[18] At the peak of the Great Eruption the radius, so far as such a thing is meaningful during such a violent expulsion of material, would have been around 1,400 R☉, comparable to the largest known stars, including VY Canis Majoris. The signature balloon-shaped clouds of gas blown from a pair of massive stars called Eta Carinae have tantalized astronomers for decades. ejected material have sizes comparable to that of our solar [122] In the case of Eta Carinae, the secondary is clearly causing additional instability in the primary, making it difficult to predict future developments. To match those observations, the models require much higher mass loss rates. [118][119][120] The lack of sufficiently luminous WN stars and the discovery of apparent LBV supernova progenitors has also prompted the suggestion that certain types of LBVs explode as a supernova without evolving further.[121]. At that time, the star began to brighten again, and reached 7th magnitude It is possible that the two stars formed roughly at the same time. [113] Possible explanations for the eruptions include: a binary merger in what was then a triple system;[114] mass transfer from Eta Carinae B during periastron passages;[15] or a pulsational pair-instability explosion. This resulted in the star being shrouded by a cloud of gas and dust. It is the most luminous star of this classification. Both stars appear to be at around 3 million years old. P Cygni profiles (named after By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. The HII and recombination lines vary very strongly, with continuum emission (electromagnetic radiation across a broad band of wavelengths) less affected. [113], Eta Carinae is a unique object, with no very close analogues currently known in any galaxy. The amount of mass being carried away by the wind is the equivalent one sun every thousand years. [2] Further sporadic observations over the next 70 years show that Eta Carinae was probably around 3rd magnitude or fainter, until Lacaille reliably recorded it at 2nd magnitude in 1751. The most massive star in the Milky Way is R136a1, which has over 250 times the mass of the sun. In a few years, it produced almost as much visible light as a faint supernova explosion, but the star survived. Eta Carinae is engulfed by the Homunculus Nebula. The recent visual brightening is considered to be largely caused by a decrease in the extinction, due to thinning dust or a reduction in mass loss, rather than an underlying change in the luminosity.[96]. A very faint structure, seen in argon, is evidence of an interaction between winds from Eta Car A and those of Eta Car B, the hotter, less massive, secondary star. Eta Carinae peaked at a magnitude of 6.2 in 1892 and in 1895 faded rapidly at magnitude 7.5. NASA astronauts repaired STIS during a servicing mission in May to upgrade and repair the 19-year-old Hubble telescope. 1941. Looking for fun activities to teach kids about Eta Carinae? It is about 4 million times brighter than our local star, making it also one An event similar to Eta Carinae A's Great Eruption has been observed in only one other star in the Milky Way – P Cygni – and in a handful of other possible LBVs in other galaxies. Eta Carinae radiates 99 % of its luminosity This is the only star known to produce ultraviolet laser emission. Mirrored lobes of gas and dust surround Eta Carinae’s central stars, which are flanked at right by ragged, shock-heated gas. to violent outbursts. At its brightest in 1843 it likely reached an apparent magnitude of −0.8, then −1.0 in 1845. 30°2′N). per hour, is largely composed of nitrogen and other elements formed Since Eta Carinae is located in the Carina Nebula, the stars may have originated from there. During the 2014 spectroscopic event, the apparent visual magnitude became brighter than magnitude 4.5. The smaller star is about 30 times the mass of the Sun and may be as much as a million times more luminous. In the resulting spectrum, iron and nitrogen define the outer boundary of the massive wind, a stream of charged particles, from Eta Car A, the primary star. At optical depth 0.67 the radius would be over 800 R☉, indicating an extended optically thick stellar wind. This spectral transition from F supergiant to strong emission is characteristic of novae, where ejected material initially radiates like a pseudo-photosphere and then the emission spectrum develops as it expands and thins. material is spraying out in the same plane as the hypothetical Your browser or your browser's settings are not supported. Therefore, its future evolution is highly uncertain, but almost certainly involves further mass loss and an eventual supernova. [104] Eta Carinae is still much brighter at infrared wavelengths, despite the presumed hot stars behind the nebulosity. An effective temperature determined for the surface of a spherical optically thick wind at several hundred R☉ would be 9,400–15,000 K, while the temperature of a theoretical 60 R☉ hydrostatic "core" at optical depth 150 would be 35,200 K.[41][96][19][108] The effective temperature of the visible outer edge of the opaque primary wind is generally treated as being 15,000 K–25,000 K on the basis of visual and ultraviolet spectral features assumed to be directly from the wind or reflected via the Weigelt Blobs. While this "mass loss" may not sound very large, in fact it is an enormous rate among stars of all types. Individual lines show widely varying widths, profiles, and Doppler shifts, often multiple velocity components within the same line. None of them seem to be quite as violent as Eta Carinae's. [17], Direct spectral observations did not begin until after the Great Eruption, but light echoes from the eruption reflected from other parts of the Carina Nebula were detected using the U.S. National Optical Astronomy Observatory's Blanco 4 meter telescope at the Cerro Tololo Inter-American Observatory. By 1895 the spectrum again consisted mostly of strong emission lines, with the absorption lines present but largely obscured by emission. release for this image, as presented at SEDS). More detailed observations were made with the Einstein Observatory,[68] ROSAT X-ray telescope,[69] Advanced Satellite for Cosmology and Astrophysics (ASCA),[70] and Chandra X-ray Observatory. Gaia Data Release 2 has provided the parallax for many stars considered to be members of Trumpler 16, finding that the four hottest O-class stars in the region have very similar parallaxes with a mean value of 0.383 ± 0.017 milli-arcseconds (mas), which translates to a distance of 2,600 ± 100 parsecs. Eta Carinae B is likely to have a well-defined photosphere and its radius can be estimated from the assumed type of star. The highest energy gamma-rays detected were above 100 MeV. In 1730, its brightness reached mag 2, and again fell to mag 4 in about 1782. [8] From 1845 to 1856, the brightness decreased by around 0.1 magnitudes per year, but with possible rapid and large fluctuations. The ionisation levels and continuum require the existence of a source with a temperature at least 37,000 K.[58], Certain FeII UV lines are unusually strong. [95] Both component stars are largely obscured by circumstellar material ejected from Eta Carinae A, and basic properties such as their temperatures and luminosities can only be inferred. The observable radiation originates from a pseudo-photosphere where the optical density of the wind drops to near zero, typically measured at a particular Rossland opacity value such as ​2⁄3. Its brightness decreased from 1845 to 1856 by 0.1 magnitude per year. The total mass of the ejecta from the last outburst is Herschel did not observe the star after this, but received correspondence from the Reverend W.S. Eta Carinae has also been compared to other possible supernova impostors such as SN 1961V and iPTF14hls, and to superluminous supernovae such as SN 2006gy. [27], Halley gave an approximate apparent magnitude of 4 at the time of discovery, which has been calculated as magnitude 3.3 on the modern scale. Since the stars in the Eta Carinae system are engulfed by the Homunculus cloud, it is difficult to determine their exact physical properties. Monocular vs. Binoculars- Which One is Best for Stargazing. It became the second-brightest star in the sky between 11 and 14 March 1843 before fading well below naked eye visibility after 1856.

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