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  • richardmitnick 5:33 pm on February 14, 2017 Permalink | Reply
    Tags: , , , , , ESA/Gaia, Milky Way Galaxy, RAdial Velocity Experiment (RAVE) survey   

    From Dunlap: “Missing Stars in the Solar Neighbourhood Reveal the Sun’s Speed and Distance to the Centre of the Milky Way Galaxy” 

    Dunlap Institute bloc
    Dunlap Institute for Astronomy and Astrophysics

    Feb 13 2017
    Dr. Jason Hunt
    Dunlap Fellow
    Dunlap Institute for Astronomy & Astrophysics
    University of Toronto
    p: 416-978-3147
    e: jason.hunt@dunlap.utoronto.ca

    Chris Sasaki
    Communications Co-ordinator
    Dunlap Institute for Astronomy & Astrophysics
    University of Toronto
    p: 416-978-6613
    e: csasaki@dunlap.utoronto.ca
    w: dunlap.utoronto.ca

    1
    A composite image shows the Gaia spacecraft against a backdrop of the Milky Way Galaxy. Image: ESA/ATG medialab; background image: ESO/S. Brunier

    Using a novel method and data from the Gaia space telescope, astronomers from the University of Toronto have estimated that the speed of the Sun as it orbits the centre of the Milky Way Galaxy is approximately 240 kilometres per second.

    In turn, they have used that result to calculate that the Sun is approximately 7.9 kiloparsecs from the Galaxy’s centre—or almost twenty-six thousand light-years.

    Using data from the Gaia space telescope and the RAdial Velocity Experiment (RAVE) survey, Jason Hunt and his colleagues determined the velocities of over 200,000 stars relative to the Sun. Hunt is a Dunlap Fellow at the Dunlap Institute for Astronomy & Astrophysics, University of Toronto.

    The collaborators found an unsurprising distribution of relative velocities: there were stars moving slower, faster and at the same rate as the Sun.

    But they also found a shortage of stars with a Galactic orbital velocity of approximately 240 kilometres per second slower than the Sun’s. The astronomers concluded that the missing stars had been stars with zero angular momentum; i.e. they had not been circling the Galaxy like the Sun and the other stars in the Milky Way Galaxy;

    “Stars with very close to zero angular momentum would have plunged towards the Galactic centre where they would be strongly affected by the extreme gravitational forces present there,” says Hunt. “This would scatter them into chaotic orbits taking them far above the Galactic plane and away from the Solar neighbourhood.”

    “By measuring the velocity with which nearby stars rotate around our Galaxy with respect to the Sun,” says Hunt, “we can observe a lack of stars with a specific negative relative velocity. And because we know this dip corresponds to 0 km/sec, it tells us, in turn, how fast we are moving.”

    Hunt and his colleagues then combined this finding with the proper motion of the supermassive blackhole known as Sagittarius A* (“A-star”) that lies at the centre of the Galaxy to calculate the 7.9 kiloparsec distance.

    Proper motion is the motion of an object across the sky relative to distant background objects. They calculated the distance in the same way a cartographer triangulates the distance to a terrestrial landmark by observing it from two different positions a known distance apart.

    The result was published in Astrophysical Journal Letters in December 2017.

    The method was first used by Hunt’s co-author, current chair of the Department of Astronomy & Astrophysics at the University of Toronto, Prof. Ray Calberg, and Carlberg’s collaborator, Prof. Kimmo Innanen. But the result Carlberg and Innanen arrived at was based on less than 400 stars.

    Gaia is creating a dynamic, three-dimensional map of the Milky Way Galaxy by measuring the distances, positions and proper motion of stars. Hunt and his colleagues based their work on the initial data release from Gaia which included hundreds of thousands of stars. By the end of its 5 year mission, the space mission will have mapped well over 1 billion stars.

    The velocity and distance results are not significantly more accurate than other measurements. But according to Hunt, “Gaia’s final release in late 2017 should enable us to increase the precision of our measurement of the Sun’s velocity to within approximately one km/sec, which in turn will significantly increase the accuracy of our measurement of our distance from the Galactic centre.”

    Additional notes:

    1) The RAdial Velocity Experiment, or RAVE, is a survey of stars conducted at the Australian Astronomical Observatory (AAO) between 2003 and 2013. It measured the positions, distances, radial velocities and spectra of half-a-million stars—over two hundred thousand of which are included in Gaia data.

    See the full article here .

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    Dunlap Institute campus

    The Dunlap Institute is committed to sharing astronomical discovery with the public. Through lectures, the web, social and new media, an interactive planetarium, and major events like the Toronto Science Festival, we are helping to answer the public’s questions about the Universe.
    Our work is greatly enhanced through collaborations with the Department of Astronomy & Astrophysics, Canadian Institute for Theoretical Astrophysics, David Dunlap Observatory, Ontario Science Centre, Royal Astronomical Society of Canada, the Toronto Public Library, and many other partners.

     
  • richardmitnick 10:14 am on November 28, 2016 Permalink | Reply
    Tags: , , , How long to orbit Milky Way’s center?, Milky Way Galaxy   

    From EarthSky: “How long to orbit Milky Way’s center?” 

    1

    EarthSky

    1
    Our sun is located about two-thirds of the way out from the center of the Milky Way. Illustration via Caltech.

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

    The planets in our solar system orbit around the sun. One orbit of the Earth takes one year. Meanwhile, our entire solar system – our sun with its family of planets, moon, asteroid and comets – orbits the center of the Milky Way galaxy. Our sun and solar system move at about about 500,000 miles an hour (800,000 km/hr) in this huge orbit. So in 90 seconds, for example, we all move some 12,500 miles (20,000 km) in orbit around the galaxy’s center.

    Our Milky Way galaxy is a big place. Even at this blazing speed, it takes the sun approximately 225-250 million years to complete one journey around the galaxy’s center.

    This amount of time – the time it takes us to orbit the center of the galaxy – is sometimes called a cosmic year.

    2
    Artist’s concept of solar system with the Milky Way galaxy in the background.

    By the way, in the past when we’ve talked about this subject, people have commented on the difference between the words rotate and revolve. The word revolve means to orbit around another body. Earth revolves (or orbits) around the sun. The sun revolves around the center of the Milky Way galaxy.

    On the other hand, rotate means to spin on an axis. The Earth rotates every 24 hours. The sun rotates, but not at a single rate across its surface. The movements of the sunspots indicate that the sun rotates once every 27 days at its equator, but only once in 31 days at its poles.

    What about the Milky Way galaxy? Yes, the whole galaxy could be said to rotate, but like our sun, the galaxy is spinning at different rates as you move outward from its center. At our sun’s distance from the center of the Milky Way, it’s rotating once about every 225-250 million years – defined by the length of time the sun takes to orbit the center of the galaxy.

    3
    Illustration of a rotating galaxy, with different parts of the galaxy revolving around the center at different rates. Scientists call this “differential rotation.” Stars near the center revolve around the center faster than those farther out. This diagram is from Nick Strobel’s Astronomy Notes. Go to his site at http://www.astronomynotes.com for updates and more info.

    Bottom line: The planets in our solar system orbit (revolve) around the sun, and the sun orbits (revolves) around the center of the Milky Way galaxy. We take about 225-250 million years to revolve once around the galaxy’s center. This length of time is called a cosmic year.

    See the full article here .

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  • richardmitnick 3:12 pm on June 10, 2016 Permalink | Reply
    Tags: , , Milky Way Galaxy,   

    From natgeo: “How Much Does the Milky Way Weigh?” 

    National Geographic

    National Geographics

    May 31, 2016
    Michelle Z. Donahue

    1
    The band of the Milky Way stretches over Natural Bridges National Monument in Utah.
    Photograph by Jim Richardson, National Geographic Creative

    Want to start a fight between astrophysicists who study the Milky Way? Ask them to tell you how much the galaxy weighs.

    Now, a new modeling method by researchers at McMaster University in Ontario, Canada, may help put those debates to rest.

    According to the new work, presented May 31 at a Canadian Astronomical Society conference in Winnipeg, the Milky Way contains the same amount of mass as 700 billion suns—and that puts it on the slimmer side of the scale. At the same time, our galaxy seems to contain slightly more dark matter than previously calculated. This mysterious invisible substance is thought to exist in a cloud around the Milky Way.

    Figuring out how much the Milky Way currently weighs can allow cosmologists to get a better handle on our galaxy’s past and future.

    “Understanding our galaxy’s mass puts it into a better cosmological context,” says study leader Gwendolyn Eadie, a doctoral candidate at McMaster. For starters, the rate at which stars in any given galaxy form, exist, and die seems to be tied to the overall mass of the galaxy.

    “People who study the evolution of galaxies look at how the mass relates to its evolution,” says Eadie. “If we have a better handle on what the mass of the Milky Way is, we can understand how it and other galaxies form and evolve.”

    Moving Through Dark Matter

    Previous estimates of how much matter the Milky Way contains vary wildly. Some studies report it holds the equivalent of 1 trillion suns, while others say it’s merely 100 billion.

    Those measurements all include the types of matter we can observe or detect directly—dust, planets, moons, stars, and some of the dwarf galaxies orbiting the Milky Way—as well as the galaxy’s dark matter halo.

    Invisible except for its gravitational effects on other objects, dark matter is exceptionally tricky to measure, and Eadie has been working on the problem since she started graduate work studying ancient groups of stars known as globular clusters.

    Eadie ultimately devised a method to measure our galaxy’s dark matter using the known motions and velocities of 89 globular clusters that exist around the Milky Way.

    She used globular clusters because they are dispersed at different distances throughout the galaxy, and because they are relatively large, well defined, and easier to track over time than individual stars. As these clusters orbit the galactic center, dark matter pushes and pulls on them in predictable ways.

    Put together with the known masses of visible objects in the galaxy, her model created a “mass profile” of the Milky Way, which estimates the mass contained within any distance from the galactic center.

    At 700 billion suns, Eadie’s final estimate agrees more closely with the “lighter galaxy” camp, which judges that some of the outer-edge objects, including some large, distant globular clusters and diffuse dwarf galaxies, aren’t truly bound by the Milky Way’s gravity and thus not part of its overall total mass.

    And since the stellar mass of the galaxy is currently estimated at around 60 billion suns, and dust and gas make up about one to three percent of the rest, Eadie’s results suggest that as much as 88 percent of the mass in the Milky Way is comprised of dark matter.

    Hefty Home

    While Eadie’s work isn’t the first to try to estimate the mass of the galaxy, her study combines a wide variety of data sources to yield one of the most thorough analyses to date, says Alan McConnachie, a research officer and instrument specialist at the National Research Council of Canada’s Herzberg Institute for Astrophysics.

    “Figuring out how fast, and in what direction, globular clusters are moving is pretty hard. Combining all of these data together in a consistent model for the Milky Way is a real challenge,” McConnachie says.

    “People sometimes are a bit surprised that we don’t have a better idea of how heavy the Milky Way is, given that it’s the galaxy we live in,” he adds. “This work is a big step toward being able to claim with confidence that we know how massive our home actually is.”

    For Eadie, the result is inspiration to continue astrophysicists’ efforts to pinpoint the nature of dark matter.

    “On the one hand, the visible Milky Way in the night sky is extensive—that stream of stars and dust across the dark sky is beautiful, magnificent, and enormous,” Eadie says. “But the idea that the stuff I’m seeing is only about one-fifth of what’s out there inspires me to figure out what we’re missing.”

    See the full article here .

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  • richardmitnick 2:51 pm on June 10, 2016 Permalink | Reply
    Tags: 80 Percent of Humankind Can’t See the Milky Way Anymore, , , Milky Way Galaxy,   

    From natgeo: “80 Percent of Humankind Can’t See the Milky Way Anymore” 

    National Geographic

    National Geographics

    June 10, 2016
    Michelle Z. Donahue

    1
    The Milky Way illuminates the sky over Dinosaur National Monument, which spreads across Colorado and Utah. Photograph by Dan Duriscoe

    The Milky Way galaxy, that torrent of stars that slashes across a deeply darkened night sky, has been a deep well of inspiration from humanity’s earliest days. The ancient Egyptians saw it as a pool of cow’s milk, while in Hindu mythology the arcing galactic arm was likened to a dolphin swimming through the sky. Countless scientists, philosophers, and artists, including Galileo, Aristotle, and Vincent Van Gogh, have drawn upon the galaxy as their muse. (Read “How Much Does the Milky Way Weigh?”)

    But a new atlas of the night sky across the entire globe shows that more than 80 percent of the planet’s land areas—and 99 percent of the population of the United States and Europe—live under skies so blotted with man-made light that the Milky Way has become virtually invisible.

    Fabio Falchi, a researcher at the Light Pollution Science and Technology Institute (ISTIL) in Thiene, Italy, announced Friday the release of a new survey that quantifies nighttime sky quality for every region in the world. Produced using over 35,000 ground-based observations and six months of data from 2014 collected with the Suomi National Polar-orbiting Partnership (NPP) satellite, the atlas is an update to a 2001 work and shows the planet’s darkest and brightest locations in stark contrast.

    NASA/Goddard Suomi NPP satellite
    NASA/Goddard Suomi NPP satellite

    Woe to Singapore, a place of eternal twilight, with the entire population living under skies so bright their eyes cannot fully adjust to night vision, let alone see the Milky Way. Kuwait, Qatar, and the United Arab Emirates have it nearly as bad.

    On the other hand, more than 75 percent of the population of Chad, the Central African Republic, and Madagascar live under near-pristine skies, or places where background light represents less than one percent of the sky’s overall brightness. And according to Falchi’s analysis, residents of the Azores have the distinction of living the farthest from land with unspoiled skies: They’d have to travel nearly 1,100 miles, to the western Sahara, to experience an ancestrally darkened landscape (unless they travel out into the ocean).

    2
    Light pollution clouds the view over Joshua Tree National Park, California. Photograph by Dan Duriscoe

    “In the first atlas we had a hint of what was happening, but these numbers are shocking,” Falchi says. “We have lost the connection with our roots, of literature, of philosophy, of science, of religion—all are connected with the contemplation of the night sky. A new generation can no longer appreciate this beauty.” (“See a Stunning New View of the Milky Way.”)

    Study co-author Dan Duriscoe, a physical scientist with the National Park Service’s Natural Sounds and Night Skies Division, has worked in the Park Service for 36 years and has collected light measurements in national parks since 1994. On the East Coast, apart from a few scattered points in West Virginia, Pennsylvania, and New England, it’s extremely difficult to get to a place with an unfettered view of stars.

    “People could get that experience closer to home decades ago, but now they’re forced out into Utah or Death Valley or Yellowstone, somewhere far from their backyards,” Duriscoe says. “There’s an increased public awareness of how this is a rare experience and becoming one that will cost them some money to go see.”

    High-Tech Eyes on the Sky

    Sweeping over the Earth’s poles 14 times a day, the Suomi satellite generates a complete global set of high-resolution day and night images every 24 hours. Falchi, along with ISTIL colleague Pierantonio Cinzano, worked with data from partners including the National Park Service (NPS) and the National Oceanographic and Atmospheric Administration (NOAA) to produce the atlas. The 2001 atlas looked at only light escaping from Earth into space, while the new data reveal where light is reflected from the sky down to the Earth’s surface. (Read “Graveyard of Stars May Lie at Milky Way’s Center.”)

    Falchi plans to release a print version of the atlas, and an interactive digital atlas, similar to one from 2006 produced using the 2001 data, is also in the works.

    3
    A map illustrates light pollution in North and South America. Illustration by Fabio Falchi, Google Earth

    Chris Elvidge, a co-author of the study and a scientist with NOAA’s National Centers for Environmental Information, says he expects that the satellite data and analysis will be useful not only for astronomers, who have a vested interest in a dark night sky, but also for biologists studying light impacts on nocturnal organisms, medical researchers interested in the human health effects, and city planners.

    One drawback of the satellite’s imaging instruments is limited detection of the blue and violet parts of the visible spectrum—the very zone where white LEDs would show up on satellite scans. Though highly efficient, white LEDs can be excessively bright, and as municipalities begin to install them in streetlights and for other outdoor purposes, the impact of LEDs may actually worsen overall light pollution in the long run.

    “Several cities have jumped on the LED bandwagon without getting their citizens’ approval,” says Connie Walker, an astronomer with the National Optical Astronomy Observatory in Tucson, Arizona, and a board member of the International Dark-Sky Association. Jurisdictions interested in effectively reducing light pollution can turn to the two atlases to research before-and-after maps, and compare what’s worked and what hasn’t, she says.

    “This atlas affords a consistent way of comparing light pollution in different areas of the world over the last 15 years,” she says.

    4
    This map shows light pollution in the Eastern Hemisphere. Illustration by Fabio Falchi, Google Earth

    Falchi’s work, done completely in his off hours as a labor of love, helps put the extent of the problem into perspective, Duriscoe says.

    “To tackle this on a global scale, nobody else before has attempted it,” he says. “When you can stand back and look at the whole Earth and the impact of our modern lifestyle on the ability of all cultures to enjoy the natural nocturnal environment, it shows how we just take it for granted.”

    Protecting Natural Cycles

    At one time, communities with large telescopes, like the Palomar Observatory outside of San Diego, California, prided themselves on their efforts to protect the night sky, though that attitude seems to have waned over the last several decades, Duriscoe notes. Now, however, with more research emerging about the negative impacts on humans of overexposure to light, there has been an uptick of interest in combating the 24-hour lifestyle.

    Falchi has been personally involved in his own community in changing approaches to outdoor lighting. As the current president of the nonprofit CieloBuio dark skies advocacy organization, he spearheaded a petition effort in the late 1990s to enact lighting reform laws in Lombardia, the region where he lives and works. With controls on the types of new fixtures being installed and limits on light intensity in given areas, despite a twofold increase in the number of new lights, light-pollution levels in the region have remained constant from 2000 to today.

    Though much of Italy is now governed by similar laws, it’s still only a start, Falchi says.

    “This is not a sufficient measure for controlling light pollution, but simply a stop in the increase,” he adds. “For almost all other pollutants—chemical, particulate, carbon monoxide, or anything else, graphs show that almost all of them have decreased over the last 20 years. We need to decrease pollution from light as well.”

    See the full article here .

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  • richardmitnick 3:33 pm on April 16, 2016 Permalink | Reply
    Tags: , , , Milky Way Galaxy   

    From ESO: “Comparison of the central part of the Milky Way at different wavelengths (annotated)” 

    ESO 50 Large

    European Southern Observatory

    24 February 2016 [Never saw it, would have posted it.]
    Unsigned

    1
    Credit: ESO/ATLASGAL consortium/NASA/GLIMPSE consortium/VVV Survey/ESA/Planck/D. Minniti/S. Guisard
    Acknowledgement: Ignacio Toledo, Martin Kornmesser

    This comparison shows the central regions of the Milky Way observed at different wavelengths.

    The top panel shows compact sources of submillimetre radiation detected by APEX as part of the ATLASGAL survey, combined with complementary data from ESA’s Planck satellite, to capture more extended features.

    ESA/Planck
    ESA/Planck

    The second panel shows the same region as seen in shorter, infrared, wavelengths by the NASA Spitzer Space Telescope.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    The third panel shows the same part of sky again at even shorter wavelengths, the near-infrared, as seen by ESO’s VISTA infrared survey telescope at the Paranal Observatory in Chile. Regions appearing as dark dust tendrils here show up brightly in the ATLASGAL view.

    Finally the bottom picture shows the more familiar view in visible light, where most of the more distant structures are hidden from view.

    The significance of the colours varies from image to image and they cannot be directly compared.

    See the full article here .

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

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  • richardmitnick 10:06 am on March 22, 2016 Permalink | Reply
    Tags: , ATLASGAL, , Milky Way Galaxy,   

    From Ethan Siegel: “New map of the Milky Way now complete!” 

    Starts with a bang
    Starts with a Bang

    3.21.16
    Ethan Siegel

    Milky Way map NASA/JPL Caltech/ESOR. Hurt
    Milky Way map NASA/JPL Caltech/ESOR. Hurt

    Milky Way map. ATLASGAL .Image credit  ESO APEX ATLASGAL consortiumNASA GLIMPSE consortium ESA Planck
    Milky Way map. ATLASGAL .Image credit ESO/APEX ATLASGAL consortium NASA/GLIMPSE consortium ESA/Planck

    ESA/Planck
    ESA/Planck

    “True realism consists in revealing the surprising things which habit keeps covered and prevents us from seeing.” -Jean Cocteau

    Our atmosphere is great for viewing the Milky Way in visible light, but other wavelengths are mostly blocked.

    This is too bad, because the dust in our galaxy blocks visible light, leaving much of the Universe unexplored.

    1
    Atmospheric transmission windows as a function of wavelength. Images credit: Created as part of the project ENGL/EMIR Carsten Stech (top, with absorption/transmission features); NASA / Wikimedia Commons user Mysid (bottom), edits by E. Siegel.

    Earth has a few narrow “windows,” however, where the atmospheric gases allow light of particular wavelength ranges to penetrate.

    2
    The view of the galactic center in four different wavelength bands. Atop, from the ATLASGAL survey at 870 microns; below that, from Spitzer in the mid-IR; below that, from ESO’s VISTA in the near-IR, and at the bottom in visible light, where the dust obscures everything of interest. Image credit: ESO/ATLASGAL consortium/NASA/GLIMPSE consortium/VVV Survey/ESA/Planck/D. Minniti/S. Guisard. Acknowledgement: Ignacio Toledo, Martin Kornmesser.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    ESO/Vista Telescope
    ESO/Vista Telescope

    Rather than needing to go to space to map the Universe, we can build ground based telescopes and arrays capable of gathering far more light than a space-based observatory.

    ESO/APEX
    ESO/APEX

    In the Chilean plateaus, a 12-meter radio telescope known as the Atacama Pathfinder EXperiment (APEX) just mapped the entire southern galactic plane at unprecedented wavelengths: the sub-millimeter, between the infrared and the radio.


    Access mp4 video here .

    More than 70 scientific papers have already been published, but most fabulous of all are the images.

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    The latest composite release, from the ATLASGAL collaboration. Image credit: ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium/ESA/Planck.

    These wavelengths map the cold dust, which will form the next generation of stars in our galactic plane.

    4
    The latest composite release, from the ATLASGAL collaboration. Image credit: ESO/APEX/ATLASGAL consortium/NASA/GLIMPSE consortium/ESA/Planck.

    While all the other infrared wavelengths hide this dust from view, this latest survey, the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), beats even space-based surveys for resolution.


    Access mp4 video here .

    Enjoy this first-time view of our galaxy’s future stars.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 9:03 pm on January 8, 2016 Permalink | Reply
    Tags: , , Milky Way Galaxy,   

    From SDSS: “Largest Age Map of the Milky Way Reveals How Our Galaxy Grew Up” 

    SDSS Telescope

    Sloan Digital Sky Survey

    January 8, 2016
    Jordan Raddick

    Temp 1
    This image shows the latest results as colored dots superimposed on an artist’s conception of the Milky Way. Red dots show stars that formed when the Milky Way was young and small, while blue shows stars that formed more recently, when the Milky Way was big and mature. The color scale shows how many billion years have passed since those stars formed. Credit: G. Stinson (MPIA)

    Melissa Ness-Our Galaxy grew up by growing out.

    Steve Majewski-Seeing so many stars at once means getting spectra of 70,000 red giants is actually possible with a single telescope in a few years’ time.

    “Close to the center of our Galaxy, we see old stars that were formed when it was young and small. Farther out, we see young stars. We conclude that our Galaxy grew up by growing out,” says Ness, lead author of the study. “To see this, we needed an age map spanning large distances, and that’s what this new discovery gives us.”

    The researchers mapped the Galaxy by observing red giants, bright stars in the final stages of their lives that can be observed out to large distances from our Sun, into the very inner and outer reaches of the Milky Way. “If we know the mass of a red giant star, we know its age by using the fusion clock inside every star,” says Marie Martig, lead author of a related study and a co-author of Ness’s study. “Finding masses of red giant stars has historically been very difficult, but surveys of the Galaxy have made new, revolutionary techniques possible.”

    The team started with spectra taken from one of the SDSS’s component surveys, the Apache Point Observatory Galaxy Evolution Experiment (APOGEE).

    Temp 2
    IR map of the whole Galaxy showing the plane and bulge of the Galaxy full of stars and dust. APOGEE uses new IR instrumentation to study stars within the disk and is less affected by the extinction from interstellar dust.

    “APOGEE is the ideal survey for this work because it can get high-quality spectra for 300 stars simultaneously over a large area of sky,” says Steve Majewski of the University of Virginia and Principal Investigator of the APOGEE survey. “Seeing so many stars at once means getting spectra of 70,000 red giants is actually possible with a single telescope in a few years’ time.”

    The ages of stars cannot be measured with APOGEE spectra alone, but the APOGEE team realized that light curves from the Kepler satellite, a NASA space mission whose main goal is to find planets around stars, could provide the missing link between APOGEE spectra and stellar ages.

    NASA Kepler Telescope
    Kepler

    APOGEE therefore observed thousands of red giants that had also been seen by Kepler. After combining information from the APOGEE spectra and Kepler lightcurves, the researchers could then apply their methods to measure ages for all 70,000 red giant stars sampling all parts of the galaxy.

    “In the galaxy we know best – our own – we can clearly read the story of how galaxies form in a Universe with large amounts of cold dark matter,” says Ness. “Because we can see so many individual stars in the Milky Way, we can chart its growth in unprecedented detail. This unprecedented, enormous map really is one for the ages.”

    See the full article here.

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    The Sloan Digital Sky Survey has created the most detailed three-dimensional maps of the Universe ever made, with deep multi-color images of one third of the sky, and spectra for more than three million astronomical objects. Learn and explore all phases and surveys—past, present, and future—of the SDSS.

    The SDSS began regular survey operations in 2000, after a decade of design and construction. It has progressed through several phases, SDSS-I (2000-2005), SDSS-II (2005-2008), SDSS-III (2008-2014), and SDSS-IV (2014-). Each of these phases has involved multiple surveys with interlocking science goals. The three surveys that comprise SDSS-IV are eBOSS, APOGEE-2, and MaNGA, described at the links below. You can find more about the surveys of SDSS I-III by following the Prior Surveys link.

    Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS- IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is http://www.sdss.org.

    SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU) / University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatory of China, New Mexico State University, New York University, University of Notre Dame, Observatório Nacional / MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, and Yale University.

     
  • richardmitnick 10:18 am on December 24, 2015 Permalink | Reply
    Tags: , , , Milky Way Galaxy   

    From ESA: “Stellar density map” 

    ESASpaceForEuropeBanner
    European Space Agency

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    Credits: ESA/Gaia – CC BY-SA 3.0 IGO

    The outline of our Galaxy, the Milky Way, and of its neighbouring Magellanic Clouds, in an image based on housekeeping data from ESA’s Gaia satellite, indicating the total number of stars detected every second in each of the satellite’s fields of view.

    ESA Gaia satellite
    Gaia

    2
    Seen from the southern skies, the Large and Small Magellanic Clouds (the LMC and SMC, respectively) are bright patches in the sky. These two irregular dwarf galaxies, together with our Milky Way Galaxy, belong to the so-called Local Group of galaxies. Astronomers once thought that the two Magellanic Clouds orbited the Milky Way, but recent research suggests this is not the case, and that they are in fact on their first pass by the Milky Way. The LMC, lying at a distance of 160 000 light-years, and its neighbour the SMC, some 200 000 light-years away, are among the largest distant objects we can observe with the unaided eye. Both galaxies have notable bar features across their central discs, although the very strong tidal forces exerted by the Milky Way have distorted the galaxies considerably. The mutual gravitational pull of the three interacting galaxies has drawn out long streams of neutral hydrogen that interlink the three galaxies.
    Date 27 August 2009
    Source ESO

    3
    Local Group. Andrew Z. Colvin

    Brighter regions indicate higher concentrations of stars, while darker regions correspond to patches of the sky where fewer stars are observed.

    The plane of the Milky Way, where most of the Galaxy’s stars reside, is evidently the brightest portion of this image, running horizontally and especially bright at the centre. Darker regions across this broad strip of stars, known as the Galactic Plane, correspond to dense, interstellar clouds of gas and dust that absorb starlight along the line of sight.

    The Galactic Plane is the projection on the sky of the Galactic disc, a flattened structure with a diameter of about 100 000 light-years and a vertical height of only 1000 light-years.

    Beyond the plane, only a few objects are visible, most notably the Large and Small Magellanic Clouds, two dwarf galaxies orbiting the Milky Way, which stand out in the lower right part of the image. A few globular clusters – large assemblies up to millions of stars held together by their mutual gravity – are also sprinkled around the Galactic Plane.

    Acknowledgement: this image was prepared by Edmund Serpell, a Gaia Operations Engineer working in the Mission Operations Centre at ESA’s European Space Operations Centre in Darmstadt, Germany.

    This work is licenced under the Creative Commons Attribution-ShareAlike 3.0 IGO

    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 11:57 am on December 15, 2015 Permalink | Reply
    Tags: , , Milky Way Galaxy,   

    From New Scientist: “Prodigal gas cloud was born in Milky Way and is crashing back in” 

    NewScientist

    New Scientist

    15 December 2015
    Ken Croswell

    1
    Image: CBill Saxton, NRAO/AUI/NSF

    NRAO GBT
    NRAO Greenbank radio telescope

    CALL it the comeback kid. A massive cloud of gas crashing into the Milky Way probably started its life in our galaxy, according to new observations from the Hubble Space Telescope.

    NASA Hubble Telescope
    NASA/ESA Hubble

    Located 40,000 light years from Earth, Smith’s Cloud is 11,000 light years long, 2500 light years across and has a mass millions of times that of our sun. If we could see it, it would span 30 times the diameter of the full moon from tip to tail.

    But because it is made mostly of hydrogen gas, it is nearly invisible. It was discovered in the early 1960s when astronomer Gail Smith detected radio waves emitted by its hydrogen atoms. In 2008, other astronomers reported that the cloud is moving towards the Milky Way and will crash into its disc in 27 million years.

    “This cloud has always stood out as something of an oddball,” says Andrew Fox, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland.

    Some thought Smith’s Cloud was fresh gas falling into the Milky Way, or a starless galaxy carrying gas and shrouded in dark matter. Either way, the cloud should contain few elements heavier than hydrogen and helium, which are made by stars.

    Now Fox and his colleagues have used Hubble to observe ultraviolet light from three active galactic nuclei that lie billions of light years beyond Smith’s Cloud. By measuring how this light filters through the cloud, they can work out the heavy elements in its composition.

    They found that sulphur atoms in the cloud absorb so much ultraviolet light that its sulphur-to-hydrogen ratio is half that of the sun, suggesting stars have polluted it (Astrophysical Journal Letters, submitted). This means the cloud is hardly a pristine relic from the dawn of time.

    Instead, it is probably material cast out of the galaxy’s disc that is now falling back in.

    “I think that’s by far the best explanation,” says David Nidever, an astronomer at the University of Arizona in Tucson.

    The cloud is as rich in sulphur as the Milky Way’s outer disc, and earlier calculations of its trajectory indicated that, if it did come from our galaxy, it arose about 70 million years ago from a part of the disc 15,000 light years further from the galactic centre than the sun and Earth are.

    But the new finding raises a puzzle: what could catapult such a massive cloud out of the Milky Way’s disc? Exploding stars eject material, but no supernova-driven cloud is nearly so massive.

    “It certainly has left us scratching our heads,” Fox says.

    After getting blasted out of the Milky Way, the cloud may have gained additional mass by accreting some of the hot tenuous gas that pervades the galaxy’s halo. Still, Fox doubts whether this process would have added enough material to explain the cloud’s total mass.

    See the full article here .

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  • richardmitnick 5:50 pm on December 11, 2015 Permalink | Reply
    Tags: , , , Milky Way Galaxy   

    From Astronomy: “A ‘ghost from the past’ recalls the infancy of the Milky Way” 

    Astronomy magazine

    Astronomy Magazine

    December 11, 2015
    SINC, Madrid

    1
    The Milky Way arcs into a panorama in the southern sky, taken from the Paranal Observatory, Chile. ESO/H.H. Heyer

    Globular clusters are spherical-shaped or globular stellar groupings — hence the name — which can contain millions of stars. There are about 200 of them in the Milky Way, but few are as intriguing to astronomers as the E 3 cluster.

    It is situated around 30,000 light-years away in the southern constellation Chameleon. A team of Spanish and Italian astronomers has named it “a ghost from the Milky Way’s past” in an article published recently.

    “This globular cluster and a few similar ones, such as Palomar 5 or Palomar 14, are ‘ghosts’ because they appear to be in the last stages of their existence, and we say ‘from the past’ because they are very old. They were formed when our galaxy was virtually new-born, 13,000 million years ago,” said Carlos de la Fuente Marcos, an independent astronomer who collaborates with colleagues from the Northern Catholic University and ESO in Chile, and the University of Padua in Italy.

    E 3 is hidden behind younger and brighter objects located between the cluster and Earth, but it has been possible to analyze it thanks to the Very Large Telescope (VLT) in the European Southern Observatory (ESO) in Cerro Paranal, Chile.

    ESO VLT Interferometer
    ESO/VLT

    The data obtained revealed some surprises.

    “Unlike typical globular clusters, which contain hundreds of thousands and in some cases millions of stars, the object studied only has a few tens of thousands of them,” said De la Fuente Marcos. “Additionally, it doesn’t have the typical circular symmetry, but a much distorted, almost ghostly rhomboidal shape contorted by the galactic gravitational waves.”

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    The globular cluster E 3 (center).DSS/STScI/©UDS/CNRS

    According to another study on E 3 by Michigan State University (USA) researchers, this cluster is chemically homogeneous — it doesn’t have several star populations in its interior.

    “This is characteristic of an object that was created in block in one single episode, like what is supposed to have happened when our galaxy was born — very large star clusters containing millions of stars were formed — but what remains of them today are objects like E 3, ghosts from a distant past,” said De la Fuente Marcos. He explained that the study of these objects “enables us to gain insight into the infancy of the Milky Way.”

    Native or captured?

    Despite the recently published new data on this strange globular cluster, astronomers still have to clarify if it was really formed in our galaxy or not. It is known that some of its clusters are not native to the Milky Way but were captured, even though they can currently be seen in its interior. Thousands of millions of years ago our galaxy cannibalized other smaller galaxies and kept their globular clusters. The rest were formed in-situ.

    In the article, it is suggested that the object analyzed could be dynamically related to other clusters, such as 47 Tucanae, one of the richest and largest of the Milky Way. They could even share the same stream of stars. If this were the case, it would support the hypothesis that E 3 was captured in the distant past.

    “We hope to obtain new data in 2016 thanks to more spectroscopic observations, and perhaps we will be able to give answers to these questions,” said De la Fuente Marcos.

    See the full article here .

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