Transcript Star and Sun Properties

What this Mini-Lesson Will Cover:
1. How do you interpret the HR Diagram?
2. Where does a star’s energy come from?
3. What are the physical properties of our
Sun?
Day 1: What Are Stars?
 A star is a large celestial body that is composed of hot
gas and that emits light; the sun is a typical star
• The Sun, our closest star, is 93 million miles from Earth.
• The next closest star is 4.3 lighter years away.
• By mass, the Sun is 71 % Hydrogen, 27% helium and the
rest heavier element. This is similar to the composition
of the universe.
• The Sun is about 4.6 billion years old.
Day 1: Sun’s Energy
 The Sun, like all stars, are driven by nuclear fusion
reactions.
• The core of a star is extremely hot, extremely dense, and
under extreme pressure.
• Nuclear fusion takes place in the core of a star.
• The Sun’s nuclear fusion combines the nuclei of hydrogen
atoms to form a helium atom.
• In a nuclear reaction some of the matter is converted in to
Energy per the equation E = MC2
Day 3: Stellar Equilibrium.
 The Sun is in stellar equilibrium. The inward force of
gravity is balanced by the outward force of gas
pressure caused by the Sun’s high core Temperature.
Day 2: Hertzsprung-Russell Diagram
 The H-R diagram is used to classify stars.
• The vertical line on an H-R diagram indicates brightness
in absolute magnitude (true brightness of a star).
• The horizontal line on the H-R diagram indicates
temperature.
• Most stars appear in a diagonal line called the main
sequence (white band on chart).
• As stars age and pass through different stages, their
positions on the H-R diagram change.
Day 2: H-R Diagram
1. Where are most
stars located on the
HR Diagram?
2. What two
properties
determines a stars
absolute
magnitude?
3. Which color stars
are the hottest and
which are the
coolest?
4. From Earth, Sirius
is the brightest star
on our night sky.
How can it appear
brighter than
Betelgeuse?
Day 3: Interpreting Graphics
Base your answers to questions 1 through 4 on the
illustration below.
1.
Which of these
stars would
appear to be
brightest if all of
them were
observed from the
same distance?
A.
B.
C.
D.
Aldebaran
Canopus
Sun
Vega
Temperature
Day 3: Interpreting Graphics
2.
3.
Proxima Centauri,
in the lower left, is
the closest star to
the Earth. Why is
it hard to see from
Earth?
Which of these
stars is most likely
to become a white
dwarf in the near
future?
A. Betelgeuse
B. Sirius
C. Proxima
Centauri
D. Alpha
Centauri
Temperature
Day 3: Interpreting Graphics
4. Why does Sirius appear
brighter in the night
sky than Betelgeuse?
A.
Sirius is a brighter star
than Betelgeuse.
B.
Betelgeuse is farther
from Earth than Sirius.
C.
Betelgeuse is cooler
than Sirius, so it does
not emit as much
light.
D.
Sirius has a smaller
diameter, so it is a
more concentrated
light source.
Temperature
Day 3: Answers
 1. B Canopus – it is highest on the absolute
magnitude scale.
 2. Proxima Centauri is small and has a low
temperature compared to other stars.
 3. A, The next stage after red giant is a white dwarf.
 4. B,