What is remnants of a type 2 supernova?

Answer 1

After a star has burned out its fuel supply, exhausting the hydrogen and helium that are being fused, one of three things can happen, depending on the mass of the star.

For a star with a mass similar to the Sun, it will turn into a white dwarf and radiate its remaining heat into space for billions of years. It will end its life as a black dwarf. (Though none exist at the moment, as the universe is not old enough).

For larger stars, depending on its chemical composition and temperature, the star explodes as a supernova and usually collapses into a neutron star. If the remaining mass is large enough, the pressure will be insufficient to stop a total collapse, and the star will become a black hole.

A supernova remnant [See Link] is the structure resulting from the massive explosion of a star in a supernova. The remnant is bounded by an expanding shock wave, including ejected material from the explosion and the interstellar material it sweeps up along the way.

The supernova explosion expels much or all of the stellar material with velocities around 3,000 km/s. When this material collides with the surrounding circumstellar or interstellar gas, it forms a shock wave that can heat the gas up to temperatures as high as 10 million °K, forming a plasma.

The stages involved are:

# Free expansion of the ejecta, until it sweeps up its own weight in circumstellar or interstellar medium. This can last tens to a few hundred years depending on the density of the surrounding gas. # Sweeping up of a shell of shocked circumstellar and interstellar gas. # Cooling of the shell, to form a thin, dense shell surrounding the hot interior. This is the pressure-driven phase. # Cooling of the interior. The dense shell continues to expand from its own momentum. # Merging with the surrounding interstellar medium. After roughly a million years, it will merge into the general turbulent flow, contributing its remaining kinetic energy to the turbulence. There are three types of remnant:

* Shell-like, such as Cassiopeia A * Composite, where the shell contains a central pulsar wind nebula, such as G11.2-0.3. * Mixed-morphology ("thermal composite") remnants, in which central thermal X-ray emissions are seen, enclosed by a radio shell.

*The illumination of the gases by heating provides the spectacular light-and-shadow appearance of supernova nebulae. It is believed that these dense clouds can become the stellar "nurseries" for further generations of stars.