Friday, April 28, 2017

The Life Cycle of Spiral Arm Galaxies

By James A. Marusek

 Our solar system resides in a spiral arm galaxy called the Milky Way.  A galaxy is a system of millions or billions of stars and the remnants of dead stars (black holes, white dwarfs, neutron stars), small bodies (planets, asteroids, comets), and disassociated atoms, ions and elementary particles, held together by gravitational and electromagnetic attraction.  There are at least 2 trillion galaxies in our observable universe and many of these are spiral galaxies.
 
Spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge.  Spiral galaxies resemble spiraling pinwheels.  The spiral arms shine brightly in the night’s sky because they are composed of the brightest stars in the universe.  These are massive stars of spectral type “O” and slightly smaller type “B” stars using the Yerkes classification system.  O-type stars are very hot and luminous, and appear in the visible spectrum as bluish-white.  These stars are commonly called giants, and supergiants.  These stars have between 15 and 90 times the mass of our Sun and surface temperatures between 30,000 and 52,000° K.  They are between 30,000 times and several million times as luminous as our Sun.......To Read More...


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