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  • richardmitnick 12:54 pm on July 6, 2020 Permalink | Reply
    Tags: "Herschel and Planck views of star formation", , , Basic Research, ,   

    From European Space Agency – United space in Europe: “Herschel and Planck views of star formation” 

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    From European Space Agency – United space in Europe

    From United Space in Europe


    A collection of intriguing images based on data from ESA’s Herschel and Planck space telescopes show the influence of magnetic fields on the clouds of gas and dust where stars are forming.

    ESA/Herschel spacecraft active from 2009 to 2013

    ESA/Planck 2009 to 2013

    The images are part of a study by astronomer Juan D. Soler of the Max Planck Institute for Astronomy in Heidelberg, Germany, who used data gathered during Planck’s all-sky observations and Herschel’s ‘Gould Belt Survey’. Both Herschel and Planck were instrumental in exploring the cool Universe, and shed light on the many complexities of the interstellar medium – the mix of gas and dust that fills the space between the stars in a galaxy. Both telescopes ended their operational lifetime in 2013, but new discoveries continue to be made from their treasure trove of data.

    Herschel revealed in unprecedented detail the filaments of dense material in molecular clouds across our Milky Way galaxy, and their key role in the process of star formation. Filaments can fragment into clumps which eventually collapse into stars. The results from Herschel show a close link between filament structure and the presence of dense clumps.

    Herschel observed the sky in far-infrared and sub-millimetre wavelengths, and the data is seen in these images as a mixture of different colours, with light emitted by interstellar dust grains mixed within the gas. The texture of faint grey bands stretching across the images like a drapery pattern, is based on Planck’s measurements of the direction of the polarised light emitted by the dust and show the orientation of the magnetic field.

    The study explored several nearby molecular clouds all within 1500 light years from the Sun including Taurus, Ophiuchus, Lupus, Corona Australis, Chamaeleon-Musca, Aquila Rift, Perseus, and Orion.

    In this study, published last year in Astronomy & Astrophysics, the Herschel data were used to calculate the density of the molecular clouds along our line of sight to investigate how the interstellar medium interacts with surrounding magnetic fields.

    Astronomers have long thought magnetic fields play a role in star formation, along with other factors such as gas pressure, turbulence, and gravity. However, observations of the magnetic fields in and around nearby star-forming clouds have been limited until the advent of Planck.

    The paper builds upon previous studies by the Planck collaboration to investigate how interstellar matter is likely coupled to these magnetic field lines, moving along them until multiple ‘conveyor belts’ of matter converge to form an area of high density. This can be seen in some images in the form of ‘striations’, which is material that appears perpendicular to the filament. These regions continue to receive matter along the magnetic lines until they collapse under their own gravity, becoming cooler and dense enough to create stellar newborns.

    While the magnetic field is preferentially orientated perpendicular to the densest filaments, it appears that the orientation of the magnetic field changes from parallel to perpendicular with increasing density. However, there appears to be no correlation between the star formation rate and the orientation between filaments and magnetic fields, although the study also finds a correlation between the distribution of projected densities.

    Corona Australis molecular cloud viewed by Herschel and Planck

    Taurus Molecular Cloud viewed by Herschel and Planck

    Rho Ophiuchi cloud complex viewed by Herschel and Planck

    Lupus cloud complex viewed by Herschel and Planck

    The Aquila Rift star-forming complex viewed by Herschel and Planck

    Many more at the full article.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 12:05 pm on July 6, 2020 Permalink | Reply
    Tags: "Star-forming region IRAS 12272-6240 probed in infrared", According to the paper the results confirm that IRAS 12272-6240 is a giant young complex one million years old and still active at its nucleus., , , Basic Research, ,   

    From phys.org: “Star-forming region IRAS 12272-6240 probed in infrared” 

    From phys.org

    July 6, 2020
    Tomasz Nowakowski

    Mid- and far-infrared composite colour images of the region centred on IRAS 12272-6240. Credit: Tapia et al., 2020.

    Astronomers have conducted spectroscopic observations of a star-forming region known as IRAS 12272-6240. Results of this observational campaign shed more light on the nature of this massive and complex region. The study was detailed in a paper published in MNRAS.

    Star-forming regions are essential for astronomers to better understand the processes of star formation and stellar evolution. Observations of such regions have the potential to expand the list of known stars, protostars, young stellar objects and clumps, which could be then be studied comprehensively in various wavelengths in order to get more insights into initial stages of the stellar life cycle.

    Located some 30,300 light years away, at the far end of the Carina-Sagittarius arm of the Milky Way galaxy, IRAS 12272-6240 is a complex star-forming region with a compact massive dense clump and several associated masers.

    A team of astronomers led by Mauricio Tapia of the National Autonomous University of Mexico took a closer look at IRAS 12272-6240. Using the Baade/Magellan telescope in Chile, they performed near-infrared imaging and low-resolution spectroscopy of this region.

    Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high.

    The study was complemented by data from the Herschel Infrared GALactic Plane survey (Hi-GAL) and from NASA’s two spacecraft: Spitzer and Wide-field Infrared Survey Explorer (WISE).

    NASA/Spitzer Infrared Telescope. No longer in service.


    “In this work, we present new sub-arcsec broad- and narrowband near-IR imaging of a 120 x 120 square arcsec area centered on the massive star-forming region IRAS 12272-6240. We supplemented these data with HI-GAL/Herschel far-IR images combined with archive IRAC/Spitzer and WISE mid-IR observations,” the astronomers wrote in the paper.

    The observations found that IRAS 12272-6240 has a compact massive (around 13,100 solar masses) dense dust clump containing two young stellar objects (YSOs) of Class I, designated Irs-1N and Irs-1S, and associated methanol, hydroxide as well as water masers. The two YSOs probably form a binary system that is about 21,000 AU wide.

    The data suggest that the central star of IRAS 12272-6240 is most likely of spectral type O9V, has an effective temperature of about 33,500 K and is about 23 times more massive than our sun. The central star seems to have a pre-planetary disc with a mass of 0.01 solar masses at an inclination angle of 32 degrees.

    The astronomers were able to distinguish two embedded clusters in IRAS 12272-6240 differing in age, spatial distribution and physical characteristics. The older and more extended of these two is about 1 million years old, contains more than 50 stars in its nucleus and a halo of some 80 fainter stars extending to a radius of about 4.24 light years. The second one, consisting of at least 35 identified members, is estimated to be significantly younger than 1 million years and appears to be more deeply embedded.

    According to the paper, the results confirm that IRAS 12272-6240 is a giant young complex located where massive star formation processes started some one million years ago and is still active at its nucleus.

    See the full article here .


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  • richardmitnick 10:35 am on July 6, 2020 Permalink | Reply
    Tags: "White dwarfs reveal new insights into the origin of carbon in the universe", 1.5 solar masses represents the minimum mass for a star to spread carbon-enriched ashes upon its death., , Astrophysicists still debate which types of stars are the primary source of the carbon in our own galaxy., , Basic Research, Carbon in our own galaxy, , Every carbon atom in the universe was created by stars through the fusion of three helium nuclei.,   

    From UC Santa Cruz: “White dwarfs reveal new insights into the origin of carbon in the universe” 

    From UC Santa Cruz

    July 06, 2020
    Tim Stephens

    NGC 7789, also known as Caroline’s Rose, is an old open star cluster of the Milky Way, which lies about 8,000 light-years away toward the constellation Cassiopeia. It hosts a few white dwarfs of unusually high mass that were analyzed in this study. (Image credit: Guillaume Seigneuret and NASA)

    A new analysis of white dwarf stars supports their role as a key source of carbon, an element crucial to all life, in the Milky Way and other galaxies.

    White dwarf star in the process of solidifying. Credit: University of Warwick/Mark Garlick

    Approximately 90 percent of all stars end their lives as white dwarfs, very dense stellar remnants that gradually cool and dim over billions of years. With their final few breaths before they collapse, however, these stars leave an important legacy, spreading their ashes into the surrounding space through stellar winds enriched with chemical elements, including carbon, newly synthesized in the star’s deep interior during the last stages before its death.

    Every carbon atom in the universe was created by stars, through the fusion of three helium nuclei. But astrophysicists still debate which types of stars are the primary source of the carbon in our own galaxy, the Milky Way. Some studies favor low-mass stars that blew off their envelopes in stellar winds and became white dwarfs, while others favor massive stars that eventually exploded as supernovae.

    In the new study, published July 6 in Nature Astronomy, an international team of astronomers discovered and analyzed white dwarfs in open star clusters in the Milky Way, and their findings help shed light on the origin of the carbon in our galaxy. Open star clusters are groups of up to a few thousand stars, formed from the same giant molecular cloud and roughly the same age, and held together by mutual gravitational attraction. The study was based on astronomical observations conducted in 2018 at the W. M. Keck Observatory in Hawaii and led by coauthor Enrico Ramirez-Ruiz, professor of astronomy and astrophysics at UC Santa Cruz.

    Keck Observatory, operated by Caltech and the University of California, Maunakea Hawaii USA, 4,207 m (13,802 ft)

    “From the analysis of the observed Keck spectra, it was possible to measure the masses of the white dwarfs. Using the theory of stellar evolution, we were able to trace back to the progenitor stars and derive their masses at birth,” explained Ramirez-Ruiz, who also holds a Niels Bohr Professorship at the University of Copenhagen.

    The relationship between the initial masses of stars and their final masses as white dwarfs is known as the initial-final mass relation, a fundamental diagnostic in astrophysics that integrates information from the entire life cycles of stars, linking birth to death. In general, the more massive the star at birth, the more massive the white dwarf left at its death, and this trend has been supported on both observational and theoretical grounds.

    But analysis of the newly discovered white dwarfs in old open clusters gave a surprising result: the masses of these white dwarfs were notably larger than expected, putting a “kink” in the initial-final mass relation for stars with initial masses in a certain range.

    “Our study interprets this kink in the initial-final mass relationship as the signature of the synthesis of carbon made by low-mass stars in the Milky Way,” said lead author Paola Marigo at the University of Padua in Italy.

    In the last phases of their lives, stars twice as massive as our Sun produced new carbon atoms in their hot interiors, transported them to the surface, and finally spread them into the interstellar medium through gentle stellar winds. The team’s detailed stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to allow the central cores of these stars, the future white dwarfs, to grow appreciably in mass.

    Analyzing the initial-final mass relation around the kink, the researchers concluded that stars bigger than 2 solar masses also contributed to the galactic enrichment of carbon, while stars of less than 1.5 solar masses did not. In other words, 1.5 solar masses represents the minimum mass for a star to spread carbon-enriched ashes upon its death.

    These findings place stringent constraints on how and when carbon, the element essential to life on Earth, was produced by the stars of our galaxy, eventually ending up trapped in the raw material from which the Sun and its planetary system were formed 4.6 billion years ago.

    “Now we know that the carbon came from stars with a birth mass of not less than roughly 1.5 solar masses,” said Marigo.

    Coauthor Pier-Emmanuel Tremblay at University of Warwick said, “One of most exciting aspects of this research is that it impacts the age of known white dwarfs, which are essential cosmic probes to understand the formation history of the Milky Way. The initial-to-final mass relation is also what sets the lower mass limit for supernovae, the gigantic explosions seen at large distances and that are really important to understand the nature of the universe.”

    By combining the theories of cosmology and stellar evolution, the researchers concluded that bright carbon-rich stars close to their death, quite similar to the progenitors of the white dwarfs analyzed in this study, are presently contributing to a vast amount of the light emitted by very distant galaxies. This light, carrying the signature of newly produced carbon, is routinely collected by large telescopes to probe the evolution of cosmic structures. A reliable interpretation of this light depends on understanding the synthesis of carbon in stars.

    In addition to Marigo, Tremblay, and Ramirez-Ruiz, the coauthors of the paper include scientists at Johns Hopkins University, American Museum of Natural History in New York, Columbia University, Space Telescope Science Institute, University of Warwick, University of Montreal, University of Uppsala, International School for Advanced Studies in Trieste, Italian National Institute for Astrophysics, and the University of Geneva. This research was supported by the European Union through an ERC Consolidator Grant and the DNRF through a Niels Bohr Professorship.

    See the full article here .


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    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)


    UC Observatories Lick Autmated Planet Finder, fully robotic 2.4-meter optical telescope at Lick Observatory, situated on the summit of Mount Hamilton, east of San Jose, California, USA

    The UCO Lick C. Donald Shane telescope is a 120-inch (3.0-meter) reflecting telescope located at the Lick Observatory, Mt Hamilton, in San Jose, California, Altitude 1,283 m (4,209 ft)

    UC Santa Cruz campus

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

  • richardmitnick 9:11 am on July 6, 2020 Permalink | Reply
    Tags: "U.K. buys stake in satellite company that could spoil astronomy", , , “It’s the stuff at 1000 kilometers that is the real killer for astronomy” says Mark McCaughrean of the European Space Agency., “Megaconstellations” of satellites, Basic Research, , OneWeb filed for bankruptcy protection in March 2020, , The U.K. government said in a statement today that its acquisition of OneWeb will “contribute to the government’s plan to join the first rank of space nations.”, U.K. government and the Indian cellphone operator Bharti Global have successfully bid to rescue OneWeb with a $1 billion investment.   

    From Science Magazine: “U.K. buys stake in satellite company that could spoil astronomy” 

    From Science Magazine

    Jul. 3, 2020
    Daniel Clery

    OneWeb plans to launch as many as 42,000 satellites to an orbit that could harm astronomy. Credit: NASA/Kim Shiflett

    When OneWeb filed for bankruptcy protection in March, astronomers breathed a sigh of relief. The company planned to launch thousands of internet-providing satellites into low-Earth orbit, where their reflections could disrupt the observations of ground-based telescopes. But now, the company has risen from the grave with the announcement today that the U.K. government and the Indian cellphone operator Bharti Global have successfully bid to rescue OneWeb with a $1 billion investment.

    The revived company now plans an even larger constellation of up to 42,000 satellites, at an altitude of 1200 kilometers—the worst possible outcome for astronomers. At that altitude, satellites will leave bright trails across telescope images all through the night, effectively ruining the observations of survey telescopes such as the 8-meter Vera C. Rubin Observatory, under construction in Chile. “It’s the stuff at 1000 kilometers that is the real killer for astronomy,” says Mark McCaughrean of the European Space Agency, speaking at a briefing organized by the European Astronomical Society (EAS). “Engagement [with astronomers] has to happen and it has to happen now.”

    Astronomers first became concerned about such “megaconstellations” last year, when the launch company SpaceX lofted the first batch of its Starlink satellites. The aim of the project is to provide internet access in areas hard to reach with fiber-optic cables. The satellites, launched 60 at a time in a single rocket, proved to be highly visible in the sky, to the alarm of astronomers. The company has now launched 540 Starlink satellites—part of an initial goal of 1584—and aims to provide a service in the United States and Canada before the end of the year.

    Early on, astronomers began working with SpaceX to mitigate the impact of its satellites. In a January launch, one satellite was covered with an antireflective coating (dubbed Darksat), and in June, one satellite carried a sunshade to stop reflections (Visorsat). Although Darksat partially reduced the satellite’s visibility, it wasn’t enough to satisfy astronomers. Visorsat has yet to reach its operational altitude so, Olivier Hainaut of the European Southern Observatory told the EAS briefing, “we don’t know yet” how bright it will appear. But McCaughrean says Starlink’s next launch will be populated entirely with Visorsats.

    OneWeb is one of several other companies chasing Starlink with similar goals. Astronomers had only limited interactions with the company before it filed for Chapter 11 protection in March with 74 satellites launched toward an initial goal of 650. While new owners were being sought, OneWeb applied for permission to expand its constellation to 42,000.

    The U.K. government said in a statement today that its acquisition of OneWeb will “contribute to the government’s plan to join the first rank of space nations.” Initial reports suggested the government wanted to transform the constellation into a navigation system akin to GPS, because with Brexit, the United Kingdom will no longer be a governing member of Europe’s Galileo navigation system. But there is no mention of navigation plans in today’s statement.

    The rescue of OneWeb still has political and legal hurdles to overcome, but Robert Massey of the Royal Astronomical Society told the EAS briefing: “I would hope the government uses its leverage to ensure OneWeb are a good partner and engages with the scientific community.” He adds, “It’s hard to believe they didn’t know.”

    See the full article here .


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  • richardmitnick 9:47 am on July 5, 2020 Permalink | Reply
    Tags: "Astronomers Are Uncovering the Magnetic Soul of the Universe", , , Basic Research, , , ,   

    From Quanta Magazine via WIRED: “Astronomers Are Uncovering the Magnetic Soul of the Universe” 

    From Quanta Magazine



    Natalie Wolchover

    Researchers are discovering that magnetic fields permeate much of the cosmos. If these fields date back to the Big Bang, they could solve a cosmological mystery.

    Hidden magnetic field lines stretch millions of light years across the universe.Illustration: Pauline Voß/Quanta Magazine.

    Anytime astronomers figure out a new way of looking for magnetic fields in ever more remote regions of the cosmos, inexplicably, they find them.

    These force fields—the same entities that emanate from fridge magnets—surround Earth, the sun, and all galaxies. Twenty years ago, astronomers started to detect magnetism permeating entire galaxy clusters, including the space between one galaxy and the next. Invisible field lines swoop through intergalactic space like the grooves of a fingerprint.

    Last year, astronomers finally managed to examine a far sparser region of space—the expanse between galaxy clusters. There, they discovered the largest magnetic field yet: 10 million light-years of magnetized space spanning the entire length of this “filament” of the cosmic web [Science]. A second magnetized filament has already been spotted elsewhere in the cosmos by means of the same techniques. “We are just looking at the tip of the iceberg, probably,” said Federica Govoni of the National Institute for Astrophysics in Cagliari, Italy, who led the first detection.

    The question is: Where did these enormous magnetic fields come from?

    “It clearly cannot be related to the activity of single galaxies or single explosions or, I don’t know, winds from supernovae,” said Franco Vazza, an astrophysicist at the University of Bologna who makes state-of-the-art computer simulations of cosmic magnetic fields. “This goes much beyond that.”

    One possibility is that cosmic magnetism is primordial, tracing all the way back to the birth of the universe. In that case, weak magnetism should exist everywhere, even in the “voids” of the cosmic web—the very darkest, emptiest regions of the universe. The omnipresent magnetism would have seeded the stronger fields that blossomed in galaxies and clusters.

    The cosmic web, shown here in a computer simulation, is the large-scale structure of the universe. Dense regions are filled with galaxies and galaxy clusters. Thin filaments connect these clumps. Voids are nearly empty regions of space.Illustration: Springel & others/Virgo Consortium.

    Primordial magnetism might also help resolve another cosmological conundrum known as the Hubble tension—probably the hottest topic in cosmology.

    The problem at the heart of the Hubble tension is that the universe seems to be expanding significantly faster than expected based on its known ingredients. In a paper posted online in April and under review with Physical Review Letters, the cosmologists Karsten Jedamzik and Levon Pogosian argue that weak magnetic fields in the early universe would lead to the faster cosmic expansion rate seen today.

    Primordial magnetism relieves the Hubble tension so simply that Jedamzik and Pogosian’s paper has drawn swift attention. “This is an excellent paper and idea,” said Marc Kamionkowski, a theoretical cosmologist at Johns Hopkins University who has proposed other solutions to the Hubble tension.

    Kamionkowski and others say more checks are needed to ensure that the early magnetism doesn’t throw off other cosmological calculations. And even if the idea works on paper, researchers will need to find conclusive evidence of primordial magnetism to be sure it’s the missing agent that shaped the universe.

    Still, in all the years of talk about the Hubble tension, it’s perhaps strange that no one considered magnetism before. According to Pogosian, who is a professor at Simon Fraser University in Canada, most cosmologists hardly think about magnetism. “Everyone knows it’s one of those big puzzles,” he said. But for decades, there was no way to tell whether magnetism is truly ubiquitous and thus a primordial component of the cosmos, so cosmologists largely stopped paying attention.

    Meanwhile, astrophysicists kept collecting data. The weight of evidence has led most of them to suspect that magnetism is indeed everywhere.

    The Magnetic Soul of the Universe

    In the year 1600, the English scientist William Gilbert’s studies of lodestones—naturally magnetized rocks that people had been fashioning into compasses for thousands of years—led him to opine that their magnetic force “imitates a soul.” He correctly surmised that Earth itself is a “great magnet,” and that lodestones “look toward the poles of the Earth.”

    Magnetic fields arise anytime electric charge flows. Earth’s field, for instance, emanates from its inner “dynamo,” the current of liquid iron churning in its core. The fields of fridge magnets and lodestones come from electrons spinning around their constituent atoms.

    Cosmological simulations illustrate two possible explanations for how magnetic fields came to permeate galaxy clusters. At left, the fields grow from uniform “seed” fields that filled the cosmos in the moments after the Big Bang. At right, astrophysical processes such as star formation and the flow of matter into supermassive black holes create magnetized winds that spill out from galaxies.Video: F. Vazza.

    However, once a “seed” magnetic field arises from charged particles in motion, it can become bigger and stronger by aligning weaker fields with it. Magnetism “is a little bit like a living organism,” said Torsten Enßlin, a theoretical astrophysicist at the Max Planck Institute for Astrophysics in Garching, Germany, “because magnetic fields tap into every free energy source they can hold onto and grow. They can spread and affect other areas with their presence, where they grow as well.”

    Ruth Durrer, a theoretical cosmologist at the University of Geneva, explained that magnetism is the only force apart from gravity that can shape the large-scale structure of the cosmos, because only magnetism and gravity can “reach out to you” across vast distances. Electricity, by contrast, is local and short-lived, since the positive and negative charge in any region will neutralize overall. But you can’t cancel out magnetic fields; they tend to add up and survive.

    Yet for all their power, these force fields keep low profiles. They are immaterial, perceptible only when acting upon other things. “You can’t just take a picture of a magnetic field; it doesn’t work like that,” said Reinout van Weeren, an astronomer at Leiden University who was involved in the recent detections of magnetized filaments.

    In their paper last year, van Weeren and 28 coauthors inferred the presence of a magnetic field in the filament between galaxy clusters Abell 399 and Abell 401 from the way the field redirects high-speed electrons and other charged particles passing through it. As their paths twist in the field, these charged particles release faint “synchrotron radiation.”

    The synchrotron signal is strongest at low radio frequencies, making it ripe for detection by LOFAR, an array of 20,000 low-frequency radio antennas spread across Europe.

    ASTRON LOFAR European Map

    The team actually gathered data from the filament back in 2014 during a single eight-hour stretch, but the data sat waiting as the radio astronomy community spent years figuring out how to improve the calibration of LOFAR’s measurements. Earth’s atmosphere refracts radio waves that pass through it, so LOFAR views the cosmos as if from the bottom of a swimming pool. The researchers solved the problem by tracking the wobble of “beacons” in the sky—radio emitters with precisely known locations—and correcting for this wobble to deblur all the data. When they applied the deblurring algorithm to data from the filament, they saw the glow of synchrotron emissions right away.

    LOFAR consists of 20,000 individual radio antennas spread across Europe.Photograph: ASTRON.

    The filament looks magnetized throughout, not just near the galaxy clusters that are moving toward each other from either end. The researchers hope that a 50-hour data set they’re analyzing now will reveal more detail. Additional observations have recently uncovered magnetic fields extending throughout a second filament. Researchers plan to publish this work soon.

    The presence of enormous magnetic fields in at least these two filaments provides important new information. “It has spurred quite some activity,” van Weeren said, “because now we know that magnetic fields are relatively strong.”

    A Light Through the Voids

    If these magnetic fields arose in the infant universe, the question becomes: how? “People have been thinking about this problem for a long time,” said Tanmay Vachaspati of Arizona State University.

    In 1991, Vachaspati proposed that magnetic fields might have arisen during the electroweak phase transition—the moment, a split second after the Big Bang, when the electromagnetic and weak nuclear forces became distinct. Others have suggested that magnetism materialized microseconds later, when protons formed. Or soon after that: The late astrophysicist Ted Harrison argued in the earliest primordial magnetogenesis theory in 1973 that the turbulent plasma of protons and electrons might have spun up the first magnetic fields. Still others have proposed that space became magnetized before all this, during cosmic inflation—the explosive expansion of space that purportedly jump-started the Big Bang itself. It’s also possible that it didn’t happen until the growth of structures a billion years later.

    The way to test theories of magnetogenesis is to study the pattern of magnetic fields in the most pristine patches of intergalactic space, such as the quiet parts of filaments and the even emptier voids. Certain details—such as whether the field lines are smooth, helical, or “curved every which way, like a ball of yarn or something” (per Vachaspati), and how the pattern changes in different places and on different scales—carry rich information that can be compared to theory and simulations. For example, if the magnetic fields arose during the electroweak phase transition, as Vachaspati proposed, then the resulting field lines should be helical, “like a corkscrew,” he said.

    The hitch is that it’s difficult to detect force fields that have nothing to push on.

    One method, pioneered by the English scientist Michael Faraday back in 1845, detects a magnetic field from the way it rotates the polarization direction of light passing through it. The amount of “Faraday rotation” depends on the strength of the magnetic field and the frequency of the light. So by measuring the polarization at different frequencies, you can infer the strength of magnetism along the line of sight. “If you do it from different places, you can make a 3D map,” said Enßlin.

    Illustration: Samuel Velasco/Quanta Magazine.

    Researchers have started to make [MNRAS] rough Faraday rotation measurements using LOFAR, but the telescope has trouble picking out the extremely faint signal. Valentina Vacca, an astronomer and a colleague of Govoni’s at the National Institute for Astrophysics, devised an algorithm a few years ago for teasing out subtle Faraday rotation signals statistically, by stacking together many measurements of empty places. “In principle, this can be used for voids,” Vacca said.

    But the Faraday technique will really take off when the next-generation radio telescope, a gargantuan international project called the Square Kilometer Array, starts up in 2027. “SKA should produce a fantastic Faraday grid,” Enßlin said.

    For now, the only evidence of magnetism in the voids is what observers don’t see when they look at objects called blazars located behind voids.

    Blazars are bright beams of gamma rays and other energetic light and matter powered by supermassive black holes. As the gamma rays travel through space, they sometimes collide with ancient microwaves, morphing into an electron and a positron as a result. These particles then fizzle and turn into lower-energy gamma rays.

    But if the blazar’s light passes through a magnetized void, the lower-energy gamma rays will appear to be missing, reasoned Andrii Neronov and Ievgen Vovk of the Geneva Observatory in 2010. The magnetic field will deflect the electrons and positrons out of the line of sight. When they decay into lower-energy gamma rays, those gamma rays won’t be pointed at us.

    Illustration: Samuel Velasco/Quanta Magazine.

    Indeed, when Neronov and Vovk analyzed data from a suitably located blazar, they saw its high-energy gamma rays, but not the low-energy gamma-ray signal. “It’s the absence of a signal that is a signal,” Vachaspati said.

    A nonsignal is hardly a smoking gun, and alternative explanations for the missing gamma rays have been suggested. However, follow-up observations have increasingly pointed to Neronov and Vovk’s hypothesis that voids are magnetized. “It’s the majority view,” Durrer said. Most convincingly, in 2015, one team overlaid many measurements of blazars behind voids and managed to tease [Physical Review Letters] out a faint halo of low-energy gamma rays around the blazars. The effect is exactly what would be expected if the particles were being scattered by faint magnetic fields—measuring only about a millionth of a trillionth as strong as a fridge magnet’s.

    Cosmology’s Biggest Mystery

    Strikingly, this exact amount of primordial magnetism may be just what’s needed to resolve the Hubble tension—the problem of the universe’s curiously fast expansion.

    That’s what Pogosian realized when he saw recent computer simulations [Physical Review Letters] by Karsten Jedamzik of the University of Montpellier in France and a collaborator. The researchers added weak magnetic fields to a simulated, plasma-filled young universe and found that protons and electrons in the plasma flew along the magnetic field lines and accumulated in the regions of weakest field strength. This clumping effect made the protons and electrons combine into hydrogen—an early phase change known as recombination—earlier than they would have otherwise.

    Pogosian, reading Jedamzik’s paper, saw that this could address the Hubble tension. Cosmologists calculate how fast space should be expanding today by observing ancient light emitted during recombination. The light shows a young universe studded with blobs that formed from sound waves sloshing around in the primordial plasma. If recombination happened earlier than supposed due to the clumping effect of magnetic fields, then sound waves couldn’t have propagated as far beforehand, and the resulting blobs would be smaller. That means the blobs we see in the sky from the time of recombination must be closer to us than researchers supposed. The light coming from the blobs must have traveled a shorter distance to reach us, meaning the light must have been traversing faster-expanding space. “It’s like trying to run on an expanding surface; you cover less distance,” Pogosian said.

    The upshot is that smaller blobs mean a higher inferred cosmic expansion rate—bringing the inferred rate much closer to measurements of how fast supernovas and other astronomical objects actually seem to be flying apart.

    “I thought, wow,” Pogosian said, “this could be pointing us to [magnetic fields’] actual presence. So I wrote Karsten immediately.” The two got together in Montpellier in February, just before the lockdown. Their calculations indicated that, indeed, the amount of primordial magnetism needed to address the Hubble tension also agrees with the blazar observations and the estimated size of initial fields needed to grow the enormous magnetic fields spanning galaxy clusters and filaments. “So it all sort of comes together,” Pogosian said, “if this turns out to be right.”

    See the full article here .


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  • richardmitnick 10:00 am on July 4, 2020 Permalink | Reply
    Tags: "Peering under galactic dust study reveals radiation at center of Milky Way", (WHAM)-Wisconsin H-Alpha Mapper telescope, , , Basic Research, , LINER-type galaxy,   

    From University of Wisconsin Madison: “Peering under galactic dust, study reveals radiation at center of Milky Way” 

    From University of Wisconsin Madison

    July 3, 2020
    Eric Hamilton

    Thanks to 20 years of homegrown galactic data, astronomers at the University of Wisconsin–Madison, UW–Whitewater and Embry-Riddle Aeronautical University have finally figured out just how much energy permeates the center of the Milky Way.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    The researchers say it could one day help astronomers track down where all that energy comes from. Understanding the source of the radiation could help explain not only the nature of the Milky Way, but the countless others that resemble it.

    Writing in the journal Science Advances on July 3, UW–Madison astronomy graduate student Dhanesh Krishnarao, UW–Whitewater Professor of Astronomy Bob Benjamin and Embry-Riddle Professor of Astronomy Matt Haffner report that the Milky Way’s center occupies a middle ground of galactic radiation levels known as a LINER-type galaxy.

    The researchers used the Wisconsin H-alpha Mapper, or WHAM, telescope to measure the emission of visible light from hydrogen in a disk-shaped region tilted beneath the plane of the Milky Way, highlighted in red. Dhanesh Krishnarao/Milky Way image by Axel Mellinger.

    In many ways, the Milky Way is among the most mysterious galaxies. Although we call it home, our view of the galaxy’s dense and active center is blocked by immense clouds of dust. However, working with the Wisconsin H-Alpha Mapper telescope, (WHAM), the researchers recently stumbled onto a fortuitous path toward understanding more about the energy at the center of the Milky Way.

    U Wisconsin WHAM Wisconsin Alpha Mapper telescope

    A few years ago, Benjamin was reviewing two decades worth of information gathered by WHAM about ionized hydrogen gas across the entire galaxy. Gas that’s ionized has absorbed enough energy to strip it of its electrons, and it gives off a red hue that telescopes can capture.

    He noticed an anomaly. In a bubble protruding beneath the dark dust toward the center of the galaxy, some of the gas was heading in the direction of Earth when that shouldn’t have been possible.

    “That didn’t make any sense because galactic rotation can’t produce that,” says Benjamin.

    The errant gas not only begged to be explained, but also offered an opportunity to understand the energy permeating the galactic center. Because the bubble of gas extended away from the heaviest clouds of dust, it allowed the researchers to see further toward the galactic center than is normally possible. Measuring how much of the gas was ionized would tell them how much radiation existed in the galactic center.

    So, Krishnarao set WHAM’s sights squarely on this protruding bubble to gather additional information on the ionized nitrogen, oxygen and hydrogen that resided there. He then turned his attention to a 40-year-old model of galactic gas that might help him explain his data.

    The model attempted to explain the extent of the neutral, or non-ionized, gas within the protruding bubble. Krishnarao first refined the model’s prediction of the shape of the gas, and then he adapted it to account for ionized gas as well.

    By combining the raw data from WHAM with the updated model, the astronomers were able to estimate the three-dimensional size, location and composition of ionized gas. The results showed that there was a large amount of ionized gas permeating the center of the Milky Way, which had never been seen before.

    “It was surprising to us because we’d only known about the neutral gas before,” Benjamin says. “But compared to other galaxies we’ve observed, the amount of ionized gas looked pretty normal.”

    Krishnarao’s team also noticed that the composition of the ionized gas — and thus the nature of the radiation that produces it — changes as you move away from the center of the galaxy.

    “That’s telling us that what’s happening at the very nucleus of our galaxy, really close to that central supermassive black hole, is different than what’s happening a little bit farther away,” says Krishnarao.

    Study reveals radiation at center of Milky Way
    Working with the Wisconsin H-Alpha Mapper telescope, (WHAM), the researchers recently stumbled onto a fortuitous path toward understanding more about the energy at the center of the Milky Way.

    The overall radiation at the galactic center places it into a category known as LINER. About one-third of all galaxies we can see are LINERs. It’s a catch-all term for galaxies with more radiation at the center relative to galaxies dominated by star formation, but less radiation than that produced by the galactic engines of mass-eating supermassive black holes known as active galactic nuclei. Not too much, and not too little, the Milky Way plays the role of the Goldilocks of galactic radiation.

    The researchers were also able to explain the gas’s unusual trajectory. The three-dimensional location of the gas showed that it was on an orbit headed toward Earth due to the elliptical rotation of the bar of the Milky Way.

    However, the source of radiation in LINER galaxies remains a mystery. Now that it’s known the Milky Way falls into that category, it offers a chance for up-close observations of radiation sources to try and pin down just what creates all that energy.

    Krishnarao is now studying whether barred spiral galaxies like our own are prone to being LINERs, and what could explain that association. The answers will help make sense of the Milky Way’s sister spiral galaxies, spread throughout the universe, and give us a deeper understanding of our galactic home.

    This work was supported in part by the National Science Foundation for WHAM development, operations and science activities including grants AST-0607512, AST-1108911, and AST-1714472/1715623; NASA grant NNX17AJ27G; and IDEX Paris-Saclay grant ANR-11-IDEX-0003-02.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

  • richardmitnick 1:25 pm on July 3, 2020 Permalink | Reply
    Tags: "First asteroid found within Venus’s orbit could be a clue to missing ‘mantle’ asteroids", , , Basic Research, ,   

    From Science Magazine: “First asteroid found within Venus’s orbit could be a clue to missing ‘mantle’ asteroids” 

    From Science Magazine

    Jul. 1, 2020
    Nola Redd

    The first Vatira, 2020 AV2, may point to asteroids resembling Earth’s mantle. Equinox Graphics/Science Source.

    Earlier this year, astronomers discovered an oddball asteroid inside the orbit of Venus—the first member of a predicted flock near the Sun. No bigger than a small mountain, the asteroid has now gained another distinction: It appears to be rich in the mineral olivine, which makes up much of Earth’s deep rock. Some astronomers think that is a clue to a larger set of asteroids, never properly accounted for, that was forged early in the formation of the Solar System.

    “It’s improbable that we look at this new population and an olivine-dominated object is the first type we see,” says Francesca DeMeo, an asteroid hunter at the Massachusetts Institute of Technology who was not part of the discovery team. “That’s what makes this a cool result.”

    Most of the nearly 1 million known asteroids lie in a belt beyond Mars, shepherded by Jupiter’s gravity. Just 23 Atira asteroids—named after a Native American goddess—have been found within Earth’s orbit, because interactions with the inner planets upset their orbits and eventually send them crashing into a planet or the Sun. But astronomers have long suspected the existence of an even smaller population of short-lived objects within the orbit of Venus, informally called Vatiras.

    They’re hard to spot. Like Venus, these objects would appear low on the horizon at dawn and dusk, barely visible against the glare of the Sun. Yet on 4 January, astronomers using a small survey telescope at the Palomar Observatory in California found one: 2020 AV2, a 1.5-kilometer-wide asteroid in a 151-day orbit around the Sun.

    To find out what 2020 AV2 is made of, Marcel Popescu, a researcher at the Astronomical Institute of the Romanian Academy, and his colleagues used telescopes on the Canary Islands to prise apart the asteroid’s reflected light, revealing absorption lines that are clues to chemical composition. They identified the fingerprint of olivine, a major mineral in the mantle of Earth and other planets, Popescu and his colleagues reported on 18 June in the Monthly Notices of the Royal Astronomical Society. “We’re not able to say definitely that it is an olivine-dominated asteroid, but olivine is abundant at its surface,” Popescu says.

    Separate studies of the object’s trajectory by Carlos and Raul de la Fuente Marcos, brothers who are researchers at the Complutense University of Madrid and were also co-authors on the discovery paper, revealed that 2020 AV2 likely originated in the main asteroid belt. Gravitational interactions with Jupiter would have flung it, and potentially some neighbors, toward Earth. There, a gravitational dance with the terrestrial planets probably nudged its orbit inside Venus over millions of years. That path, along with its small size, suggests to Popescu a way to solve a decades-old “missing mantle” puzzle for asteroids.

    The same separation into core, mantle, and crust that took place in rocky planets soon after they formed is also thought to have occurred in small planetary embryos 4.56 billion years ago. Heat from the decay of short-lived radioactive aluminum-26 caused iron and nickel-rich rocks in these embryos to sink into their cores while olivine-rich rocks rose into a mantle and the lightest minerals formed a thin crust. Subsequent collisions shattered these embryos into asteroids.

    Yet although plenty of metal-rich asteroids have been identified, the olivine-rich mantle asteroids are few and far between. “When you fragment differentiated bodies, you should get a lot of mantle out,” says Marco Delbo, of the Côte d’Azur Observatory in Nice, France. “But we don’t see many of these asteroids in the main belt.” In 2019, DeMeo reported finding 21 new olivine-rich asteroids in the main belt, bringing the total to 36. But that’s still not enough to account for all the missing mantle material.

    One idea is that astronomers just can’t see small enough. The olivine-rich asteroids are more easily pulverized than their harder iron cousins, suggesting most of the missing mantle sits in small pieces—a “battered-to-bits” model first proposed in the 1990s. 2020 AV2 could be a far-flung representative of a hidden population of even smaller, olivine-rich objects in the main belt that are hard to see because they’re farther from Earth, Popescu says. “As soon as we are able to observe smaller objects, it is expected that we will find these objects,” he says.

    Other researchers are skeptical. In her 2019 study, DeMeo searched for olivine-rich objects nearly as small as 2020 AV2 and found only a handful—not enough to hint at a hidden smaller population. Moreover, she says, the Vatiras are likely to hail from the inner part of the asteroid belt, where olivine-rich bodies are slightly more common. That makes 2020 AV2’s composition a little less surprising, she says. The discovery “definitely adds to our body of knowledge,” she says. “I just don’t think it clinches any final conclusions.”

    Meanwhile, Popescu wants to observe the asteroid again and look for signs of another mineral, pyroxine, which would firm up its identity as a “mantle” asteroid. And he hopes ongoing surveys will spot more close-in asteroids. “It’s a very interesting object, a peculiar one—the first of its kind,” Popescu says. “I want to see if there will be others.”

    *Correction, 2 July, 4 p.m.: A previous version of the story misstated the number of Atira asteroids and the affiliation for Carlos and Raul de la Fuente Marcos.

    See the full article here .


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    Stem Education Coalition

  • richardmitnick 12:55 pm on July 3, 2020 Permalink | Reply
    Tags: "Thorne-Żytkow Objects: When a Supergiant Star Swallows a Dead Star", , , Basic Research, Both theory and observation still have a long way to go., , , HV 2112, HV 2112: A Strange Star Disputed, Thorne-Żytkow Object Discovered in 2014   

    From Discover Magazine: “Thorne-Żytkow Objects: When a Supergiant Star Swallows a Dead Star” 


    From Discover Magazine

    July 3, 2020
    Eric Betz

    One of the universe’s strangest stars is thought to form when a neutron star gets sucked into a red supergiant. But despite 45 years of searching, astronomers still aren’t sure they’ve ever found one.

    A Thorne-Żytkow object is a theoretical type of hybrid star created when a dense neutron star is swallowed by a puffy red supergiant star, as seen in this artist’s concept. (Credit: Astronomy Magazine)

    Nearly half a century ago, physicist Kip Thorne (now a Nobel laureate) and astronomer Anna Żytkow suggested a strange, Russian-nesting-doll-type star might be hiding in the cosmos, just waiting to be found by those who knew how to seek it. Astronomers named these theoretical stellar hybrids Thorne-Żytkow objects.

    The possible existence of Thorne-Żytkow objects came to light when their namesake researchers ran early computer simulations. When they did, they found that a neutron star — a tiny, ultra-dense stellar remnant left behind when a star goes supernova — could be gobbled up by a red supergiant star.

    According to the simulations, if the “Twins” (in the Danny DeVito-Arnold Schwarzenegger sense) get too close to one another, instead of one star getting ejected, the two stars can merge together. The city-sized, solar-mass neutron star would carry on living inside its much larger host, almost like a cosmic parasite.

    But even if physics really allows for such stars to exist, finding them will be hard.

    In a study published in 1975 in The Astrophysical Journal, Thorne and Żytkow suggested these stars would look almost identical to red supergiants like Betelgeuse in the constellation Orion. Supergiant stars are relatively common and are some of the youngest and largest stars in the universe. Thorne-Żytkow objects (TZOs) would look very similar to red supergiants, but are suspected to survive up to 10 times longer.

    Ordinary red supergiants, like other stars, are powered by nuclear fusion in their cores. So when that energy runs out, their uncontested gravity causes them to implode before erupting as a supernova. But TZOs can live such long lives because they do not rely on sustained nuclear fusion in their cores to avoid collapse. Instead, a TZO’s neutron star core, which is already extremely compressed, largely prevents the rapid and uncontested gravitational collapse of the surrounding supergiant layers.

    Astronomers have two different theories for how TZOs form — and they both depend on the initial objects starting their lives as two gigantic stars in a close binary system. In one theory, the bigger of the two stars would explode as a supernova first, leaving behind a neutron star. But over time, the remaining supergiant would continue to balloon outward, growing until it fully swallowed the nearby neutron star remnant.

    Another possibility for the formation of TZOs is that when one star explodes as an asymmetric supernova, its remnant core could get a powerful “kick.” That could potentially fire the neutron star into the belly of the remaining red giant.

    A candidate Thorne-Zytkow object (yellow box) shines among the stars of the Small Magellanic Cloud. (Credit: ESA/Hubble)

    Thorne-Żytkow Object Discovered

    But no matter how they form, astronomers in 2014 announced they may have discovered the first Thorne-Żytkow object. The star was hiding some 200,000 light-years away in the Small Magellanic Cloud, a dwarf galaxy that orbits the Milky Way.


    Small Magellanic Cloud. 10 November 2005. NASA/ESA Hubble and Digitized Sky Survey 2

    It was found by astronomer Emily Levesque, now at the University of Washington, with the help of her team of researchers. To find the suspected TZO, Levesque’s group used New Mexico’s Apache Point Observatory to study two dozen red supergiant stars in the Milky Way, as well as one of the Magellan Telescopes in Chile to study another group of supergiants in the Small Magellanic Cloud.

    Apache Point Observatory, near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft)

    Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile. over 2,500 m (8,200 ft) high

    Upon reviewing the data, one star in particular stood out. The system, dubbed HV 2112, was initially cataloged as variable in 1908 by pioneering astronomer Henrietta Swan Leavitt. At the time, though, astronomers thought it was a red supergiant living out its dying days before going supernova.

    However, more than 100 years after Leavitt first noted the strange object, Levesque and her team’s analysis revealed unusual chemical signatures that they thought could be the tell-tale signs of a mythical Thorne-Żytkow object. The researchers saw excess amounts of lithium, calcium and other elements, which they could only explain through the unique nuclear reactions that would occur inside a TZO.

    But they couldn’t be completely sure; HV 2112 also seemed to have other strange chemical fingerprints that they didn’t expect to see. Based on these remaining mysteries, the team suggests that either theoretical models haven’t fully appreciated the nuances of Thorne-Żytkow objects, or HV 2112 simply wasn’t a TZO in the first place.

    HV 2112: A Strange Star Disputed

    The bizarre nature of the find sparked headlines at the time. But for astronomers, it was also an important discovery because it offered evidence for stars powered by processes beyond nuclear fusion.

    But four years later, in 2018, another group of astronomers pushed “pause” on this unique find [MNRAS]. They’d done their own analysis of HV 2112 and compared it to similar stars, but didn’t find the same levels of excess calcium or other elements spotted by Levesque’s team. The new analysis did show a surplus of lithium, but, other than that, the results suggested this star was basically an ordinary red supergiant.

    Though the team might have dashed HV 2112’s dreams of being different, they did offer up the hope a replacement candidate. They found another possible Thorne-Żytkow object, cataloged as HV 11417, which did sport some of tell-tale signs that astronomers predicted the objects should have.

    One thing the two teams do agree on is that when it comes to Thorne-Żytkow objects, both theory and observation still have a long way to go.

    See the full article here .


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  • richardmitnick 8:56 am on July 3, 2020 Permalink | Reply
    Tags: "Pluto has likely maintained an underground liquid ocean for billions of years", According to S. Alan Stern “We’re going to need an orbiter to clinch the case [for Pluto’s ocean]., , , , Basic Research, , , , Oceans are ubiquitous. Most of them are in the outer solar system. And they could be abodes for life.   

    From Astronomy Magazine: “Pluto has likely maintained an underground liquid ocean for billions of years” 

    From Astronomy Magazine

    June 23, 2020
    Eric Betz

    The discovery hints that subsurface oceans are common in the outer solar system, which is good news for the those seeking extraterrestrial life.

    Pluto as imaged by the New Horizons mission. NASA/JHU-APL/SwRI.

    When early Earth was still a molten mass with a surface swimming in liquid magma, Pluto and its underground ocean were just forming. And for the billions of years since, liquid plutonian water has remained in the distant solar system, providing a potential abode for life. At least, that’s the conclusion of a new study published June 22 in the journal Nature Geoscience.

    The study rewrites scientists’ theories about the early history of Pluto and suggests that other liquid oceans — once thought to be unique to Earth — are common on dwarf planets across the outer solar system.

    “Oceans are ubiquitous. Most of them are in the outer solar system. And they could be abodes for life,” says S. Alan Stern, an astronomer at the Southwest Research Institute and head of NASA’s New Horizons mission. “This is a fundamental sea change in the way we view the solar system.”

    Just 15 minutes after closest approach, New Horizons captured a near-sunset view of Pluto’s rugged terrain and hazy, layered atmosphere. The scene is 230 miles across. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

    NASA/New Horizons spacecraft

    Pluto’s buried ocean

    When the New Horizons spacecraft made its flyby of Pluto in 2015, it revealed a surface geology so active and complex that scientists suspected there may have once been an ocean buried miles beneath Pluto’s thick crust of ice. Those suspicions have grown closer to presumptions in recent years. And now, most planetary scientists agree that, even today, Pluto has a global liquid ocean under its surface.

    But how does a world smaller than Earth’s moon harbor on ocean? And how did it manage to keep it from freezing over the course of billions of years?

    With the new study, scientists think they finally have an answer to these questions.

    Until now, astronomers assumed that Pluto formed out of cold material glomming together very slowly. As a dusty disk of debris coalesced around our Sun, the dwarf planet would have gradually clumped together out of bits of rock and ice. Once large enough, Pluto’s internal heat would have melted some of its ice, creating a subsurface ocean. That story works well, astronomers say, as Pluto’s underground ocean is explained simply by the decay of radioactive elements.

    But the team behind this latest research wanted to test that theory anyway. They wanted to find out whether Pluto started off hot instead, and formed through a series of massive impacts much like early Earth.

    “We understand this picture fairly well from the early inner solar system through meteorites and other things,” says lead study author Carver Bierson, a graduate student at the University of California, Santa Cruz. However, he adds, “we actually don’t have much of a picture for the outer solar system.”

    Putting Pluto in the freezer

    As it turns out, there is a way to tell whether Pluto formed hot or cold by simply observing the dwarf planet’s surface. It relates to the straightforward fact that water expands as it freezes and compresses when it melts.

    “If you take a glass of water and put it in the freezer, that glass is going to break overnight because when the water freezes, it expands,” Stern says. “The same thing is true on Pluto.”

    When water freezes, the molecules inside vibrate less and form a crystalline structure that leaves ice less dense. That’s why ice cubes float in your glass, and why this solid water also expands.

    So if Pluto started hot and then slowly froze, its surface should have expanded, leaving evidence of geologic features formed through expansion. But if Pluto had a cold start, the dwarf planet’s surface should show evidence of compression going back into the world’s distant history.

    To probe which of these two scenarios fits the evidence, the team took a closer look at New Horizons’ data, searching for signs of either expansion or compression. They were surprised by what they found.

    “We see terrains on Pluto that look to be very old, roughly the age of the solar system, and we don’t see evidence of that compression,” Bierson says. That suggests a hot start.

    One such example comes from craters. Impacts on an icy world typically form neat circles. But over time, Pluto’s craters have all been stretched out, even ones that sit in the oldest terrains. However, none of them are compressed.

    There are other lines of evidence, too.

    Bierson went on to model Pluto’s early formation using a hot-start scenario. He found that if Pluto formed through a rapid succession of large impacts, the heat from those explosions would continue to build up. This would maintain Pluto’s internal ocean in a liquid state. But for that to have happened, Bierson says, the world must have formed in some 30,000 years — if not less.

    Still, this idea actually matches up well with other recent models of the early evolution of the Kuiper Belt, a region of icy objects and dwarf planets beyond Neptune. Studies suggest that smaller Kuiper Belt objects could have formed in just a few hundred or thousand years.

    “It’s kind of nice that the geology is telling us this,” he says. “People trying to understand the [Kuiper Belt] dynamics are also coming to this conclusion.” The conclusion of a hot start for Pluto “is a weird, surprising answer,” he adds.

    Pluto’s suspected sizzling start also carries major implications for the small world’s neighbors, like Eris, Makemake, and Haumea. If Pluto formed hot and fast, other dwarf planets likely did as well. Taken together with new knowledge of the icy ocean moons around the gas giant planets, astronomers are overturning the old notion of Earth as the sole ocean world in our solar system. Instead, it could be that the outer solar system is surprisingly rich in liquid water.

    “Dozens of worlds in the inner and outer solar systems could have oceans,” Stern says. “It’s one of the most profound discoveries in planetary science in the Space Age.”

    These alien worlds might not seem like a likely place for life to emerge. Pluto sits an average of some 4 billion miles from the Sun (about 40 times farther away than Earth), where very little light reaches the dwarf planet’s surface, letting temperatures drop to around –400 degrees Fahrenheit.

    But below Pluto’s frigid surface, in the relatively warm subsurface ocean, life would be protected from radiation and asteroid impacts.

    “The interesting thing about oceans on the inside is that, in some ways, they’re much safer havens for life,” Stern says. “You’re protected from impacts like the ones that killed the dinosaurs. If the Sun releases flares or a supernova goes off, then you’re safe from that.”

    How Pluto got its heart

    This latest find adds to a growing body of evidence that suggests Pluto has long harbored an active ocean. And another piece of that puzzle only arrived earlier this year.

    Pluto’s icy “heart” is the world’s most recognizable feature. The region is shaped by what looks like a giant impact basin the size of Texas. The heart’s left lobe consists of a 600-mile-wide (1,000 kilometers) ice plain called Sputnik Planitia, which is the largest glacier in the solar system. When New Horizons first brought this feature into clear focus, astronomers thought it must have formed when another large object smashed into Pluto in its past.

    However, the exact location of the basin is suspicious. It sits on precisely the opposite side of world from Pluto’s large moon, Charon. Because an impactor could have hit Pluto anywhere, Stern says, “the idea that this just happened to strike opposite to Charon could be coincidence, but it seems to me too much to believe that it happened entirely by chance.”

    Instead, he thinks the alignment between Charon and Sputnik Planitia could be due to a complicated process called polar wander. Based on models, scientists think the massive glacier could have easily slid along the dwarf planet’s surface until it sat directly opposite from Charon. But that model only makes sense if Pluto has an ocean.

    Still, Stern admits the evidence they have for the existence of Pluto’s ocean is indirect. “We have several lines of circumstantial evidence, but you usually can’t convict in a court of law on circumstantial evidence,” he says.

    And that’s why Stern and a team of researchers are pushing for a Pluto orbiter that would not just return to the dwarf planet, but actually orbit it. New Horizons only got a quick look at Pluto during its brief flyby. And though groundbreaking, the probe only captured high-quality images of 40 percent of the distant world. And another 40 percent of the surface was too dark for New Horizons to even make out anything at all. A Pluto orbiter, on the other hand, could be built with radar and laser instruments that don’t need visible light to see the surface.

    According to Stern, “We’re going to need an orbiter to clinch the case [for Pluto’s ocean], just like it took Cassini to clinch the case for an ocean at Enceladus and Galileo to clinch the case for an ocean at Europa.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Astronomy is a magazine about the science and hobby of astronomy. Based near Milwaukee in Waukesha, Wisconsin, it is produced by Kalmbach Publishing. Astronomy’s readers include those interested in astronomy and those who want to know about sky events, observing techniques, astrophotography, and amateur astronomy in general.

    Astronomy was founded in 1973 by Stephen A. Walther, a graduate of the University of Wisconsin–Stevens Point and amateur astronomer. The first issue, August 1973, consisted of 48 pages with five feature articles and information about what to see in the sky that month. Issues contained astrophotos and illustrations created by astronomical artists. Walther had worked part time as a planetarium lecturer at the University of Wisconsin–Milwaukee and developed an interest in photographing constellations at an early age. Although even in childhood he was interested to obsession in Astronomy, he did so poorly in mathematics that his mother despaired that he would ever be able to earn a living. However he graduated in Journalism from the University of Wisconsin Stevens Point, and as a senior class project he created a business plan for a magazine for amateur astronomers. With the help of his brother David, he was able to bring the magazine to fruition. He died in 1977.

  • richardmitnick 7:49 am on July 3, 2020 Permalink | Reply
    Tags: "Europeans Decide on Particle Strategy", , Basic Research, , , , , , ,   

    From “Physics”: “Europeans Decide on Particle Strategy” 

    About Physics

    From “Physics”

    July 2, 2020
    Michael Schirber

    The CERN Council approved a strategy update that prioritizes a 100-km circular collider, while still developing other options for future particle physics projects.

    A map depicting where the 100-km-long Future Circular Collider could be built in relation to CERN’s existing accelerator infrastructure.

    European particle physicists have updated their strategy for the coming decades. Beyond current commitments, the community advocates pursuing a new facility at the CERN site outside Geneva—a circular collider with a circumference of 100 kilometers. Such a machine could serve a dual purpose: to act initially as a “Higgs factory” where electrons and positrons smash together at energies up to 350 GeV, and to later scope out the high-energy frontier by colliding protons at up to 100-TeV energies. The feasibility of this so-called Future Circular Collider (FCC) is still an open question, which is why the strategy also calls for continued research and development into accelerator technology, such as plasma acceleration and muon colliders.

    Following a two-year-long process, the European Strategy for Particle Physics Update was unanimously endorsed on June 19 by the CERN Council, which is the governing body of the CERN facility. The Update outlines a number of current and future priorities. In the near-term, the main initiatives for Europe are the high-luminosity upgrade of CERN’s Large Hadron Collider (LHC) and continuing support of international neutrino experiments, such as the forthcoming Deep Underground Neutrino Experiment (DUNE) in the US.

    FNAL LBNF/DUNE from FNAL to SURF, Lead, South Dakota, USA

    But beyond that, many questions remain. “CERN needs to have a project for after the LHC,” says Halina Abramowicz, chair of the European Strategy Group, from Tel Aviv University in Israel.

    The main objective of any post-LHC endeavor will be to look for new particles or phenomena that go beyond the standard model of particle physics.

    Standard Model of Particle Physics, Quantum Diaries

    Physicists are still in the dark as to what this “new physics” will be, so the best way forward is to study the Higgs boson with greater precision, Abramowicz says. The Higgs is unique in that it should interact with all particles, even ones that physicists haven’t detected yet. “The Higgs does not differentiate: if there is something out there, it will couple to it,” Abramowicz explains.

    CERN CMS Higgs Event May 27, 2012

    CERN ATLAS Higgs Event June 12, 2012

    Precision measurements of Higgs physics can be done with an electron-positron collider, but the exact design of such a Higgs factory is still undecided. The International Linear Collider (ILC) is one option, but the proposed host, Japan, has not yet committed to the project.

    ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan

    Researchers at CERN have been developing the Compact Linear Collider (CLIC), which could potentially smash electrons and positrons at energies as high as 3 TeV.

    CERN CLIC collider

    CERN CLIC Collider annotated

    However, uncertainty about the energy where new physics might appear led the Strategy Group to decide on the FCC concept as the best option to pursue. The large ring-shaped tunnel could accommodate a Higgs factory and then later shift to colliding protons at energies 7 times greater than those of the LHC.

    But pursuing the FCC won’t be straightforward. “The FCC would be the machine that physicists most want,” says Ursula Bassler, the president of the CERN Council. “However, we do not know if it’s technically and financially feasible.” Preliminary estimates suggest that such a collider would cost around 20 billion dollars, so involvement by countries outside of Europe will likely be necessary. “The scope and the science and technology challenges of such a Higgs factory would require a long-term global collaboration of the kind that the US is currently engaged in with the LHC and DUNE,” says Fermilab’s Marcela Carena, who was the US representative for the strategy’s Physics Preparatory Group.

    One possible wrinkle is that Chinese physicists have proposed the Circular Electron Positron Collider (CEPC), whose design is similar in size and scope to that of the FCC.

    China Circular Electron Positron Collider (CEPC) map. It would be housed in a hundred-kilometer- (62-mile-) round tunnel at one of three potential sites. The documents work under the assumption that the collider will be located near Qinhuangdao City around 200 miles east of Beijing.

    “I think there is a competition between China and Europe,” Bassler says. “However, there’s also a lot of collaboration going on.” As long as neither side has committed to a project, she thinks it can help spur innovation to have different groups working on the same research track.

    Abramowicz stresses that the FCC is not the final word. By continuing research and development into accelerator technology, she believes particle physicists can remain flexible in the face of new developments in the scientific and political worlds. “From the input we received, it’s clear that particle physicists are very excited about the FCC, but they do realize that it’s not a given. So they want to make sure that we have alternatives.”

    Bassler is happy the process is complete. “In the beginning, every time I met a physicist at CERN cafeteria, I heard a different strategy.” She feels the community has now converged on a common roadmap, in which the first step will be a thorough feasibility study of the FCC concept. At the same time, US particle physicists will be working on “Snowmass”—a community exercise led by the American Physical Society, which aims to draw up a particle physics vision for 2021. “The timing of the European Strategy Update fits well with the launch of the Snowmass process,” Carena says.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

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