Free Astronomy Magazine September-October 2021

4 SEPTEMBER-OCTOBER 2021 ASTRO PUBLISHING More “Earths” but fewer complex biospheres by Michele Ferrara revised by Damian G. Allis NASA Solar System Ambassador I n recent months, several pub- lished studies have significantly expanded what we know about Earth-sized planets and their poten- tial capacity to host life as we know it. One of the biggest unknowns concerning Earth-like (but not nec- essarily habitable) planets is their number within the Milky Way. Cur- rent estimates are distributed over a very wide range that also varies de- pending on the type of the host star. T his illustration depicts a planet partially hidden in the glow of its host star and a nearby companion star. After examining a num- ber of binary stars, astronomers concluded that Earth-sized planets in many two-star systems may go unnoticed in transit research. The light from the second star makes it more difficult to detect changes in the host star’s light as the planet passes in front of it. [International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva (Spaceengine)]