Scientists Say: Quasar

This word describes the superbright center of some galaxies

a photo of a distant quasar taken by the Hubble telescope

The bright spots at the center of the photo are 14 billion light-years away. Scientists once thought they were two twin objects, but this is actually just one quasar. It appears twice in this image because of an effect called gravitational lensing that happens when gravity bends light.


Quasar (noun, “KWAY-sar”)

This word describes the distant and superbright center of some galaxies.

Galaxies, like our own Milky Way, are huge collections of stars. All known galaxies that are bigger than a certain size have supermassive black holes near their center. Supermassive black holes are the most massive of black holes. These objects have a powerful gravitational pull. Quasars can be found at the cores of galaxies where one of these giants is sloppily slurping up matter. As the supermassive black hole sucks in mass, gas and dust swirl around it. This matter moves so quickly that it gives off a lot of energy.

Some of this energy is given off as radio waves. That’s why these objects were first called “quasi-stellar radio sources,” or quasars for short. But quasars emit all types of radiation, including X-rays and visible light. A quasar’s light outshines all the other stars in its galaxy. In fact, quasars are some of the brightest objects known. They can be trillions of times brighter than the sun.

Most quasars that astronomers and others have found are billions of light-years away from Earth. Because quasars are so far way, people need telescopes to see them.

In a sentence

Inside a distant quasar, two black holes may smash together in about a million years.

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Carolyn Wilke is a former staff writer at Science News Explores. She has a Ph.D. in environmental engineering. Carolyn enjoys writing about chemistry, microbes and the environment. She also loves playing with her cat.

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