Space Telescopes and Starshades: Finding Earth-like Worlds

Going on a cosmic treasure hunt for planets similar to our own. NASA's New Worlds Observer (NWO) mission is an exciting step in this direction. This mission involves a 4-meter space telescope and a 50-meter starshade placed at a stable point between Earth and the Sun, known as L2. The goal? To detect and study habitable planets around nearby stars. First, let's understand what a starshade is. It's like a giant sunshade in space, designed to block out unwanted light from distant stars. This allows the telescope to see faint planets orbiting these stars. The NWO mission uses smart target selection methods based on previous detections to maximize efficiency. It also considers varying levels of cosmic dust, known as exozodiacal background, and the chances of finding Earth-like planets.Through both analytical calculations and simulated observations, the team found that even in the worst-case scenario, the NWO could detect and characterize at least one habitable Earth-like planet with a 95% probability. In fact, they expect to find around three such planets within the mission's lifetime. One of the interesting findings is the "sweet spot" for starshade design. A starshade with an effective diameter of about 50 meters, having 12 or 16 petals, and placed around 70, 000 to 100, 000 kilometers from the telescope, seems to be the most feasible and cost-effective option. This mission not only helps us find new worlds but also leaves time for exploring the universe in other wavelengths, like ultraviolet and near-infrared, during the same mission.