GalaxiesGalaxies

Your complete address is part of a much Your complete address is part of a much larger system than your street, city, state, larger system than your street, city, state,

country, and even the planet Earth.country, and even the planet Earth.

. . . You also live in the Milky Way

Galaxy.

GalaxiesGalaxies

Are large groups of stars, dust, and gasAre large groups of stars, dust, and gasCome in a variety of shapes and sizesCome in a variety of shapes and sizesLarge galaxies contain more than a trillion Large galaxies contain more than a trillion

stars!stars!Hubble Space Telescope has helped us Hubble Space Telescope has helped us

understand the different types of galaxiesunderstand the different types of galaxiesAre classified by their different shapesAre classified by their different shapes

Spiral GalaxiesSpiral Galaxies

Have a bulge at the Have a bulge at the centercenter

Have spiral armsHave spiral armsArms made up of gas, Arms made up of gas,

dust, and new starsdust, and new starsExamples: Andromeda Examples: Andromeda

and our Milky Way and our Milky Way GalaxyGalaxy

Interesting Facts!Interesting Facts!

Earth is about two-thirds of the distance Earth is about two-thirds of the distance from the center of the Milky Way to the from the center of the Milky Way to the edge of the Milky Way.edge of the Milky Way.

Interesting Facts!Interesting Facts!

Our solar system revolves around the Our solar system revolves around the galaxy every 200 million years.galaxy every 200 million years.

Interesting Facts!Interesting Facts!

The last time the solar system was in its The last time the solar system was in its current position was during the Triassic current position was during the Triassic period, when dinosaurs first appeared on period, when dinosaurs first appeared on Earth!Earth!

Other Spiral GalaxiesOther Spiral Galaxies

Barred GalaxiesBarred Galaxies

Much like spiral Much like spiral galaxiesgalaxies

Have two distinct Have two distinct “bars” vs. many spiral “bars” vs. many spiral armsarms

Other Barred GalaxiesOther Barred Galaxies

Elliptical GalaxiesElliptical Galaxies

About 1/3About 1/3rdrd of all galaxies of all galaxies Simply a massive blob of starsSimply a massive blob of stars Spherical or more stretched outSpherical or more stretched out Very bright centers with little extra gas and dustVery bright centers with little extra gas and dust Contain mostly old starsContain mostly old stars

Lenticular GalaxiesLenticular Galaxies

Has both a bulge and a diskHas both a bulge and a disk All the stars are thought to be oldAll the stars are thought to be old Have no spiral armsHave no spiral arms There is little or no gas There is little or no gas

Irregular GalaxiesIrregular Galaxies

Don’t tend to fit into any other classDon’t tend to fit into any other class Irregular shapeIrregular shapeNo center bulgeNo center bulgeMay have been formed by the collision of May have been formed by the collision of

two or more galaxiestwo or more galaxiesMany are close in proximity to large spiral Many are close in proximity to large spiral

galaxies. Perhaps the spiral galaxies are galaxies. Perhaps the spiral galaxies are distorting the shape of irregular galaxies.distorting the shape of irregular galaxies.

What are Galaxies Composed of?What are Galaxies Composed of?

Billions of starsBillions of starsSome planetary systems Some planetary systems Gas cloudsGas cloudsStar clustersStar clusters

NebulaNebula

A large cloud of dust and gas in interstellar A large cloud of dust and gas in interstellar spacespace

A region in space where stars are born or A region in space where stars are born or where stars explode at the end of their where stars explode at the end of their liveslives

Spiral galaxies usually have nebula, but Spiral galaxies usually have nebula, but elliptical galaxies contain very few.elliptical galaxies contain very few.

Eagle NebulaEagle Nebula

Scientists Scientists believe that believe that stars are being stars are being born in the born in the pillars of this pillars of this nebulanebula

Other NebulaOther Nebula

Star ClustersStar Clusters

Globular ClustersGlobular Clusters = groups of older stars, = groups of older stars, looks like a ball, contains up to 1 million looks like a ball, contains up to 1 million starsstars

Star ClustersStar Clusters

Open ClustersOpen Clusters = = a group of stars a group of stars that are close that are close together relative together relative to surrounding to surrounding starsstars

The Pleiades are The Pleiades are an open clusteran open cluster

QuasarsQuasarsStarlikeStarlikeAre very luminous (bright)Are very luminous (bright)Generate a lot of energyGenerate a lot of energyMay be caused by massive black holes in May be caused by massive black holes in

the cores of some galaxiesthe cores of some galaxiesThought to be the most distant objects in Thought to be the most distant objects in

the universe; 6 billion light-years away!the universe; 6 billion light-years away!

Origin of GalaxiesOrigin of Galaxies

How is looking through a How is looking through a telescope like looking back telescope like looking back in time?in time?

Looking at distant galaxies Looking at distant galaxies reveals what early galaxies reveals what early galaxies may have looked like.may have looked like.

SummarySummary

The universe consists of billions of galaxiesThe universe consists of billions of galaxiesGalaxies are classified by shapeGalaxies are classified by shapeThe Milky Way galaxy is a spiral galaxyThe Milky Way galaxy is a spiral galaxyStudying galaxies helps scientists Studying galaxies helps scientists

understand the origin on our galaxy and the understand the origin on our galaxy and the universeuniverse