January 25th, 2013 by James Ayre
Betelgeuse, an enormous red supergiant star (the closest one to the Earth), has been revealed, in a new image from the ESA’s Herschel space observatory, to be rapidly approaching an a somewhat strange ‘wall’ of dust. The outer reaches of the star will likely impact with the wall in around 5,000 years.
Betelgeuse is one of the most visible stars in the nights sky, it’s located right on the shoulder of the constellation Orion the Hunter. Those living in the northern hemisphere can see the star on any clear winter night, it’s the bright orangish-red star over and to the left of the famous three-star belt of Orion.
“Roughly 1000 times the diameter of our Sun and shining 100,000 times more brightly, Betelgeuse’s impressive statistics come with a cost. For this star is likely on its way to a spectacular supernova explosion, having already swelled into a red supergiant and shed a significant fraction of its outer layers.”
“The new far-infrared view from Herschel shows how the star’s winds are crashing against the surrounding interstellar medium, creating a bow shock as the star moves through space at speeds of around 30 km/s.”
The dusty arcs that are preceding the star are a testament to its loss of mass, these layers were previously part of the star.
“Closer to the star itself, an inner envelope of material shows a pronounced asymmetric structure. Large convective cells in the star’s outer atmosphere have likely resulted in localised, clumpy ejections of dusty debris at different stages in the past.”
“An intriguing linear structure is also seen further away from the star, beyond the dusty arcs. While some earlier theories proposed that this bar was a result of material ejected during a previous stage of stellar evolution, analysis of the new image suggests that it is either a linear filament linked to the Galaxy’s magnetic field, or the edge of a nearby interstellar cloud that is being illuminated by Betelgeuse.”
“If the bar is a completely separate object, then taking into account the motion of Betelgeuse and its arcs and the separation between them and the bar, the outermost arc will collide with the bar in just 5000 years, with the red supergiant star itself hitting the bar roughly 12,500 years later.”
It’s too bad that is so far into the future, as that could be an incredible sight (even better than this year’s Best Astronomical Events). Because of how close Betelgeuse is to us though (640 light years), when the star finally does go supernova, it will be very visible from the Earth. It will be easily brighter than the full moon and visible in broad daylight for many months. Because its rotational axis isn’t directed towards the Earth, researchers think that it is very unlikely that we would be hit by gamma ray bursts from the explosion. The best current estimates say that it will go supernova at some point in the next million years, but not anytime soon.
The mythologies of various peoples around the world feature some interesting stories related to the star. “In the Americas, Betelgeuse signifies a severed limb of a man-figure (Orion)—the Taulipang of Brazil know the constellation as Zililkawai, a hero whose leg was cut off by his wife, with the variable light from Betelgeuse linked to the severing of the limb. Similarly, the Lakota people of North America see it as a chief whose arm has been severed. The Wardaman people of northern Australia knew the star as Ya-jungin ‘Owl Eyes Flicking’, its variable light signifying its intermittent watching of ceremonies led by the Red Kangaroo Leader Rigel. In South African mythology, Betelgeuse was perceived as a lion casting a predatory gaze toward the three zebras represented by Orion’s Belt.”
“The opposed locations of Orion and Scorpio, with their corresponding bright variable red stars Betelgeuse and Antares, were noted by ancient cultures around the world. The setting of Orion and rising of Scorpio signify the death of Orion by the scorpion”, and vice versa. Orion was the human hunter who killed the giant scorpion, and vice-versa in other versions of the story, and was turned into a star by the gods for it. “The positions of Betelgeuse and Antares at opposite ends of the celestial sky were considered significant and their constellations were seen as a pair of scorpions. Scorpion days marked as nights that both constellations could be seen.”
Image Credits: ESA/Herschel/PACS/L. Decin et al; Betelgeuse and Orion via Wikimedia Commons
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