Slide 31
Continuous
Emission or Bright Line (from ionized gas, like a nebula or a neon sign)
Absorption or dark line (from stars)
Slide 32
Radiation
All stars emit radiation
Radio, infrared, visible, ultraviolet, x-ray and even some gamma rays
Most sunlight is yellow-green visible light or close to it
The Sun at X-ray wavelengths
Image at http://imagine.gsfc.nasa.gov/docs/science/know_l1/sun.html
Image and info at http://imagine.gsfc.nasa.gov/docs/teachers/gammaraybursts/imagine/page18.html
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Slide 33
Using a Star’s Spectrum
We can use a star’s spectrum to classify it.
NOAO/AURA/NSF image at http://antwrp.gsfc.nasa.gov/apod/ap010530.html
Slide 34
Slide 35
Time to Create a Stellar Graph
Everyone will receive several “stars”
Place them on the large paper, according to their color and their brightness
This is a version of the Hertzsprung-Russell diagram.
Slide 36
Hertzsprung-Russell Diagram
Slide 37
Young stars form in nebulae from Small Magellanic Cloud
Slide 38
Star-forming region in the Large Magellanic Cloud
Slide 39
Slide 40
Interstellar “eggs”
Movie at
Slide 41
Our Sun is a Regular/ Small Star
On the “Main Sequence”
Slide 42
In a few Billion years… Red Giant
Slide 43
Billions of years ago, things may have been different
The Sun was cooler (by up to 30%!)
Earth’s atmosphere was different (thicker, carbon dioxide)
Conditions will be different in the future
By many accounts, increases in the Sun’s temperature will make Earth uninhabitable in 1 billion years or less
These changes will also affect other planets… Mars?