ConstellationsConstellations

ConstellationsConstellations Patterns in the skyPatterns in the sky Represent Mythical Characters, Animals Represent Mythical Characters, Animals

or Objects or Objects ExamplesExamples

Big Dipper (Ursa Major), Little Dipper (Ursa Big Dipper (Ursa Major), Little Dipper (Ursa Minor), OrionMinor), Orion

CircumpolarCircumpolar• Meaning they stay above the horizon all year longMeaning they stay above the horizon all year long

Big DipperBig Dipper

Little DipperLittle Dipper

OrionOrion

Properties of Stars’ BrightnessProperties of Stars’ Brightness

Absolute MagnitudeAbsolute Magnitude Is a measure of the light that a star gives Is a measure of the light that a star gives

offoff

Apparent MagnitudeApparent Magnitude Is a measure of the amount of light that is Is a measure of the amount of light that is

received on Earthreceived on Earth

Why the Two MeasurementsWhy the Two Measurements

Is helps us classify starsIs helps us classify stars Helps us measure distances to starsHelps us measure distances to stars

Here’s HowHere’s How

Luisa conducted an experiment to Luisa conducted an experiment to determine the relationship between the determine the relationship between the distance and the brightness of stars. She distance and the brightness of stars. She placed a light bulb at different distances placed a light bulb at different distances along a meter stick and measured the along a meter stick and measured the brightness of the light with a light meter. On brightness of the light with a light meter. On next side you will see Luisa’s data. next side you will see Luisa’s data.

What trends do you notice?What trends do you notice? What is the relationship between light What is the relationship between light

intensity and distance?intensity and distance?

Luisa’s Data TableLuisa’s Data Table

Effect of Distance on LightEffect of Distance on Light

Distance (cm)Distance (cm) Meter Reading (luxes)Meter Reading (luxes)

2020 4150.04150.0

4040 1037.51037.5

6060 461.1461.1

8080 259.4259.4

Space MeasurementSpace Measurement

ParallaxParallax Astronomers measure the apparent shift in Astronomers measure the apparent shift in

its position when viewed from two different its position when viewed from two different anglesangles

Light YearLight Year Because of the vast dimensions of space we Because of the vast dimensions of space we

use Light Years when calculating Distancesuse Light Years when calculating Distances Light travels at 3.00 x 10^8 m/sLight travels at 3.00 x 10^8 m/s

• How far does it travel in one year?How far does it travel in one year?

ParallaxParallax

Star PropertiesStar Properties

ColorColor Indicates TemperatureIndicates Temperature Hot stars are blue/whiteHot stars are blue/white Cool Stars look orange/redCool Stars look orange/red Yellow Stars indicate medium temperatureYellow Stars indicate medium temperature

• Our Sun is a medium temperature starOur Sun is a medium temperature star

Star PropertiesStar Properties

SpectrumSpectrum View Star light with a spectroscope you can View Star light with a spectroscope you can

break up the visible light into a “fingerprint”break up the visible light into a “fingerprint” Spectrum indicates elements in the star’s Spectrum indicates elements in the star’s

atmosphereatmosphere Spectrum gives the following info:Spectrum gives the following info:

• TempTemp• PressurePressure• DensityDensity• Motion of the Star’s GasesMotion of the Star’s Gases

Classifying StarsClassifying Stars

Ejnar Hertzsprung and Ejnar Hertzsprung and Henry RussellHenry Russell

Graphed Stars by Graphed Stars by Temperature and Temperature and Absolute MagnitudeAbsolute Magnitude

Called it the H-R Called it the H-R DiagramDiagram

H-R DiagramH-R Diagram

Main Sequence (MS)Main Sequence (MS) Diagonal BandDiagonal Band Upper LeftUpper Left

Hot Blue. Bright StarsHot Blue. Bright Stars

Lower RightLower Right Cool, Red, Dim StarsCool, Red, Dim Stars

Middle Middle Average Yellow StarsAverage Yellow Stars

Dwarfs and GiantsDwarfs and Giants 10% of Stars that 10% of Stars that

Don’t Fit on MSDon’t Fit on MS

Production of EnergyProduction of Energy

Nuclear FusionNuclear Fusion Joining of AtomsJoining of Atoms Proton – Proton Proton – Proton

ChainChain Starts with two Starts with two

Protons and Ends with Protons and Ends with Helium Helium

ENERGYENERGY

Stellar EvolutionStellar Evolution

Stellar EvolutionStellar Evolution1.1. Nebula contractionNebula contraction

Temperature increaseTemperature increase At 10 million Kelvin Fusion Begins At 10 million Kelvin Fusion Begins

2.2. Balancing of Heat and PressureBalancing of Heat and Pressure This is Called steady State EquilibriumThis is Called steady State Equilibrium Balance is lost when Hydrogen Core is used upBalance is lost when Hydrogen Core is used up Core contracts and heats up causing outer Core contracts and heats up causing outer

layers to expand and coollayers to expand and cool Star becomes a giantStar becomes a giant Helium nuclei fuse to form a core of CarbonHelium nuclei fuse to form a core of Carbon

Stellar EvolutionStellar Evolution

3.3. White DwarfWhite Dwarf Helium is exhausted and outer layers of giant Helium is exhausted and outer layers of giant

escapeescape Core contracts into a hot dense starCore contracts into a hot dense star

4.4. SupergiantsSupergiants Massive stars causes higher temps and greater Massive stars causes higher temps and greater

expansionexpansion Fusion stopsFusion stops Core crashes inward causing the outer part to Core crashes inward causing the outer part to

explode into a Supernovaexplode into a Supernova

Stellar EvolutionStellar Evolution

5.5. Collapsed Core of a Supernova may form Collapsed Core of a Supernova may form a neutron star of extremely high densitya neutron star of extremely high density

6.6. A Tremendously Big Supernova Core can A Tremendously Big Supernova Core can collapse to a point of no Volume – a Black collapse to a point of no Volume – a Black HoleHole

Gravity is so strong not even light can escapeGravity is so strong not even light can escape Beyond the Event Horizon gravity operates as Beyond the Event Horizon gravity operates as

normalnormal

Interstellar Nursery Interstellar Nursery

Life Cycle of Our SunLife Cycle of Our Sun

1987 Super Nova1987 Super Nova

http://aspire.cosmic-ray.org/labs/star_life/starlife_main.hthttp://aspire.cosmic-ray.org/labs/star_life/starlife_main.htmlml

http://btc.montana.edu/ceres/html/LifeCycle/stars1.html#http://btc.montana.edu/ceres/html/LifeCycle/stars1.html#activity2activity2

http://www.ioncmaste.ca/homepage/resources/web_resohttp://www.ioncmaste.ca/homepage/resources/web_resources/CSA_Astro9/files/multimedia/unit2/star_lifecycle/sturces/CSA_Astro9/files/multimedia/unit2/star_lifecycle/star_lifecycle.htmlar_lifecycle.html

http://chandra.harvard.edu/resources/misc/http://chandra.harvard.edu/resources/misc/special_features.htmlspecial_features.html

Black HoleBlack Hole