Milky way galaxy movement
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Milky Way Galaxy Movement: Structure, Kinematics, and External Influences
Milky Way Spiral Structure and Internal Motion
The Milky Way is a barred spiral galaxy with four major spiral arms and a strong central bar. The bar rotates at about 35–40 km/s per kiloparsec, completing a rotation every 160–180 million years. This bar, along with the spiral arms, drives the movement of stars within the galaxy, causing radial migration and trapping or scattering stars near orbital resonances. The bar and spiral arms together account for a significant portion of the galaxy's stellar mass and play a key role in shaping the internal kinematics of the Milky Way 63.
Galactic Disk Dynamics and Recent Perturbations
The Milky Way's disk is dynamically young and has been recently perturbed. Analysis of the motions of millions of stars reveals substructures in phase space, such as snail shells and ridges, indicating that the disk was disturbed between 300 and 900 million years ago. This timing matches the last close passage of the Sagittarius dwarf galaxy, suggesting that interactions with satellite galaxies can cause significant dynamical heating, ring-like structures, and complex velocity patterns in the disk .
Influence of the Large Magellanic Cloud (LMC) and Satellite Galaxies
The Large Magellanic Cloud (LMC), the Milky Way's most massive satellite, is currently making its first close approach, moving at about 327 km/s. Its gravitational pull is strong enough to dislodge the Milky Way disk from the galactic center of mass, causing a reflex motion detectable in the kinematics of outer halo stars and satellite galaxies. This means that models of the Milky Way must account for the LMC's influence, as it significantly affects the galaxy's motion and the reference frame for observing the stellar halo 110.
Many of the Milky Way's dwarf satellite galaxies, including those associated with the LMC, follow orbits that are highly concentrated near their pericenters and often share a common orbital direction. This suggests a real structure in the distribution of satellites, with many co-orbiting along a vast polar structure. Some ultra-faint dwarfs are on high-velocity, eccentric, retrograde orbits, and several may be on their first infall into the Milky Way, further highlighting the dynamic and evolving nature of the galaxy's outer regions 257.
Motions of Globular Clusters and Dwarf Galaxies
Globular clusters and dwarf galaxies in the Milky Way halo exhibit a range of orbital behaviors. Clusters in the inner 10 kpc show significant rotation, while those farther out have more radially anisotropic orbits. The 3D velocities of these objects, measured with high precision using Gaia and Hubble Space Telescope data, help constrain the mass and gravitational potential of the Milky Way. These measurements also reveal that some clusters and dwarfs were likely accreted from other galaxies, while others formed within the Milky Way itself 4957.
The Milky Way’s Place in the Local Group
The Milky Way is the second-largest galaxy in the Local Group, which includes more than 50 galaxies. Its interactions with nearby galaxies, especially the LMC and Small Magellanic Cloud (SMC), are ongoing and have a profound impact on its structure and motion. Recent data show that the LMC and SMC are likely on their first orbit around the Milky Way, challenging previous assumptions and providing new insights into the galaxy's evolution .
Conclusion
The movement of the Milky Way galaxy is shaped by its internal structure—bar, spiral arms, and disk—as well as by ongoing interactions with satellite galaxies like the LMC and Sagittarius dwarf. These interactions cause significant perturbations, reflex motions, and complex orbital patterns among stars, clusters, and satellite galaxies. Modern astrometric surveys, especially Gaia, are providing unprecedented detail on these motions, allowing astronomers to refine models of the Milky Way’s dynamics and its place in the cosmic neighborhood 1234+6 MORE.
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