For us, galaxies are where the most interesting events in the universe occur. Stars, planets, and black holes are all typically found within these bustling cosmic circles. However, the universe is not just galaxies. There is a vast expanse of interstellar space between galaxies. In the galactic desert, if you’re lucky you might come across a few hydrogen atoms, or at most, a wandering planet ejected from your home galaxy.
So where does a galaxy end and interstellar space begin? There seem to be many plausible ways for astronomers to define the “edge” of a galaxy. Perhaps it is where the concentration of gas or dust is below a certain threshold, or even due to the influence of the galaxy’s gravity.
Defining the edge of a galaxy
Nushkia Chamba He is a postdoctoral fellow at NASA Ames Research Center, specializing in the study of galactic neighborhoods and galaxy formation and evolution in general. Here she helps explain how astronomers define galactic edges and what factors contribute to where a particular galaxy’s edge is likely to be located. .
“Simply put, the ‘boundaries’ of galaxies have traditionally been defined using fixed levels of brightness (technically called surface brightness isophotes),” Chamba said. say. But Chamba has been spearheading recent efforts to more precisely define the edge of the galaxy. “Our work is 2020 and 2022 He was the first to discuss the alternative idea of ”edge of the galaxy” as a definition of size. ”
Specifically, Chambers and her team developed a physically motivated criterion for galactic boundaries, based on the gas density required for star formation. This means that the outermost region of a galaxy, where star formation is still occurring or likely to occur, is what Chambers and her colleagues defined as the “edge” of the galaxy.
This kind of defines the edge of the city where new housing development is still happening. It suggests that this “edge” is changing and dynamic.
read more: How many galaxies are there? Astronomers reveal the hugeness of the universe
How star formation sets the boundaries of galaxies
Because the boundaries of a galaxy are defined as a function of where star formation occurs, astronomers have studied how a galaxy’s position relative to other galaxies affects its size, and therefore maintains star formation in its outer regions. I’m interested in abilities. .
“We study how galaxies adjust their size over their lifetimes, depending on whether they are located in dense clusters of thousands of galaxies or are largely isolated. “We’ve been trying to understand how galaxies grow, and how the environment affects the growth of galaxies,” Chamba said.
Chamba was part of a team that included; this yearfound that galaxies in crowded environments are up to 50% smaller in size than galaxies in near-isolated environments.
“This is consistent with our current understanding of how galaxies undergo degassing through environmental interactions and processes that stop star formation and growth, compared to isolated galaxies that can retain gas for longer periods of time. ” she says.
“Many factors can affect the galactic edge, environment, morphology (shape and size), and mass of a stellar galaxy. (It remains to be seen how dark matter affects star formation. (and this is an open question in astrophysics), not only are the edges of galaxies modified by their intrinsic structure and environment, but also the era in which most of a galaxy’s star formation occurred. Identify. change over time” Chamba explains.
read more: Spiral arms of the universe explain how star systems form
A closer look at dwarf galaxies
Small galaxies, or “dwarf” galaxies, are more influenced by their environment. As it travels near crowded galaxies, it is likely to lose material such as gas and dust, which affects the galaxy’s capabilities. We support the formation of new stars.
recent research The study by Chambers and colleagues also sheds light on the possible role of supernovae in dispersing gas within galaxies. There, “stellar feedback” influences the flow of gas into and out of galaxies, potentially supporting or denying star formation.
Astronomers are now able to observe the concentration of gas in distant galaxies, and thus the potential for star formation. Development of deep imaging technologyTelescopes such as the James Webb Space Telescope are optimized for observing very faint light.
read more: How galaxies live, breathe, and die
Future research on galaxy formation
Chamba says researchers, for example, dark matterwhich can affect star formation in galaxies. Based on the current cosmological framework, the size of a galaxy, and therefore how much matter it is made of, is determined by the nature of the dark matter halo that exerts a gravitational influence on the surrounding baryonic matter. generally agreed upon. we are made of.
There is still much to learn about the factors that drive the evolution of galaxies over time, and Chambers is at the forefront of that effort.
read more: Black hole theory finally explains how galaxies form
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Conor Feely is a New Zealand-based science writer who looks at research at the intersection of science and philosophy, covering a wide range of topics including astronomy and neuroscience. I completed my Master’s degree in Science Communication at the University of Otago. Conor is a regular contributor to Discover Magazine, and his work has also appeared in New Scientist, Nautilus Magazine, Live Science, New Humanist, and more.
