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    There Might Be More Than One Way to Make a Planet

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    Astronomers have found evidence of a process that supports an alternative, more rapid approach to planetary formation, more top down than bottom up.When it comes to making a planet, astronomers have long subscribed to what Cassandra Hall, an astronomer at the University of Georgia’s Center for Simulational Physics, refers to as the “bottom up” approach: The gas and dust swirling around a young star slowly clumps together over millions of years, and its gravity shapes it into a rounded object.But a discovery by Dr. Hall and her colleagues, published in the journal Nature this month, suggests that the picture might be more complex.In a star system 508 light-years from Earth, the researchers found conditions that support an alternative “top down” approach to planet formation, in which the fertile material circling a young star rapidly collapses into a planet. The mechanism, known as gravitational instability, could explain the existence of mysterious, massive worlds known to follow wide orbits around relatively young stars.“There’s never been real, hard evidence of it happening before,” Dr. Hall wrote in an email. “We found it!”The cosmic matter stirring around an infant star is ripe with planet-forming potential. The matter is known as a protoplanetary disk, and its rotation is generally driven by the gravity of its host star. But if that disk gets large enough, it can be influenced by its own gravity, causing the young star system to become unstable. Regions of higher density in the disk emerge in the form of spiral arms, similar to the shape of spinning clouds in a hurricane.“The star would be like the eye of the storm,” said Jess Speedie, a graduate student at the University of Victoria in Canada who led the study under the supervision of Ruobing Dong, an astrophysicist.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      For Stonehenge’s Altar Stone, an Improbably Long Ancient Journey

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      A six-ton megalith at the heart of the archaeological site traveled more than 450 miles to get there, a new study concludes.Near the center of the roughly 5,000-year-old circular monument known as Stonehenge is a six-ton, rectangular chunk of red sandstone. In Arthurian legend, the so-called Altar Stone was part of the ring of giant rocks that the wizard Merlin magically transported from Mount Killaurus, in Ireland, to Salisbury Plain, a chalk plateau in southern England — a journey chronicled around 1136 by a Welsh cleric, Geoffrey of Monmouth, in his “Historia Regum Britanniae.”Since then, the accepted provenance of the Altar Stone has shifted, spanning a range of possible sites from east Wales and the Marches to northern England. On Wednesday, a study in the journal Nature reroutes the megalith’s odyssey more definitively, proposing a path much longer than scientists had thought possible.The researchers analyzed the chemical composition and the ages of mineral grains in two microscopic fragments of the Altar Stone. This pinpointed the stone’s source to the Orcadian Basin in northeast Scotland, an area that spans Inverness, the Orkney Islands and Shetland. To reach the archaeological site in Wiltshire, the megalith would have traveled at least 465 miles by land or more than 620 miles along the present-day coastline if it came by sea.“This is a genuinely shocking result,” said Rob Ixer, a retired mineralogist and research fellow at University College London who collaborated on the project. “The work prompts two important questions: How and why did the stone travel the length of Britain?”Stonehenge features two kinds of rocks: larger sarsens and smaller bluestones. The sarsens are sandstone slabs found naturally in southern England. They weigh 20 tons on average and were erected in two concentric arrangements. The inner ring is a horseshoe of five trilithons (two uprights capped by a horizontal lintel), of which three complete ones still stand.Richard Bevins examining Bluestone Stone 46, a rhyolite most probably from north Pembrokeshire, on Wales’s southwest coast.Nick Pearce/Aberystwyth University.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Heat Raises Fears of ‘Demise’ for Great Barrier Reef Within a Generation

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      A new study found that temperatures in the Coral Sea have reached their highest levels in at least four centuries.This generation will probably see the demise of the Great Barrier Reef unless humanity acts with far more urgency to rein in climate change, according to scientists in Australia who released new research on heat in the surrounding ocean.The Great Barrier Reef is the largest coral reef system in the world and is often called the largest living structure on Earth. The study, published on Wednesday in the journal Nature, found that recent extreme temperatures in the Coral Sea are at their highest in at least 400 years, as far back as their analysis could reach.It included modeling that showed what has been driving those extremes: Greenhouse gas emissions caused by humans burning fossil fuels and destroying natural places that store carbon, like forests.“The heat extremes are occurring too often for those corals to effectively adapt and evolve,” said Ben Henley, a paleoclimatologist at the University of Melbourne and an author of the new study. “If we don’t divert from our current course, our generation will likely witness the demise of one of Earth’s great natural wonders, the Great Barrier Reef.”The study’s scientific prose put it this way: “The existential threat to the Great Barrier Reef ecosystem from anthropogenic climate change is now realized.”Tanya Plibersek, Australia’s environment minister, said in a statement that the government understood its responsibility to act on climate change and safeguard the reef. She pointed to a recent law that calls for a 43 percent reduction of emissions by 2030 and to $1.2 billion in measures to protect the reef.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      This Is Literally Your Brain on Drugs

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      A small new study shows reactions in the brain in people who were given psilocybin in a controlled setting.If you had to come up with a groovy visualization of the human brain on psychedelic drugs, it might look something like this.Sara Moser/Washington University School of MedicineThe image, as it happens, comes from dozens of brain scans produced by researchers at Washington University School of Medicine in St. Louis who gave psilocybin, the compound in “magic mushrooms,” to participants in a study before sending them into a functional M.R.I. scanner.The kaleidoscopic whirl of colors they recorded is essentially a heat map of brain changes, with the red, orange and yellow hues reflecting a significant departure from normal activity patterns. The blues and greens reflect normal brain activity that occurs in the so-called functional networks, the neural communication pathways that connect different regions of the brain.The scans, published Wednesday in the journal Nature, offer a rare glimpse into the wild neural storm associated with mind-altering drugs. Researchers say they could provide a potential road map for understanding how psychedelic compounds like psilocybin, LSD and MDMA can lead to lasting relief from depression, anxiety and other mental health disorders.“Psilocybin, in contrast to any other drug we’ve tested, has this massive effect on the whole brain that was pretty unexpected,” said Dr. Nico Dosenbach, a professor of neurology at Washington University and a senior author of the study. “It was quite shocking when we saw the effect size.”We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Summer 2023 Was the Northern Hemisphere’s Hottest in 2,000 Years, Study Finds

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      Scientists used tree rings to compare last year’s extreme heat with temperatures over the past two millenniums.The summer of 2023 was exceptionally hot. Scientists have already established that it was the warmest Northern Hemisphere summer since around 1850, when people started systematically measuring and recording temperatures.Now, researchers say it was the hottest in 2,000 years, according to a new study published in the journal Nature that compares 2023 with a longer temperature record across most of the Northern Hemisphere. The study goes back before the advent of thermometers and weather stations, to the year A.D. 1, using evidence from tree rings.“That gives us the full picture of natural climate variability,” said Jan Esper, a climatologist at Johannes Gutenberg University in Mainz, Germany and lead author of the paper.Extra greenhouse gases in the atmosphere from the burning of fossil fuels are responsible for most of the recent increases in Earth’s temperature, but other factors — including El Niño, an undersea volcanic eruption and a reduction in sulfur dioxide aerosol pollution from container ships — may have contributed to the extremity of the heat last year.The average temperature from June through August 2023 was 2.20 degrees Celsius warmer than the average summer temperature between the years 1 and 1890, according to the researchers’ tree ring data.And last summer was 2.07 degrees Celsius warmer than the average summer temperature between 1850 and 1900, the years typically considered the base line for the period before human-caused climate change.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More