1. The universe is extremely large and consists of all time, space, energy, and matter
It contains hundreds of billions of galaxies
These galaxies exist together in super clusters
Galaxies contain hundreds of billions of stars like our Sun
Space is so large, distances are measured in light years
We are looking back in time when we observe galaxies through telescopes
The Universe

2. Gravity causes objects in space to be grouped together in different ways
The Earth is apart of a solar system, which contains our Sun, all the planets, asteroids, and comets
The solar system is part of the Milky Way Galaxy, which contains hundreds of billions of stars, like our Sun
The Universe contains hundreds of billions of galaxies
The universe is expanding, galaxies are moving away from each other…Doppler effect
The Universe

3. Types of Galaxies Our solar system lies within the Milky Way Galaxy
A Galaxy is hundreds of billions of stars held together by gravity
Milky way is a spiral galaxy, a disc with arms and a huge glowing center
Milky way is 100,000 LY across
3 types of galaxies: spiral, elliptical, and irregular…most are spiral or elliptical
Spiral: have arms of stars, gas, and dust that is in a spiral pattern
Elliptical: shaped like spheres or ovals. Most stars are old, no gas or dust
Irregular: Faint galaxies without a definite shape, smaller & few stars
Most galaxies have super massive black holes at their center
Quasars centers of galaxies are very bright & look like stars
Types of Galaxies

4. The Sun The Sun is a star, the only one in our solar system
Produces energy from hydrogen gas from fusion…gas is dense, core
Contains 99.9% of the mass of the solar system
Although the Sun is a gas, it does have structure & layers

5. Becomes cooler and less dense as you move from the center
Core: very dense gas, 15 million oC, Fusion occurs
Radiative Zone: thick layer, dense, no fusion
Convection Zone: energy moves by convection
Photosphere: a.k.a Sun’s surface, what you see, light is emitted from here
Chromosphere: Think middle layers, gives off pinkish light, hotter than photosphere
Corona: outermost, hotter than photosphere, only see during eclipse
Sunspots: cooler than other areas, appear dark
Solar Flares: Prominence ejects hot gas
Layers of the Sun

6. Classifying Stars Brightness depends on distance from Earth
To measure distance, astronomers use parallax, which is its shift in position when viewed from different locations
Color: diff. in color is a difference in temp.

7. Star Life Cycle Stars begin their life as nebula
Main Sequence is the stage when stars are turning hydrogen into helium
When H runs out it becomes a giant star and fuses He into C
Giant stars shed layers and become a white dwarf = dead core of giant star
High mass stars (8x our Sun) spend less time in MS stage…become Supergiants form elements up to iron, then collapse to produce supernovas
Cores of supergiant stars may become neutron stars or black holes
Star Life Cycle

8. Star Life Cycle