6. Are the stars same in size? Are
the stars same in color? Are
the stars equally bright? When
we look at the sky, we see
thousands of stars. In reality,
there are approximately 400
billion stars in our galaxy, and
there are about 170 billion of
galaxies.
WHAT IS A STAR?
7. Sun is only about 150 million
kilometers away, and it takes
only 8 minutes and 20 seconds
for sunlight to reach our world.
It’s diameter is about 1.4
million kilometers, 100 times of
the earth. But yet it is only a
medium-size star. Many other
stars are much, much bigger.
THE SUN
8. • Color and Temperature
• Brightness and Magnitude of
Stars
• Sizes of Stars
• Distance of Stars
• Composition of Stars
CHARACTERISTICS OF STARS
9. Which star is the hottest?
RED BLUE
Which star is very similar to our sun?
YELLOW ORANGE
Which is the coolest star?
BLUE YELLOW
SHORT REVIEW
10. Let’s play a game, our class is divided into two groups. In
three minutes I want you to identify the following color of
each star based on their temperature.
STAR COLOR TEMPERATURE
Sun 5,700
Vega 9,900
Alnilam 27,000
Sirius 10,000
Proxima Centuari 2,300
Epsilon Iridani 4,600
TEMPERATURE AND COLOR
12. Stars emit colors of many different
wavelengths, but the wavelength of
light where a star's emission is
concentrated is related to the star's
temperature - the hotter the star, the
more blue it is; the cooler the star, the
more red it is.
COLOR AND
TEMPERATURE
13. • Star color ranges from red to blue.
The color of star indicates its surface
temperature.
• The coolest star is about 2800 ℃ at
the surface. These star appear red.
The temperature of the hottest star is
about 28 000℃ or higher. These star
appear blue.
17. The star’s brightness as seen from
Earth is its apparent brightness.
Apparent brightness depends on
how far a star is from the Earth. On
Figure 1 Sirius appears bigger than
Rigel, is actually very small
compared to Ringel. It appears
larger only because it is closer to us.
DISTANCE
18. Astronomers consider the star’s
absolute brightness when
comparing stars. A star’s
absolute brightness is the
brightness the star would have if
all stars were the same standard
distance from earth.
ACTUAL BRIGHTNESS
19. • Stars varies in size, from huge to
supergiants to tiny neutrons stars.
• Astronomers group stars into five
types:
• Neutron stars, white dwarfs,
medium-sized stars, giants and
supergiants.
SIZES OF STARS
20. • Neutron stars are the smallest, it has a
diameter of about 16 km.
• White dwarf is about 7300 km., slightly
greater than that of earth.
• Medium-sized star is about one-tenth the
diameter of the sun.
• Giant star is 10 to 100 times that or the sun.
• Supergiant stars is up to 1000 times the
diameter of the sun.
21.
22. • Scientist use parallax to determine how far
away a star is from Earth. A parallax is an
apparent change in the position of an object
caused by a change in the position of the
observer.
• The closer a star is to Earth, the greater its
apparent change of position. Very distant
stars seem not to shift position at all.
DISTANCE OF STARS
23. • Scientist express distances between stars in
light years. A light year is the distance that
light travels in one year at a speed of 300
000 km per second (kps). A light year is
about 9.5 trillion km or 9 500 000 000 000
km.
• The closest star is Proxima Centauri, 4.2
light years from Earth. Other stars are
hundred of light years away.
24. Using spectroscope, astronomers have found
that almost all stars have the same general
chemical make up. The most element in stars is
hydrogen, the lightest element that make 60%
to 80% of the total mass of a star. The second
element is Helium, make up about 96% to 99%
of stars mass.
Other elements are oxygen ,neon ,carbon , and
nitrogen.
COMPOSITION OF STARS
25. Stars is composed mostly of two lightest
elements
Hydrogen Helium
STARS
27. Observers in ancient times
also imagined group of
stars that form pictures of
animals, objects, and
people. These imaginary
groups of stars are called
constellations.
CONSTELLATIONS
28. Many constellations have names that can be traced
back early Babylonians and Greek civilizations, but
nearly all cultures have different names for the
constellations. For example, Greeks called the large
constellation Orion, which means hunter and is
prominent in the night sky all over the world
during winter. Early Filipinos visualized the same
group of stars as Balik, a trap used in hunting wild
pigs. Christian Filipinos named the three stars
(Orion’s belt) Tatlong Maria or Tres Marias.
CONSTELLATIONS
34. By observing the Sun’s movement and
position in the sky, we can tell what time
of the day it is. When it seems to rise in
the east, it is morning. When it is above us,
it is noon. When it seems to move towards
the west, it is afternoon. At night, stars are
used to tell the time. Just like the sun, stars
also seem to move from east to west.
APPARENT MOVEMENT OF THE
STARS THROUGH THE NIGHT
35. Polaris, commonly known as the
North Star, is the brightest star in the
constellation Ursa Minor (Little
Dipper). It is very close to the north
celestial pole, making it the current
northern pole star. Because it lies
nearly in a direct line with the axis of
Earth’s rotation “above” the north
Pole, Polaris stands almost motionless
in the sky, and all the stars of the
Northern sky appear to rotate it.
THE POLARIS
36. Star trail is a type of
photograph that
utilizes long-exposure
times to capture the
apparent motion of
stars in the night sky
due to the rotation of
the Earth.
STAR TRAIL
37. In Metro Manila, when you face
North Polaris, which is 11.3° from
the horizon is seen at around 15°
due to atmospheric refraction. In
some parts of the country (i.e
Southern Philippines), it would be
difficult to locate Polaris since
starlights near the horizon are
washed out by lights lit by men, or
obstructed by man-made or
topographical structures or trees.
POLARIS
38. To locate the Polaris, face
North and locate the Big
Dipper. Two stars (Merak
and Dubhe) in the Big
Dipper are called pointer
stars because they seem to
point to Polaris.
HOW TO LOCATE
POLARIS?
44. The rotation of the earth on its axis
causes the apparent nightly
movement of the stars across the
sky, the revolution is responsible for
the fact that we can see different
parts of the sky at different parts of
the year.
STARS APPEAR TO MOVE
IN THE NIGHT SKY
45.
46. An observer from Earth will be
able to see the stars that are on
the night side. The stars on the
same side as the sun cannot be
seen because sunlight
overpowers all the starlights.
47. During summer in the Philippines, the
constellations of Orion and Taurus are not
visible at night. They will be visible again as
the cold season begins. During this time,
Scorpio will not be seen in the night sky.
The Earth revolves around its orbit, the
stars that were concealed by the bright light
of the Sun in the previous months will
appear in the night sky.
49. While constellations were associated with
religion, they also have practical uses.
Before calendars, people had no way of
determining when to sow or harvest
except by looking at these patterns in the
sky. Ancient people developed a way to
remember the patterns by giving them
names and stories.
USES OF
CONSTELLATIONS
50. For example, in the northern hemisphere, the
constellation Orion indicates the coming of
cold season. The constellations made easier for
them to recognize patterns in the sky. For
example, Gemini is seen in the Philippines
during the months of April and May. Farmers
interpreted the appearance of Gemini as the
end of planting season and it signified rich
harvest.
USES OF
CONSTELLATIONS
53. Another use of constellation is navigation.
The polaris used in navigation because it
does not change its position at any time of
the night year. Also, one can figure out
his/her latitude just by looking at how
high Polaris appears in the night sky. This
allowed sailors to find their way as they sail
across the seas.
OTHER USES
56. QUESTION AND
ANSWER PORTION
How do stars appear to move in the
night sky?
What is the closest star to Earth?
Why do stars have colors?
What are the imaginary group of
stars?
57. This constellation is prominent during
winter
It is commonly known as North Star
What is the brightest star?
It is a type of photograph that capture
the apparent motion of stars in the
night due to the rotation of the Earth.
Give 10 constellations
58. The Sun is also know as?
What is the name of our galaxy?
What is the largest constellation?
