CH 14 The Stars

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CH 14 The Stars

• Intro. to astronomy
• Nuclear reactions fuel the stars

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Nuclear reactions in stars

• All stars have a beginning and an end.
• In a series of nuclear reaction hydrogen is
  consumed and make helium.
• This is called hydrogen burning.
• Heaver elements are made when helium burns.
• 3 helium atoms make a carbon

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The interior of a large star displays concentric
shells of fusion reactions, yielding
progressively heavier elements toward the core.
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Neutrino (first detected 1956)

• Little neutral one
• No electric charge
• Travels at speed of light
• If stopped would have no mass
• Now routinely made in the lab and studied.

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Fusion in the sun

• P P ? D e n
• But we can only detect 30 of the amount they
  expect.

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This solar neutrino apparatus is located a mile
underground in the Homestake gold mine in South
Dakota.
It receives only about one-third of the expected
number of neutrinos from the Sun.
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The magnetic field of the Earth is swept out into
a long tail by the solar wind.
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The northern lights (aurora borealis) result from
the interaction of
A Question.

• the Earth and the moons gravity
• the Earths and the suns gravity
• the Earths and the suns magnetic fields
• the solar wind and the Earths magnetic field
• The moons and the Earths magnetic field

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The Suns peak output of energy is in the middle
of the visible spectrum, with lesser amounts of
energy emission at different wavelengths.
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Schematic diagrams of telescopes.
Optical telescope Radio wave
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Annie Jump Cannon (left) and Henrietta Swan
Leavitt (right) contributed important studies of
the spectroscopy of stars at the Harvard College
Observatory.
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The triangulation of stellar distances. By
measuring the angle of sight to a given star from
two points of known separation, we can determine
the stars distance from us.
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A Hertzsprung-Russell diagram plots a stars
temperature versus its energy output.
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• Started hydrogen burning more than 4.5 billion
  years ago and it will remain near that point on
  the diagram for several billion years more.
• As the hydrogen is consumed, helium burning
  starts.

The life cycle of the Sun.

• Once the helium is consumed, the nuclear fusion
  reactions will cease and gravitational collapse
  will cause the Sun to heat up.
• Eventually the Sun will cool to a white dwarf.

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A schematic diagram of a pulsar rapid
rotation intense magnetic field. This combination
of traits produces a pulsing, lighthouse-like
pattern of energetic radiation.
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Jocelyn Bell Burnell detected the first pulsars
in 1967.
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Black hole

• An object so dense that nothing, not even light
  can escape.
• Collapsing stars can become black holes.
• Material falling into black holes can emit light
  so we can see the effects of black holes
  eventhough we cannot see the holes themselves.
• Double stars.

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The distance to near stars can be determined by
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• looking at the stars position.
• triangulation.
• blue shift.
• red shift.
• using a ruler.