The British cosmologist, who was diagnosed with motor neuron disease aged 21, is backing the Breakthrough Starshot project.
It would see a nanocraft probe sent to Alpha Centauri in just over 20 years.
Speaking at the conference, he said: "The idea behind this innovation is to have the nanocraft on the light beam.
"Such a system could reach Mars in less than an hour, or reach Pluto in days, pass Voyager in under a week and reach Alpha Centauri in just over 20 years."
The Alpha Centauri star system is 25 trillion miles (4.37 light years) away.
With today's fastest spacecraft, it would take about 30,000 years to get there.
Breakthrough Starshot aims to establish whether a gram-scale nanocraft, on a sail pushed by a light beam, can fly over a thousand times faster.
Astronomers estimate that there is a reasonable chance of an Earth-like planet existing in the 'habitable zones' of Alpha Centauri's three-star system.
It has been a busy few days for Hawking, with not just one, but two doomsday predictions for the future of the planet.
Hawking warned at a separate conference that AI could be the 'worst thing' for humanity, arguing that mankind needs to put measures in place to prevent robots from taking over. Photo / Getty
Humanity must also be prepared to tackle artificial intelligence to stop robots replacing people, he warned at the 2017 Web Summit, held in Lisbon and attended by around 60,000 people.
Hawking said the technology could transform every aspect of life but cautioned that intelligent machines pose new challenges.
He said robots are already threatening millions of jobs but that this new revolution could be used to help society and for the good of the world, including alleviating poverty and disease.
"The rise of AI could be the worst or the best thing that has happened for humanity," Hawking said via video link at the opening night of the summit on Monday.
"We simply need to be aware of the dangers, identify them, employ the best possible practice and management and prepare for its consequences well in advance."
Hawking's comments come during an escalating debate about the pro and cons of AI, a term used to describe machines with a computer code that learns as it goes.
Silicon Valley entrepreneur Elon Musk, who is chief executive of electric car maker Tesla Inc and rocket company SpaceX, has warned that AI is a threat to humankind's existence.
But Microsoft co-founder Bill Gates, in a rare interview recently, told the Wall Street Journal that there was nothing to panic about.
Hawking said everyone has a role to play in making sure that this generation and the next are fully engaged with the study of science at an early level.
He hope that this will create "a better world for the whole human race".
"We need to take learning beyond a theoretical discussion of how AI should be, and take action to make sure we plan for how it can be," said Hawking, who communicates via a cheek muscle linked to a sensor and computerised voice system.
