shadows on the sun the story of sunspots dr. lyndsay fletcher, university of glasgow
TRANSCRIPT
Shadows on the SunThe story of sunspots
Dr. Lyndsay Fletcher, University of Glasgow
Image: Bill Leslie, Forres
The first recorded observation
Photocredit: Michael Myers
364 BC – Chinese astronomer Gan-De records a darkening on the face of the Sun.
Sunspots recorded regularly by ~ 30 BC.
Observing through thin cloud or smoke?
Photocredit: Ed Sanders
A Perfect Body?300-250 BC - The Aristotelian view of the Universe
The Earth is at the centre of a set of revolving spheres,each carrying a perfect andimmutable celestial body
The Sun is one such perfect body and should therefore be free of flaws
But Theophrastus (374-287 B.C.) claims to observe flaws on the Sun
The first known drawing of sunspots?by John of Worcester, 8th December 1128
The first sunspot drawing
The Copernican Revolution
1543 - the Sun at the centre of the ‘Universe’Sunspot observations have a bearing on the 16th C. cosmology,
demonstrating that heavenly bodies are not perfect and unchanging.
The first telescopic observationsGalileo is usually credited with first turning a telescope to look at the Sun. This might not be correct!
Galileo Scheiner Fabricius Harriot
The four contenders are:
Galileo claimed tohave been observingsunspots since theAutumn of 1610.
However, his first public demonstration was in 1611.
The first known record of a telescopic sunspot observation
This was drawn by the English mathematicianThomas Harriot….
..on 8th December 1610
‘..the greatest mathematician thatOxford has produced.’
Thomas Harriot
1560 -1621
1613, Italy 2001, Hawai’i
Heinrich Schwabe
The 11-year cycle
Image: NASA/ISAS/LMSAL Yohkoh
1992
1996
2001
Movie: NASA Sun-Earth Connections
Close-up of an active region (TRACE satellite)
Iron filings around a bar magnet line up according to magnetic force field.
Coronal plasma is also tied to magnetic force field
Solar magnetic fieldWhite = ‘north’ Black = ‘south’
umbra
penumbra
A Simple Sunspot
Images: Swedish Solar Telescope
Why are sunspots dark?Because they are cooler than their surroundings, and so produce less radiation:
Why are sunspots cool?
Because they are so strongly magnetised
Magnetic field ‘resists’ convection, so heat from the rest of the photosphere can’t be fed into the sunspot
Image: NASA/ISAS/LMSAL Yohkoh
1992
1996
2001
A topical question – the effect of solar activity on climate
Clear historical association of periods of low sunspot number and the Earth’s climate. Is this still important?
http://solarb.msfc.nasa.gov/index.html
http://sdo.gsfc.nasa.gov/
http://trace.lmsal.com/
http://sohowww.nascom.nasa.gov/
More images and movies at: