Posted on 04/05/2005 9:36:50 AM PDT by LibWhacker
The Universe could host billions of Earths
British researchers are more confident than ever that there are "Earths" out there waiting to be discovered.
The scientists say perhaps a half of all the known planetary systems today could be harbouring habitable worlds.
It must be said most of these systems are strange places where supergiant planets orbit close in to their stars.
But Barrie Jones and colleagues say their modelling work suggests that even with this oddness, there should be room for small rocky planets.
The Open University team presented its ideas here at the UK National Astronomy Meeting on Tuesday.
They extend recent and previously published theoretical work, "putting it on a firmer modelling basis," Professor Jones told the BBC News website.
The research calculates the likely number of Earths out there, based on what we know about how planets form and the conditions needed for life - in particular, the requirement to sit in the part of a solar system that is neither too hot for liquid water, nor too cold.
'Disaster' area
"The conclusions haven't changed, I'm pleased to say. Roughly half the systems out there could have Earths in their habitable zones today and have been there long enough for life to develop," Jones added.
The limitations of current telescope technology make it extremely difficult to view so-called extrasolar planets directly.
Astronomers have therefore made most of their detections indirectly - by finding stars that appear to "wobble" under the gravitational tug of what must be nearby, very large planets.
The technique has the bias of only showing up apparently bizarre systems - where planets that are sometimes many times the mass of our own Jupiter circle their stars in orbits that are smaller than Mercury's.
And this presents a problem because current thinking holds that these huge Jupiters probably formed some way out from their stars before migrating inwards. And if they did that, the chances are they would have destroyed all in their path, including any fledging Earths.
"We've now got some simple rules for establishing how far these disaster zones extend," explained Professor Jones.
Moving zones
Encouragingly, his team finds there is plenty room and time for Earths to evolve.
"At the stage these great giants sweep through, the Earths are not formed - they are still smallish planetary embryos. They get scattered but the simulations show enough material remains that Earths can form after the migration of the great giants has taken place."
The team found about half of the known exoplanetary systems offer a safe haven for a period extending from the present into the past that is at least long enough for life to have developed on any such planets.
The situation is complicated slightly by the fact that the habitable zone migrates outwards as the star ages, and in some cases this changes the potential for life to evolve.
Thus, in some cases a safe haven might have been available only in the past, while in other cases it might exist only in the future.
These scenarios of past extinction and future birth increase to about two-thirds the proportion of the known exoplanetary systems that are potentially habitable at some time during the main-sequence lifetime of their central star.
The research by Barrie Jones, Nick Sleep, and David Underwood has been published in Astrophysical Journal.
I wonder if those "earths" have the kind of loonies that ours has.
The three keys to real estate:
Location
Location
Location
Since the alternative earths are in the wrong location (ie. far from us) they are worthless to us.
Key word.
Unless we can really master warp speed travel. Then we can send liberals to one of these alternate worlds, since they seem to live in one anyway.
What did these planets do to us to deserve that.
exoplanet ping!
"The Truth Is Out There!!"
I wonder if they know who discovered THIS earth...
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And 1,000 years, or even 10,000 years, is not much in the human time scale. We've been walking around on this planet for what, a few million years? So isn't it feasible that somewhere, some civilization could have just been a slight bit faster? Or are we really the fastest, or nearly the fastest. I just don't understand why no one has contacted us if there are so many civilizations out there.
Hey why give the liberals a chance at a better planet. I say leave them behind so they can continue saving it and we can go out and populate a few dozen of them. And when they have aborted themselves to death we can come back and reclaim the planet.
We've only been transmitting to the universe for a few decades, so almost certainly none of them would have any idea we're here. Even if there are 10,000 detectable civilizations in the galaxy, the galaxy is so big that the nearest one on average would be about 1,000 light years away. Any civilization further than 120 light years away would hear nothing but silence coming from our direction, no matter how sensitive their instruments.
Hmm.. I may need to recalculate my solution to the Drake Equation.. ;^) The frequency of close-orbit gas giants has been a key factor in 'rare earth' hypotheses of recent years. If their presence very near a star doesn't significantly diminish the formation of rocky planets, then that undercuts them in a major way.
The ability to receive radio transmissions is fairly new. Even newer is the ability to discern that radio transmissions might be sent to us from other civilizations.
Figure, SETI has actively been looking for intelligent life via radio transmissions since 1984. This gives us a 21 light-year range of possible places in the universe that might be sending us messages via light-speed radio transmissions.
21 light years is pretty small.
Furthermore, while intelligent, even highly advanced cultures may thrive on other worlds, intergalactic travel at speeds faster than light may indeed be impossible as currently theorized. Like us, these other civilizations might be unable to develop spacecraft capable of travelling through the vastness of our galaxy (not to mention the universe). This could explain why aliens aren't dropping by daily.
Or maybe we are alone (though I believe this is unlikely).
60, not 120 light years.
It was about 60 years ago our radio transmissions were strong enough to break the ionosphere's interference.
Of course, maybe it's not a swell idea to stumble around in the dark, shouting, "HERE I AM" :
http://www.amazon.com/exec/obidos/ASIN/0688139892/ref=ase_cssf-20/103-0456473-4825460
Preferably, inhabitable, but inhospitable..
Thanks for the ping!
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