Astrophysics is the branch of astronomy that deals with the physical properties and behavior of celestial objects and phenomena.

Cosmology is the branch of physics that deals with the origin and evolution of the universe.

The Big Bang Theory is the prevailing cosmological model for the universe from the earliest known periods through its present expansion and cooling.

The cosmic microwave background (CMB) is electromagnetic radiation that is a remnant of the early universe.

Dark energy is a hypothetical form of energy that is believed to be responsible for the observed acceleration of the universe's expansion.

A supercluster is a large group of galaxies that are gravitationally bound together.

A star cluster is a group of stars that are gravitationally bound together.

Star formation is the process by which stars are born.

Star death is the process by which stars die.

A white dwarf is the remnant left behind after a star dies.

A neutron star is the remnant left behind after a massive star dies.

A black hole is the remnant left behind after a very massive star dies.

Galaxy formation and evolution is the theory that describes the formation and evolution of galaxies.

Galaxy structure and dynamics is the theory that describes the structure and dynamics of galaxies.

Galaxy interactions is the theory that describes the interactions between galaxies.