Interstellar travel - once the stuff of science fiction - is now being taken seriously by none other than Daniel S Goldin, head of the National Aeronautics and Space Administration (Nasa) in the United States, who has ordered his brightest scientists to find a way of sending a space probe beyond the Solar System.
Mr Goldin has directed Nasa's Office of Space Science to draw up proposals for building a space vehicle of the 21st century and he has asked the Jet Propulsion Laboratory in California to set up a task force for drawing a ''route map'' to the stars.
Recent findings suggesting there may be water-bearing planets orbiting our nearest stellar neighbours - raising the distant prospect of alien life - have spurred efforts to turn the science fiction of interstellar travel into reality.
At a brainstorming session of some of the world's leading authorities on space travel, held last month at the California Institute of Technology (Caltech) in Pasadena, scientists proposed futuristic power sources for propelling spacecraft thousands of times further than the Sun.
"I think Nasa is serious about developing advanced propulsion, but whether these space vehicles will take us to the nearest stars is not yet known," said Dr Richard Mewaldt, a Caltech physicist who attended the meeting.
"But they would get us into interstellar space, and the planets of our own solar system, in a far shorter time than we can today."
Conventional rocket technology would not be suitable for interstellar travel. Just travelling to the edge of the Solar System - to a point known as the heliopause, where the solar wind stops blowing - would take 30 years with existing rocket fuel.
The furthest man-made object from the Earth is the Voyager 2 space probe, which was launched in 1977 and has so far travelled about 70 times the distance from the Earth to the Sun. It is expected to run out of fuel in about 2020, when it will be no more than about twice this distance.
Going to the stars is even more daunting. It would take more than four years for a spacecraft travelling at the speed of light to reach our nearest stellar neighbour, the star Proxima Centauri.
Dr Andrew Coates, a physicist at the Mullard Space Laboratory at University College London, said Nasa is nevertheless serious about interstellar travel.
''There is great interest in exploring this interstellar space because so little is known about it. A probe that can travel this distance is being taken very seriously and it could be launched as early as 2010, or even before that if we have a breakthrough,'' he said.
If a space probe can be built to go beyond the edge of the Solar System it can search for the elusive Oort Cloud, a cosmic maternity ward for billions of comets, Dr Coates said.
Nasa is investigating several alternatives to rocket technology. One of the most promising is a plan to launch lightweight spacecraft using powerful laser beams.
Leik Myrabo, professor of engineering physics at Rensselaer Polytechnic Institute in Troy, New York, has successfully test-fired a prototype miniature space vehicle, which he has managed to launch 30 metres into the air using a military laser gun.
One advantage of this is that the spacecraft's launch motors - the laser - are left behind, enabling them to be reused, in addition to making the spacecraft lighter. ''We're trying to defeat gravity at a cost that is far cheaper than rockets,'' Professor Myrabo said.
Another idea is for interstellar spacecraft to deploy large ''solar sails'', which can use the energy of the solar wind to propel them into interstellar space, said Dr Mewaldt. "There is a whole series of new spacecraft technology you can think about to accomplish interstellar travel. One could imagine in five years you could launch a spacecraft to test these concepts,'' he said.Reuse content