Visions of the Cosmos
Life Among the Stars
The Search for Extra-terrestial Intelligence - SETI
by Ray Goodwin
Somewhere there are mountains
Glistening in the snow
Somewhere there are mountains
That we shall never know
Somewhere there are rivers
Flowing fast and free
Somewhere there are rivers
That we can never see
Somewhere there are oceans
And sun drenched island sands
Forests full of creatures
In vastly distant lands
Somewhere there’s a planet
Beneath an alien star
The people watch our tiny sun
And wonder where we are
One day perhaps we’ll find them
Across the void of space
Perhaps through ways as yet not known
We’ll meet them face to face
We only know of one planet where life exists. However from the evidence of the existence of extra solar planets and proto-planetary discs most scientists believe that there perhaps a few other worlds in many ways similar to our own beautiful Earth. As mentioned in the previous page it seems that in order for life to flourish it is necessary to have liquid water.
It would at first sight seem to be that the planet must orbit its star in the habitable zone. However there are other possibilities. Taking as an example Europa one of the moons of Jupiter. Because of its large distance from the Sun, Europa is totally encased in ice. However, it is believed that under the ice there is a huge planet-wide ocean of liquid water kept warm by the tidal energy supplied mainly by Jupiter and also by the other three moons - Io, Callisto and Ganymede. Callisto and Ganymede themselves as well as the moons of Saturn, Titan and Enceladus may also have hidden oceans beneath their frozen surfaces.
It is also possible that gas giant planets may be accompanied by large Earth-sized moons within the habitable zone of a parent star and thus able to sustain a biosphere.
It is problematical whether or not low mass stars known as red dwarfs may play host to life -bearing planets. Any planets in the 'habitable zone might be so close as to be tidally locked - that is to say always turning the same face towards the star. There are varying opinions but some authorities think that given the right set of weather conditions and ocean currents such planets may be able to maintain liquid water on the night side as well as on the day side.
It is therefore highly likely that quite a large number of worlds exist where the chemistry of life has evolved. However taking our own Earth as an example, the process of evolution would seem to take a very long time. We can not of course be sure that the very slow rate of evolution on our own planet is a hard and fast rule. Over the four and a half billion years of the Earth's existence life is thought to have begun around 3,800 million years ago. However it was only about 544 million years ago that the Cambrian Explosion took place when very suddenly in the geological time scale advanced multi-cellular animals began to evolve and it was only because of the existence of continental land masses that life began to conquer the land. As far as we can tell human-type intelligence only appeared about 200,000 years ago and technological civilisations around 10,000 years ago. The dinosaurs and even the most intelligent mammals did not evolve a highly technological civilisation. It may therefore be that, although our planet may not be the only example, technological civilisations may be quite rare in the Universe.
SETI- The Search for Extra-terrestrial Intelligence
In 1960 Frank Drake turned his Radio Telescope to the heavens and directed the dish to the nearby Sun-like star, Epsilon eridani and listened for signals. He did the same for another nearby star Tau ceti. It was the beginning of the radio search for civilisations beyond the Earth. Later the experiments that Drake had pioneered were formalised into an organisation called SETI. Since then the SETI Institute using massive radio telescopes has been combing the skies for an intelligent signal from a planet in another star system. One of the telescopes used in the project is the largest single dish radio telescope in the world. It is located at Arecibo and is set in the tropical jungles of Puerto Rico. It played an important role in the film ‘Contact’ by Carl Sagan. In the film the scientist Eleanor Arroway played by Jody Foster picked up signals from a planet orbiting the star Vega using the array telescope.
No signals have yet been received but one day we may detect a signal that will change our world picture forever.
Arecibo Radio Telescope
|Jodie Foster as Dr Eleanor Arroway as the scientist in the film Contact||
Jill Tarter - Director of SETI
One of the foremost astronomers of the late twentieth century was the enthusiastic and charismatic Carl Sagan. Together with his wife Ann Druyan he director the film of their book 'Contact' based on the ideas of SETI. SETI was founded by Drake whose enthusiasm drove the project onwards. Some say that the main character in the film, Eleanor Arroway was based on the director of SETI Jill Tarter.
|Carl Sagan married three times. His first wife was the famous biologist Lynn Margulis who is well known for her collaboration with James Lovelock on the Gaia Theory. They had two children Dorion and Jeremy. His second wife was the well known artist Linda Salzman and their son Nick Sagan was involved in the production of a number of star trek films. By all accounts his marriage to his third wife Ann Druyan (mother of Sasha and Sam) was extremely happy and they remained together until his early death at the age of 62. He was made most famous among the general public by his television series 'Cosmos' in 1980 and by the film 'Contact'. He made innumerable contributions to science. Carl Sagan was instrumental in persuading the authorities to fix a plaque to the Pioneer Space Craft launched in the early 1970s. If in some remote future it is found by an alien civilisation it will tell them what we looked like and where we came from.||
The 'Pioneer Plaque
Courtesy National Radio Astronomy Observatory
The arid desert valley in the Plains of St Augustin New Mexico is home to a powerful radio telescope , the Very Large Array. With its twenty-seven dish antennas, each connected to the other, spread out over 22 miles in a "Y" formation, the Very Large Array, or VLA, is capable of detecting extremely faint radio emissions from the distant stars.
However it does not have any connections with the SETI project. It was simply used for dramatic effect in the film 'Contact'.
Aerial View of the Very Large Array Courtesy NRAO/AUI Photograph by Dave Finley
The Allen Array Radio Telescope
Perhaps the use of the Very Large Array in the film was somewhat prophetic. Very recently the Allen Array Telescope has been put into operation. One of its important tasks will be to search for other civilisations.
On 11 October 2007, the University of California at Berkeley and the SETI Institute announced that the first 42 radio dishes of the Allen Telescope Array (ATA) had been activated. The Telescope is dedicated to Paul G Allen the co-founder of Microsoft. Planning for the telescope began in 2001. Eventually 350 radio dishes will be installed. The full 350-dish array, when completed in approximately three years, will have unprecedented research capabilities.
ATA opens the doors to a new era of scientific progress. The telescope’s potential discoveries include a better understanding of exploding stars (supernovas), black holes, and new, exotic astronomical objects that are predicted but not yet observed. It will also provide expanded search capabilities to determine if intelligent civilizations have evolved around other stars. The ATA is the first panchromatic, wide-angle, snapshot, radio camera ever built. It is the most effective tool to create radio images of a vast area of the sky ever placed in the hands of researchers. While making innovative observations for radio astronomy, it can simultaneously interrogate solar-type stars for artificially produced signals that would reveal the presence of extraterrestrial intelligence.
The University of California at Berkeley and the SETI Institute announced that the first 42 radio dishes of the Allen Telescope Array (ATA) had been activated. and collecting scientific data from the far reaches of the universe. This is the first phase of a planned 350 radio dishes that will advance the capabilities of radio astronomy research. Paul G. Allen, Microsoft co-founder and philanthropist whose foundation donated seed money that started the project in 2001, joined representatives of UC Berkeley and the SETI Institute to launch the array.
The Allen Telescope Array (ATA) is a radio interferometer in development in northern California, roughly 290 miles northeast of San Francisco, at the Hat Creek Radio Observatory. The ATA is jointly managed by the UC Berkeley Radio Astronomy Lab and the SETI institute. The ATA currently has 42 dishes and has a goal to expand to 350 dishes
The Kepler Mission
NASA is planning to launch the Kepler Discovery mission in March 2009. The aim of the mission is to detect for the first time Earth-like extra-solar planets.
In the words of the principal Investigator, William Borucki of
NASA's Ames Research Center in California "The Kepler Mission will, for the first time, enable humans to search our galaxy for Earth-size or even smaller planets," With this cutting-edge capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: Are there others like us in the Universe?" s a space telescope designed to survey distant stars to determine the prevalence of Earth type planets.
Kepler will detect planets indirectly, using the "transit" method. A transit occurs each time a planet crosses the line-of-sight between the planet's parent star that it is orbiting and the observer. When this happens, the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit.
We are reminded here of the transits of Venus and Mercury. From Mars the Earth would also transit across the face of the Sun from time to time. Even though the dimming of a star is very small, Kepler will be able sensitive enough to detect it.
Illustrations Courtesy NASA
Seth Shostak, a senior astronomer at the SETI Institute published in SETI's web-site puts it very dramatically:-
"Take a bare 100 watt light bulb
and switch it on. Now step back about 300 miles. Once you're in position,
arrange for a friend to slowly pass a pinhead 30 feet in front of the bulb
without notice or warning. Your job? Detect the decrease in light when the
pinhead gets between you and the bulb.
I suspect that's not something you do every day. But NASA's Kepler telescope will be doing it every half-hour for the next three years and more.
Actually, not quite. Kepler will be measuring the brightness of more than 100,000 "light bulbs."
This new NASA space-borne instrument, which is now completing its shakedown cruise, is engaged in the ultimate staring contest. Kepler will continuously monitor the luminosity of 145,000 stars in the region of constellations Cygnus and Lyra, looking for dimming of as little as 0.006 percent of a star's brightness. Unlike other schemes for finding planets around distant stars (so-called "exoplanets"), Kepler can unearth Earths. That is, it can detect worlds hundreds of light years away that are comparable in both size and orbital position to our home planet. Cousins of the Earth – and obvious candidates for life."
Artist's Rendering of Kepler's Target Region in the Milky Way
An artist's rendering of what our Galaxy might look as viewed from outside
our Galaxy. Our sun is about 25,000 light years from the center of the Milky Way.
The cone illustrates the neighbourhood of our galaxy that the Kepler Mission
will search to find habitable terrestrial type planets.
Credit: Jon Lomberg NASA
The key technology at the heart of the photometer is a set of charged coupled devices (CCDs) that measures the brightness of hundreds of thousands of stars at the same time. CCDs are the silicon light-sensitive chips that are used in today's TV cameras, camcorders and digital cameras. Kepler must monitor many thousands of stars simultaneously, since the chance of any one planet being aligned along the line-of-sight is only about 1/2 of a percent.
From 1995-1997 Jon Lomberg worked on the Warner Brothers film CONTACT, as Astronomical Visual Consultant. In this capacity Lomberg designed and
This section is also to be found with further details in the section on Extra-solar Planets
An excellent web-pages are
http://www.seti.org/Page.aspx?pid=1255 and www.seti.org
The Nature of Life