November Super Nova, 400 Years Later

by Rod Kennedy

November is an exciting month.  Football season is in full swing, Thanksgiving is approaching for many in the United States, and several cultural end-of-year celebrations are close at hand.  The night skies can be exciting, too. As the nights get longer, there are more hours of darkness to enjoy, even if the temperature is starting to get a little cool.  Yet the November skies we see are not nearly as exciting as they were over 400 years ago, when a new star made its appearance.

On a clear November evening in 1572, November eleventh to be precise, the great Danish astronomer Tycho Brahe was observing the sky and taking measurements.  Suddenly he noticed a very bright star in a place where no star had previously been visible in the constellation Cassiopeia.  Tycho was an experienced observer and had mapped the night sky with precision that still astonishes us today.  Yet this star had never been observed or recorded before.  In his amazement, Tycho required the confirmation of two of his assistants to verify that the star was really there.  Over the next eighteen months the star slowly faded to invisibility.

Today we know the star Tycho saw was really a super nova.  Super novae are old stars that blow themselves to pieces at the end of their life cycles.  Tycho’s Star was so bright it out shined the planet Venus and was even visible in the daylight hours.  As it cooled and shrank it gradually dimmed, changing from white to yellow to red.  Today we know that Tycho’s Star was about 10,000 light years from Earth.  The remains of this huge explosion can still be found in Cassiopeia, but a telescope is needed to find it.  Just thirty years later another super nova was observed, this time by Tycho’s assistant Kepler.

While Tycho’s Super Nova was the first of its kind to be observed by Europeans, it was not the first ever observed by humans.  In the year 1054, Chinese astronomers recorded what they called a “guest star” in the constellation we know as Taurus the Bull.  The Chinese recorded many such “guest stars” and it is even possible that our ancient ancestors observed the blast that created the Veil Nebula in Cygnus more than then thousand years ago.

Super novae remnants show us the death of stars.  Yet November gives us a chance to see the infancy of stars as well.  Looking East just after sunset we find the Pleiades or Seven Sisters in Taurus the Bull.  This cluster of stars is less than 100 million years old.  The stars are blue, which means they are very hot.  Very hot stars do not live as long as cooler stars and therefore the Pleiades are fairly young.  If we compare these stars to Aldebaran, the brightest star in Taurus, we find that it is a red-orange star.  The color, combined with its size and spectrum tell us that Aldebaran is nearing the end of its life.  In fact it is possible that Aldebaran may end its life as a super nova as well.

We normally think of the skies as constant and unchanging.  The constellations remain the same throughout a human lifetime.  Even the paths of the planets are regular and predictable.  Yet, as Tycho discovered, sometimes the night sky surprises us – so keep looking up, because the next super nova might occur at any moment.

November 2010 Chart

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