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The secret of dwarf galaxies: How were these small galaxies born in the early universe?
In the universe, dwarf galaxies have always attracted the attention of astronomers with their uniqueness. These galaxies, which are smaller than the Milky Way and contain thousands to billions of stars, are known to hold important keys to understanding the formation and evolution of the universe. Against this backdrop, scientists have been able to gain insight into the origins of dwarf galaxies, especially how they formed in the early universe.
What is a dwarf galaxy?
Dwarf galaxies are relatively small galaxies that are dwarfed by the size of our Milky Way, which has 20 to 400 billion stars. For example, the Large Magellanic Cloud is classified by some astronomers as a dwarf galaxy, even though it contains more than 30 billion stars. The formation and activity of dwarf galaxies are often strongly influenced by interactions with larger galaxies, a fact that is increasingly being recognized in astronomical research.
Theory of formation of dwarf galaxies
There are currently several theories to explain the formation of dwarf galaxies. One popular view is that most galaxies, including dwarf galaxies, are formed together with dark matter. Dwarf galaxies may also be made of gas with low metallicity, astronomers have found, using NASA's Galaxy Evolution Explorer (GEO). In the Leo Ring, a cloud of hydrogen and helium, scientists have observed the formation of new dwarf galaxies.
Due to their tiny size, dwarf galaxies are often pulled and torn apart by neighboring spiral galaxies, which leads to star streams and eventual galactic mergers.
In the Local Group of galaxies, many dwarf galaxies orbit larger galaxies such as the Milky Way, Andromeda, and Triangulum. A 2007 study showed that many dwarf galaxies were formed by gravitational tidal effects during the early evolution of the Milky Way and Andromeda galaxies.
Diversity of Local Dwarf Galaxies
In our universe, especially in the Local Group region, astronomers have identified several types of dwarf galaxies. Among them are spherical galaxies, dwarf elliptical galaxies and irregular galaxies, each of which has its own unique shapes and compositions. Some dwarf galaxies, such as the Blue Chiron Galaxy (BCD), have a large number of young and hot stars, which makes them appear blue. These galaxies form at a rapid rate, causing their stars to produce energy relatively vigorously.
The Mystery of Faint Dwarf Galaxies
Faint dwarf galaxies (UFDs) are another type of galaxy that contain between a few hundred and a hundred thousand stars, making them extremely faint and difficult to detect in the universe. These galaxies are similar to globular galaxies, but contain large amounts of dark matter and have a more extended structure. Scientists first discovered these faint galaxies following the advent of digital sky surveys in 2005, and their appearance provides a rich source of data for studying the early universe.
Scientists believe that faint dwarf galaxies contain important information about the early universe because all UFDs discovered so far are ancient systems that probably formed within a few million years after the Big Bang.
Characteristics of hypertropic galaxies
Ultra-dense galaxies (UCDs) are a group of relatively compact galaxies that contain a high density of stars. These galaxies are about 200 light-years in diameter and typically contain about 100 million stars. Astronomers speculate that such galaxies are the cores of nucleated dwarf elliptical galaxies, which lost gas and outer stars during tidal interactions, leading to their formation.
Based on analyzing the dynamical and structural properties of the locations where ultracluster galaxies are located, scientists have identified about 100 UCDs and found that they have properties that are completely different from normal spherical galaxies. In particular, M60-UCD1, discovered in the Virgo galaxy cluster, is about 54 million light-years away from the Earth. The star density in its core region is 25 times that of the Earth's galaxy.
ConclusionThe formation process of dwarf galaxies and their unique properties have undoubtedly given astronomers a deeper understanding of the evolution and structure of the universe. These small galaxies are not only the "remnants" of the universe, but also valuable resources for future research. In the future, as observation technology develops further, will we be able to unravel more mysteries about dwarf galaxies and allow them to reveal the secrets of the early universe to us more clearly?
