quasar

American  

[kwey-zahr, -zer, -sahr, -ser] / ˈkweɪ zɑr, -zər, -sɑr, -sər /

noun

Astronomy.

1. one of over a thousand known extragalactic objects, starlike in appearance and having spectra with characteristically large redshifts, that are thought to be the most distant and most luminous objects in the universe.

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quasar British  

/ ˈkweɪzɑː, -sɑː /

noun

1. any of a class of extragalactic objects that emit an immense amount of energy in the form of light, infrared radiation, etc, from a compact source. They are extremely distant and their energy generation is thought to involve a supermassive black hole located in the centre of a galaxy

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quasar Scientific  

/ kwā′zär′ /

1. Short for quasi-stellar radio source. A compact, starlike celestial body with a power output greater than our entire galaxy. Believed to be the oldest and most distant objects ever detected, quasars are billions of light-years from Earth and moving away from us at nearly 80 percent of the speed of light. For this reason, quasars are highly important to astronomers' understanding of the early universe. Little is currently understood about the nature of quasars; one theory suggests that they are produced by giant black holes destroying enormous amounts of matter, causing the subsequent ejection of radiation along their north and south poles. Many astronomers believe that quasars represent an early stage in the evolution of galaxies such as our own.

2. See also blazar Seyfert galaxy

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Etymology

Origin of quasar

1960–65; quas(i-stell)ar, in quasi-stellar radio source, the first type of quasar discovered

Compare meaning

How does quasar compare to similar and commonly confused words? Explore the most common comparisons:

• quasar vs. pulsar

Explanation

A quasar is a starlike object in space that may emit energy, light, and radio waves. In the vastness of the universe, there are many bodies such as planets, moons, asteroids, and suns. Another type of object is the quasar. Quasars are a lot like suns, though much smaller. Quasars have large redshifts, which means the light from the quasar increases in frequency, moving to the red part of the light spectrum. Quasars are powerful and usually produce a lot of radiation. Don't mess with a quasar!

Example Sentences

The Milky Way itself may have once gone through a quasar phase, although it is not active today.

From Science Daily • Mar. 30, 2026

The quasar is pulling in matter at an exceptionally high rate while also emitting intense X-rays and launching a strong radio jet.

From Science Daily • Jan. 24, 2026

Instead, this quasar remains bright in X-rays and strongly radio-loud at the same time.

From Science Daily • Jan. 24, 2026

Although quasar activity peaked in the early Universe, quasars were rare and spread apart by hundreds of millions of light years.

From Space Scoop • Jul. 4, 2025

In that case, the more distant the galaxy, the earlier in its history we are observing it, and the more likely it is that we should see it as a quasar.

From "Cosmos" by Carl Sagan