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  • richardmitnick 10:15 am on August 28, 2019 Permalink | Reply
    Tags: , , , , , Milky Way   

    From European Space Agency: “Gaia untangles the starry strings of the Milky Way” 

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    From European Space Agency

    28 August 2019

    Marina Kounkel
    Western Washington University, USA
    Email: marina.kounkel@wwu.edu

    Kevin Covey
    Western Washington University, USA
    Email: kevin.covey@wwu.edu

    Timo Prusti
    Gaia Project Scientist
    European Space Agency
    Email: timo.prusti@esa.int


    Gaia tracing starry strings in the Milky Way.

    Rather than leaving home young, as expected, stellar ‘siblings’ prefer to stick together in long-lasting, string-like groups, finds a new study of data from ESA’s Gaia spacecraft.

    ESA/GAIA satellite

    Exploring the distribution and past history of the starry residents of our galaxy is especially challenging as it requires astronomers to determine the ages of stars. This is not at all trivial, as ‘average’ stars of a similar mass but different ages look very much alike.

    To figure out when a star formed, astronomers must instead look at populations of stars thought to have formed at the same time – but knowing which stars are siblings poses a further challenge, since stars do not necessarily hang out long in the stellar cradles where they formed.

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    This diagram shows a face-on view of stellar ‘families’ – clusters (dots) and co-moving groups (thick lines) of stars – within about 3000 light-years from the Sun, which is located at the centre of the image. The diagram is based on data from the second data release of ESA’s Gaia mission. Each family is identified with a different colour and comprises a population of stars that formed at the same time. Purple hues represent the oldest stellar populations, which formed around 1 billion years ago; blue and green hues represent intermediate ages, with stars that formed hundreds of millions of years ago; orange and red hues show the youngest stellar populations, which formed less than a hundred million years ago. Thin lines show the predicted velocities of each group of stars over the next 5 million years, based on Gaia’s measurements. The lack of structures at the centre is an artefact of the method used to trace individual populations, not due to a physical bubble. A recent study using data from Gaia’s second data release uncovered nearly 2000 previously unidentified clusters and co-moving groups of stars and determined the ages for hundreds of thousands of stars, making it possible to track stellar ‘siblings’ and uncover their surprising arrangements. The study revealed that the most massive among these familial groups of stars may keep moving together through the galaxy in long, string-like configurations for billions of years after their birth.

    “To identify which stars formed together, we look for stars moving similarly, as all of the stars that formed within the same cloud or cluster would move in a similar way,” says Marina Kounkel of Western Washington University, USA, and lead author of the new study [The Astronomical Journal].

    “We knew of a few such ‘co-moving’ star groups near the Solar System, but Gaia enabled us to explore the Milky Way in great detail out to far greater distances, revealing many more of these groups.”

    Marina used data from Gaia’s second release to trace the structure and star formation activity of a large patch of space surrounding the Solar System, and to explore how this changed over time. This data release, provided in April 2018, lists the motions and positions of over one billion stars with unprecedented precision.

    The analysis of the Gaia data, relying on a machine learning algorithm, uncovered nearly 2000 previously unidentified clusters and co-moving groups of stars up to about 3000 light years from us – roughly 750 times the distance to Proxima Centauri, the nearest star to the Sun. The study also determined the ages for hundreds of thousands of stars, making it possible to track stellar ‘families’ and uncover their surprising arrangements.

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    Stellar families in Gaia’s sky

    “Around half of these stars are found in long, string-like configurations that mirror features present within their giant birth clouds,” adds Marina.

    “We generally thought young stars would leave their birth sites just a few million years after they form, completely losing ties with their original family – but it seems that stars can stay close to their siblings for as long as a few billion years.”

    The strings also appear to be oriented in particular ways with respect to our galaxy’s spiral arms – something that depends upon the ages of the stars within a string. This is especially evident for the youngest strings, comprising stars younger than 100 million years, which tend to be oriented at right angles to the spiral arm nearest to our Solar System.

    3
    Stellar groups and strings in the Milky Way – edge-on view

    The astronomers suspect that the older strings of stars must have been perpendicular to the spiral arms that existed when these stars formed, which have now been reshuffled over the past billion years.

    “The proximity and orientation of the youngest strings to the Milky Way’s present-day spiral arms shows that older strings are an important ‘fossil record’ of our galaxy’s spiral structure,” says co-author Kevin Covey, also of Western Washington University, USA.

    “The nature of spiral arms is still debated, with the verdict on them being stable or dynamic structures not settled yet. Studying these older strings will help us understand if the arms are mostly static, or if they move or dissipate and re-form over the course of a few hundred million years – roughly the time it takes for the Sun to orbit around the galactic centre a couple of times.”

    Gaia was launched in 2013, and is on a mission to chart a three-dimensional map of our galaxy, pinpointing the locations, motions, and dynamics of roughly one percent of the stars within the Milky Way, along with additional information about many of these stars. Further Gaia releases, including more and increasingly precise data, are planned for the coming decade, providing astronomers with the information they need to unfold the star-formation history of our galaxy.

    “Gaia is a truly ground-breaking mission that is revealing the history of the Milky Way – and its constituent stars – like never before,” adds Timo Prusti, Gaia project scientist at ESA.

    “As we will determine the ages for a larger number of stars distributed throughout our galaxy, not just those residing in compact clusters, we’ll be in an even better position to analyse how these stars have evolved over time.”

    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 11:37 am on July 24, 2019 Permalink | Reply
    Tags: "Production Sites of Stars are Rare", , , , , High-density gas- the material for stars- accounts for only 3% of the total mass of gas distributed in the Milky Way, Milky Way, , Nobeyama Radio Obeservatory (NRO) 45-m telescope   

    From National Astronomical Observatory of Japan: “Production Sites of Stars are Rare” 

    NAOJ

    From National Astronomical Observatory of Japan

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    Distribution of gas clouds obtained from the FUGIN project. The high-density gas (right) is detected only in small parts of the low-density gas (left). (Credit: NAOJ)

    Astronomers using the Nobeyama Radio Obeservatory (NRO) 45-m telescope [below] found that high-density gas, the material for stars, accounts for only 3% of the total mass of gas distributed in the Milky Way. This result provides key information for understanding the unexpectedly low production rate of stars.

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

    Stars are born in gas clouds. The high-density gas pockets form in the extended, low-density gas clouds, and stars form in the very dense gas cores which evolve within the high-density gas. However, observations of distant galaxies detected 1000 times fewer stars than the production value expected from the total amount of low-density gas. To interpret the discrepancy, observations which detect both of the high-density and low-density gas with high-spatial resolution and wide area coverage were needed. However, such observations are difficult, because the high-density gas structures are dozens of times smaller than the low-density gas structures.

    The Milky Way survey project “FUGIN” conducted using the NRO 45-m telescope and the multi-beam receiver FOREST overcame these difficulties. Kazufumi Torii, a project assistant professor at NAOJ, and his team analyzed the big data obtained in the FUGIN project, and measured the accurate masses of the low-density and high-density gas for a large span of 20,000 light-years along the Milky Way. They revealed for the first time that the high-density gas accounts for only 3% of the total gas.

    These results imply the production rate of high-density gas in the low-density gas clouds is small, creating only a small number of opportunities to form stars. The researcher team will continue working on the FUGIN data to investigate the cause of inefficient formation of the high-density gas.

    Science paper PASJ

    See the full article here .

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    NAOJ

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level


    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array
    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

     
  • richardmitnick 11:18 am on March 13, 2019 Permalink | Reply
    Tags: "Streams of Stars Snaking Through the Galaxy Could Help Shine a Light on Dark Matter", Adrian Price-Whelan calls GD-1 "the Goldilocks stream" because it's in just the right place., , , At about 33000 light-years (10 kiloparsecs) GD-1 is the longest stellar stream in the galactic halo, , , Dark matter makes up the bulk of the mass in the universe but it has never been directly observed, , , Milky Way, scores of dark matter seeds are scattered through galaxies like the Milky Way, , The stellar stream known as GD-1 is a thin flow of material tucked inside the Galactic halo   

    From smithsonian.com: “Streams of Stars Snaking Through the Galaxy Could Help Shine a Light on Dark Matter” 

    smithsonian
    From smithsonian.com

    March 12, 2019
    Nola Taylor Redd

    When the Milky Way consumes another galaxy, tendrils of stellar streams survive the merger, containing clues about the universe’s mysterious unseen matter.

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    An ultraviolet image of the Andromeda galaxy, the closest major galaxy to the Milky Way, taken by NASA’s Galaxy Evolution Explorer space telescope. Like our own galaxy, Andromeda is a spiral galaxy with a flat rotating disk of stars and gas and a concentrated bulge of stars at the center. (NASA/JPL-Caltech)

    When a small galaxy strays too close to the Milky Way, the gravity from our larger galaxy reels it in. Gas and stars are ripped from the passing galaxy as it falls inward toward its doom, creating streams of material that stretch between the galactic pair. These streams continue to tear away stars until the infalling object has been completely consumed. After the merger is over, some of the only remaining signs of the devoured object are the stellar streams snaking through the Milky Way, a small sample of stars from a galaxy long gone.

    In addition to being a record of the past, one of these streams may provide the first direct evidence for small scale clusters of dark matter—the elusive material that is believed to account for 85 percent of all matter in the universe. A recent analysis of a trail of stars reveals that it interacted with a dense object in the last few hundred million years. After ruling out the most likely suspects, the researchers determined that the relatively recently made gap in the stream may have been caused by a small clump of dark matter. If confirmed, the eddies of this stellar stream could help scientists sort through the competing theories about dark matter and perhaps even close in on the characteristics of the mysterious material.

    The stellar stream known as GD-1 is a thin flow of material tucked inside the Galactic halo, the loose collection of stars and gases surrounding the disk of the Milky Way. Using data released last April from the European Space Agency’s Gaia space telescope, which is in the process of assembling the most detailed map of the Milky Way’s stars ever made, astronomers were able to use precise positional data to reconstruct the movement of the stars in GD-1.

    ESA/GAIA satellite

    Torn from a cloud of material, the stream is the last remnant of an object that was likely consumed by our galaxy in the last 300 million years—an eyeblink on astronomical timescales.

    Gaia found two small breaks in the stream, the first unambiguous observation of gaps in a stellar stream, as well as a dense collection of stars called a spur. Together, these features suggest that a small but massive object shook up the material of the stream.

    “I think this is the first direct dynamical evidence for the small-scale [structure] of dark matter,” says Adrian Price-Whelan, an astronomer at the Flatiron Institute in New York. Working with Ana Bonaca of the Harvard-Smithsonian Center for Astrophysics, Price-Whelan investigated the newfound structures in GD-1 to determine their source and presented the results earlier this year at the winter meeting of the American Astronomical Society.

    At about 33,000 light-years (10 kiloparsecs), GD-1 is the longest stellar stream in the galactic halo. While Price-Whelan and his colleagues were able to use models to show that one of the gaps formed during the generation of the stream, the other gap remained a mystery. However, along with the puzzle, Gaia also revealed a solution: the spur.

    When an object travels past or through a stellar stream, it disrupts the stars. Price-Whelan compares the disruption to a strong jet of air blowing across a stream of water. The water—or stars—plume outward along the path of the disruptor, creating a gap. Some move so fast that they escape the stream and go flying off into space, lost forever. Others are pulled back into the stream to form eddy-like features astronomers call spurs. After a few hundred million years, most spurs merge back into the stream, and only the gap remains, though some can be longer-lived.

    When it comes to spotting structures in stellar streams, Price-Whelan calls GD-1 “the Goldilocks stream” because it’s in just the right place. GD-1 is within the stars of the Milky Way, but moving in the opposite direction, making it easier for astronomers to pick out the stars in the stream from the surrounding objects. “At any given location, it’s moving differently from the way most of the other stars in that part of the sky are moving,” Price-Whelan says.

    The researchers modeled what type of objects could be responsible for the relatively newborn spur spotted in GD-1. They determined that the responsible object had to weigh in with a mass somewhere between 1 million and 100 million times the mass of the sun. Stretching only about 65 light-years (20 pc) in length, the object would have been incredibly dense. The interaction between the stream and the dense object would have likely happened within the last few hundred million years out of the 13.8-billion-year lifetime of the universe.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Dark matter isn’t the only object that could have disrupted the stellar stream. A globular cluster or dwarf galaxy swooping nearby could also have created the gap and spur. Price-Whelan and his colleagues turned their eyes toward all known such objects and calculated their orbits, finding that none came close enough to GD-1 in the last billion years to shake things up. A chance encounter with a primordial black hole could have sent the stream’s stars flying, but it would have been an extremely rare event.

    According to dark matter simulations that allow for small structures, scores of dark matter seeds are scattered through galaxies like the Milky Way. A stream like GD-1 is expected to encounter at least one such seed within the last 8 billion years, making dark matter a far more likely perturber based on encounter rates than any other object.

    Dark matter makes up the bulk of the mass in the universe, but it has never been directly observed. The two leading theories for its existence are the warm dark matter model and the Lambda cold dark matter model (ΛCDM), which is the model preferred by most scientists.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    Under ΛCDM, dark matter forms clumps that can be as large as a galaxy or as small as a soda can. Warm dark matter models suggest that the material has less massive particles and lacks the can-sized structures that the ΛCDM model suggests. Finding evidence for small scale structures of dark matter could help weed out certain models and start to narrow in on some of the characteristics of the tantalizing stuff.

    “Streams might be the only avenue that we could [use to] study the lowest mass end of what dark matter is doing,” Price-Whelan says. “If we want to be able to confirm or reject or rule out different theories of dark matter, we really need to know what’s happening at [the low] end.”

    Gaia’s data helped identify the stars of the spur, but it’s not detailed enough to compare the velocity differences between them and the stars in the stream, which could help confirm that dark matter perturbed the structure. Price-Whelan and his colleagues want to use NASA’s Hubble Space Telescope to further study the movement of the faint stars in GD-1. Although Gaia has opened the door to wide-scale examination of the movement of stars across the Milky Way, Price-Whelan says that it can’t compete with the HST when it comes to very faint stars. “You can drill much deeper when you have a dedicated telescope like Hubble,” he says.

    The differences in how the stars of the stream and spur move could help astronomers determine how much energy the perturbing object carried, as well as allow researchers to calculate its orbit. These pieces of information could be used to track down the disruptive dark matter clump and study its immediate environment.

    In addition to making a more in-depth study of GD-1, astronomers plan to apply the same techniques enabled by Gaia’s data to some of the more than 40 other streams surrounding the Milky Way. Spotting spurs and gaps in other streams and tying them to dark matter could further improve our understanding of how the mysterious substance interacts with the visible galaxy.

    After decades of puzzling over the mystery of dark matter, the gaps and spurs in stellar streams like GD-1 may finally help to reveal the secrets of the substance that makes up most of the universe. “This is one of the most exciting things that has come out of Gaia,” Price-Whelan says.

    See the full article here .

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    Smithsonian magazine and Smithsonian.com place a Smithsonian lens on the world, looking at the topics and subject matters researched, studied and exhibited by the Smithsonian Institution — science, history, art, popular culture and innovation — and chronicling them every day for our diverse readership.

     
  • richardmitnick 1:47 pm on January 4, 2019 Permalink | Reply
    Tags: , , , , , Milky Way, The Large Magellanic Cloud could hit our galaxy in two billion years’ time., The Milky Way is on a collision course with a neighbouring galaxy that could fling our Solar System into space   

    From Durham University: “Milky Way heading for catastrophic collision” 

    Durham U bloc

    From Durham University

    4 January 2019

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    Hubble Space Telescope image representing a merger between two galaxies (M51a and M51b) similar in mass to the Milky Way and the Large Magellanic Cloud. Credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team (STScI/AURA)

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Large Magellanic Cloud by by German astrophotographer Eckhard Slawik

    There’s an enemy in our midst. Quietly circling around our galaxy, it could send our Solar System hurtling out of the Milky Way and into the obscurity of interstellar space.

    Its name is the Large Magellanic Cloud (LMC), and even though it is one of the more researched satellite galaxies buzzing around our own, astrophysicists are only now seeing it for what it truly is: an unusually large cosmic threat.

    The Milky Way is on a collision course with a neighbouring galaxy that could fling our Solar System into space.

    The Large Magellanic Cloud could hit our galaxy in two billion years’ time.

    On the off chance that humans survive for another two billion years, our descendants will be in for a treat.

    If the catastrophic collision wakes up the black hole sleeping at the center of our galaxy, this dark beast will begin devouring everything in sight, growing ten times larger than it already is.

    As it feeds on surrounding gas, the stage will be set and the show will begin – what the researchers describe as a “spectacular display of cosmic fireworks.”

    “This phenomenon will generate powerful jets of high energy radiation emanating from just outside the black hole,” explains lead author Marius Cautun, a cosmologist at Durham University.

    “While this will not affect our Solar System, there is a small chance that we might not escape unscathed from the collision between the two galaxies which could knock us out of the Milky Way and into interstellar space.”

    Our galaxy is long overdue for such a collision. So far, it has managed to get by relatively unscathed in the grand scheme of things. Especially when you consider the company that it keeps.

    The Milky Way is surrounded by a group of smaller satellite galaxies, orbiting quietly around us.

    These galaxies can lead separate lives for many billions of years, but on occasion, they can find themselves sinking into the centre of their host galaxy, until at last they collide and are swallowed up completely.

    In this way, galaxies are constantly evolving and growing, but the Milky Way’s poor appetite makes it quite atypical.

    In comparison to our own galaxy, for instance, Andromeda can devour galaxies weighing nearly 30 times more.

    “We think that up to now our galaxy has had only a few mergers with very low mass galaxies,” says co-author Alis Deason, a computational cosmologist at Durham University.

    “This represents very slim pickings when compared to nearby galaxies of the same size as the Milky Way.”

    This galactic collision would happen much sooner than the predicted impact between the Milky Way and another neighbour, Andromeda, which scientists say will hit our galaxy in eight billion years.

    Andromeda Galaxy Adam Evans

    Active black hole

    The coming together with the Large Magellanic Cloud could wake up our galaxy’s dormant black hole, which would begin devouring surrounding gas and increase in size by up to ten times.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    Sgr A* from ESO VLT

    As it feeds, the now-active black hole would throw out high-energy radiation.

    While these cosmic fireworks are unlikely to affect life on Earth, researchers say there is a small chance that the initial collision could send our Solar System hurtling into space.

    Dark matter

    The Large Magellanic Cloud is the Milky Way’s brightest satellite galaxy and only entered our neighbourhood about 1.5 billion years ago. It sits about 163,000 light years from our galaxy.

    Until recently, astronomers thought that it would either orbit the Milky Way for many billions of years, or, since it moves so fast, escape from our galaxy’s gravitational pull.

    However, recent measurements indicate that the Large Magellanic Cloud has nearly twice as much dark matter than previously thought.

    Solar System

    Researchers say that since it has a larger than expected mass, the Large Magellanic Cloud is rapidly losing energy and is doomed to collide with our galaxy, which could have consequences for our Solar System.

    Lead researcher Dr Marius Cautun, a postdoctoral fellow in our Institute for Computational Cosmology, said: “There is a small chance that we might not escape unscathed from the collision between the two galaxies, which could knock us out of the Milky Way and into space.”

    Read the full research paper MNRAS.

    See the full article here .

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    Durham U campus

    Durham University is distinctive – a residential collegiate university with long traditions and modern values. We seek the highest distinction in research and scholarship and are committed to excellence in all aspects of education and transmission of knowledge. Our research and scholarship affect every continent. We are proud to be an international scholarly community which reflects the ambitions of cultures from around the world. We promote individual participation, providing a rounded education in which students, staff and alumni gain both the academic and the personal skills required to flourish.

     
  • richardmitnick 1:53 pm on December 16, 2018 Permalink | Reply
    Tags: , , , , , , Milky Way,   

    From EarthSky: “What is the Local Group?” 

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    From EarthSky

    How many galaxies are now known to lie within our Local Group of galaxies? How does our Milky Way rank, size-wise? And what about the vast superclusters beyond?

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    One view of the Local Group- a bit to constricted.The 3 largest galaxies in the Local Group are, in descending order, Messier 31 the Andromeda galaxy, the Milky Way, and Messier 33 also known as the Triangulum Galaxy

    Iconic view of the Local Group. Andrew Z. Colvin 3 March 2011

    We know where our galaxy is located, but only locally speaking. The Milky Way galaxy is one of more than 54 galaxies known as the Local Group. The three largest members of the group are our Milky Way (second-biggest), the Andromeda galaxy (biggest) and the Triangulum Galaxy. The other galaxies in the Local Group are dwarf galaxies, and they’re mostly clustered around the three larger galaxies.

    The Local Group does have a gravitational center. It’s somewhere between the Milky Way and the Andromeda Galaxy.

    The Local Group has a diameter of about 10 million light-years.

    Astronomers have also discovered that our Local Group is on the outskirts of a giant supercluster of galaxies, known as the Virgo Supercluster.

    Virgo Supercluster NASA

    Virgo Supercluster, NASA, Wikipedia

    At least 100 galaxy groups and clusters are located within the Virgo Supercluster. Its diameter is thought to be about 110 million light-years.

    The Virgo Supercluster may be part of an even-larger structure that astronomers call the Laniakea Supercluster.

    Laniakea supercluster. From Nature The Laniakea supercluster of galaxies R. Brent Tully, Hélène Courtois, Yehuda Hoffman & Daniel Pomarède at http://www.nature.com/nature/journal/v513/n7516/full/nature13674.html. Milky Way is the red dot.

    It consists of perhaps 100,000 galaxies stretched out over some 520 million light-years.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.orgin 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 12:55 pm on September 24, 2018 Permalink | Reply
    Tags: , , , , , , Milky Way,   

    From COSMOS Magazine: “A galactic near-miss set stars on an unexpected path around the Milky Way” 

    Cosmos Magazine bloc

    From COSMOS Magazine

    24 September 2018
    Ben Lewis

    A close pass from the Sagittarius dwarf galaxy sent ripples through the Milky Way that are still visible today.

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    Image Credit: R. Ibata (UBC), R. Wyse (JHU), R. Sword (IoA)

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

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    Tiny galaxy; big trouble. Gaia imaging shows the Sagittarius galaxy, circled in red. ESA/Gaia/DPAC

    ESA/GAIA satellite

    Between 300 and 900-million years ago the Sagittarius dwarf galaxy made a close pass by the Milky Way, setting millions of stars in motion, like ripples on a pond. The after-effects of that galactic near miss are still visible today, according to newly published findings.

    The unique pattern of stars left over from the event was detected by the European Space Agency’s star mapping mission, Gaia. The details are contained in a paper written by Teresa Antoja and colleagues from the Universitat de Barcelona in Spain, and published in the journal Nature.

    The movements of over six million stars in the Milky Way were tracked by Gaia to reveal that groups of them follow different courses as they orbit the galactic centre.

    In particular, the researchers found a pattern that resembled a snail shell in a graph that plotted star altitudes above or below the plane of the galaxy, measured against their velocity in the same direction. This is not to say that the stars themselves are moving in a spiral, but rather that the roughly circular orbits correlate with up-and-down motion in a pattern that has never been seen before.

    While some perturbations in densities and velocities had been seen previously, it was generally assumed that the movement of the disk’s stars is largely in dynamic equilibrium and symmetry about the galactic plane. Instead, Antoja’s team discovered something had knocked the disk askew.

    “It is a bit like throwing a stone in a pond, which displaces the water as ripples and waves,” she explains.

    Whereas water will eventually settle out after being disturbed, a star’s motion carries signatures from the change in movement. While the ripples in the distribution caused by Sagittarius passing by has evened out, the motion of the stars themselves still carry the pattern.

    “At the beginning the features were very weird to us,” says Antoja. “I was a bit shocked and I thought there could be a problem with the data because the shapes are so clear.”

    The new revelations came about because of a huge increase in quality of the Gaia data, compared to what had been captured previously. The new information provided, for the first time, a measurement of three-dimensional speeds for the stars. This allowed the study of stellar motion using the combination of position and velocity, known as “phase space”.

    “It looks like suddenly you have put the right glasses on and you see all the things that were not possible to see before,” says Antoja.

    Computer models suggest the disturbance occurred between 300 and 900 million years ago – a point in time when it’s known the Sagittarius galaxy came near ours.

    In cosmic terms, that’s not very long ago, which also came as a surprise. It was known that the Milky Way had endured some much earlier collisions – smashing into a dwarf galaxy some 10 billion years ago, for instance – but until now more recent events had not been suspected. The Gaia results have changed that view.

    See the full article here .


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  • richardmitnick 9:44 am on August 7, 2018 Permalink | Reply
    Tags: , , , , , , Milky Way   

    From EarthSky: “Dark Rift in the Milky Way” 

    1

    From EarthSky

    August 7, 2018
    Bruce McClure

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Standing under a dark sky? Look up! In August, you’ll notice a long, dark lane dividing the bright Milky Way. This Dark Rift is a place where new stars are forming.

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    Thick dust clouds block our night-time view of the Milky Way, creating what is sometimes called the Great Rift or Dark Rift. Image via NASA.

    Have you ever looked up from a dark place on a starry August evening and noticed the dark areas in the Milky Way? For centuries, skywatchers pondered this Great Rift or Dark Rift, as it’s called, but today’s astronomers know it consists of dark, obscuring dust in the disk of our Milky Way galaxy.

    How to see the Dark Rift. The Milky Way is easy to see if you have dark skies. It’s a shining band, stretching across the sky. If you want to see the Dark Rift, that’s easy, too, as long as you realize you aren’t looking for a bright object. You’re looking instead for dark lanes of dust, running the length of the starlit Milky Way band.

    1
    The Great Rift – also known as the Dark Rift – and the Milky Way pass through the Summer Triangle and above the Teapot asterism in Sagittarius.

    You will be looking south from sometime in June or July (probably) through about October – in a dark sky – and, from a Northern Hemisphere location, you’ll see the Milky Way come off the southern to southeastern horizon. Notice that the Milky Way band looks milky white. The skies aren’t really black like ink between stars in the Milky Way. You will know when you see the Dark Rift because it is as if someone took a marker and colored it darker.

    The Dark Rift begins just above the constellation Sagittarius the Archer. Follow the Milky Way up until you see a black area in the Milky Way just before you get to the constellation Cygnus, which has the shape of a cross.

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    Photo via Manish Mamtani.

    Don’t miss the Milky Way and Great Rift rise. One of the most spectacular sights is to see the Milky Way as it rises. Around 10 p.m. in June, step outside and look in the east to see the phenomena of the Great Rift and the rest of the Milky Way make its dramatic entrance as it rises into the night skies. In July and August, the Great Rift will already be up as darkness falls.

    Make sure you have your binoculars handy to scan the Milky Way. There are many interesting star-forming regions, star clusters and millions of stars that will capture your attention.

    Look in the Great Rift and imagine all the stars that will eventually reveal themselves as the molecular gas dissipates. More about that below.

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    ESA/Planck
    Shown is the interaction between interstellar dust in the Milky Way and the structure of our galaxy’s magnetic field, as detected by ESA’s Planck satellite over the entire sky. Image via ESA on Pinterest.

    ESA/Planck 2009 to 2013

    Molecular dust is the reason it is dark. Stars are formed from great clouds of gas and dust in our Milky Way galaxy and other galaxies. When we look up at the starry band of the Milky Way and see the Dark Rift, we are looking into our galaxy’s star-forming regions. The protostars (newly forming stars) are generating molecular dust that doesn’t allow light in the visual spectrum to shine through.

    However, with the advancement of telescopes that see in different light waves – such as X-rays or infrared – we now know that there’s activity in the area.

    5
    This painting shows some of the animal shapes that the Incas saw in the Dark Rift of the Milky Way. Image via Coricancha Sun Temple in Cusco/Futurism.

    Ancient cultures focused on the dark not the light areas. You know those paintings where if you look at the light areas you see one thing, but in the dark areas you see something else?

    The Dark Rift is a bit like that. A few ancient cultures in Central and South America saw the dark areas of the Milky Way as constellations. These dark constellations had a variety of myths associated with them. For example, one important dark constellation was Yacana the Llama. It rises above Cuzco, the ancient city of the Incas, every year in November.

    By the way, the other famous area of the sky that is obscured by molecular dust is visible from the Southern Hemisphere. It’s the famous Coalsack Nebula near the Southern Cross, also known as the constellation Crux. The Coalsack is another region of star-forming activity in our night sky – much like the Great Rift.

    Bottom line: On an August night, looking edgewise into our galaxy’s disk, you’ll notice a long, dark lane dividing the bright starry band of the Milky Way. This so-called Dark Rift or Great Rift is a place where new stars are forming.

    See the full article here .


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    Please help promote STEM in your local schools.

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    Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. “Being an EarthSky editor is like hosting a big global party for cool nature-lovers,” she says.

     
  • richardmitnick 1:12 pm on May 14, 2018 Permalink | Reply
    Tags: , , , , Milky Way   

    From European Space Agency: “Our galaxy’s heart” 

    ESA Space For Europe Banner

    From European Space Agency

    14/05/2018

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

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    ESO/ATLASGAL consortium; ESA/Planck

    ESO APEX Telescope ATLASGAL Large Area Survey of the Galaxy

    ESO/APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

    ESA/Planck 2009 to 2013

    At first glance, this image may resemble red ink filtering through water or a crackling stream of electricity, but it is actually a unique view of our cosmic home. It reveals the central plane of the Milky Way as seen by ESA’s Planck satellite and the Atacama Pathfinder Experiment (APEX), which is located at an altitude of around 5100m in the Chilean Andes and operated by the European Southern Observatory.

    This image was released in 2016 as the final product of an APEX survey mapping the galactic plane visible from the southern hemisphere at submillimetre wavelengths (between infrared and radio on the electromagnetic spectrum). It complements previous data from ESA’s Planck and Herschel space observatories.

    Planck and APEX are an ideal pairing. APEX is best at viewing small patches of sky in great detail while Planck data is ideal for studying areas of sky at the largest scales. It covers the entire sky – no mean feat. The two work together well, and offer a unique perspective on the sky.

    This image reveals numerous objects within our galaxy. The bright pockets scattered along the Milky Way’s plane in this view are compact sources of submillimetre radiation: very cold, clumpy, dusty regions that may shed light on myriad topics all the way from how individual stars form to how the entire Universe is structured.

    From right to left, notable sources include NGC 6334 (the rightmost bright patch), NGC 6357 (just to the left of NGC 6334), the galactic core itself (the central, most extended, and brightest patch in this image), M8 (the bright lane branching from the plane to the bottom left), and M20 (visible to the upper left of M8). A labelled view can be seen here.

    Planck was launched on 14 May 2009 and concluded its mission in October 2013. The telescope returned a wealth of information about the cosmos; its main aim was to study the Cosmic Microwave Background (CMB), the relic radiation from the Big Bang. Among other milestones, Planck produced an all-sky map of the CMB at incredible sensitivity and precision, and took the ‘magnetic fingerprint’ of the Milky Way by exploring the behaviour of certain light emitted by dust within our galaxy.

    Its observations are helping scientists to explore and understand how the Universe formed, its composition and contents, and how it has evolved from its birth to present day.

    APEX is a collaboration between the Max Planck Institute for Radio Astronomy, the Onsala Space Observatory, and the European Southern Observatory, ESO. The telescope is operated by ESO.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    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 8:59 am on April 25, 2018 Permalink | Reply
    Tags: , , , , , , Milky Way,   

    From Science Magazine: “European satellite reveals motions of more than 1 billion stars and shape of the Milky Way” 

    ScienceMag
    Science Magazine

    Apr. 25, 2018
    Daniel Clery

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    The Large Magellanic Cloud, one of the Milky Way’s nearest neighbors, may be more massive than previously thought. The image is not a photograph, but rather a map of the density of stars detected by Gaia in each pixel.
    DPAC/Gaia/ESA/Gaia

    Large Magellanic Cloud. Adrian Pingstone December 2003

    ESA/GAIA satellite

    “It’s like waiting for Christmas,” said Vasily Belokurov, an astronomer at the University of Cambridge in the United Kingdom last week. Today, the gifts arrived: the exact positions, motions, brightnesses, and colors of 1.3 billion stars in and around the Milky Way, as tracked by the European Space Agency’s (ESA’s) €750 million Gaia satellite, which after launch in 2013 began measuring the positions of stars and, over time, how they move. On 25 April, ESA made Gaia’s second data set—based on 22 months of observations—publicly available, which should enable a precise 3D map of large portions of the galaxy and the way it moves. “Nothing comes close to what Gaia will release,” Belokurov says.

    One might think that the galaxy is completely mapped. But large parts of it are obscured by gas and dust, and it is hard to discern structure from the vantage of the solar system. Gaia is not only expected to clarify the spiral structures of the galaxy today, but because the satellite traces how stars move, astronomers can wind the clock backward and see how the galaxy evolved over the past 13 billion years—a field known as galactic archaeology. With Gaia’s color and brightness information, astronomers can classify the stars by composition and identify the stellar nurseries where different types were born, to understand how chemical elements were forged and distributed.

    Gaia isn’t only about the Milky Way. For solar system scientists, the new data set will contain data on 14,000 asteroids. That’s a small fraction of the roughly 750,000 known minor bodies, but Gaia provides orbit information 100 times more accurate than before, says University of Cambridge astronomer Gerry Gilmore, who heads the U.K. branch of Gaia’s data processing consortium. That should help astronomers identify families of asteroids and trace how they relate to each other, shedding light on the solar system’s past and how planets formed from smaller bodies.

    See the full article here .

    Please help promote STEM in your local schools.

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  • richardmitnick 9:34 am on April 21, 2018 Permalink | Reply
    Tags: , , , , , Milky Way,   

    From University of Heidelberg: “Stars Are Born in Loose Groupings” 

    U Heidelberg bloc

    University of Heidelberg

    20 April 2018

    Analysis of Gaia satellite data points to a new view of star formation.

    ESA/GAIA satellite

    Based on previously published data from the Gaia Mission, researchers at Heidelberg University have derived the conditions under which stars form. The Gaia satellite is measuring the three-dimensional positions and motions of stars in the Milky Way with unprecedented accuracy.

    Milky Way Galaxy Credits: NASA/JPL-Caltech/R. Hurt

    Milky Way by GAIA ESA

    Using these data, Dr Jacob Ward and Dr Diederik Kruijssen determined the positions, distances and speeds of a large number of young massive stars within 18 nearby loose stellar groupings. The researchers were able to demonstrate that there is no evidence whatsoever that these associations are expanding. They therefore could not have originated as a dense cluster and then expanded to their current size.

    The long-standing model of star formation maintains that most, if not all stars originate in relatively densely packed star clusters. Experts refer to this as the “monolithic” model of star formation. Based on that model, every grouping of young stars observable today must have had its origin in one or more much denser clusters. After the stars formed, these clusters expelled the remaining molecular gas and were able to expand due to the loss of the gravitationally bound mass. Today’s less dense clusters would have formed in this way and hence now, millions of years later, would evidence clear signs of strong expansion.

    For Dr Ward and Dr Kruijssen, the results of their research clearly indicate that the “monolithic” model of star formation is simply not viable. Both researchers favour another explanation, namely that only a small fraction of stars are born within dense clusters. Instead, stars form across wide-spread molecular gas clouds across a broad range of densities. This “hierarchical” model of star formation explains today’s star clusters and associations with a variety of densities showing no signs of further expansion.

    The next publication of data from the Gaia Mission is scheduled for April 25 this year. By then, data on over a billion stars will have been collected – at least five hundred times that of the two million stars that were included in this initial study. Jacob Ward and Diederik Kruijssen hope that this new data will enable them to expand their study to potentially hundreds of loose stellar groupings, known as OB Associations, and to delve much further into the question of how stars originate. Dr Ward and Dr Kruijssen conduct research at the Institute of Astronomical Computing at Heidelberg University’s Centre for Astronomy (ZAH). Their research is part of the work being done in the Collaborative Research Center (CRC 881) “The Milky Way System”.

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    Hubble Space Telescope image of the OB association Cepheus OB4, one of the loose groupings of young stars studied by Dr Ward and Dr Kruijssen. The young stars are visible in bright blue; the gas and dust left after their formation is shown in red colours and dark shades. The results of the Gaia satellite show that Cepheus OB4 undergo no expansion, indicating that the stars formed in their current spatial configuration.
    Source: Davide De Martin & the ESA/ESO/NASA Photoshop FITS Liberator.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Heidelberg Campus

    Founded in 1386, Heidelberg University, a state university of BadenWürttemberg, is Germany’s oldest university. In continuing its timehonoured tradition as a research university of international standing the Ruprecht-Karls-University’s mission is guided by the following principles:
    Firmly rooted in its history, the University is committed to expanding and disseminating our knowledge about all aspects of humanity and nature through research and education. The University upholds the principle of freedom of research and education, acknowledging its responsibility to humanity, society, and nature.

     
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