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.
Planets ten times as massive as Jupiter, those are some big-ass planets.
HMMPH! Bodes well for the rest of the galaxy, then...
(sometimes it seems like ONE is too many.)
What about all the other lifeless planets and moons we can observe in our own neighborhood?
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
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?
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,
You just blew my mind! ;-)
There is also the "moon factor" which impacts the earths tilt and also provides other benefits of which I can't recall.
However, even adding all these all conditions, considering the vast number of stars out there, there has got to be a certain percentage of them which have planets capable of sustaining life. But as you and the article imply, that number may be small on a percentage basis.
And then there are alternate dimensions.
And, therefore, of course, that's the only reason anything is in space, just and only to give us light, right?
Wow, 6 posts before the hijacking attempts.
"that's the only reason anything is in space, just and only to give us light, right?"
Well, what do you think?
"All I know is that if space is infinite then there has to be at least one."
It's like multiplication by zero, the so-called "trivial solution" which gives an easy answer to a difficult and challenging problem.
So far there is no verification for the measurement of infinity, so no one knows for sure. All we know is that it's real freaking big.
Did someone mention Abortion???
A little bit of drinking wisdom that you're free to use ad infinitum.
Hence the "if" in my statement.
The Torah.
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