Birthday Eclipse

Every month has a long list of birthdays of famous people. December is no exception.  December is well known for the birthdays of Ozzy Osbourn, Joseph Conrad, Walt Disney, Humphrey Bogart and Jesus of Nazareth (although the historical accuracy of this last one cannot be verified).  Likewise, December is also the birth month for a number of famous astronomers.  Three of these are well known names in the annals of history.  Two are less well known by name but still important in their contribution to the science.


The first famous astronomer birthday is that of Tycho Brahe.  Tycho was born on December 14, 1546, in Denmark.  Tycho was the world’s foremost naked eye observer, making all of his observations years before the telescope was invented.  Tycho used sophisticated, non-magnifying instruments to carefully measure the positions of stars.

Johannes Kepler was born on December 27, 1571, in Germany.   By using Tycho’s information of the positions of the planets, he formulated his three laws of planetary motion.  The first law states that the orbits of planets are ellipses.  The second is that as a planet orbits the sun, it sweeps out equal areas in equal intervals of time.  The third law states that the time needed for a planet to orbit the sun is related to how far it is from the sun.  Kepler’s laws added additional evidence that the sun, not the Earth is at the center of the solar system.  Yet it would take our next famous birthday to explain how the system worked.

Isaac Newton was born on December 25, 1642, exactly one year after the death of Galileo.  While Newton is most famous for his work in physics, it is his universal law of gravitation that is of interest to astronomers.  Newton’s law of gravitation states that the amount of force between two objects is related to their masses and how far apart they are.  Thus, a large object exerts a large force on a small object but the farther apart the two objects are, the weaker the force becomes.  This law explained how planets orbit the sun and how the moon orbits the Earth.  It also provided a way to confirm Kepler’s three laws.

Our final December birthday belongs to Annie Jump Cannon on December 11, 1863.   Cannon is credited with creating the Harvard Classification Scheme which was the first attempt to organize and classify stars based on their temperature.  Today the hottest stars are classified as type O while the coolest stars are classified type M.  In this scheme our star, the sun, is a type G star.

If you are tired of celebrating December astronomical birthdays, take time on the night of the 20th to watch for a total lunar eclipse.  Begin watching the full moon about 10:45 PM.  By 11:30 the moon will be noticeably darker and by 11:40 it will have taken on a redish or browning color.  This is the beginning of totality, when the moon passes through the darkest part of the Earth’s shadow.  Totally should last until about 3:00 am.  By the time the moon sets the eclipse will be over.

December is full of famous birthdays.  Some are famous because they are great actors or writers.  Some are famous because they were great thinkers or philosophers.  Some are famous because they contributed to our modern view of our solar system and our universe.  December 2010 also adds a rare and wonderful event, an eclipse.  So look out, because although next december you will still be able to celebrate the birthdays, there will not be a lunar eclipse.

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