A black hole of tremendous mass, equivalent to those of millions or even billions of stars, which is believed to exist and occupy the centers of many galaxies. The supermassive black hole residing in
the center of our Milky Way Galaxy is the object Sgr A* with a mass of 4 x 10^6 solar masses within a radius of 100 astronomical units.
A violent stellar explosion which blows off all or most of the star's material at high velocity leaving a compact stellar remnant such as a neutron star or black hole. At maximum light, the supernova
can have luminosity about 108 or 109 times the solar luminosity. The phenomenon results from the later evolution of stars when an instability sets in the core following the nucleosynthesis of iron. In massive stars, the supernova occurs when the star has used up all its available nuclear fuel and it reaches a lower energy state through gravitational collapse to form a more compact object. In white dwarfs forming binary systems, accretion of mass onto the surface of a neutron star can be sufficient to take the star over the upper mass limit for stability as a white dwarf. Consequently, the white dwarf collapses in a supernova explosion to form a neutron star. There are several supernova types.
A violent stellar explosion which blows off all or most of the star's material at high velocity leaving a compact stellar remnant such as a neutron star or black hole. At maximum light, the supernova
can have luminosity about 108 or 109 times the solar luminosity. The phenomenon results from the later evolution of stars when an instability sets in the core following the nucleosynthesis of iron. In massive stars, the supernova occurs when the star has used up all its available nuclear fuel and it reaches a lower energy state through gravitational collapse to form a more compact object. In white dwarfs forming binary systems, accretion of mass onto the surface of a neutron star can be sufficient to take the star over the upper mass limit for stability as a white dwarf. Consequently, the white dwarf collapses in a supernova explosion to form a neutron star. There are several supernova types.
The body of expanding gas ejected at a speed of about 10,000 km s^-1 by a supernova explosion, observed as a diffuse gaseous nebula, often with a shell-like structure. Supernova remnants are generally
powerful radio sources. The evolution of the SNR can be divided into different phases according to the dominant physical processes. Simplified models are made for the first stages, to get an idea of typical time scales, expansion velocities, and sizes. The three main phases are: 1) the free expansion phase, 2) the Sedov-Taylor phase, and 3) the snowplow phase.
The body of expanding gas ejected at a speed of about 10,000 km s^-1 by a supernova explosion, observed as a diffuse gaseous nebula, often with a shell-like structure. Supernova remnants are generally
powerful radio sources. The evolution of the SNR can be divided into different phases according to the dominant physical processes. Simplified models are made for the first stages, to get an idea of typical time scales, expansion velocities, and sizes. The three main phases are: 1) the free expansion phase, 2) the Sedov-Taylor phase, and 3) the snowplow phase.