Space - Tullamore Astronomical Society
Space - Tullamore Astronomical Society
Space - Tullamore Astronomical Society
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f c , creatures with the technology to send out<br />
signals; and L, the longevity of civilisations. N is the<br />
number of stars meeting all these criteria. Of all the<br />
factors in the equation only one, R*, is anywhere near to<br />
being understood. It represents the number of stars and<br />
we do know that there are a lot of them - more than 100<br />
thousand million, or maybe as many as 400 thousand<br />
million in our galaxy alone. Eventually with the help of<br />
what they call the Terrestrial Planet Finder or TPF (a<br />
piece of equipment that has not yet been developed) that<br />
the researchers hope to solve the third factor in the<br />
Drake equation, n e, the number of planets with<br />
inhabitable environments. They might even be able to<br />
solve factor fl , those on which life has originated.<br />
TPF would capture the feeble light from a<br />
distant rocky planet, while cancelling out the far more<br />
brilliant light of its star. The amount of planetary light<br />
they could detect might amount to only one pixel. This<br />
minute quantity of light could then be examined for what<br />
are called the spectral signatures of, for example,<br />
oxygen, methane, ozone or some other clue to the<br />
possible presence of life.<br />
The forms of life that we know on Earth are<br />
dependent on liquid water and organic molecules, mostly<br />
made up of carbon. But even on Earth, the huge and<br />
widely differing conditions under which life can exist<br />
are amazing. Life is found in the sea and on land; in<br />
almost waterless desert conditions; in the Arctic and in<br />
the tropics; in the darkest depths of the ocean; in deep<br />
caves - and, in fact, almost anywhere. Some life forms<br />
can go without food for months and even years; some<br />
can lie dormant for great lengths of time and then<br />
seemingly revive; some can get their nourishment by<br />
dissolving rock and living off the chemicals in it.<br />
It’s also been suggested that there might be other<br />
forms of life in the universe quite unlike anything on<br />
Earth: life based perhaps on silicon instead of carbon;<br />
life that drifts in the atmosphere above a planet, and so<br />
on.<br />
A new SETI programme was initiated in 1992 at<br />
the world’s largest radio telescope at Arecibo, Puerto<br />
Rico. In 1993 the US Congress withdrew its support for<br />
the programme, but it has been continues under private<br />
sponsorship. In May 1999 the SETI@home project was<br />
set up. This harnessed the power of millions of home<br />
computers to analyse signals picked up by a detector on<br />
the Arecibo radio telescope. So far results have been<br />
disappointing in spite of 40 years of searching. On one<br />
occasion it was thought that what might be an artificial<br />
signal had been detected, but it wasn’t repeated and it<br />
couldn’t be confirmed as anything out of the ordinary.<br />
What seems to be a more promising line of<br />
investigation than the SETI programme is the search for<br />
stars, which might have planets orbiting them. In 1994, a<br />
Ph.D. student at the University of Geneva called Didier<br />
Queloz saw that a star he was observing appeared to be<br />
rocking back and forth. This phenomenon of wobbling<br />
stars has since been discovered to indicate the presence<br />
of a planet orbiting the star. With the existing technology<br />
in the nineteen nineties it was quite impossible to see<br />
such a planet, even with the most powerful optical<br />
telescopes, but it is hoped that it will become possible to<br />
mask the strong light from a star so as to enable<br />
observers to see at least its largest planets. This has been<br />
compared to seeing a firefly in the beam of a searchlight<br />
or lighthouse many miles away. By the year 2000<br />
astronomers had detected at least 22 planets outside our<br />
solar system thanks to this discovery of star wobble and<br />
their number is continually increasing as more and more<br />
are discovered. So far, only very large planets are<br />
detectable by this means: gas giants or planets with a<br />
mass much greater than that of the Earth. Researchers<br />
are calling these remote gas giants ’Jupiter’s’ after the<br />
planet of that name in our own solar system.<br />
What haven’t been found yet are rocky planets<br />
of a size similar to our planet, which is considered to be<br />
the best habitat for forms of life similar to those on<br />
Earth. Astronomers have taken to calling these<br />
‘Goldilocks Planets’. You’ll remember that in the story<br />
the little girl Goldilocks finds the house of the three<br />
bears, tries sitting on their chairs, eating their porridge<br />
and sleeping in their beds. The porridge is too hot, too<br />
18<br />
Réalta – Volume 7, Issue 2 – November/December 2005 – <strong>Tullamore</strong> <strong>Astronomical</strong> <strong>Society</strong>