What Is A Quasar?

A quasar is a supermassive black hole in the heart of a distant galaxy that feeds on gas.

Quasar is an abbreviation for quasi-stellar radio source, which astronomers discovered in 1963 as objects that looked like stars but emitted radio waves. Now, the phrase refers to all feeding and hence bright supermassive black holes, also known as active galactic nuclei.

It's a bit of a stretch to call a black hole brilliant; black holes are, after all, black. In reality, practically every massive galaxy has a black hole with a mass ranging from millions to billions of Suns, and many of these black holes are hidden from view. The monster of our Milky Way galaxy weights 4.3 million solar masses, but its famine diet muffles anything except tiny flashes and flickers. The orbits of stars surrounding it, though, tell us it's there. Other dormant black holes will occasionally shred an infalling star, revealing their presence with a flash of radiation.

However, quasars are a unique type of black hole. They live in galaxies with abundant gas supplies, maybe from a recent galaxy-galaxy collision, and feast on the inflowing material. As it falls in, the gas spirals about, heating up and producing radiation over the electromagnetic spectrum.

Read More — Scientists showed how the earliest quasars formed

Because supermassive black holes in neighboring galaxies often do not have as much gas as quasars, they are typically found in distant galaxies. Markarian 231, located around 600 million light-years from Earth, is the closest quasar.

WHAT DOES A QUASAR LOOK LIKE?

A quasar is the light-producing structures that surround the feeding black hole as well as the black hole itself. The incandescent disk of infalling material emits visible and ultraviolet light, while hotter gas above the disk emits X-ray energy. Jets emitted by the black hole's poles range in frequency from radio waves to X-rays. The abundant dust and gas further away from the black hole shine at infrared wavelengths.

Read More — How are quasars formed?

A quasar accretion disk is generally a few light-days broad and scales with the mass of the black hole. That pales in contrast to its home galaxy, which is around 100,000 light-years across. However, quasars frequently outshine their hosts.

Despite their brightness, quasars are so tiny and far away that even the most powerful telescope cannot discern all of their structures. Astronomers must sift through the details using other methods, such as spectroscopy (spreading out the light by wavelength) or light curve analysis (spreading out the light by its arrival time).

While the specifics are still being debated, we may utilize existing information to construct a broad image of a quasar. Just keep in mind that as we learn more, this picture may alter!