Nova

recurrent novaclassical novanovaehelium novanew starNovasStellar surface fusionclassic novaenormously bright starfar too small to explode
A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or many months.wikipedia
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Cataclysmic variable star

cataclysmic variablecataclysmic variablescataclysmic
They are all considered to be cataclysmic variable stars.
They were initially called novae, from the Latin 'new', since ones with an outburst brightness visible to the naked eye and an invisible quiescent brightness appeared as new stars in the sky.

Dwarf nova

SU UMa variableSS Cyg variableSU Ursae Majoris
The main sub-classes of novae are classical novae, recurrent novae (RNe), and dwarf novae.
novae) is a type of cataclysmic variable star consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion.

Binary star

spectroscopic binaryeclipsing binarybinary
All observed novae involve a white dwarf in a close binary system.
Binary stars are also common as the nuclei of many planetary nebulae, and are the progenitors of both novae and type Ia supernovae.

Transient astronomical event

transientastronomical eventastronomical transient
A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star, that slowly fades over several weeks or many months.
Singularly, the term is used for violent deep-sky events, such as supernovae, novae, dwarf nova outbursts, gamma-ray bursts, and tidal disruption events, as well as gravitational microlensing, transits and eclipses.

List of novae in the Milky Way galaxy

frequentlyList of novae
They occur far more frequently than galactic supernovae, averaging about ten per year.
This is a partial list of novae in the Milky Way galaxy that have been discovered and recorded since 1891.

Nova remnant

A few novae produce short-lived nova remnants, lasting for perhaps several centuries.
A nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae.

Supernova

supernovaecore-collapse supernovasupernovas
They occur far more frequently than galactic supernovae, averaging about ten per year. During the sixteenth century, astronomer Tycho Brahe observed the supernova SN 1572 in the constellation Cassiopeia.
Supernovae are more energetic than novae.

Tycho Brahe

BraheTychoTyge Brahe
During the sixteenth century, astronomer Tycho Brahe observed the supernova SN 1572 in the constellation Cassiopeia.
His precise measurements indicated that "new stars" (stellae novae, now known as supernovae), in particular that of 1572, lacked the parallax expected in sublunar phenomena and were therefore not tailless comets in the atmosphere as previously believed but were above the atmosphere and beyond the moon.

SN 1572

Tycho's Supernova1572Tycho's Nova
During the sixteenth century, astronomer Tycho Brahe observed the supernova SN 1572 in the constellation Cassiopeia.
The appearance of the "new star" helped to revise ancient models of the heavens and to speed on a revolution in astronomy that began with the realisation of the need to produce better astrometric star catalogues (and thus the need for more precise astronomical observing instruments).

Thermal runaway

runawayrunaway reactionthermal explosion
Hydrogen fusion may occur in a stable manner on the surface of the white dwarf for a narrow range of accretion rates, giving rise to a super soft X-ray source, but for most binary system parameters, the hydrogen burning is unstable thermally and rapidly converts a large amount of the hydrogen into other, heavier chemical elements in a runaway reaction, liberating an enormous amount of energy.
In astrophysics, runaway nuclear fusion reactions in stars can lead to nova and several types of supernova explosions, and also occur as a less dramatic event in the normal evolution of solar mass stars, the "helium flash".

RS Ophiuchi

RS Oph
An example is RS Ophiuchi, which is known to have flared six times (in 1898, 1933, 1958, 1967, 1985, and 2006).
RS Ophiuchi (RS Oph) is a recurrent nova system approximately 5,000 light-years away in the constellation Ophiuchus.

V1500 Cygni

Nova Cygni 1975V1500 CygNova Cygni
The brightest recent example was Nova Cygni 1975.
V1500 Cygni or Nova Cygni 1975 was a bright nova occurring in 1975 in the constellation Cygnus.

Super soft X-ray source

VY Scl starVY Sculptoris starNL/VY Scl variable
Hydrogen fusion may occur in a stable manner on the surface of the white dwarf for a narrow range of accretion rates, giving rise to a super soft X-ray source, but for most binary system parameters, the hydrogen burning is unstable thermally and rapidly converts a large amount of the hydrogen into other, heavier chemical elements in a runaway reaction, liberating an enormous amount of energy.
Those with luminosities below ~3 x 10 38 erg/s are consistent with steady nuclear burning in accreting white dwarfs (WD)s or post-novae.

Accretion (astrophysics)

accretionaccretingaccreted
When the orbital period falls in the range of several days to one day, the white dwarf is close enough to its companion star to start drawing accreted matter onto the surface of the white dwarf, which creates a dense but shallow atmosphere.
Occasionally, this can result in stellar surface fusion (see Bondi accretion).

White dwarf

white dwarfswhite dwarf starcentral star
All observed novae involve a white dwarf in a close binary system.
The spectra of these novae exhibit abundances of neon, magnesium, and other intermediate-mass elements which appear to be only explicable by the accretion of material onto an oxygen-neon-magnesium white dwarf.

V339 Delphini

Nova Delphini 2013V339 Del
The most recent were V1280 Scorpii, which reached magnitude 3.7 on 17 February 2007, and Nova Delphini 2013.
V339 Delphini or Nova Delphini 2013 (PNV J20233073+2046041) is a bright nova star in the constellation Delphinus.

V445 Puppis

The theory was first proposed in 1989, and the first candidate helium nova to be observed was V445 Puppis in 2000.
V445 Puppis was a nova in the constellation Puppis.

Nova Centauri 2013

V1369 Centauri
The last bright nova was V1369 Centauri reaching 3.3 magnitude on 14 December 2013.
Nova Cen 2013 or V1369 Cen (PNV J13544700-5909080) was a bright nova in the constellation Centaurus.

V1280 Scorpii

V1280 Sco
The most recent were V1280 Scorpii, which reached magnitude 3.7 on 17 February 2007, and Nova Delphini 2013.
V1280 Scorpii (or Nova Scorpii 2007) is a nova observed in February 2007 in the constellation Scorpius, just south of M62.

Andromeda Galaxy

AndromedaM31Andromeda Nebula
Roughly 25 novae brighter than about the twentieth magnitude are discovered in the Andromeda Galaxy each year and smaller numbers are seen in other nearby galaxies.
At the time Andromeda was considered to be a nearby object, so the cause was thought to be a much less luminous and unrelated event called a nova, and was named accordingly; "Nova 1885".

Symbiotic nova

symbiotic
Symbiotic novae are slow irregular eruptive variable stars with very slow nova-like outbursts with an amplitude of between 9 and 11 magnitudes.

Roche lobe

donor starRoche-lobemass transfer
The second star—which may be either a main sequence star or an aging giant—begins to shed its envelope onto its white dwarf companion when it overflows its Roche lobe.
Mass transfer due to Roche-lobe overflow is responsible for a number of astronomical phenomena, including Algol systems, recurring novae (binary stars consisting of a red giant and a white dwarf that are sufficiently close that material from the red giant dribbles down onto the white dwarf), X-ray binaries and millisecond pulsars.

Type Ia supernova

type IaType Ia supernovaetype 1a supernova
Eventually, the white dwarf could explode as a Type Ia supernova if it approaches the Chandrasekhar limit.
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.

Milky Way

Milky Way Galaxygalaxyour galaxy
Novae most often occur in the sky along the path of the Milky Way, especially near the observed galactic centre in Sagittarius; however, they can appear anywhere in the sky.
Searching the photographic record, he found 11 more novae.

Multimodal distribution

bimodalbimodal distributionmultimodal
For instance, the distribution of their absolute magnitude is bimodal, with a main peak at magnitude −8.8, and a lesser one at −7.5.
Examples of variables with bimodal distributions include the time between eruptions of certain geysers, the color of galaxies, the size of worker weaver ants, the age of incidence of Hodgkin's lymphoma, the speed of inactivation of the drug isoniazid in US adults, the absolute magnitude of novae, and the circadian activity patterns of those crepuscular animals that are active both in morning and evening twilight.