A Matrix Knot Invariant by Alexander J. W.

By Alexander J. W.

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For a short time a supernova may produce as much energy as an entire galaxy of 100,000 million stars. In its center remains what is left of the core of the star. If this is less than three times the mass of the Sun, it will be converted into a neutron star. The pressure of the supernova explosion is so immense that all the protons and electrons in the nucleus combine to form neutrons. A neutron star has all the mass of a star compressed into a diameter of perhaps 10 kilometers. Surrounding the neutron interior is a thin crust of iron and, above that, a dense atmosphere just a few centimeters thick!

Astronomers could measure the speed of rotation of galaxies at different distances from the center. In the Andromeda Galaxy, for example, they could see that stars in the center were rotating rapidly around the center and could work out how massive the center of the galaxy had to be to allow them to move that fast. They could also work out from the brightness of the center of the galaxy how many stars there were there. In every case, it was found that the stars rotated far more rapidly than could be explained by the mass of visible stars.

From there it was a simple step to think of yet-more-compact objects. 30 Cosmological Enigmas The second crucial moment was the launch of the x-ray satellite Uhuru on December 12, 1970. It was launched on Kenyan independence day from the San Marcos launch platform off the coast of Kenya (hence, the name uhuru, the Swahili word for “freedom”). Uhuru had the task of mapping the x-ray sky, searching for objects that emitted x-rays. The satellite found 339 sources that were at least one-thousandth as bright as the Crab Nebula.

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