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- The galaxy that our solar system resides in.
- Appears as a white ~hazy~ band across the sky
- Is about 100 000 light years long, and 10000 light years thick.
- The solar system is located in the Milky Way's Orion arm.
- A large collection of stars, planets, gas, and dust all held together by gravity.
- Example: the Milky Way
A collection of stars inside a galaxy held together by gravity
- 50-1000 stars
- Located in the main band of the Milky Way
- 100 000 to million stars in a distinct spherical shape.
- They are located around the center of the milky way (its bulge)
- 40 galaxies that the Milky Way is a part of
- Around 10 million light years in diameter
- Milky Way and Andromeda are largest of the group
- Most are ellipticals and companions to larger galaxies
- A cluster of Galaxies groups
- 4-25 clusters of galaxies.
- 100s of millions of light years in size.
- A supercluster is a collection of local groups
"Pinwheel" shape with long arms spiraling out from core. Side view has a large bulge in the middle. Most stars in this galaxy are new and there is lots of space for stars to form.
- Either in the shape of a perfect circle or long ellipse.
- This is the largest type of galaxy
- Amount for over half of all galaxies in the universe.
- Contain some of the oldest stars in the universe.
- Galaxies without a regular shape.
- Mixture of old and new stars most likely from the collision of multiple spiral and elliptical galaxies.
The study of the ~universe~.
- When spectral lines are displaced from their normal positions.
- When light is moving away from you, the light frequency stretches out. When they are getting closer to you, they are compressed together.
- When a siren is far from you and is coming closer, the pitch gets higher due to the waves being compressed. When the siren is moving away from you the pitch get lower since the wavelengths are being stretched.
- Longer wavelengths are for the red end of the spectrum.
- When objects move away from you, the wavelengths are stretched, therefore showing red visible light in the spectrum
- If a galaxy is moving away from you, the spectral lines are redshifted.
- When an object is getting closer to you, the wavelengths are compressed. Shorter wavelengths are associated with the violet/blue end of the spectrum.
- So when a galaxy is nearing you, the spectrum would be blueshifted
- The speed of the galaxy (determined by redshift) is proportional to the distance of the galaxy from Earth.
- According to this theory, all galaxies started moving outwards at the same time.
- a galaxy moving twice as fast is now twice as far away.
- The slope of a graph describing the relationship between a galaxy's distance from Earth and speed.
- The hubble constant is the rate at which the universe is expanding.
- George Gamow, discovered the relationship and realized, the universe is expanding.
- Before the Big Bang, the universe was compact and very dense.
- The big bang happened 14 billion years ago.
- The universe began expanding in a hot and violent fashion.
- Basically a very big explosion that caused the universe to expand.
Cosmic Microwave Background (CMB) (concept)
- When the radiation left over from the Big Bang expands to other forms of electromagnetic radiation.
- When the universe first exploded, it was very hot and filled with gamma rays. As the universe expanded, the wavelengths of the radiation stretched into visible light and now currently microwave wavelength. Microwaves are stretched out more than the original gamma rays proving that the universe expanded from a point.
The radiation left over from the Big Bang that fills the universe
- Invisible to telescopes
- Most abundant matter in the universe.
- Dark Matter makes up 23 percent of the universe.
- Visible light is 4 percent.
Reasons for Theorizing Dark Matter
- The reason Dark Matter was theorized is because stars in Andromeda were moving at such high speeds than expected. The only way to fill in the gap of knowledge was to theorize that there was 90 percent more mass than they are able to see.
- Another theory is that the motion of the galaxies orbiting the Milky Way shows that the Milky Way is 10 x larger than estimated.
- An "anti-gravity" effect.
- Instead of gravity slowing the expansion of the universe, this mystery force, was causing the expansion to accelerate.
- Make up the remaining 73 percent of the entire universe