Astronomy Research Project By Christina Ciganik

Star Brightness and Distance from Earth Absolute Magnitude and Luminosity

Stars Distance from Earth The Sun is the star closest to the Earth at a distance of about 150 million kilometers This distance is one Astronomical Unit (AU) Astronomical units can be used to measure distances within our solar systems

Light Years A Light Year is the distance a single ray of light can travel in space in one year (9.5 trillion kilometers) A single ray of light travels at about 300,000 kilometers per second in space

Luminosity “A measure of the total amount of energy radiated by a star or other celestial object per second.” - ATOE The actual brightness of a star which depends on its size and temperature

Apparent Magnitude Apparent Magnitude – How bright a star appears from Earth’s surface Brightest star is the 1 st magnitude Stars with a weaker brightness have lower magnitudes A strong magnitude is 2.5 times greater than the one after it Does not show how bright a star really is only how bright it appears

Absolute Magnitude Absolute Magnitude is the Apparent Magnitude of a star placed at 32.6 light years away from the sun Lets us compare the stars’ luminosities without the problem of distance

HR Diagram Temperature Versus Absolute Magnitude

HR Diagram Temperature Luminosity

HR stands for Hertzsprung- Russell Danish astronomer Ejnar Hertzsprung and American astronomer Henry Russell discovered the diagram originally

HR Diagram (cont.) “As stars live out their lives, changes in their structure are reflected in changes in their temperatures, sizes, and luminosities” These factors cause them to move on the H-R Diagram.

The HR Diagram shows the basic characteristics of stars and the relationship between absolute magnitude, temperature, and luminosity of them You can use the diagram to find the temperature and brightness of a star

3 Major sections of the HR Diagram Main Sequence Giants and Supergiants White Dwarfs

Main Sequence “A major grouping of stars that forms a relatively narrow band from the upper left to the lower right when plotted according to luminosity and surface temperature on the Hertzsprung-Russell diagram.” -dictionary

The Main Sequence is a stable state where stars shine steadily for a long period of time The greatest amount of stars are on the Main Sequence Stars will spend almost 90% of their lifetime on the Sequence Main Sequence (cont.)

Giants and Supergiants Very Luminous Low surface temperatures Stage in a star’s life after the Main Sequence Not as much time of the star’s life is spent here The two types are blue-white giants and red giants

White Dwarfs Very Dense High surface temperature Last stage before death Very Faint About the size of earth

HR Diagram in Action hr/HRdiagram.html ray.org/labs/star_life/hr_interactive.html

Bibliography--get full info Gareth, James. "The Hertzsprung Russel Diagram." HR Diagram. 23 May "Hertzsprung-Russell Diagram." Wikipedia the Free Encyclopedia. 17 May Wikimedia Foundation, Inc. "Interpreting the HR Diagram." How Hot is That Star? 15 Dec University of California. 18 May "Main Sequence Stars." 18 May Smith, Gene. "The Hertzsprung-Russell Diagram." Gene Smith's Astronomy Tutorial. 21 Apr University of California, San Diego. 19 May Soper, Davison E. "Hertzsprung-Russell Diagram." nstitute of Theoretical Science. 22 May Spaulding, Nancy E., and Samuel N. Namowitz. Earth Science. Evanston Illinois: McDougal Littell,

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