# Exploring Betelgeuse: The Uniquely Boiling Red Supergiant Star
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Chapter 1: Understanding Betelgeuse
Betelgeuse, a red supergiant star, showcases a strikingly different appearance compared to our Sun. Lacking spherical symmetry, it resembles a pot perpetually boiling, with enormous bubbles forming on its surface.
Over three decades of meticulous observations using advanced telescopes and interferometers have provided scientists with a comprehensive understanding of Betelgeuse's photosphere and its expansive atmosphere. This red supergiant has progressed far beyond the main sequence of stellar evolution, resulting in significant growth and the thinning of its outer layers. The intense convective currents within transport the hottest material from the star's interior to the photosphere, creating massive "bubbles" that render Betelgeuse's surface irregular.
Numerous studies conducted in recent decades have confirmed its unconventional appearance. For instance, a pivotal study from 1990 by Buscher, Haniff, Baldwin, and Warner utilized the 4.2-meter William Herschel Telescope with a masking technique to simulate an interferometer. They observed:
> "High-resolution images of the M-supergiant Betelgeuse in February 1989 at various wavelengths reveal a distinct asymmetric feature on its surface, contributing 10-15% of the total observed flux. This may indicate a nearby companion star or, more plausibly, large-scale convection within the stellar atmosphere."
In their findings, they postulated that these surface regions are so expansive that only a few would be present simultaneously.
Section 1.1: The First Direct Images of Betelgeuse
The existence of this asymmetry was corroborated six years later in May 1996 when The Astrophysical Journal published the first direct image of a star's surface, other than the Sun, captured by the Hubble Space Telescope. Betelgeuse was chosen for this groundbreaking observation due to its considerable angular diameter visible from Earth.
The initial image of Betelgeuse's disk was taken on March 3, 1995, showcasing an angular diameter approximately 20,000 times smaller than that of the Moon. Observations revealed an extensive chromosphere, suggesting that the stellar disk's diameter in ultraviolet light was about twice that observed in visible light.
Gilliland and Dupree emphasized:
> "The dominant bright feature in Betelgeuse's atmosphere starkly contrasts with the mottled appearance of the Sun, which typically displays numerous active regions. The unique physical phenomena observed in Betelgeuse's atmosphere could provide insights into energy balance in low-gravity environments."
The first video title is Red supergiant star Betelgeuse's boiling surface 'mimics' rotation in animation. This video presents a visual representation of Betelgeuse's boiling surface and its dynamic features.
Section 1.2: Observations in Far Ultraviolet
In a 2001 article, Timothy, Horch, and Valenti published the first direct image of Betelgeuse in far ultraviolet, revealing an atmosphere extending more than three times the visible diameter of the star. This observation confirmed the extensive and non-uniform nature of Betelgeuse's atmosphere.
More recently, observations using the PIONIER instrument of the Very Large Telescope Interferometer from 2012 to 2014 showed a large bright spot on Betelgeuse's photosphere, which appeared to shift over time. This hot spot likely originated from a massive convection cell, with a temperature approximately 1,000 K higher than the average for Betelgeuse.
The second video title is Furious Boiling of Betelgeuse // Robot-Surgeon on the ISS // Biggest Black Holes Ever Seen. This video explores Betelgeuse's boiling dynamics and compares them to other cosmic phenomena.
Chapter 2: Unraveling the Mysteries of Betelgeuse
The analysis of Betelgeuse's atmosphere has revealed significant asymmetries and varying temperatures. Observations with the ALMA interferometer in 2015 highlighted these features, demonstrating that the star's atmosphere is anything but uniform. The findings from the ALMA observations indicate that the diameter of Betelgeuse's atmosphere is about 1,400 times that of the Sun.
Recent images captured with the SPHERE instrument of the Very Large Telescope in 2019 further illustrated the stark brightness variation and persistent asymmetry of Betelgeuse. Comparing two images from January and December 2019, researchers noted a considerable decrease in brightness alongside the continuous irregularity of the star.
Imagining an Up-Close View of Betelgeuse
If we could observe Betelgeuse from the distance of Pluto, shielded from its intense light, we would likely witness its bubbling, asymmetrical form as depicted in simulations created by astronomer Bernd Freytag.
In summary, the extensive research and observations of Betelgeuse reveal not only its distinct physical characteristics but also the complex phenomena at play within its atmosphere, setting it apart from our familiar Sun.
Notes
- The gravitational force at the photosphere of a red supergiant like Betelgeuse is significantly lower than that of the Sun, estimated at approximately 0.5 cm/s².
This concludes the exploration of Betelgeuse's unique features and characteristics.