611286
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Astrophysics Unit 13
- Stellar radiation and
stellar types
- Energy source
- The source of the Suns energy is nuclear fusion
in the interior of the star. Inside the Sun, nuclei
of hydrogen fuse together to form helium,
releasing energy in the process. Beucase high
pressures, the nuclei are suffciciently close to
each other for collisions to occur. Owing to
temperatures in excess of 10^8 K, the
electrostatic repulsion hydrogen nuclei can be
overcome and fuse together.
- As Kinetic energy of the particles inside the
Sun increase, the radiation pressure
increases. Radiation pressure is the force
exerted by solar radiation on the
surroundings. It acts to stabilize the Sun
against gravitational collapse, creating a kind
of equilibrium.
- The source of the Suns energy is nuclear fusion
in the interior of the star. Inside the Sun, nuclei
of hydrogen fuse together to form helium,
releasing energy in the process. Beucase high
pressures, the nuclei are suffciciently close to
each other for collisions to occur. Owing to
temperatures in excess of 10^8 K, the
electrostatic repulsion hydrogen nuclei can be
overcome and fuse together.
- Luminosity and Brightness
- The luminosity of a star
is defined as the energy
emitted per unit time.
- b= L/(4πd^2 )
- Apparent brightness of a star is defined as the power incident on Earth
perpendicular to unit area. To measure apparent brightness, the light
reaching the Earth is collected with a telescope and detected using a
charge-coupled device (CCD). The data is processed by a computer and
the apparent brightness can then be worked out accurately.
- The luminosity of a star
is defined as the energy
emitted per unit time.
- Wiens Displacement law
states that the peak
wavelength of the emission of
a black body is inversely
proportional to its temperature.
- Max. Wavelength = 2.9 x 10^-3 / T
- If the energy emitted from a star
is analyzed over a range of
wavelengths and the peak
wavelength is determined, then
the surface temp. of the star can
be determined.
- Max. Wavelength = 2.9 x 10^-3 / T
- Stellar Spectra
- Energy source
- Cosmology
- Stellar distances
- The universe
- Our solar system is made up of 8
planets. The planetary orbits have
the sun at one of the two foci of an
ellipse. the orbit is almost circular,
a circle being a special kind of
ellipse.
- Our solar system is made up of 8
planets. The planetary orbits have
the sun at one of the two foci of an
ellipse. the orbit is almost circular,
a circle being a special kind of
ellipse.
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