Artist's conception of a white dwarf star accreting hydrogen from a larger companion

A nova (pl. novae) is a cataclysmic nuclear explosion caused by the accretion of hydrogen onto the surface of a white dwarf star. Image File history File linksMetadata Making_a_Nova. ... Accretion, means any growth or increase in size by a gradual external addition or inclusion. ... Image of Sirius A and Sirius B taken by the Hubble Space Telescope. ... This article is about the astronomical object. ...

Development

If a white dwarf has a close companion star that overflows its Roche lobe, the white dwarf will steadily accrete gas from the star's outer atmosphere. The companion may be a main sequence star, or one that is aging and expanding into a red giant. The captured gases consist primarily of hydrogen and helium, the two principal constituents of ordinary matter in the universe. The gases are compacted on the white dwarf's surface by its intense gravity, compressed and heated to very high temperatures as additional material is drawn in. The white dwarf consists of degenerate matter, and so is largely unresponsive to heat, while the accreted hydrogen is not. Hydrogen fusion can occur in a stable manner on the surface through the CNO cycle; the dependence of the hydrogen fusion rate on temperature and pressure mean that it is only when it is compressed and heated at the surface of the white dwarf to a temperature of some 20 million K that a nuclear fusion reaction rapidly converts a large amount of the hydrogen into other heavier elements.^[1] The enormous amount of energy liberated by this process blows the remaining gases away from the white dwarf's surface and produces an extremely bright outburst of light. The rise to peak brightness can be very rapid or gradual which is related to the speed class of the nova ; after the peak the brightness declines steadily.^[2] The time taken for a nova to decay by 2 or 3 magnitudes from maximum optical brightness is used to classify a nova via its speed class. A fast nova will typically take less than 25 days to decay by 2 magnitudes and a slow nova will take over 80 days.^[3] A three-dimensional representation of the Roche potential in a binary star with a mass ratio of 2, in the co-rotating frame. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Cross section of a red giant showing nucleosynthesis and elements formed According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... In particle physics, the baryons are a family of subatomic particles including the proton and the neutron (collectively called Greek barys, meaning heavy, as they are heavier than the other main groups of particles. ... The deepest visible-light image of the cosmos, the Hubble Ultra Deep Field. ... Degenerate matter is matter which has sufficiently high density that the dominant contribution to its pressure arises from the Pauli exclusion principle. ... This article does not cite its references or sources. ... The Kelvin scale is a thermodynamic (absolute) temperature scale where absolute zero—the lowest possible temperature where nothing could be colder and no heat energy remains in a substance—is defined as zero kelvin (0 K). ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... The periodic table of the chemical elements A chemical element, often called simply an element, is a substance that cannot be decomposed or transformed into other chemical substances by ordinary chemical processes. ...

In spite of their violence, the amount of material ejected in novae is usually only about 1/10,000th of a solar mass, quite small relative to the mass of the white dwarf. Furthermore, only five percent of the accreted mass is fused to power the outburst.^[1] Nonetheless, this is enough energy to accelerate nova ejecta to velocities as high as several thousand kilometers per second--higher for fast novae than slow ones--with a concurrent rise in luminosity from a few times solar to 50,000-100,000 times solar.^{[1] [4]} In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... A kilometre (American spelling: kilometer) (symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... Luminosity has different meanings in several different fields of science. ...

A white dwarf can potentially generate multiple novae over time as additional hydrogen continues to accrete onto its surface from its companion star. An example is RS Ophiuchi, which is known to have flared six times (in 1898, 1933, 1958, 1967, 1985, and again in 2006). Eventually, however, either the white dwarf will run out of material, or collapse into a neutron star, or explode as a type Ia supernova. RS Ophiuchi (RS Oph) is a nova approximately 1,950 light-years away in the constellation Ophiuchus. ... 1898 (MDCCCXCVIII) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar (or a common year starting on Monday of the 12-day-slower Julian calendar). ... Year 1933 (MCMXXXIII) was a common year starting on Sunday. ... Year 1958 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ... 1967 (MCMLXVII) was a common year starting on Sunday of the Gregorian calendar (the link is to a full 1967 calendar). ... 1985 (MCMLXXXV) was a common year starting on Tuesday of the Gregorian calendar. ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... A neutron star is one of the few possible endpoints of stellar evolution. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ...

Occasionally a nova is bright enough and close enough to be conspicuous to the unaided eye. The most recent example was Nova Cygni 1975. This nova appeared on August 29, 1975 in the constellation Cygnus about five degrees north of Deneb and reached magnitude 2.0 (nearly as bright as Deneb). Another recent instance was Nova Cygni 1992, though it was considerably fainter. V1500 Cygni or Nova Cygni 1975 was a bright nova occuring in 1975 in the constellation Cygnus. ... August 29 is the 241st day of the year in the Gregorian Calendar (242nd in leap years), with 124 days remaining. ... 1975 (MCMLXXV) was a common year starting on Wednesday. ... Cygnus (Latin for swan) is a northern constellation. ... Deneb (α Cyg / α Cygni / Alpha Cygni) is the brightest star in the constellation Cygnus and one of the brightest stars in the night sky, with apparent magnitude 1. ... // Headline text HEY!! HOW ARE YOU ALL?? Its nice of you to come read this page. ... V1974 Cygni or Nova Cygni 1992 was a relatively bright nova in the constellation Cygnus. ...

Occurrence rate, and astrophysical significance

Astronomers estimate that the Milky Way experiences roughly 20 to 60 novae per year, with a likely rate of about 40.^[1] The number of novae discovered each year is much lower, probably due to great distance and observational biases.^[5] By comparison, the number of novae discovered each year in the nearby Andromeda Galaxy is much lower; roughly ½ to ⅓ that of the Milky Way.^[6] The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias), sometimes referred to simply as the Galaxy), is a barred spiral galaxy of the Local Group. ... Selection bias is the error of distorting a statistical analysis by pre- or post-selecting the samples. ... M31 in a small telescope The Andromeda Galaxy (IPA: , also known as Messier 31, M31, or NGC 224; older texts often called it the Andromeda Nebula) is a spiral galaxy approximately 2. ...

Spectroscopic observation of nova ejecta nebulae has shown that they are enriched in elements such as helium, carbon, nitrogen, oxygen, neon, and magnesium.^[1] Though it would seem that the contributions of novae to the Galaxy might be large over astronomical time scales, this is not the case; in fact, novae supply only 1/50th the amount of material to the interstellar medium as supernovae do, and only 1/200th that of red giant and supergiant stars.^[1] Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of matter and its properties by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation. ... The Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... For other uses, see Neon (disambiguation). ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... The interstellar medium (or ISM) is the name astronomers give to the tenuous gas and dust that pervade interstellar space. ... Cross section of a red giant showing nucleosynthesis and elements formed According to the Hertzsprung-Russell diagram, a red giant is a large non-main sequence star of stellar classification K or M; so-named because of the reddish appearance of the cooler giant stars. ... Supergiants are the most massive stars. ...

Recurrent novae like RS Ophiuchi (those with periods on the order of decades) are rare. Astronomers theorize however that most, if not all novae are recurrent, albeit on time scales ranging from 1,000 to 100,000 years.^[7] The recurrence interval for a nova is less dependent on the white dwarf's accretion rate than on its mass; with their powerful gravity, massive white dwarfs require less accretion to fuel an outburst than lower-mass ones.^[1] Consequently, the interval is shorter for high-mass white dwarfs.^[1]

Historical significance

The astronomer Tycho Brahe observed the supernova SN 1572 in the constellation Cassiopeia, and described it in his book de stella nova (Latin for "concerning the new star"), giving rise to the name nova. In this work he argued that a nearby object should be seen to move relative to the fixed stars, and that the nova had to be very far away. Though this was a supernova and not a classical nova, the terms were considered interchangeable until the 1930s.^[1] Tycho Brahe Monument of Tycho Brahe and Johannes Kepler in Prague   , born Tyge Ottesen Brahe (December 14, 1546 – October 24, 1601), was a Danish (Scanian) nobleman best known today as an early astronomer, though in his lifetime he was also well known as an astrologer and alchemist. ... X-ray image of the expanding cloud of debris and high energy electrons from Tychos supernova. ... Cassiopeia is a northern constellation which Greek mythology considered to represent a vain queen. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... The 1930s (years from 1930-1939) were described as an abrupt shift to more radical and conservative lifestyles, as countries were struggling to find a solution to the Great Depression, also known in Europe as the World Depression. ...

Novae as distance indicators

Novae have some promise for use as standard candles. For instance, the distribution of their absolute magnitude is bimodal, with a main peak at magnitude -7.5, and a lesser one at -8.8. Novae also have roughly the same absolute magnitude 15 days after their peak (-5.5). Comparisons of nova-based distance estimates to various nearby galaxies and galaxy clusters with those done with Cepheid variable stars have shown them to be of comparable accuracy.^[8] A standard candle is an astronomical object that has a known luminosity. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... In statistics, a bimodal distribution is a distribution with two different peaks — that is, there are two distinct values that measurements tend to center around. ... This article is about a celestial body. ... ... A Cepheid variable is a member of a particular class of variable stars, notable for a fairly tight correlation between their period of variability and absolute stellar luminosity. ... Most stars are of nearly constant luminosity. ...

References

1. ^ ^{a b c d e f g h i} Prialnik, Dina. "Novae", pp. 1846-56, in Paul Murdin, ed. Encyclopedia of Astronomy and Astrophysics. London: Institute of Physics Publishing Ltd and Nature Publishing Group, 2001. ISBN 1-56159-268-4
2. ^ AAVSO Variable Star Of The Month: May 2001: Novae
3. ^ Brian Warner. Cataclysmic Variable Stars. 052154209X.
4. ^ Zeilik, Michael. Conceptual Astronomy. New York: John Wiley & Sons, Inc., 1993. ISBN 0-471-50996-5
5. ^ Muirden, James. "Searching for Novae", pp. 259-79. In James Muirden, ed., Sky Watcher's Handbook. New York: W.H. Freeman and Company Ltd., 1993. ISBN 0-7167-4502-X
6. ^ W. Liller, B. Mayer, July 1987, "The rate of nova production in the Galaxy", Publications Astronomical Society of the Pacific, vol. 99, pp. 606-609.
7. ^ Seeds, Michael A. Horizons: Exploring the Universe, 5th ed. Belmont: Wadsworth Publishing Company, 1998, ISBN 0-534-52434-6, p.194.
8. ^ Alloin, D., and W. Gieren, eds. Stellar Candles for the Extragalactic Distance Scale. Robert Gilmozzi and Massimo Della Valle, "Novae as Distance Indicators", pp. 229-241. Berlin: Springer, 2003. ISBN 3-540-20128-9.

The American Association of Variable Star Observers (AAVSO) is an organization that collects observations of variable stars by amateur astronomers and uses them to establish light curves for each stars variation in brightness over time. ...

Bright novae since 1890

Note: Please add all novae brighter than 6 mag [1] Year 1891 (MDCCCXCI) was a common year starting on Thursday (link will display the full calendar). ... T Aurigae (or Nova Aurigae 1892) was a nova, which lit up in the constellation Auriga in 1892. ... 1898 (MDCCCXCVIII) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar (or a common year starting on Monday of the 12-day-slower Julian calendar). ... V1059 Sagittarii was a nova, which lit up in 1898 in the constellation Sagittarius. ... 1899 (MDCCCXCIX) was a common year starting on Sunday (see link for calendar). ... V606 Aquilae was a nova, which lit up in the constellation Aquila in 1899. ... 1901 (MCMI) was a common year starting on Tuesday (see link for calendar) of the Gregorian calendar (or a common year starting on Wednesday of the 13-day-slower Julian calendar). ... GK Persei (also Nova Persei 1901) was a bright nova occuring in 1901 in Perseus. ... 1903 (MCMIII) was a common year starting on Thursday (see link for calendar) of the Gregorian calendar or a common year starting on Friday of the 13-day slower Julian calendar. ... Nova Geminorum 1903 was a Nova, which 1903 in the constellation of twins appeared and reached a brightness of 6 mag. ... 1905 (MCMV) was a common year starting on Sunday (see link for calendar). ... V604 Aquilae was a nova, which occured in Aquila in 1905 with a maximum brightness of 7. ... 1910 (MCMX) was a common year starting on Saturday (see link for calendar) of the Gregorian calendar or a common year starting on Sunday of the 13-day slower Julian calendar. ... Nova Lacertae 1910 was a nova, which 1910 in the constellation Lacerta lit up. ... 1912 (MCMXII) was a leap year starting on Monday in the Gregorian calendar (or a leap year starting on Tuesday in the 13-day-slower Julian calendar). ... Nova Geminorum 1912 was a nova, which 1912 in the constellation of Gemini lit up. ... Year 1918 (MCMXVIII) was a common year starting on Tuesday of the Gregorian calendar (see link for calendar) or a common year starting on Wednesday of the Julian calendar. ... V603 Aquilae (or Nova Aquilae 1918) was a bright nova occuring in Aquila in 1918. ... Year 1919 (MCMXIX) was a common year starting on Wednesday (link will display the full calendar). ... HR Lyrae was a nova, which occured in Lyra in 1919 with a brightness of 6. ... Year 1919 (MCMXIX) was a common year starting on Wednesday (link will display the full calendar). ... V849 Ophiuchi was a nova, which lit up in 1919 in Ophiuchus and reached a brightness of 7. ... Year 1920 (MCMXX) was a leap year starting on Thursday. ... V476 Cygni was a nova, which occured in the constellation Cygnus in 1920. ... 1925 (MCMXXV) was a common year starting on Thursday (link will take you to calendar). ... RR Pictoris was a nova, which lit up in the constellation Pictor in 1925. ... 1934 (MCMXXXIV) was a common year starting on Monday (link will take you to calendar). ... DQ Herculis (or Nova Herculis 1934) was a slow bright nova occurring in Hercules in December 1934. ... 1936 (MCMXXXVI) was a leap year starting on Wednesday (link will take you to calendar). ... CP Lacertae was a nova, which lit up in 1936 in the constellation Lacerta. ... 1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ... BT Monocerotis was a nova, which lit up in the constellation Monoceros in 1939. ... Year 1942 (MCMXLII) was a common year starting on Thursday (the link is to a full 1942 calendar). ... CP Puppis (or Nova Puppis 1942) was a bright nova occurring in the constellation Puppis in 1942. ... Year 1943 (MCMXLIII) was a common year starting on Friday (the link is to a full 1943 calendar). ... Nova Aquilae 1943 was a nova, which 1943 in the constellation eagle appeared and which reached a brightness of 6,1 mag. ... 1950 (MCML) was a common year starting on Sunday (link will take you to calendar). ... DK Lacertae was a nova, which lit up in the constellation Lacerta in 1950. ... Year 1960 (MCMLX) was a leap year starting on Friday (the link is to a full 1960 calendar). ... V446 Herculis was a nova in the constellation Hercules in 1960. ... 1963 (MCMLXIII) was a common year starting on Tuesday (the link is to a full 1963 calendar). ... V533 Herculis was a nova which occurred in 1963 in the constellation Hercules. ... 1970 (MCMLXX) was a common year starting on Thursday (the link is to a full 1970 calendar). ... FH Serpentis was a nova, which appeared in the constellation Serpens in 1970. ... 1975 (MCMLXXV) was a common year starting on Wednesday. ... V1500 Cygni or Nova Cygni 1975 was a bright nova occuring in 1975 in the constellation Cygnus. ... 1975 (MCMLXXV) was a common year starting on Wednesday. ... V373 Scuti was a nova, which appeared in 1975 in the constellation Scutum and reached magnitude 6. ... 1976 (MCMLXXVI) was a leap year starting on Thursday. ... NQ Vulpeculae was a nova with a maximum brightness of 6th magnitude (October 21, 1976) appearing in the constellation Vulpecula. ... 1978 (MCMLXXVIII) was a common year starting on Sunday. ... V1668 Cygni was a nova which appeared in the constellation Cygnus in 1978 with a maximum brightness of 6th mag. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... QU Vulpeculae was a nova, which occured in 1984 in the constellation Vulpecula and which reached a brightness of 5. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... V842 Centauri was a nova which occurred in 1986 in the constellation Centaurus and which reached a brightness of 4. ... 1991 (MCMXCI) was a common year starting on Tuesday of the Gregorian calendar. ... V838 Herculis was a nova which occurred in the constellation Hercules in 1991 and which reached magnitude 5. ... 1992 (MCMXCII) was a leap year starting on Wednesday. ... V1974 Cygni or Nova Cygni 1992 was a relatively bright nova in the constellation Cygnus. ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... V1494 Aquilae was a nova which occurred in 1999 in the constellation Aquila and which reached a brightness of 5. ... 1999 (MCMXCIX) was a common year starting on Friday, and was designated the International Year of Older Persons by the United Nations. ... V382 Velorum was a bright nova, which occured in 1999 in the southern constellation Vela. ... 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... RS Ophiuchi (RS Oph) is a nova approximately 1,950 light-years away in the constellation Ophiuchus. ...

Recurrent novae

• RS Ophiuchi
• T Coronae Borealis
• T Pyxidis

RS Ophiuchi (RS Oph) is a nova approximately 1,950 light-years away in the constellation Ophiuchus. ... T Coronae Borealis is a recurring Nova in Corona Borealis. ... T Pyxidis is a recurrent nova in the constellation Pyxis. ...

Notes

• Under the Morgan-Keenan spectral classification scheme, novae are classified as Type-Q.

In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ...

See also

• Cataclysmic variable
• Crab Nebula
• Dwarf nova
• Hypernova
• Nova remnant
• Supernova

Artists conception of a cataclysmic variable system Cataclysmic variables are a class of binary stars containing a white dwarf and a companion star. ... The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant in the constellation of Taurus. ... A dwarf nova is a type of cataclysmic variable, consisting of a close binary star system in which one of the components is a white dwarf, which accretes matter from its companion. ... A hypernova is a theoretical type of supernova produced when an exceptionally large star collapses at the end of its lifespan. ... A nova remnant is made up of the materials left behind by the gigantic explosion of a star in a nova. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ...

External links

• General Catalog of Variable Stars, Sternberg Astronomical Institute, Moscow
• NASA Observatorium: Classical Nova

Sternberg Astronomical Institute is a research institution in Moscow, Russia, division of Moscow State University. ... Location Position of Moscow in Europe Government Country District Subdivision Russia Central Federal District Federal City Mayor Yuriy Luzhkov Geographical characteristics Area  - City 1,081 km² Population  - City (2005)    - Density 10,415,400   8537. ...