06/12/2021
Our solar system consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids. Beyond our solar system, there are more planets than stars in the night sky. So far, we have discovered thousands of planetary systems orbiting other stars in the Milky Way, with more planets being found. Most of the hundreds of billions of stars in our galaxy are thought to have planets of their own, and the Milky Way is but one of perhaps 100 billion galaxies in the universe.
This makes us wonder about how was the solar system discovered? how did it come to be? and what is its structure?
For millennia, astronomers have followed points of light that seemed to move among the stars. The ancient Greeks named them planets, meaning "wanderers." Mercury, Venus, Mars, Jupiter, and Saturn were known in antiquity, and the invention of the telescope added the Asteroid Belt, Uranus, Neptune, Pluto, and many of these worlds' moons. The dawn of the space age saw dozens of probes launched to explore our system, an adventure that continues today.
Five human-made objects so far, Voyager 1, Voyager 2, New Horizons, Pioneer 10, and Pioneer 11, have crossed the threshold into interstellar space.
Our solar system formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova. When this dust cloud collapsed, it formed a solar nebula – a spinning, swirling disk of material. Most of the material was pulled toward the center to form the sun. Other particles within the disk collided and stuck together to form asteroid-sized objects named planetesimals, some of which combined to become the asteroids, comets, moons, and planets.
Finally, our planet is in some ways a mere speck in the vast cosmos, we have a lot of company out there. It seems that we live in a universe packed with planets – a web of countless stars accompanied by families of objects, perhaps some with a life of their own. So, let’s discover it!