Mystery of erupting star uncovered
12 Sep 2016 by qwbdchbctt.d qwbdchbctt.d
Scientists have discovered that a huge supernova-like event seen in the mid-19th century for 20 years had happened more than once before.
Scientists have discovered a huge supernova-like event seen in the mid-19th century for 20 years had also previously occurred in earlier centuries
The Great Eruption between 1837 and 1857 saw Eta Carinae become one of the brightest stars in the sky. The stellar material surrounding the binary star system was hurled into space at speeds reaching two million miles per hour.
Nathan Smith, associate professor at the Department of Astronomy at the University of Arizona (UA), said: “From the first reports of its 19th-century outburst up to the most recent data obtained with advanced capabilities on modern telescopes, Eta Carinae continues to baffle us. The most important unsolved problem has always been the underlying cause of its eruption, and now we find that there were multiple previous eruptions. This is a bit like reconstructing the eruption history of a volcano by discovering ancient lava flows.”Eta Carinae, is located about 7,500 light years away in the southern constellation of Carina. Visible from the Southern Hemisphere, two stars orbit each other every five and a half years. It is surrounded by the Homunculus, an hourglass shaped cloud of glowing gas and dust.
Megan Kiminki, lead author from UA, said: “These are very large stars that appear very volatile, even when they’re not blowing off nebulae. They have a dense core and very fluffy envelopes. If you replaced our sun by the larger of the two, which has about 90 – 100 solar masses, it could very well extend into the orbit of Mars.”
Kiminki and a team of researchers analysed pictures taken by the Hubble Space Telescope and discovered there had been other similar outbursts since the 13th century. They deduced from the slow expansion rate of gas outside the Homunculus that there were two previous eruptions in the mid-13th and 16th century.
The researchers discovered that the older ejected gases were not released from the poles, unlike the Homunculus. Kiminki said: “Even more surprising was that the oldest eruption was very one-sided, suggesting two stars were involved, because it would be very unlikely for one star to blow material out toward just one side."
The scientists are now working on determining the cause for these outbursts. Some non-related studies have theorised a subclass of supernova explosions that are very violent shortly before they finally explode. Eta Carinae may be our nearest example of this.The research was published in arXiv.
