Changes

In the center of the core of the galaxy is a large, complex radio source known as '''Sagittarius A''' that is invisible in normal light due to interstellar dust.  Here a [[supernova]] remnant exists along with a region of ionized [[hydrogen]].  Towards the center of this complex is '''Sagittarius A*''', the source of the radio waves and is the location of a supermassive black hole.<ref>http://news.bbc.co.uk/2/hi/science/nature/7774287.stm</ref> <ref>http://cass.ucsd.edu/public/tutorial/MW.html</ref> The black hole itself isn't the source of the radio waves, but the large accretion disk around it.

In the center of the core of the galaxy is a large, complex radio source known as '''Sagittarius A''' that is invisible in normal light due to interstellar dust.  Here a [[supernova]] remnant exists along with a region of ionized [[hydrogen]].  Towards the center of this complex is '''Sagittarius A*''', the source of the radio waves and is the location of a supermassive black hole.<ref>http://news.bbc.co.uk/2/hi/science/nature/7774287.stm</ref> <ref>http://cass.ucsd.edu/public/tutorial/MW.html</ref> The black hole itself isn't the source of the radio waves, but the large accretion disk around it.

There appears to be no star formation currently in the core of the galaxy, which consists of mostly older, red stars and [[globular cluster|globular clusters]].  However, there is a cluster of 100-200 very young stars that seem to have formed all around the same time a few million years ago.  It is possible they are from a star cluster outside the galactic core and migrated inward over time and now orbit near Sagittarius A*.<ref>http://www.astro.ucla.edu/~ghezgroup/gc/publications/yso.shtml</ref>  They are sometimes collectively referred to as the '''paradox of youth''' as the presence of the supermassive black hole is thought to normally disrupt any star formation.  The area immediately surrounding the core of the galaxy though, known as the "'''5-kpc ring'''", holds a large percentage of both the galaxy's molecular hydrogen and current star formation.<ref>http://www.bu.edu/galacticring/new_introduction.htm</ref>  

There appears to be no star formation currently in the core of the galaxy, which consists of mostly older, red stars and [[globular cluster|globular clusters]].  However, there is a cluster of 100-200 very young stars.  It is possible they are from a star cluster outside the galactic core and migrated inward over time and now orbit near Sagittarius A*.<ref>http://www.astro.ucla.edu/~ghezgroup/gc/publications/yso.shtml</ref>  They are sometimes collectively referred to as the '''paradox of youth''' as the presence of the supermassive black hole is thought to normally disrupt any star formation.  The area immediately surrounding the core of the galaxy though, known as the "'''5-kpc ring'''", holds a large percentage of both the galaxy's molecular hydrogen and current star formation.<ref>http://www.bu.edu/galacticring/new_introduction.htm</ref>

===Disk===

===Disk===