Aliens Even More Likely Now To Be Out There ~ Average star has two potentially Earth-like worlds

Concept art depicting the lights of an ET civilisation on an exoplanet. Credit: David A Aguilar (CfA)

Boffins in Australia have applied a
hundreds-of-years-old astronomical rule to data from the Kepler
planet-hunting space telescope. They’ve come to the conclusion that the
average star in our galaxy has not one but two Earth-size planets in its “goldilocks” zone where liquid water – and thus, life along Earthly lines – could exist.


“The ingredients for life are plentiful, and we now
know that habitable environments are plentiful,” says Professor Charley
Lineweaver, a down-under astrophysicist.

Lineweaver and PhD student Tim Bovaird worked this
out by reviewing the data on exoplanets discovered by the famed Kepler
planet-hunter space scope. Kepler naturally tends to find exoplanets
which orbit close to their parent suns, as it detects them by the
changes in light they make by passing in front of the star. As a result,
most Kepler exoplanets are too hot for liquid water to be present on
their surfaces, which makes them comparatively boring.


Good planets in the “goldilocks” zone which is
neither too hot nor too cold are much harder to detect with Kepler,
which is a shame as these are the planets which might be home to alien
life – or alternatively, home one day to transplanted Earth life
including human colonists, once we’ve cracked that pesky interstellar
travel problem.


However there exists a thing called the Titius-Bode relation
– aka Bode’s Law – which can be used, once you know where some inner
planets are, to predict where ones further out will be found.


Assuming Bode’s Law works for other suns as it does
here, and inputting the positions of known inner exoplanets found by
Kepler, Lineweaver and Bovaird found that on average a star in our
galaxy has two planets in its potentially-habitable zone.


That doesn’t mean there are habitable or inhabited
planets at every star, of course. Even here in our solar system,
apparently lifeless (and not very habitable) Mars is in the habitable
zone.


Even so, there are an awful lot of planets in the
galaxy, so some at least ought to have life on them, and in some cases
this life ought to have achieved a detectable civilisation. Prof
Lineweaver admits that the total lack of any sign of this is a bit of a
puzzler.


“The universe is not teeming with aliens with
human-like intelligence that can build radio telescopes and space
ships,” admits the prof. “Otherwise we would have seen or heard from
them.


“It could be that there is some other bottleneck for
the emergence of life that we haven’t worked out yet. Or intelligent
civilisations evolve, but then self-destruct.”


Of course, humans – some approximations of which have
been around for some hundreds of thousands of years, perhaps – have
only had civilisation of any kind in any location for a few thousand of
those years. Our civilisation has only risen to levels where it could be
detectable across interstellar distances very recently.


There may be many planets out there inhabited by
intelligent aliens who either have no civilisation at all, or only
primitive civilisation. There may be quite a few who have reached or
passed the stage of emitting noticeable amounts of radio or other
telltale signs, but those emissions either will not reach us for
hundreds of thousands of years – or went past long ago.


It would seem reasonable to suspect that there are
multitudes of worlds out there where life exists in plenty but has never
become intelligent, as Earth life was for millions of years before
early humans began using tools really quite recently.


But the numbers are still such that the apparent
absence of star-travelling aliens could make you worry about the
viability of technological civilisation if, like Professor Lineweaver,
you learn your astrophysics out of textbooks and lectures (and publish
your research, as we see here, in hefty boffinry journals like the Monthly Notices of the Royal Astronomical Society).


But if movies, speculofictive novels and TV have taught us anything here on the Reg
alien life desk, it is that in fact the galaxy is swarming with
star-travelling aliens (and/or humans taken secretly from planet Earth
for mysterious purposes in the past, or perhaps humans from somewhere
else etc). The reason we don’t know about them is that they don’t want us to.

Source Article from http://feedproxy.google.com/~r/AscensionEarth2012/~3/pC4_LLpRxyw/aliens-even-more-likely-now-to-be-out.html

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