The ancient Greek philosopher Aristotle declared the heavens were perfect and unchanging, and his view went unchallenged for nearly 2,000 years. But keen-eyed renaissance astronomers like Tycho Brahe discovered stars that varied in brightness. The science of variable stars was born.
Galaxy Shapes: Another Legacy of Edwin Hubble
Spring is the time to peer up and out of the plane of our Milky Way at fields of distant galaxies in Leo, Virgo, and Coma Berenices. Every galaxy you see, and nearly every one of the billions of galaxies in the universe conforms to one of four basic galaxy shapes first outlined by Edwin Hubble in the 1930’s.
Stellar Magnitude: Understanding the Brightness of Stars and Planets
Astronomers use a numerical measure called “magnitude” to describe the brightness of stars, planets, and other objects in the night sky. Here’s how it works.
By convention, brighter objects have a smaller numerical value of magnitude than fainter objects. So a star with magnitude 4 is brighter than a star with magnitude 5, for example. It’s a little like a ranking system, where brighter stars are assigned a smaller number. Again, by convention, stellar magnitudes are defined so that an object with magnitude 1.0 is 100 times brighter than an object with magnitude 6.0. So each step of 1.0 in magnitude is the “fifth root” of 100, which is a factor of 2.512. That means a star of magnitude 3.0 is 2.512 times as bright as a star of magnitude 4.0, which is 2.512 times as bright as a star of magnitude 5.0, and so on. Try it yourself, if you have a calculator handy.
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