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Astronomy
Since the beginning of time,
astronomers have attempted to study
the movements of the stars and
planets.
Long, long ago…
• Ptolemy thought the
Earth was the center of
the universe.
• This was considered
the geocentric way of
thought.
• Ptolemy also thought
that we were not
moving.
Helio---what?
• In 1500 AD,
Copernicus said the
Sun was the center of
the universe
(heliocentric viewpoint).
• Copernicus also said
that the planets were
orbiting in a circular
pattern.
• In 1609, Kepler proved
Copernicus was wrong
about the orbits. The
planets orbit in an
elliptical pattern instead
of a circular pattern.
• Galileo proved that
Copernicus was right
about the Sun being the
center of the our solar
system.
• Galileo created a
telescope that allowed
him to prove these
theories.
Ptolemy’s geocentric view…
• The Church supported
this view and did not
support future views
of Copernicus, Kepler,
and Galileo.
• Galileo was even put
under house arrest for
his findings.
Sunspots and Moons
• Galileo observed the Sun through his telescope and saw
that the Sun had dark patches on it that we now call
sunspots (he eventually went blind, perhaps from damage
suffered by looking at the Sun with his telescope). He saw
these spots moving, so he realized that the Sun must be
rotating. He thought that if the Sun was moving, we
probably were rotating on an axis.
• Galileo observed 4 points of light that changed their
positions with time around the planet Jupiter. He
concluded that these were objects in orbit around Jupiter.
Indeed, they were the 4 brightest moons of Jupiter, which
are now commonly called the Galilean moons (Galileo
himself called them the “Medician Stars”).
The Phases of Venus
• Galileo used his telescope to show that Venus went
through a complete set of phases, just like the Moon. This
was probably the most important observation that Galileo
made, because this proved that Venus was revolving
around the Sun.
• In the old system of thinking, Venus should always be in
crescent phase as viewed from the Earth. In the Copernican
system, Venus should exhibit a complete set of phases as
viewed from the Earth because it is illuminated from the
center of its orbit.
What else Galileo saw…
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Galileo saw that the planets were disks, not points of
light, as seen through the telescope.
He saw that the great "cloud" called the Milky Way
(which we now know to be the disk of our spiral galaxy)
was composed of enormous numbers of stars that had
not been seen before.
He observed that the planet Saturn had "ears". We now
know that Galileo was observing the rings of Saturn, but
his telescope was not good enough to show them as
more than extensions on either side of the planet.
Galileo saw that the Moon was not smooth, as had been
assumed, but was covered by mountains and craters.
Stuff in space…
• Asteroids are chunks of
rock and metal that are
commonly found in a
belt between Mars and
Jupiter.
• Meteoroids are smaller
than asteroids.
• What do you call a
meteoroid that falls to
the Earth?
• It is a meteorite.
• Comets are frozen
balls of gas, rock, and
ice.
• Why do comets have a
tail when they are near
the Sun? They are
melting.
How many planets have we
found?
• This latest discovery (May
2015) brings the
confirmed count of planets
outside our solar system to
1,021.
• Most of these planets are
smaller than Neptune,
which is almost four times
the size of Earth.
• Launched in March
2009, Kepler is the
first NASA mission to
find potentially
habitable Earth-size
planets. Discoveries
include more than
4,600 planet
candidates.
Kepler is actually a special type of
telescope housed on a spacecraft…
Planets in our system:
• My very excellent mother just served us nachos.
• Name the planets of our galaxy, in order.
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Dwarf planets include: Ceres,
Eris, Haumea, Makemake, and
Pluto
Eris is just slightly larger
than Pluto and takes 557
years to make a very skewed
orbit of the Sun. Ceres is
between Mars and Jupiter.
Two other dwarf planets
include Haumea and
Makemake.
The new definition of
"planet": A body that circles
the sun without being some
other object's satellite, is
large enough to be rounded
by its own gravity (but not
so big that it begins to
undergo nuclear fusion, like
a star) and has "cleared its
neighborhood" of most other
orbiting bodies.
This artist's concept shows dwarf
planets Eris, Pluto and Ceres in
comparison to Earth. Pluto's moon
Charon also is shown.
Galileo mission
• http://solarsystem.nasa.gov/galileo/
Go to sizes of planets…
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Astronomers are searching for a planet similar to Earth, with water (so that it could
support life).
Two methods to detect planets are commonly used: the wobble method and the transit
method.
The wobble method is based on planets that are as massive as Jupiter. Massive planets
pull on their stars, making them wobble like a large dog who walks its owner. You can
often tell that a dog is walking it’s owner without seeing the dog, as you watch the
person being pulled this way and that. This is how scientists detect massive planet that
are far away. They look for stars that are wobbling. The less massive planets do not
produce such a visible pull on their stars, however, so another method is used.
The transit method looks for stars that are smaller than our Sun (red dwarfs). As a
smaller (less massive) planet passes in front of the star, it causes a brief dimness of the
star due to the eclipse or transit of the planet. We can detect a less massive planet
passing in front of a less massive star from far away. NASA has launched the Kepler
telescope just to search for transit planets (launched in 2009).
http://www.kepler.arc.nasa.gov/http://www.kepler.arc.nasa.gov/
Rotate means to spin on the axis.
• A planet’s rotation
time may vary, so the
length of a day will
vary too.
• Venus’ rotation time is
much slower than
ours, so the days are
longer there.
Seasons are caused by…?
• Seasons are caused by
the Earth’s tilt on its
axis.
• March 21 marks our
Vernal Equinox.
• June 21 is the beginning
of our Summer Solstice
(most daylight hours in
Northern Hemisphere).
• Sept 23 marks our
Autumnal Equinox and
Dec 22 marks our Winter
Solstice.
So, are the seasons the
same in both the Northern
and Southern Hemispheres?
No seasons???
• Mercury, Venus,and Jupiter
have no axial tilt, so they
also have no seasons.
• Mars has colder winters and
warmer summers than Earth.
• Distance from the Sun can
also determine seasons.
(Pluto has cold and colder
weather; Uranus has years
of day and years of night
due to its tilt.
How long is a day on Venus?
• Try going to Venus for
a day; you could get
everything and more
done in one day!
• One day on Venus is
equal to 243 Earth
days.
• Why?
What causes a year?
• A revolution is the
movement of a planet
all the way around the
Sun.
Phases of the moon
• The Sun’s light is
reflected off the moon in
phases due to the moon’s
rotation.
• Waxing phases are the
ones you see as the moon
goes to the Full Moon
phase.
• Waning phases are the
ones you see as the moon
goes to the New Moon
phase.
• http://starchild.gsfc.nasa.gov/docs/StarChild
/solar_system_level2/moonlight.html
• WAX ON (karate kid) means there is more
(more wax); to wane is to get smaller.
What an awesome wave, dude!
• The gravitational pull
of the moon and the
Earth, and the
difference between
those two forces cause
the tides.
• The net force can be
seen in the diagram,
which causes the
squashed appearance.
I can’t see you…
In a lunar eclipse, what can’t you see?
• The Earth blocks our view of the
moon.
• The next total lunar eclipse that will
be visible from North America will
be on September 28, 2015.
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Eclipses in 2016
March 9: Total solar eclipse
March 23: Penumbral lunar eclipse
September 1: Annular solar eclipse
September 16: penumbral lunar eclipse
.
How far is it to the closest star?
• One astronomical unit
is 93,000,000 miles.
• This is the distance
from the Earth to the
Sun.
How far is that star…?
• One light year is about 5.8
trillion miles.
• A light year is the distance
that light can travel in a
vacuum in a year.
• What is a vacuum?
• Proxima Centauri is the
next closest star to Earth.
• Four point two light years
away means that you are
seeing the way it looked
4.2 light years ago. (5.8
trillion times 4.2).
(one trillion = 1 one and
12 zeros)
From baby star to old star…
• Stars have stages of
growth just like we do.
• Newborn stars are
called Nebula.
• Being a star is all
about the race between
gravity and burning of
gases (hydrogen and
helium).
You’re a protostar!
• The second stage of a
star is called a
protostar.
• During this stage, the
pressure causes the
temperature to rise to
27 million degrees F,
high enough for fusion
to begin.
Main sequence star
• In the third stage, the
hydrogen of the star is
turned into helium in a
process called fusion.
• This gives the star energy.
• As the hydrogen runs out,
so does the star.
• This takes millions or
billions of years, depending
on the mass of the star.
• Our Sun is in this stage.
What’s your mass anyway?
• Low mass stars will
become white dwarfs.
Our Sun will become a
white dwarf.
• Medium mass stars will
become red giants,
planetary nebulas, and
then white dwarfs.
• High mass stars will
become supergiants,
supernovas, and black
holes or neutron stars.
Go to star sizes…
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Twinkle, twinkle little star
You’re a ball of gas that’s very far.
Thirty two light years in the sky.
Ten parsecs (32.6 light years) which is really high.
Helium, carbon, and hy-dro-gen,
Fuse to make our starry friend.
When it enters supernova stage, it explodes with
burst of rays.
• And if the star’s mass is big and bold, it will
become a black hole!
How can we find a star?
• Stars give off
electromagnetic
radiation---radio
waves, infrared rays,
visible light, UV
waves, x rays and
gamma rays.
• Astronomers can now
detect a type of star by
the type of radiation it
gives off.
Radio telescopes help
astronomers detect waves
from space.
GBT in Pocahontas County, WV
I can’t see you…
• In a solar eclipse, the
moon blocks our view
of the Sun. Our next
partial solar eclipse
will be on Oct 23,
2014.
Welcome to my galaxy…
• Edwin Hubble was an
astronomer in the 1920’s
who discovered that
galaxies are moving and
that the universe is
expanding.
• The Hubble telescope is
used in space today, and
will be replaced by the
Webb telescope in the
near future.
Galaxies are classified
by various shapes.
• They may be spirals,
barred spirals,
lenticular, ellipticals or
irregular clusters.
The Milky Way is a spiral
galaxy.
• Our next closest
galaxy is Andromeda,
yet it is twice the size
of our galaxy.
• There are billions of
galaxies in space; each
galaxy contains
hundreds of thousands
of stars.
Galaxies are never alone.
• They are usually
connected with other
galaxies by gravity.
• Clusters of galaxies
can be as small as two
galaxies orbiting each
other.
• There is no end to the
amount of galaxies in
a cluster.
A view from within the
Milky Way Galaxy.
Our universe…
• The Milky Way galaxy
is part of a cluster called
the local group, which
includes 40 different
galaxies.
• The local group is part
of a super cluster called
the Virgo Cluster, which
contains over 2,000
galaxies.
The International Space Station
• The station, built by
5 different groups, is
about 361 feet
across (a football
field).
http://www.youtube.
com/watch?v=0Oxo
EnzAhFg&list=PLiu
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