Stars are huge balls of hot glowing gas that produce heat and light through nuclear fusion reactions. They can vary in temperature, size, brightness, and color, as shown on the Hertzsprung-Russell diagram. Our sun is a yellow middle-aged star around 5 billion years old that is made up mostly of hydrogen and helium. It produces energy through nuclear fusion and provides Earth with various types of electromagnetic radiation like visible light, infrared, and ultraviolet waves.

1. The Sun & Stars

2. What is a star?
 Stars are huge bodies of hot glowing gas, that
give off energy in the form of heat and light.

3. How do stars differ from one
another?
 Stars can be different
from each other in
temperature, size, an
d brightness.
 The Hertzsprung-
Russell (H-R) diagram
shows these
differences.

4. What does the color of a
star tell us?
 The color of a star tells us its temperature.
 Hotter stars-blue
 Cooler stars-red
 Our sun is a yellow star.

5. How old is our star?
 Our sun is about 5 billion years old. It is a
middle-aged star, meaning it has about
another 5 billion years. The solar system
formed at the same time as the sun, and
therefore, has the same age.

6. What makes up our star?
 The sun is made up of hydrogen
and helium.
 Inside the sun, nuclear reactions
are taking place. Two atoms of
hydrogen are being forced
together, due to the rapid speed
at which they are
moving, forming helium. When
this happens, large amounts of
energy are being released, like
atomic bombs constantly going
off.

7. What kind of energy does the
Earth get from the sun?
 Earth receives electromagnetic
energy from the sun. This
brings the light and heat from
the sun to the earth. It includes
such types of energy
waves, such as:
 U-V waves
 Infrared waves
 Microwaves
 Gamma waves
 Visible light

8. Looking at the Hertzsprung-
Russell (H-R) diagram:
 Absolute magnitude is how
bright a star actually is
 The brighter a star is, the
lower the absolute
magnitude
 There are 4 groups of stars
that fall into the H-R
diagram
(supergiants, giants, main
sequence, and white
dwarfs)