STARS

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STARS
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Instructions

• Students will underline the portions of the
  PowerPoint that are underlined.

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A Nuclear Furnace

• 1. A star is like a gigantic nuclear furnace.
• 2. The nuclear reactions inside convert hydrogen
  into helium by means of a process known as
  fusion.
• 3. It is this nuclear reaction that gives a star
  its energy.

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Classifying Stars

• Scientists classify stars by
• Temperature
• Brightness

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Star Temperature

• 1. The color of a star tells us about its
  temperature.
• Blue stars are the hottest, 7500C- 30,000C.
• Red stars are the coolest, less than 3500C.
• Our sun is yellow in color, in the middle of the
  temperature scale, from 5000C-7500C.

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Betelgeuse- Red Star- Coolest
Rigel- Blue Star-Hottest
CONSTELLATION ORION
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Brightness or Magnitude

• 1. Stars are also classified by their brightness.
• 2. The brightness of a star as seen from Earth is
  called apparent magnitude.
• 3. The actual brightness of a star is called
  absolute magnitude.
• Example The SUN has an absolute magnitude of 4.8
  when compared to the other stars. The SUN has an
  apparent magnitude of -26.8 because it is so
  close.

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Another Example of absolute and apparent
magnitude.
A
B
Which light is brighter, A or B?
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• Light A is brighter than light B.
• We see the apparent magnitude of the lights (how
  they look to us)
• If lights A and B were next to each other they
  would look the same because the two lights are
  exactly the same.
• Their absolute magnitude is the same.
• Distance makes them look different. The same is
  true for stars.
• Two stars could be the same brightness but their
  distance from us makes their brightness
  different.

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H-R Diagram
Brighter
1. The H-R Diagram shows us color, size,
temperature, absolute magnitude and the life
cycle of stars.
Dimmer
Hotter
Cooler
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Constellations

• A constellation is a group of stars that appear
  to form patterns and images in the sky.
• The stars in a constellation are often vastly
  distant from each other, but they appear close to
  each other from the perspective of Earth.
• There are 88 constellations.

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Betelgeuse- Red Star- Coolest
Rigel- Blue Star-Hottest
CONSTELLATION ORION
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Constellations

• The 88 official constellations defined by the IAU
  are mostly based upon those of the ancient Greek
  tradition, passed down through the Middle Ages,
  which includes the 'signs of the zodiac,' twelve
  constellations through which the sun passes and
  which thus have had special cultural
  significance.
• The rest consist of constellations defined in the
  early modern era by astronomers who studied the
  southern hemisphere's skies, which were invisible
  to the Greeks.

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Zodiac Signs-Whats your Sign?

• Leo, Virgo, Libra, Scorpius, Sagittarius,
  Capricornus, Aquarius, Pisces, Aries, Taurus,
  Gemini, Cancer

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CapricornusThe Sea Goat

• This zodiacal constellation, like Pisces, depicts
  the result of the sudden appearance of the
  earthborn giant Typhoeus. Bacchus was feasting on
  the banks of the Nile at the time, and jumped
  into the river. The part of him that was below
  water was transformed into a fish, while his
  upper body became that of a goat. From this point
  of view, he saw that Typhoeus was attempting to
  tear Jupiter into pieces he blew a shrill note
  on his pipes, and Typhoeus fled. Jupiter then
  placed the new shape of Bacchus in the heavens
  out of thanks for the rescue.
• Capricornus has therefore from antiquity been
  represented by a figure with the head and body of
  a goat and the tail of a fish. It may be seen
  between Aquarius and Sagittarius low on the
  southern horizon.

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AquariusThe Water Carrier

• The water carrier represented by the zodiacal
  constellation Aquarius is Ganymede, a beautiful
  Phrygian youth. Ganymede was the son of Tros,
  king of Troy (according to Lucian, he was also
  son of Dardanus). While tending his father's
  flocks on Mount Ida, Ganymede was spotted by
  Jupiter. The king of gods became enamored of the
  boy and flew down to the mountain in the form of
  a large bird, whisking Ganymede away to the
  heavens. Ever since, the boy has served as
  cupbearer to the gods. Ovid has Orpheus sing the
  tale

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• "The king of the gods was once fired with love
  for Phrygian Ganymede, and when that happened
  Jupiter found another shape preferable to his
  own. Wishing to turn himself into a bird, he none
  the less scorned to change into any save that
  which can carry his thunderbolts. Then without
  delay, beating the air on borrowed pinions, he
  snatched away the shepherd of Ilium, who even now
  mixes the winecups, and supplies Jove with
  nectar, to the annoyance of Juno" (Metamorphoses
  X 154-160).Aquarius is a summer constellation in
  the northern hemisphere, found near Pisces and
  Cetus. It is especially notable as the radiant
  for four meteor showers, the largest of which is
  the Delta Aquarid meteor shower in late July and
  early August.

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Most Visible Constellations

• Orion-The Great Hunter

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Follow Orions Belt to Sirius, the brightest star
in the sky.
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Ursa Major- The Big Bear
The Big Dipper

• Ursa Major, the Greater Bear
• Zeus fell in love with Callisto, daughter of
  Lycaon (see under Lupus) and by her had a son,
  Arcas. In order to spare Callisto from the wrath
  of Hera, Zeus changed her into a bear to hide her
  identity

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The Story of the Big Bear

• In ancient times, when the moonths were the
  annual calendar, people studied astronomy to help
  them know when to plant and when to harvest. They
  knew when the rivers were likely to
  overflow...the Egyptians noted that the cycles of
  the Dog Star, Sirius, coincided with the rise and
  fall of the Nile River. They could accurately
  predict the Nile floods. Some of the Native
  American cultures noted that when the Big
  Dipper...they could see Ursa Major, the Great
  Bear...dipped low in the western sky, the leaves
  of the trees would turn red. Fall was here.
• .

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• The story goes that three hunters were trailing
  the bear. The hunters were the three stars that
  we see as the handle of the Big Dipper. One of
  the hunters had shot the bear in the side, but
  the wound wasn't serious enough to stop the bear.
  The middle hunter carried a pot on his shoulder
  to cook the bear meat in, but the hunters never
  got close enough to kill the bear. He went
  crashing through the forests of the night, always
  managing to keep the same distance ahead of the
  three hunters. At the end of summer, the bear and
  the hunters grew tired, and they dipped lower and
  lower toward the horizon. When the bear got very
  close to the horizon, close enough for blood to
  drip from the wound in his side onto the trees,
  the people noticed that the leaves turned red. It
  was time to harvest and finish preparation for
  winter.

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The Big Dipper

• The Big Dipper and Polaris play an important part
  in the story of the Underground Railroad which
  helped slaves escape their captivity in the
  southern states of the United States before the
  Civil War by fleeing north to Canada.
• The folk song "Follow the Drinking Gourd"
  (another name for the Big Dipper) was a coded
  song that gave directions on the escape route
  from Alabama and Mississippi. While traveling on
  their long escape journey, they could always tell
  which way was north by the location of Polaris
  which they could find by the pointer stars.

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Ursa Minor-The Little Bear

• Ursa Minor, the Lesser Bear
• Hera, discovering the tryst Zeus had had with
  Callisto (see Ursa Major), convinced Arcas to
  hunt after his mother, who had been changed into
  a bear by Zeus. To protect Callisto, Zeus changed
  Arcas into a bear and carried them both by their
  tails to the heavens, where they became
  constellations. Annoyed at this honor, Hera
  convinced Poseidon not to allow the bears to
  bathe in the sea. For this reason, Ursa Major and
  Ursa Minor never sink below the horizon.
• Vela, the Sails

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Create a constellation based on the letters in
your name

• Complete grid using the letters of your name.
• Transfer points to second grid.
• Create a shape with the letters and create a
  story that explains why your constellation is in
  the sky. Name your constellation after yourself
  or after the shape.
• Cut out your constellation and glue to
  construction paper.
• Write your story and the paper provided and glue
  to bottom of paper.
• Due Friday, 2/6/09

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Life Cycle of our Sun

• Stellar Nebula
• Protostar
• Main Sequence
• Red Giant
• Planetary Nebula
• White Dwarf
• Black Dwarf

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Life Cycle of a Massive Star

• Stellar Nebula
• Protostar
• Blue Giant
• Red Supergiant
• Supernova
• Neutron Star
• (Pulsar)
• OR
• 7. Black Hole

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Life Cycle of A Star

• 1. Stars begin their lives as clouds of dust and
  gas called a stellar nebula.

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A Protostar

• The gravity of a passing star or the shock wave
  from a nearby supernova may cause the nebula to
  contract.
• 1. Matter in the gas cloud will begin to come
  together into a dense region called a protostar.
• 2. As the protostar continues to condense, it
  heats up.
• 3. Eventually, it reaches a critical mass and
  nuclear fusion begins.
• 4. This begins the main sequence phase of the
  star. Our Sun is a main sequence star.

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PROTOSTAR
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Main Sequence Stars

• 1. The life span of a star depends on its size.
• 2. Very massive stars will become blue giants
  during their main sequence.
• Their main sequence may last only a few hundred
  thousand years.
• 3. Smaller stars, like the Sun, will burn for
  several billion years during their main sequence
  stage.
• 4. Our Sun is in its main sequence.

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The main sequence is the longest part of a stars
life
Average sized star like our Sun during main
sequence.
Massive star larger than our Sun during main
sequence
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Red Giant and Red Supergiant

• 1. Eventually, the star's fuel will begin to run
  out.
• 2. Our Sun will expand into what is known as a
  red giant.
• 3. Massive stars will become red supergiants.
• 4. This phase will last until the star exhausts
  its remaining fuel.
• 5. At this point, the star will collapse.

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Our Sun

• 1. Most average stars will blow away their outer
  atmospheres to form a planetary nebula.
• 2. Their cores will remain behind and burn as a
  white dwarf until they cool down.
• 3. What will be left is a dark ball of matter
  known as a black dwarf.

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Planetary Nebula
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White Dwarf
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Massive Stars

• 1. If the star is massive enough, the collapse
  will trigger a violent explosion known as a
  supernova.
• 2. If the remaining mass of the star is about 1.4
  times that of our Sun, it will collapse further
  to become a neutron star.
• 3. If the remaining mass of the star is more than
  about three times that of the Sun, it will
  collapse and what is left behind is an intense
  region of gravity called a black hole.

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Massive Stars (Larger than our Sun)
Become Red Supergiants.
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Red Supergiant becomes Supernova in a giant
explosion,
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OR It becomes a Black Hole
This is an illustration, not an actual black
hole!!
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Supernova Becomes a Neutron Star
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Life Cycle of our Sun

• Stellar Nebula
• Protostar
• Main Sequence
• Red Giant
• Planetary Nebula
• White Dwarf
• Black Dwarf

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Life Cycle of a Massive Star

• Stellar Nebula
• Protostar
• Blue Giant
• Red Supergiant
• Supernova
• Neutron Star
• (Pulsar)
• OR
• 7. Black Hole

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Interactive Website

• http//aspire.cosmic-ray.org/labs/star_life/starli
  fe_main.html