The Evolution of Milky Way Galaxy.
                     The Evolution of 
Milky Way Galaxy
Introduction
• The bright glow of the Milky Way stretching across the night sky is one of the greatest 
sights afforded us. Having inspired star-gazers for millennia, we now know that this 
band of light is the view of our home galaxy from the inside. 
Source: astronomy.swin.edu.au
The Milky Way
• The Milky Way is a typical spiral galaxy with distinct structural components. It contains a 
thin disk (diameter 100,000 light years approx.), a thick disk, a bulge (diameter 25,000 
light years approx.), and a stellar halo which is home to about 150 globular clusters.
Source: astronomy.swin.edu.au
History
• Astronomers have understood the basic properties of galaxies, at least that they’re 
large congregations of stars, gas, and dust far beyond the Milky Way, since the 1920s. 
• But really understanding galaxies, the story of their formation in the early universe and 
how they have evolved over the past 13 billion years, is a tricky struggle that challenges 
the best researchers.
Source: astronomy.com
Telescopes helped astronomers
• Larger and larger telescopes being used over the past few years have helped 
astronomers solve some questions and raise others. 
• With the Hubble Space Telescope, for example, in its Ultra Deep Field, astronomers can 
see nearly back to the universe’s infancy. 
Source: astronomy.com
Probability behind the formation of Milky way
• The Milky Way probably formed when star clusters came together to form the galaxy’s 
core. As the gas clouds rotated faster, the galaxy flattened out into a disk.
Source: astronomy.com
Research from Hubble's images
• Hubble's images suggest that the Milky Way started out as a faint blue object with lots 
of gas, clouds of which eventually collapsed to form stars.
• At the time of peak star formation throughout the universe about 4 billion years after 
the Big Bang galaxies like the Milky Way were pumping out about 15 new stars per year.
Source: astronomy.com
Research in 20th Century
• In the 20th century, astronomers discovered that our silver river is just one piece of a 
vast island of stars.
• Milky Way galaxy came together nearly 14 billion years ago when enormous clouds of 
gas and dust coalesced under the force of gravity. Over time, two structures emerged: 
first, a vast spherical “halo,” and later, a dense, bright disk. 
Source: www.quantamagazine.org
Milky Way’s violent youth
• Astronomers raced to download the dynamic star map and found evidence of epic 
collisions that shaped the Milky Way’s violent youth, as well as new signs that the 
galaxy continues to churn in an unexpected way.
Source: www.quantamagazine.org
A Still-Growing Galaxy
• The Milky Way has enjoyed a relatively quiet history in recent eons, but newcomers 
continue to stream in. Stargazers in the Southern Hemisphere can spot with the naked 
eye a pair of dwarf galaxies called the Large and Small Magellanic Clouds. 
Source: www.quantamagazine.org
Known Facts about the Milky Way
• The Sun, one of the hundreds of billions of stars comprising the Milky Way, is situated in 
the thin disk, about 25,000 light years from the center of the Galactic bulge. 
• Originally thought to be of Hubble type, astronomers now believe that the Milky Way 
has a central bar and is therefore a loosely wound.
Source: astronomy.swin.edu.au