Red Giant Star Betelgeuse [UPSC Notes]

Research suggests that Betelgeuse will explode in ‘tens of years’. What is Betelgeuse? Is it likely to explode in our lifetime? Read on for more information on the red giant Betelgeuse. This topic is relevant for the IAS exam science and technology segment of GS paper III.

What is Betelgeuse? 

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Betelgeuse, a bright red star in the Orion constellation, is undergoing significant changes. It is also called Alpha Orionis and is the second brightest star in the constellation Orion, marking the eastern shoulder of the hunter. 

• Betelgeuse was born as a supermassive star millions of years ago and has been “dramatically” and “mysteriously” dimming for the last six months.
• Recent research indicates that Betelgeuse may explode as a supernova within a few decades.
• However, there are contrasting opinions and uncertainties regarding the exact timeline and distance of Betelgeuse.

Life Cycle of Massive Stars

• Massive stars like Betelgeuse initially fuse hydrogen into helium to produce energy and maintain stability.
• Eventually, the star exhausts its hydrogen fuel and transitions to burning helium to form carbon.
• This process continues with the fusion of heavier elements until the star’s core is rich in iron.

Betelgeuse’s Late Carbon-Burning Stage

• Betelgeuse’s observed pulsation suggests it is in the late carbon-burning stage, nearing its end.
• The pulsation periods indicate the radius, luminosity, and mass of the star, confirming its advanced stage.

Also read: Runaway Black Holes

Pulsation and Expansion of Red Giants

• Red giant stars like Betelgeuse expand and contract due to periodic heating and cooling of their outermost layers.
• The expansion occurs when hydrogen is ionized, leading to the star’s outer shell being ejected.
• This cyclical process causes the star to appear dimmer and brighter to distant observers.

Conflicting Views on Betelgeuse’s Supernova

Research by Devesh Nandal’s team suggests Betelgeuse is in its final stage of core carbon-burning.

• Their model predicts Betelgeuse’s radius, luminosity, and fundamental pulsation period, aligning with observations.
• Another team led by László Molnár and Meridith Joyce challenges Nandal’s findings, disputing Betelgeuse’s radius and distance.

Uncertainties and Model Dependencies

• Astronomers differ in their estimations of Betelgeuse’s radius, distance, and luminosity.
• Disputes regarding these parameters impact predictions about Betelgeuse’s supernova timeline.
• While the consensus is that Betelgeuse will eventually explode, the exact timing remains uncertain.

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