The sun is the largest object in the solar system, containing over 99% of its mass. It emits light and heat that support life on Earth and influence all solar system objects. The sun has various internal layers, including the core where energy is produced through nuclear fusion, and an outer atmosphere. Sunspots, solar flares, and other features periodically appear on its surface. In a few billion years, the sun will expand and grow hotter, eventually making Earth uninhabitable.

1. THE SUN

2. The sun is by far the largest object in
the solar system. It contains more than
99.8% of the total mass of the Solar
System .
The strong gravitational pull of the
Sun holds Earth and the other planets in
the solar system in orbit. The Sun’s light
and heat influence all of the objects in the
solar system and allow life to exist on
Earth.

3. Equatorial Radius: 695,500 km
Equatorial Circumference: 4,379,000 km
Volume: 1,142,200,000,000,000,000 km3
Mass: 1,989,000,000,000,000,000,000,000,000,000 kg
Density: 1.409 g/cm3
Surface Area: 6,087,799,000,000 km2

4. The Sun is an average star—its
size, age, and temperature fall in about
the middle of the ranges of these
properties for all stars. Astronomers
believe that the Sun is about 4.6 billion
years old and will keep shining for about
another 7 billion years.

5. Composition of the Sun
Abundance Abundance
Element (percentage of total (percentage of total
number of atoms) mass)
Hydrogen 91.2 71.0
Helium 8.7 27.1
Oxygen 0.078 0.97
Carbon 0.043 0.40
Nitrogen 0.0088 0.096
Silicon 0.0045 0.099
Magnesium 0.0038 0.076
Neon 0.0035 0.058
Iron 0.0030 0.14
Sulfur 0.0015 0.040

6. Solar Winds
•expanding atmosphere with a constant flow of
tiny, fast, electrically charged particles.
•carries remnants of the Sun’s magnetic field,
which affect the magnetic fields of the planets and
larger satellites. The solar wind pushes the planets’
magnetic fields away from the Sun, turning them
into elongated, windsock shapes.
•The solar wind spreads out as it leaves the Sun
•causes auroras—displays of colored light—in the
atmosphere of Earth’s polar regions.

7. Heliosphere
- region through which the solar wind
blows
Within the heliosphere, the Sun provides
most of the heat and light that are present, and
the particles in the solar wind interact with the
planets and satellites in the solar system.

8. Layers of the Sun

9. - innermost layer of the sun
- it is where the energy that keeps
the sun shining produced
-16 million ºC. in a gaseous state.

10. Solar Envelope
- puts pressure on the core and maintains the
core's temperature.
- The hotter a gas is, the more transparent
it is. The solar envelope is cooler and
more opaque than the core. It becomes
less efficient for energy to move by
radiation, and heat energy starts to build
up at the outside of the radiative zone.

11. -is the lowest, densest level of the solar
atmosphere.
- This is the light we see. That’s why we see
this as the surface.
The photosphere is opaque (not
transparent), because it contains negative
hydrogen ions (a hydrogen atom with two
electrons, instead of the usual one). Hydrogen
ions block, absorb, and emit light, all of which
prevent light from passing directly through a
cloud of hydrogen ions.

12. “Sphere of Color”
-Very low density
-But also very hot
- Energy from below excites the atoms
and produces emission from this layer.
-Predominant element – Hydrogen.
-Brightest hydrogen line

13. A prominence is a feature of
a layer of the Sun’s atmosphere called
the chromosphere. Magnetic fields
suspend loops of gas—prominences—
above the main photosphere layer.
These loops are actually cooler than
the rest of the photosphere, but they
still appear bright against the dark
sky.

15. Corona
-outermost layer of the sun
-Only visible during eclipses, it is a low
density cloud of plasma with higher
transparency than the inner layers.
-Its average temperature is 1 million K
This picture of the corona was taken during a total solar eclipse
on July 11, 1991, in La Paz, Baja California, Mexico.

16. -cool, dark, temporary patches
Sunspot that appear on the outer visible
layer (photosphere) of the Sun.
Sunspots occur where areas of
the Sun’s magnetic field loop up
from the Sun’s surface,
disrupting the convection of hot
gases from below. Sunspots are
typically about half the
temperature of the surrounding
photosphere and so appear
darker.
-The largest sunspots can be
wider than earth.

17. Importance of the Sun
The Sun provides Earth with
vast amounts of energy
every day.
The oceans and seas store
Plants use this energy and help keep
the Sun’s
the temperature of Earth
energy to make food, and
at a level that allows a
plants provide food for life to
wide variety of
other organisms.
exist.

18. The Sun cannot shine forever, because it
will eventually use up its present fuel. The
nuclear fusion reactions that make the Sun glow
depend on the element hydrogen, but the
hydrogen in the Sun’s core will eventually run
out. Nuclear reactions have converted about 37
percent of the hydrogen originally in the Sun’s
core into helium. Astronomers estimate that the
Sun’s core will run out of hydrogen in about 7
billion years.

19. In 3 billion years, the Sun will be hot
enough to boil Earth’s oceans away. Four billion
years thereafter, the Sun will have used up all its
hydrogen and will balloon into a giant star that
engulfs the planet Mercury. At this point in its
life, the Sun will be a red giant star. The Sun will
then be 2,000 times brighter than it is now, and
hot enough to melt Earth’s rocks. At this time the
outer solar system will get warmer and more
habitable. The icy moons of the giant planets may
warm enough to be covered by water instead of
ice.