In August 2o15, researchers discovered a potentially habitable, Earth-sized planet orbiting the Sun’s closest stellar neighbor — Proxima Centauri, a mere 4.22 light years away. To some, this challenge is an irresistible destination. Sending a spacecraft to the planet, dubbed Proxima b, would give humans their first view of a world outside the Solar System. “Clearly it would be a huge step forward for humanity –– if we could reach out to the nearest star system,” says Bruce Betts, director of science and technology for the Planetary Society in Pasadena, California. The data beamed back could reveal whether the alien world offers the right conditions for life — and maybe even whether anything inhabits it.
The idea of reaching Proxima b, however, is not just science fiction [see attached report]. In fact, a few months before the discovery of the exoplanet, a group of business leaders and scientists took the first steps toward “visiting the Alpha Centauri star system,” home to Proxima. They announced Breakthrough Starshot, an effort backed by US$100 million from Russian investor Yuri Milner to massively accelerate research and development of a space probe that could make the trip.
When Proxima b was found [Nature 2o16; 536: 437–440], the hypothetical project (described above) gained an even more tantalizing target. In 2015, Lubin had produced a conceptual road map for getting a spacecraft to Alpha Centauri in 20 years [J Br Interplanet Soc 2o16; 69, 40–72]. He suggested using an array of lasers on Earth to generate a beam powerful enough to propel a small light sail. The Starshot team plans to use conventional rockets to send its probes into orbit. Then a 100-gigawatt laser array on Earth would fire continuously at the sail for several minutes, long enough to accelerate it to 60,000 kilometers per second.
Starshot leaders acknowledge that they are counting on future breakthroughs from the laser industry. One hundred gigawatts will be a million times more powerful than today’s biggest continuous lasers –– which put out hundreds of kilowatts. One way around that gap would be to combine light from hundreds of millions of less powerful laser beams across an array that is at least a kilometer wide. But the beams would all need to be brought into phase with each other so that their light waves would add, rather than cancel, each other out — making the lasers one of the mission technologies that requires the most development work.
This story became more exciting and relevant (a few hours ago) when NASA reported the Spitzer Space Telescope has found the first known system of seven Earth-size plantets circling a single star. Three of these planets are highly likely located in the habitable zone –– the area around the parent star where a rocky planet is most likely to have liquid water. The discovery (easily) sets a new record for “greatest number of habitable-zone planets found around a single star outside our solar system.” All of these seven planets could have liquid water –– which is the key to life, as we know it –– and under the right atmospheric conditions, but the chances are highest with the three in the habitable zone.
At about 40 light-years (235 trillion miles) from Earth, the system of planets is “relatively close to us,” in the constellation Aquarius. Because they are located outside of our solar system, these planets are scientifically called “exoplanets.” This exoplanet system is called TRAPPIST-1, named for The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. In May 2o16, researchers using TRAPPIST announced they had discovered three planets in the system. Assisted by several ground-based telescopes, including the European Southern Observatory’s Very Large Telescope, Spitzer confirmed the existence of two of these planets and discovered five additional ones, increasing the number of known planets in the system to seven.
[Yes, I know: WHAT does this have to do with Gene-Environment Interactions. The answer is “Nothing, really. But doesn’t this sound cool?]
Nature 2 Feb 2o17; 542: 20–22