Interstellar Round Trip Could Return Samples From Earth-Like Exoplanet In 300 Years

An artist's impression of the spacecraft at Proxima b. Planetary Habitability Laboratory, University of Puerto Rico at Arecibo

Jonathan O`Callaghan 01 Feb 2017, 08:00

Two scientists have come up with a novel proposal to send a fleet of spacecraft to our nearest star, Proxima Centauri, and return to Earth – possibly with the first ever samples of an exoplanet’s atmosphere.

The idea is based upon Breakthrough Starshot, an $100 million initiative set up by Russian billionaire Yuri Milner last year to use a powerful 100-gigawatt laser on Earth to send small spacecraft to Proxima. Starshot could theoretically traverse the distance of 4.2 light-years to Proxima Centauri and its potentially Earth-like orbiting planet, Proxima b, in just 20 years, traveling at 20 percent the speed of light.

But a major drawback to Starshot’s plan is that, once the spacecraft arrived at Proxima b, it would fly past the planet in a matter of seconds. The so-called nanocraft would have just a brief window to return images and data to Earth, being propelled by the laser impacting a large 10-meter-square sail, but with no way to slow down.

Instead, this latest proposal published in The Astrophysical Journal Letters today – penned by René Heller from the Max Planck Institute for Solar System Research and IT specialist Michael Hippke, both in Germany – would place a spacecraft in orbit around Proxima b for a year or so. This would give it ample time to study a planet in the system, before returning to Earth.

“A flyby mission is only a few seconds,” Hippke told IFLScience. “So wouldn’t it be really cool if we could stop there?”

To do this, they envisage using photogravitational assists to speed up and slow down the spacecraft, taking a lot longer than Starshot’s plan – more than 100 years – but with a much greater scientific return.

A photogravitational assist would involve using the photons emitted from our Sun to speed up the spacecraft. Traveling at 4.6 percent the speed of light, it would take 95 years to reach two stars that form part of a triple system with Proxima Centauri, Alpha Centauri A and B. The photons from these stars, combined with their gravitational pull, would be used to slow down the spacecraft, and place it in orbit around Proxima b 46 years later.

How the mission would play out. Planetary Habitability Laboratory, University of Puerto Rico at Arecibo

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