Friday, July 4, 2008

Happy Anniversary!

Happy 958th anniversary to the gorgeous Crab Nebula, whose supernova was first observed by Chinese, Japanese, and Arab astronomers on July 4th, 1054.

According to Wikipedia:

When SN 1054 occurred, it was visible in the day for 23 straight days and the supernova was visible in the night sky for 653 days.
There is evidence that the Mimbres and Anasazi Indians in North America saw SN 1054.
According to the High Altitude Observatory at the National Center for Atmospheric Research:

The pictograph shown on this slide was painted on a horizontal overhang six meters off the ground, located on an East-facing cliff face five hundred meters Northeast of the ruin Peñnasco Blanco, in Chaco Canyon. Strong circumstantial evidence points to the pictograph being a depiction of the 1054 supernova. The crescent is the Moon, the star shape to its left the supernova, and the hand (life-size) is taken to indicate that the site is sacred. Calculations of the Moon's orbit back to 5 July 1054 have shown that the moon was waning, just entering first quarter. These calculations also indicate that at dawn on 5 July 1054 in the American Southwest, the moon was within 3 degrees of the supernova, and its crescent oriented as on the pictograph (provided the pictograph is viewed looking up with one's back to the cliff, as the authors of the pictograph most likely did). With the apparent width of the moon being about half a degree, this pictograph comes basically as close as it possibly could to being a true scale rendition of the 1054 supernova seen in conjunction with the waning moon.

On the nearly vertical cliff face below the supernova a Sun-symbol can be seen, painted in pale yellow over a much faded red background. This, combined with a clear view on the mesa top to an eastern horizon suitable for calendrical purposes, might well indicate that the site was also a solar-observing station. From there, the Peñasco Blanco Sun-priest perhaps first noticed the supernova prior to a sunrise observation. Given how rare such an event must have been, it is then conceivable that he might have wanted to record the event. Over a dozen other examples of rock art possibly representing supernova 1054 (i.e., bright "star" close to a crescent Moon) can be found throughout the Southwest, but few are as astronomically convincing as this pictograph.
A pulsating radio source, now known as the Crab Pulsar, lies in the heart of the Nebula.
Also, today is the second anniversary of the launch of STS-121, the first space shuttle launch to occur on the 4th of July. You may recall there were some tense moments following the discovery that foam had fallen off during the STS-121 launch and could have potentially damaged the vehicle. By using new cameras and sensors on the robotic arm, NASA was able to ascertain that the damage was not significant. Discovery landed safely on July 17th.

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