1. Structure of the Universe

2. What makes up the Universe
Sun
Solar system
Planets – orbits the Sun
Moon
Stars
Composed of gas and emits light
Formed in Nebulae
Galaxy
Large collection of stars, gas, and
dust held together by gravity
3 shapes
Groups of galaxies
Super clusters
Universe

3. Universe Distance
Distances within the solar system are measured in astronomical units (AU)
Astronomical units – the average distance between Earth and the Sun.
Light year – the distance light travels in 1 year.
Measure of distance NOT TIME
Used to measure things beyond our solar system
The farther away an object is, the longer it takes it’s light to reach Earth.
# of AU’s in a light year = 10 trillion km

4. Measuring distance Light travels about 300,000 km/s
Closest star to the sun and Earth is
Proxima Centauri
4.3 years for light to travel to Earth.
Light from the Sun takes about 8 min to reach Earth

5. Parallax
The apparent change in an objects position caused by looking at it from two different points.
EX: extend arm – stick up thumb- close 1 eye- notice thumb – open eye – close the other – thumb appears to “jump positions”.

6. Size of the observable universe
Actual size not known
Radiation from objects that formed in early universe have not reached Earth.
Universe believed to have a radius of 14 billion years
Universe is ever expanding outward
Estimation 93 billion years

7. Structure of the universe
Universe – space and all the matter and energy in it
Galaxies dense
Clusters and super clusters
Nothing exists
Voids
New thinking:
Universe is like a spider web
Web = galaxies
Space = voids

8. Classifying Galaxies Edwin Hubble
1st person to identify groups of stars as a galaxy.
3 type of galaxies
Spiral
Elliptical
Irregular
a massive galaxy cluster found to be 160 trillion times the mass of the Sun. The detail in this mass map was made possible thanks to the unprecedented depth of data provided by new Hubble observations, and the cosmic phenomenon known as strong gravitational lensing.

9. Types of Galaxies Spiral Elliptical Irregular
Flat disks with spiral arms and bulges in their center core
Look like a pin wheel or a hurricane
Most common type
Example: Milky Way
Elliptical
Rounded, like a football or egg
Irregular
Galaxies that are neither spiral or elliptical

10. Milky Way Part of the galaxy cluster called the Local Group
Contains the Sun
The Milky Way is our galaxy.
It looks “milky” because the stars are too close together to be seen individually.