The background for this site was created from an image of the Cartwheel galaxy found at Jim DeLine's site, which is the copyright property of Jim DeLine and The Association of Universities for Research in Astronomy.This page was created for ES 111 Earth Science Lab, at Emporia State University, Emporia, Kansas, USA.  It was written in conjunction with the lab on the Geocentric/ Heliocentric theories from the Introduction to Earth Science Lab book, written by: Paul Johnston, Susan Aber, and Hengchun Ye (1998).  Edina, MN: Burgess Publishing.

 Intrinsic Properties of Stars:

Brightness
Temperature
Mass
Images
Constellations
References
 

Brightness

Hipparchus, in the second century B.C., classified stars by apparent brightness into six categories, with one being the brightest and six the dimmest (Lutgens 569). The apparent brightness of a star is determined by three factors: how big, how far away, and how hot the star is.   The first factor is how big the star is.  The size a star appears, as observed from Earth, affects the brightness or apparent magnitude.  The sun is the largest star, as viewed from Earth, although there are many stars in space that are much bigger than our Sun. The reason other stars look so small is because they are so far away. The sun is an average star compared with other stars in the universe and is one of some 200 billion within the Milky Way galaxy.   The Sun appears to be brighter and larger than any other stars simply because of the close distance to Earth. 
 

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Temperature

The temperature of the star also determines the brightness, which can be determined from the color of the star.  If the star is blue in color then it is a hot star that radiates short wave lengths, creating a heat of greater than 30,000 K.  If the star is red it is cooler with longer wave lengths andhas a temperature less than 30,000 K.  If a staris between 5,000 and 6,000 K it is yellow. 

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Mass

The mass of a star can be determined if it is gravitationally attached to a partner, or binary star.  Binary stars are a pair of stars that orbit each other attaching themselves by a common point.  This point is called the center of mass.  If one star is more massive than the partner star then the center of mass is closer to the bigger star and the stars will become two units.  An example of a binary star is in the constellation Big Dipper.  

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Images
 

                                          

These Hubble telescope images and more can be found at Jim DeLine's site.They are the copyright property of Jim DeLine and The Association of Universities for Research in Astronomy. The image on the left is Comet Hyakutake when it passed Earth 9.3 million miles away. The image in the center is Egg Nebula, which shows the light beams emerging from a hidden star. The image on the right appears to be an orange star because of the great distance from Earth and the resulting red shift of light.

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Constellations

As early as 5000 years ago, people became fascinated with the stars and began to name the patterns they saw. Many were named after mythological characters or great heroes.  In today's world the whole sky is one constellation. Constellations are an apparent group of stars that may be hundreds of light years away.  Constellations may have been created for religious beliefs or some other purpose.  Some people think that they tell the farmers when to plant or harvest the crops.  They can also tell a story, such as the Orion constellation, which is thought by some to be a man in a battle uniform with a sword on his belt.  The sky is presently divided into 88 constellations.  They have been made up by poets, farmers, and astronomers.  When you look up at the sky there are thousands of stars that can give you inspiration and pleasure, as well as a view of the history of the universe. 
 
 

Winter Constellations by Richard Blessing

Now the winterest constellations
rattle their cold chains
against my roof.
 
This evening
I find all I have lost in the sky.

There is the basket I raised for my son
and there is the net of stars raining down.

There the bright cloud of his mother's hair
vanishes forever all night long.
 
North of Lake Washington my father climbs
ghostly in the hunting fields.  His eyes
are hollows were nothing shines.

He says he has nothing to say to me.

Someone has carved a deer on the wall of moon.

This is the stippled history of desire.
This is winter and evening, framed by trees.

Tonight the Cascades circle like a well
where rings like water open out and out
until they break on that black rock of space
where the bound princess writhes in links to stars
and lures the sea beast up from the sea.
 

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