Stars & GallaxiesStars & Gallaxies

CMSCMS Obj. 3-5 Describe the Obj. 3-5 Describe the appearance & nature of our appearance & nature of our

galaxy & the universegalaxy & the universeState Correlation: #7State Correlation: #7

What you will LearnWhat you will Learn

Measurement in SpaceMeasurement in Space Evolution of StarsEvolution of Stars Types of GalaxiesTypes of Galaxies Identify & Describe the Milky WayIdentify & Describe the Milky Way Identify & Describe Objects in the Identify & Describe Objects in the

UniverseUniverse

Star MagnitudeStar Magnitude

Why are some stars Brighter?Why are some stars Brighter? Absolute MagnitudeAbsolute Magnitude: Measure of the : Measure of the

amount of light actually given offamount of light actually given off Apparent MagnitudeApparent Magnitude: Measure of the : Measure of the

amount of light received on Earthamount of light received on Earth

How far away are stars?How far away are stars? ParallaxParallax: apparent shift in the position of : apparent shift in the position of

an object when view from two different an object when view from two different locations locations

measures the distance of stars from earth that measures the distance of stars from earth that are relatively close are relatively close

Light YearsLight Years: Unit of measurement for : Unit of measurement for large distances in space large distances in space

Distance light travels in 1 yearDistance light travels in 1 year Light travels 300,000 km/s or 9.5 trillion km /yearLight travels 300,000 km/s or 9.5 trillion km /year

Proxima CentauriProxima Centauri: closest star to earth : closest star to earth (4.3 light years away – 40 trillion km)(4.3 light years away – 40 trillion km)

StarStar CCoolloorr

Indicates temperatureIndicates temperature Hot Stars: Hot Stars: Blue Blue /W/Whitehite Cool Stars – Cool Stars – RedRed//OrangeOrange Medium StarsMedium Stars – – YellowYellow like our Sun like our Sun

Hertzsprung-Russell Hertzsprung-Russell diagram (H-R):diagram (H-R):

shows the shows the relationship relationship between the between the absolute absolute magnitude of a magnitude of a star and its star and its temperature temperature

Evolution of a StarEvolution of a Star NebulaNebula: large cloud of gas, plasma & dust within a : large cloud of gas, plasma & dust within a

galaxy where star formation takes placegalaxy where star formation takes place A star is born by fusion of hydrogen at 10 million KA star is born by fusion of hydrogen at 10 million K

Main Sequence StarMain Sequence Star: hydrogen fueled star: hydrogen fueled star Makes up about 90% of stars Makes up about 90% of stars Can be high or low massCan be high or low mass Our sun is main sequenceOur sun is main sequence

GiantsGiants: fueled by helium from a low mass star: fueled by helium from a low mass star Outer layers Cool & expands with a carbon coreOuter layers Cool & expands with a carbon core

White dwarfWhite dwarf: outer layer of giant escapes into space, : outer layer of giant escapes into space, core contracts leaving a hot dense small starcore contracts leaving a hot dense small star

Super GiantSuper Giant: fueled by helium from a high mass star: fueled by helium from a high mass star Outer layers Cool & expands with an iron coreOuter layers Cool & expands with an iron core Neutron starNeutron star: collapsed core of super giant with extremely : collapsed core of super giant with extremely

high densityhigh density Super NovaSuper Nova: exploding star: exploding star

Black HoleBlack Hole: tremendously big supernova that collapses to a point : tremendously big supernova that collapses to a point of no volumeof no volume

Black Holes Black Holes Neutron StarsNeutron Stars

GalaxiesGalaxies

Huge collection of stars, gas, & Huge collection of stars, gas, & dustdust

Three Types of GalaxiesThree Types of Galaxies EllipticalElliptical: range from spherical to elliptical: range from spherical to elliptical

No typical size or brightnessNo typical size or brightness Contains old cool red stars & small amounts of gas & dust, so no Contains old cool red stars & small amounts of gas & dust, so no

new stars are formingnew stars are forming Most common typeMost common type

SpiralSpiral: stars arranged in two or more spiral arms: stars arranged in two or more spiral arms New blue stars form in armsNew blue stars form in arms Center is often bulging disk of older red starsCenter is often bulging disk of older red stars Barred SpiralBarred Spiral: sub-group with a vast straight bar of stars lying : sub-group with a vast straight bar of stars lying

across the center with a spiral arm at the end of each baracross the center with a spiral arm at the end of each bar

IrregularIrregular: lack regular pattern & shape, and are : lack regular pattern & shape, and are small & faintsmall & faint Two types: colliding & gravitational interaction distorting the Two types: colliding & gravitational interaction distorting the

shapeshape Mixture of young & old stars with lots of gas & dust for new star Mixture of young & old stars with lots of gas & dust for new star

formationformation

Galaxies Galaxies

Our Galaxy - The Milky Our Galaxy - The Milky WayWay

Normal SpiralNormal Spiral About 100,000 light-years in diameterAbout 100,000 light-years in diameter Contains between 200 billion & 400 Contains between 200 billion & 400

billion starsbillion stars About 14 billion years old About 14 billion years old 3 basic parts:3 basic parts:

BulgeBulge DiskDisk HaloHalo

Milky WayMilky Way

Central BulgeCentral Bulge

Mostly older starsMostly older stars Small amounts of gas and dustSmall amounts of gas and dust Very little star formationVery little star formation

DiskDisk Flattened area containing the spiral arms Flattened area containing the spiral arms

that are pin-wheeled shapedthat are pin-wheeled shaped Our solar system is located on the Orion Arm Our solar system is located on the Orion Arm

25,000 light-years away from the central 25,000 light-years away from the central bulgebulge

Galactic ClustersGalactic Clusters: vast cloud of dust & gas : vast cloud of dust & gas that forms a group of starsthat forms a group of stars Contains a few dozen to thousands of starsContains a few dozen to thousands of stars Interstellar matter is thin but widespreadInterstellar matter is thin but widespread Bound together with gravity by a common originBound together with gravity by a common origin Also know as an open cluster because they break Also know as an open cluster because they break

apartapart Believed to be what forms the spiral armsBelieved to be what forms the spiral arms

HaloHalo Sphere of gas & stars surrounding the central Sphere of gas & stars surrounding the central

bulge & diskbulge & disk Thought to be 100’s of thousands of light-years Thought to be 100’s of thousands of light-years

acrossacross Oldest stars in the galaxyOldest stars in the galaxy Stars travel in clumps called…Stars travel in clumps called…

Globular Clusters: tight gravitationally bound Globular Clusters: tight gravitationally bound concentration of approximately 10 thousand to one concentration of approximately 10 thousand to one million stars that do not break apartmillion stars that do not break apart

Dark Matter: does not produce or reflect lightDark Matter: does not produce or reflect light Has a gravitational effect that can be detectedHas a gravitational effect that can be detected Believed to be the most common material in the Milky Believed to be the most common material in the Milky

WayWay

Dark MatterDark Matter

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Nebula Nebula

Most are just a few light-years wideMost are just a few light-years wide 2 main types2 main types

Planetary Nebula: forms when a star Planetary Nebula: forms when a star collapses and throws off some of its collapses and throws off some of its outer materials to form a cloudouter materials to form a cloud

Diffuse Nebula: also known as a Diffuse Nebula: also known as a gaseous nebula because it is a huge gaseous nebula because it is a huge cloud of gas and dust with regions of cloud of gas and dust with regions of new star formationnew star formation There is no star in its centerThere is no star in its center

Light Year VideoLight Year Video

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Proxima CentauriProxima Centauri

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