The ejected material is rich in heavy elements synthesised during the explosion making SNII one of the principal sources for heavy elements in the Universe. The general picture for Type II, Type Ib and Type Ic supernovas - also called core-collapse supernovas - goes something like this. All material is © Swinburne University of Technology except where indicated. The formation of a neutron star releases an enormous amount of energy in the form of neutrinos and heat, which reverses the implosion. All but the central neutron star is blown away at speeds in excess of 50 million kilometers per hour as a thermonuclear shock wave races through the now expanding stellar debris, fusing lighter elements into heavier ones and producing a brilliant visual outburst that can be as intense as the light of several billion Suns. Population I stars form about two percent of stars and tend to be formed from heavier elements from previous giant stars. In this way, supernovae contribute to the "life cycle" of the universe- as stars collapse and reach their ends, parts get recycled to help create new stars and objects. The neutrinos produce a huge outward force simply because there are so many of them (they don't usually interact with regular matter). If, however, accretion of matter from a companion star or the merger with another white dwarf, push a white dwarf star over the Chandrasekhar limit of 1.4 solar masses, the temperature in the core of the white dwarf will rise, triggering explosive nuclear fusion reactions that release an enormous amount of energy. Like Type Ib and Type Ic supernovae, SNII are only found in regions of star formation, indicating that they result from the core-collapse of massive stars. The Crab Nebula, a remnant of a supernova observed in 1054 A.D., is the most spectacular example. Black holes are technically only theorized as they can not be directly observed due to the lack of emitted light/radiation (hence the term black hole), but astronomical observations of their possible gravitational effects on nearby systems have led to them being commonly accepted as existing stellar remnants, and products of Type II supernovae. Chandra Podcast: Supernovas: When Stars Die Many things about black holes are still not completely understood due to their complex nature. This research has led to the astounding discovery that the expansion of the universe is accelerating, possibly because the universe is filled with a mysterious substance called dark energy. According to stellar evolution theory, temperatures rise to several billion degrees in the central regions of stars with masses between 140 and 260 suns. Chronicle Article: Blasts From The Past Impact Science This so-called "pair instability" causes violent pulsations that eject a large fraction of the outer layers of the star, and eventually disrupt the star completely in a thermonuclear explosion. Every 50 years or so, a massive star in our galaxy blows itself apart in a supernova explosion. The results of a Type II Supernova are either neutron stars or black holes (explained below), along with a supernova remnant. A Type II, as well as Type Ib and Type Ic explosion, is produced by the catastrophic collapse of the core of a massive star. Infographic: Supernovas & Supernova Remnants This blowing off of layers is normally caused by either a strong stellar wind or the fact that the star is so massive that it has little gravitational control over its outer layers, as in a Wolf-Rayet star. Type Ic has also had its helium layer blown off, so it will not have helium lines in its spectrum either. Centre for Astrophysics and Supercomputing, COSMOS - The SAO Encyclopedia of Astronomy, Study Astronomy Online at Swinburne University. Because of the Pauli Exclusion Principle, the neutrons repel each other and keep in motion, with the sheer number of neutrons creating a force that keeps the object together. Type II Supernovae result from the collapse of massive stars, resulting from the collapse of the star's iron core. The remnants of Tycho's and Kepler's supernovas are thought to have been produced by Type Ia supernovas. These supernovas, called Type Ib and Type Ic, apparently differ from Type II because they lost their outer hydrogen envelope prior to the explosion. The production of electron-positron pairs saps energy from the core of the star, disturbing the equilibrium between the outward push of pressure and the inward crush of gravity. Because of this, we can't even see the black hole itself; all we can see are its effects on nearby matter. When the core stops collapsing because of neutron degeneracy pressure, the outer layers crash into the core and "bounce" outwards, creating a shock wave. Chandra's image of the Crab Nebula reveals rings and jets of high-energy particles that appear to have been flung outward over great distances from the neutron star. A Type Ia supernova is produced by a sudden thermonuclear explosion that disintegrates a white dwarf star. The most famous Type II supernova, SN 1987A, was also a very unusual one. Type II supernovas occur in regions with lots of bright, young stars, such as the spiral arms of galaxies. The nebulae are filled with high-energy electrons that are flung out from a pulsar in the middle. The diameter of the inner ring is about 1,000 times the diameter of our solar system. When the jet is momentarily aimed towards Earth during its rotation, we see a regular, repeating pulse...which is why these stars are called pulsars. 2) Check with the Chandra catalog to make sure that you are in the right ballpark for your measured angular size. Chandra Images: Supernovas & Supernova Remnants A Chandra observation of the supernova remnant Cassiopeia A (Cas A) clearly shows both the outer shock wave and the debris heated by the reverse shock wave. Though there is no fusion, the star keeps itself together through degeneracy pressure.