Stars are gigantic balls of hot gases that emit electromagnetic radiation. Their color indicates temperature, from coolest red stars to hottest white or blue-white stars. The Sun is an average-sized yellow star that is the closest star to Earth and the brightest object in the sky. It is a fiery ball of hot gases composed of layers including the photosphere, chromosphere, and corona. Solar flares and prominences are linked to the sunspot cycle and can last from minutes to months. A star is born in a nebula and dies when it runs out of hydrogen fuel.

1. What is a star?
Lesson 2

2. Stars
• Gigantic balls of
very hot gases that
give off
electromagnetic
radiation

3. • There are many
different sizes and
colors of stars.
• A star’s color
relates to how hot it
is…
– Red stars are coolest
– Orange and yellow
– White or blue-white
stars are the hottest

4. The Sun
• An average size star
• Closest to the Earth
• Brightest star in the
sky
• Enormous amounts
of light and heat
energy

5. Short Review…
1. Which star is hotter, a yellow star or a
white star?
2. What star is the closest to the Earth?

6. • The Sun is a
fiery ball of hot
gases with no
hard surfaces.
• The Sun’s
layers include
the
photosphere,
the
chromosphere,
and the corona.

7. The Explosive Sun
• The part of the Sun
that gives off the light
we see is called the
photosphere.
– It is the lowest layer of
the Sun’s atmosphere.
• The layer above the
photosphere is the
chromosphere.
• The outermost layer
is called the corona.

8. Sunspots
• Dark spots on the
face of the Sun
• The size of Earth or
larger
• Sunspots occur in the
Sun’s photosphere.
• The number of
sunspots changes in
cycles of about 11
years.

9. Solar Eruptions
• Linked to the sunspot
cycle:
– Solar Flare
• Parts of the
chromosphere erupt like
a volcano
• Can last from minutes to
hours
• May interrupt radio
communications on
Earth
– Prominence
• Ribbons of glowing gas
• Can last from minutes to
months

10. What is a Light-Year?
• The distance light
travels in one year,
5,880,000,000,000
miles

11. Short Review…
1. How long do solar flares last?
 from minutes to hours
1. Name two solar eruptions.
 Solar flares
 prominences

12. The Life of Stars
• A star is born in a cloud of gas and dust
called a nebular
• A star dies when it runs out of fuel—
hydrogen.
https://www.youtube.com/watch?v=80eMTnnLjhs