Space - 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