![In less than a heartbeat, the rug gets pulled out from
underneath the star, and the whole shebang (a star tens
of times more massive than the sun) collapses in on itself
in a sped-up trainwreck of a supernova explosion,
releasing far more energy than it normally would, thus
resulting in a hypernova.
What causes a supernova?
History
In the 1980s, the term hypernova was used to describe a theoretical
type of supernova now known as a pair-instability supernova. It referred
to the extremely high energy of the explosion compared to typical core
collapse supernovae.[1][2][3] The term had previously been used to
describe hypothetical explosions from diverse events such
as hyperstars, extremely massive population III stars in the early
universe,[4] or from events such as black hole mergers.[5]](https://image.slidesharecdn.com/physicspresentation-230227154712-47611fde/85/Physics-Presentation-pptx-9-320.jpg)
Physics Presentation.pptx
- 3. What Is a Supernova?
- 4. One type of supernova is caused by the “last hurrah” of a dying massive star. This happens when a star at least five times the mass of our sun goes out with a fantastic bang! Massive stars burn huge amounts of nuclear fuel at their cores, or centers. This produces tons of energy, so the center gets very hot. Heat generates pressure, and the pressure created by a star’s nuclear burning also keeps that star from collapsing. A star is in balance between two opposite forces. The star’s gravity tries to squeeze the star into the smallest, tightest ball possible. But the nuclear fuel burning in the star’s core creates strong outward pressure. This outward push resists the inward squeeze of gravity. What causes a supernova?
- 5. When a massive star runs out of fuel, it cools off. This causes the pressure to drop. Gravity wins out, and the star suddenly collapses. Imagine something one million times the mass of Earth collapsing in 15 seconds! The collapse happens so quickly that it creates enormous shock waves that cause the outer part of the star to explode! Usually a very dense core is left behind, along with an expanding cloud of hot gas called a nebula. A supernova of a star more than about 10 times the size of our sun may leave behind the densest objects in the universe—black holes.
- 6. A second type of supernova can happen in systems where two stars orbit one another and at least one of those stars is an Earth- sized white dwarf. A white dwarf is what's left after a star the size of our sun has run out of fuel. If one white dwarf collides with another or pulls too much matter from its nearby star, the white dwarf can explode. Kaboom! The Crab Nebula Image credit: NASA, ESA, A white dwarf pulls Image credit: STSc
- 7. How bright are supernovas? These spectacular events can be so bright that they outshine their entire galaxies for a few days or even months. They can be seen across the universe. How common are supernovas? Not very. Astronomers believe that about two or three supernovas occur each century in galaxies like our own Milky Way. Because the universe contains so many galaxies, astronomers observe a few hundred supernovas per year outside our galaxy. Space dust blocks our view of most of the supernovas within the Milky Way. What can we learn from supernovas? Scientists have learned a lot about the universe by studying supernovas. They use the second type of supernova (the kind involving white dwarfs) like a ruler, to measure distances in space. How do scientists study supernovas? NASA scientists use a number of different types of telescopes to search for and then study supernovas. NASA’s NuSTAR spacecraft Image credit: NASA/JPL-Caltech
- 8. What Is a Hypernova? A hypernova (sometimes called a collapsar) is a very energetic supernova thought to result from an extreme core-collapse scenario. In this case, a massive star collapses to form a rotating black hole emitting twin energetic jets and surrounded by an accretion disk. It is a type of stellar explosion that ejects material with an unusually high kinetic energy, an order of magnitude higher than most supernovae, with a luminosity at least 10 times greater.
- 9. In less than a heartbeat, the rug gets pulled out from underneath the star, and the whole shebang (a star tens of times more massive than the sun) collapses in on itself in a sped-up trainwreck of a supernova explosion, releasing far more energy than it normally would, thus resulting in a hypernova. What causes a supernova? History In the 1980s, the term hypernova was used to describe a theoretical type of supernova now known as a pair-instability supernova. It referred to the extremely high energy of the explosion compared to typical core collapse supernovae.[1][2][3] The term had previously been used to describe hypothetical explosions from diverse events such as hyperstars, extremely massive population III stars in the early universe,[4] or from events such as black hole mergers.[5]
- 10. Properties Hypernovae are now widely accepted to be supernovae with ejecta having a kinetic energy larger than about 1045 joule, an order of magnitude higher than a typical core collapse supernova. The ejected nickel masses are large and the ejection velocity up to 99% of the speed of light. Astrophysical models Models for hypernova focus on the efficient transfer of energy into the ejecta. In normal core collapse supernovae, 99% of neutrinos generated in the collapsing core escape without driving the ejection of material. It is thought that rotation of the supernova progenitor drives a jet that accelerates material away from the explosion at close to the speed of light. Collapsar model The collapsar model describes a type of supernova that produces a gravitationally collapsed object, or black hole. The word "collapsar", short for "collapsed star", was formerly used to refer to the end product of stellar gravitational collapse, a stellar-mass black hole. The word is now sometimes used to refer to a specific model for the collapse of a fast-rotating star
- 11. Gamma-ray burst progenitors – Types of celestial objects that can emit gamma-ray bursts Quark star– Compact exotic star which forms matter consisting mostly of quarks Quark-nova – Hypothetical violent explosion resulting from conversion of a neutron star to a quark star