On January 27, 2015, researchers announced in the Astrophysical Journal that they had discovered a very old star with Earth-sized planets. These planets orbit the 11.2-billion-year-old star Kepler-444, which formed when the universe was approximately 20 percent younger than it is today. Scientists estimate that Kepler-444's five planets date back to the same time. This means that when our own solar system formed, the Kepler-444 system was already older than our planet is now.
Each of the five planets range in size from that of Mercury to that of Venus, which makes all of them slightly smaller than the Earth. They orbit the star at a distance that is one-tenth of the distance between the Earth and its Sun, which indicates that the planets' levels of radiation and temperature would make them uninhabitable. Nevertheless, the discovery is significant, as the size and age of these planets suggest that planets have been forming for the majority of the universe's lifetime.