2021-04-28

How do larger stars explode? The study said that titanium-containing bubbles caused a strong explosion

By yqqlm yqqlm

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How do larger stars explode? The study said that titanium-containing bubbles caused a strong explosion

The different colors in this new image mainly represent the elements Chandra detected in Cassiopeia A: iron (orange), oxygen (purple) And the amount of silicon (green) compared to magnesium. Titanium (light blue) previously detected by NASA’s NuSTAR telescope at higher X-ray energies is also shown. These Chandra and NuSTAR X-ray data are superimposed on the illumination image of the Hubble Space Telescope (yellow).

When the nuclear power source of a massive star is exhausted, its center will collapse under the action of gravity and form a dense star core called a neutron star, or less often, a black hole. When a neutron star is produced, the interior of the collapsed massive star will bounce off the surface of the star’s core, reversing the implosion.

The heat from this catastrophic event created a shock wave–similar to the sonic boom of a supersonic jet–that spreads outward on the rest of the destined star, and is produced by a nuclear reaction along the way. new element. However, in many computer models of this process, energy is quickly lost, and the shock wave’s outward journey stops, preventing the supernova from exploding.

Recent three-dimensional computer simulations have shown that neutrinos–subatomic particles of very low mass–drive bubbles in the process of creating neutron stars, accelerating away from the center of the explosion. These bubbles continue to push the shock wave forward, triggering a supernova explosion.

This new Chandra research report said that the finger-like structure pointing away from the explosion site, in the lower right, contained titanium and chromium, which matched the orange iron fragments seen. The titanium discovered by Chandra is a stable isotope, which means that the number of neutrons in its atoms means that it will not be radioactively changed into another lighter element. The titanium previously detected in Cas A with NuSTAR is an unstable isotope, which is converted to scandium and then calcium in a time frame of about 60 years. The figure does not show the stable titanium isotopes discovered by Chandra.

The conditions required to produce chromium and stabilize titanium in a nuclear reaction, such as temperature and density, match the bubbles in the three-dimensional simulation that drives the explosion.

This new study strongly supports the idea that neutrinos drive explosions to explain at least some supernovae.

Cassiopeia A is located in our Milky Way, about 11,000 light-years from the Earth. It is one of the youngest known supernova remnants in the Milky Way, with an age of about 350 years. Astronomers used the Chandra observation time of more than 1.5 million seconds, or more than 18 days, of Cassiopeia A between 2000 and 2018 for this study.