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Around July 4th In 1054, Chinese astronomers recorded a “guest star” that shone so brightly that it could be seen in broad daylight for 23 days. It is made up of the remains of this ancient supernova Crab Nebula, which has long been of great interest to astronomers. Some have hypothesized that SN 1054 (as it is now known) was the first strange new type of supernova described by physicists 40 years ago. A team of astronomers has now identified a second supernova, called SN 2018zd, which meets all the criteria for this new type, according to new paper published in the journal Astronomy of Natureso we provide an essential link in our knowledge of stellar evolution.
“The term ‘Rosetta Stone’ is often used as an analogy when we find a new astrophysical object, but I think it is appropriate in this case.” said author Andrew Howell Las Cumbres Observatory (LCO). “This supernova literally helps us decode records of thousands of years of cultures around the world. And one thing we don’t fully understand is the Crab Nebula, which helps us connect with something else that has tremendous modern records. This supernova is teaching us about basic physics in the process: how how some of the neutron stars are made, how extreme stars live and die, and how the elements we form are created and scattered throughout the universe. “
There are two known types supernova, depending on the mass of the original star. A supernova that collapses the iron core occurs with massive stars (greater than 10 solar masses), causing them to explode so violently that it causes a huge explosion and disaster. The temperature and pressure are so high that carbon begins to fuse at the core of the star. This stops the collapse of the nucleus, at least temporarily, and this process continues again and again with progressively heavier atomic nuclei. (Most of the heavy elements in the periodic table were born in living supernova furnaces that were massive stars that exploded.) When the fuel is finally completely depleted, (by then) the iron core falls into a black hole or neutron star. .
Then there is the thermonuclear supernova. Smaller stars (about eight solar masses) gradually cool down to become dense dense cores of ash known as white dwarfs. If a white dwarf that has run out of nuclear fuel is part of a binary system, it can remove matter from its partner by adding mass to its core until it reaches temperatures as high as carbon fusion.
In 1980, Japanese physicist Ken’ichi Nomoto of the University of Tokyo theorized that there could be a third type of intermediate: a supernova called “electron capture”, a star that does not have enough weight to produce an iron core. -collapse supernova, and yet it is not light enough to prevent its core from falling completely. Instead, stars stop the fusion process when their nuclei are made up of oxygen, neon, and magnesium. In this scenario, the electrons obtain neons and magnesium under the influence of the nucleus, so that the nucleus shrinks under its weight. The end result is a supernova.
Since Nomoto first proposed supernovae to capture electrons, theorists have relied on their work to identify six key features: stars should have a large mass; they should lose a large part of that mass before they explode; the mass should have an unusual chemical composition; the resulting supernova should be weak; there should be little radioactive fallout; and the nucleus should contain elements rich in neutrons.
SN 2018zd was first detected in March 2018, 31 million light-years away in a galaxy known as NGC2146. The team was probably able to identify the pioneering star by exploring archival images taken by the Hubble Space Telescope and the Spitzer Space Telescope. They continued to collect data on SN 2018zd over the next two years. Astronomers at UC Davis helped conduct spectral analysis, which was crucial evidence that it was a supernova to capture electrons.
When they combed the published data about the supernovae released so far, the team indicated a handful that met some of the predicted criteria. But only SN 2018zd marked the six boxes. Because of this discovery, astronomers are even more certain that the supernova that captured the Crab Nebula in 1054 was also an electron-trapping supernova, although it has long since occurred to make a definitive confirmation. This would also explain why SN 1054 is so bright: the materials from the explosion are likely to collide with the material thrown by the previous star, the same thing that happened with SN 2018zd.
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