Sometimes it takes a while for the meaning of a new scientific discovery to really sink in. In the case of the planet Proxima Centauri b, announced last week, it may take decades or even centuries to fully grasp the importance of what we have found. You see, this is not just any planet: It is similar to Earth in mass, and it orbits its star in the “habitable zone,” where temperatures could potentially allow the existence of Earthlike bodies of liquid water. Proxima Centauri is not just any star, either: It is the very nearest one after the Sun, and it is a small red orb whose feeble light makes it relatively easy to study the planet close beside it.The science at stake here is enormous. Proxima Centauri b will surely become the archetype for understanding more distant Earth-size, and possibly Earth-like, planets all across our galaxy. The effort needed to study it will be enormous, too, however. At present the planet cannot even be glimpsed directly through the mightiest telescopes on Earth. Nevertheless, the race is on–a thrilling but maddeningly slow-motion race to bring Proxima Centauri into view, to figure out if it could (or does!) support life, even to visit it with an interstellar probe.That last goal is the most ambitious; some might call it the most absurd. But the discovery of Proxima Centauri b comes at a propitious time, just as a group of physicists and engineers have been thinking very realistically about how to send a space probe to another star, and to do it within a single human lifetime. The resulting
concept would use an array of extremely high-power lasers to shoot a beam at a huge, extremely thin reflective sail. Energy from the beam would accelerate the sail (and a miniature probe attached to it) to 1/5 the speed of light, more than 1,000 times faster than anything humans have yet achieved.
of the University of California at Santa Barbara to develop a popular-level summary of how the Starshot would work. You can read about it
here. If you want to dig into the more technical details of the project, Lubin also has a much longer
posted online. This proposal envisions technology beyond what is available today, but there are no science-fiction elements in it. No warp drive, no wormholes. It is a straight extrapolation from things we know and do right now, just executed on a vastly greater scale-which is broadly similar to where the idea of going to the moon was around 1950.
In other words, we don’t know how to build a Starshot yet, but at least we know where to start. If we invested seriously in the project-on the order of $20 billion total, more than the Large Hadron Collider but far less than the International Space Station-and got started right away, Lubin and other researchers guesstimate that we could have the
ready in three decades. I’ll be more conservative and add another two decades to allow for all the full suite of components: In addition to the phased laser array you need the the energy-collecting sails, the probes themselves, and a “mothership” to carry them into orbit before interstellar launch. Just this week, a group of Starshot planners
met at Moffett Field
in California to hash out some of the details.Lubin suggests that the a laser-accelerated lightsail could reach 0.25c (that is, 25 percent the speed of light). The Breakthrough Starshot
announcementsimilarly suggests a target velocity of 0.2c. I’ll again be conservative–within this frame of crazy optimism, that is–and say that what is really possible is closer to 0.05c, or 5 percent the speed of light. That is still roughly 10,000 miles per second, a hugely ambitious goal. At that speed, sending probes to Proxima Centauri b would take approximately 85 years.Notice, by the way, that I said
probes. To make the Starshot work, you want to start with very small payloads, no larger than an iPhone and possibly a good deal smaller; the lighter the payload, the easier it is to accelerate to ultra-high velocity. A low-mass payload will necessarily have limited capabilities, probably a camera, a couple types of spectrometers, particle & magnetism detectors, and a laser communication system. When that probe reaches its destination, it will still be moving at 10,000 miles per second and will have no way to slow down. Your trip through the most interesting part of the Proxima Centauri system will happen very quickly, in a matter of hours, and you will have no way to steer toward planet b or any other specific targets.