Earlier work by David E. Fisher, MD, PhD, director of the Mass General Cancer Center’s Melanoma Program and director of MGH’s Cutaneous Biology Research Center (CBRC), laid the foundation for the current study. In 2007, Fisher and his team found something unexpected: Exposure to ultraviolet (UV) rays (specifically the form called UVB), causes the skin to produce the hormone endorphin, which is chemically related to morphine, heroin and other opioids — in fact, all activate the same receptors in the brain. A subsequent study by Fisher found that UV exposure raises endorphin levels in mice, which then display behavior consistent with opioid addiction.

Endorphin is sometimes called a “feel good” hormone because it induces a sense of mild euphoria. Studies have suggested that some people develop urges to sunbathe and visit tanning salons that mirror the behaviors of opioid addicts. Fisher and his colleagues speculated that people may seek out UVB because they unknowingly crave the endorphin rush. But that suggests a major contradiction. “Why would we evolve to be behaviorally drawn towards the most common carcinogen that exists?” asked Fisher. After all, sun exposure is the primary cause of skin cancer, to say nothing of wrinkles and other skin damage.

Fisher believes that the only explanation for why humans and other animals seek out the sun is that exposure to UV radiation is necessary for production of vitamin D, which our bodies can’t formulate on their own. Vitamin D promotes uptake of calcium, which is essential for building bone. As tribes of humans migrated north during prehistoric times, an evolutionary alteration might have been needed to compel them to step out of caves and into the sunshine on bitterly cold days. Otherwise, small children would have died of prolonged vitamin D deficiency (the cause of rickets) and weak bones might have shattered when people ran from predators, leaving them vulnerable.

This theory led Fisher and colleagues to hypothesize that sun seeking is driven by vitamin D deficiency, with the goal of increasing synthesis of the hormone for survival, and that vitamin D deficiency might also make the body more sensitive to the effects of opioids, potentially contributing to addiction. “Our goal in this study was to understand the relationship between vitamin D signaling in the body and UV-seeking and opioid-seeking behaviors,” says lead author Lajos V. Kemény, MD, PhD, a postdoctoral research fellow in Dermatology at MGH.

In the Science Advances paper, Fisher, Kemény and a multidisciplinary team from several institutions addressed the question from dual perspectives. In one arm of the study, they compared normal laboratory mice with mice that were deficient in vitamin D (either through special breeding or by removing vitamin D from their diets). “We found that modulating vitamin D levels changes multiple addictive behaviors to both UV and opioids,” says Kemény. Importantly, when the mice were conditioned with modest doses of morphine, those deficient in vitamin D continued seeking out the drug, behavior that was less common among the normal mice. When morphine was withdrawn, the mice with low vitamin D levels were far more likely to develop withdrawal symptoms.

The study also found that morphine worked more effectively as a pain reliever in mice with vitamin D deficiency — that is, the opioid had an exaggerated response in these mice, which may be concerning if it’s true in humans, too, says Fisher. After all, consider a surgery patient who receives morphine for pain control after the operation. If that patient is deficient in vitamin D, the euphoric effects of morphine could be exaggerated, says Fisher, “and that person is more likely to become addicted.”

The lab data suggesting that vitamin D deficiency increases addictive behavior was supported by several accompanying analyses of human health records. One showed that patients with modestly low vitamin D levels were 50 percent more likely than others with normal levels to use opioids, while patients who had severe vitamin D deficiency were 90 percent more likely. Another analysis found that patients diagnosed with opioid use disorder (OUD) were more likely than others to be deficient in vitamin D.

Back in the lab, one of the study’s other critical findings could have significant implications, says Fisher. “When we corrected vitamin D levels in the deficient mice, their opioid responses reversed and returned to normal,” he says. In humans, vitamin D deficiency is widespread, but is safely and easily treated with low-cost dietary supplements, notes Fisher. While more research is needed, he believes that treating vitamin D deficiency may offer a new way to help reduce the risk for OUD and bolster existing treatments for the disorder. “Our results suggests that we may have an opportunity in the public health arena to influence the opioid epidemic,” says Fisher.

“This work opens the door to many other studies that will help us understand the significance of having a mechanism for converting RNA messages into DNA in our own cells,” says Richard Pomerantz, PhD, associate professor of biochemistry and molecular biology at Thomas Jefferson University. “The reality that a human polymerase can do this with high efficiency, raises many questions.” For example, this finding suggests that RNA messages can be used as templates for repairing or re-writing genomic DNA.

The work was published June 11th in the journal Science Advances.

Together with first author Gurushankar Chandramouly and other collaborators, Dr. Pomerantz’s team started by investigating one very unusual polymerase, called polymerase theta. Of the 14 DNA polymerases in mammalian cells, only three do the bulk of the work of duplicating the entire genome to prepare for cell division. The remaining 11 are mostly involved in detecting and making repairs when there’s a break or error in the DNA strands. Polymerase theta repairs DNA, but is very error-prone and makes many errors or mutations. The researchers therefore noticed that some of polymerase theta’s “bad” qualities were ones it shared with another cellular machine, albeit one more common in viruses — the reverse transcriptase. Like Pol theta, HIV reverse transcriptase acts as a DNA polymerase, but can also bind RNA and read RNA back into a DNA strand.

In a series of elegant experiments, the researchers tested polymerase theta against the reverse transcriptase from HIV, which is one of the best studied of its kind. They showed that polymerase theta was capable of converting RNA messages into DNA, which it did as well as HIV reverse transcriptase, and that it actually did a better job than when duplicating DNA to DNA. Polymerase theta was more efficient and introduced fewer errors when using an RNA template to write new DNA messages, than when duplicating DNA into DNA, suggesting that this function could be its primary purpose in the cell.

The group collaborated with Dr. Xiaojiang S. Chen’s lab at USC and used x-ray crystallography to define the structure and found that this molecule was able to change shape in order to accommodate the more bulky RNA molecule — a feat unique among polymerases.

“Our research suggests that polymerase theta’s main function is to act as a reverse transcriptase,” says Dr. Pomerantz. “In healthy cells, the purpose of this molecule may be toward RNA-mediated DNA repair. In unhealthy cells, such as cancer cells, polymerase theta is highly expressed and promotes cancer cell growth and drug resistance. It will be exciting to further understand how polymerase theta’s activity on RNA contributes to DNA repair and cancer-cell proliferation.”

This research was supported by NIH grants 1R01GM130889-01 and 1R01GM137124-01, and R01CA197506 and R01CA240392. This research was also supported in part by a Tower Cancer Research Foundation grant.

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Since floating ice shelves help to hold back the larger grounded mass of the glacier, the recent speedup due to the weakening edge could shorten the timeline for Pine Island Glacier’s eventual collapse into the sea. The study from researchers at the University of Washington and British Antarctic Survey was published June 11 in the open-access journal Science Advances.

“We may not have the luxury of waiting for slow changes on Pine Island; things could actually go much quicker than expected,” said lead author Ian Joughin, a glaciologist at the UW Applied Physics Laboratory. “The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

Pine Island Glacier contains approximately 180 trillion tons of ice — equivalent to 0.5 meters, or 1.6 feet, of global sea level rise. It is already responsible for much of Antarctica’s contribution to sea-level rise, causing about one-sixth of a millimeter of sea level rise each year, or about two-thirds of an inch per century, a rate that’s expected to increase. If it and neighboring Thwaites Glacier speed up and flow completely into the ocean, releasing their hold on the larger West Antarctic Ice Sheet, global seas could rise by several feet over the next few centuries.

These glaciers have attracted attention in recent decades as their ice shelves thinned because warmer ocean currents melted the ice’s underside. From the 1990s to 2009, Pine Island Glacier’s motion toward the sea accelerated from 2.5 kilometers per year to 4 kilometers per year (1.5 miles per year to 2.5 miles per year). The glacier’s speed then stabilized for almost a decade.

Results show that what’s happened more recently is a different process, Joughin said, related to internal forces on the glacier.

From 2017 to 2020, Pine Island’s ice shelf lost one-fifth of its area in a few dramatic breaks that were captured by the Copernicus Sentinel-1 satellites, operated by the European Space Agency on behalf of the European Union. The researchers analyzed images from January 2015 to March 2020 and found that the recent changes on the ice shelf were not caused by processes directly related to ocean melting.

“The ice shelf appears to be ripping itself apart due to the glacier’s acceleration in the past decade or two,” Joughin said.

Two points on the glacier’s surface that were analyzed in the paper sped up by 12% between 2017 and 2020. The authors used an ice flow model developed at the UW to confirm that the loss of the ice shelf caused the observed speedup.

“The recent changes in speed are not due to melt-driven thinning; instead they’re due to the loss of the outer part of the ice shelf,” Joughin said. “The glacier’s speedup is not catastrophic at this point. But if the rest of that ice shelf breaks up and goes away then this glacier could speed up quite a lot.”

It’s not clear whether the shelf will continue to crumble. Other factors, like the slope of the land below the glacier’s receding edge, will come into play, Joughin said. But the results change the timeline for when Pine Island’s ice shelf might disappear and how fast the glacier might move, boosting its contribution to rising seas.

“The loss of Pine Island’s ice shelf now looks like it possibly could occur in the next decade or two, as opposed to the melt-driven subsurface change playing out over 100 or more years,” said co-author Pierre Dutrieux, an ocean physicist at British Antarctic Survey. “So it’s a potentially much more rapid and abrupt change.”

Pine Island’s ice shelf is important because it’s helping to hold back this relatively unstable West Antarctic glacier, the way the curved buttresses on Notre Dame cathedral hold up the cathedral’s mass. Once those buttresses are removed, the slow-moving glacier can flow more quickly downward to the ocean, contributing to rising seas.

“Sediment records in front of and beneath the Pine Island ice shelf indicate that the glacier front has remained relatively stable over a few thousand years,” Dutrieux said. “Regular advance and break-ups happened at approximately the same location until 2017, and then successively worsened each year until 2020.”

Other co-authors are Daniel Shapero and Ben Smith at the UW; and Mark Barham at British Antarctic Survey. The study was funded by the U.S. National Science Foundation, NASA and the U.K. Natural Environment Research Council.

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The biology of our brains may play a role in that. Researchers at Washington University School of Medicine in St. Louis have identified specific areas and cells in the brain that become active when an individual is faced with the choice to learn or hide from information about an unwanted aversive event the individual likely has no power to prevent.

The findings, published June 11 in Neuron, could shed light on the processes underlying psychiatric conditions such as obsessive-compulsive disorder and anxiety — not to mention how all of us cope with the deluge of information that is a feature of modern life.

“People’s brains aren’t well equipped to deal with the information age,” said senior author Ilya Monosov, PhD, an associate professor of neuroscience, of neurosurgery and of biomedical engineering. “People are constantly checking, checking, checking for news, and some of that checking is totally unhelpful. Our modern lifestyles could be resculpting the circuits in our brain that have evolved over millions of years to help us survive in an uncertain and ever-changing world.”

In 2019, studying monkeys, Monosov laboratory members J. Kael White, PhD, then a graduate student, and senior scientist Ethan S. Bromberg-Martin, PhD, identified two brain areas involved in tracking uncertainty about positively anticipated events, such as rewards. Activity in those areas drove the monkeys’ motivation to find information about good things that may happen.

But it wasn’t clear whether the same circuits were involved in seeking information about negatively anticipated events, like punishments. After all, most people want to know whether, for example, a bet on a horse race is likely to pay off big. Not so for bad news.

“In the clinic, when you give some patients the opportunity to get a genetic test to find out if they have, for example, Huntington’s disease, some people will go ahead and get the test as soon as they can, while other people will refuse to be tested until symptoms occur,” Monosov said. “Clinicians see information-seeking behavior in some people and dread behavior in others.”

To find the neural circuits involved in deciding whether to seek information about unwelcome possibilities, first author Ahmad Jezzini, PhD, and Monosov taught two monkeys to recognize when something unpleasant might be headed their way. They trained the monkeys to recognize symbols that indicated they might be about to get an irritating puff of air to the face. For example, the monkeys first were shown one symbol that told them a puff might be coming but with varying degrees of certainty. A few seconds after the first symbol was shown, a second symbol was shown that resolved the animals’ uncertainty. It told the monkeys that the puff was definitely coming, or it wasn’t.

The researchers measured whether the animals wanted to know what was going to happen by whether they watched for the second signal or averted their eyes or, in separate experiments, letting the monkeys choose among different symbols and their outcomes.

Much like people, the two monkeys had different attitudes toward bad news: One wanted to know; the other preferred not to. The difference in their attitudes toward bad news was striking because they were of like mind when it came to good news. When they were given the option of finding out whether they were about to receive something they liked — a drop of juice — they both consistently chose to find out.

“We found that attitudes toward seeking information about negative events can go both ways, even between animals that have the same attitude about positive rewarding events,” said Jezzini, who is an instructor in neuroscience. “To us, that was a sign that the two attitudes may be guided by different neural processes.”

By precisely measuring neural activity in the brain while the monkeys were faced with these choices, the researchers identified one brain area, the anterior cingulate cortex, that encodes information about attitudes toward good and bad possibilities separately. They found a second brain area, the ventrolateral prefrontal cortex, that contains individual cells whose activity reflects the monkeys’ overall attitudes: yes for info on either good or bad possibilities vs. yes for intel on good possibilities only.

Understanding the neural circuits underlying uncertainty is a step toward better therapies for people with conditions such as anxiety and obsessive-compulsive disorder, which involve an inability to tolerate uncertainty.

“We started this study because we wanted to know how the brain encodes our desire to know what our future has in store for us,” Monosov said. “We’re living in a world our brains didn’t evolve for. The constant availability of information is a new challenge for us to deal with. I think understanding the mechanisms of information seeking is quite important for society and for mental health at a population level.”

In addition to these virtues, DHA is also associated with a reduction in the incidence of cancer. How it works is the subject of a major discovery by a multidisciplinary team of University of Louvain (UCLouvain) researchers, who have just elucidated the biochemical mechanism that allows DHA and other related fatty acids to slow the development of tumours. This is a major advance that has recently been published in the journal Cell Metabolism.

Key to the discovery: interdisciplinarity

In 2016, Olivier Feron’s UCLouvain team, which specialises in oncology, discovered that cells in an acidic microenvironment (acidosis) within tumours replace glucose with lipids as an energy source in order to multiply. In collaboration with UCLouvain’s Cyril Corbet, Prof. Feron demonstrated in 2020 that these same cells are the most aggressive and acquire the ability to leave the original tumour to generate metastases. Meanwhile, Yvan Larondelle, a professor in the UCLouvain Faculty of Bioengineering, whose team is developing improved dietary lipid sources, proposed to Prof. Feron that they combine their skills in a research project, led by PhD candidate Emeline Dierge, to evaluate the behaviour of tumour cells in the presence of different fatty acids.

Thanks to the support of the Fondation Louvain, the Belgian Cancer Foundation and the Télévie telethon, the team quickly identified that these acidotic tumour cells responded in diametrically opposite ways depending on the fatty acid they were absorbing. Within a few weeks, the results were both impressive and surprising. “We soon found that certain fatty acids stimulated the tumour cells while others killed them,” the researchers explained. DHA literally poisons them.

A fatal overload

The poison acts on tumour cells via a phenomenon called ferroptosis, a type of cell death linked to the peroxidation of certain fatty acids. The greater the amount of unsaturated fatty acids in the cell, the greater the risk of their oxidation. Normally, in the acidic compartment within tumours, cells store these fatty acids in lipid droplets, a kind of bundle in which fatty acids are protected from oxidation. But in the presence of a large amount of DHA, the tumour cell is overwhelmed and cannot store the DHA, which oxidises and leads to cell death. By using a lipid metabolism inhibitor that prevents the formation of lipid droplets, researchers were able to observe that this phenomenon is further amplified, which confirms the identified mechanism and opens the door to combined treatment possibilities.

For their study, UCLouvain researchers used a 3D tumour cell culture system, called spheroids. In the presence of DHA, spheroids first grow and then implode. The team also administered a DHA-enriched diet to mice with tumours. The result: tumour development was significantly slowed compared to that in mice on a conventional diet.

This UCLouvain study shows the value of DHA in fighting cancer. “For an adult,” the UCLouvain researchers stated, “it’s recommended to consume at least 250 mg of DHA per day. But studies show that our diet provides on average only 50 to 100 mg per day. This is well below the minimum recommended intake.”

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Researchers investigating remains in Cambridge, UK, found that those buried in the town centre, particularly in plots for wealthier citizens and clergy, were much more likely to have had bunions — suggesting rich urbanites paid a higher price for their footwear in more ways than one.

A University of Cambridge team also discovered that older medieval people with hallux valgus were significantly more likely to have sustained a broken bone from a probable fall compared to those of a similar age with normal feet.

Hallux valgus is a minor deformity in which the largest toe becomes angled outward and a bony protrusion forms at its base, on the inside of the foot.

While various factors can predispose someone to bunions, from genetics to muscle imbalance, by far the most common contemporary cause is constrictive boots and shoes. The condition is often associated with wearing high heels.

Archaeologists analysed 177 skeletons from cemeteries in and around the city of Cambridge and found that only 6% of individuals buried between 11th and 13th centuries had evidence of the affliction. However, 27% of those dating from the 14th and 15th centuries had been hobbled by longstanding hallux valgus.

Researchers point out that shoe style changed significantly during the 14th century: shifting from a functional rounded toe box to a lengthy and more elegant pointed tip.

In a paper published today in the International Journal of Paleopathology, the team from Cambridge University’s After the Plague project argues that these “poulaine” shoes drove the rise of bunions in medieval Britain.

“The 14th century brought an abundance of new styles of dress and footwear in a wide range of fabrics and colours. Among these fashion trends were pointed long-toed shoes called poulaines,” said study co-author Dr Piers Mitchell from Cambridge’s Department of Archaeology.

“The remains of shoes excavated in places like London and Cambridge suggest that by the late 14th century almost every type of shoe was at least slightly pointed — a style common among both adults and children alike.”

“We investigated the changes that occurred between the high and late medieval periods, and realized that the increase in hallux valgus over time must have been due to the introduction of these new footwear styles,” said Mitchell.

First author Dr Jenna Dittmar, who conducted the work while at Cambridge, said: “We think of bunions as being a modern problem but this work shows it was actually one of the more common conditions to have affected medieval adults.”

The remains came from four separate sites around Cambridge: a charitable hospital (now part of St John’s College); the grounds of a former Augustinian friary, where clergy and wealthy benefactors were buried; a local parish graveyard on what was the edge of town; and a rural burial site by a village 6km south of Cambridge.

Researchers conducted “paleopathological assessments,” including inspecting foot bones for the bump by the big toe that is the hallmark of hallux valgus.

They found a sliding scale of bunion prevalence linked to the wealth of those interred on each site. Only 3% of the rural cemetery showed signs, 10% of the parish graveyard (which mainly held the working poor), creeping up to 23% of those on the hospital site.

Yet almost half those buried in the friary — some 43% — including five of the eleven individuals identified as clergy by their belt buckles, carried the mark of the bunion.

“Rules for the attire of Augustinian friars included footwear that was ‘black and fastened by a thong at the ankle’, commensurate with a lifestyle of worship and poverty,” said Mitchell.

“However, in the 13th and 14th centuries it was increasingly common for those in clerical orders in Britain to wear stylish clothes — a cause for concern among high-ranking church officials.”

In 1215, the church forbade clergy from wearing pointed-toed shoes. This may have done little to curb the trend, as numerous further decrees on indiscretions in clerical dress had to be passed, most notably in 1281 and 1342.

“The adoption of fashionable garments by the clergy was so common it spurred criticism in contemporary literature, as seen in Chaucer’s depiction of the monk in the Canterbury Tales,” said Mitchell.

Across late medieval society the pointiness of shoes became so extreme that in 1463 King Edward IV passed a law limiting toe-point length to less than two inches within London.

The majority of remains with signs of hallux valgus across all sites and eras within the study were men (20 of the 31 total bunion sufferers). The research also suggests that health costs of foot fashion were not limited to bunions.

Dr Jenna Dittmar found that skeletal remains with hallux valgus were also more likely to show signs of fractures that usually result from a fall e.g. those to upper limbs indicating an individual tumbled forward onto outstretched arms.

This association was only found to be significant among those who died over 45 year old, suggesting youthful fashion choices came back to haunt the middle-aged even in medieval times.

“Modern clinical research on patients with hallux valgus has shown that the deformity makes it harder to balance, and increases the risk of falls in older people,” said Dittmar. “This would explain the higher number of healed broken bones we found in medieval skeletons with this condition.”

An international team of astronomers observed the star, VVV-WIT-08, decreasing in brightness by a factor of 30, so that it nearly disappeared from the sky. While many stars change in brightness because they pulsate or are eclipsed by another star in a binary system, it’s exceptionally rare for a star to become fainter over a period of several months and then brighten again.

The researchers believe that VVV-WIT-08 may belong to a new class of ‘blinking giant’ binary star system, where a giant star — 100 times larger than the Sun — is eclipsed once every few decades by an as-yet unseen orbital companion. The companion, which may be another star or a planet, is surrounded by an opaque disc, which covers the giant star, causing it to disappear and reappear in the sky. The study is published in Monthly Notices of the Royal Astronomical Society.

The discovery was led by Dr Leigh Smith from Cambridge’s Institute of Astronomy, working with scientists at the University of Edinburgh, the University of Hertfordshire, the University of Warsaw in Poland and Universidad Andres Bello in Chile.

“It’s amazing that we just observed a dark, large and elongated object pass between us and the distant star and we can only speculate what its origin is,” said co-author Dr Sergey Koposov from the University of Edinburgh.

Since the star is located in a dense region of the Milky Way, the researchers considered whether some unknown dark object could have simply drifted in front of the giant star by chance. However, simulations showed that there would have to be an implausibly large number of dark bodies floating around the Galaxy for this scenario to be likely.

One other star system of this sort has been known for a long time. The giant star Epsilon Aurigae is partly eclipsed by a huge disc of dust every 27 years, but only dims by about 50%. A second example, TYC 2505-672-1, was found a few years ago, and holds the current record for the eclipsing binary star system with the longest orbital period — 69 years — a record for which VVV-WIT-08 is currently a contender.

The UK-based team has also found two more of these peculiar giant stars in addition to VVV-WIT-08, suggesting that these may be a new class of ‘blinking giant’ stars for astronomers to investigate.

VVV-WIT-08 was found by the VISTA Variables in the Via Lactea survey (VVV), a project using the British-built VISTA telescope in Chile and operated by the European Southern Observatory, that has been observing the same one billion stars for nearly a decade to search for examples with varying brightness in the infrared part of the spectrum.

Project co-leader Professor Philip Lucas from the University of Hertfordshire said, “Occasionally we find variable stars that don’t fit into any established category, which we call ‘what-is-this?’, or ‘WIT’ objects. We really don’t know how these blinking giants came to be. It’s exciting to see such discoveries from VVV after so many years planning and gathering the data.”

While VVV-WIT-08 was discovered using VVV data, the dimming of the star was also observed by the Optical Gravitational Lensing Experiment (OGLE), a long-running observation campaign run by the University of Warsaw. OGLE makes more frequent observations, but closer to the visible part of the spectrum. These frequent observations were key for modelling VVV-WIT-08, and they showed that the giant star dimmed by the same amount in both the visible and infrared light.

There now appear to be around half a dozen potential known star systems of this type, containing giant stars and large opaque discs. “There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star,” said Smith. “In doing so, we might learn something new about how these kinds of systems evolve.”

Astronomers have modelled how the change in gravitational forces in the system as a result of the star becoming a white dwarf will cause its planets to fly loose from their orbits and bounce off each other’s gravity, like balls bouncing off a bumper in a game of pinball.

In the process, they will knock nearby debris into their dying sun, offering scientists new insight into how the white dwarfs with polluted atmospheres that we see today originally evolved. The conclusions by astronomers from the University of Warwick and the University of Exeter are published in the Monthly Notices of the Royal Astronomical Society.

The HR 8799 system is 135 light years away and comprises a 30-40 million year-old A type star and four unusually massive planets, all over five times the mass of Jupiter, orbiting very close to each other. The system also contains two debris discs, inside the orbit of the innermost planet and another outside the outermost. Recent research has shown that the four planets are locked in a perfect rhythm that sees each one completing double the orbit of its neighbour: so for every orbit the furthest completes, the next closest completes two, the next completes four, while the closest completes eight.

The team from Warwick and Exeter decided to learn the ultimate fate of the system by creating a model that allowed them to play ‘planetary pinball’ with the planets, investigating what may cause the perfect rhythm to destabilise.

They determined that the resonance that locks the four planets is likely to hold firm for the next 3 billion years, despite the effects of Galactic tides and close flybys of other stars. However, it always breaks once the star enters the phase in which it becomes a red giant, when it will expand to several hundred times its current size and eject nearly half its mass, ending up as a white dwarf.

The planets will then start to pinball and become a highly chaotic system where their movements become very uncertain. Even changing a planet’s position by a centimetre at the start of the process can dramatically change the outcome.

Lead author Dr Dimitri Veras from the University of Warwick Department of Physics said: “The planets will gravitationally scatter off of one another. In one case, the innermost planet could be ejected from the system. Or, in another case, the third planet may be ejected. Or the second and fourth planets could switch positions. Any combination is possible just with little tweaks.

“They are so big and so close to each other the only thing that’s keeping them in this perfect rhythm right now is the locations of their orbits. All four are connected in this chain. As soon as the star loses mass their locations will deviate, then two of them will scatter off one another, causing a chain reaction amongst all four.”

Dr Veras was supported by an Ernest Rutherford Fellowship from the Science and Technology Facilities Council, part of UK Research and Innovation.

Regardless of the precise movements of the planets, one thing that the team is certain of is that the planets will move around enough to dislodge material from the system’s debris discs into the atmosphere of the star. It is this type of debris that astronomers are analysing today to discover the histories of other white dwarf systems.

Dr Veras adds: “These planets move around the white dwarf at different locations and can easily kick whatever debris is still there into the white dwarf, polluting it.

“The HR 8799 planetary system represents a foretaste of the polluted white dwarf systems that we see today. It’s a demonstration of the value of computing the fates of planetary systems, rather than just looking at their formation.”

Co-author Professor Sasha Hinkley of the University of Exeter said: “The HR 8799 system has been so iconic for exoplanetary science since its discovery nearly 13 years ago, and so it is fascinating to see into the future, and watch it evolve from a harmonious collection of planets into a chaotic scene.”

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