Above: An animation showing the “photogravitational assist” at Alpha Centauri A.

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For this plan to work, the probe would redeploy its sail on arrival, leveraging the incoming radiation from the stars in the Alpha Centauri system. Using a computer simulation, Heller and Hippke based their calculations on a 100-gram space probe attached to a 100,000-square-meter sail, which is about the size of 14 soccer fields. As the probe gets increasingly close to the star system, the braking force increases.

On arrival, instead of using solar photons as a propulsion force, the sail “catches” the outgoing solar radiation from Alpha Centauri, gradually slowing the vehicle down. Ironically, the same physics that will push the probe away from our solar system will be used to slow it down at its destination.

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During the deceleration maneuver, the tiny probe will need to approach the star Alpha Centauri A to within five stellar radii (i.e. a distance equal to five-times the width of the star), or about four million kilometers, in order to be captured into orbit. By this point, the nanocraft will have slowed down to about 2.5 percent the speed of light. Failure to slow the craft down from its maximum cruising speed (4.6 percent the speed of light) would fling the probe away and back into interstellar space.

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Once at Alpha Centauri A, the star’s gravity can be used to maneuver the probe, similar to the “slingshot” maneuvers used to direct probes like Voyagers 1 and 2 around the solar system. Theoretically, the autonomous probe could settle into an orbit around Alpha Centauri A and explore its planets. Excitingly, Heller and Hippke have also outlined a plan for sending the probe to the system’s other stars, namely Alpha Centauri B (the binary companion to Alpha Centauri A) and Proxima Centauri (a distant third star located about 0.22 light-years (1.2 trillion miles) from A and B’s common center of mass). Under this plan, it would take the probe about a century to reach Alpha Centauri A, a few days to reach Alpha Centauri B, and then another 46 years to reach Proxima Centauri.

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But the added years would be worth it. In one of the most remarkable discoveries of 2016, astronomers learned that Proxima Centauri hosts an Earth-like planet. It’s one of the most tantalizing objects of inquiry within striking distance—and we finally have a plan for observing it up close. Data collected by the probe would take a little over four years to reach mission scientists on Earth (given the extreme distances involved, we’re going to have be patient with such things, and get accustomed to such long term planning/thinking). A system for sending the data back still needs to be developed.

A battery of technical hurdles still need to be sorted out before such a mission is launched, but the researchers are optimistic. For example, some of the super-light materials required for the mission have already been produced in the lab. “We might need one or two decades to be able to build such interstellar light sails,” Heller told Gizmodo. He adds that the sail’s surface would need to be very reflective from the red to the blue part of the visible spectrum, and possibly even beyond that. “This technology is not yet available but, again, huge progress has been made in laboratories over the past few years and scientists have found...materials that can reflect up to 99.99% the amount of light that they receive.”

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Next, Heller and Hippke plan to present their study in detail to the Breakthrough Starshot Initiative at its upcoming Breakthrough Discuss meeting in Palo Alto in April.

“We are very interested in their feedback, because these people are the world’s leading experts in this emerging field of interstellar light sail research,” he said. “Then, Michael [Hippke] and I are working out ideas for an interstellar travel catalog to our most nearby stars, but this is work in progress and mostly confidential between Michael and me so far.”

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Ooooh, such a tease. As always, Gizmodo will be on the lookout for when this research is made public. Until then, let’s celebrate the fact that we’re a step closer to embarking on humanity’s first interstellar space mission.

[The Astrophysical Journal Letters]