Type Ia supernova

type IaType Ia supernovaetype 1a supernovaIaIa supernovaType 1aType 1a supernovaeType-Iadouble degeneratesupernova
A type Ia supernova (read "type one-a") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf.wikipedia
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White dwarf

white dwarfswhite dwarf starcentral star
A type Ia supernova (read "type one-a") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf. Theoretical astronomers long believed the progenitor star for this type of supernova is a white dwarf, and empirical evidence for this was found in 2014 when a Type Ia supernova was observed in the galaxy Messier 82.
A carbon–oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may explode as a type Ia supernova via a process known as carbon detonation; SN 1006 is thought to be a famous example.

Messier 82

M82Cigar GalaxyNGC 3034
Theoretical astronomers long believed the progenitor star for this type of supernova is a white dwarf, and empirical evidence for this was found in 2014 when a Type Ia supernova was observed in the galaxy Messier 82.
SN 2014J, a type Ia supernova, was discovered in the galaxy on 21 January 2014.

Dark energy

energyvacuum energycauses an acceleration in the expansion
Details of the pre-nova moments may help scientists better judge the quality of Type Ia supernovae as standard candles, which is an important link in the argument for dark energy.
In 1998, the High-Z Supernova Search Team published observations of Type Ia ("one-A") supernovae.

Star

starsstellarmassive star
A type Ia supernova (read "type one-a") is a type of supernova that occurs in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf.
When the Roche lobe is violated, a variety of phenomena can result, including contact binaries, common-envelope binaries, cataclysmic variables, and type Ia supernovae.

Binary star

spectroscopic binaryeclipsing binarybinary
One model for the formation of this category of supernova is a close binary star system.
Binary stars are also common as the nuclei of many planetary nebulae, and are the progenitors of both novae and type Ia supernovae.

Kepler space telescope

KeplerKepler MissionKepler Space Observatory
In May 2015, NASA reported that the Kepler space observatory observed KSN 2011b, a type Ia supernova in the process of exploding.

Chandrasekhar limit

Chandrasekhar masslimit(Chandrasekhar) limit
Somewhat confusingly, this limit is often referred to as the Chandrasekhar mass, despite being marginally different from the absolute Chandrasekhar limit where electron degeneracy pressure is unable to prevent catastrophic collapse.
Type Ia supernovae derive their energy from runaway fusion of the nuclei in the interior of a white dwarf.

SN 2003fg

Champagne SupernovaSNLS-03D3bb
A double degenerate scenario is one of several explanations proposed for the anomalously massive progenitor of SN 2003fg.
SN 2003fg, sometimes called the "Champagne Supernova", was an unusual Type Ia supernova.

SN 2011fe

In the case of SN 2011fe, the companion star must have been smaller than the Sun, if it existed.
SN 2011fe, initially designated PTF 11kly, was a Type Ia supernova discovered by the Palomar Transient Factory (PTF) survey on 24 August 2011 during an automated review of images of the Messier 101 from the nights of 22 and 23 August 2011.

Thermal runaway

runawayrunaway reactionthermal explosion
Within a few seconds of initiation of nuclear fusion, a substantial fraction of the matter in the white dwarf undergoes a runaway reaction, releasing enough energy (1–2e44 J) to unbind the star in a supernova explosion.
A type Ia supernova results from runaway carbon fusion in the core of a carbon-oxygen white dwarf star.

Type II supernova

Type IItype II-P supernovatype IIn supernova
Type Ia supernova differ from Type II supernova, which are caused by the cataclysmic explosion of the outer layers of a massive star as its core collapses, powered by release of gravitational potential energy via neutrino emission.
White dwarf stars, if they have a near companion, may then become Type Ia supernovae.

Nova

recurrent novaclassical novanovae
The theory of this type of supernova is similar to that of novae, in which a white dwarf accretes matter more slowly and does not approach the Chandrasekhar limit.
Eventually, the white dwarf could explode as a Type Ia supernova if it approaches the Chandrasekhar limit.

SN 1006

supernova of 1006supernova that occurred in 1006 CEthe 1006 supernova
It has also been strongly suggested for SN 1006, given that no companion star remnant has been found there.
This description is often taken as probable evidence that the supernova was of Type Ia.

Zombie star

supernova 2012Z
This type of supernova may not always completely destroy the white dwarf progenitor, but instead leave behind a zombie star.
A zombie star is a hypothetical result of a Type Iax supernova which leaves behind a remnant star, rather than completely dispersing the stellar mass.

SNR 0509-67.5

It is the only possible explanation for SNR 0509-67.5, as all possible models with only one white dwarf have been ruled out.
It was probably a type Ia supernova, as indicated by the detection in 2004 of the elements silicon and iron.

Sloan Digital Sky Survey

SDSSBaryon Oscillation Spectroscopic SurveyApache Point Observatory Galactic Evolution Experiment
However, a study based on SDSS spectra found 15 double systems of the 4,000 white dwarfs tested, implying a double white dwarf merger every 100 years in the Milky Way.
In 2005 the survey entered a new phase, the SDSS-II, by extending the observations to explore the structure and stellar makeup of the Milky Way, the SEGUE and the Sloan Supernova Survey, which watches after supernova Ia events to measure the distances to far objects.

Accelerating expansion of the universe

accelerating universecosmic accelerationaccelerating
In 1998, observations of distant Type Ia supernovae indicated the unexpected result that the universe seems to undergo an accelerating expansion.
The accelerated expansion was discovered during 1998, by two independent projects, the Supernova Cosmology Project and the High-Z Supernova Search Team, which both used distant type Ia supernovae to measure the acceleration.

Gravitational wave

gravitational wavesgravitational radiationgravitational wave radiation
Inward spiraling white dwarf pairs are strongly-inferred candidate sources of gravitational waves, although they have not been directly observed.
They cannot get much closer together than 10,000 km before they will merge and explode in a supernova which would also end the emission of gravitational waves.

Calcium

CaCa 2+ calcium ions
Near the time of maximal luminosity, the spectrum contains lines of intermediate-mass elements from oxygen to calcium; these are the main constituents of the outer layers of the star.
48 Ca is produced by electron capture in the r-process in type Ia supernovae, where high neutron excess and low enough entropy ensures its survival.

Phillips relationship

The original correction to standard candle value is known as the Phillips relationship
In astrophysics, the Phillips relationship is the relationship between the peak luminosity of a Type Ia supernova and the speed of luminosity evolution after maximum light.

Carbon detonation

runaway carbon fusionigniteignition of carbon fusion
It involves a runaway thermonuclear process which spreads through the white dwarf in a matter of seconds, producing a Type Ia supernova which releases an immense amount of energy as the star is blown apart.

Universe

physical worldThe Universeuniverses
In 1998, observations of distant Type Ia supernovae indicated the unexpected result that the universe seems to undergo an accelerating expansion.
Commonly, the set of observations fitted includes the cosmic microwave background anisotropy, the brightness/redshift relation for Type Ia supernovae, and large-scale galaxy clustering including the baryon acoustic oscillation feature.

Calán/Tololo Survey

Calán/Tololo Supernova Survey
The use of Type Ia supernovae to measure precise distances was pioneered by a collaboration of Chilean and US astronomers, the Calán/Tololo Supernova Survey.
It was founded by Mario Hamuy, Jose Maza, Mark M. Phillips, and Nicholas B. Suntzeff in 1989 out of discussions at the UC Santa Cruz meeting on supernovae on how to improve the Hubble diagram using Type Ia supernovae.

Cosmic distance ladder

standard candlestandard candlesdistance
The stability of this value allows these explosions to be used as standard candles to measure the distance to their host galaxies because the visual magnitude of the supernovae depends primarily on the distance.
For example, all observations seem to indicate that Type Ia supernovae that are of known distance have the same brightness (corrected by the shape of the light curve).

Hubble's law

Hubble constantHubble parameterHubble flow
when combined with the Hubble diagram of the Type Ia supernova distances have led to an improved value of the Hubble constant.
A value for q measured from standard candle observations of Type Ia supernovae, which was determined in 1998 to be negative, surprised many astronomers with the implication that the expansion of the universe is currently "accelerating" (although the Hubble factor is still decreasing with time, as mentioned above in the Interpretation section; see the articles on dark energy and the ΛCDM model).