"This image combines data from four space telescopes to create a multi-wavelength view of all that remains of RCW 86, the oldest documented example of a supernova. Chinese astronomers witnessed the event in 185 A.D., documenting a mysterious "guest star" that remained in the sky for eight months. X-ray images from NASA's Chandra X-ray Observatory and the European Space Agency's XMM-Newton Observatory were combined to form the blue and green colors in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova.
Infrared data from NASA's Spitzer Space Telescope and WISE, Wide-Field Infrared Survey Explorer, shown in yellow and red, reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy.
By studying the X-ray and infrared data, astronomers were able to determine that the cause of the explosion was a Type Ia supernova, in which an otherwise-stable white dwarf, or dead star, was pushed beyond the brink of stability when a companion star dumped material onto it. Furthermore, scientists used the data to solve another mystery surrounding the remnant - how it got to be so large in such a short amount of time. By blowing away wind prior to exploding, the white dwarf was able to clear out a huge "cavity," a region of very low-density surrounding the system. The explosion into this cavity was able to expand much faster than it otherwise would have.
This is the first time that this type of cavity has been seen around a white dwarf system prior to explosion. Scientists say the results may have significant implications for theories of white-dwarf binary systems and Type Ia supernovae.
RCW 86 is approximately 8,000 light-years away. At about 85 light-years in diameter, it occupies a region of the sky in the southern constellation of Circinus that is slightly larger than the full moon. This image was compiled in October 2011."Source: NASA
Ian Stewart is a mathematician at the University of Warwick in the United Kingdom. His new book "In Pursuit of the Unknown" is published by Basic Books in the United States in March. In the United Kingdom it is available from Profile Books with the title "Seventeen Equations That Changed the World."
I was one of those annoying kids who actually liked equations. I collected them in a notebook. I loved the way you could plug a few numbers into an equation and find out how bright the Sun would be if you were standing on Pluto. Or work out how big a rainbow looks from the refractive index of water and the time of day.
I realize I am a rarity in that respect. Stephen Hawking’s publishers allegedly told him that every equation he put into his runaway bestseller "A Brief History of Time" would halve its sales. So, if he’d left out Einstein’s E=mc2, he would have sold another 10 million copies. But his publishers had a point. Although the great equations have had more impact on humanity than all the kings and queens in the history books put together, they can look very off-putting.