Could the mysterious orbit of Betelgeuse be a cosmic illusion due to its huge ‘boiling’ surface.

 

Recent simulations have shed light on the intriguing behavior of Betelgeuse, revealing the dynamic nature of its surface as blobs of plasma rise and fall, akin to a celestial boiling cauldron.

The colossal star Betelgeuse, potentially on the brink of a cataclysmic explosion, has confounded scientists with its apparent rapid rotation, a phenomenon now attributed to the dynamic nature of its surface rather than true spinning. Betelgeuse, a red supergiant towering around 1,000 times the mass of our sun, holds the distinction of being one of the universe’s largest stars. Its sheer enormity is such that if it were to replace the sun, its vast expanse would engulf the orbit of Jupiter, consigning inner planets like Earth, Mercury, Venus, and Mars to oblivion.

Despite its youth of merely 10 million years, a mere fraction of our sun’s age, Betelgeuse stands precariously on the threshold of celestial demise, having depleted its hydrogen reserves due to its intense heat and mass. This impending fate, likely to unfold within the next few millennia or even within human lifetimes, will culminate in a spectacular supernova event, outshining the moon for weeks on end. Betelgeuse’s fluctuations in brightness add to its mystique, further underscoring the enigmatic nature of this celestial giant nestled within the Orion constellation.

Deciphering Betelgeuse’s Rotation: Synthetic ALMA Observations Unveil Large-scale Convection in 3D Simulations of Red Supergiants.

In 2018, data gathered by the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile unveiled a surprising revelation about Betelgeuse: it was rotating at an astonishing speed of approximately 11,200 mph (18,000 km/h), a rate vastly exceeding the typical rotation expected of red supergiants, which usually spin at least 100 times slower. This anomaly sparked intrigue among researchers, prompting theories to explain such rapid rotation. One hypothesis suggests that Betelgeuse might have consumed a companion star it once orbited, resulting in its accelerated spin. However, not all experts find this explanation convincing, hinting at the complex and enigmatic nature of this celestial phenomenon.

Understanding the evolutionary trajectories of massive stars remains a challenging endeavor, yet crucial insights can be gleaned from detailed observations of nearby red supergiants like Betelgeuse. Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) have revealed a dipolar velocity field in Betelgeuse, suggesting a projected rotation rate of approximately 5 km s−1, significantly higher than predicted by conventional single-star evolutionary models. This discrepancy has led to speculations regarding the possibility of Betelgeuse being a result of a binary merger.

However, an alternative explanation posits that large-scale convective motions could simulate rotational effects, especially when only partially resolved. To support this hypothesis, 3D CO5BOLD simulations of non-rotating red supergiants were conducted, followed by post-processing to predict ALMA images and SiO spectra. The results indicate that synthetic radial velocity maps have a high probability of being misinterpreted as evidence for a projected rotation rate exceeding 2 km s−1, reinforcing the need for additional ALMA observations to conclusively determine Betelgeuse’s rotational status.

Such data not only hold implications for understanding angular momentum and binary interactions during late stellar evolution but also offer invaluable insights into the atmospheric structure and underlying physical processes of red supergiants, pivotal in the context of supernova progenitors and the formation of gravitational-wave sources.

The recent study, published on February 20 in The Astrophysical Journal Letters, offers a fresh perspective on the puzzling observations of Betelgeuse. Researchers propose that the apparent rapid rotation captured by ALMA might not be attributed to the star’s actual spinning but rather to the presence of immense gas bubbles undulating across its surface. Lead author Jing-Ze Ma, a doctoral candidate in stellar astrophysics at the Max Planck Institute for Astrophysics in Germany, explained that stars like Betelgeuse exhibit such pronounced boiling motions on their surfaces that these movements are observable. However, these dynamic motions had been previously misinterpreted, shedding new light on our understanding of this enigmatic celestial entity.

Used computer simulations to model the surface of red supergiants such as Betelgeuse.

In their latest research endeavor, Ma and his team employed advanced computer simulations to replicate the surface characteristics of red supergiants such as Betelgeuse. Unlike our sun, which maintains a relatively spherical shape, these simulations unveiled a dramatic contrast: Betelgeuse’s colossal surface undergoes constant undulations, resembling a shape-shifting mass as immense globules of plasma, surpassing anything seen within our solar system, ascend and descend akin to bubbles in a lava lamp.

When observed through telescopes like ALMA, which possess less resolving power compared to some contemporary counterparts, the upward motion on one side of Betelgeuse could be erroneously interpreted as the star rotating towards the observer, while a downward motion might be misconstrued as the star spinning away from observers, adding further complexity to our understanding of this stellar phenomenon.

After conducting simulations, the team utilized a program designed to replicate the processing capabilities of telescopes like ALMA. Their findings, detailed in the researchers’ statement, indicate that a significant portion—up to 90%—of the simulated stars could be erroneously perceived as exhibiting rotation. Presently, the explanation involving a boiling surface remains speculative, yet the researchers are actively scrutinizing more comprehensive observations of Betelgeuse to validate this hypothesis. Should this theory hold true, it could potentially elucidate the seemingly rapid rotational behaviors observed in several hundred other known red supergiants, as suggested by the researchers.