... Our Galaxy . ... Stars . ... Spiral arms are home to much more than just the brightest stars, however. ... Spread along the bright spiral arms can be seen prominent dark lanes, clouds of molecular gas and dust which obscure the visible light. ... The spiral arms are lit up by the extraordinary luminous young massive stars that are born within the dark clouds of molecular gas that lie along the arms. ... This interpretation тАУ of a spiral galaxy with active star formation within it тАУ is not...