The Sun…a star in our solar system (continued)
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Transcript of The Sun…a star in our solar system (continued)
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The Sun…a star in our solar system (continued)
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But first…see a solar twin tonight
Beta Canum Venaticorum…look
almost up and a little east at 9PM
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Beta Canum Venaticorum (Beta CVn)
• Spectral type: G0V• Temperature: 5930 K• Luminosity (relative to
Sun): 1.12• Distance: 27.3 light
years• Judged best
candidate by astronomer Margaret Turnbull to try and communicate with them
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Next topic: solar activity
The Sun doesn’t always look like it does today
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Sunspots illustrate the rotation of the Sun
Sunspots over several days
The Sun rotates with a period of 27 days (a good indicator of its age)
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Closeup of a sunspot
Sunspots are regions of strong magnetics fields (0.2 -0.4 Tesla)
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Sunspots and their strong magnetic fields are related to more mysterious aspects of
the Sun
Above the photosphere are more rarefied and hotter parts of the solar atmosphere
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The Chromosphere-region above the photosphere, and substantially hotter
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The Solar Corona
What is it? How did it get that way?
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The X-Ray Sun
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The Temperature Profile in the Solar Atmosphere
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The process or processes responsible for heating the solar corona almost certainly
involve the solar magnetic field
We just don’t know how
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The hot, rarefield, magnetically-dominated parts of the solar atmosphere show continual activity and energy release
erupting solar prominence...April 21, 2010
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Solar activity includes two violent types of events
• Solar flares
• Coronal mass ejections
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Coronal mass ejections
A loop of matter “blasts off” from the Sun
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Solar flare…the movie
The solar flare of April 21, 2002, shown on Astronomy Picture of Day for November 6,
2007
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Why are flares and coronal mass ejections important?
• They are dangerous! They can generate levels of radiation in interplanetary space that are lethal
• They are part of, and play a role in, the development of the solar wind
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Sunspots and solar activity: they come and go
Sept. 21, 2000 Jan. 26, 2008
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The 11 year solar cycle: where are we now?
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The 11 year solar cycle goes back to the time of Galileo
Maunder Minimum