Local Galaxies and Local Galaxies and Collisions of GalaxiesCollisions of GalaxiesPSC 203PSC 203OverviewOverviewIn this lecture …In this lecture …Nearby galaxiesNearby galaxiesInteractions of galaxiesInteractions of galaxiesReviewReviewWhat galaxy do we live in?What galaxy do we live in?What type of galaxy is ours?What type of galaxy is ours?What are the other types of galaxies?What are the other types of galaxies?Milky Way GalaxyMilky Way GalaxyLocal Sub-GroupLocal Sub-GroupNearby GalaxiesNearby GalaxiesClosest galaxyClosest galaxySagittarius dwarfSagittarius dwarfDwarf ellipticalDwarf ellipticalOther very close galaxiesOther very close galaxiesLarge and Small Large and Small Magellanic cloudsMagellanic cloudsIrregular galaxiesIrregular galaxiesSagittarius Dwarf GalaxySagittarius Dwarf GalaxyHard to seeHard to seeFairly faintFairly faintSpread out on skySpread out on skyOther stars in frontOther stars in frontLarge Magellanic cloud Small Magellanic cloud Local Sub-GroupLocal Sub-Grouplocal sub-grouplocal sub-groupWhat types of galaxies are in local sub-What types of galaxies are in local sub-group?group?Us, a spiralUs, a spiralMostly dwarf ellipticalsMostly dwarf ellipticalsSome irregularsSome irregularsLocal GroupLocal GroupThe full local group is larger stillThe full local group is larger stillabout 30-40 galaxies about 30-40 galaxies about 1 Mpc acrossabout 1 Mpc acrossbiggest:biggest:Andromeda galaxyAndromeda galaxyVideo,galaxies of the local groupVideo,galaxies of the local groupAndromeda Interacting GalaxiesInteracting GalaxiesDefinition ...Definition ...Galaxies which are close enough for their Galaxies which are close enough for their mutual gravity to affect each othermutual gravity to affect each otherInteracting GalaxiesInteracting Galaxiessome irregulars form when galaxies some irregulars form when galaxies interactinteractgravity of one pulls on the othergravity of one pulls on the othermay even collidemay even collidevideo, what happens when galaxies ...video, what happens when galaxies ... end result is galaxy or galaxies with end result is galaxy or galaxies with distortionsdistortionsCollision OverviewCollision OverviewGas and dust affected mostGas and dust affected mostPulled away into strange shapesPulled away into strange shapesNew star formation triggeredNew star formation triggeredStars may be deflectedStars may be deflectedMove to different location in galaxyMove to different location in galaxyMay be flung out and separate from galaxyMay be flung out and separate from galaxyStars themselves don't collideStars themselves don't collideSimulationsSimulationsSimulations often used to predict Simulations often used to predict interactions...interactions...Video, physics simulationVideo, physics simulationVideo, multiple galaxy collisionVideo, multiple galaxy collisionSimulations match well to observationsSimulations match well to observationsvideo, simulation vs observationvideo, simulation vs observationExample ImagesExample ImagesExample ImagesExample ImagesGalaxy mergersGalaxy mergersVery large galaxies may be due to mergers Very large galaxies may be due to mergers of many smaller galaxiesof many smaller galaxiesVideo, Hubblecast 16Video, Hubblecast 16Slow and gradual processSlow and gradual processInteractions in the Local GroupInteractions in the Local GroupSagittarius dwarf galaxySagittarius dwarf galaxyAlready collided with Milky way and emerged Already collided with Milky way and emerged from the other side at least once, probably from the other side at least once, probably more timesmore timesVideo, Sagittarius galaxy fly aroundVideo, Sagittarius galaxy fly aroundOther dwarf galaxiesOther dwarf galaxiesEvidence of other dwarf galaxies already Evidence of other dwarf galaxies already merged with Milky Waymerged with Milky WayMilky Way and AndromedaMilky Way and AndromedaAndromeda has interacted with its Andromeda has interacted with its neighborsneighborsMilky Way and Andromeda will eventually Milky Way and Andromeda will eventually interactinteractVideo, Andromeda, Beauty and the BeastVideo, Andromeda, Beauty and the BeastRecent evidenceRecent evidenceUsed to think that Andromeda is much Used to think that Andromeda is much larger than uslarger than usAndromeda and Milky Way close to same sizeAndromeda and Milky Way close to same sizeWill collide a bit earlierWill collide a bit earlierMaybe 3 billion years from nowMaybe 3 billion years from