A Mysterious Star

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A Mysterious Star

Eta Carinae is situated approximately 7,500 light-years from Earth in the constellation Carina, which makes it a relatively nearby star. Nevertheless, there is no definite evidence showing that Eta Carinae was observed before the 17th century. However, the German navigator, Pieter Keyser (1540-1596) did describe seeing a fourth-magnitude star that well may have been Eta Carinae. The star that Pieter Keyser observed around 1595-1596, was at the correct position for it to have been this mysterious star. In turn, Keyser’s observations were copied onto the celestial globes of the Dutch-Flemish astronomer Petras Plancius (1552-1622) and the French engraver and cartographer Jodocus Hondius (1563-1612), as well as the 1603 Uranometricia of the German lawyer and astronomer Johann Bayer (1572-1625). The Dutch explorer Frederick de Houtman’s (1571-1627) independent star catalogue, also produced in 1603, does not include Eta Carinae among the other 4th magnitude stars located in that region.

The first known reliable observation was produced by the English astronomer Edmond Halley (1656-1742) in 1677, when he recorded the star dismissively as Sequens–meaning “following” relative to another star within a newly discovered constellation then dubbed Robur Carolinum. Halley’s Catalogus Stellarum Australium was published in 1679. The mysterious star was also recognized and named Eta Roboris Caroli, Eta Argus, or Eta Navis. Eta was observed in what was later to be known as the constellation Carina. However, it was not generally known as Eta Carinae until 1879, when the stars of Argo Navis were finally designated as the daughter constellations situated in the Uranometria Argentina of the American astronomer Benjamin Apthorp Gould (1824-1896).

Halley determined an approximate apparent magnitude for Eta Carinae of “4” at the time of his discovery, which was later calculated to be magnitude 3.3 on the scale used by astronomers today. Several possible earlier observations indicate that Eta Carinae did not grow much brighter than this for most of the 17th century.

However, Eta Carinae brightened in 1837 from a 4th magnitude star to become brighter than the star Rigel. This proved to be the beginning of what is called its Great Eruption. Indeed, Eta Carinae became the second-brightest star in the sky between March 11 and March 14 1843. After 1856, it began to fade well below what the unaided human eye is able to see. A smaller eruption followed soon thereafter, when Eta Carinae reached 6th magnitude in 1892, before growing dim again. Since 1940, it has brightened consistently, growing brighter than magnitude 4.5 by 2014.

The blue-white star Rigel (Beta Orionis) is usually the 7th brightest star suspended in the dark night sky above our planet, as well as the brightest star in the Orion Constellation. However, it is occasionally out-dazzled within its constellation by the variable star Betelgeuse.

The duo of main stars within the Eta Carinae system display an eccentric orbit with a period of 5.54 years. The primary star is a true “oddball”, similar to a luminous blue variable, that started out at a hefty 150-250 solar-masses. However, the primary has shed at least 30 solar-masses already, and it is expected to go supernova in the near future. The behemoth star has the distinction of being the only one of its gigantic searing-hot kind known to produce ultraviolet laser emission. The secondary star of the fiery duo is extremely luminous–and very hot. This star is probably of spectral class O, and it weighs-in at an impressive 30 to 80 times solar-mass. The system is heavily blanketed by the Homunculus Nebula, which is composed of material hurled out from the primary during the Great Eruption. It is a dazzling denizen of the Trumpfer 16 open stellar cluster situated within the considerably larger Carina Nebula.

At the beinning of the 19th century, the binary Eta Carinae was very dim and unremarkable in appearace. However, its looks began to change during the first decades of that century as it grew ominously brighter. In 1843, Eta Carinae had become the second-brightest star in Earth’s night sky, out-dazzled only by the brilliant “dog star” Sirius–in spite of the fact that Sirius is one thousand times closer to us.

In 1827, the English botanist and traveler W.J. Burchell noticed the bizarre light display performed by Eta Carinae when it became a 1st magnitude star. Because of this, Burchell became the first to suspect that it varied in brightness. The English astronomer John Herschel (1792-1871) made a detailed list of accurate measurements in the 1830s revealing that Eta Carinae consistently glared at approximately magnitude 1.4–that is, until November 1837. On the night of December 16, 1837, Herschel stared up at the sky in amazement because this was when Eta Carinae suddenly and dramatically brightened sufficiently to out-shine Rigel–thus heralding the Great Eruption.

Observations conducted in radio, infrared, and in space have greatly expanded astronomical studies of Eta Carinae across all wavelengths of the electromagnetic spectrum. These studies revealed continuing alterations in the spectral energy distribution.

Finally, in July 2018, Eta Carinae was reported to have the most powerful colliding wind shock in our Sun’s general neighborhood in the Milky Way Galaxy. Observations conducted with NASA’s NuSTAR satellite provided greater resolution data that earlier studies using the Fermi Gamma-ray Space Telescope. By using direct focusing observations of the non-thermal source in the extremely hard X-ray band that is spatially coincident with the mysterious star, they showed that the source of the non-thermal X-rays varies with the orbital phase of the binary star system. Furthermore, the photon index of the emission is similar to that derived through analysis of the gamma-ray spectrum (y-ray).

Only the most massive stars in the Universe give rise to stellar mass black holes after they have gone supernova. The unstable, dying behemoth star of the Eta Carinae system is certainly massive enough to collapse into a black hole when it has finally reached the end of that long stellar road. But, it is such an extremely massive star that it may very well perish in a special–and spectacular–type of supernova blast called a pair-instability supernova. Pair-instability supernovae leave nothing at all behind–not even a black hole. u can download movie 720p mkv movie download in this link

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