The bright lights could just draw you in NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

Of all the stars in the sky, you might assume the closest to the sun would be the easiest to visit. But this may not be the case.

René Heller at the Max Planck Institute for Solar System Research in Göttingen, Germany, says we could reach and orbit Sirius, the brightest star in our night sky, in just 69 years. This is despite the fact that it is twice as far away as our nearest stars in the Alpha Centauri system, which would take at least 90 years to reach.

A private enterprise called Breakthrough Starshot is hoping to send a fleet of small, wafer-thin spacecraft to visit Alpha Centauri and explore its tantalising planets. Previous estimates by Breakthrough Starshot have indicated they could reach Alpha Centauri in just 20 years, travelling at a fifth of the speed of light. But this estimate was calculated for a flyby mission, passing by in just a few seconds.


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That’s not much use if you actually want to observe anything when you’re there: the spacecraft would need to slow down. Earlier this year, Heller and independent researcher Michael Hippke showed how light from the stars themselves could be used to slow down a solar-sail powered spacecraft.

That technique might put Alpha Centauri at a disadvantage. Such a mission to put the spacecraft in orbit there around the star Proxima Centauri, for example, would take around 140 years, Heller has calculated.

Sirius is 8 light years away, twice as far as Alpha Centauri, but 16 times as bright, so its light would help the spacecraft both speed up and then decelerate.

Simple maths

The results surprised Heller at first, but the maths is simple, he says.

The time it takes to travel to the star system and then stay there is a function of the distance divided by the square root of the luminosity, so it would take less time to travel to Sirius compared to Alpha Centauri.

The idea is “innovative and interesting”, says Avi Loeb at Harvard University. “However, the concept requires an extremely thin sail if the goal is to reach a fraction of the speed of light.”

Heller and Hippke say the key to cracking this issue lies in material science.

“We need a very light, solid, temperature-resistant, and highly reflective sail material that can span an area of several hundred metres squared,” says Heller.

The material could possibly be based on graphene with a metamaterial coating, he says. “If this works out, then humanity can really go interstellar.”

Journal reference: https://arxiv.org/abs/1704.03871