A short historical look at supernovae

Though observed supernovae occur many light years away from our home on Earth, they have found their way into our history and hearts. The term ``nova'' meaning ``new'' might seem like an ironic descriptor of a dying star, merely named this way because the increase in luminosity from an old star to a supernova is so great that the supernova appears to be a new star.  Perhaps the term is an apt one, however. Though supernovae occur at the end of a star's existence, they can also symbolize potential for new star forming regions. Supernovae seem to have a sense of hope in destruction about them.

Not surprisingly, we have been fascinated by these dramatic events in the sky throughout history. The first recorded supernova, observed in A. D. 1006 and recorded in Europe, China, Japan, Egypt, and Iraq, was "a little more than a quarter of the brightness of the moon" according to Egyptian student Ali Ridwan. Just 48 years later, another "guest star", which was also bright enough to be seen in the day, appeared in Taurus, and left behind the elegant crab supernova remnant for us to observe today.

Historic writings suggest that these explosions were both beautiful and terrifying to the cultures who witnessed them. An Arabic medical textbook from A. D. 1242 connected the A. D. 1054 supernova to an outbreak of the plague, stating that the "spectacular star... caused an epidemic to break out in Old Cairo when the Nile was low.''  Upon hearing that the public believed the A. D. 1006 supernova to be an omen of famine, the Chinese Director of the Bureau of Astronomy, Chou K'o-ming, countered general alarm by announcing the new star to be an omen of prosperity occurring during the reign of a very wise leader - a smart career move which soon got him a promotion.

Pictographs found in New Mexico (pictured below) are thought to depict the 1054 supernova.

Five hundred years later, in 1572, Tycho Brahe observed very bright "nova stella'' in the constellation of Cassiopeia. He gave a confident account of the experience in his book De Nova Stella, in which he wrote:

``I noticed that a new and unusual star, surpassing the other stars in brilliancy, was shining almost directly above my head; and since I had, almost from boyhood, known all the stars of the heavens perfectly (there is no great difficulty in attaining that knowledge), it was quite evident to me that there had never before been any star in that place in the sky.'' -Tycho Brahe

Though images such as the Hubble Deep Field suggest that it is quite a bit harder to know all of the stars than Brahe claimed, Brahe's supernova observation signified a cultural turning point, challenging the early Renaissance belief that the stars did not change. The philosophies of that culture would be thoroughly turned upside down by yet another supernova in 1604 observed by Brahe's student, Kepler.

Since Brahe and Kepler's discoveries, we have not observed another supernova in our own galaxy. Fortunately, many spectacular supernovae have been found in surrounding galaxies.  The funny looking character pictured below, Zwicky, found over a hundred supernovae. His classifications pioneered our modern understanding of how supernovae occur.

Recently, in 1994, a particularly beautiful Type Ia supernova was found near the spiral galaxy NGC 4526 (pictured below). SN 1994D was found just outside the galaxy disk, and appeared almost as bright as the galaxy core.

The mechanisms that drive supernovae explosions are quite amazing. Even more incredible to me is the amount of understanding astronomers have gathered about these processes with such seemingly limited information - simply electromagnetic waves telling the story of an explosion from the distant past.