Kepler-444, the oldest known planets
Five rocky worlds form 11.2 billion years ago, when the galaxy was barely a fifth its present age.
- When
- Known to
- ± 1 billion years
- Era
- Galaxy Assembly, Stelliferous
Kepler-444 hosts five planets smaller than Earth, all orbiting closer than Mercury does the Sun. Asteroseismology — reading the star's internal sound waves — dates the system to 11.2 billion years, making it the oldest known system of Earth-sized planets. It shows that rocky worlds were being assembled when the universe had only a fraction of today's heavy elements, and pushes the possible beginning of planets, and perhaps of life, far earlier than expected.