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f c , creatures with the technology to send out signals; and L, the longevity of civilisations. N is the number of stars meeting all these criteria. Of all the factors in the equation only one, R*, is anywhere near to being understood. It represents the number of stars and we do know that there are a lot of them - more than 100 thousand million, or maybe as many as 400 thousand million in our galaxy alone. Eventually with the help of what they call the Terrestrial Planet Finder or TPF (a piece of equipment that has not yet been developed) that the researchers hope to solve the third factor in the Drake equation, n e, the number of planets with inhabitable environments. They might even be able to solve factor fl , those on which life has originated. TPF would capture the feeble light from a distant rocky planet, while cancelling out the far more brilliant light of its star. The amount of planetary light they could detect might amount to only one pixel. This minute quantity of light could then be examined for what are called the spectral signatures of, for example, oxygen, methane, ozone or some other clue to the possible presence of life. The forms of life that we know on Earth are dependent on liquid water and organic molecules, mostly made up of carbon. But even on Earth, the huge and widely differing conditions under which life can exist are amazing. Life is found in the sea and on land; in almost waterless desert conditions; in the Arctic and in the tropics; in the darkest depths of the ocean; in deep caves - and, in fact, almost anywhere. Some life forms can go without food for months and even years; some can lie dormant for great lengths of time and then seemingly revive; some can get their nourishment by dissolving rock and living off the chemicals in it. It’s also been suggested that there might be other forms of life in the universe quite unlike anything on Earth: life based perhaps on silicon instead of carbon; life that drifts in the atmosphere above a planet, and so on. A new SETI programme was initiated in 1992 at the world’s largest radio telescope at Arecibo, Puerto Rico. In 1993 the US Congress withdrew its support for the programme, but it has been continues under private sponsorship. In May 1999 the SETI@home project was set up. This harnessed the power of millions of home computers to analyse signals picked up by a detector on the Arecibo radio telescope. So far results have been disappointing in spite of 40 years of searching. On one occasion it was thought that what might be an artificial signal had been detected, but it wasn’t repeated and it couldn’t be confirmed as anything out of the ordinary. What seems to be a more promising line of investigation than the SETI programme is the search for stars, which might have planets orbiting them. In 1994, a Ph.D. student at the University of Geneva called Didier Queloz saw that a star he was observing appeared to be rocking back and forth. This phenomenon of wobbling stars has since been discovered to indicate the presence of a planet orbiting the star. With the existing technology in the nineteen nineties it was quite impossible to see such a planet, even with the most powerful optical telescopes, but it is hoped that it will become possible to mask the strong light from a star so as to enable observers to see at least its largest planets. This has been compared to seeing a firefly in the beam of a searchlight or lighthouse many miles away. By the year 2000 astronomers had detected at least 22 planets outside our solar system thanks to this discovery of star wobble and their number is continually increasing as more and more are discovered. So far, only very large planets are detectable by this means: gas giants or planets with a mass much greater than that of the Earth. Researchers are calling these remote gas giants ’Jupiter’s’ after the planet of that name in our own solar system. What haven’t been found yet are rocky planets of a size similar to our planet, which is considered to be the best habitat for forms of life similar to those on Earth. Astronomers have taken to calling these ‘Goldilocks Planets’. You’ll remember that in the story the little girl Goldilocks finds the house of the three bears, tries sitting on their chairs, eating their porridge and sleeping in their beds. The porridge is too hot, too 18 Réalta – Volume 7, Issue 2 – November/December 2005 – Tullamore Astronomical Society
cold or just right, while the chairs and beds are too big, too small or just right. A suitable planet would have to be not too close to its star to be too hot for life; and not too far away from it to be too cold for life; not too big to have a crushing gravity; and not too small so that it loses its atmosphere. With the discovery of these other solar systems in our galaxy, more and more astronomers are becoming convinced that other planets like ours exist in the universe. A year or two ago David Bell (from Shannonside AC) gave us a lecture in which he argued the case for the view that our Earth might be the only planet on which life had emerged. He said at the time that he was taking up this position to provoke discussion and that he could equally argue for the opposite view that life was common throughout the universe. It seems that fewer and fewer astronomers are inclined towards what we might call the anthropocentric view, i.e. that we are unique in the universe and that Earth is the only planet where life has arisen. This is the kind of attitude that Galileo had to face when he said that the Earth went round the Sun and not the other way round. When you think how many countless millions of stars are in our galaxies and how many countless millions of galaxies there are in the universe, and how the building blocks of life can be detected even in deep space, it seems inconceivable that life is not to be found elsewhere. So the search for extraterrestrial life goes on. The National Geographic magazine has published a table showing the progress of this search as follows: 1992: Arecibo Radio Telescope Scientists announce the discovery of planets around a pulsar. They are unlike any known planets and are almost certainly hostile to life, but they are the first alien planets to be found. 1995: Haute-Provence Observatory (France) Astronomers discover a planet around a sun-like star, 51 Pegasi, by tracking stellar motions. The same technique has revealed more than 130 planets. 1999: STARE Project For the first time the shadow of a Jupiter-size planet is detected as the planet passes over the face of its star, HD 209458. 2001: Hubble Space Telescope By observing light from HD 209458 as its planet passes, astronomers see hints of a planetary atmosphere containing sodium. 2003: Keck Interferometer This equipment combines light from the two existing Keck telescopes, eliminating atmospheric ‘noise’ with what’s called adaptive optics. It searches for debris disks around stars, which could indicate planet formation, and look directly for giant planets. 2006: Large Binocular Telescope The twin mirrors of this telescope will search for debris disks and for newly former Jupiter-size planets. 2007: Kepler Mission This space-based telescope will survey more than 100,000 stars for dimming that hints at the presence of Earth-size planets. 2009: Space Interferometry Mission (SIM) This will combine light from multiple telescopes to map stars and seek planets almost as small as Earth. 2014-2020: Terrestrial Planet Finder (TPF) A two-part space mission to detect light from Earth-size planets, and search for signs of habitability. 2025: Life Finder The Space-based Life Finder will search newfound Earths for signs of biological activity. So the first part pf this challenging programme has been achieved: We know now that there are other solar systems besides our own. Other stars have planets. Now it remains to be discovered whether any of these might sustain life; what that life might be like; and last of all, whether any such life forms could be intelligent. Man has ever undertaken probably no more exciting research. This article, by Girvan, was the basis for a lecture he gave to TAS on Tuesday October 11 th . It provided a good debate afterwards, where so many avenues of discussion about the possibility of life, both as we know it, and not, and where it could exist. Réalta – Volume 7, Issue 2 – November/December 2005 – Tullamore Astronomical Society 19
Page 1 and 2: REALTA 9+- Reviews, Events And Lect
Page 3 and 4: Key organisers and folks involved i
Page 5 and 6: NEWS UPDATE From Around The Univers
Page 7 and 8: Moon discovered orbiting Solar Syst
Page 9 and 10: Two New Moons for Pluto? New images
Page 11 and 12: viewing for the most part during th
Page 13 and 14: Great Irish Women Astronomers By Gi
Page 15 and 16: One would expect one or some of the
Page 17: Goldilocks and the (many) more than
Page 21 and 22: SPACEFLIGHT News Russian Spacecraft
Page 23 and 24: Contributions Wanted Do you ever no

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