Physics Photo of the Week

April 7, 2006

Orion Objects


Heather Aziz

From the photo one can see that two stars stand out from the rest in this constellation.  Those two stars are Betelguese (red) and Rigel (blue-white).  Betelgeuse  (Alpha Orionis) is 427 light-years away from earth.  It is a semi regular variable star. Betelgeuse is a red giant star.  It is red because it has a fairly low surface temperature for a star (2400 Kelvin).  It is 6 million years old.  It is the second brightest in the Orion constellation and the tenth brightest in the sky. Betelgeuse is 15 times more massive than the sun. If it were placed at the center of our solar system, its outer surface would extend well beyond the orbit of the Earth.  Astronomers predict that it will ultimately undergo a type two supernova explosion.  Which means that eventually Betelgeuse will become a Neutron star.  A Neutron star is the very strong super dense remains of a supernova with a center core of pure neutrons.
Rigel is a super giant.  It is the brightest star in Orion and shines with approximately 40,000 times the luminosity of the sun.  Rigel is located 773 light-years away from the earth.  It is the seventh brightest star in the sky and is believed to be a triple star that is orbited by Rigel B and C.  Rigel is a blue-white color because of its surface temperature of about 11,000 Kelvin.  The sun has a surface temperature of about 5800 Kelvin!

Another important object of the Orion constellation is the Orion nebula (left).  This nebula is 1500 light-years from the earth.  The Orion nebula is actually made up of two types of nebulas: emission nebula and reflection nebula.  An emission nebula is a high temperature gas cloud that is red because of hydrogen and is usually the site of star formation.  A reflection nebula is a cloud of dust that reflects light of near by stars and looks blue. The Orion nebula is the nearest formation region for stars to the earth.  Because of this it is possible to view from earth small regions of the nebula that seem to be on the verge of collapsing into new stars.
All photos by Donald F. Collins

Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department.  These photos feature an interesting phenomena in the world around us.  Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation.  Atmospheric phenomena are especially welcome.  Please send any photos to

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