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How big are elliptical galaxies? They can reach up to 700,000 light-years!
Elliptical galaxies are a type of galaxy with an elliptical shape and almost smooth surface features. According to Edwin Hubble's 1936 book "The Realm of Nebulae", elliptical galaxies, spiral galaxies and lenticular galaxies together constitute the three main categories of galaxies. These elliptical galaxies are typically composed of old, low-mass stars with a sparse interstellar medium surrounding large globular star clusters. These galaxies generally have less star formation activity, but brief star formation events may occur when merging with other galaxies.
"Elliptical galaxies are generally thought to occupy 10-15% of the Virgo Supercluster."
These galaxies range in size from small dwarf elliptical galaxies (with tens of millions of stars) to super-giant galaxies (with more than 100 billion stars), giving them a dominant position among galaxy clusters. Edwin Hubble initially believed that elliptical galaxies would evolve into spiral galaxies, but this assumption was later found to be incorrect. Although the accretion of some gas and small galaxies may form a disk around an elliptical structure.
Characteristics of elliptical galaxies
Elliptical galaxies are characterized by their random motion and lack of obvious shape structure. The stars in these galaxies are much older than those in younger spiral galaxies and are predominantly dark red in color. Statistics show that there is a supermassive black hole at the center of every large elliptical galaxy, and the mass of these black holes is highly correlated with the mass of the galaxy.
"Observation results show that the dynamic properties of elliptical galaxies and disk galaxies are similar, which may indicate that they are formed by the same physical process."
These galaxies are more common in galaxy clusters and compact assemblages of galaxies, while the structures and formation processes of the different types of elliptical galaxies remain controversial. Most elliptical galaxies lack gas and dust, so their star formation rates are low and they are generally dominated by old star populations.
Size and type
Elliptical galaxies vary greatly in size, ranging from 3,000 light-years to more than 700,000 light-years in diameter, a range unmatched by other galaxy types. Some dwarf elliptical galaxies are even close in size to globular star clusters, but contain considerable amounts of dark matter. The Hubble classification system for elliptical galaxies uses a numerical value to describe the extent of the galaxy's image, which is determined by the ratio of the major and minor axes of the galaxy's brightness profile.
"For a spherical galaxy, the long axis and the short axis are equal, then the value is 0, and the Hubble type is E0."
The difference is that one needs to consider how the viewing angle affects the true structure of these galaxies. Some galaxies classified as type E0 may actually exhibit elongated shapes. Experts further classify elliptical galaxies into more "box-shaped" or "disk-shaped" subtypes based on the direction of motion of the stars in the galaxy.
Star formation activity
In recent observations, researchers have discovered that some early types of galaxies still have residual gas that can be used for star formation. Although the star formation rate of elliptical galaxies is generally low, some data indicate that these black holes may inhibit the cooling process of the gas, thereby limiting star production.
Future research on elliptical galaxies
An in-depth understanding of elliptical galaxies is crucial to the study of galaxy evolution in the astronomical community. The properties of these galaxies not only help explain their relationship to spiral galaxies, but also provide important clues about large-scale structure and the evolution of the universe. In future research, how to better understand the formation of elliptical galaxies and their interactions with other galaxies will be an important issue for scientists. These galaxies are not only part of the chips of the universe, but also carry countless histories and secrets. Can we really fully understand their full picture?
