25.6 The Formation of the Galaxy
3 min read•june 12, 2024
The 's formation is a cosmic tale of mergers and growth. From primordial gas clouds to the grand spiral we see today, our galaxy has been shaped by with smaller galaxies and the gravitational dance of its satellites.
Evidence of this turbulent past is everywhere, from warped disks to . As we look to the future, the Milky Way's story continues with an impending collision with Andromeda, promising to reshape our galactic home once again.
Formation and Evolution of the Milky Way
Formation of the Milky Way
Top images from around the web for Formation of the Milky Way
Andromeda–Milky Way collision - Wikipedia View original
Is this image relevant?
ESA Science & Technology - A major event in the formation of the Milky Way View original
Is this image relevant?
star-forming region Archives - Universe Today View original
Is this image relevant?
Andromeda–Milky Way collision - Wikipedia View original
Is this image relevant?
ESA Science & Technology - A major event in the formation of the Milky Way View original
Is this image relevant?
1 of 3
Top images from around the web for Formation of the Milky Way
Andromeda–Milky Way collision - Wikipedia View original
Is this image relevant?
ESA Science & Technology - A major event in the formation of the Milky Way View original
Is this image relevant?
star-forming region Archives - Universe Today View original
Is this image relevant?
Andromeda–Milky Way collision - Wikipedia View original
Is this image relevant?
ESA Science & Technology - A major event in the formation of the Milky Way View original
Is this image relevant?
1 of 3
- Primordial gas clouds composed mostly of hydrogen and helium collapsed under their own gravity initiating the formation process
- As clouds collapsed they fragmented into smaller clumps which formed the first stars and star clusters ()
- Early star clusters and gas clouds eventually merged to form the proto-
- continued to grow by merging with smaller galaxies and accreting their stars and gas ()
- Mergers contributed to the growth of the Milky Way's stellar population and the formation of its halo
- Evidence of past mergers seen in the presence of stellar streams () and with distinct chemical compositions
- The process of played a crucial role in shaping the Milky Way's structure and composition
Influence of satellite galaxies
- Milky Way's disk is not perfectly flat but exhibits warps and ripples caused by gravitational tidal forces exerted by orbiting satellite galaxies
- Stellar streams are elongated structures of stars stripped from satellite galaxies during mergers ()
- contains substructures such as globular clusters and dwarf galaxies which are remnants of accreted and disrupted satellite galaxies
- Gravitational interactions with satellite galaxies have shaped key features of the Milky Way's structure and composition
Evidence for galactic collisions
- Stellar streams indicate remnants of dwarf galaxies torn apart by the Milky Way's gravitational tides in the past
- Globular clusters with distinct chemical compositions suggest they originated in previously accreted dwarf galaxies
- Milky Way's disk warps and ripples likely caused by past interactions with satellite galaxies
- (M31) currently approaching the Milky Way at ~110 km/s
- Simulations predict the Milky Way and Andromeda will collide and merge in ~4.5 billion years forming a larger galaxy ("" or "")
- Smaller satellite galaxies like the Large and Small Magellanic Clouds expected to be absorbed by the Milky Way in the future
Galactic Structure and Dark Matter
- The Milky Way's structure includes a , which contains most of the visible matter and ongoing star formation
- At the center of the galaxy lies the , a dense concentration of older stars
- The galaxy is surrounded by a , which extends far beyond the visible components and contributes significantly to the total mass
- The concept of explains how smaller structures like dwarf galaxies merged over time to form larger galaxies like the Milky Way
Key Terms to Review (23)
Andromeda Galaxy: The Andromeda Galaxy, also known as Messier 31 or NGC 224, is a spiral galaxy located approximately 2.5 million light-years from Earth. It is the largest and most massive galaxy in the Local Group, which includes our own Milky Way Galaxy. The Andromeda Galaxy's vast size, distance, and relationship to the Milky Way make it a crucial object of study in understanding the large-scale structure and evolution of the universe.
Collisions: Collisions are interactions where two or more astronomical bodies exert forces on each other, altering their trajectories and sometimes merging. They play a crucial role in the formation and evolution of galaxies.
Dark matter halo: Dark matter halo is a theoretical, spherical region surrounding galaxies, including the Milky Way, composed mostly of dark matter. It extends beyond the visible components of the galaxy and contains most of its mass.
Dark Matter Halo: A dark matter halo is a hypothetical distribution of dark matter that surrounds and extends well beyond the visible component of a galaxy. Dark matter is a mysterious substance that does not emit, reflect, or absorb light, yet it makes up a significant portion of the universe's total mass and plays a crucial role in the formation and evolution of galaxies.
Dwarf Galaxies: Dwarf galaxies are small, faint, and relatively low-mass galaxies that are typically found orbiting larger host galaxies. They are the most numerous type of galaxy in the universe and play a crucial role in the formation and evolution of larger galaxies.
Galactic Bulge: The galactic bulge is a prominent, spherical-shaped component of many spiral galaxies, including our own Milky Way. It is a densely packed region located at the center of the galaxy, containing mostly older stars with a variety of ages and compositions.
Galactic Disk: The galactic disk is a flattened, disk-like component of a galaxy that contains the majority of the galaxy's stars, gas, and dust. It is the primary location where most of a galaxy's star formation and stellar activity occurs, making it a crucial feature in understanding the architecture, stellar populations, and formation of a galaxy.
Galactic Halo: The galactic halo is a spherical or ellipsoidal region surrounding the disk and bulge of a galaxy, consisting of diffuse gas, stars, and other matter not concentrated in the galactic plane. It is a crucial component in understanding the architecture, mass, stellar populations, formation, and evolution of galaxies.
Galaxy Merger: A galaxy merger is the process in which two or more galaxies collide and combine to form a single, larger galaxy. This event is a crucial aspect of galaxy formation and evolution, as it significantly shapes the structure and properties of galaxies over cosmic time.
Globular clusters: Globular clusters are tightly bound groups of stars, typically containing hundreds of thousands to millions of members. They orbit the galactic core and are among the oldest objects in the universe.
Globular Clusters: Globular clusters are dense, spherical collections of tens of thousands to millions of old stars gravitationally bound together. They are found in the outer regions of galaxies, including the Milky Way, and provide insights into the formation and evolution of galaxies.
Hierarchical Structure Formation: Hierarchical structure formation is a fundamental concept in cosmology that describes the evolution of large-scale structures in the universe. It explains how matter in the universe organizes itself into a hierarchical pattern of structures, from small-scale objects like galaxies to large-scale structures like galaxy clusters and superclusters.
Large Magellanic Cloud: The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way, located approximately 163,000 light-years from Earth. It is one of the closest galaxies to our own and serves as an important laboratory for studying stellar evolution, variable stars, and the formation and distribution of galaxies in the universe.
Milkdromeda: Milkdromeda is a hypothetical future merger of the Milky Way and Andromeda galaxies, which are currently on a collision course and expected to combine into a single, larger galaxy in several billion years. This cosmic event will dramatically reshape the night sky and have significant implications for the evolution of the resulting galactic system.
Milkomeda: Milkomeda is the hypothetical future merger of the Milky Way and Andromeda galaxies, which are expected to collide and form a single, larger galaxy over the next few billion years. This cosmic event is a key aspect of the formation and evolution of our galaxy.
Milky Way: The Milky Way is the galaxy in which our solar system is located, comprising hundreds of billions of stars and vast amounts of gas and dust. It is a spiral galaxy, with a central bulge and a rotating disk of stars, gas, and dust. The Milky Way is an essential component in understanding the structure, formation, and evolution of the universe, as it provides a window into the larger cosmic landscape.
Milky Way Galaxy: The Milky Way Galaxy is the spiral galaxy that includes our Solar System, characterized by its barred structure and multiple spiral arms. It is one of billions of galaxies in the universe and contains over 200 billion stars.
Orphan Stream: An orphan stream is a stellar stream that is not associated with any known galaxy or globular cluster. These streams are believed to be the remnants of dwarf galaxies or star clusters that have been tidally disrupted and dispersed over time, leaving behind a trail of stars orbiting the Milky Way.
Proto-Milky Way: The proto-Milky Way refers to the early, formative stage of our galaxy, the Milky Way, before it reached its current mature state. It represents the initial conditions and evolutionary processes that led to the formation and development of the Milky Way as we know it today.
Protogalactic cloud: A protogalactic cloud is a massive gas cloud that existed in the early universe and is believed to be the precursor to galaxies. These clouds primarily consist of hydrogen and helium.
Sagittarius Stream: The Sagittarius Stream is a stream of stars that originates from the disruption of a dwarf galaxy that was gravitationally bound to the Milky Way. This stream of stars orbits the center of the Milky Way and provides valuable insights into the formation and evolution of our galaxy.
Small Magellanic Cloud: The Small Magellanic Cloud is a dwarf irregular galaxy that is a satellite of the Milky Way Galaxy. It is one of the closest galaxies to the Milky Way and provides valuable insights into the formation and evolution of galaxies.
Stellar Streams: Stellar streams are long, narrow structures of stars that are gravitationally bound and move together through the Milky Way galaxy. They are the remnants of disrupted dwarf galaxies or globular clusters that have been tidally stripped and stretched out by the gravitational forces of the Milky Way over time.