Hypernova also known as a type 1c Supernova
Type Ib and Ic supernovae
Types Ib and Ic supernovae are categories of stellar explosions that are caused by the core collapse of massive stars. These stars have shed their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon...

, refers to an incredibly large star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

 that collapses at the end of its lifespan. Until the 1990s, it referred specifically to an explosion with an energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 of over 100 supernovae (over 1048 joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

s); such explosions are believed to be the origin of long-duration gamma-ray bursts.

After the 1990s, the term came to be used to describe the supernovae of the most massive stars, the hypergiant
A hypergiant is a star with a tremendous mass and luminosity, showing signs of a very high rate of mass loss.-Characteristics:...

s, which have masses from 100 to over 300 times that of the Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. Decaying 56Ni
Isotopes of nickel
Naturally occurring nickel is composed of five stable isotopes; , , , and with being the most abundant . 58Ni may decay by double beta-plus decay to 58Fe. 26 radioisotopes have been characterised with the most stable being with a half-life of 76,000 years, with a half-life of 100.1 years,...

, a short-lived isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 of nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...

, is believed to provide much of a hypernova's light.

The radiation output of a nearby hypernova could cause serious harm to Earth; however, no hypergiant is located close enough to Earth to pose a threat. A group led by Brian Thomas, an astrophysicist at Washburn University
Washburn University
Washburn University is a co-educational, public institution of higher learning in Topeka, Kansas, USA. It offers undergraduate and graduate programs, as well as professional programs in law and business. Washburn has 550 faculty members, who teach more than 6,400 undergraduate students and...

 in Kansas, has conjectured that a hypernova may have caused the Ordovician–Silurian mass extinction on Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 440 million years ago, but there is no unambiguous evidence of it.

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
Stellar black hole
A stellar black hole is a black hole formed by the gravitational collapse of a massive star. They have masses ranging from about 3 to several tens of solar masses...

. The word is sometimes used now to refer to a specific model for the collapse of a fast-rotating star, as discussed below.

Collapsing star

The core of a hypernova collapses directly into a black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...

, and two extremely energetic jets of plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...

 are emitted from its rotational poles at nearly the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

. These jets emit intense gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s and are a candidate explanation for long-duration gamma-ray bursts. However, hypernovas are not a candidate to explain short duration gamma-ray bursts, which are apparently not associated with massive stars, since some short bursts appear in regions where there is no new star formation – a necessity since massive stars have short lifetimes and thus must be newly-born.

The energy output of a hypernova from a massive star, plus a beaming effect, is needed to explain the observed brightness plus the great distance (up to 10 billion light years, as measured by red shift of afterglow ionization) of long-duration (> 2 seconds) gamma-ray bursts, which requires on the order of 1044 joules of gamma radiation emission. The mechanism is that since powerful energy jets would be created along the rotation axis of the black hole, a burst of high-energy radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 would appear to an observer in the path of the jet, even at a distance which is a large fraction of that to the visible edge of the universe. To date, hypernovas and long-duration gamma-ray bursts have been seen in stellar nurseries, but none has yet been observed in our own galaxy.

Since stars large enough to collapse directly into a black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...

 are quite rare, hypernovae would likewise be rare, if they indeed occur. It has been estimated that a hypernova would occur in our galaxy every 200 million years.

In recent years a great deal of observational data on long-duration gamma-ray bursts significantly increased our understanding of these events and made clear that the collapse model
Computational model
A computational model is a mathematical model in computational science that requires extensive computational resources to study the behavior of a complex system by computer simulation. The system under study is often a complex nonlinear system for which simple, intuitive analytical solutions are...

 produces explosions that differ only in detail from more or less ordinary supernovae. Nevertheless, they continue sometimes to be referred to in the literature as hypernovae. The word hypernova itself was coined by S.E. Woosley
Stanford E. Woosley
Stanford Earl Woosley is a physicist, and Professor of Astronomy and Astrophysics. He is the director of the Center for Supernova Research at UCSC. He has published over 300 papers.-Research Interest:...


Collapsar is currently used as the name of a hypothetical model where a fast-rotating Wolf-Rayet star
Wolf-Rayet star
Wolf–Rayet stars are evolved, massive stars , which are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s...

 with a massive (greater than 30 solar mass
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...

es) core collapses to form a large, rotating black hole, drawing in the surrounding envelope of stellar matter
Matter is a general term for the substance of which all physical objects consist. Typically, matter includes atoms and other particles which have mass. A common way of defining matter is as anything that has mass and occupies volume...

 at relativistic
Special relativity
Special relativity is the physical theory of measurement in an inertial frame of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies".It generalizes Galileo's...

 speeds with a Lorentz factor
Lorentz factor
The Lorentz factor or Lorentz term appears in several equations in special relativity, including time dilation, length contraction, and the relativistic mass formula. Because of its ubiquity, physicists generally represent it with the shorthand symbol γ . It gets its name from its earlier...

 of around 150. These speeds would make collapsars the fastest known celestial objects. They may be considered to be "failed" type Ib supernovae.

A possible example of a collapsar is the unusual supernova Sn1998bw, which was associated with the gamma-ray burst GRB 980425
GRB 980425
GRB 980425 was a gamma-ray burst that was detected on 25 April 1998 at 21:49 UTC. A gamma-ray burst is a highly luminous flash associated with an explosion in a distant galaxy and producing gamma rays, the most energetic form of electromagnetic radiation, and often followed by a longer-lived...

. This was classified as a type Ic supernova due to its distinctive spectral
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

 properties in the radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

 spectrum, indicating the presence of relativistic matter.

Another type of hypernova is a pair-instability supernova
Pair-instability supernova
A pair-instability supernova occurs when pair production, the production of free electrons and positrons in the collision between atomic nuclei and energetic gamma rays, reduces thermal pressure inside a supermassive star's core...

, of which SN 2006gy
SN 2006gy
SN 2006gy was an extremely energetic supernova, sometimes referred to as a hypernova or quark-nova, that was discovered on September 18, 2006. It was first observed by Robert Quimby and P. Mondol, and then studied by several teams of astronomers using facilities that included the Chandra, Lick, and...

 was possibly the first observed example. This supernova event was observed in a galaxy about 240 million light years (72 million parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....

s) from Earth. In a pair-instability supernova, the pair production
Pair production
Pair production refers to the creation of an elementary particle and its antiparticle, usually from a photon . For example an electron and its antiparticle, the positron, may be created...

 effect causes a sudden pressure drop in the star's core, leading to a rapid partial collapse, which causes a sharp rise in temperature and pressure leading to an explosive thermonuclear burning and complete explosion of the star.

In fiction

Jack McDevitt
Jack McDevitt
Jack McDevitt is an American science fiction author whose novels frequently deal with attempts to make contact with alien races, and with archaeology or xenoarchaeology....

's science fiction novel The Devil's Eye features a hypernova outside the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...


The science fiction novel The Forever War
The Forever War
The Forever War is a science fiction novel by American author Joe Haldeman, telling the contemplative story of soldiers fighting an interstellar war between humanity and the enigmatic Tauran species...

describes collapsars as a way to travel faster than light in its universe. They are, however, much smaller in scale and in much greater abundance in the book than they are in reality.

Further reading

  • A. I. MacFadyen and S. E. Woosley "Collapsars: Gamma-Ray Bursts and Explosions in 'Failed Supernovae'" Astrophysical Journal
    Astrophysical Journal
    The Astrophysical Journal is a peer-reviewed scientific journal covering astronomy and astrophysics. It was founded in 1895 by the American astronomers George Ellery Hale and James Edward Keeler. It publishes three 500-page issues per month....

    , Vol 524, Pages 262–289, October 1999.
  • Stanford E. Woosley "Gamma-ray bursts from stellar mass accretion disks around black holes" Astrophysical Journal, Vol 405, Pages 273–277, March 1993.
  • Tsvi Piran "The Physics of Gamma-Ray Bursts" Reviews of Modern Physics
    Reviews of Modern Physics
    The Reviews of Modern Physics is a journal of the American Physical Society. The journal started in paper form. All volumes are also online by subscription.Issue 1, Volume 1 consisted of the review by...

    , Vol 76, October 2004
  • Cosmological Gamma-Ray Bursts and Hypernovae Conclusively Linked (SN 2003dh and GRB 030329) European Southern Observatory
    European Southern Observatory
    The European Southern Observatory is an intergovernmental research organisation for astronomy, supported by fifteen countries...

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