Even though the Universe is mostly composed of a cold and dark void, there occasionally are celestial bodies scattered throughout this empty space. These can range from normal objects, such as planets, to bizarre phenomena, like black holes. Given how the Universe is such a wondrous and amazing place, we should all be compelled to know more about the different astronomical bodies that exist within it.
Planets: We all know what a planet is: a round and rigid celestial object that orbits a star. There are various types of planets:
- Terrestrial Planets: These planets are primarily made up of rocks and metals, making them solid. In our solar system, these include the Earth, Venus, Mercury, and Mars.
- Gas Giants: These planets are mainly made up of gas (helium & hydrogen), meaning that they aren’t solid. If you tried to stand on them, you would essentially sink down. In our solar system, these include Jupiter and Saturn.
- Dwarf Planets: These planets are basically terrestrial planets, but just extremely small. You probably remember poor Pluto being demoted to a dwarf planet since it’s smaller than the Moon.
Satellites: The Earth’s Moon is a satellite, a celestial object that orbits a bigger body, such as a planet. For the most part, satellites are much, much smaller than the bodies they orbit. An interesting example of a satellite is Titan, one of Saturn’s moons, because it is bigger than Mercury.
Stars: Stars are massive celestial objects that create light, heat, and energy from the nuclear fusion of hydrogen into helium in their cores. There are many types of stars, some of which are:
- Main Sequence Stars: These are stars that are at the most stable stage of their life (main sequence). Stars will spend most of their lives in this stage, constantly fusing hydrogen into helium. Our sun is a main sequence star.
- Red Giant: When a star runs out of hydrogen, it begins to fuse helium, causing the star’s surface to massively expand, cool, and turn red. At the same time, the outer layers begin to shed away into space.
- White Dwarf: Once all of the star’s layers have been shed and the core collapses on itself due to gravity, all that remains is the white dwarf. It essentially is the corpse of the star, and it’s also extremely dense.
- Red Dwarfs: Red dwarfs are the smallest and coolest stars that are on the main sequence. They burn their fuel so slowly that they might become the last stars to exist in the Universe. As such, they might become the final home of humanity.
Quasars: Even though quasars (picture of this article) are the brightest objects in the Universe, they aren’t some massive stars going supernova. Instead, quasars are the nuclei of galaxies in their infancy, and they are powered by supermassive black holes.
Black Holes: We have all heard of black holes: celestial objects whose gravity is so strong that not even light can escape it. The center of a black hole is called a singularity, where gravity and density are believed to be infinite. This also means that space and time extend into infinity here. Could you imagine how that would feel?
