Astronomers have found that there are many dead galaxies in the Universe. Among the reasons for their death are “gluttony” and
Are there many dead galaxies or is this not a frequent occurrence?
Those galaxies in which stars have ceased to form are called dead. They have existed since the inception of the universe.
In one of the large-scale studies about the deadgalaxies, scientists from the Niels Bohr Institute found that almost 50% of all the largest galaxies in the Universe stopped producing new stars 9 billion years ago. This means that they can be considered dead.
How are dead galaxies formed?
To understand this, consider the galaxyMilky Way. At its center, presumably, there is a supermassive black hole: it is responsible for all the movements inside. Scientists believed that as soon as a black hole begins to become more active, it ejects cold dust and hydrogen clouds, as a result of which the galaxy is destroyed and the star formation process stops.
Next, gas clouds from the black hole envelop the galaxies and prevent gas flows from penetrating inside. The result is a cloud-buried galaxy that produces no stars.
There was another opinion.Some astronomers believed that dead galaxies are formed due to collisions with each other. After such a sharp contact, an explosion of star formation occurs and the entire supply of hydrogen gas, with the help of which new stars appear, is reduced to zero.
To understand the true reasons, scientiststook pictures of the central part of the oldest galaxy MACS2129−1. At first glance, it is no different from the others: it has stopped forming stars and has a red tint - this is the characteristic color of red dwarfs, which have almost run out of material for internal thermonuclear reactions.
Next, the authors paid attention to the spectrumgalaxies and found out that it was not spherical, but flat, somewhat reminiscent of the Milky Way. This means that the galaxy “died” at the dawn of its development.
According to astronomers, this death occurred due todark matter: it accelerated and warmed up ordinary matter, from which new stars are formed in the galaxy. Therefore, the material for star formation quickly ran out and all activity ceased.
Death from "gluttony". How does the new theory of the death of galaxies work?
Different galaxies produce stars at different rates. To create one star, you need a special gas, which is in limited quantities.
Astrophysicists have discovered the galaxy cluster CL J1001+0220, which is located in the early universe. It produces so many stars every year that its mass is 4 thousand times heavier than the Sun.
This is a record number. Such a rate of star formation will lead to the fact that gas reserves will run out and there will be nothing to create stars from. This phenomenon was jokingly called “death from gluttony.”
How are scientists discovering dead galaxies?
At the end of September 2021, astronomers usingHubble discovered six dead galaxies. According to the authors of the work, they stopped producing stars at a time when the universe was most actively creating stars.
At first, astronomers used Hubble toto find the exact location of the galaxies, after which they used the ALMA radio telescope complex to understand if the galaxies contain the same cold dust that we talked about above.
But despite their knowledge, scientists could notdiscover new similar objects, if not for a large cluster of galaxies: it works like a lens and helps to explore the distant regions of the Universe much more clearly.
Astronomers have published pictures of dead galaxies.The images show a yellow light - it came from starlight. There is also violet light - this is cold dust: it appears instead of hydrogen gas, which is responsible for the appearance of stars.
The death of a galaxy depends on its typestar formation, but this event can also happen completely unexpectedly, for example, due to the activity of dark matter. Astronomers have not yet studied all the causes of galactic death, but today there are enough tools to identify such objects and understand the causes of death.
Now scientists are engaged in classifying the causes of death of galaxies and highlighting the most likely and popular among them.
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