General, Research, Technology

Why are most dwarf galaxies dead?

Looking at photos of distant galaxies obtainedWith the Hubble Space Telescope, we don’t often think about how these links of the space web are born, live and die. In 1929, when Edwin Hubble radically changed our understanding of the Universe, no one could have imagined that humanity would discover 100 billion galaxies! The astronomer also proved that our Universe is expanding with acceleration and compiled the first detailed system for classifying galaxies by shape. Needless to say, this system is the basis of modern classification. Space is a truly crazy place in which countless stars and galaxies are born and die, and this process is interconnected: when new stars cease to be born in a galaxy, scientists classify it as dead. But why are most dead galaxies dwarf?

Dwarf galaxies - another mystery of the universe

Dwarf galaxies - what you need to know?

Before Edwin Hubble proved that oursthe galaxy is just a grain of sand in the vast ocean of space, the researchers believed that our galaxy is the whole Universe. Moreover, Albert Einstein created the general theory of relativity (GR) based on the fact that only our galaxy exists. The discovery shocked him and subsequently he called Edwin Hubble the giant of astronomy. Agree, absolutely deserved. So, Hubble has identified three main types of galaxies: spiral, elliptical and irregular. Spiral galaxies, as we know today, are more common than others. But what about their size?

A dwarf galaxy is considered a dwarf, the number of stars in which is tens and hundreds of timessmaller than in the Milky Way galaxy. Due to the low luminosity, a detailed study of dwarf galaxies is possible only at relatively close distances. There is no clear difference between ordinary and dwarf galaxies.

Researchers note that dwarf galaxiesoften are satellites of larger, brighter galaxies. The smallest dwarf galaxies have mass, compared with a million solar masses. The closest satellite to our galaxy is the dwarf galaxy Small Magellanic Cloud. It is believed that dwarf galaxies originated as independent galaxies billions of years ago, however, younger ones are also found in space. Scientists believe that dwarf galaxies should have played a large role in the formation of huge galaxies.

Pictured by astronomer Edwin Hubble. The Man Who Changed Our Perception of the Universe

It is also important that, like ordinarygalaxies, dwarf stars contain stars of different ages - just like in ordinary galaxies; however, stars in dwarf galaxies, as a rule, are distinguished by a very low content of chemical elements heavier than helium. Moreover, interstellar gas and dark matter are also present in tiny galaxies. Nevertheless, not so long ago, scientists discovered as many as 19 dwarf galaxies without dark matter. How is this possible and what does it mean for modern science, read in our material.

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Dead galaxies

As you know, a galaxy is considered dead if init no longer forms new stars. But how are they born? To begin with, gas is present in any galaxy. As it cools, it contracts and gradually turns into stars. Of course, this is a very simplified explanation. The force of gravity literally draws gas into the galactic disk, and supernova explosions push it out. It turns out that galaxies seem to “breathe” gas, inhaling and exhaling it. It is thanks to these processes that galaxies exist and new stars are born.

According to a new study,it is very difficult for dwarf galaxies to restore the star formation process, since most of the stars in them are very ancient. Moreover, existing stars in such galaxies struggle with the birth of any new stars, even after the galactIku gets fresh fuel for star formation - gas.

So looking galaxies in the lens of the legendary Hubble Space Telescope

This is interesting: How many galaxies are there in the Local Group and what does this say about the Milky Way?

However, a computer simulation developed byThe authors of the study showed that ultimately new stars in dwarf galaxies can arise and even give the galaxy brightness. It just takes billions of years. The work can be found on the preprint server.

The authors of the work write that in order tocollapse into stars, the gas must be cold and dense. This requirement creates problems for small galaxies, which appeared shortly after the Big Bang, when the ultraviolet radiation of galaxies divided the intergalactic hydrogen atoms into protons and electrons. Scientists call this process “reionization” - it allows radiation to pass through space and heat the gas inside the galaxies. The problem is that initially there was little gas in dwarf galaxies, and reionization completely killed star formation. Thus, the researchers write, all the stars in most dwarf and not massive galaxies are ancient. True, not without exceptions.

Galaxies Big and Small Magellanic clouds - satellites of the Milky Way

Read even more fascinating articles about space and distant worlds on which intelligent life can exist on the pages of our magazine in Yandex.Zen. It publishes articles that are not on the site.

So, two unrelated dwarf galaxies inLeo constellations, called Leo P and Leo T, still form new stars. To explain why these small galaxies flourish, the authors of the study resorted to computer modeling of gas, stars, and dark matter in low-mass dwarf galaxies. The results showed that infusion gas can “revive” dwarf galaxies and trigger the star formation process. It just happens very slowly.

Another interesting finding of a new studyis the fact that now researchers can predict the existence of a new class of galaxies. Modeling shows that some dwarf galaxies have already accumulated gas, but the star formation process has not yet begun. One way or another, further research should clarify the reasons why this happens. I hope that from this article you learned something new and truly amazing about the world in which we live.