What is a quasar?

A quasar is a highly energetic and distant celestial object that emits enormous amounts of radiation.

Quasars, short for quasi-stellar radio sources, are among the most luminous and energetic objects in the universe. They are believed to be powered by supermassive black holes at the centers of galaxies, which accrete matter and release vast amounts of energy in the form of radiation and high-speed jets of particles. Quasars were first discovered in the 1960s as mysterious radio sources that appeared star-like in optical telescopes, but were found to emit intense radio waves and X-rays. They are located billions of light-years away from Earth and can be used as probes of the early universe, as their light carries information about the conditions and evolution of the cosmos at the time they were emitted. Quasars are also important for testing theories of gravity and cosmology, as they can reveal the large-scale distribution of matter and the geometry of space-time. However, their extreme distances and brightness make them difficult to observe and study in detail, and many questions about their properties and origins remain unanswered.