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Stars  &  Our Sun

Current Solar Images

Test

 Outline Page
Classification of stars:

 

 

This is a view of the sun unlike anything you have probably seen.  It is viewed as if the only light you can see from it comes from the emissions of the element Helium.  The sun "burns" Hydrogen, and the "ash" left behind is Helium.  The sun is, even after 41/2 Billion years, still made mostly of Hydrogen.


Click on image to see full size version.

 

 

 
A Glossary solar terms

 

  

The sun is powered by Fusion.

Layers and Surface Features

This image (From "Views of the Solar System") is a quick reference guide to the sun's basic layer structure.  By extension, it is thought to apply in form, though not necessarily in extent, to most stars that are similar in size to our sun.

Click for larger image

 Click for larger image.
From "Views of the Solar System" by Calvin J. Hamilton

 

There are different interpretations and ongoing research that account for differences between these data and other tables you may have seen:

Layer

Temperature, °Kelvin

Size, or Distance

Core 16 million K 86,000 miles (140,000 km)
Radiation zone From 9 million K to 2.0 million K From  140,000 km (86,000 miles) to 513,000 km (319,000 miles) from the center
Convection zone From 2.0 million K to 6500 K From just below the photosphere down to about 183,000 km (130,000 miles) below the surface
Photosphere
 (Considered the "surface" of the Sun)		 From 6500 K at the bottom to 4000 K at the top To about 500 km (300 miles) deep
Chromosphere From 4000 K at the bottom  to 8000 K at the top From 400 km (250 miles) to 2100 km (1300 miles) above the photosphere
Transition Region From 8000 K to 
about 500,000 K		 Very narrow 100 km (60 miles) layer between the chromosphere 
and the corona
Corona 500,000 K or more, up to a few million K From 2100 km (1300 miles) out millions of km

 

The Sun's Statistics
(from Views of the Solar System)

 Mass (kg)

1.989x1030

 Mass (Earth = 1)

332,830 

 Equatorial radius (km)

695,000 

 Equatorial radius (Earth = 1)

108.97 

 Rotational period (days)

25-36* 

 Apparent Magnitude

-26.72 

Absolute Magnitude

4.8

 Mean surface temperature

6,000°K 

 Principal chemistry Percentage
Hydrogen
Helium
Oxygen 
Carbon
Nitrogen
Neon
Iron
Silicon
Magnesium
Sulfur
All others 
 92.1% 
7.8% 
0.061% 
0.030% 
0.0084% 
0.0076% 
0.0037% 
0.0031% 
0.0024% 
0.0015% 
0.0015% 

*The Sun's period of rotation at the surface varies from approximately 25 days at the equator to 36 days at the poles. Deep down, below the convective zone, everything appears to rotate with a period of 27 days.

Some well-known bright stars (From Chris Dolan's The Constellations and Their Stars )

Star Name Distance
(light years)		 Apparent
Magnitude		 Absolute
Magnitude		 Spectral
Type
Sirius 8.6 -1.46 1.4 A1Vm
Rigil Kentaurus 4.3 -0.27 4.4 G2V + K1V
Arcturus 34 -0.04 0.2 K1.5IIIp
Vega 25 0.03 0.6 A0Va
Rigel ~1400 0.12 -8.1 B81ae
Procyon 11.4 0.38 2.6 F5IV-V
Betelgeuse ~1400 0.50 (var.) -7.2 M2Iab
Aldebaran 60 0.85 (var.) -0.3 K5III
Antares ~520 0.96 (var.) -5.2 M1.5Iab
Spica 220 0.98 (var.) -3.2 B1V
Pollux 40 1.14 0.7 K0IIIb
Deneb 1500 1.25 -7.2 A2Ia
Castor 49 1.57 0.5 A1V + A2V

Surface Features

• Are areas of the photosphere cooler than 
  surrounding areas

• Temporary

• Caused by electromagnetic anomalies

      Occur in cycles -

      • Maxima about every 11 years
 

Prominences
Huge arching columns of plasma (charged gas particles), which seem to follow magnetic field paths.
From the ESA and NASA SOHO Satellite, in early 2000

Solar Flares

 

     Click for larger image
Solar flares are not to be confused with ; What is a Solar Flare? - This NASA page serves well as an introduction.

This NASA page - Solar Flares - does, too.

 

  • Plasma shooting  away from the sun
  • A cause of radio disruptions on earth
  • May be part of what we call "Cosmic rays"

 

 

Coronal Mass Ejections
  What is a Coronal Mass Ejection? - This NASA page serves well as an introduction.

See them at Coronal Mass Ejections from the Solar Maximum Mission

Solar Wind What is the Solar Wind? - This NASA page serves well as an introduction.

NASA education pages

Okay, now take this test.

Read through the page above. Click on the links. Think about what you're seeing. Ask each other what you think about these things.

Please do NOT go on until you have taken and passed this test!

  • Test on the SUN (No YOU stay here, it's too hot there! Test is ABOUT the sun!)

 

 

UPDATED: 11/04/07