Or Graur on the Big Bang and the Physics of Galaxies
Aug 7, 2024
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Astrophysicist Or Graur, an associate professor at the University of Portsmouth and author of 'Galaxies,' delves into the universe's grandeur. He discusses the groundbreaking findings from the James Webb Space Telescope, which reveal complex, ancient galaxies formed shortly after the Big Bang. Graur explores the formation and lifecycle of spiral galaxies, their transformation of gas into stars, and the intricate relationship with dark matter and black holes. He also touches on the vastness of the Milky Way and the intriguing questions of life beyond Earth.
The James Webb Space Telescope's observations reveal early galaxies were surprisingly larger and more structured than previously anticipated soon after the Big Bang.
Galaxies are interconnected within groups and clusters, altering our understanding of cosmic scale and the dynamics of the universe's structure.
Deep dives
Breathtaking Discoveries of the James Webb Space Telescope
The James Webb Space Telescope has made significant contributions to our understanding of early galaxies, revealing that they appeared larger, more structured, and more numerous than previously expected within just a few hundred million years after the Big Bang. Observations include the surprising presence of massive black holes in these early galaxies, challenging existing timelines for their formation. Astrophysicist Orr Grauer highlights that while some findings seem to disrupt established models like lambda-CDM, it's essential to remain cautious and await more comprehensive data over the coming years. The observational capabilities of the James Webb Space Telescope are reshaping our understanding of the universe's structure and the dynamics within it.
Types and Formation of Galaxies
Galaxies come in various types—including spiral, elliptical, and irregular—and their forms are closely related to their ages and the processes of their formation. Spiral galaxies, for instance, have disk-like structures, while older elliptical galaxies tend to be more spherical. The formation of these galaxies is influenced by the dynamics of gas and dark matter, with gas settling into disks due to angular momentum over billions of years. Understanding these differences helps astronomers trace the evolution of galaxies and the overall structure of the universe.
Galaxies, Clusters, and the Cosmic Web
Galaxies are not isolated; they exist within groups and clusters, which are held together by gravity. The Milky Way, for example, is part of the Local Group that includes a few dozen galaxies, while larger clusters can contain hundreds or even thousands of galaxies. Understanding the relationships between galaxies and their clusters changes the perception of cosmic scale, illustrating how these massive structures form a complex web across the universe known as the cosmic web. This interconnectedness impacts our understanding of galaxy formation and the distribution of matter in the universe.
The Role of Dark Matter and Supernovae in Cosmic Measurements
Dark matter makes up a substantial portion of the total mass in galaxies, influencing their structure and behavior. Rotational speeds of stars within galaxies provide critical evidence for the existence of dark matter, as observed by astronomers like Vera Rubin, who noted unexpected velocities that indicated unseen mass. Additionally, Type 1a supernovae serve as critical standard candles for measuring astronomical distances, which allows for an understanding of the universe's expansion. The interplay between dark matter, black holes, and supernovae is essential in deriving cosmological distances and gauging the consistent evolution of galaxies throughout time.
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Astrophysicist Or Graur offers a brief and fascinating overview of the history, physics, and astrophysical uses of galaxies. Starting with the history of the last two thousand years of galaxy studies, Graur discusses the types of galaxies we observe and the physics that drive them; the myths and physical structure of the Milky Way; how galaxies were used to discover and study the mysterious phenomena of dark matter and dark energy; and how scientists think galaxies formed shortly after the Big Bang and evolved to their present forms.
Or Graur is Associate Professor of Astrophysics at the University of Portsmouth's Institute of Cosmology and Gravitation, as well as Research Associate at the American Museum of Natural History. He is the author of "Supernova" and his latest book, "Galaxies" from MIT Press.
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