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Formation and Evolution of Galaxies
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Formation and Evolution of Galaxies
Comets
History
- In the late 1700's Charles Messier was a Comet Hunter
- Known for finding non-comet objects
- Messier found some of the most beautiful objects you can see through a telescope
- These objects are known as the Messier List
The Pleiades
Messier Object #45
"Spiral Nebulae" Great Andromeda
Messier Object #31
The Great Debate
of 1920
More History
One side argued that these unknown objects are nearby within our solar system but are small
The other side argued that these are island galaxies similar to ours but they are far far away
Parralax Method
Parralax Method
- The Parralax method is a tool to measure the distance of far away stars
- The problem with using this method to determine the distance of the unknown objects was that these objects were much to far away
Leavitt Law
Henrietta Leavitt
- Henrietta helped determine the distance of stars that are much further away
- She did this by focusing on variable stars
- Variable stars pulsate in size and change their brightness
- This oscillation takes place over a very set period of time and said period is directly tied to the intrinsic brightness of the star
Mt. Wilson Telescope
Edwin Hubble
- Edwin applied Leviatt's method with the Mt. Wilson Telescope.
- Hubble pointed the telescope at the Spiral Nebulae Andromeda finding some variable stars
- Hubble was then able to determine the distance of Andromeda which was 2.5 million lightyears away
- This settled the great debate revealing that these objects are large and distant
- Instead of Spiral Nebula they are now called Galaxies
- Hubble also discovered that these galaxies are moving away from us meaning the universe is constantly expanding
What is a galaxy?
Galaxies
- Formation of stars and gas
- They rotate and spin with gravity in the center holding the galaxy together
- If you count up all the stars and gas in a galaxy and figure out how quickly it is rotating and how much mass needs to be there to hold the galaxy together its not enough.
- There is an unseen mass known as dark matter in the center of the galaxy that only interacts with gravity
Red Elliptical
Red Elliptial
Blue Spiral
Blue Spirals
(Milky Way)
Irregular Galaxies
Irregular Galaxies
Observations
Galaxies have a non-uniform distribution in space
About 200 Billion galaxies in the universe
Thats about it!
Time scales for galaxy change are very very slow
Similar to the earth orbiting the sun the solar system orbits the milky way but rather than taking a year to complete a full orbit it takes roughly 250 million years.
Galaxy Observations
Theory and
Simulations
Since there is no way to observe a galaxies entire formation and evolution over billions of years
Astronomers use simulations
They write a computer program creating a virtual space
Include dominant physics such as: gravity and fluid dynamics
Create initial conditions as starting point
Run simulation forwards in time
Anyalyze results and compare with observations
Irregular Galaxies
Astronomers are able to simulate the formation and evolution of a galaxy and see what that galaxy looks like all the way through its life time
This gives us answers as to why irregular galaxies are the way they are
For Example:
Irregular Galaxies
Evolution of
the Milky Way
Milkomeda
Astronomers have simulated the Milky Ways evolution and have determined that the Milky Way will collide and merge with the Andromeda galaxy in about 8 billion years
Simulation