's really unlikely they will communicate with us assuming we recognize them as an intelligent species to begin with.  Humanity doesn't have a very good track record at making friends - among our own kind or with other species.  The factors supporting life in general are high.  The factors supporting long-term intelligent life are very, very low - at least for life like US.

Life will likely be all over the galaxy.  But I don't think we'll ever be having cordial, two-sided conversations with any of it.

Ben-ann
Ben-ann

"I have as yet to determine which is more frightening, the possibility that there may be other life in the universe or the possibility that we are entirely alone!!

Adam_Smith
Adam_Smith

"Even the simplest cell has millions of such molecules. And, the cell would have to come into existence and be living all at once."

I believe that evolutionists theorize that relatively simple amino acids and peptides are created first by random combination. More complex molecules are then built from random combinations of these -- and these kinds of molecules are very prone to combining in ever more complex ways.

Adam_Smith
Adam_Smith

@BabuG.Ranganathan Hmm. Too much oxygen, too little oxygen -- it's a problem either way. It seems there is a delicate balance of carbon, oxygen, silicon and hydrogen that produces a wet rocky world with enough left over oxygen to be favorable for life. Furhermore, it may be that metals as heavy as iron or better may be needed to produce a technological civilization or even more complex forms of life.