We’ll start by exploring our own backyard, the solar system, and move on from there, says Loeb, who heads the Starshot advisory committee. After all, he notes, the tiny probes “can reach Pluto in three days, rather than the 9.5 years it took New Horizons to get there.” The program could sacrifice some of the multiple probes, he says, sending them “very close to targets we’re interested in. For example, we could fly through the plumes [of Enceladus] and see if we could detect the fingerprints of life.” The probes could also fly through the rings of Saturn or other harsh environments.
“With cheap, fast spacecraft,” says Guillochon, “we could send one out to every asteroid in the asteroid belt or to every Pluto-like object in the outer solar system. With these small craft ready to launch, we could have hundreds of missions, each of them to a brand-new, never-before-seen world.” Speaking of new worlds, he says, “If Planet Nine exists, this would be one way to get there quickly.”
There is no timetable set for missions like this, but if all goes according to plan, after 20 years of practice within the solar system, scientists may finally be ready for the first extra-solar target, the Alpha Centauri system. It has three separate stars to survey. Proxima Centauri is the nearest, and the other two, Alpha Centauri A and B, are similar to our sun in mass and luminosity.
What might a space probe see when it gets there? Proxima’s planet, dubbed Proxima b, is an obvious target. The rocky world of roughly Earth’s mass is in a tight orbit around its dim star, located in its “habitable zone.” Liquid water, and thus possibly life, might exist on its surface. There’s also an unconfirmed planetary sighting near Alpha Centauri B.
University of Colorado astrophysicist Webster Cash, meanwhile, is trying out an innovative technique to see such planets directly. Cash, who participated in a Starshot workshop in April, is reflecting light from a telescope on Arizona’s Kitt Peak to a smaller, secondary telescope 1.5 miles away. In between, he’s placed a screen called a starshade to block the light of a test star to detect dimmer planets orbiting it.