Red supergiant star braces for dusty wall collision

Posted by Thomas Anderson

The European Space Agency's (ESA) Herschel space observatory has identified multiple arcs around Betelgeuse, the nearest red supergiant star to Earth.

According to astronomers, both the star and its arc-shaped shields could collide with an intriguing dusty ‘wall’ in 5000 years.

Betelgeuse rides on the shoulder of the constellation Orion the Hunter. It can be easily observed with the naked eye in the northern hemisphere winter night sky as the orange–red star above and to the left of Orion’s famous three-star belt.

Approximately 1,000 times the diameter of our Sun and shining 100,000 times more brightly, Betelgeuse’s rather impressive statistics come with a cost. To be sure, this star is likely on its way to a spectacular supernova explosion, having swelled into a red supergiant and shed a significant fraction of its outer layers.

As you can see in the image above, 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 most likely resulted in localized, 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 hypothesize that this bar was a result of material ejected during a previous stage of stellar evolution, analysis of the new image suggests it is either a linear filament linked to the Galaxy’s magnetic field, or perhaps even 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 5,000 years, with the red supergiant star itself hitting the bar roughly 12,500 years later.