Planet Earth
The third planet from the Sun, featuring liquid water, a protective magnetic field, and a stable atmosphere — making it the only known world capable of sustaining complex life.
Solar System
A gravitationally bound system containing the Sun, eight planets, dwarf planets, over 200 moons, asteroid belts, the Kuiper Belt, and the distant Oort Cloud which forms its outer boundary.
Orion Arm
A minor spiral arm of the Milky Way, about 3,500 light-years wide. Our Solar System lies inside the Local Interstellar Cloud, a star-forming region within this arm.
Milky Way Galaxy
A barred spiral galaxy roughly 100,000 light-years across, containing 200–400 billion stars, nebulae, star clusters, and a supermassive black hole called Sagittarius A* at its center.
Local Group
A gravitationally bound galaxy group containing around 80 members, including the Milky Way, Andromeda, and Triangulum galaxies. It spans roughly 10 million light-years.
Virgo Supercluster
A massive collection of galaxy clusters. The Local Group lies on its outskirts, while the Virgo Cluster — containing over 1,300 galaxies — forms its dense central region.
Laniakea Supercluster
An enormous cosmic structure spanning about 520 million light-years and containing over 100,000 galaxies, all flowing gravitationally toward a region known as the Great Attractor.
Observable Universe
The region of the cosmos from which light has reached Earth since the Big Bang — about 93 billion light-years across and containing roughly 2 trillion galaxies.
Cosmic Web
The large-scale structure of the universe — a vast interconnected network of galaxy filaments, clusters, and enormous empty voids shaped by dark matter and dark energy.
Universe
The totality of all space, time, energy, and matter, including the observable regions and the unknown expanses beyond our cosmic horizon.
Multiverse
A speculative concept proposing that our universe may be one of countless others — each potentially with different physical laws, dimensions, or origins.