Скачать или смотреть The Milky Way: Our Home Galaxy in the Cosmos

#MilkyWay #Andromeda #GalacticExploration #DarkMatter #SupermassiveBlackHoles #Astrophysics #GalaxyDynamics #SpiralArms #xrayobservations

This is the twelfth lecture series of my complete online introductory undergraduate college course. This video series was used at William Paterson University and CUNY Hunter in online classes as well as to supplement in-person course material.

In this series of videos, we embark on a captivating journey through the Milky Way and Andromeda galaxies, uncovering their intricate structures and dynamic processes. We begin our exploration by analyzing the Milky Way’s spiral arms, which serve as remarkable sites of star formation. These arms are formed through the gravitational interaction of gas clouds and the presence of young, hot stars, specifically type O and B stars. The illumination provided by these stars highlights the arms, which act as dense regions of stellar creation, showcasing the ongoing processes that fuel the galaxy’s evolution. As we delve into the dynamics of the Milky Way, we focus on its rotation, which presents intriguing anomalies. Through the examination of rotation curves, we discover that the inner regions rotate as a solid body, while the outer regions exhibit differential rotation. This means that the orbital speed of stars and gas remains roughly constant, regardless of their distance from the galactic center. This observation challenges our understanding of galactic dynamics based on the expected Keplerian drop-off, where objects farther from the center should orbit more slowly. The discrepancy between these expectations and observations leads astronomers to propose the existence of dark matter—an unseen form of matter that does not emit light but exerts gravitational influence. The implications of dark matter are profound. To maintain the constant rotational speed observed at greater distances from the galactic center, there must be significant mass beyond the visible stars and gas. Researchers employ various methods to study dark matter, including the analysis of rotation curves from external galaxies, searching for microlensing events, and observing gravitational lensing effects produced by galaxy clusters. Collectively, these approaches indicate that dark matter is pervasive, extending well beyond the luminous parts of galaxies and constituting a substantial portion of the universe’s total mass. Our exploration continues as we turn our attention to the centers of the Milky Way and Andromeda galaxies. Using advanced observational techniques with the Chandra X-ray Observatory and the Hubble Space Telescope, we obtain detailed views of the turbulent inner landscapes of these galaxies. In Andromeda, we observe intense X-ray emissions emanating from its core, revealing bright point-like sources and diffuse light that indicate active processes occurring in this region. As we examine the Milky Way’s central region, which spans approximately 400 by 900 light years, we discover a cluttered environment filled with neutron stars, black holes, and hot diffuse gas radiating at millions of Kelvin. Observations in radio wavelengths, conducted by the Very Large Array (VLA), reveal spherical features resulting from supernova remnants and magnetic fields, which create snake-like structures in the gas. Focusing on Sagittarius A*, the supermassive black hole at the Milky Way’s center, we find that it exerts immense gravitational influence on surrounding stars. The Galactic Center Group at UCLA has mapped the stellar motions over 20 years, confirming the existence of this massive object. The orbit of the star S0-2, which completes a full orbit every 20 years, has enabled astronomers to distinguish between Newtonian gravity and Einsteinian gravity, further enhancing our understanding of the dynamics at play in the galactic center. In summary, our journey today takes us from observing the central mysteries of Andromeda to the heart of our own Milky Way, revealing the fascinating dynamics driven by supermassive black holes at their centers. This exploration provides compelling evidence for the existence of black holes and enhances our understanding of their fundamental nature and influence in shaping galaxies. Join us as we unravel the secrets of the Milky Way and Andromeda, shining a light on the dynamic and turbulent cores of these captivating galaxies.

0:00:00 - Our Cosmic Address
0:14:51 - The Great Cosmic Distance Debate
1:06:29 - The Milky Way's Many Faces
1:35:14 - Stellar Neighborhoods: the Population I and II Stars
1:53:35 - The Galaxy's Formation, Evolution and Fate
2:13:31 - The Milky Way's Spiral Arms
2:39:57 - Dark Matter in the Milky Way and Beyond
3:24:06 - The Supermassive Black Hole at the Center of the Milky Way