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Earth-like planets may be more rare than thought
Nature Magazine ^ | 30 July 2004 | Philip Ball

Posted on 07/30/2004 11:12:50 AM PDT by PatrickHenry

We could be alone in the Universe after all. The discovery during the past decade of over a hundred planets around other stars has encouraged many scientists to think that habitable planets like ours might be common. But a recent study tells them to think again.

Martin Beer of the University of Leicester, UK, and co-workers argue that our Solar System may be highly unusual, compared with the planetary systems of other stars. In a preprint published on Arxiv1 [footnote's link in original article], they point out that the alien planets we have seen so far could have been formed by a completely different process from the one that formed ours. If that is so, says Beer, "there won't necessarily be lots of other Earths up there".

Most of the planets around other stars, known as extrasolar planets, are detected from the wobble that they induce in their own sun's motion. This wobble is caused by the gravitational tug of the planet on the star. Because stars are much bigger than planets, the effect is tiny, and it is only in the past decade that telescopes have been sensitive enough to detect it.

Even then, the wobble is detectable only for giant planets, which are those about as big as Jupiter, the bloated ball of gas in our Solar System. It is not possible at present to detect planets as small as the Earth.

Jupiter is not habitable: it is too cold, and is mostly composed of dense gas. And it is unlikely that extrasolar giant planets would support life either. But astronomers generally assume that if they detect such a planet in a distant solar system, it is likely to be accompanied by other, smaller planets. And maybe some of the smaller planets in these systems are just like Earth.

This is what Beer and colleagues now dispute. They say that the properties of almost all the known extrasolar planets are quite different from those of Jupiter.

Hot Jupiters

There are 110 of these extrasolar planets, at the latest count, and they are all between about a tenth and ten times as massive as Jupiter. Most of them are, however, much closer to their sun than Jupiter is to ours: they are known as 'hot Jupiters'. They also tend to have more elongated orbits than those of Jupiter and the Earth, both of which orbit the Sun on almost circular paths.

Ever since Copernicus displaced the Earth from the centre of the Universe, astronomers have tended to assume that there is nothing special about our place in the cosmos. But apparently our planetary system might not be so normal after all. Is it just chance that makes Jupiter different from other extrasolar planets? Beer and his colleagues suspect not.

They suggest that other planets were not formed by the same kind of process that produced our Solar System, so they might not have smaller, habitable companions.

Different recipes

The planets in our Solar System were put together from small pieces. The cloud of gas and dust that surrounded our newly formed Sun agglomerated into little pebbles, which then collided and stuck together to form rocky boulders and eventually mini-planets, called planetesimals. The coalescence of planetesimals created rocky planets such as Earth and Mars, and the solid cores of giant planets such as Jupiter, which then attracted thick atmospheres of gas.

But that is not the only way to make a solar system. Giant planets can condense directly out of the gaseous material around stars, collapsing under their own gravity. This process, which generates giant planets with a wide range of orbital radii and eccentricities, does not seem capable of producing the rocky planets seen in our own Solar System, which is why it has generally been ignored.

Yet it might account very nicely for the known extrasolar planets. "It wouldn't surprise me if there are two different ways that planetary systems are formed," Beer says. But how can we know if that is the case? "Probably the best way is just to gather more observations," says Beer. Only then can we know how unusual we really are.


TOPICS: Culture/Society; Miscellaneous; Philosophy
KEYWORDS: astronomy; cosmology; earth; planets; science; xplanets
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Opinions certainly seem to vary on this topic.
1 posted on 07/30/2004 11:12:51 AM PDT by PatrickHenry
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To: VadeRetro; jennyp; Junior; longshadow; RadioAstronomer; Physicist; LogicWings; Doctor Stochastic; ..
Science list Ping! This is an elite subset of the Evolution list.
See the list's description in my freeper homepage. Then FReepmail me to be added or dropped.
2 posted on 07/30/2004 11:14:02 AM PDT by PatrickHenry (Since 28 Oct 1999, #26,303, over 192 threads posted, and somehow never suspended.)
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To: PatrickHenry

"rarer"?


3 posted on 07/30/2004 11:15:52 AM PDT by Viet Vet in Augusta GA
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To: PatrickHenry

All I know is that if space is infinite then there has to be at least one.


4 posted on 07/30/2004 11:17:07 AM PDT by Bikers4Bush (Flood waters rising, heading for more conservative ground. Vote for true conservatives!)
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To: PatrickHenry

There was a book written on this very topic a few years back, but the name escapes me at the moment.


5 posted on 07/30/2004 11:17:12 AM PDT by ECM
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To: PatrickHenry

"Even then, the wobble is detectable only for giant planets, which are those about as big as Jupiter.."

So what does this tell them about the existance of earth-sized planets? Zippo.

In all the millions of galaxies, each with millions of stars, its hard to believe that whatever conditions were conducive to the formation of life here did not also occur elsewhere.


6 posted on 07/30/2004 11:17:37 AM PDT by ZULU
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Comment #7 Removed by Moderator

To: PatrickHenry

Creationist arguments aside, its hard to say really if another Earth could develop somewhere.


8 posted on 07/30/2004 11:18:29 AM PDT by RockinRight (Liberalism IS the status quo)
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To: PatrickHenry

I wonder if Martin beer is any relation to the great german astronomer Wilhelm Beer.


9 posted on 07/30/2004 11:18:49 AM PDT by RightWingAtheist (<A HREF=http://www.michaelmoore.com>stupid blob</A>)
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To: PatrickHenry
110 out of BILLIONs of stars in one galaxy alone and they are already throwing in the towel? Sheesh... we just got started!

Do these knotheads never stop to think that there may be as many different processes for planet formation as there are dust clouds coalescing into stellar nebula? That each may be radically different from the next depending on the ratio and composition of elements contained therein?

That just because one person uses Nestle and I use Hersey's that the end result couldn't still be one darn tasty chocolate chip cookie?

Don't they teach logic any more?

10 posted on 07/30/2004 11:20:13 AM PDT by Dead Corpse (For an Evil Super Genius, you aren't too bright are you?)
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To: ZULU
In all the millions of galaxies, each with millions of stars, its hard to believe that whatever conditions were conducive to the formation of life here did not also occur elsewhere.

The condition for the formation of life is everywhere in the universe. Indeed it transcends the universe. It is God's creative power. Someday soon you will come face to face with that power.

11 posted on 07/30/2004 11:22:49 AM PDT by P-Marlowe
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To: PatrickHenry

Big News, the longer we study the Universe the more it invariably points to a Creator who designed this little "happenstance" called Earth.


12 posted on 07/30/2004 11:23:56 AM PDT by RUCKUS INC. ("Wow, what a crapweasel." - Frank_Discussion)
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Comment #13 Removed by Moderator

Comment #14 Removed by Moderator

Comment #15 Removed by Moderator

To: ECM
Rare Earth: Why Complex Life Is Uncommon in the Universe.
16 posted on 07/30/2004 11:29:26 AM PDT by Cincinatus (Omnia relinquit servare Republicam)
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To: TonyRo76

Just read your bio, it's nice to see a TULIP-er on FR.


17 posted on 07/30/2004 11:29:48 AM PDT by RUCKUS INC. ("Wow, what a crapweasel." - Frank_Discussion)
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To: TonyRo76

Would you mind quoting me the scripture that proves there are no other earthlike planets in the universe? I don't remember seeing that.


18 posted on 07/30/2004 11:36:25 AM PDT by thecabal ("For all that you hold dear on this good Earth, I bid you stand, Men of the West!" --Aragorn)
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To: ECM

Alchemy of the Heavens?
http://www.amazon.com/exec/obidos/tg/detail/-/0385472137/qid=1091212578/sr=8-1/ref=sr_8_xs_ap_i1_xgl14/104-0276543-3117500?v=glance&s=books&n=507846


19 posted on 07/30/2004 11:37:06 AM PDT by Little Ray (John Ffing sKerry: Just a gigolo!)
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To: Cincinatus

That would be the one--thanks!


20 posted on 07/30/2004 11:38:43 AM PDT by ECM
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To: Dead Corpse

The Milky Way galaxy has approx. 100,000,000,000 stars and it's 1 of approx. 1,000,000,000 or so galaxies. So this nitwit is ready to conclude there are no more "earths" after a very crude form of investigation of 110 planets around 25 or so stars that at this point can ONLY, ONLY detect Jupiter-sized planets.

Utter rubbish from a pseudo-scientist who had to work hard to find something to write about.


21 posted on 07/30/2004 11:39:44 AM PDT by Neville72
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To: PatrickHenry

There is only one data point. And that is us. All else is speculation. However, using probability, we can make some predictions. Thusly was born the "Drake Equation".


22 posted on 07/30/2004 11:42:52 AM PDT by RadioAstronomer
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To: ECM

the book was
"the rare earth"
written by brownlee and another u of wash prof
an amazing book.
They go thru all the arguments why complex life is so rare. This is my solution to fermi's paradox.


23 posted on 07/30/2004 11:45:15 AM PDT by genghis
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Comment #24 Removed by Moderator

To: PatrickHenry
There are 110 of these extrasolar planets, at the latest count, and they are all between about a tenth and ten times as massive as Jupiter. Most of them are, however, much closer to their sun than Jupiter is to ours

Why is this surprising? If we're using gravitational anomolies to detect planets, of course it's going to be easier to find large planets that are close to their sun, because the effects of gravity are much greater.

25 posted on 07/30/2004 11:53:06 AM PDT by ThinkDifferent
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To: PatrickHenry; AAABEST; Mycroft Holmes

Drake equation ping. I always go back and forth on this ....


26 posted on 07/30/2004 11:56:30 AM PDT by fooman (Get real with Kim Jung Mentally Ill about proliferation)
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Comment #27 Removed by Moderator

To: PatrickHenry

When there are billions of stars in each galaxy, and billions of galaxies, it's kinda hard to believe we're unique.


28 posted on 07/30/2004 12:00:27 PM PDT by jimt
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To: Neville72
The Milky Way galaxy has approx. 100,000,000,000 stars and it's 1 of approx. 1,000,000,000 or so galaxies. So this nitwit is ready to conclude there are no more "earths" after a very crude form of investigation of 110 planets around 25 or so stars that at this point can ONLY, ONLY detect Jupiter-sized planets.

Utter rubbish from a pseudo-scientist who had to work hard to find something to write about.

Well said.

Jupiter is not habitable: it is too cold, and is mostly composed of dense gas. And it is unlikely that extrasolar giant planets would support life either.

This type of thinking always amazes me. Yes, life that evolved on Earth has adapted to the conditions found on Earth, no surprise here. Would it be so surprising that life elsewhere in the universe would adapt to the conditions there?

29 posted on 07/30/2004 12:02:20 PM PDT by RJL
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To: PatrickHenry

Are We Alone (reason to ponder what makes the earth unique)


http://www.freerepublic.com/focus/f-news/1181928/posts


30 posted on 07/30/2004 12:02:26 PM PDT by Lucy Lake
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To: PatrickHenry
They suggest that other planets were not formed by the same kind of process that produced our Solar System, so they might not have smaller, habitable companions.

We've been over all this time and again on FR. Current detection methods select a highly specific (and probably highly unusual) sample which tells us little about Earth-like (or even Jupiter-like) worlds.

The idea that these close binary brown dwarf systems formed differently from our solar system in no way supports the title of this article, even if the idea is perfectly correct.

31 posted on 07/30/2004 12:02:41 PM PDT by Physicist
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To: TonyRo76

I think arminianism is arrogant and man centered and borders on man's will being a false idol...


32 posted on 07/30/2004 12:04:09 PM PDT by RUCKUS INC. ("Wow, what a crapweasel." - Frank_Discussion)
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To: TonyRo76

I think arminianism is arrogant and man centered and borders on man's will being a false idol...

I am a Conservatie Baptist who says "Thank God for Martin Luther"


33 posted on 07/30/2004 12:04:42 PM PDT by RUCKUS INC. ("Wow, what a crapweasel." - Frank_Discussion)
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Comment #34 Removed by Moderator

To: RadioAstronomer

What is your opinion of the arguments made in "Rare Earth". The Drake equation only gives the upside, but doesn't seem to take into account the conditions that would preclude higher forms of life. For instance, the radiation conditions in the core of galaxies and in the arms of spiral galaxies are too high to allow the survival of higher life forms. That leaves the area between the arms for habitable zones in spiral galaxies, and stars only stay in between the spiral arms for extended periods of time if they are 1/2 the radius of the galaxy from the center of the galaxy. These factors alone remove several orders of magnitude from the number of possible stars that could sustain higher forms of life.


35 posted on 07/30/2004 12:07:04 PM PDT by Pres Raygun
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To: PatrickHenry
I know as much about this as any non-specialist. Rare Earth makes as good an argument as the SETI proponents. One significant difference: the negative case is falsifiable (just find some ETs or an Earthlike extra-solar planet). The positive case can be continued literally forever: "They are there, we just haven't found them yet." It is worth some effort to find out, but anyone who claims to have the answer now is frankly full of crap.
36 posted on 07/30/2004 12:07:16 PM PDT by atomic conspiracy (A few words for the media: Julius Streicher, follow his path, share his fate.)
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To: thecabal

This seems too easy but "In the beginning God created the heavens (plural) and the earth (singular)"


37 posted on 07/30/2004 12:08:05 PM PDT by RUCKUS INC. ("Wow, what a crapweasel." - Frank_Discussion)
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To: RightWingAtheist
I wonder if Martin Beer is any relation to the great german astronomer Wilhelm Beer.

IIRC, they have a common ancestor Tümuch Beer...

38 posted on 07/30/2004 12:10:17 PM PDT by null and void (Freedom is written with blood on the streets, not with ink in congress.)
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To: PatrickHenry
They also tend to have more elongated orbits than those of Jupiter and the Earth, both of which orbit the Sun on almost circular paths.

I thought our planets' orbits were "wildly elliptical."

39 posted on 07/30/2004 12:10:38 PM PDT by Junior (FABRICATI DIEM, PVNC)
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To: ThinkDifferent
Why is this surprising? If we're using gravitational anomolies to detect planets, of course it's going to be easier to find large planets that are close to their sun, because the effects of gravity are much greater.

Ding Ding Ding! We have a winner!

It's called a "selection effect" - the data sample looks biased towards hot Jupiters, but that's only because current detection technologies find those preferentially. Give it about 10 years and we will have much better data with the new surveys coming on line. Anyway, personally I find it amazing that we now know of 10 times as many planets OUTSIDE our solar system as IN it!

The Extrasolar Planets Encyclopaedia

Exo Planets

40 posted on 07/30/2004 12:10:50 PM PDT by alnitak ("That kid's about as sharp as a pound of wet liver" - Foghorn Leghorn)
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To: PatrickHenry

Planets ten times as massive as Jupiter, those are some big-ass planets.


41 posted on 07/30/2004 12:11:20 PM PDT by jpl ("Go balloons, go ballons! Confetti, confetti, where's the confetti?" - Don Mischer)
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Comment #42 Removed by Moderator

To: PatrickHenry

HMMPH! Bodes well for the rest of the galaxy, then...


43 posted on 07/30/2004 12:12:15 PM PDT by Dawgmeister
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To: Dawgmeister

(sometimes it seems like ONE is too many.)


44 posted on 07/30/2004 12:13:18 PM PDT by Dawgmeister
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To: RadioAstronomer
There is only one data point. And that is us. All else is speculation. However, using probability, we can make some predictions. Thusly was born the "Drake Equation".

What about all the other lifeless planets and moons we can observe in our own neighborhood?

45 posted on 07/30/2004 12:13:25 PM PDT by Moonman62 (The Fermi Paradox Rules)
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To: RadioAstronomer; Dead Corpse; ZULU
I think that a more careful analysis suggests why this means that Earth Planets are even more rare than previously thought.

First, most scientists accept that "binary" star systems (or - any arrangement where 2 or more stars rotate around each other) are not likely to have any conditions necessary to support life. The constantly changing gravitational stresses would probably prevent the formation of any planet that could support life, and if a planet existed - the constant upheavals, earthquakets, etc. would be catastrophic. [Oh, By The Way ... 70% of the stars are not "by themselves" ... and are in binary or higher configurations.]

Again, most scientists agree that the center of a galaxy, where 20 - 30% of the stars are in much higher density, the radiation levels are very high, and would not be conducive to life.

And most scientists agree that stars on the very outer reaches of a galaxy probably lack the "super nova" remnants that provide the heavy elements that are found on the Earth (elements with an atomic number greater 56 (Fe - iron). What would happen if a small earth sized planet formed but there was nothing heavier than iron??

So the first 3 suppositions remove possibly 95% of the stars from being considered as possibly supporting life.

The latest analysis considers the way planets form. The analysis suggests that perhaps a more normal way for planets to form is not the way our planets formed around our Sun. Suppose that 80% of the time, the method of planet formation is what we see elsewhere (large gas giants, closer to a star). .. and that method would not be conducive to creating a small planet that would be habitable to life ... This means that once again, we are removing additional stars from consideration where life might form.

Mike

46 posted on 07/30/2004 12:15:28 PM PDT by Vineyard
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To: TonyRo76
Humanistic science, however, has a tendency to declare things dogmatically that directly oppose Scripture

a) I'm not aware of the branch of science called "Humanistic science."
b) Don't anthropomorphicize science. It doesn't "declare" nor does it have "tendencies." It just is.
c) Scientific thought is not concerned with Scripture any more than it is concerned with the Quran, the Upinishads, the Norse mythology, or Navajo campfire stories. It just is.
d) Of course, maybe I'm wrong (something we say in science), so maybe you can point to me where science "directly opposes Scripture."*

*That is, in the sense in which you are speaking. Of course, science DOES indeed oppose scripture since there are no ghosts, no one rises from the dead, no one has changed water to wine, burning bushes have not been shown to speak, people have not been shown to live 900 years, plants have not been shown to live without sunlights, etc. But I know that's not your point, I digress and I apologize in advance.
47 posted on 07/30/2004 12:16:52 PM PDT by whattajoke
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To: Pres Raygun
These factors alone remove several orders of magnitude from the number of possible stars that could sustain higher forms of life.

Still leaving a fairly large number in the end.

Just a thought: If we only find ONE other inhabited planet in the entire galaxy will the Bible Thumpers admit defeat and all become atheists? How about two planets? What's the end-of-Religion threshold?

Hint- The Americas are not mentioned ANYWHERE in the Bible, finding land and 'Injuns' didn't make the Church crumble. So, why do the Bible Thumpers fear life anywhere but here?

hmmm?

48 posted on 07/30/2004 12:19:30 PM PDT by null and void (Freedom is written with blood on the streets, not with ink in congress.)
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To: thecabal

Re the scripture which may indicate that there may be no other earth like planets in the universe. The following is from Genesis, Chapter 1. Note it is said he made the stars also and set them in the firmament to give light upon the earth.
1:14
And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
1:15
And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.
1:16
And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: [he made] the stars also.
1:17
And God set them in the firmament of the heaven to give light upon the earth,


49 posted on 07/30/2004 12:24:22 PM PDT by Rock N Jones
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To: Bikers4Bush
All I know is that if space is infinite then there has to be at least one.

You just blew my mind! ;-)

50 posted on 07/30/2004 12:26:23 PM PDT by HitmanLV (I will not be pushed, filed, stamped, indexed, briefed, debriefed or numbered. My life is my own.)
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