Script for
Searching the Universe
This slideshow is designed for all grades. Information depends on audience. Main focus is to get students to observe the night time sky and to think of the patterns in the sky.
Slide 1.
Searching the Universe
·
This
is a picture of a galaxy which resembles what our Milky Way galaxy looks like.
We cannot take a picture of our galaxy, as we cannot get far enough away.
What was named first the candy bar or our galaxy?
Of course, the galaxy.
·
Our
galaxy is a spiral galaxy with center of many stars (nucleus) and stars that are
farther away (where our solar system resides), in one of the “arms.”
·
Use the fiber optics
(UFO looking thing), show them that the points of light represent stars.
In the Universe stars are concentrated in galaxies…. So take a bunch of
the fibers and put them together.
These represent how stars are held together by gravity.
There are stars,
galaxies, globular clusters, and quasars that are part of the
Universe beyond our Solar System. There are different types of individual
stars representing different parts of their life. For instance, a planetary
nebulae has a round shape with shells of gas being thrown from stars that
are ending their lives. A Herbig -Haro object is a young star that is ejecting
jets of material back into space. Many of these objects are light years apart. A
light year is the distance light travels in one year, or about 6 trillion
miles.
But we also see
objects that are within our Solar System like planets, comets,
asteroids and meteoroids.
·
When the Sun is warming
the Earth and you look up into the blue sky, what do you see? You might see a
few clouds moving lazily across the sky. But what would happen if the light of
the Sun disappeared? You would see stars and other components of the Universe.
Ask the students what do they see.
Lights…. and are the lights moving…. yes
(even airplane lights)
·
The light is coming in two ways… either the stars are generating light or we see
reflected light.
·
Hydrogen and Helium. Plasma is the
most abundant state of matter in the Universe.
Plasma a state of matter and most abundant
an ionized gas consisting of positive ions and free electrons in proportions
resulting in more or less no overall electric charge, typically at low pressures
(as in the upper atmosphere and in fluorescent lamps) or at very high
temperatures (as in stars and nuclear fusion reactors).
·
Revolution and Rotation.
Point out in diagram…
everything even the Sun rotates on an axis and everything seems to revolve
around something else. Gravitation
attraction causes this movement.
·
The Earth is always
rotating, spinning eastward. We do not sense this motion, however, because
everything else on the Earth’s surface is moving as well. There is no
independent frame of reference for observing rotation. Viewed from space,
however, the Earth is clearly spinning. A point on Earth takes 24 hours to
complete one rotation and come back to its starting point. The Earth spins
completely once in 24 hours or in 1 day. The axis is the internal line around
which the Earth rotates. The axis is tilted 23.5o from an imaginary
vertical line drawn through the Earth.The Earth is spinning on its axis, it is
also revolving around the Sun.
·
The Moon revolves
eastward around the Earth, taking 29.5 days to complete one orbit. The phases of
the Moon are complex when fully explained; at this point the students need to be
able to distinguish between a full Moon and a new Moon. A full Moon is when we
see the complete Moon from the surface of the Earth. This takes place when the
Moon is in the outer part of its orbit, and sunlight and reflected sunlight
(from the Earth) shine on it. During a new Moon, we cannot see any of the Moon
in the night sky. This occurs when the Moon is between the Earth and the Sun.
Slide
4.
Where is the light coming from?
·
Venus and Moon
this is reflected light, planets and moons do not generate their own
light
·
stars within galaxies
generate their own light… however when the galaxy is far away it might be
perceived as just one point of light to our eyes
Stars are different
distances from the Earth. This means we see the relative brightness or magnitude
of stars, not their real, or absolute magnitude. Astronomers call a star's
brightness its magnitude. The brightness as we see it on Earth is termed
apparent magnitude, while a star’s actual light output is called absolute
magnitude. For instance, our Sun has an apparent magnitude of -26.8 (very
bright) but an absolute of 4.8 (not bright). The derivation of these numbers is
not important in the third grade. The main point is that from Earth, we see only
the apparent brightness of the stars.
Slide 5.
What state of matter is found in the Universe?
·
Chemical
composition. When stars form in the present Milky Way galaxy they are composed
of about 71% hydrogen and 27% helium, as measured by mass, with a
small fraction of heavier elements.
·
Stars
come in huge range of different sizes. Neutron stars can be just 20 to 40 km
in diameter, whereas white dwarf can be very similar in size to Earth's. The
largest supergiants, on the other hand, can be more than 1500 times larger than
our Sun.
Slide 6.
There are many stars that have many shapes, sizes and colors
·
Stars appear to the
naked eye as spiky, twinkling lights or scintillation, especially at
night. The stars near the horizon also seem to flash and change color.
The twinkling and flashing effects are not due to the stars themselves but to
the Earth's atmosphere. Turbulent air currents cause the star's light to
dance around. The spikiness of star images is due to optical effects in the
observer's eyes. In reality, stars are spheres of gas similar to our own Sun.
Stars are held together by gravity.
·
Astronomers classify
stars in two ways. The first classification uses the star’s spectrum, the
color(s) of light that the star emits. A star’s spectrum is caused by the
temperature in the outer layers of the star. If the star is hot, it looks blue.
If it is cool, it looks red. The chart below shows the basic classification of
stars by spectral type. The temperatures for stars are measured in a unit
called, Kelvin. The temperature of a star in degrees Centigrade is equal
to its temperature in degrees Kelvin plus 273. In other words, real hot!
The Sun is a star. A
self-luminous sphere of gas and plasma that is held together by its own gravity,
and energized by nuclear reactions in its interior. The Sun has a four part
structure. The outermost layer is the corona, the Sun’s outer atmosphere. This
is a zone of super hot (temperatures vary, but range to millions of degrees
centigrade). The corona is periodically hit by shock waves released from the
Sun’s surface. Combined with its high temperature, this produces the solar wind,
a stream of subatomic particles that are "blown" or projected outward from the
Sun. The solar wind moves at speeds of over 400 km/sec (893,000 mph) and extends
well beyond the edge of the Solar System. Below the corona is a thin layer
called the chromosphere, which is less than 200 kilometers thick. This lower
part of the Sun’s atmosphere is composed mainly of hydrogen, and has an average
temperature of 5,000 Co. Chromosphere means "color sphere", because
when visible, this layer appears as a thin red crescent. The corona and
chromosphere are visible only during solar eclipses, when the remainder of the
Sun is hidden.
The visible surface
layer of the Sun is the photosphere, which is a layer of plasma about 300
kilometers thick. It is composed of 94% hydrogen and 6% helium. Viewed from
Earth, the photosphere has a grainy or spotted texture of light and dark
patches. This texture is caused by temperature variations in the photosphere:
the hot areas look brighter than the dark areas. These variations are caused by
circulation within the photosphere. The photosphere also has a magnetic field,
but unlike the magnetic fields of the planets, the lines of magnetic force here
wind around the Sun’s rotational axis, following lines of latitude rather than
lines of longitude. The reasons for this are not fully understood.
The remainder of the
Sun is its interior or core. The core consists largely of plasma composed of the
nuclei of hydrogen atoms. Deep within the core, the temperature is approximately
15 million degrees centigrade. It has been calculated that a pinhead of material
at core temperature would be lethal to a person who was 160 kilometers away!.
The pressure in the
core is also enormous. It is calculated to be 70 trillion grams per square
centimeter. The main feature of the Sun, of course, is that it radiates energy.
This is caused by nuclear fusion. At core pressures and temperatures, four
hydrogen nuclei undergo a series of fusion reactions, which eventually produce
one heavier atom of helium. This process releases a huge amount of energy. This
energy radiates into space, mostly as infrared and visible light. Other
wavelengths, including ultraviolet radiation and gamma rays, are also emitted.
Fusion reactions happen relatively rarely in the Sun, so it burns its hydrogen
"fuel" fairly slowly. The Sun has been undergoing fusion for around 5 billion
years, and should last another 2 billion years before it depletes is hydrogen.
Slide 7.
·
Color of a star can help us determine how hot a star is.
Hertzsprung and Russell… found out about the stars
(go over hot and cool stars)… make sure they can read the data chart.
·
Have students figure out what color is for cool stars versus hot.
Also since our Sun is yellow, have them figure out the temperature of our
Sun.
A two-dimensional graph, devised independently by Ejnar Hertzsprung (1873–1967)
and Henry Norris Russell (1877–1957), in which the absolute magnitudes of stars
are plotted against their spectral types. Stars are found to occupy only certain
regions of such a diagram.
Slide 8. Hubble Telescope
·
The Hubble Telescope
revolutionized our understanding of the Universe.
It allowed astronomers to see worlds we never saw before.
It was launched in 1990 and still sending pictures.
·
The Hubble Space
Telescope is a large machine. It is about 44 feet (13.1 meters) in length,
roughly the same size as a school bus. The Hubble is heavy; it weighs 12 tons
(11,600 kilograms). The Hubble looks like a fat silver tube, almost like a
number of cans stacked on top of each other. Forty foot long solar power
panels sprout form each side of the telescope. These provide all the power
the Hubble needs to operate.
·
Inside, the Hubble
contains one large mirror which 8 feet (2.4 meters) in diameter. When the Hubble
is aimed at an astronomical object, such as a galaxy, radiation from the galaxy
shine into the telescope and onto the mirror. From here the radiation is
analyzed by several scientific instruments.
None of these
instruments take pictures like the photographic cameras we are used to. Instead,
they take digital images, which are stored as files in a computer and then
transmitted to Earth. No person ever really "looks through" the Hubble Space
Telescope.
The Hubble is a
satellite. It orbits the Earth very quickly, completing one revolution
every 97 minutes. This means the Hubble moves a speed of about 5 miles per
second, or 18,000 miles per hour! When the Hubble observes distant stars and
galaxies, it must stay pointed in the same direction for hours at a time. In
addition, it must remain stable while fighting the effects of the Earth’s
gravity and the solar wind.
How does the Hubble
remain stable? While the telescope is making observations, computer-controlled
machines called gyroscopes keep it stable and pointed in the right
direction. The Hubble requires very precise pointing to take good pictures.
The operation of the
Hubble is controlled by scientists and engineers at the Space Telescope Science
Institute, located near Baltimore, Maryland. The scientists, who are from all
over the world, decide where they want the telescope to look, and what kind of
information they want to collect. The engineers are responsible for giving
commands to the satellite and making sure it stays in working order.
Edwin Hubble, a well
known astronomer, classified galaxies into four major groups, ellipsoidal,
spiral, and irregular, based on their shape and origin. The core of a galaxy,
where most of its stars are concentrated, is called the galaxy’s nucleus. The
spiral arms of spiral galaxies are concentrations of stars that seem to spin
from the nucleus.
Slide 9.
A Star is Born
·
Stars are born and die
within galaxies. A star is born when atoms of
light elements are squeezed under enough pressure for their nuclei to undergo
fusion. All stars are the result of a balance of forces: the force of
gravity compresses atoms in interstellar gas until the fusion reactions begin
·
A star is a ball
of hot gas held together by its own gravity. Gravity also causes stars to
undergo nuclear fusion within their interior. The energy release causes the star
to shine. The energy of fusion balances the star’s gravity, preventing it from
collapsing. However, when a star’s internal energy dwindles, the star may fade
from sight into a white dwarf star, or a neutron star, an
extremely high density object composed of 99% neutrons. Neutron stars are
probably remnants from supernova explosions.
·
This famous picture is of
a “star nursery.” Pillars of helium
and hydrogen create new stars. This
is a nebula.
·
Gravitational forces
create these pillars.
Slide 10.
And a star can die
·
The most massive stars quickly exhaust their fuel supply and
explode in core-collapse supernovae, some of the most energetic explosions in
the universe. A supernova’s radiation can easily (if only briefly) outshine the
rest of its host galaxy.
·
The remnant stellar core will form a
neutron star or a black hole, depending
on how much mass remains. If the core contains between 1.44 and 3 solar masses,
that mass will crush into a volume just 10 to 15 miles wide before a quantum
mechanical effect known as
neutron degeneracy pressure prevents total collapse. The exact upper
limit on a neutron star mass isn’t known, but around 3 solar masses, not even
neutron degeneracy pressure can combat gravity’s inward crush, and the core
collapses to form a black hole.
Black Holes
Astronomers have found what appears to be a black hole 25 to 40
times the mass of our Sun, a weight class not previously known to exist.
Black holes can't be seen, because any light that enters them is
trapped. So to find black holes, scientists look for intense radiation from
around them as well as their gravitational effects on nearby gas and stars.
Black holes come in two distinct varieties, scientists know. A
stellar black hole results from the collapse of a single, massive star and is
typically a few times the mass of the Sun. Supermassive black holes anchor the
centers of many galaxies and can harbor millions or billions of solar masses.
Slide 11.
There are other objects in the Universe
Slide 12. Milky Way
Our galaxy, the Milky
Way is actually a giant, as its mass is probably between 750 billion and one
trillion solar masses, and its diameter is about 100,000 light years. Radio
astronomical investigations of the distribution of hydrogen clouds have revealed
that the Milky Way is a spiral galaxy of Hubble type Sb or Sc. Therefore, out
galaxy has both a pronounced disk component exhibiting a spiral structure, and a
prominent nuclear region which is part of a notable bulge/halo component.
The Milky Way Galaxy
belongs to the Local Group, a smaller group of 3 large and over 30 small
galaxies, and is the second largest (after the Andromeda Galaxy M31) but perhaps
the most massive member of this group. M31, at about 2.9 million light years, is
the nearest large galaxy, but a number of faint galaxies are much closer: Many
of the dwarf Local Group members are satellites or companions of the Milky Way.
The two closest neighbors, both already mentioned, have only recently been
discovered: The nearest of all, discovered in 2003, is an already almost
disrupted dwarf galaxy, the Canis Major Dwarf, the nucleus of which is about
25,000 light-years away from us and about 45,000 light-years from the Galactic
Center. Second comes SagDEG at about 88,000 light years from us and some 50,000
light years from the Galactic Center. These two dwarfs are currently in close
encounters with our Galaxy and in sections of their orbits situated well within
the volume ocupied by our Milky Way. They are followed in distance by the more
conspicuous Large and Small Magellanic Cloud, at 179,000 and 210,000 light
years, respectively.
The spiral arms of our
Milky Way contain interstellar matter, diffuse nebulae, and young stars and open
star clusters emerging from this matter. On the other hand, the bulge component
consists of old stars and contains the globular star clusters; our galaxy has
probably about 200 globulars, of which we know about 150. These globular
clusters are strongly concentrated toward the Galactic Center: From their
apparent distribution in the sky, Harlow Shapley has concluded that this center
of the Milky Way lies at a considerable distance (which he overestimated by
factors) in the direction of Sagittarius and not rather close to us, as had been
thought previously.
NOTE:
Open one side of the “star” model.
Leave it open, and then after Cookie break you can take the “star” out.
Put it into the cup and then staple it closed.
It is really a bouncy ball, and the longer it has time to dry it will
bounce better. Tell the students
when they go home after school.
Slide 13.
Play constellation song.
Slide 14.
Constellations show a pattern
Slide 15.
·
Most of the stars in a
constellation have no real connection with each other at all. They may all lie
at vastly different distances from Earth, and simply form a pattern by chance.
The main stars in each constellation are labeled with a letter of the Greek
alphabet, the brightest star usually being termed alpha.
·
The brightness of a star
is called its magnitude. Stars have different brightness for two reasons.
First, stars radiate different amounts of light; more energetic stars are the
brightest . Second, stars lie at vastly differing distances from the Earth. A
small star that is close to the Earth can appear brighter than a large star that
is far away from the Earth.
·
There is
88 constellations that astronomers use to
look at a direction in space.
Constellations can
help make the heavens come alike for the observer. Each image in the sky helps
to chart an area so it is easy to identify. A constellation refers to an entire
sector, but there are many patterns that can be identified. An asterism
is a pattern of stars that does not form the main or full pattern of an
"official" constellation. For example, in the northern hemisphere the Big Dipper
is only an asterism of the official Ursa Major (the Great Bear). Ursa Minor, the
Little Bear constellation is visible in the northern hemisphere all year long.
Polaris, the North Star can be found at the end of the asterism, the Little
Dipper. Ursa Minor was created in the 6th century B.C. as a
navigational aid for sailors. Can you find the Little Dipper in the figure to
the right?
Slide 16.
Many cultures developed ways to create a calendar using alignments.
There are some of the famous ones that still remmants remain.
Slide 17.
Slide 18.
Constellations of the Zodiac
This animation shows the procession of
the constellations within the Zodiac and how they move around the sky
Side 19.