NationMaster - Encyclopedia: Eta Carinae

Eta Carinae (η Carinae or η Car) is a highly luminous hypergiant double star. Estimates of its mass range from 100–150 times the mass of the Sun, and its luminosity is about four million times that of the Sun. Image File history File links Mergefrom. ... The Homunculus Nebula is an emission nebula surrounding the massive star Eta Carinae. ... A huge, billowing pair of gas and dust clouds are captured in this NASA Hubble Space Telescope image of the supermassive star Eta Carinae. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... The Homunculus Nebula is an emission nebula surrounding the massive star Eta Carinae. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... Photo of the familiar constellation Orion. ... Carina (IPA: , Latin: ) is a southern constellation which forms part of the old constellation of Argo Navis. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... This article or section contains a plot summary that is overly long or excessively detailed. ... Also known as S Doradus type stars, a luminous blue variable is a very large, very bright, variable star. ... For the band of the same name, see: Binary Star (band) Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left). ... This article or section is in need of attention from an expert on the subject. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... In astronomy, the solar radius is a unit of length used to express the size of stars and larger objects such as galaxies. ... This article does not cite any references or sources. ... The solar luminosity, , is a unit of luminosity (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars. ... For other uses, see Temperature (disambiguation). ... For other uses, see Kelvin (disambiguation). ... The globular cluster M80. ... This illustration shows the oblate appearance of the star Achernar caused by rapid rotation. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A star catalogue, or star catalog, is an astronomical catalog that lists stars. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... The Henry Draper Catalogue is an astronomy catalogue with astrometric and spectroscopic data about more than 225,000 stars. ... Smithsonian Astrophysical Observatory Star Catalog contain the 258,996 stars. ... This article does not cite any references or sources. ... This article does not cite its references or sources. ... For the band of the same name, see: Binary Star (band) Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left). ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... This article or section is in need of attention from an expert on the subject. ... Sol redirects here. ...

Significance

This object is currently the most massive nearby star that can be studied in great detail. While it is possible that other known stars might be more luminous and more massive, Eta Carinae has the highest confirmed luminosity based on data across a broad range of wavelengths; former prospective rivals such as the Pistol Star have been demoted by improved data. Below is a list of stars arranged in order of increasing absolute bolometric magnitude (decreasing luminosity). ... This is a list of the most massive stars. ... The Pistol Star, once thought to be the brightest star in the Milky Way galaxy (exceeded only by LBV-1806), is 10 million times as bright as the Sun and about 100 times as massive. ...

Stars in the weight class of Eta Carinae, with more than 100 times the mass of the Sun, produce more than a million times as much light. They are quite rare — only a few dozen in a galaxy as big as the Milky Way. They are assumed to approach (or potentially exceed) the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in its radiation and gas, resulting in a possible supernova or hypernova in the near future. For other uses, see Milky Way (disambiguation). ... In physics, the Eddington Limit is a natural limit to the luminosity that can be radiated by spherically symmetric accretion onto a compact object, like a black hole. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... This article needs additional references or sources for verification. ...

Eta Carinae's chief significance for astrophysics is based on its giant eruption or supernova impostor event seen around 1843. In a few years, Eta Carinae produced almost as much visible light as a supernova explosion, but it survived. Other supernova impostors have been seen in other galaxies, for example the false supernovas SN 1961v in NGC 1058^[1] and SN 2006jc in NGC 4904^[2], which produced a false supernova in October 2004. Significantly, SN 2006jc was destroyed in a supernova explosion two years later, on October 9, 2006^[3]. The supernova impostor phenomenon may represent a surface instability^[4] or a failed supernova. Eta Carinae's giant eruption was the prototype for this phenomenon, and after 160 years the star's internal structure has not fully recovered. Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 282nd day of the year (283rd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

This object is located in the constellation Carina (right ascension 10 h 45.1 m, declination −59°41m), about 7,500 to 8,000 light-years from the Sun. It is not typically visible north of latitude 27°N. Photo of the familiar constellation Orion. ... Carina (IPA: , Latin: ) is a southern constellation which forms part of the old constellation of Argo Navis. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ... Sol redirects here. ...

The Homunculus Nebula is an emission nebula surrounding the massive star Eta Carinae. ... NGC 3372, the Eta Carinae Nebula. ... The Pleiades is one of the most famous open clusters. ...

Brightness variations

One remarkable aspect of Eta Carinae is its changing brightness. It is currently classified as a luminous blue variable (LBV) double star. A luminous blue variable is a very large, very bright, variable star. ... This article or section contains a plot summary that is overly long or excessively detailed. ... For the band of the same name, see: Binary Star (band) Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left). ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ...

When Eta Carinae was first catalogued in 1677 by Edmond Halley, it was of the 4th magnitude, but by 1730, observers noticed it had brightened considerably, and was at that point one of the brightest stars in Carina. Subsequently it dimmed again, and by 1782 was back to its former obscurity, but in 1820 it started growing in brightness again. By 1827 it had brightened more than tenfold, and reached its greatest brightness in April 1843: with a magnitude of −0.8 it was the second brightest star in the night-time sky (after Sirius at 8.6 light years away), despite its enormous distance of 7,000–8,000 light-years. (To put the relationship in perspective, the relative brightness would be like comparing a candle (Sirius) at 14.5 meters (48 feet) to another light (Eta Carinae) on the horizon of our planet 10km (6.2miles) away, which would appear almost as bright as the candle.) 1677 (MDCLXXVII) was a common year starting on Friday of the Gregorian calendar (or a common year starting on Monday of the 10-day slower Julian calendar). ... // Portrait of Edmond Halley painted around 1687 by Thomas Murray (Royal Society, London) Portrait of Edmond Halley Bust of Edmond Halley in the Museum of the Royal Greenwich Observatory Edmond Halley FRS (sometimes Edmund; IPA: ) (November 8, 1656 â€“ January 14, 1742) was an English astronomer, geophysicist, mathematician, meteorologist, and physicist. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... Events Pope Clement XII elected September 17 - Change of emperor of the Ottoman Empire from Ahmed III (1703-1730) to Mahmud I (1730-1754) Anna Ivanova (Anna I of Russia) became czarina Births April 16 - Henry Clinton, British general (d. ... 1782 was a common year starting on Tuesday (see link for calendar). ... 1820 was a leap year starting on Saturday (see link for calendar). ... Year 1827 (MDCCCXXVII) was a common year starting on Monday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Wednesday of the 12-day slower Julian calendar). ... Year 1843 (MDCCCXLIII) was a common year starting on Sunday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Friday of the 12-day slower Julian calendar). ... For other uses, see Sirius (disambiguation). ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ...

Eta Carinae sometimes has large outbursts, the last one just around its brightness maximum, in 1841. The reason for these outbursts is not yet known. The most likely possibility is believed to be that they are caused by built-up radiation pressure from the star's enormous luminosity. 1841 is a common year starting on Friday (link will take you to calendar). ... Radiation pressure is the pressure exerted upon any surface exposed to electromagnetic radiation. ... This article does not cite any references or sources. ...

After 1843 Eta Carinae faded away, and between about 1900 and 1940 it was only of the 8th magnitude: invisible to the naked eye.^[5] Year 1843 (MDCCCXLIII) was a common year starting on Sunday (link will display the full calendar) of the Gregorian Calendar (or a common year starting on Friday of the 12-day slower Julian calendar). ... Äž: For the film, see: 1900 (film). ... Year 1940 (MCMXL) was a leap year starting on Monday (link will display the full 1940 calendar) of the Gregorian calendar. ...

A "spectroscopic minimum" or "X-ray eclipse" occurred in the midsummer of 2003. Astronomers organized a large observing campaign, which included every available ground-based (e.g. CCD optical photometry^[6]) and space observatory, including major observations with the Hubble Space Telescope, the Chandra X-ray Observatory, the INTEGRAL Gamma-ray space observatory, and the Very Large Telescope. Primary goals of these observations were to determine if in fact Eta Carinae is a binary star; if so, to identify its companion star; to determine the physical mechanism behind the "spectroscopic minima"; and to understand their relation (if any) to the large scale eruptions of the 19th century. Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... The Chandra X-ray Observatory is a satellite launched on STS-93 by NASA on July 23, 1999. ... This article is about the concept of integrals in calculus. ... One of the four telescopes that make up the VLT, named Kueyen. ... For the band of the same name, see: Binary Star (band) Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left). ...

Falceta-Gonçalves and co-workers^[7] have found good agreements between the X-rays' light curve and the evolution on a wind-wind collision zone of a binary system. Their results were complemented by new tests on radio wavelengths.

Spectrographic monitoring of Eta Carinae^[8] showed that some emission lines faded precisely every 5.52 years, and that this period was stable for decades. The star's radio emission,^[9] along with its X-ray brightness,^[10] also drop precipitously during these "events" as well. These variations, along with ultra-violet observations gives very high probability for the scenario that Eta Carinae is actually a binary star, in which a hot, lower mass star revolves around η Carinae in a 5.52-year, highly eccentric elliptical orbit.^[11] For the band of the same name, see: Binary Star (band) Hubble image of the Sirius binary system, in which Sirius B can be clearly distinguished (lower left). ...

Kashi and Soker^[12] studied the propagation of the ionizing radiation emitted by the secondary star in Eta Carinae. A large fraction of this radiation is absorbed by the primary stellar wind, mainly after it encounters the secondary wind and passes through a shock wave. The amount of absorption depends on the compression factor of the primary wind in the shock wave. The compression factor is limited by the magnetic pressure in the primary wind. The variation of the absorption by the post-shock primary wind with orbital phase changes the ionization structure of the circumbinary gas and can account for the radio light curve of Eta Car. Fast variations near periastron passage are attributed to the onset of the accretion phase. A solar wind is a stream of particles (mostly high-energy protons ~ 500 keV) which are ejected from the upper atmosphere of a star (in the case of a star other than the Earths Sun, it may be called a stellar wind instead). ... Introduction The shock wave is one of several different ways in which a gas in a supersonic flow can be compressed. ... A diagram of Keplerian orbital elements. ...

Eta Carinae suddenly and unexpectedly doubled its brightness in 1998–1999. Currently (2007) it can be easily seen with the naked eye, because it is brighter than magnitude 4.7.^{[citation needed]} Year 1998 (MCMXCVIII) was a common year starting on Thursday (link will display full 1998 Gregorian calendar). ... This article is about the year. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st Century. ...

Future prospects

Very large stars like Eta Carinae use up their fuel very quickly because of their disproportionately high luminosities. Eta Carinae is expected to explode as a supernova or hypernova after about 1 million years or less from now, or perhaps less than several millennia, but as its current age is uncertain, it could explode at any time. However, LBVs such as Eta Carinae may be a stage in the evolution of the most massive stars; the prevailing theory now holds that they will exhibit extreme mass loss and become Wolf-Rayet Stars before they go supernova, if they are unable to hold their mass to explode as a hypernova.^[13] Image File history File links Size of this preview: 800 Ã— 387 pixelsFull resolution (1000 Ã— 484 pixel, file size: 224 KB, MIME type: image/jpeg) A diagram of the Eta Carinae Nebula. ... Image File history File links Size of this preview: 800 Ã— 387 pixelsFull resolution (1000 Ã— 484 pixel, file size: 224 KB, MIME type: image/jpeg) A diagram of the Eta Carinae Nebula. ... The Hubble Space Telescope (HST) is a telescope in orbit around the Earth, named after astronomer Edwin Hubble. ... Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... This article needs additional references or sources for verification. ... Also known as S Doradus type stars, a luminous blue variable is a very large, very bright, variable star. ... Artists impression of a Wolf-Rayet star Wolf-Rayet stars (often referred to as WR stars) are evolved, hot, massive stars which have very strong stellar winds. ...

More recently another possible Eta Carinae analogue was observed; namely SN 2006jc some 77 million light years away in UGC 4904, in the constellation of Lynx.^[14] It brightened on 20 October 2004 and was reported by amateur astronomer Koichi Itagaki as supernova. However, it survived and finally exploded two years later as a Mag 13.8 type Ib supernova on 9 October 2006. Its earlier brightening was a supernova impostor event; the initial explosion hurled 0.01 solar masses (~20 Jupiters) of material into space.

Due to the similarity of Eta Carinae and SN 2006jc, Stefan Immler of NASA's Goddard Space Flight Center suggests that Eta Carinae could explode in our lifetime or even in the next few years. However, Stanford Woosley of the University of California in Santa Cruz disagrees with Immler’s suggestion, and he says it is likely that Eta Carinae is at an earlier stage of evolution and that it has several kinds of material left for nuclear fusion.

Another recent analog star explosion was supernova SN 2006gy, observed starting on September 18, 2006 in NGC 1260 (a spiral galaxy in the constellation Perseus) 238 million light years from earth. A number of astronomers modelling supernova events have suggested that the explosion mechanism for SN 2006gy may be very similar to the fate that awaits Eta Carinae. SN 2006gy and the core of its home galaxy, NGC 1260, viewed in x-ray light from the Chandra X-ray Observatory. ... is the 261st day of the year (262nd in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

It is possible that the Eta Carinae hypernova or supernova could affect Earth, about 7,500 light years away, but would not likely affect humans directly, who are protected from gamma rays by the atmosphere. The damage would likely be restricted to the upper atmosphere, the ozone layer, spacecraft, including satellites, and any astronauts in space. At least one scientist has claimed that if the star were to explode, "it would be so bright that you would see it during the day, and you could even read a book by its light at night".^[15] A supernova or hypernova produced by Eta Carinae would probably shoot a gamma ray burst out on both sides in the direction of its rotation axis. This catastrophic burst would probably not hit earth though, because the rotation axis does not currently point at us. Since Eta Carinae is at least a double star, or even a triple star, examined due to its short brightness and X-ray variation period, this may either increase or decrease the intensity of the supernova or hypernova it produces depending on the circumstances.[1] A light year, abbreviated ly, is the distance light travels in one year: roughly 9. ... This article is about electromagnetic radiation. ... The image above shows the optical afterglow of gamma ray burst GRB-990123 taken on January 23, 1999. ... When two stars are so nearly in the same direction as seen from Earth that they appear to be a single star to the naked eye but may be separated by the use of telescopes, they are referred to as a double star. ...

Contents

Significance

Brightness variations

Future prospects

See also

References

External links

Contents

Significance GA_googleFillSlot("encyclopedia_square");

Brightness variations

Future prospects

See also

References

External links

Significance