Star Systems & GalaxiesStar Systems & Galaxies

Star Systems & ClustersStar Systems & ClustersMost stars are members of groups of two Most stars are members of groups of two

or more stars, called or more stars, called star systemsstar systems..Our solar system only has one star.Our solar system only has one star.

Binary StarsBinary StarsStar systems with two stars are called Star systems with two stars are called

binarybinary stars. stars.A A eclipsingeclipsing binarybinary system occurs when one system occurs when one

star periodically blocks the light from another star periodically blocks the light from another star.star.

Binary starsBinary stars eclipsing binary system

PLIEADES OPEN CLUSTER

Star ClustersStar Clusters Many stars belong to larger groupings called star Many stars belong to larger groupings called star

clustersclusters.. Open clustersOpen clusters have a loose chaotic appearance and have a loose chaotic appearance and

are made up of young stars (less than a billion years are made up of young stars (less than a billion years old). old).

Globular clustersGlobular clusters are round and densely packed are round and densely packed groupings containing older stars (12-13 billion years groupings containing older stars (12-13 billion years old).old).

47 Tucanae, 10-12 billion years old, 15,000 light-years from Earth.

Globular Cluster

GalaxiesGalaxies GalaxiesGalaxies are large groups of stars, star are large groups of stars, star

systems, star clusters, dust, and gas bound systems, star clusters, dust, and gas bound together by gravity.together by gravity. Come in a variety of shapes and sizes.Come in a variety of shapes and sizes. Contain trillions of stars.Contain trillions of stars. Classified by Classified by shapeshape.. It is estimated that there is over 100 billion galaxies.It is estimated that there is over 100 billion galaxies.

Three Shapes of GalaxiesThree Shapes of Galaxies

SpiralSpiral Galaxies GalaxiesFlattened arms that spin Flattened arms that spin

around the center, mostly around the center, mostly made up of young stars.made up of young stars.

EllipticalElliptical Galaxies Galaxies round, from flat disks to round, from flat disks to

spheres, contain older stars.spheres, contain older stars. IrregularIrregular Galaxies Galaxies

Irregular shape, so they Irregular shape, so they make up their own category, make up their own category, generally young stars with generally young stars with lots of dust and gases.lots of dust and gases.

Andromeda spiral galaxy

Elliptical Galaxy M87

Irregular Galaxy M82

Milky Way GalaxyMilky Way Galaxy

Our solar Our solar system is system is located in a located in a spiralspiral galaxy galaxy called the called the Milky WayMilky Way..

Scale of the UniverseScale of the Universe Since numbers astronomers use are often very Since numbers astronomers use are often very

large, they use large, they use scientific notationscientific notation to describe to describe sizes and distances in the universe.sizes and distances in the universe. Example: 1 light-year is 9,500,000,000,000,000 Example: 1 light-year is 9,500,000,000,000,000

meters or 9.5 X 10meters or 9.5 X 101515 meters. meters.

Galaxies, and the Galaxies, and the UniverseUniverse

The UniverseThe Universe

The Universe is made up of many The Universe is made up of many Galaxies.Galaxies.

The study of the origin, structure, and The study of the origin, structure, and future of the Universe is called future of the Universe is called Cosmology.Cosmology.Astronomers use galaxies far away to Astronomers use galaxies far away to

hypothesize how they form.hypothesize how they form.

Doppler EffectDoppler Effect

Change in wavelength caused by the Change in wavelength caused by the apparent motion of the source.apparent motion of the source.

Blue Shift - light from objects coming Blue Shift - light from objects coming toward you is compressed looks more toward you is compressed looks more blue.blue.

Red Shift - light from objects moving away Red Shift - light from objects moving away looks more red.looks more red.

Big SurpriseBig Surprise

No Galaxies showed blue shiftNo Galaxies showed blue shiftAll galaxies showed red shift.All galaxies showed red shift.Which meansWhich means

All galaxies were moving awayAll galaxies were moving awayThe universe is expandingThe universe is expanding

Origin of the UniverseOrigin of the Universe

The theory that the universe began with a The theory that the universe began with a tremendous explosion is known as the Big tremendous explosion is known as the Big Bang Theory.Bang Theory.13.7 billion years ago, all matter was 13.7 billion years ago, all matter was

compressed into one spot and expanded compressed into one spot and expanded rapidly.rapidly.

Explained red shift.Explained red shift.