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Tag: cosmology

  • Giant ‘bubble’ in space could be source of powerful cosmic rays

    Giant ‘bubble’ in space could be source of powerful cosmic rays

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    Composite image of Cygnus OB2, with detected emissions shown in bright red, orange and blue colours.

    Conditions in the star-forming region Cygnus OB2 are ideal for producing high-energy cosmic rays.Credit: X-ray: NASA/CXC/SAO/J. Drake et al; H-alpha: Univ. of Hertfordshire/INT/IPHAS; Infrared: NASA/JPL-Caltech/Spitzer

    Astronomers have detected an enormous gamma-ray bubble that could be a source of the Milky Way’s most powerful cosmic rays — high-energy particles that rain down on Earth from space.

    The turbocharged galactic accelerator — dubbed a ‘super PeVatron’ — is capable of blasting out cosmic rays at energies of at least 10 petaelectronvolts (PeV; 1016 electronvolts), pushing the upper limits of the energies such particles are thought to reach in the Milky Way.

    The findings, published in Science Bulletin1, confirm that such high-energy sources exist in our galaxy. “We were looking for this kind of stuff for years,” says study co-author Zhen Cao, an astrophysicist at the Chinese Academy of Science’s Institute of High Energy Physics in Beijing. “Now we really see it.”

    China’s mountain observatory begins hunt for origins of cosmic rays

    Cosmic rays are subatomic particles, often protons or atomic nuclei, that zip through space at nearly the speed of light. Those in the Milky Way are known to reach energies of at least a few PeV, but locating the sources of very-high-energy cosmic rays has been notoriously difficult. This is because cosmic rays bounce off magnetic fields as they whizz through space, which means that their flight paths are so convoluted that it is hard to work out their places of origin. To get around this problem, researchers measure gamma-ray photons — particles produced by the interaction of cosmic rays with interstellar gas. Gamma rays carry 10% of the energy of cosmic rays, and they travel in straight lines, making it easier to pinpoint potential cosmic-ray sources.

    Cao and his colleagues used the Large High Altitude Air Shower Observatory (LHAASO) in Daocheng, China, to measure gamma rays coming from Cygnus OB2, a massive star-forming region in the Cygnus constellation.

    The LHAASO team detected a huge gamma-ray-emitting structure, known as a bubble, that was emitting photons with energies higher than 1 PeV, with one measuring 2.5 PeV. This suggests that the area could be generating cosmic rays that reach energies of somewhere between 10 and 25 PeV at least, says Cao.

    The hot, short-lived stars within Cygnus OB2 produce stellar winds that reach speeds of thousands of kilometres per second, says Cao. When these gusts collide with gas and other material that lies between stars, they create ideal conditions for accelerating cosmic rays to high energy levels.

    The observations suggest that cosmic rays originating in the Milky Way can reach much higher energies than previously thought, says Gavin Rowell, an astroparticle physicist at the University of Adelaide in Australia. “The result is certainly very exciting,” he adds.

    Next, Cao and his team will investigate Cygnus OB2 in finer detail to try to locate the precise source of the high-energy cosmic rays in the star cluster. They will also continue to hunt for other super accelerators in the Milky Way, says Cao.

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  • Most detailed X-ray sky map bolsters standard model of cosmology

    Most detailed X-ray sky map bolsters standard model of cosmology

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    Astronomers have reconstructed nearly nine billion years of cosmic evolution by tracing the X-ray glow of distant clusters of galaxies. The analysis supports the standard model of cosmology, according to which the gravitational pull of dark matter — a still-mysterious substance — is the main factor shaping the Universe’s structure.

    “We do not see any departures from the standard model of cosmology,” says Esra Bulbul, a senior member of the team and an astrophysicist at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany. The results are described1 in a preprint posted online on 14 February.

    The galactic clusters were spotted in the most detailed picture ever taken of the sky using X-rays, which was published late last month. This image revealed around 900,000 X-ray sources, from black holes to the relics of supernova explosions.

    Space telescope to chart first map of the Universe in high-energy X-rays

    The picture was the result of the first six months of operation of eROSITA (Extended Roentgen Survey with an Imaging Telescope Array), one of two X-ray telescopes that were launched into space in July 2019 aboard the Russian spacecraft SRG (Spectrum-Roentgen-Gamma). eROSITA scans the sky as the spacecraft spins, and collects data over wider angles than are possible for most other X-ray observatories. This enables it to slowly sweep the entire sky every six months.

    By an unusual arrangement, the eROSITA team is split into two — with a group based in Germany and one based in Russia — and each has exclusive access to eROSITA data from only half of the sky. The mission was originally intended to cover the sky eight times. But Russia’s full-scale invasion of Ukraine in 2022 led the German government to freeze its collaborations, and eROSITA was put on stand-by. By then, it had completed four full sky scans.

    The data that Bulbul and her collaborators have used so far were from their half of the sky, collected during the first scan. Even so, the results are already among the most precise cosmological measurements ever made. It is unclear when the Russia-based group will publish its data and analysis.

    Evolving Universe

    By looking across vast distances, telescopes such as eROSITA also peer back in time, to see the various stages of cosmic evolution. As the Universe expands, the space between galaxies tends to grow larger, but at the same time, galaxies are pulled towards one another by gravity, including their own and especially that of dark matter. As a result, giant cosmic voids form and expand, and matter increasingly clumps into a web of giant clusters of galaxies.

    Cosmic map reveals a not-so-lumpy Universe

    Astrophysicist Vittorio Ghirardini at the MPE worked with Bulbul and other collaborators to map the haloes of intergalactic gas surrounding more than 5,000 galaxy clusters in 3D using a combination of eROSITA’s data and an existing map made by the Dark Energy Survey (DES), which uses a telescope in Chile. “Since X-rays are very powerful at detecting haloes, we can be very certain that there is a very big structure there,” Ghirardini says.

    The observations span a vast area and time period — approximately 9 billion years. This allowed the researchers to calculate some of the most crucial parameters of cosmic evolution, including ‘lumpiness’ — how much the total mass of matter has concentrated in the cosmic web at any given time. In 2017, similar calculations based on DES data alone seemed to show2 that the web had become lumpy much more slowly than the standard model predicts, but in the latest analysis, that discrepancy has gone away. (Results made public last year from a separate cosmology experiment also indicated harmony with the standard model3.)

    Neutrino boundary

    Furthermore, the galactic-cluster data enabled the team to tease out the role of neutrinos in shaping the cosmic web. Copious amounts of these elementary particles were produced in the Big Bang, and their low masses and reluctance to interact with other particles mean that they act like dark matter, forming haloes around galaxies. From this information, the astrophysicists calculated that neutrinos could have masses of no more than 0.22 electronvolts (an electron has a mass of around 500,000 eV). “These are the tightest measurements of the neutrino masses available,” Bulbul says; lab measurements on Earth have so far established4 a larger upper limit of 0.8 eV.

    Even if eROSITA’s observations never resume, the team’s work is not over yet. “We have a lot more data we are working on,” says Bulbul. The team will eventually be able to map gas halos that are smaller, fainter or more distant than the ones in the current catalogue — and to increase the precision of the measurements.

    The same applies to the other types of X-ray source mapped by eROSITA, such as quasars, the intensely bright supermassive black holes at the centres of many galaxies. Studies on this trove of information have only just begun, says eROSITA spokesperson Mara Salvato, an astrophysicist at the MPE. “By the end of the mission, we expect to catalogue three million objects.”

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  • Is the universe conscious? It seems impossible until you do the maths

    Is the universe conscious? It seems impossible until you do the maths

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    THEY call it the “unreasonable effectiveness of mathematics”. Physicist Eugene Wigner coined the phrase in the 1960s to encapsulate the curious fact that merely by manipulating numbers we can describe and predict all manner of natural phenomena with astonishing clarity, from the movements of planets and the strange behaviour of fundamental particles to the consequences of a collision between two black holes billions of light years away. Now, some are wondering if maths can succeed where all else has failed, unravelling whatever it is that allows us to contemplate the laws of nature in the first place.

    It is a big ask. The question of how matter gives rise to felt experience is one of the most vexing problems we know of. And sure enough, the first fleshed-out mathematical model of consciousness has generated huge debate about whether it can tell us anything sensible. But as mathematicians work to hone and extend their tools for peering deep inside ourselves, they are confronting some eye-popping conclusions.

    Not least, what they are uncovering seems to suggest that if we are to achieve a precise description of consciousness, we may have to ditch our intuitions and accept that all kinds of inanimate matter could be conscious – maybe even the universe as a whole. “This could be the beginning of a scientific revolution,” says Johannes Kleiner, a mathematician at the Munich Centre for Mathematical Philosophy in Germany.

    If so, it has been a long time coming. Philosophers have pondered the nature of consciousness for a couple of thousand years, largely to no avail. Then, half a century ago, biologists got involved. They have discovered …

    Article amended on 4 May 2020

    Correction: We have updated the campus of Inland Norway University of Applied Sciences at which Hedda Hassel Mørch is based, and changed the attribution of work on the effects of sleep or sedation on phi.

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