Stephen Hawking wants to send tiny space probes to the stars

13 photos: Cool unmanned space missions

Dawn – NASA's Dawn spacecraft began orbiting the dwarf planet Ceres in March. Scientists were surprised by the large white spots shining on Ceres, seen above. On its way to Ceres, Dawn spent time studying the proto-planet Vesta in 2001. Ceres and Vesta are the two most massive bodies in the main asteroid belt between Mars and Jupiter. The mission, launched in 2007, is giving scientists new knowledge of how the solar system formed and evolved.

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13 photos: Cool unmanned space missions

Deep Impact/EPOXI – NASA's Deep Impact spacecraft was launched on January 12, 2005, and it traveled 268 million miles (431 million kilometers) to hurl its coffee table-sized probe into comet Tempel 1 on July 4, 2005. This image of Tempel 1 was taken by Deep Impact's camera 67 seconds after the probe hit the comet. Scattered light from the collision saturated the camera's detector and caused the bright splash seen in this image. The Deep Impact mission was supposed to end a few weeks later, but NASA approved an extension and renamed the spacecraft EPOXI and sent it on to fly by Comet Hartley 2 in November 2010. The probestopped communicating with mission managers in September 2013 and was declared lost.

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13 photos: Cool unmanned space missions

Cassini – The Cassini spacecraft moves in for a closer look at Saturn. Two pictures taken during the spacecraft's approach to the planet in May 2004 were combined to create this mosaic of Saturn, its rings and several of its icy moons. Cassini was 17.6 million miles (28.3 million kilometers) from Saturn when the images were taken. The probe was launched on October 15, 1997, from Cape Canaveral Air Force Station in Florida. It arrived at Saturn on June 30, 2004. The spacecraft dropped a probe called Huygens to the surface of Saturn's moon Titan. It was the first landing on a moon in the outer solar system.

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13 photos: Cool unmanned space missions

Stardust – The Stardust spacecraft was launched on February 7, 1999, from Cape Canaveral, Florida. After traveling 3.5 billion miles (5.6 billion kilometers), the spacecraft made history by capturing images of asteroid Annefrank and collecting samples of comet Wild 2 and successfully returning them to Earth. It also took spectacular images of comet Tempel 1. The probe's mission ended on March 25, 2011, when mission managers put it in safe mode and turned off the transmitter for the last time.

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13 photos: Cool unmanned space missions

Voyager 1 and Voyager 2 – Of all the NASA missions, none has visited as many planets, rings and moons as the twin Voyager 1 and Voyager 2 spacecraft, which were launched in 1977. Each probe is much farther away from Earth and the sun than Pluto. In August 2012, Voyager 1 made the historic entry into interstellar space, the region between stars. Scientists hope to learn more about this region when Voyager 2 reaches interstellar space. Both spacecraft are still sending scientific information back to NASA.

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13 photos: Cool unmanned space missions

Surveyor – Surveyor 1 was the first U.S. spacecraft to make a soft landing on the Moon. The program ran during the mid-1960s and was declared a success. The program's focus eventually switched to support of the Apollo program.

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13 photos: Cool unmanned space missions

Explorer 1 – A model of Explorer 1, America's first satellite, is held by, from left, NASA official William Pickering, scientist James Van Allen and rocket pioneer Wernher von Braun. The team was gathered at a news conference at the National Academy of Sciences in Washington to announce the satellite's successful launch. It had been launched a few hours before, on January 31, 1958.

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13 photos: Cool unmanned space missions

Breakthrough Starshot – This illustration shows light beams from Earth pushing a tiny spacecraft's sail. The proposed Breakthrough Starshot project would send hundreds of "nanocraft" space probes 4.37 light years away -- at speeds of up to 100 million miles an hour -- to to explore Alpha Centauri, our nearest star system. The ambitious project is many years away from becoming reality.

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Story highlights

• Astrophysicist Stephen Hawking announced the ambitious Breakthrough Starshot project on Tuesday
• The project would send hundreds of tiny space probes to explore Alpha Centauri, our nearest star system

(CNN)Imagine hundreds of spacecraft the size of a butterfly, propelled by light beams at record-shattering speeds and journeying to distant stars 4.37 light years away -- far deeper into space than human-built probes have ever ventured.

It's arguably the most ambitious space exploration project in history, and it may not be completed in our lifetimes.

But if anyone can pull it off, it's these guys.

Some of the world's most brilliant minds, including physicist Stephen Hawking and Facebook founder Mark Zuckerberg, are behind a $100 million program to send tiny "nanocraft" to explore Alpha Centauri, our nearest star system.

"Today, we commit to this next great leap into the cosmos," Hawking said alongside billionaire entrepreneur Yuri Milner at a press conference Tuesday in New York. "Because we are human, and our nature is to fly."

Hawking, Milner and Zuckerberg make up the board of directors for the mission, which is called Breakthrough Starshot and seeks to apply Silicon Valley ingenuity to space travel. The project is led by Pete Worden, former director of NASA's Ames Research Center, and advised by a committee of top scientists and engineers.

Their plan goes like this: They hope to build hundreds of little space probes, each weighing just a few grams and carrying cameras, photon thrusters, power supply, navigation and communication equipment. A rocket would ferry these nanocraft into space, where they would unfold tiny sails.

Powerful laser beams from Earth would then push the sails, propelling the little nanocraft up to 100 million mph -- that's 20% of light speed, far faster than today's spacecraft can travel -- to Alpha Centauri, where they would collect images and other data and beam them back to Earth.

Project leaders estimate that today's fastest spacecraft would take about 30,000 years to reach the Alpha Centauri star system, some 25 trillion miles away. But they believe these nanocraft could fly more than 1,000 times faster, which would allow them to reach Alpha Centauri in about 20 years.

The project's leaders admit they face big engineering challenges, and that any launch is many years and billions of dollars away. But they say their plans are based on technology that already exists or is likely to become available soon.

They also plan to ask the world's scientists for their help by posting public-domain research andsoliciting ideas online.

Some scientists are skeptical they can make this happen, given the current limits of technology and the difficulty of raising enough money to fund the project. The Russian-born Milner estimates it could cost as much as $10 billion.

But he and his colleagues for now are optimistic.

"The human story is one of great leaps," Milner said in a statement. "Fifty-five years ago today, (Russian cosmonaut) Yuri Gagarin became the first human in space. Today, we are preparing for the next great leap -- to the stars."

CNN