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    The Milky Way may be spawning many more stars than astronomers had thought

    The Milky Way is churning out far more stars than previously thought, according to a new estimate of its star formation rate.

    Gamma rays from aluminum-26, a radioactive isotope that arises primarily from massive stars, reveal that the Milky Way converts four to eight solar masses of interstellar gas and dust into new stars each year, researchers report in work submitted to arXiv.org on January 24. That range is two to four times the conventional estimate and corresponds to an annual birthrate in our galaxy of about 10 to 20 stars, because most stars are less massive than the sun.

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    At this rate, every million years — a blink of the eye in astronomical terms — our galaxy spawns 10 million to 20 million new stars. That’s enough to fill roughly 10,000 star clusters like the beautiful Pleiades cluster in the constellation Taurus. In contrast, many galaxies, including most of the ones that orbit the Milky Way, make no new stars at all.

    “The star formation rate is very important to understand for galaxy evolution,” says Thomas Siegert, an astrophysicist at the University of Würzburg in Germany. The more stars a galaxy makes, the faster it enriches itself with oxygen, iron and the other elements that stars create. Those elements then alter star-making gas clouds and can change the relative number of large and small stars that the gas clouds form.

    Siegert and his colleagues studied the observed intensity and spatial distribution of emission from aluminum-26 in our galaxy. A massive star creates this isotope during both life and death. During its life, the star blows the aluminum into space via a strong wind. If the star explodes when it dies, the resulting supernova forges more. The isotope, with a half-life of 700,000 years, decays and gives off gamma rays.

    Like X-rays, and unlike visible light, gamma rays penetrate the dust that cloaks the youngest stars. “We’re looking through the entire galaxy,” Siegert says. “We’re not X-raying it; here we’re gamma-raying it.”

    The more stars our galaxy spawns, the more gamma rays emerge. The best match with the observations, the researchers find, is a star formation rate of four to eight solar masses a year. That is much higher than the standard estimate for the Milky Way of about two solar masses a year.

    The revised rate is very realistic, says Pavel Kroupa, an astronomer at the University of Bonn in Germany who was not involved in the work. “I’m very impressed by the detailed modeling of how they account for the star formation process,” he says. “It’s a very beautiful work. I can see some ways of improving it, but this is really a major step in the absolutely correct direction.”

    Siegert cautions that it is difficult to tell how far the gamma rays have traveled before reaching us. In particular, if some of the observed emission arises nearby — within just a few hundred light-years of us — then the galaxy has less aluminum-26 than the researchers have calculated, which means the star formation rate is on the lower side of the new estimate. Still, he says it’s unlikely to be as low as the standard two solar masses per year.

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    In any event, the Milky Way is the most vigorous star creator in a collection of more than 100 nearby galaxies called the Local Group. The largest Local Group galaxy, Andromeda, converts only a fraction of a solar mass of gas and dust into new stars a year. Among Local Group galaxies, the Milky Way ranks second in size, but its high star formation rate means that we definitely try a lot harder.    More

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    Some of the earliest modern humans in Europe used bows and arrows

    A site in France briefly occupied by modern humans is littered with stone points that were probably used as arrowheads, showing that bows and arrows were used in Europe much earlier than we thought

    Humans

    22 February 2023

    By Michael Le Page
    Reproductions of arrows with flint heads like those found at Grotte Mandrin in FranceLudovic Slimak
    Bows and arrows were first used in Europe much earlier than we previously thought. More than 100 arrowheads have been found in a rock shelter briefly used by a group of modern humans 54,000 years ago in an early foray into Neanderthal territory.
    “It’s incredible how many we have,” says Laure Metz at Aix-Marseille University in France.
    Metz is part of a team that has been excavating a rock shelter called Grotte Mandrin in southern France. This shelter was used first by Neanderthals more than 80,000 years ago, and then by modern humans from about 45,000 years ago – around the time that modern humans displaced Neanderthals all across Europe.Advertisement
    But, last year, the team reported that, for a 40-year period around 54,000 years ago, Grotte Mandrin was used as a hunting camp by a small group of modern humans. The clinching evidence came from a baby tooth that isn’t Neanderthal.
    In the layers of earth from this time, Metz and her colleagues have now reported finding more than a thousand small stone points around 1 or 2 centimetres long. Of these, around 100 have been identified as broken or complete arrowheads, as they have one or more signs of impact damage resembling those seen when the team used newly made stone points as arrowheads. The others may be arrowheads too, but the researchers are unsure.
    “The tips from Mandrin could hardly have been used in any other way than to tip arrows,” says Marlize Lombard at the University of Johannesburg in South Africa, who wasn’t involved in the study.
    Researcher Ludovic Slimak holding a flint point from Grotte MandrinPhilippe PSAILA
    Most of the Mandrin arrowheads are broken. Some are arrowhead tips that broke off inside animals and were brought back to camp inside butchered meat, says Metz. Many of these show signs of charring from fires.
    The parts that remained attached to the shaft have also been found. Because of the work involved in making arrow shafts, says Metz, when an arrowhead broke, hunters would have brought the arrow back to camp and replaced the arrowhead, discarding the broken one.

    Before now, the earliest unambiguous evidence for bows and arrows in Europe came from finds in Stellmoor, Germany, dating to around 10,000 years ago, says Metz. However, it was considered likely that the modern humans who displaced Neanderthals around 45,000 years ago had bows and arrows.
    These humans were definitely using stone-tipped projectiles; the issue is that, with larger stone points, there is no way to tell if they were spearheads or arrowheads, says Metz. At some prehistoric sites in Europe, evidence of arrowheads may have been missed – archaeologists used to throw away smaller bits of stone, she says, regarding them as having no value.
    Bows and arrows were first developed in Africa at least 70,000 years ago. Lombard and others have found stone and bone arrowheads at several sites in southern Africa dating back as far as this. The modern humans who moved out of Africa may have spread the technology around the world.
    Despite presumably seeing bows in action, Neanderthals never developed them, says Metz. They kept using large, stone-tipped spears that were either thrust directly or thrown by hand, and so required close contact with their prey.
    The team has found no evidence that the arrows were used in conflict, but Metz says warfare is so ubiquitous in human societies that she is convinced it took place in prehistory too. She says that, while it is possible that this small group of modern humans was wiped out by Neanderthals despite having technological advantages such as bows and arrows, we just don’t know what happened to them. “We have no idea,” she says.

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    Don't Miss: Explore wildfire's power at Science Gallery London

    Was the shift to farming really the worst mistake in human history?The notion that our ancestors’ shift from a hunter-gatherer lifestyle to farming was disastrous for our health is well established, but a new study should prompt a rethink, says Michael Marshall More

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    Next Exit film review: New tale of the afterlife takes a wrong turn

    Two volunteers sign up for euthanasia to help a research project when evidence of consciousness after death emerges. The idea’s great, but the script could use a bit more life

    Humans

    22 February 2023

    By Simon Ings
    Teddy (Rahul Kohli) contronts his father (Marcelo Tubert)Magnet releasing
    Next Exit
    Mali Elfman
    Apple TV
    FROM out of nowhere, a chink of light appears. With painful slowness, it grows stronger: we are inching towards a half-open door. Beyond the door, everything seems normal. A little boy plays a game of pretend. At least, that is what we think. Soon enough we learn what is really going on: he is playing cards with his dead father.
    Nothing else in Mali Elfman’s debut feature lives up to this unsettling opening, though there is a … More

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    Was the shift to farming really the worst mistake in human history?

    The notion that our ancestors’ shift from a hunter-gatherer lifestyle to farming was disastrous for our health is well established, but a new study should prompt a rethink, says Michael Marshall

    Humans

    | Columnist

    22 February 2023

    By Michael Marshall
    Shutterstock/J. Lekavicius
    This is an extract from the Our Human Story email newsletter. Sign up to receive it for free in your inbox every month.
    STOP me if you have heard this one before: the transition to farming was a cataclysmic turn for the worse. Beginning around 12,000 years ago, some of our ancestors started cultivating crops, abandoning the egalitarian and sustainable hunter-gatherer lifestyle that had worked for hundreds of thousands of years. The result was poor health, limited diets, new diseases and unsustainable practices that have culminated with climate change and a sixth mass extinction.
    This narrative has become well … More

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    How to use the science of fat to make delicious, confit food

    Fat gets a bad rap, but it is key to making enjoyable foods like confit pork. You can also use the confit method for parsnips, says Sam Wong

    Humans

    22 February 2023

    By Sam Wong
    PhotoCuisine/Viel, Pierre Louis/StockFood
    FAT is a controversial subject in food science. We have all been told from an early age that it is unhealthy and something we should try to eat less of. But as we have said in New Scientist before, the science that led us to fear it is deeply flawed, and many studies have found that cutting down on fat brings no clear health benefits.
    In fact, fats are an essential part of our diet, a vital aid to cooking and key to what makes many of our favourite foods, such as chocolate, so enjoyable. To make smarter … More

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    The James Webb telescope found six galaxies that may be too hefty for their age

    The James Webb Space Telescope’s first peek at the distant universe unveiled galaxies that appear too big to exist.

    Six galaxies that formed in the universe’s first 700 million years seem to be up to 100 times more massive than standard cosmological theories predict, astronomer Ivo Labbé and colleagues report February 22 in Nature. “Adding up the stars in those galaxies, it would exceed the total amount of mass available in the universe at that time,” says Labbé, of the Swinburne University of Technology in Melbourne, Australia. “So you know that something is afoot.”

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    The telescope, also called JWST, released its first view of the early cosmos in July 2022 (SN: 7/11/22). Within days, Labbé and his colleagues had spotted about a dozen objects that looked particularly bright and red, a sign that they could be massive and far away.

    “They stand out immediately, you see them as soon as you look at these images,” says astrophysicist Erica Nelson of the University of Colorado Boulder.

    Measuring the amount of light each object emits in various wavelengths can give astronomers an idea of how far away each galaxy is, and how many stars it must have to emit all that light. Six of the objects that Nelson, Labbé and colleagues identified look like their light comes from no later than about 700 million years after the Big Bang. Those galaxies appear to hold up to 10 billion times the mass of our sun in stars. One of them might contain the mass of 100 billion suns.

    “You shouldn’t have had time to make things that have as many stars as the Milky Way that fast,” Nelson says. Our galaxy contains about 60 billion suns’ worth of stars — and it’s had more than 13 billion years to grow them. “It’s just crazy that these things seem to exist.”

    In the standard theories of cosmology, matter in the universe clumped together slowly, with small structures gradually merging to form larger ones. “If there are all these massive galaxies at early times, that’s just not happening,” Nelson says.

    One possible explanation is that there’s another, unknown way to form galaxies, Labbé says. “It seems like there’s a channel that’s a fast track, and the fast track creates monsters.”

    But it could also be that some of these galaxies host supermassive black holes in their cores, says astronomer Emma Curtis-Lake of the University of Hertfordshire in England, who was not part of the new study. What looks like starlight could instead be light from the gas and dust those black holes are devouring. JWST has already seen a candidate for an active supermassive black hole even earlier in the universe’s history than these galaxies are, she says, so it’s not impossible.

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    Finding a lot of supermassive black holes at such an early era would also be challenging to explain (SN: 3/16/18). But it wouldn’t require rewriting the standard model of cosmology the way extra-massive galaxies would.

    “The formation and growth of black holes at these early times is really not well understood,” she says. “There’s not a tension with cosmology there, just new physics to be understood of how they can form and grow, and we just never had the data before.”

    To know for sure what these distant objects are, Curtis-Lake says, astronomers need to confirm the galaxies’ distances and masses using spectra, more precise measurements of the galaxies’ light across many wavelengths (SN: 12/16/22).

    JWST has taken spectra for a few of these galaxies already, and more should be coming, Labbé says. “With luck, a year from now, we’ll know a lot more.” More

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    Hello Tomorrow! review: Selling holiday homes on the moon

    Apple TV+’s compelling new science-fiction offering is a retro-futurist piece, more 20th-century US social drama than technofest

    Humans

    15 February 2023

    By Bethan Ackerley
    Myrtle Mayburn (Alison Pill) has big doubts about her lunar holiday homeApple TV+
    Hello Tomorrow!
    Amit Bhalla, Lucas Jansen
    Apple TV+
    THERE is a certain school of thought that says “real” science fiction must be full of ideas about how science and technology might change our world. This is often called “hard” sci-fi, and there are those who view any deviation from this style with as bellicose an attitude as possible.
    I am not a purist: I prefer to think of sci-fi as a broad church, with the power to imagine almost … More