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"Did Life First Appear on Alien Worlds 12-13 Billion Years Ago?" --Ask Leading A

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  • derhexer@aol.com
    A post on the possibility that alien life appeared billions of years ago. Maybe there have been a series of sterilizing events in our Galaxy every few billion
    Message 1 of 1 , Jan 1, 2013
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      A post on the possibility that alien life appeared billions of years ago.

      Maybe there have been a series of sterilizing events in our Galaxy every
      few billion years that have wiped out higher life forms?

      Have a great 2013!!

      Chris


      ____________________________________
      From: vlandi@...
      To: derhexer@...
      Sent: 1/1/2013 6:20:45 P.M. Eastern Standard Time
      Subj: The Daily Galaxy: News from Planet Earth & Beyond



      _The Daily Galaxy: News from Planet Earth & Beyond_
      (http://www.dailygalaxy.com/my_weblog/)

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      ____________________________________
      _"Did Life First Appear on Alien Worlds 12-13 Billion Years Ago?" --Ask
      Leading Astrobiologists_
      (http://feedproxy.google.com/~r/TheDailyGalaxyNewsFromPlanetEarthBeyond/~3/iCbLx3tJd_Q/astrobiologists-ask-did-life-first-appear-o
      n-worlds-12-to13-billion-years-ago.html?utm_source=feedburner&utm_medium=ema
      il)
      Posted: 01 Jan 2013 09:03 AM PST



      (http://www.dailygalaxy.com/.a/6a00d8341bf7f753ef017c35339513970b-pi)
      The abundance of _heavy elements_
      (http://en.wikipedia.org/wiki/Heavy_metal_(chemistry)) in the Universe has grown over history. In the past the
      average metallicity would be quite a bit less. Again, under the previous
      paradigm this had been assumed to preclude _rocky planet_
      (http://en.wikipedia.org/wiki/Terrestrial_planet) formation early in the Universe, but now we
      know that such planets could have been constructed in environments that
      contained much poorer levels of heavy elements.
      This means that planets that could potentially have supported life may
      have formed eight, ten, maybe even twelve billion years ago. Surveys do detect
      a decrease in the number of planet-hosting stars with decreasing
      metallicity, but this drop is much shallower for terrestrial planets than it is for
      gas giants. Of course, the presence of some heavy elements during the
      planet-building phases is required, but the minimum level has not yet been
      determined.
      The raw materials for building _terrestrial planets_
      (http://www.dailygalaxy.com/my_weblog/2012/08/vaporizing-earth-to-identify-atmospheres-of-super-ear
      ths--1.html) were available very soon after the _Big Bang_
      (http://www.dailygalaxy.com/my_weblog/2012/08/the-oldest-star-in-the-universe-closest-to-th
      e-big-bang-in-composition.html) , raising the possibility that there could
      be _life in the Universe_
      (http://en.wikipedia.org/wiki/Extraterrestrial_life) far older than ours. Perhaps they reside around long-lived red dwarf
      stars, or have moved on from their home system after their star expired. Or,
      perhaps, we really are the first, which means that if life has happened
      just once throughout the entire history of the Universe, our existence must
      be a fluke and our planet very, very special indeed.
      The _Kepler Mission_
      (http://www.dailygalaxy.com/my_weblog/2012/08/getting-closer-kepler-mission-captures-41-new-planets-in-20-star-systems.html) ,
      who's field of view encompasses 1/400th of the _Milky Way_
      (http://en.wikipedia.org/wiki/Milky_Way) , has changed the way we view exoplanets. Simply by
      observing so many all at once in its field-of-view, the space telescope is
      taking an unprecedented census of alien worlds. It has found 2,321 candidate
      planets to date, over a third of which are smaller, rocky planets
      (Jupiter-sized _gas giants_ (http://en.wikipedia.org/wiki/Gas_giant) or larger make
      up just 11 percent, with the rest being Neptune-sized worlds of
      indeterminate nature), whereas before Kepler you could count the number of rocky
      exoplanets discovered on one hand. Follow-up studies of their host stars have
      since revealed a surprising discovery.
      "We found that the existence of small planets does not depend as strongly
      on the metallicity of their star as is the case for the larger planets,"
      says Lars Buchhave of the _Niels Bohr Institute_
      (http://maps.google.com/maps?ll=55.6967472222,12.5713333333&spn=0.01,0.01&q=55.6967472222,12.5713333333%20
      (Niels%20Bohr%20Institute)&t=h) at the University of Copenhagen. Buchhave
      is lead author of a new study involving a multinational group of
      astronomers investigating the spectra of 150 stars that play host to 226 candidate
      planets found by Kepler. Their research was initially presented at the 220th
      meeting of the_American Astronomical Society_ (http://aas.org/) in
      Anchorage, Alaska this June, followed by a paper in Nature.
      "At first glance it appears very counter-intuitive that gas giants should
      be the ones caring about metallicity and terrestrial planets less so," says
      Anders Johansen of Lund Observatory in Sweden, who was a co-author on the
      Buchhave paper.
      Only when you stop to consider how planets are constructed does it begin
      to make sense. The process of accreting hierarchically from smaller building
      blocks is termed core accretion, but there has been something of a debate
      surrounding gas giants like Jupiter. Can they condense straight out of the
      gas of the solar nebula like a star, or do they need a large seed around
      which to grow by rapidly gathering gas from the _protoplanetary disc_
      (http://en.wikipedia.org/wiki/Protoplanetary_disk) in a runaway process?
      Findings that show rocky planets existing around stars irrespective of
      their heavy element abundances mean that larger areas of galaxies than thought
      could be potentially habitable.
      The preference of gas giants for higher metallicity stars indicates that
      they formed through core accretion, building up a central rocky core ten
      times the _mass of Earth_ (http://en.wikipedia.org/wiki/Earth_mass) that could
      dominate the protoplanetary disc and sweep up much of the gas before it
      dissipates after around ten million years. In lower metallicity systems there
      would not be enough heavy elements to build up large cores, leaving only
      small rocky worlds. Johansen suggests that one way of looking at terrestrial
      planets is to see them as failed gas giant cores.
      Limits to Life Planetary systems around stars possessing a deficiency in
      heavy elements might prove to be attractive locales to search for life
      because, without the presence of gas giants, life might have an easier time of
      it.
      Most of the extra-solar gas giants that we have discovered are so-called
      'hot Jupiters' located very close to their stars and completing an orbit in
      just a few days. These planets were not born this close, instead they
      migrated in-system from their birth orbits. Johansen says that more and more
      astronomers are coming around to the idea that such migration is forced by the
      gravitational pull and dynamical friction of the gas, or by close
      encounters with other planets. These interactions with fellow constituents of the
      protoplanetary disc removed angular momentum from the planets, often causing
      them to spiral towards their stars. Any smaller planets unfortunate to be
      in their way are thrown out of the system by the marauding gas giant.
      "If a Jupiter-type planet migrates and in the process scatters all the
      smaller planets away, one should probably look for terrestrial planets
      elsewhere," says Buchhave. Life may have had a more pleasant ride in the _early
      Universe_ (http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang) when,
      thanks to the lower metallicity, there were no gas giants – and the argument
      that Jupiter-sized planets are needed as a shield against comet impactors no
      longer holds water either.
      Life can do without gas giant planets. If Earth-sized planets do not
      require stars with high abundances of heavy elements, then that has huge
      implications, expanding the possible abodes for life throughout both space and
      time.
      Galaxies tend to evolve chemically from the inside out, with the highest
      abundances of heavy elements closer to the galactic center than in the
      outskirts of the spiral arms. Under the previous paradigm, the outer regions of
      the spiral arms were effectively the badlands, incapable of building
      planets or life. Yet when metallicity is no longer such a big issue, the galactic
      habitable zone – a region where environmental conditions including the
      metallicity and the rate of supernovae conspire to make habitable planets
      possible – suddenly widens to encompass much wider swathes of a galaxy.
      "I expect there will be a lower limit," says Johansen. "Simply because
      below a threshold metallicity there is not enough building material to form
      Earth-mass planets." Clearly, a heavy _element abundance_
      (http://en.wikipedia.org/wiki/Abundance_of_the_chemical_elements) a tenth of the Sun's or less
      would struggle to build any planets. However, each galaxy evolves
      differently and there is no way to say for sure when the _Milky Way_
      (http://www.dailygalaxy.com/my_weblog/2012/08/the-oldest-star-in-the-universe-closest-to-the
      -big-bang-in-composition.html) crossed this threshold, although it is
      likely to have been early in the history of the Universe, for the young cosmos
      was particularly adept at producing multiple generations of stars in quick
      succession.
      Star-formation rates of 4,000 solar masses per year have been measured
      less than a billion years after the Big Bang, compared to the paltry ten solar
      masses of gas converted into stars each year in the Milky Way.
      "A typical massive star that exploded and released heavy elements 10 to 12
      billion years ago had a metallicity of about a tenth of the Sun," adds
      Johan Fynbo, Professor of Cosmology at the Niels Bohr Institute. "But whenever
      you have a new generation of stars then you start enriching the
      interstellar gas with heavy elements."
      _Rocky planets_ (http://en.wikipedia.org/wiki/Terrestrial_planet) around
      more stars, across greater expanses of the Milky Way and going back deeper
      in time than we had ever dreamt adds more fuel to the fire of the _Fermi
      Paradox_ (http://en.wikipedia.org/wiki/Fermi_paradox) . First voiced by the
      brilliant nuclear physicist Enrico Fermi in 1950, the Fermi Paradox questions
      why, given all the stars and planets out there coupled with the huge age of
      the Universe, have no alien civilizations encountered Earth yet? Where are
      they all?
      The problem is made even worse when you consider that the first term in
      the _Drake Equation_ (http://en.wikipedia.org/wiki/Drake_equation) – Frank
      Drake's method for estimating the number of intelligent civilizations in the
      Galaxy – is the star formation rate, which on average was much higher in
      the Universe 10 to 13 billion years ago when it seems planets could first
      begin forming. In the Milky Way today the average annual star formation rate
      is ten solar masses; an order of ten or one hundred greater has the effect
      of bumping up the product of the equation: the estimated number of
      civilizations.
      One of the favorite counter-arguments to the Fermi Paradox was that the
      threshold metallicity takes time to build up, resulting in the Sun being one
      of the first stars at the required level and hence Earth would be one of
      the first planets with life. Now we see that planets and possibly life could
      have arisen at practically any point in cosmic history, undermining this
      counter-argument and once again forcing us to ask, where is everybody?
      If life did first appear on worlds 12 to13 billion years ago, then
      intelligent civilizations (if indeed they survived all this time) would now
      billions of years ahead of us and their concerns may no longer include the
      happenings on a damp mudball somewhere in the galactic hinterlands. Perhaps
      civilizations that are many billions of years old instead spend their time
      siphoning energy from black holes or living inside Dyson Spheres.
      There are, however, some twists in the tale. In 2010 researchers at the
      Max Planck Institute for Astronomy in Heidelberg, Germany, found a gas giant
      planet around a star so lacking in heavy elements that it must have formed
      very early in the history of the Universe. To add to the intrigue, the
      star, known as HIP 13044 and located 2,000 light years away, is part of a
      stellar stream that is all that remains of a dwarf galaxy that has been
      cannibalized by the Milky Way.
      This year, the same researchers found another low metallicity star with
      two gas giants. Based on its abundance of hydrogen and helium the star, known
      as HIP 11952, was born 12.8 billion years ago, a mere 900 million years
      after the Big Bang. Why gas giants have been able to form around these
      heavy-metal deficient stars is unknown, perhaps hinting at an alternative process
      for gas planet formation. On the other hand new results suggest that, in
      some regions of the Universe at least, gas giants have been able to form all
      along.
      For some faint galaxies in the distant Universe, whose light is too feeble
      to allow a measurement of their spectra, it is possible to cheat by making
      use of natural backlights such as highly luminous quasars to probe faint
      foreground galaxies. When taking advantage of this method to study the
      chemical composition of a galaxy that existed 12 billion years ago, a team of
      astronomers including Johan Fynbo made a rather surprising revelation.
      "We looked at a background quasar whose light was passing through a galaxy
      in front of it, where the light of the quasar was absorbed," says Fynbo.
      "This allowed us to see the absorption lines from oxygen, sulphur, carbon
      and all the elements that have been synthesized in the galaxy."
      Twelve billion years ago the chemistry of galaxies should have been fairly
      primitive, yet in this one particular galaxy Fynbo and his colleagues, who
      reported on their findings in Monthly Notices of the Royal Astronomical
      Society, found abundances of heavy elements equivalent to the abundance in
      the Sun.
      Such finds at high distances are not unusual in themselves, but they tend
      to occur within the hearts of quasars, across a very small area of a
      galaxy. In this instance, however, the quasar light was shining through the disc
      of the foreground galaxy revealing the solar levels of heavy elements
      52,000 light years from the center, right in the outskirts.
      Even today our own Milky Way isn't so heavily chemically processed to the
      edge of its spiral arms, so how did this distant galaxy become so enriched
      throughout its full extent so quickly? The best explanation so far is that
      a starburst – a ferociously rapid bout of star formation – within the
      inner regions of the galaxy has blown the heavy elements into the galactic
      outlands. This can be done simply though the gale force stellar winds of
      radiation emanating from hot, massive stars, or riding on the shock waves of
      supernovae.
      Furthermore, the quasar light was reddened by intervening dust in the
      galaxy. Dust is the most basic building block of planet formation, coming
      together in conglomerations and clumps that build up into protoplanets. Dust is
      also a product of the violent bombardment phase endured by young planetary
      systems and is copiously manufactured in supernovae.
      "In order to make planets you clearly need metals and that seems to be
      possible quite far out in a galaxy at a very early time, which is what
      surprised us," says Fynbo. However, such high metallicities enables gas giant
      planets to also form but, although Lars Buchhave has mentioned what
      difficulties gas giants can cause for habitable planets, they don't necessarily have
      to be a show-stopper and our Solar System with Jupiter and Saturn is not the
      only exception.
      "In the Kepler-20 planetary system there are five planets," he says,
      "Three are Saturn-sized planets and two are terrestrial-sized, with the order
      being big–small–big–small–big. If the Saturn-mass planets migrated in, how
      can the small planets be in-between the larger ones?'
      The image at the top of the page by Carter Roberts of the Eastbay
      Astronomical Society in Oakland, CA, shows the Milky Way region of the sky where
      the Kepler spacecraft/photometer will be pointing --equal to 1/400th of the
      galaxy. Each rectangle indicates the specific region of the sky covered by
      each CCD element of the Kepler photometer. There are a total of 42 CCD
      elements in pairs, each pair comprising a square.
      The image at the top of the page show the many bright, pinkish clouds in
      NGC 4700, known as _H II regions_ (http://en.wikipedia.org/wiki/H_II_region)
      , where intense ultraviolet light from hot young stars is causing nearby
      hydrogen gas to glow. H II regions often come part-and-parcel with the vast
      molecular clouds that spawn fresh stars, thus giving rise to the
      locally-ionized gas. In 1610, French astronomer _Nicolas-Claude Fabri de Peiresc_
      (http://en.wikipedia.org/wiki/Nicolas-Claude_Fabri_de_Peiresc) peered through
      a telescope and found what turned out to be the first H II region on
      record: the _Orion Nebula_
      (http://www.dailygalaxy.com/my_weblog/2012/06/the-mystery-of-the-missing-life-giving-molecule-in-space-deepens.html) , located
      relatively close to our Solar System, here in the Milky Way.
      Journal reference: Nature
      The Daily Galaxy via _NASA Astrobio.net_ (http://www.astrobio.net/)
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