The Solar System
It’s time for the human race to enter the solar system. ~ American politician Dan Quayle
Our solar system got its start less than 5 billion years ago. A shock wave from a supernova explosion created a debris cloud that collapsed to form the Sun and its satellites. The cloud also cradled the birth of hundreds of thousands of other star systems. By that time, among the trillions of star systems throughout the universe, many millions had already matured to have planets teeming with life.
Until the mid-1990s, cosmologists embraced the core-accretion theory: a standard model which explained star system formation using a few basic principles of physics and chemistry. The theory accounted for every major feature of the solar system, yet it turned out to be inapt.
From the mid-1990s, exoplanets in other star systems kept being found that were inexplicable, such as gas giants the size of Jupiter in close, tight orbits around their stars. The accumulation of such discoveries trashed the core-accretion theory. Space oddities continue to be found, leaving no coherent account of how planetary systems come into being.
One feature found in many systems is planetary migration. All sorts of planets grow to full size in the middle to outer part of a solar disc before moving inwards. This can sometimes cause other planets to shift their orbits outwards. Such shenanigans occurred during the development of our solar system.
Our star system itself is coursing the cosmos at 20 kilometers per second. The solar system makes a rotation around the Milky Way galactic disk every 230 million years.
