Supernovae Quiz

Supernova: Explosion of a Star at Its End of Life

• A supernova is a powerful and luminous explosion of a star that occurs during the last evolutionary stages of a massive star or when a white dwarf is triggered into runaway nuclear fusion.

• The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months.

• Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a white dwarf, or the sudden gravitational collapse of a massive star's core.

• Supernovae can expel several solar masses of material at velocities up to several percent of the speed of light, driving an expanding shock wave into the surrounding interstellar medium, observed as a supernova remnant.

• The most recent naked-eye supernova was SN 1987A, which was the explosion of a blue supergiant star in the Large Magellanic Cloud, a satellite of the Milky Way.

• Supernovae are a major source of elements in the interstellar medium from oxygen to rubidium and can trigger the formation of new stars.

• The word supernova is derived from the Latin word nova, meaning "new", and was coined by Walter Baade and Fritz Zwicky in 1931.

• Supernovae are relatively rare events, occurring about three times a century in the Milky Way, and only a tiny fraction of stars have the capacity to become a supernova.

• Supernovae in other galaxies cannot be predicted with any meaningful accuracy and are discovered when they are already in progress.

• Supernova discoveries are reported to the International Astronomical Union's Central Bureau for Astronomical Telegrams, which assigns a name to the supernova.

• Astronomers classify supernovae according to their light curves and the absorption lines of different chemical elements that appear in their spectra.

• Type I and Type II supernovae are classified on the basis of their spectra, with Type Ia showing a strong ionised silicon absorption line and Type II showing lines of hydrogen known as the Balmer series in the visual portion of the spectrum.

• Calcium-rich supernovae are a rare type of very fast supernova with unusually strong calcium lines in their spectra, thought to occur when material is accreted from a helium-rich companion rather than a hydrogen-rich star.Classification and Formation of Supernovae

• Type II supernovae can be sub-divided based on their spectra, with some having relatively narrow features and are called type IIn.

• Type IIb supernovae show lines of hydrogen at early times, but become dominated by lines of helium over time.

• Type II-P supernovae show a distinctive "plateau" in the light curve shortly after peak brightness where the visual luminosity stays relatively constant for several months.

• Type II-L supernovae lack a distinct plateau and have a linear light curve.

• Supernovae that do not fit into the normal classifications are designated peculiar, or "pec".

• Type Ia supernovae are produced by runaway fusion ignited on degenerate white dwarf progenitors.

• Normal Type Ia supernovae have very uniform properties and are useful standard candles over intergalactic distances.

• Abnormally bright type Ia supernovae occur when the white dwarf already has a mass higher than the Chandrasekhar limit.

• Type Iax supernovae occur when helium accretes onto a white dwarf and may not completely destroy the white dwarf progenitor.

• Type Ia/IIn supernovae originate from exploding white dwarfs but contain hydrogen lines in their spectra.

• Core collapse can be caused by several different mechanisms and is the cause of all types of supernova except type Ia.

• The sudden halt of core collapse rebounds and produces a shock wave that stalls in the outer core within milliseconds as energy is lost through the dissociation of heavy elements.Supernovae: Types, Light Curves, and Energy Output

• Core collapse supernovae occur when massive stars exhaust their nuclear fuel and their cores collapse, resulting in a powerful explosion.

• Type II supernovae occur when core collapse occurs during a supergiant phase when the star still has a hydrogen envelope.

• Type Ib and Ic supernovae occur when stars that become supernovae have lost most of their outer hydrogen envelopes due to strong winds or interaction with a companion.

• Ultra-stripped supernovae occur when the exploding star has been stripped almost all the way to the metal core via mass transfer in a close binary.

• SN 2019hgp was the first supernova explosion showing direct evidence for a Wolf-Rayet progenitor star.

• Electron-capture supernovae arise when a star in the transitional range between white dwarf formation and iron core-collapse supernovae implodes after its core runs out of nuclear fuel.

• Failed supernovae occur when the initial core collapse cannot be reversed by the mechanism that produces an explosion, usually because the core is too massive.

• The light curves of supernovae are dominated by subsequent radioactive heating of the rapidly expanding ejecta.

• The luminous emission of type Ia supernovae is driven by radioactive decay of ejected nickel-56.

• Type II supernovae show a prolonged plateau in their light curves due to the existence of hydrogen in the ejecta from the atmosphere of the supergiant progenitor star.

• The remaining compact object receives a large velocity away from the epicenter due to an expansion asymmetry, but the mechanism by which momentum is transferred to the compact object remains a puzzle.

• The electromagnetic radiation emitted by supernovae is almost a minor side-effect, as the emitted energy is a tiny fraction of the total energy released during the event.Supernovae: Classification, Progenitor, Role in Stellar Evolution, Effect on Earth

• Supernovae are classified into different types based on the type of star at the time of collapse, and the energy production varies in each type.

• Type Ia supernovae derive their energy from a runaway nuclear fusion of a carbon-oxygen white dwarf, resulting in ejection of the entire mass of the original star at high kinetic energy, and around half a solar mass of that mass is 56Ni generated from silicon burning.

• Core collapse supernovae are visually fainter, but the total energy released is far higher, and in some cases, fallback onto a black hole drives relativistic jets, transferring substantial further energy into the ejected material.

• Supernova classification depends on the progenitor star's metallicity, and type Ia supernovae occur in all galaxy types, while core collapse supernovae occur in galaxies undergoing current or very recent star formation.

• Type Ib and Ic supernovae are hypothesized to have been produced by core collapse of massive stars that have lost their outer layer of hydrogen and helium, and type IIn supernovae also have high rates of mass loss in the period just prior to their explosions.

• The progenitor of the supernova is closely tied to the type of star at the time of the collapse, and the occurrence of each type of supernova depends on the progenitor star's metallicity, affecting the strength of the stellar wind and thereby the rate at which the star loses mass.

• Supernovae events generate heavier elements that are scattered throughout the surrounding interstellar medium, enriching the molecular clouds that are the sites of star formation and ultimately influencing the star's life and possibility of having planets orbiting it.

• Supernova remnants consist of a compact object and a rapidly expanding shock wave of material, enriching the surrounding interstellar medium with elements other than hydrogen and helium, which astronomers refer to as "metals," and triggering star formation by compressing nearby, dense molecular clouds in space.

• Supernovae are a major source of elements in the interstellar medium from oxygen through to rubidium, with type Ia supernovae producing mainly silicon and iron-peak elements, and core collapse supernovae ejecting much smaller quantities of the iron-peak elements than type Ia supernovae but larger masses of light alpha elements such as oxygen and neon.

• Supernovae are potentially strong galactic sources of gravitational waves, but none have so far been detected, and using the arrival of a neutrino signal may provide a trigger that can identify the time window in which to seek the gravitational wave, helping to distinguish the latter from background noise.

• Nearby supernovae may have influenced the biodiversity of life on Earth, with geological records suggesting that nearby supernova events have led to an increase in cosmic rays, which in turn produced a cooler climate, stronger winds, increased ocean mixing, and resulted in the transport of nutrients to shallow waters along the continental shelves, leading to greater biodiversity.

• Type Ia supernovae are potentially the most dangerous if they occur close enough to the Earth as they arise from dim, common white dwarf stars in binary systems.

• In 1996, it was theorized that traces of past supernovae might be detectable on Earth in the form of metal isotope signatures in rock strata, and in 2009, elevated levels of nitrate ions