July 4th, 955 Years Ago

Long before the American colonies declared independence from Great Britain, there was a July 4th that had fireworks of a different sort

The year was 1054. Henry III was the Holy Roman Emperor. The Byzantine Empire was reconquering Syria, Mesopotamia and Palestine. Led by Leif Ericson, the Vikings established settlements in North America. China's population was swelling to 100 million.

And on July 4th of that year, a supernova -- the massive explosion of a star -- in the Taurus constellation was witnessed around the world. People were likely mesmerized by the strange light that remained in the sky for months, so bright that it could be seen in daylight. Chinese and Arab astronomers recorded the event.

The remnants of that moment can be seen today. Those remnants make up the famous Crab Nebula, a supernova remnant and pulsar wind nebula that is 6,500 light-years away. Eleven light-years across, the Crab Nebula is the strongest regular source of X-ray and gamma ray energy in the Earth's sky.

Now that's a serious fireworks display.

GET INVOLVED

• Sign a petition to add the option for US taxpayers to contribute to NASA on the IRS 1040 tax form
• See what's in the sky tonight
• Download Google Earth 5.0, which has an interactive map of the entire surface of Mars
• Buy a beginner telescope from the Discovery Channel store ($99.00)

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image: This is a mosaic image, one of the largest ever taken by NASA's Hubble Space Telescope of the Crab Nebula, a six-light-year-wide expanding remnant of a star's supernova explosion. The newly composed image was assembled from 24 individual Wide Field and Planetary Camera 2 exposures taken in October 1999, January 2000, and December 2000. The colors in the image indicate the different elements that were expelled during the explosion. Blue in the filaments in the outer part of the nebula represents neutral oxygen, green is singly-ionized sulfur, and red indicates doubly-ionized oxygen. (credit: NASA)