Free Astronomy Magazine March-April 2022

31 MARCH-APRIL 2022 ASTRO PUBLISHING cal units away from the Sun (82 billion km or 51 billion mi). If we consider that the Voyager 1 probe, launched in 1977, has moved away by just over 155 a s t r o n o m i c a l units, the idea of Friedman and col- leagues appears rather utopian, even despite the advances accumu- lated by astronautics in the last 45 years. However, this same team pro- posed a solution to shorten the time needed to reach the focal line. The solution consists of using a probe equipped with a large solar sail, a technology that recently has been successfully tested in Earth orbit with LightSail 2. The principle of solar sailing finds the sail propelled (therefore accelerated) by the pres- sure of solar radiation. The larger the sail and the lighter the load car- ried, the higher the achievable ve- locity. The team calculated that a focusing device weighing about 100 kg (220 lb) could arrive at its desti- nation in about a quarter of a cen- tury, which is acceptable given the impressive prospects. We cannot predict what from all this possibility will be achieved in the coming decades and what will remain only theory. What is certain is that Prox- ima b will remain a primary target for many research teams, at least until it is certain (and not just prob- able) that it is an inhospitable planet for life as we know it. ! difference from traditional imaging at the distance of that system, it’s enough to say that the largest ground-based telescopes can re- solve details no smaller than two million kilometers wide, or about 150 times the size of the Earth. At that scale, the image of no exo- planet could occupy more than one single pixel. If, on the other hand, we could use the Sun as if it were the objective of a telescope, we could obtain a resolution of a few kilometers on Proxima b, which would mean mapping the surface in amazing detail. Beyond all the technical difficulties that such an undertaking would bring, the most relevant problem is reaching the focal line of the “lens,” which begins about 550 astronomi- T hese images taken by the Planetary Society’s LightSail 2 spacecraft show the Red Sea, the Nile River, the Eastern Mediterranean Sea with surrounding areas (below), and northern Brazil (right). The LightSail 2 mission demonstrated that it is possible to accelerate a spacecraft by simply using the pressure of solar radiation, a type of propulsion that could be exploited to reach distant destinations in a few decades, such as the focal line of the solar gravitational lens or the nearest exoplanets. [The Planetary Society]