Posted on 09/27/2003 7:19:20 AM PDT by KevinDavis
The question of whether we're alone in the universe just got a lot bigger.
Two astronomers from the University of New South Wales, Australia - Dr Charles Lineweaver and Daniel Grether - have found that at least 25 per cent of Sun-like stars have planets.
"This means there are at least 100 billion stars with planets in our Galaxy," says Dr Lineweaver, a Senior Research Fellow at the University's School of Physics.
Until now, astronomers believed that only five to 15 per cent of Sun-like stars had orbiting planets, but Lineweaver and Grether's work shows that previous estimates under-reported the proportion of so-called extrasolar planets.
The Astrophysical Journal, the world's leading journal of astrophysics, has accepted their research for publication.
Astronomers have been carefully monitoring 2,000 nearby stars for the presence of orbiting extrasolar planets.
"To date, they've detected a hundred or so, meaning the fraction of stars with extrasolar planets was around five per cent," says Dr Lineweaver.
"But most planets are too small or take too long to orbit their host stars to be detected. For example, if the Sun were one of the stars being monitored, we still wouldn't have detected any planets around it.
"Using a new method to correct for this incompleteness, we found that at least 25 per cent of Sun-like stars have planets."
Dr Lineweaver believes that the figure of at least 100 billion stars with orbiting planets could be on the low side when it comes to cosmic counting. It could be that close to 100 per cent of stars have planets.
"Given that there are about 400 billion stars in our Galaxy alone, it means there could be up to 400 billion stars with planets," he says.
"With about 100 billion galaxies in the observable universe, our result suggests that there are at least 10 trillion planetary systems in the Universe."
'What Fraction of Sun-like Stars have Planets?' by Charles H Lineweaver and Daniel Grether will be published later this year. It is available online.
Dr Lineweaver is an ARC Senior Research Fellow and Senior Lecturer, School of Physics, UNSW. Daniel Grether is working on a PhD.
IOW, even if there is a great deal of life in the galaxy it doesn't mean that The Earth won't remain, effectively, "lonely".
I'm a skeptic, frankly. I don't think we will detect extraterrestrial life anytime soon (say within the next hundred years). In fact, and of course I'm just guessing, I don't think the probability is particularly good that we will discover it in the next thousand years, even though I also tend to think that extraterrestrial life does exist.
Question... and would we know intelligence if we saw it..?
Uh, that's GENERAL Hammond. The Colonel is O'Neal.
Hey! The galaxy grew again!
Qball phone home!
Kidding, right? You can't even find a great apartment in 20-30 years.
Here's what will happen: we will find a planet close enough so that we can transform it to a base condition we like. This transformation will take a really long time, a million years just to pick a number. But we will find a close enough planet in 20-30 years, it just won't be what Joe Sixpack would call earthlike.
Ever is a big word.
The problem is this: currently, we detect extrasolar planets by watching for stars that wobble slightly when orbited by a close-by dark object. Ths technique allows us to find planets anywhere in the sky, but only planets large enough to cause their star to wobble. If we could look at our own solar system from a distance, we would find it difficult to even detect Jupiter with this method. This is why, although we're seeing lots of planets out there, we can only see very large ones.
Using the transit method would allow us to see much smaller planets. Although to use the transit method we are limited to stars whose planetary orbit planes happen to coincide with our line of sight, the idea behind Kepler is that if we survey a sufficiently large number of stars, we will find a few that happen to present at exactly the right angle. From these, we can then estimate how many planets there are in the sky.
Just ask Colonel Hammond.
You tell Colonel Hammond that I don't want to go to abydos! :)
At first measurement, there were only 40 billion candidates and with this article the estimate has jumped by 60 billion and, as techniques refine there may be 400 billion "sun-like stars."
All the while, "...if the Sun were one of the stars being monitored, we still wouldn't have detected any planets around it."
Thus, even though we have tremendously increased the odds of finding more planets in the universe , we can't find the one planet that we know has intelligent life.
We are reduced to looking where the light is best for something we have proven we cannot find.
He's been a general for a number of years now. And really, I'll go anywhere he wants me to. Just so long as he sends me with a zat -- and Major Carter.
I believe in the Rare Earth Hypothesis, which includes the prediction that the skies are filled with planets teeming with life.
This is however only primitive types of life, such as dominated the earth for several billion years, up until (comparatively) very recently.
This is verrry interesting in that it is the polar opposite of the article which formed the basis for the now pulled thread Solar System Formation. That base article is here: http://xxx.lanl.gov/PS_cache/astro-ph/pdf/0207/0207536.pdf
In that article, the scientists create an improbable scenario for planet formation which must begin with a large surface area of one kilometer. That would mean fewer planets ought to be expected, fewer still of our type. On the pulled thread I asked whether dark energy should have been considered. I pose the question again here.
I believe dark energy ought to be relevant to planet formation in that negative gravity would create acceleration in every direction, causing additional pressure on particles in the intervening space to bind. It seems to me this additional pressure would be actualized as heat in the particles, thus providing for binding of particles smaller than a kilometer.
If dark energy is negative gravity, then it would not exist in the presence of positive gravity and thus could not be measured in local space laboratory experiments. It would have to be inferred from deep space observations, like we infer black holes from other evidence.
My deduction is based on the "duality" between gravity and space/time. Positive gravity should be visualized as an indentation of space/time causing approaching objects to orbit and spin downwards into the indentation. And conversely, objects within the indentation much achieve an escape velocity to get outside the horizon of its space/time geometric effect.
Therefore, if dark energy is negative gravity the reverse would be true. It would be an outdent of space/time causing objects in its horizon to be repelled - or accelerated. Like the positive gravity indentation, the outdent would create acceleration in every direction.
The implication of this thought experiment is that negative gravity, like positive gravity, would be be very small compared to the other fields (electromagnetic, strong and weak atomic) --- but would accumulate over distance.
Consequently, I would expect planetary formulation in environments which would not begin with one kilometer sized planetisimals to infer the existence and effect of intervening dark energy. Dark energy accounts for 73% of the mass of the universe.
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