Astronomy Research Project

Astronomy Research Project By Christina Ciganik

Star Brightness and Distance from EarthAbsolute 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 1st 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 DiagramTemperature Versus Absolute Magnitude

HR Diagram Luminosity Temperature

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

Main Sequence (cont.) • 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

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 http://www.astro.ubc.ca/~scharein/a311/Sim/hr/HRdiagram.html http://aspire.cosmic-ray.org/labs/star_life/hr_interactive.html

Bibliography--get full info • Gareth, James. "The Hertzsprung Russel Diagram." HR Diagram. 23 May 2006 <http://freespace.virgin.net/gareth.james/3__objects/HR_Diagram/hr_diagram.html>. • "Hertzsprung-Russell Diagram." Wikipedia the Free Encyclopedia. 17 May 2006. Wikimedia Foundation, Inc. • "Interpreting the HR Diagram." How Hot is That Star? 15 Dec. 1997. University of California. 18 May 2006 <http://www.smv.org/jims/l6a.htm>. • "Main Sequence Stars." 18 May 2006 <http://www.astro.umd.edu/education/astro/stev/main_seq.html>. • Smith, Gene. "The Hertzsprung-Russell Diagram." Gene Smith's Astronomy Tutorial. 21 Apr. 1999. University of California, San Diego. 19 May 2006 <http://cassfos02.ucsd.edu/public/tutorial/HR.html>. • Soper, Davison E. "Hertzsprung-Russell Diagram." nstitute of Theoretical Science. 22 May 2006 <http://zebu.uoregon.edu/~soper/Stars/hrdiagram.html>. • Spaulding, Nancy E., and Samuel N. Namowitz. Earth Science. Evanston Illinois: McDougal Littell, 1994. 379-382.

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Astronomy Research Project