Looking at pictures of distant galaxies obtained by the Hubble space telescope, we don’t so often think about how beings are born, live and die, these parts of the cosmic web. In 1929, when Edwin Hubble radically changed our view of the Universe, no one can’t imagine that mankind will discover a 100 billion galaxies! The astronomer proved that the universe expands with acceleration and was first detailed system of classification of galaxies by shape. Needless to say that this system is the basis of modern classification. Space is a really crazy place, which is born and dies countless number of stars and galaxies, and this process is interconnected: when in the galaxy cease to be born new stars, scientists klassificeret her dead. But why most of the dwarf galaxies dead?
Dwarf galaxies – what you need to know?
Before Edwin Hubble proved that our galaxy is a speck in the vast cosmic ocean, researchers believed that our galaxy is the whole universe. Moreover, albert Einstein created the General theory of relativity (gr) based on the fact that there was only our galaxy. The discovery shocked him, and he subsequently called Edwin Hubble giant of astronomy. You will agree, completely deserved. So, Hubble has identified three main types of galaxies: spiral, elliptical and irregular. Spiral galaxies as we know today, occur most frequently. But what about their size?
Considered a dwarf galaxy with low luminosity, the number of stars in which tens and hundreds times less than in the milky Way galaxy. Due to the low luminosity of a detailed study of dwarf galaxies is only possible for relatively close distances. A clear difference between normal and kirlikovali galaxies does not exist.
The researchers note that dwarf galaxies are often satellites of larger, more luminous galaxies. The smallest dwarf galaxies have masses sravnival with a million solar masses. The nearest satellite of our galaxy, the dwarf galaxy called the Small Magellanic Cloud. It is believed that dwarf galaxies has emerged as an independent galaxy billions of years ago, however in space there are more young. Scientists believe that dwarf galaxies should play a greater role in the formation of huge galaxies.
Also important is the fact that like normal galaxies, dwarf contains stars of different ages – just like in normal galaxies; however, the stars in the dwarf galaxies usually have very low contents of chemical elements heavier than helium. Moreover, tiny galaxies also present interstellar gas and dark matter. However not so long ago scientists have discovered as many as 19 dwarf galaxies without dark matter. How this is possible and what it means for modern science read our material.
As you know, the galaxy is considered dead if it no longer forms new stars. But how are they born? Let’s start with the fact that in any galaxy there is a gas. Cools, it shrinks and gradually turns into a star. Of course, this is a very simplistic explanation. The force of gravity literally pulls the gas inside the galactic disk and the supernova explosions push it out. It turns out the galaxy is like a breathing gas, breathing in and out of it. It is through these processes there are galaxies and new stars are born.
According to the results of a new study of dwarf galaxies very difficult to reconstruct the process of star formation, since most stars in them are very old. Moreover, the existing stars in these galaxies are struggling with the birth of any new stars, even after galaktIK gets the fresh fuel for star formation – gas.
However, a computer simulation developed by the authors of the study showed that eventually the new stars in the dwarf galaxies can arise even give the galaxy brightness. It will just take billions of years. Work can be found on the Preprint server arXiv.org.
The authors write that in order to collapse into stars, the gas must be cold and dense. This requirement creates problems for small galaxies, which appeared soon after the Big Bang, when ultraviolet radiation of galaxies divided intergalactic hydrogen atoms into protons and electrons. Scientists call this process “reionization” – it allows the radiation to pass through space and heat the gas inside galaxies. The problem is that in dwarf galaxies was originally a little gas, and reionizatsii and completely killed the star formation process. Thus, the researchers write, all the stars in the majority and not the dwarf galaxies are ancient. However, not without exceptions.
So, two unrelated dwarf galaxy in the constellation Leo, named Leo T and Leo P, still forming new stars. To explain why these small galaxies are flourishing, the study authors resorted to computer modeling of gas, stars and dark matter in dwarf galaxies with low mass. The results showed that infusion gas can “revive” dwarf galaxies and start the process of star formation. Just everything is very slow.