december in antarctica: the sun never sets. the images are 1 hour apart
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December in Antarctica: The Sun never sets.The images are 1 hour apart.
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The abundances of the chemical elements in the Sun (the cosmic abundances), relative to106 Si atoms.
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Light is a form of electromagnetic radiation and consists of alternating electric and magnetic fields
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The various types of electromagnetic radiation, also referred to as the electromagnetic spectrum.
Note: The shorter the wavelength of electromagnetic radiation, the higher is its energy.
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The spectrum of visible (“white”) light can be separated into its various wavelength components with the aid of a glass prism, into
the colors of the rainbow.
Definition: 1 Å (Ångstrom) = 10-8 cm.
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Bunsen’s discovery of the characteristic spectral absorption lines of the chemical elements.
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Characteristic spectra of the chemical elements Li, Fe, Ba, Ca and white light
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Determination of the abundances of the chemical elements in the Sun through the measurement of their spectra with a spectroscope
mounted on a telescope
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Spectrum of our Sun, showing the spectral lines of the multitude of chemical elements present in our star
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Spectrum of our Sun, indicating the presence of the spectral lines of the chemical element Fe
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Schematic diagram of the interior make-up of the Sun.
Listed are the gas density and the temperature as a function
of depth in the Sun.
Note: density of water = 1,of rock =~ 3,
and of iron metal = ~ 8.
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Relationship between the 3 temperature scales.
In the sciences, the Kelvin scale is commonly used.
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Sunspots appear dark, because they are cooler
(~ 4,000°K) than the
surrounding photosphere of
the Sun (~ 5,800°K).
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Sunspots occur in pairs
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Galileo, the discoverer of
sunspots
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Observation of sunspots on successive days show the
rotation of the Sun around its axis.
These observations indicate that the Sun does not rotate like a
solid body, but has differential rotation:
Sunspots at Sun’s equator rotate once around the Sun in ~ 25
days, whereas those at 75° N and S rotate once around the Sun in
~ 33 days.
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Origin of sunspots by compression of magnetic field lines due to differential rotation of the star.
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Sunspots occur in pairs, representing the N and S poles of the magnetic field lines
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The number of sunspots varies from year to year, with an 11 year sunspot cycle.
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The 11 year cycle in the frequency of sunspots, observed continuously back to Galileo
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“Granules” in the photosphere of the Sun, 300-1,000 km across. Granules are convection cells, with hotter gases (~ 200°K) rising in bright centers with velocities of ~ 2 km/sec, and sinking in dark areas.
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Solar flare
~ 10 Trillion megawatts
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Solar eclipse, showing “solar wind”.Photographed in 1973 in Kenya.
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The “Northern Lights”, or Aurora Borealis