A supernova occurs when a star explodes. This can occur when a massive star runs out of fuel for nuclear fusion and undergoes a gravitational collapse into a neutron star or black hole. Another way that it can occur is when two white dwarf stars merge, or one white dwarf star parasitically accumulates mass from a nearby star.
When the star explodes, it does not have to explode symmetrically. The explosion could be asymmetrical. In the Large Magellanic Cloud (LMC), a nearby irregular galaxy, the Chandra X-Ray observatory has found evidence of just such an asymmetrical supernova. NASA looked at the remnant of N49 using both Chandra and Hubble images. These can be seen in the first image to the right.
Chandra looked at the remnant of N49 in the X-Ray spectrum and found two interesting features. These can be seen in the second image to the right. The first feature is a small envelope of gas, colored in blue, can be seen in the image to the lower right. This bullet of gas is traveling at 5 million miles per hour.
The second feature is a Soft Gamma ray Repeater (SGR). This is a neutron star that emits gamma rays and X-rays. Do you see how off center the neutron star is? If this SGR is part of the stellar core from the supernova, then the kick from the asymmetrical supernova has sent it careening off into space at an approximate speed of 490 miles per second. While that is fast, it is only a fraction of the speed of light.
The Hubble Space Telescope looks at our universe at optical wavelengths, and is shown in the third image to the right. The optical data from Hubble shows up in the image as yellows and purples. This is where the shockwave from the asymmetrical supernova is interacting with nearby clouds of gas.
The asymmetrical supernova remnant, N49, is approximately 160,000 light years from Earth. Using the data from Chandra and Hubble, astronomers think that the light from the supernova reached Earth approximately 5,000 years ago.
via : Chandra Observatory
The light of the supernova reaching earth 5,000 years ago is different from the supernova occurring 5,000 years ago.
Astronomers think that the light from the supernova reached Earth approximately 5,000 years ago. Astronomers also think that the actual supernova occurred approximately 165,000 years ago. I use the terms “think” and “approximately” because there is always some uncertainty in the measurements.
It is not clearas to how we are able to perceive and believe that the supernova occured 5000 years back while we are 160000 lightyears away.
During the last 5K years light could travel only 3% of the total distance. Laymen like me need elucidation.