| Micele |
30 september 2010 10:45 |
Soit, even wat afwijken van dat hopeloos debunk hier.
Nu moeten "ze" Frank Drake en zijn bijna 50 jarige berekening nog gelijk gaan geven ook... 8-)
http://en.wikipedia.org/wiki/Frank_Drake
http://de.wikipedia.org/wiki/Frank_Drake
Ik las deze morgen iets in de krant van Gliese 581 daarom surfde ik wat naar deze kant:
Citaat:
http://news.sciencemag.org/scienceno...-in.html?rss=1
Earth-Like Planets May Abound in the Milky Way
by Phil Berardelli on 12 April 2010, 7:01 PM
Maybe Frank Drake was right. Nearly half a century ago, the American astronomer postulated that, based on pure statistical probability, the Milky Way could be teeming with Earth-like planets.
Now observations of formerly sunlike stars called white dwarfs suggest that the overwhelming majority of them once harbored at least one rocky world. And because sunlike stars could account for up to half of the Milky Way's population of several hundred billion suns, that means hundreds or even thousands of civilizations might inhabit our galaxy.
The question of how many rocky worlds exist in the galaxy has perplexed astronomers for the better part of a century. Even now, technology hampers the search. Astronomers are years away from being able to image another Earth directly. The two methods of detecting extrasolar planets, nicknamed "wobble and blink," involve plotting tiny shifts in a star's motion caused by the gravitational tug of its orbiting planets, and catching the slight dimming in a star's light that occurs whenever a planet passes between the star and an observer's telescope. Both methods have revealed hundreds of Jupiter-like planets, but not a counterpart to Earth—though a few rocky giants have been spotted.
But tomorrow at a meeting of the Royal Astronomical Society in Glasgow, United Kingdom, a team of researchers will present a new way to estimate how many rocky planets could be out there. The study centers on white dwarf stars. These dying suns once shone like our own, but late in their 9-billion-year life spans they ballooned into red giants, stars with diameters up to 200 times that of our sun. (If this happened in our solar system, the sun would expand to beyond Earth's orbit.) Then, gradually, the bloated stars shriveled to only half of their original size, slowly dimming into oblivion and surrounded by huge, thin atmospheres.
Those atmospheres can provide an easy-to-read signal that rocky planets once orbited the dying stars, according to the researchers. The team studied the spectra, or chemical signatures, of the light from 146 white dwarfs located within a few hundred light-years of Earth. Among those stars, 109 exhibited spectra indicating that heavier elements such as calcium were present in their atmospheres. Rocky planets are the only likely sources for these heavy elements, so the spectra show that the stars must have swallowed such planets during their expansive, red-giant stage.
Based on the data, the team extrapolates that at least 3.5% of all sunlike stars across the Milky Way currently harbor rocky planets. By a further rough calculation, that means the galaxy has held as many as a billion rocky worlds at one time or another. A small fraction of these, in turn, could have been Earth-like, meaning they met such criteria as harboring water and existing within a habitable distance from their suns.
The study reinforces the idea that the formation of planets around stars "is a common outcome," says planetary scientist Jonathan Fortney of the University of California, Santa Cruz. So common, he says, that the number of stars harboring rocky planets is "probably much higher" than the value of 3.5% estimated by the authors.
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vb. exoplaneten in "mogelijk bewoonbare zone van een ster, waar leven kan ontstaan ":
Citaat:
http://www.spacepage.be/artikelen/ex...lanetenstelsel
Gliese 581 c
Deze planeet (ontdekt op 24 april 2007 door Stéphane Udry van het Observatorium van de Universiteit van Genève in Zwitserland), bevindt zich waarschijnlijk (op de rand van) de bewoonbare zone. Binnen deze zone is water in vloeibare vorm mogelijk. Met een vermoedelijke temperatuur van 0 tot 40°C is Gliese 581 c de eerste planeet die vergelijkbaar is met de aarde. Recent onderzoek in 2007 duidt echter in de richting van aanzienlijk hogere tempe- raturen ten gevolge van een aanwezig “broeikas” effect, dit blijft echter onbevestigd. Ervan uitgaande dat Gliese 581 c een rotsplaneet is en geen ijsplaneet, betekent dat de doorsnede ongeveer 50% groter is dan de aarde. De zwaartekracht is naar schatting 2,2 keer sterker dan die van de aarde. De planeet heeft een omlooptijd van slechts 13 aardse dagen en de afstand tot haar ster bedraagt slechts 7% van de afstand van de aarde tot de zon. Doordat de ster kleiner en kouder is dan de zon, valt Gliese 581 c toch min of meer binnen de bewoonbare zone. De omloopbaan is mogelijk aan zijn zon gebonden, wat betekent dat de planeet tijdens zijn omloop precies éénmaal om zijn eigen as draait. Atmosferische stromingen zouden op de koude zijde misschien leven mogelijk maken.
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http://de.wikipedia.org/wiki/Habitable_Zone
Begriff
Der Begriff der habitablen Zone geht zurück auf den Astronomen Su-Shu Huang und wurde Ende der 1950er erfunden.[2][3] Der Begriff bedeutet wörtlich auf deutsch „bewohnbare Zone“. Das ist irreführend und hat zu Kritik geführt. Im eigentlichen Wortsinn bezeichnet „bewohnbar“ einen Himmelskörper mit einer voll entwickelten, für Menschen geeigneten Sauerstoff-Kohlenstoff-Ökologie. Im allgemeinsten heutigen astrobiologischen Verständnis ist mit habitabler Zone dagegen ein Parameterbereich gemeint, im dem ein Himmelskörper Leben hervorbringen kann, aber nicht muss.
Bekannte Exoplaneten in einer habitablen Zone [Bearbeiten]
Derzeit ist von keinem Exoplaneten mit Sicherheit bekannt, ob er sich in einer habitablen Zone befindet. Der beste Kandidat war zeitweise der etwa 20 Lichtjahre von der Erde entfernte Gliese 581 c, der zweite Planet des roten Zwerges Gliese 581, der aber inzwischen seinen Status als ein eventueller habitabler Planet eingebüßt hat, da er zu intensive Strahlung von seinem Stern erhält.[11] Seither ist ein anderer Planet des Systems, Gliese 581 d, ins Zentrum der Aufmerksamkeit gerückt. Der Planet mit der achtfachen Erdmasse umrundet seinen Stern binnen 84 Tagen einmal. Der Planet liegt in seinem System in einer Zone, die klimatische Bedingungen wie die des frühen Mars ermöglicht. Damit wäre er ein Kandidat für einen Planeten, dessen Bedingungen die Entstehung von Leben ermöglicht haben könnten.[12] Diese Annahmen beruhen jedoch auf Modellrechnungen, nicht auf direkten Beobachtungen, und sind von zahlreichen Modellparametern abhängig.
ook: http://en.wikipedia.org/wiki/Gliese_581_c
Citaat:
http://en.wikipedia.org/wiki/Gliese_581_d
Gliese 581 d (pronounced /ˈɡliːzə/) or Gl 581 d is an extrasolar planet orbiting the star Gliese 581 approximately 20 light-years away in the constellation of Libra. Because of its mass, between 7 and 14 times that of Earth, the planet is classified as a super-Earth. In late April 2009, new observations by the original discovery team concluded that the planet is within the habitable zone where liquid water may exist
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"ze" oefenen al :lol:
Citaat:
Messages from Earth
Another artist impression of Gliese 581 d as a Super-Earth.In October 2008, members of the networking website Bebo beamed A Message From Earth, a high-power transmission at Gliese 581, using the RT-70 radio telescope belonging to the National Space Agency of Ukraine. This transmission is due to arrive in the Gliese 581 system's vicinity by the year 2029; the earliest possible arrival for a response, should there be one, would be in 2049.[13]
As part of the 2009 National Science Week celebrations in Australia, Cosmos Magazine launched a website called Hello From Earth to collect messages for transmission to Gliese 581d. The maximum length of the messages was 160 characters, and they were restricted to the English language. In total, 25,880 messages were collected from 195 countries around the world. The messages were transmitted from the DSS-43 70 m radio telescope at the Canberra Deep Space Communication Complex at Tidbinbilla, Australia on the 28th of August, 2009.[14]
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