Science Wire

Betelgeuse braces for a collision

fuzzy, faint arcs on one side of star and fuzzy vertical line, see caption
Artist’s concept showing star Betelgeuse (center), with a series of arcs immediately to the left of the star. The arcs are thought to be material ejected from Betelgeuse as it evolved into a red supergiant. Notice the faint linear bar of dust on the left side of the image. It represents a dusty filament connected to our galaxy’s magnetic field, or the edge of an interstellar cloud. If this filament, or wall, exists – as some astronomers believe – the arcs ejected from Betelgeuse will hit the wall 5,000 years from now. Betelgeuse itself will collide with the wall 12,500 years later. Image via ESA/Herschel/PACS/L. Decin et al.

The red star Betelgeuse – in the shoulder of the constellation Orion the Hunter – can be seen easily with the unaided eye at this time of year. Betelgeuse is one of two bright stars (the other is Rigel) above and below Orion’s Belt, a short, straight row of three medium-bright stars. This star is roughly 1,000 times our sun’s diameter and shines some 100,000 times more brightly. But 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.

A series of broken, dusty arcs ahead of the star’s direction of motion testify to a turbulent history of mass loss.

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.


January 22, 2013
Science Wire

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