| − | A '''nebula''', from the [[Latin]] word for ''[[cloud]]'', is a cloud of interstellar [[dust]] and [[gas | gases]]. <ref>http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula.html</ref>. Nebulae have been observed both within the [[Milky Way]] [[galaxy]] and in other galaxies. These large clouds of mostly hydrogen gas can form stars, as likely happened to our solar system about 4.6 billion years ago. <ref>http://www.windows.ucar.edu/tour/our_solar_system/formation.html</ref> | + | A '''nebula''', from the [[Latin]] word for ''[[cloud]]'', is a cloud of interstellar [[dust]] and [[gas | gases]]. <ref>http://fusedweb.pppl.gov/CPEP/Chart_Pages/5.Plasmas/Nebula.html</ref>. Nebulae have been observed both within the [[Milky Way]] [[galaxy]] and in other galaxies. These large clouds of mostly hydrogen gas can form stars an planets. Our solar system formed about 4.6 billion years ago. <ref>http://www.windows.ucar.edu/tour/our_solar_system/formation.html</ref> |