Transcript Star ppt

STARS, CONSTELLATIONS
AND PLANETS
4th Grade Science
Earth Science
Unit IV: Stars and Solar Systems
S4E1 & S4E2
STARS
ACTIVATING VIDEO
http://www.bcsdk12.net/cms/lib01/GA01000598/Centricity/Domain/107/I%20a
m%20A%20Star%20The%20Stars%20Song%20by%20StoryBots.avi
I’m Star video
•If you went outside on a clear evening
and brought along a blanket and
were to lie down and look in the sky
what would you see?
WHAT IS A STAR?
• A star is a massive, bright, sphere of very hot gas
called plasma which is held together by its
own gravity.
• Stars radiate energy created from nuclear fusion,
which is a process that takes place in a star's core
and involves hydrogen fusing (burning) to
make helium.
HOW DO STARS FORM?
• Stars form when enough dust and gas clump together
because of gravitational forces. Nuclear reactions release
energy to keep the star hot. Planets form when smaller
amounts of dust and gas clump together because of
gravitational forces.
• Stable stars like the Sun change during their lifetime to form
other types of stars, such as red giants, white dwarfs,
neutron stars and black holes. The fate of a star depends
upon how much matter it contains.
STAR FACTS
• The nearest star to Earth is the Sun, which is classified as a G2 yellow
dwarf star.
• There are approximately 200-400 billion stars in our Milky Way Galaxy
alone.
• Each galaxy contains hundreds of billions of stars and there is
estimated to be over 100 billion galaxies in the universe. So the total
number of stars in the universe is mind boggling, estimated to be at
least 70 sextillion and possibly as high as 300 sextillion, that's
300,000,000,000,000,000,000,000!!!!!
• Stars are usually between 1 and 10 billion years old. Some stars may
even be close to the age of the observed Universe at nearly 13.8
billion years old.
WHAT MIGHT YOU SEE IN THE
NIGHT SKY?
• Astronomers classify stars according to their physical
characteristics. Characteristics used to classify stars
include color, temperature, size, composition, and
brightness.
• What does composition mean?
• One way scientists classify stars is by color. Star colors
range from blue, white, and yellow to orange and
red. The color of a star is a clue to its surface
temperature. Blue stars are the hottest, and red stars
are the coolest. Our sun is between the hottest and
the coolest stars.
• The brightness of a star depends upon both its size and its temperature. How
bright a star looks from Earth depends on both its distance from Earth and
how bright the star actually is.
• Distances on Earth’s surface are often measured in kilometers. However,
distances to the stars are so large that kilometers are not very practical units.
Astronomers use a unit called the light-year to measure distances between
the stars.
• A light-year is the distance that light travels in one year, about 9.5 million
million kilometers.
•The two most important
characteristics of stars are
temperature and absolute brightness.
STARS GROUPED BY SIZE
• Supergiants are the largest stars, and may have diameters several
hundred times the size of the Sun.
• Giants are more common than Supergiants, and have diameters 10 to
100 times as large as the Sun. Red Giants have cooler temperatures
than giants, and are thus less bright, but their size is still massive.
• Medium-size or dwarf stars are about as large as the sun.
• White dwarfs are small stars (smaller than the distance across Asia).
THE SUN IS A STAR!!!!
What do you see?
CONSTELLATIONS
HISTORY OF CONSTELLATIONS
• When ancient observers around the world looked up at the night sky, they
imagined that groups of stars formed pictures of people or animals. Today,
we call these imaginary patterns of stars constellations
When we talk about constellations, do
you know what they are?
• The first thing you need to know is that constellations are not
real!
• The constellations are totally imaginary things that poets,
farmers and astronomers have made up over the past 6,000
years (and probably even more!). The real purpose for the
constellations is to help us tell which stars are which, nothing
more. On a really dark night, you can see about 1000 to
1500 stars. Trying to tell which is which is hard. The
constellations help by breaking up the sky into more
managable bits. They are used as mnemonics, or memory
aids.
WHAT DO YOU SEE?
EXAMPLES OF CONSTELLATIONS
CONSTELLATIONS VS. GALAXIES VS
UNIVERSE
• These stars form a constellation, a group of stars that form an imaginary
picture in the sky.
• A galaxy is a huge system of gases, dust, and stars.
Galaxies contain billions of stars.
The universe is everything that exists in space.
COMPARE STARS TO PLANETS
What are some comparisons of planets and stars just by looking at this picture?
• Video link
• http://www.bcsdk12.net/cms/lib01/GA01000598/Centricity/Domain/107/Co
mparison%20of%20planets%20and%20stars.mov
PLANETS
• A solar system is a group of objects in space that orbit a star
in the center, plus the star itself. The sun is the star in the
center of our solar system. Everything else in the solar system
is small compared to the sun.
• Our solar system contains a variety of objects. These include
planets, “dwarf planA planet is a large object that revolves
around a star in a clear orbit. ets,” moons, and asteroids. A
“dwarf planet” also revolves around a star, but its path is not
clear of other objects. A moon is a smaller object that
revolves around a planet.
THE INNER PLANETS
• The inner planets are those closest to the sun. They
are Mercury, Venus, Earth, and Mars. These planets
are alike in many ways. They all have rocky surfaces
and are smaller than most of the outer planets.
THE OUTER PLANETS
• Beyond Mars, on the far side of the asteroid belt, are the
outer planets. They are Jupiter, Saturn, Uranus, and
Neptune.
• These four planets are huge and made mostly of gases.
They have no known solid surface. Their atmospheres blend
smoothly into the denser layers of their interiors, very deep
beneath the outer layers. For this reason, these planets are
often called the gas giants.
• In our solar system, there are eight planets. Often, scientists
group them as the inner planets and the outer planets.
THE EARTH AND ITS
MOTION
THINK QUESTION
What is the difference between
rotating and revolving?
• The changes of the seasons, as well as the changes of night
and day, occur because of the ways Earth moves.
• Earth moves in two ways. You have learned that Earth
rotates on its axis. It takes about 24 hours for Earth to make
one complete rotation.
• In addition to rotating on its axis, Earth revolves, or travels in
a path around the sun. An object’s path in space around
another object is its orbit. Earth’s orbit takes about 365 days,
or one year.
YOU MAY KNOW THAT EARTH IS DIVIDED INTO NORTHERN AND
SOUTHERN HEMISPHERES BY THE EQUATOR. THE EQUATOR IS AN
IMAGINARY LINE GOING ALL THE WAY AROUND EARTH HALFWAY
BETWEEN THE NORTH AND SOUTH POLES.
THINK QUESTION
•
Do we have summer because the Earth is
closer to the Sun during the summer?
• It’s the tilt of Earth’s axis that produces seasons.
• As Earth revolves, one part is tilted toward the sun.
That part of Earth takes in more energy from the sun
in the form of heat. The part that is tilted away from
the sun takes in less energy from the sun.
MOON PHASES
• The moon is a small planetlike body that revolves around Earth rather than
the sun. As Earth revolves around the sun, the moon revolves around Earth.
• The moon appears to shine, but the light you see is actually reflected light
from the sun. As the moon revolves around Earth, different amounts of its lit
surface can be seen. That’s why the moon seems to have different shapes,
or phases.
PHASES OF THE MOON
During the first half of the moon’s cycle, the amount of the
lit side of the moon seen from Earth waxes, or increases.
During the second half of the moon’s cycle, the amount of
the lit side of the moon seen from Earth wanes, or
decreases. Then the cycle begins again.