Image: Starship
Courtesy Adrian Mann
An artist's impression of the Icarus starship accelerating past Jupiter, gaining a valuable boost in speed with the help of the gas giant's gravity, slingshotting it toward its interstellar destination.
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updated 10/4/2011 10:48:53 PM ET 2011-10-05T02:48:53

If humans ever build an interstellar spaceship —a vehicle capable of reaching another star — one of the biggest questions will be which of the billions of stars in the Milky Way it should visit.

Scientists debated possible interstellar destinations at the 100-Year Starship Symposium, a weekend meeting here sponsored by the Defense Advanced Research Projects Agency to discuss planning the first mission to another star system.

Among the top priorities for choosing a star to target is its potential to harbor life, said astrobiologist Jill Tarter of the SETI (Search for Extraterrestrial Intelligence) Institute. [Gallery: Visions of Future Human Spaceflight]

"It's really the story of life in the cosmos that is likely to drive exploration beyond the solar system," Tarter said."I think this is the question that will be worth the effort and the pain and the investment of traveling to another star system."

Tarter and other experts agreed that any interstellar mission should try to visit a star that has planets — hopefully planets the right size and distance from their stars to host life.

The symposium is part of the 100 Year Starship Study, a $1 million, one-year project of DARPA and NASA to look into what it would take to launch a mission to another star within a century. In November, the agencies plan to award $500,000 in seed money to an organization that can spearhead the effort to research the necessary technology and logistics.

Narrowing down the options
Having planets isn't the only qualification the chosen star must meet. Another important criterion is its distance from Earth — the closer, the better.

At 4.4 light-years away from the sun, Alpha Centauri is our nearest stellar neighbor, putting it at the top of the list of candidates. However, even Alpha Centauri would be a long trip. One light-year, the distance light crosses in a single year, is about 6 trillion miles (10 trillion kilometers).

To put such a distance in perspective, one speaker at the symposium suggested an analogy: If Earth was here in Orlando, and Alpha Centauri was in Los Angeles, then the entire solar system would span only 1 mile (1.6 kilometers).

The farthest any human-made object has ever traveled is approximately to the edge of the solar system. That object, the Voyager probe, is traveling at 38,000 mph (61,000 kilometers per hour). While that might sound speedy, it's no match for interstellar distances.

For a true interstellar mission, scientists will have to develop new means of propulsion, such as nuclear-powered engines.

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Project Icarus
One group working on the problem is Project Icarus, a joint endeavor by the Tau Zero Foundation and the British Interplanetary Society, to design an interstellar spacecraft. This first potential mission would not carry humans onboard, but would aim to send robotic probes to investigate a nearby star and its environs.

"The way to view it would be an incremental approach," said Icarus designer Ian Crawford, a planetary scientist at Birkbeck, University of London. "We would probably stick with a closer target initially to develop the expertise of interstellar spaceflight. Then you can move on to more distant targets. I don't think it's wise to bite off more than you can chew initially."

Project Icarus has chosen to give itself a deadline of 100 years, meaning the spacecraft must be able to reach its destination within a century, preferably sooner, of launching. [Most Extreme Human Spaceflight Records]

The Icarus designers are focusing on building a nuclear-powered spacecraft, which they hope would be able to travel at up to 15 percent the speed of light (light travels at 186,000 miles per second, or 300 million meters per second). At that rate, the farthest the Icarus spaceship could reach in 100 years would be about 15 light-years away.

That still leaves plenty of options.

Top candidates
Within 15 light-years of the sun, there are 58 known stars in 38 separate stellar systems (many of the stars are in binary pairs). Of those 58 stars, two are currently known to have planets.

However, because extraterrestrial planet-hunting is just heating up, scientists expect many of the others also host planets that just happen to be currently undetectable.

However, even the two nearest stars known to have planets are still good initial candidates.

One is called Epsilon Eridani, and lies 10.5 light-years away. It is known to have a planet with about one and a half times the mass of Jupiter, and also has a disk of dust around it that suggests there are likely other, smaller planets present, too.

The second candidate is called GJ 674. At 14.8 light-years away, this one is pushing right up against the 15-light-year limit, but it could still be a viable option, experts said.

And don't forget Alpha Centauri. Though no planets have yet been discovered around this star, that doesn't mean there aren't any.

"My own view is that Alpha Centauri will only lose its place at the top of the list if we determine that it doesn't have a planetary system," Crawford said.

The science of detecting alien planets is developing quickly, and researchers will probably have a much better idea where the nearby planets are by the time the first interstellar spaceship is ready to fly.

"The main thing to note here is that long before we can build an Icarus vehicle, astronomical tools will have told us where the planets are orbiting nearby stars," Crawford said. "Within 100 years, I'm reasonably confident we'll have a complete inventory. I think the take-home message here is, by the time we're ready to build an interstellar vehicle, we will in fact know where to send it."

You can follow Space.com senior writer Clara Moskowitz on Twitter @ClaraMoskowitz. Follow Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Explainer: 10 pieces of Star Trek tech

  • Paramount Pictures

    The latest reboot of the Star Trek franchise follows the story of a young James Kirk on his way to becoming captain of the Starship Enterprise. The movie gives Trekkies a fresh dose of fictional high-tech wizardry. But is any of this possible in the real world? Click the "Next" arrow above to see how 10 pieces of Trek tech, from teleportation to warp drive, are faring here on Earth.

    -- By John Roach, MSNBC contributor

  • Teleportation: a work in progress

    Ray Strange  /  AFP via Getty Images file

    "Beam me up, Scotty!" Oh, how easy travel would be if the technology existed to disintegrate our bodies in one place and nearly instantaneously make them reappear at our destination. Unfortunately, that kind of teleportation remains firmly fixed in the realm of Star Trek fiction. However, scientists are meeting with some success as they try to teleport messages encoded in beams of light across table-length distances, such as this experiment from 2002. More recent advances include teleporting information from one trapped atom to another.

  • Tricorder-like device scans for cancer

    Boris Rubinsky et al.

    Star Trek fans know tricorders as familiar handheld devices that scan unfamiliar planets (and organisms). Real-world citizens, too, are becoming familiar with a host of futuristic gizmos that do everything from reading a critter's DNA to scanning patients for cancerous tumors, as shown in this side-by-side comparison of a fictional tricorder (left) and a medical scan of simulated breast tumor displayed on a cell phone.

  • Deflector shield envisioned for Mars missions

    Ruth Bamford And John Bradford

    A so-called deflector shield surrounds the Starship Enterprise, protecting the spacecraft and its crew from lethal doses of radiation. Lab experiments now suggest that a portable magnetic shield could protect real-life astronauts on a mission to Mars. The shield would force harmful particles to curve around the ship. The engineering details remain to be worked out, and for now, the shield protects only against particles from the solar wind. Gamma rays and X-rays would remain a threat. An artistic depiction of the technology deployed on the Enterprise is shown here.

  • U.S. Air Force develops PHaSER

    Image: PHaSER
    U.s. Air Force

    The weapon of choice for Trekkies is the phaser, a device that directs an adjustable beam of energy at its target. The phaser is capable of a range of effects, from a momentary stun to instant obliteration. The U.S. Air Force has developed its own prototype device with the Star Trek moniker PHaSER (Personal Halting and Stimulation Response). The hefty gunlike device was originally developed to blind an attacker temporarily. A second laser has since been added capable of heating up skin.

  • Holodeck tech emerging

    Tom Uhlman  /  AP

    Starfleet members seeking knowledge or fun can step into holodecks to experience an interactive virtual reality eerily close to life itself. Similar technologies are beginning to emerge in the real world, including this 3-D lab at Wright State University in Ohio, where businesses can use the technology to speed up and improve the designs of products. An energy company is using it to enhance their search for oil. Other firms are embracing advances in video and audio technology to make telepresence, or videoconferencing, more realistic. The most lifelike experiences, however, remain in science fiction.

  • Tractor beam manipulates cells on a chip

    MIT

    In Star Trek, tractor beams are used by starships and space stations to control the movement of objects usually to pull them in closer, tow them along, or push them away. Researchers at the Massachusetts Institute of Technology have used a tractor beam of light to pick up, hold and move around individual cells on the surface of a microchip. To demonstrate the technology, the researchers moved around and held in place 16 E. coli cells to spell out MIT, as shown in this image.

  • Cell phones are pretty good communicators

    Apple Inc. via AP

    Trek-style communicators are those little devices, handheld or sometimes worn as a badge, that allow Starfleet members to speak to others in different parts of the ship or different parts of a planet. Modern-day cell phones, including the iPhone shown here, just might wow even the likes of Captain Kirk.

  • Universal translators making strides

    iTRAVL

    In Star Trek, language is seldom a barrier thanks to universal translators, devices that allow people of different tongues to converse. Communication among cultures in the real world remains a challenge, but basic words and phrases are no longer stumbling blocks, thanks to gadgets such as the translator from iTRAVL shown here. Speak into the device, and it will translate the word or phrase and speak it aloud.

  • Cloaking devices coming out of hiding

    Naomi Halas, Rice University |

    Cloaking devices are rampant in science fiction, from Star Trek to Harry Potter but they are no longer confined to the imagination. Real-world scientists are creating new materials that manipulate wavelengths of light in ways that can hide objects from detection. This graphic shows the basic design of a 3-D metamaterial lined with nanocups that redirect the flow of light that hits it, making the object invisible.

  • Warp drive? Don't bet on it

    Les Bossinas  /  NASA

    The Enterprise can travel faster than light via something called warp drive — essentially, a device that warps the space-time continuum around a starship. Many scientists have batted around ideas about how to achieve blistering speeds in real life, but most experts have concluded that, at least for now, warping the fabric of space is beyond human understanding of the laws of physics. Among the difficulties is harnessing the energy required to kick-start the propulsion.

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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