Astronomers have discovered a planet estimated to be 10 billion years old, comparable to the age of the universe itself. The object rotates around one of the oldest stars in the Milky Way, located 280 light years from Earth.
The planet is 1.5 times larger than Earth, three times more massive and orbits the star TOI-561 with an orbital period of 10.5 hours. TOI-561 b’s surface temperature is estimated at 2,480 kelvin, with it always facing one side of the local sun. The discovery suggests that rocky planets can exist for a very long time while remaining stable.
The planet’s density is comparable to Earth, indicating that it is composed of light elements and consistent with its age. Heavy elements are formed in the bowels of stars and are ejected into space with their demise, including in supernova explosions. Therefore, the oldest stars have low metallicity, that is, they contain few elements heavier than hydrogen. Similarly, any ancient planets also cannot contain many heavy elements.
The existence of old planets also increases the chances of the development of complex life. On Earth, vertebrate animals appeared no earlier than 500 million years ago, although the age of the Earth reaches 4.5 billion years.