Scientists are using X-rays to determine the hospitability of stars for life on exoplanets. Data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton were used to study 24 stars like our Sun that were at least one billion years old. They found these older stars had lower levels of X-rays — and hence magnetic activity — than other types of stars. This relatively calm is good news for life trying to form on planets around these stars. Astronomers will continue to look at different properties, including X-rays, to assess the best place to look for life outside our Solar System.