Jun 12, 2023 21:00:00

What is a `` quasar '' that is considered one of the brightest objects in the universe?

A '

quasar ' is a celestial body that exists in the center of the galaxy, blows out matter vigorously, and shines brightly with a power comparable to that of 1 trillion fixed stars. Kurzgesagt , a science YouTube channel, explains in animation about quasars, which sometimes have amazing power to destroy the galaxy.

The Black Hole That Kills Galaxies-YouTube


A quasar is a relatively small celestial body, but it basically exists in the center of the galaxy.

Quasars are also known to be the brightest and most powerful objects in existence, suggesting that they could completely remake the universe around them.

The discovery of such quasars began in the 1950s, when astronomers noticed that mysterious powerful radio waves were being emitted from various parts of the universe. The source of the radio waves was found to be a celestial body whose internal structure could not be confirmed with an astronomical telescope, and which could only be observed using a radio telescope.

This object was named a ``quasi-stellar radio source'' because the light source looked like a fixed star.

It is also called 'Quasar' as an abbreviation for 'quasi-stellar radio source'.

It is known that quasars include objects that blink, emit radio waves, and emit X-rays and visible light.

The quasar's spectrum has a strong

redshift , so it turned out to be a distant object that seems to move away from Earth at a tremendous speed of more than 30% of the speed of light as the universe expands.

Being billions of light-years away and appearing bright and large, quasars are believed to be thousands of times brighter than

the Milky Way galaxy .

Astronomers have so far discovered more than one million quasars, all of which have been found to be far from Earth.

Also, since many quasars are far away, it is estimated that they peaked in the early stages of the universe's formation, 3 billion years after the Big Bang.

A ``supermassive black hole'' is the reason why quasars are able to produce intensely bright energy in the early stages of the immature universe, three billion years after the Big Bang.

When the surrounding gas and dust are sucked into the supermassive black hole, which is thought to exist at the center of every galaxy, these gas and dust form a disk while rotating around the black hole. This disk is called the '

Acretion Disk'.

Matter sucked into the black hole moves at a speed close to the speed of light before it crosses

the event horizon, and is absorbed by the black hole with tremendous kinetic energy. It is believed that the energy released by matter sucked into a black hole is about 60 times the energy generated by nuclear fusion.

In the accretion disk, the temperature rises to several hundred thousand degrees Celsius or more due to friction between substances, and the substance turns into

plasma . As a result, various electromagnetic waves such as X-rays, visible light, and radio waves are emitted from the accretion disk with great force.

The central part of such an active galaxy is called an '

active galactic nucleus ', and quasars are considered to be one type of this active galactic nucleus.

In the early days of the universe, which is about one-third the size of the current universe, gas and dust collided more violently than they do today, generating strong frictional heat. Therefore, it is thought that many active quasars were formed.

Particularly active quasars are known to emit huge beams of matter called ``jets'' that grow to sizes of hundreds of thousands of light years.

But the violent jets overheat the gas needed for star formation, and star formation stops.

Not only that, but if the jet pushes gas out of the galaxy, not only the quasar but also the galaxy will starve and lose the raw material for new stars.

On the other hand, the gas is compressed by the shock waves and jets from the quasar, and it is possible to form new stars for a short period of time. Also, the gas pushed out by the jet is mixed with the gas entering the galaxy and recycled.

However, it is thought that once a quasar has fallen into a starvation state, it will disappear, leaving only a supermassive black hole.

Also, it has not been clarified whether quasars once existed in the Milky Way galaxy to which the earth belongs.

However, since

Sagittarius A* , which exists at the center of the galaxy, has grown to a mass four million times that of the Sun, it is suggested that there may once have been a quasar.

Billions of years from now, when the Milky Way and

Andromeda galaxies collide, it is possible that the central black holes will merge, forming even more supermassive black holes and giving birth to new quasars. I'm here.