N▪nakedeyelimit-Forobserversinverydarkskies,itispossibletoseestarsasfaintas6thmagnitude.Themagnitudesystemisa rankingsystemwherefirstmagnitudestarsarethebrightest.InlightpollutedskieswhereIlive,weareluckytosee3rdmagnitude stars.▪nebula-Intheclassicalsense,anebulaisanyastronomicalobjectthatisnotapinpointoflight.Atonetime,thisdefinitionincluded galaxiesotherthanourownMilkyWay,andclustersofstars.Nowadays,thedefinitionislimitedtopatchoflightcausedbyglowing interstellar gas or dust.▪neutronstar- Acondensedremnantofanexplodedmassivestar,nobiggerthanafewkilometersinsize.Spinningneutronstars are what we observe as pulsars.