* Stars: Stars are the primary source of visible energy in the universe. They emit light and other forms of electromagnetic radiation due to the nuclear fusion reactions occurring in their cores.
* Galaxies: Galaxies are vast collections of stars, gas, and dust. The combined light from stars within a galaxy contributes to its visible energy output.
* Nebulae: Nebulae are interstellar clouds of gas and dust where star formation occurs. They often emit visible light due to the ionization of gas by nearby stars.
* Supernovae: Supernovae are powerful explosions that occur when massive stars reach the end of their lives. They release enormous amounts of visible energy in the form of light and radiation.
Invisible matter in the universe:
* Dark matter: Dark matter is a mysterious substance that does not emit or reflect light, making it invisible. It is believed to constitute a significant portion of the universe's total mass, but its exact nature remains unknown.
* Black holes: Black holes are regions of spacetime with extremely strong gravitational forces. They are invisible because any light or matter that enters their event horizon cannot escape.
* Neutrinos: Neutrinos are subatomic particles that are very difficult to detect due to their extremely weak interactions with other matter. They are produced in various processes in the universe, including nuclear reactions in stars and supernovae.