1. STARS
There are billions of stars in our galaxy and each one is a little different than the others! This unit teaches us the physical properties of stars. When you’re done, you should be able to describe the properties of the sun and compare it to other known stars in the galaxy.

2. A star is a sphere of ionized gas.
Stars are held together by gravity
There are 4 main classifications of stars: dwarf, giant, super giant, and main sequence.
They emit heat and light.
Powered by nuclear fusion.
Composed mainly of hydrogen (H) and helium (He).

3. Brightness Absolute Magnitude Apparent Magnitude
Refers to how bright a star actually is
Also known as luminosity
Apparent Magnitude
Refers to how bright a star appears from Earth

4. Physical Properties of Stars
Color and Temperature
Star color is determined by the star’s surface temperature.
Mass
Least massive are the red dwarf stars.
Most massive are the hypergiants.
Bigger stars “burn” brighter and “die” faster than smaller stars.
Hottest Blue
Blue-White
White
Yellow-White
Yellow
Orange
Coolest Red

5. Classification of Stars
Dwarf
Small, faint, and dim
Stars are at the end of their “life cycle”
Main Sequence
Where stars spend most of their “lives”
Nuclear reactions are stable
Most stars
Giant
Large and bright
Sun-sized stars can become giant stars as they begin to “die”
Super Giant
Huge stars
Stars larger than our sun can become super giants as they begin to “die”
Can become black holes

6. The Sun’s Atmosphere Corona Chromosphere Photosphere
Superheated outer layer of the Sun’s atmosphere that emits x-rays
Chromosphere
Middle layer of the atmosphere that emits ultraviolet (UV) rays
Photosphere
Visible surface of the Sun that emits visible light

7. The Sun’s Interior Convective Zone Radiative Zone Core
Energy travels from the radiative zone to the photosphere as gases rise and fall
Radiative Zone
Energy is transferred away from the Sun’s core
Core
Hottest part of the sun
Produces energy through nuclear fusion

8. solar flare
corona
chromosphere
photosphere
convective zone
sunspot
core
radiative zone
prominence

9. Solar Activity Sunspots Solar Flares Prominences
Energy travels from the radiative zone to the photosphere as gases rise and fall
Solar Flares
Energy is transferred away from the Sun’s core
Prominences
Huge loops of relatively cool gases

10. Nuclear Fusion
High temperatures cause hydrogen nuclei to fuse forming helium nuclei and releasing energy.
Energy travels from the core to the Sun’s surface.
CONVECTIVE ZONE
RADIATIVE ZONE
PHOTOSPHERE
CORE

11. Effect on Earth
List the effects that the Sun has on Earth. Try to come up with three different things.