Diamonds in the Sky
When it starts to get dark each night, which are the first stars you see? The brightest ones, of course! Over 2,000 years ago, Hipparchus developed a numbering system, one through six, based on the apparent magnitude or brightness of the stars he saw from Earth. A first or number one magnitude star was 100 times brighter than the faint stars in the sixth class. Over time astronomers have found some objects can be brighter than a one, so they started using a minus sign to indicate how much light there seemed to be. Do you think there are numbers higher than six? With modern telescopes, stars can be listed up to a thirty! Hipparchus might have been surprised to see astronomers still use the information from his catalog today. Newer books have changed the amounts of a few of his numbers and many, many more stars have been added to his list. Suppose you and your friends are walking after dark and you see a light shining in the distance.
JUST for FUN
Indoor Night Sky
To make an indoor sky, take a large piece of black plastic and draw the night sky on it with a silver paint pen. Use a pencil tip to make a hole for each star in the plastic so your stars will shine from the light outside. Tape the sky over the open end of a large appliance box. You will need a door in the box to get inside.
MAGNITUDE:
The amount of light a star emits or gives off is called its magnitude. Astronomers measure the magnitude of the stars out in the universe by using a number system.
It could be a streetlight or a flashlight. How bright it is doesn't tell you much about the light, if you don't know how far away it is. Modern astronomers have learned how to measure the distance to a star and its apparent magnitude, or how bright it appears to us. They use both of these figures to determine the absolute magnitude or luminosity (true bright-ness) of a star. Scientists pretend that the sun and the other stars are all the same distance from the earth to figure their absolute magnitude. The sun has an apparent magnitude of –26.7 and absolute magnitude of 4.8. See what a difference a little distance makes!
