An Etymological Dictionary of Astronomy and Astrophysics
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The material ejected by a → supernova explosion.

→ supernova; → ejecta.

The total amount of energy liberated by a → supernova. A typical supernova radiates between 10⁵¹ and 10⁵²  → erg, or 10^44-45 J (→ joules).

→ supernova; → energy.

The very short and violent phenomenon that occurs when a star undergoes → core collapse or → thermonuclear runaway.

→ supernova; → explosion.

1) The process whereby the energy and matter contained in a → supernova are injected into the → interstellar medium after the → supernova explosion. The → thermal energy injected into the ISM serves to → suppress → star formation, while → heavy elements → nucleosynthesized inside SNe tend to enhance star formation.
2) The matter thus injected.

→ supernova; → feedback.

A brilliant burst of light that would suggest a → supernova explosion, but analysis of the star's → light curve, → spectrum, and → luminosity rules it out as a genuine supernova. Energetic → outbursts of → massive stars are often labeled as "supernova impostors" (Van Dyk et al. 2000). Many of these giant eruptions are spectroscopically similar to → Type II-n supernovae and thus receive a supernova (SN) designation, but are later recognized as subluminous or their spectra and light curves do not develop like true supernovae. Consequently, they are often referred to as "supernova impostors." These impostors or giant eruptions are examples of high → mass loss episodes apparently from evolved massive stars. Authors often refer to them as → Luminous Blue Variables (LBVs), but these giant eruptions are distinctly different from LBV/→ S Doradus variability in which the star does not increase in luminosity and the eruption or maximum light can last for several years. The mechanisms triggering these events are not yet fully understood (see, e.g., Humphreys et al., 2016, arXiv:1606.04959v1).

→ supernova; → impostor.

The graph of luminosity as a function of time after a → supernova explosion. The → light curve goes up rapidly to a → peak luminosity, then decays away slowly over time, with different rates, depending on the → supernova type. The temporal evolution of a supernova's luminosity contains important information on the physical processes driving the explosion. The observed → bolometric light curves provide a measure of the total output of converted radiation of → Type Ia supernovae, and hence serve as a crucial link to theoretical models of the explosion and evolution.

→ supernova; → light; → curve.

A star which is at the origin of a supernova phenomenon.

→ supernova; → progenitor.

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.

→ supernova; → remnant.

A → shock wave that forms when the inner → iron core (of ~ 0.5 Msun) → collapses until it reaches densities in excess of → nuclear density. At this point the pressure rises dramatically and resists further collapse. The homologous core bounces and drives out a shock wave that works its way through the remainder of the initial iron core. The small compressibility of nuclear matter halts the infall of the innermost core by an elastic collective bounce whose kinetic energy is almost immediately depleted by the → photodisintegration of heavy nuclei and the emission of → neutrinos.

→ supernova; → shock.

The classification of supernovae according to the presence or absence of the absorption lines of different chemical elements that appear in their spectra shortly after their explosion. Basically, supernovae come in two main types: those that have hydrogen (Type II, from a very massive star that blows up) and those that do not (Type I, due to thermonuclear runaways in a less massive star). Both types exhibit a wide variety of subclasses. Type Ia lacks hydrogen and presents a singly-ionized silicon (Si II) line at 6150 Å, near peak light. Type Ib has non-ionized helium (He I) line at 5876 Å, and no strong silicon absorption feature near 6150 Å. Type Ic shows weak or no helium lines and no strong silicon absorption feature near 6150 Å. Type II stars also have various subclasses. See also → Type I supernova, → Type Ia supernova, → Type Ib supernova, → Type Ic supernova, → Type II supernova, → Type II-L supernova, → Type II-n supernova, and → Type II-P supernova

→ supernova; → type.

Same as → type Ia supernova

→ thermonuclear; → supernova.

A type of supernova whose spectra lacks hydrogen lines. Its → light curve exhibits a sharp maximum with a gradual decrease. Typical magnitudes M_V = -14 to -17. Ejecta velocities about 10,000 km/sec. Type I supernovae have several subtypes: → Type Ia, → Type Ib, and → Type Ic.

Type I initially introduced by R. Minkowski (1941, PASP 53, 224); → type; → supernova.

A → Type I supernova that presents a singly-ionized silicon (Si II) absorption feature at 6150 Å near peak brightness. Type Ia SNe are believed to result from mass → accretion to a carbon-oxygen → white dwarf in a → close binary system. When the white dwarf mass exceeds the → Chandrasekhar limit, the → degenerate electron pressure can no longer support the accumulated mass and the star collapses in a thermonuclear explosion producing a supernova. The → peak luminosity of SNe Ia is set by the radioactive decay chain ⁵⁶Ni → ⁵⁶Co → ⁵⁶Fe, and the observed photometric correlation between the peak luminosity and the time-scale over which the → light curve decays from its maximum is understood physically as having both the luminosity and → opacity being set by the mass of ⁵⁶Ni synthesized in the explosion. Type Ia supernovae occur in all types of galaxies. Type Ia SNe are used as → standard candles in determining cosmological distances, after normalizing their light curves with the → Phillips relation.

→ type; → supernova.

A → Type I supernova that has neutral helium line (He I) at 5876 Å, and no strong silicon (Si II) absorption feature at 6150 Å. Type Ib supernovae are believed to result from the evolution of → massive stars.

→ type; → supernova.

A → Type I supernova that shows weak or no helium lines and no strong silicon (Si II) absorption feature near 6150 Å. Type Ic supernovae are believed to result from the evolution of → massive stars.

→ type; → supernova.

A supernova type whose spectrum contains hydrogen lines. Compared with → Type I supernovae, its → light curve has a broader peak at maximum and dies away more rapidly. The magnitudes are smaller, ranging from M_V = -12 to -13.5, and the ejecta have lower velocities (about 5,000 km/sec). These supernovae, which result from the final evolution of → massive stars, have three main divisions: → Type II-P, → Type II-L, and → Type II-n.

Type II initially introduced by R. Minkowski (1941, PASP 53, 224); → type; → supernova.

A → Type II supernova which displays a linear decrease in its → light curve.

→ Type II supernova; L short for → linear.

A → Type II supernova which shows intermediate or very narrow width hydrogen → emission lines in the spectra.

→ Type II supernova; n short for → narrow.

A → Type II supernova which reaches a plateau in its → light curve. The vast majority of Type II SNe are characterized by a fast (few days) rise to a flat light curve, most pronounced in the reddest optical bands, with a duration of 80-100 days. This plateau phase is interpreted as the recession of the photosphere as the ejecta expand and cool. The spectra of SNe II-P are typically dominated by strong → P Cygni profiles of hydrogen lines, as well as iron absorption features (for a review, e.g., see Filippenko 1997, ARA&A 35, 309).

→ Type II supernova; P short for → plateau.

A → supernova remnant located in the southern Milky Way in the constellation → Vela. It has a large angular diameter of about 8° and lies 250 ± 30 pc away (Cha et al. 1999, ApJ 515, L25). Its overall emission is dominated by the interaction of the → supernova blast wave with the → interstellar medium. This SNR is also notable for a number of protrusions extending well beyond its rim, which were suggested to be fragments of ejecta from the supernova explosion. X-ray spectroscopy has since confirmed several of these protrusions to indeed be strongly enriched with ejecta. The age of the SNR is estimated to be ~11,000 years, based on the spin-down rate of the associated → Vela pulsar, but ages as large as 20,000-30,000 years have also been argued.

→ Vela; → supernova remnant.