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Indian Express
04-07-2025
- Science
- Indian Express
‘Very massive stars' shed enormous mass before collapsing into black holes: Study
'Very massive stars' or 'very luminous stars' may be emitting a significantly higher amount of material during their lifespan. A new study suggests that the immensity of these materials could be much higher than previously thought. Very luminous stars are those stars that have over 100 times the mass of the Sun. Despite having a much higher mass than the Sun, they use their nuclear fuel at a much higher rate, making their average lifespan only a few million years, at times even exhausting their fuel in a few hundred thousand years. For comparison, the Sun has existed for 4.5 billion years and is expected to live for another ten billion years. This indicates an almost fifteen billion-year lifespan, significantly longer than that of the very luminous stars. Once their nuclear fuel is exhausted, very luminous stars collapse to form black holes. A team of scientists assembled to study these stars has estimated that very luminous stars produce stellar wind that is powerful enough to blow their own outer layer into space. As per the scientists' models, stellar systems consisting of two gravitationally bound stars (also known as stellar binaries) can merge to form one very luminous star. The team also attempted to research a link between strong stellar winds and black hole population. These stars, despite their short lifespan, still influence the region around them. For instance, their powerful stellar winds can push newly formed elements into their surroundings. While most form new stars, elements key to life, such as carbon and oxygen, are also emitted. In spite of their distance from our Earth, they still bear an influence on it. These stars can be considered the predecessor to black holes. This occasionally leads to black hole binaries, where two black holes orbit around each other. These cause gravitational waves, which we then detect on Earth. Previous studies used space- and ground-based telescopes to study these stars in the Tarantula Nebula of the Large Magellanic Cloud for the first time. Several stars at the centre of the Tarantula Nebula weighed over 200 times the mass of the Sun. These stars were called 'Wolf-Rayet stars' (or WNh stars) that were at the end of their hydrogen-burning phase; hence, the stars displayed leftover hydrogen on their surface. They had an estimated temperature of 40,000 to 50,000 degrees Celsius but, as per standard models, cooled down with age. Researchers subsequently ideated a 'mass-loss recipe' to link the theory and observation. Researchers at the International School for Advanced Studies in Italy (also known as SISSA) subsequently used these studies to add to their stellar evolution code, PAdova and tRieste Stellar Evolution Code (shortened to PARSEC). They used this code to create a model for the Tarantula Nebula's stars. 'The strong winds strip away the star's outer layers, preventing it from cooling down, while maintaining the surface composition matching a WNh star. The star stays more compact and hot for longer, exactly reproducing what observations show,' researcher Kendall Shepherd was quoted as saying by The model might have given a clue to another celestial mystery: the creation of R136a1. This 1.5-million-year-old star is the most massive star known by scientists, with a mass of up to 230 times that of the Sun and a luminosity over 4.6 million times that of the Sun. The new model is suggesting two methods of R136a1's formation. It could either have been a ginormous star from birth or been the result of a colossal stellar merger (where two stars merge to form one larger star). While initially discounted, the model is now allowing for the idea of the stellar merger as a reasonable explanation for R136a1. Due to the discovery of the extent of very luminous stars' mass loss, it is discovered that they subsequently form smaller black holes after their death. These can be described as 'intermediate-mass black holes', around 100 to 10,000 times more massive than the sun, and are considered difficult to find in nature. Another notable discovery of the research is a key insight into the formation of binary black holes. Contrary to current belief, stronger stellar winds are a crucial factor for systems to develop into black hole binaries. With weaker stellar winds, it was more probable for stars to merge before becoming black holes. With more violent stellar winds, stars would be blown further apart before their death, collapse, and subsequent black hole formation. These black holes could then slowly spiral and eventually merge to form a binary black hole. While this is notable research, it was only focused on the Large Magellanic Cloud's environment. This environment has a unique chemical composition, meaning results cannot be generalisable to every system in the universe. Hence, the presumed next step will be observing and finding explanations for a selection of peculiar observed stars in other environments. (This article has been curated by Purv Ashar, who is an intern with The Indian Express)
Yahoo
04-07-2025
- Science
- Yahoo
Very massive stars vomit vast amounts of matter before collapsing into black holes
When you buy through links on our articles, Future and its syndication partners may earn a commission. Very massive stars that collapse to create black holes may vomit out much more material during their short lives than we previously thought. To fit with astronomical observations of these stars, which have masses over 100 times that of the sun, a team of scientists has estimated that very massive stars must have stellar winds far more powerful than has been estimated in the past. These winds should be powerful enough to blow the outer layers of these monstrous stars into space. The team's modeling revealed how stellar binaries can lead to mergers between stars that forge single, very massive stars. They also explored how stronger stellar winds impact black hole populations, pointing away from the formation of elusive intermediate-mass black holes. "Very massive stars are like the 'rock stars' of the universe — they are powerful, and they live fast and die young," team member Kendall Shepherd, a researcher at the Institute for Advanced Study in Italy (known by its Italian acronym, SISSA), told "For these very massive stars, their stellar wind is more like a hurricane than a light breeze." While our average-sized sun is expected to live for around 10 billion years, very massive stars burn through their nuclear fuel faster, living for just a few million years, or even a few hundred thousand years. Studying such behemoths is important because they have a profound impact on their environments despite their short lives, Shepherd said. "The strong winds of very massive stars and their eventual supernova explosions eject newly formed elements into the environment," she said. "Many of these elements form the basis of new stars, while others, like carbon and oxygen, are the building blocks of life. "They are also the progenitors of black holes, including the black hole binaries that merge and produce gravitational waves that we detect on Earth." In the new research, Shepherd and her colleagues analyzed theoretical and observational studies of very massive stars. "Such massive stars are so incredibly rare, and so few observational constraints existed," Shepherd said. "With the help of space and ground-based telescopes, researchers were recently finally able to directly observe several stars in the Tarantula Nebula of the Large Magellanic Cloud with masses above 100 times our sun's mass for the first time." Those previous studies found that the most massive stars in the Tarantula Nebula are a rare hot and bright type of mostly stripped Wolf-Rayet stars (WNh stars) at the end of their hydrogen-burning phase, meaning they show leftover hydrogen on their surface. "These stars were found to be very hot, around 72,540 to 90,000 degrees Fahrenheit (40,000 to 50,000 degrees Celsius). That's a little too hot! Standard models predict that, as the stars age, they should expand and cool down, in contrast to what the new observations showed," Shepherd said. "Researchers put the two pieces together and used the observed properties to calibrate a mass-loss 'recipe' to combine the theory and observation." The team worked this recipe into their stellar evolution code, known as PARSEC (PAdova and tRieste Stellar Evolution Code), to create a new model accounting for the massive stars of the Tarantula Nebula. "Our new models featuring stronger stellar winds are now able to match the observations and theory. The strong winds strip away the star's outer layers, preventing it from cooling down, while maintaining the surface composition matching a WNh star," Shepherd explained. "The star stays more compact and hot for longer, exactly reproducing what observations show." The team's research suggests there are two different routes that could have led to the birth of stars like the most massive star ever seen, R136a1. This star, also found in the Tarantula Nebula, has up to 230 times the mass of the sun and emits millions of times more energy than our star. It's also just 1.5 million years old, compared to the 4.6 billion-year-old sun. The team's model suggests that R136a1 could have been born as a single, ginormous star, or it could have formed as a result of a dramatic stellar merger. "I was surprised that our results give two distinct possible explanations for the origin of R136a1, the most massive star known. I was quite fascinated that a binary stellar merger — where two stars merge and become a single, more massive star — could provide a plausible origin," Shepherd said. "Even more interesting is the difference in the initial mass that is needed to reproduce R136a1 from the single-star and binary stellar merger scenarios." The researcher added that, for a single-star origin to match the features of R136a1, the star would need an initial mass over 100 solar masses — larger than is needed for a binary stellar merger origin, regardless of the wind recipe used. "This could suggest a revision to what we thought was the upper limit for how massive a star can be in the local universe," Shepherd said. Strong stellar winds and the rapid mass loss they cause also have strong implications for the masses of black holes that are created when massive stars collapse under their own gravity at the end of their lives. "Because the stronger winds strip away so much of the star's mass, at the end of their lives they form smaller black holes," Shepherd said. "This study can shed a lot of light on predicting black hole masses. Stellar models that use the standard and weaker mass-loss recipes can produce intermediate-mass black holes." These black holes, which are around 100 to 10,000 times more massive than the sun, have proved difficult for astronomers to find. "By having the stars lose more mass via stronger winds, the simulations produce fewer of these uncertain objects, making our models more in line with what is found in nature!" Shepherd said. The team also proposes that, contrary to current thinking, stronger stellar winds are needed if systems are to develop into black hole binaries with masses both greater than around 30 times that of the sun. "Even more exciting is that, when we looked at the binary black holes that merge in our simulations, our new models with stronger winds were able to produce systems where the two black holes were both massive," Shepherd said. "This is exciting because this is a population that has been observed with gravitational wave detectors, but which previous models with standard winds struggled to produce." The two black holes in these binaries emit tiny ripples in space called gravitational waves as they spiral together and eventually merge. But strong stellar winds may be key to allowing this situation to develop. "With the weaker, standard winds, the two stars expand and are more likely to merge before becoming black holes," Shepherd explained. "In contrast, the stronger winds can push the two stars apart, allowing them to survive as a pair of black holes that can later spiral in and merge." Related Stories: — 'This is the holy grail of theoretical physics.' Is the key to quantum gravity hiding in this new way to make black holes? — This supermassive black hole is eating way too quickly — and 'burping' at near-light speeds — Astronomers discover ultrapowerful black hole jet as bright as 10 trillion suns lit by Big Bang's afterglow The new research was focused on one specific environment, in the Large Magellanic Cloud, which has its own unique chemical composition. Thus, Shepherd said, the next step for the team will be to try to explain a handful of peculiar observed stars. "These results are not yet universal, and so the natural next step would be to extend this study to a range of different initial compositions, to model different environments across the universe," Shepherd concluded. "It would be very exciting to see how much the predicted black hole populations change with these differing initial compositions." The team's research is available as a preprint on the research repository arXiv.
Yahoo
19-02-2025
- Health
- Yahoo
This Eating Habit Can Be An Early Sign Of Dementia
Studies have shown that everything from brushing your teeth to climbing the stairs can reveal signs of early dementia. And now, it seems that how you take your dinner could indicate whether or not you've got a condition called frontotemporal dementia. The uncommon subtype of dementia affects about one in every 20 dementia patients, Dementia UK say it's an'umbrella term for a group of dementias that mainly affect the frontal and temporal lobes of the brain, which are responsible for personality, behaviour, language and speech.' And unlike other forms of dementia, its early stages may not always be characterised by memory loss or impaired concentration. Instead, one of the symptoms of behavioural variant frontotemporal dementia (bv FTD) is 'obsessive or repetitive behaviour' ― and that can extend to food. 'Frontotemporal dementia is associated with a wide variety of abnormal eating behaviours such as hyperphagia, fixations on one kind of food, even ingestion of inanimate objects,' a paper on the topic reads. Those with the condition may refuse to eat anything other than one food ― for instance, the paper referenced a 'banana lady,' who ate nothing but bananas and drank nothing but milk for months before her death. After an autopsy, it was found that she had frontotemporal dementia (FTD). Those with the condition may also eat non-food objects and steal food from other people's plates. 'These behaviours are problematic, of course, socially, but also with regard to patients' health as they tend to gain weight,' says SISSA researcher, Marilena Aiello, who was involved in a systemic review of FTD, 'even if individual consequences are different.' However, 'some people lose weight because they eat a narrow range of foods in an obsessive way,' the researcher says. We're not fully sure. 'The origin of food anomalies in frontotemporal dementia is likely due to many factors,' says Aiello. 'It may involve an alteration of the autonomic nervous system, characterised by an altered assessment of the body's signals, such as hunger, satiety, and appetite. Damage to the hypothalamus can cause a loss of inhibitory signals, causing behaviours such as overeating,' the researcher says. On top of that, 'There are probably sensory and cognitive factors that can complicate the picture... In patients who eat objects, for example, there is perhaps a semantic problem of recognising the object of and its function,' Allieo adds. Of course, hyperfixating on foods and eating non-food objects aren't specific to FTD. Allieo himself says that these are 'abnormalities that may be present, albeit with varied intensities, in healthy individuals with irregular eating habits.' Pica, the desire to eat non-food objects like clay, can happen in pregnancy, for instance; those with autism can sometimes hyperfixate on foods. The habit may signify FTD more strongly, however, if combined with other symptoms of the condition. These are, per the NHS: personality and behaviour changes – acting inappropriately or impulsively, appearing selfish or unsympathetic, neglecting personal hygiene, overeating, or loss of motivation language problems – speaking slowly, struggling to make the right sounds when saying a word, getting words in the wrong order, or using words incorrectly problems with mental abilities – getting distracted easily, struggling with planning and organisation memory problems – these only tend to occur later on, unlike more common forms of dementia, such as Alzheimer's disease Physical problems, such as slow or stiff movements, loss of bladder or bowel control (usually not until later on), muscle weakness or difficulty swallowing. If you suspect you or a loved one has dementia, it's important to speak to a GP as soon as possible as the earlier the intervention, the better. Bad Habits That Can Increase Your Risk Of Dementia This Could Be The Key To Identifying Dementia 15 Years Before Diagnosis Cosy Daytime Habit Can Be A Symptom Of Dementia
