When Betelgeuse, a bright orange star in the constellation of Orion, became visibly darker in late 2019 and early 2020, the astronomy community was puzzled. A team of astronomers have now published new images of the star’s surface, taken using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), that clearly show how its brightness changed. The new research reveals that the star was partially concealed by a cloud of dust, a discovery that solves the mystery of the “Great Dimming” of Betelgeuse.
Betelgeuse’s dip in brightness — a change noticeable even to the naked eye — led Miguel Montargès and his team to point ESO’s VLT towards the star in late 2019. An image from December 2019, when compared to an earlier image taken in January of the same year, showed that the stellar surface was significantly darker, especially in the southern region. But the astronomers weren’t sure why.
The team continued observing the star during its Great Dimming, capturing two other never-before-seen images in January 2020 and March 2020. By April 2020, the star had returned to its normal brightness. ...
In their new study ... the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse’s stellar surface.
Betelgeuse’s surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust. ...
A dusty veil shading Betelgeuse during its Great Dimming ~ M. Montargès et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
When Betelgeuse, a bright orange star in the constellation of Orion, became visibly darker in late 2019 and early 2020, the astronomy community was puzzled. A team of astronomers have now published new images of the star’s surface, taken using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), that clearly show how its brightness changed. The new research reveals that the star was partially concealed by a cloud of dust, a discovery that solves the mystery of the “Great Dimming” of Betelgeuse.
Betelgeuse’s dip in brightness — a change noticeable even to the naked eye — led Miguel Montargès and his team to point ESO’s VLT towards the star in late 2019. An image from December 2019, when compared to an earlier image taken in January of the same year, showed that the stellar surface was significantly darker, especially in the southern region. But the astronomers weren’t sure why.
The team continued observing the star during its Great Dimming, capturing two other never-before-seen images in January 2020 and March 2020. By April 2020, the star had returned to its normal brightness. ...
In their new study ... the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse’s stellar surface.
Betelgeuse’s surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust. ...
A dusty veil shading Betelgeuse during its Great Dimming ~ M. Montargès et al
I'm sure the regular fadings of yellow supergiant star R Coronae Borealis are not caused by the same mechanism that caused the great fading of Betelgeuse, but it seems to me that there are some similarities.
At irregular intervals a few years or decades apart R Coronae Borealis fades from its normal brightness near 6th magnitude for a period of months or sometimes years. There is no fixed minimum, but the star can become fainter than 15th magnitude in the visual range. The fading is less pronounced at longer wavelengths.
Typically the star starts to return to maximum brightness almost immediately from its minimum, although occasionally this is interrupted by another fade. The cause of this behaviour is believed to be a regular build-up of carbon dust in the star's atmosphere.
The sudden drop in brightness may be caused by a rapid condensation of carbon-rich dust similar to soot, resulting in much of the star's light being blocked. The gradual restoration to normal brightness results from the dust being dispersed by radiation pressure.
https://hitchhikers.fandom.com/wiki/Great_Collapsing_Hrung_Disaster wrote:
<<The Great Collapsing Hrung Disaster of Gal./Sid./Year 03758 which wiped out all the old Praxibetel communities on Betelgeuse VII is shrouded in deep mystery; in fact, no one ever knew what a Hrung was nor why it had chosen to collapse on Betelgeuse VII particularly.
Ford Prefect's father/uncle was the only man on the entire planet to survive the Great Collapsing Hrung disaster, by an extraordinary coincidence that he was never able satisfactorily to explain, a lack which led to considerable social embarrassment. Ford's Betelgeusian nickname, Ix, was based on this fact.
In the real universe, sudden dimming of Betelgeuse began to be noticed in early 2020. Nobody is sure what is causing this stellar fainting, although there is a chance it could be a sign of an imminent explosion. Analysis suggests that it is possible that Betelgeuse could explode any time between "now and 100,000 years from now". Since Betelgeuse is roughly 700 light years from Earth, this would date the Great Collapsing Hrung Disaster to anytime from the 14th to 23rd century CE.
“Ford Prefect’s original name is only pronounceable in an obscure Betel-geusian dialect, now virtually extinct since the Great Collapsing Hrung Disaster of Gal./Sid./Year 03758 which wiped out all the old Praxibetel communities on Betelgeuse Seven. Ford’s father was the only man on the entire planet to survive the Great Collapsing Hrung Disaster, by an extraordinary coincidence that he was never able satisfactorily to explain. The whole episode is shrouded in deep mystery: in fact no one ever knew what a Hrung was nor why it had chosen to collapse on Betelgeuse Seven particularly. Ford’s father, magnanimously waving aside the clouds of suspicion that had inevitably settled around him, came to live on Betelgeuse Five, where he both fathered and uncled Ford; in memory of his now dead race he christened him in the ancient Praxibetel tongue. Because Ford never learned to say his original name, his father eventually died of shame, which is still a terminal disease in some parts of the Galaxy. The other kids at school nicknamed him Ix, which in the language of Betelgeuse Five translates as “boy who is not able satisfactorily to explain what a Hrung is, nor why it should choose to collapse on Betelgeuse Seven.”
― Douglas Adams, The Hitchhiker's Guide to the Galaxy
<<Ford Prefect is a fictional character in The Hitchhiker's Guide to the Galaxy by the British author Douglas Adams. His role as Arthur Dent's friend – and rescuer, when the Earth is unexpectedly demolished to make way for a hyperspace bypass at the start of the story – is often expository, as Ford is an experienced galactic hitch-hiker and explains that he is actually an alien journalist, a field researcher for the titular Guide itself, and not an out-of-work actor from Guildford as he had hitherto claimed. While not explained in the book, a footnote of the original radio scripts explains that "just before arriving (on Earth) he registered his new name officially at the Galactic Nomenclaturoid Office, where they had the technology to unpick his old name from the fabric of space/time and thread the new one in its place, so that for all intents and purposes his name had always been and would always be Ford Prefect."
Although Ford had taken great care to blend into Earth society, he had "skimped a bit on his preparatory research," and thought that the name "Ford Prefect" would be "nicely inconspicuous." The Ford Prefect was a popular British car manufactured from 1938 to 1961, and Adams later clarified in an interview that Ford "had simply mistaken the dominant life form" of Earth. This was expanded on somewhat in the film version, where Ford is almost run over while attempting to greet a blue Ford Prefect. He is saved by Arthur and, in the film version of events, this is how the pair meet (this meeting also prompting Ford to rescue Arthur in particular when the Vogons come to destroy Earth). Adams later observed that this joke was lost on United States audiences who assumed it was a typing error for "perfect." Nowadays, the joke is largely lost on younger audiences in Britain as well, since the Ford Prefect is now a rare sight on British roads.
Ford takes a more existential view on the universe, sometimes bordering on joyful nihilism. He is eccentric and endlessly broad-minded – no doubt due to his vast experience of roughing it around the galaxy – and possesses of an off-key and often very dark sense of humour. He is described as being able to smile in a way that would "send hitherto sane men scampering into the trees". In his role as guide to the universe for the often bewildered everyman Arthur Dent, he serves to link the disparate elements of the story together. As well as rescuing Arthur, he introduces him to the other major characters – such as Zaphod, Trillian and Marvin the Paranoid Android – and to numerous mind-boggling concepts, from "teasers" (an explanation of UFO sightings on Earth) to the extraordinary usefulness of towels. Ford's other chief characteristic is his constant pursuit of an alcohol-fueled good time (in contrast to Arthur's quest for a cup of tea). Although his heart is in the right place and he is shown to be highly intelligent, resourceful and even brave, Ford is essentially a dilettante when it comes to causes such as the search for the question to the ultimate answer of "life, the universe and everything".>>
