My first Magazine Sky & Telescope - 04.2019

F us S tars, Part II “If we shoot to where we think Proxima will be in 50 years, we will miss it by several astronomical units,” Kervella says. “At the moment we don’t have the accuracy for that: If we project, a research and engineering initiative that shoot to where we think Proxima will be in 50 years, we will he endowed with $100 million. Its goal is to create miss it by several astronomical units,” Kervella says. a proof-of-concept design for light-propelled nano- If habitable planets are found in Alpha craft, tiny space probes accelerated by a Centauri, there’s no doubt that humans giant laser on Earth that could reach Alpha will eventually want to go there. But would Centauri in a human lifetime. These probes THE PLANET that ever be feasible? If sending a tiny probe will have a small light-sail that the laser’s THAT WASN’T is already sci-ﬁ, dispatching a craft large photons will slam into, accelerating the Astronomers haven’t enough to hold a crew could be impos- craft up to a ﬁfth of the speed of light so found planets around sible. Then add the difﬁculties of keeping that it can reach the Alpha Centauri system either Alpha Cen A or humans alive and sane during the long in 20 years. From there, they will take pic- B, but not for lack of interstellar journey. Even if the trip could tures and send them back to Earth. trying. In 2012, Xavier be done at half the speed of light, it would The idea sounds simple enough, but Dumusque (then at take 8 years, signiﬁcantly longer than the there are countless technological and Geneva Observatory, elusive trip to Mars that’s still beyond our scientiﬁc hurdles. Engineers will need Switzerland) and current technological capabilities. to develop the right materials to build colleagues announced As formidable as the challenge is, send- the sails, and then miniaturize sensors, that they had found ing people to the lunar surface also seemed antennas, navigation systems, and power a weak signal in B’s highly unlikely only 70 years ago. But once sources for the probes. A laser such as the light that looked like the goal was set, it was achieved in less one needed to accelerate them has never the wiggle in position than a decade. Will humankind have the been built. induced by an orbiting same resolve when it comes to crossing the Once en route, other scientiﬁc planet. But others interstellar abyss? unknowns could easily doom the mission, determined that the such as impacts with cosmic dust particles, signal was instead potentially devastating at high speeds ¢ Former S&T intern JAVIER BARBUZANO an artifact introduced a (S&T: Dec. 2016, p. 11). We don’t is a freelance journalist based in Barcelona. y the way the team even know for sure where the He’s been sending colonists to Alpha Cen- rocessed their data. target will be in 20 years to aim tauri in Civilization games for as long as he the probes, Kervella points out. can remember. 40 A PR I L 2 019 • SK Y & TELESCOPE p INTERSTELLAR TRAVELERS Researchers are working to design a fl ock of small probes that, accel- erated by a laser fl ash hitting their sails, could reach the Alpha Centauri system in 20 years.

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