What is the oldest planet in the solar system?

With the age of the universe pegged at 13.8 billion years, this is the oldest star with close-to-Earth-size planets ever found. By comparison, our solar system is 4.5 billion years old. The five planets are smaller than Earth, with the largest about the size of Venus and the smallest just bigger than Mercury. read more

"Jupiter is the oldest planet of the solar system, and its solid core formed well before the solar nebula gas dissipated, consistent with the core accretion model for giant planet formation." Jupiter is the most massive planet of the solar system and its presence had an immense effect on the dynamics of the solar accretion disk. read more

Long before our Sun and Earth ever existed, a Jupiter-sized planet formed around a sun-like star. Now, almost 13 billion years later, NASA's Hubble Space Telescope has precisely measured the mass of this farthest and oldest known planet. The ancient planet has had a remarkable history, because it has wound up in an unlikely, rough neighborhood. read more

There is still work to be done to confirm, without a doubt, that Jupiter is the oldest planet in the solar system. That said, many have long suspected that the Jovian beast formed first, and the new findings present a convincing argument that this the case. Jupiter is still a jerk, though. read more