Birth and Evolution of the Solar System: From Ancient Gas Clouds to the Dance of Planets

 Approximately 5 billion years ago, the Sun emerged as a full-fledged star, converting hydrogen into helium in its core. It was enveloped by a disk of material, primarily hydrogen from the nebula it originated from, but also consisting of complex molecules. Within this disk, interactions led to the formation of icy, dusty grains that grew and interacted with each other. Gaseous portions of the disk might have separated as well. Consequently, planets arose from this tumultuous environment.

Which is the oldest planet in the solar system?

Jupiter, the first to form within the initial 3 million years of the Solar System, holds the title of the oldest planet. With a mass equivalent to 318 Earths, Jupiter is so immense that its barycenter with the Sun – the point around which it orbits – is not at the Sun's center, but just outside its surface. This means Jupiter doesn't orbit precisely around the Sun. Following Jupiter, Saturn began to develop, succeeded by Neptune and Uranus. By the time the latter two were forming, Jupiter and Saturn had already consumed much of the gas in the outer Solar System. While Jupiter has active moons like Europa, Io, and Ganymede, its moon Callisto possesses the oldest surface in the Solar System. Concurrently, four rocky planets and one dwarf planet were emerging in the inner Solar System, taking longer to form – around 100 million years – due to their reliance on collisions between rocky bodies. Estimating the ages of solid celestial bodies is typically done by counting surface craters, but this becomes more complex for bodies with changing surfaces.

Which is the youngest planet in the Solar System?

Determining the youngest planet is not as straightforward as identifying the oldest, which is Jupiter according to formation models. Among the youngest contenders are Earth and Uranus, both having experienced massive collisions. Roughly 4.5 billion years ago, the primordial Earth likely collided with Theia, a Mars-sized planetoid, resulting in the Moon's formation. The Moon solidified in about 200 million years, while Earth took longer to become what it is today, with ocean and tectonic plate formation occurring around 3.6 billion years ago. Between 3 and 4 billion years ago, Uranus collided with an Earth-sized object, disrupting its interior, tilting its axis, and generating an unusual magnetic field. Deciding which planet is the youngest ultimately depends on how we define "youngest." Moreover, the definition of a planet can be limiting and controversial, as exemplified by the debate surrounding Pluto.