Constellations Constellations  Patterns in the sky  Represent Mythical Characters, Animals or Objects  Examples Big Dipper (Ursa Major), Little Dipper (Ursa Minor), Orion Big Dipper (Ursa Major), Little Dipper (Ursa Minor), Orion Circumpolar Circumpolar Meaning they stay above the horizon all year longMeaning they stay above the horizon all year long

Big Dipper

Little Dipper

Orion

Properties of Stars’ Brightness Absolute Magnitude  Is a measure of the light that a star gives off Apparent Magnitude  Is a measure of the amount of light that is received on Earth

Why the Two Measurements  Is helps us classify stars  Helps us measure distances to stars

Here’s How  Luisa conducted an experiment to determine the relationship between the distance and the brightness of stars. She placed a light bulb at different distances along a meter stick and measured the brightness of the light with a light meter. On next side you will see Luisa’s data.  What trends do you notice?  What is the relationship between light intensity and distance?

Luisa’s Data Table Effect of Distance on Light Distance (cm) Meter Reading (luxes)

Space Measurement Parallax  Astronomers measure the apparent shift in its position when viewed from two different angles  Light Year Because of the vast dimensions of space we use Light Years when calculating Distances Because of the vast dimensions of space we use Light Years when calculating Distances Light travels at 3.00 x 10^8 m/s Light 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?

Parallax

Star Properties  Color Indicates Temperature Indicates Temperature Hot stars are blue/white Hot stars are blue/white Cool Stars look orange/red Cool Stars look orange/red Yellow Stars indicate medium temperature Yellow Stars indicate medium temperature Our Sun is a medium temperature starOur Sun is a medium temperature star

Star Properties  Spectrum View Star light with a spectroscope you can break up the visible light into a “fingerprint” View Star light with a spectroscope you can break up the visible light into a “fingerprint” Spectrum indicates elements in the star’s atmosphere Spectrum indicates elements in the star’s atmosphere 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 Stars Ejnar Hertzsprung and Henry Russell  Graphed Stars by Temperature and Absolute Magnitude  Called it the H-R Diagram

H-R Diagram Main Sequence (MS)  Diagonal Band  Upper Left Hot Blue. Bright Stars Hot Blue. Bright Stars  Lower Right Cool, Red, Dim Stars Cool, Red, Dim Stars  Middle Average Yellow Stars Average Yellow Stars  Dwarfs and Giants 10% of Stars that Don’t Fit on MS 10% of Stars that Don’t Fit on MS

Production of Energy Nuclear Fusion  Joining of Atoms  Proton – Proton Chain Starts with two Protons and Ends with Helium Starts with two Protons and Ends with Helium ENERGY ENERGY

Stellar Evolution

1. Nebula contraction Temperature increase Temperature increase At 10 million Kelvin Fusion Begins At 10 million Kelvin Fusion Begins 2. Balancing of Heat and Pressure This is Called steady State Equilibrium This is Called steady State Equilibrium Balance is lost when Hydrogen Core is used up Balance is lost when Hydrogen Core is used up Core contracts and heats up causing outer layers to expand and cool Core contracts and heats up causing outer layers to expand and cool Star becomes a giant Star becomes a giant Helium nuclei fuse to form a core of Carbon Helium nuclei fuse to form a core of Carbon

Stellar Evolution 3. White Dwarf Helium is exhausted and outer layers of giant escape Helium is exhausted and outer layers of giant escape Core contracts into a hot dense star Core contracts into a hot dense star 4. Supergiants Massive stars causes higher temps and greater expansion Massive stars causes higher temps and greater expansion Fusion stops Fusion stops Core crashes inward causing the outer part to explode into a Supernova Core crashes inward causing the outer part to explode into a Supernova

Stellar Evolution 5. Collapsed Core of a Supernova may form a neutron star of extremely high density 6. A Tremendously Big Supernova Core can collapse to a point of no Volume – a Black Hole Gravity is so strong not even light can escape Gravity is so strong not even light can escape Beyond the Event Horizon gravity operates as normal Beyond the Event Horizon gravity operates as normal

Interstellar Nursery

Life Cycle of Our Sun

1987 Super Nova

 ray.org/labs/star_life/starlife_main.html ray.org/labs/star_life/starlife_main.html ray.org/labs/star_life/starlife_main.html  activity2 activity2 activity2  urces/CSA_Astro9/files/multimedia/unit2/star_lifecycle/st ar_lifecycle.html urces/CSA_Astro9/files/multimedia/unit2/star_lifecycle/st ar_lifecycle.html urces/CSA_Astro9/files/multimedia/unit2/star_lifecycle/st ar_lifecycle.html  al_features.html

Black Hole