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  • richardmitnick 8:07 am on February 21, 2017 Permalink | Reply
    Tags: Astronomy, , , , , , The thread of star birth   

    From ESA: “The thread of star birth” 

    ESA Space For Europe Banner

    European Space Agency

    1
    Title Star formation on filaments in RCW106
    Released 20/02/2017 9:30 am
    Copyright ESA/Herschel/PACS, SPIRE/Hi-GAL Project. Acknowledgement: UNIMAP / L. Piazzo, La Sapienza – Università di Roma; E. Schisano / G. Li Causi, IAPS/INAF, Italy
    Description

    ESA/Herschel spacecraft
    “ESA/Herschel spacecraft

    Stars are bursting into life all over this image from ESA’s Herschel space observatory. It depicts the giant molecular cloud RCW106, a massive billow of gas and dust almost 12 000 light-years away in the southern constellation of Norma, the Carpenter’s Square.

    Cosmic dust, a minor but crucial ingredient in the interstellar material that pervades our Milky Way galaxy, shines brightly at infrared wavelengths. By tracing the glow of dust with the infrared eye of Herschel, astronomers can explore stellar nurseries in great detail.

    Sprinkled across the image are dense concentrations of the interstellar mixture of gas and dust where stars are being born. The brightest portions, with a blue hue, are being heated by the powerful light from newborn stars within them, while the redder regions are cooler.

    The delicate shapes visible throughout the image are the result of radiation and mighty winds from the young stars carving bubbles and other cavities in the surrounding interstellar material.

    Out of the various bright, blue regions, the one furthest to the left is known as G333.6-0.2 and is one of the most luminous portions of the infrared sky. It owes its brightness to a stellar cluster, home to at least a dozen young and very bright stars that are heating up the gas and dust around them.

    Elongated and thin structures, or filaments, stand out in the tangle of gas and dust, tracing the densest portions of this star-forming cloud. It is largely along these filaments, dotted with many bright, compact cores, that new stars are taking shape.

    Launched in 2009, Herschel observed the sky at far-infrared and submillimetre wavelengths for almost four years. Scanning the Milky Way with its infrared eye, Herschel has revealed an enormous number of filamentary structures, highlighting their universal presence throughout the Galaxy and their role as preferred locations for stellar birth.

    This three-colour image combines Herschel observations at 70 microns (blue), 160 microns (green) and 250 microns (red), and spans over 1º on the long side; north is up and east to the left. The image was obtained as part of Herschel’s Hi-GAL key-project, which imaged the entire plane of the Milky Way in five different infrared bands. A video panorama compiling all Hi-GAL observations was published in April 2016.

    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 7:55 am on February 21, 2017 Permalink | Reply
    Tags: Astronomy, , , , , , Magnetic mirror design for finding evidence of primordial gravitational waves   

    From ESA: “Magnetic mirror design for finding evidence of primordial gravitational waves” 

    ESA Space For Europe Banner

    European Space Agency

    20 February 2017
    No writer credit

    1
    Title Polarisation of the Cosmic Microwave Background: finer detail
    Released 05/02/2015 3:00 pm
    Copyright ESA and the Planck Collaboration
    Description

    A visualisation of the polarisation of the Cosmic Microwave Background, or CMB, as detected by ESA’s Planck satellite on a small patch of the sky measuring 20º across.

    The CMB is a snapshot of the oldest light in our Universe, imprinted on the sky when the Universe was just 380 000 years old. It shows tiny temperature fluctuations that correspond to regions of slightly different densities, representing the seeds of all future structure: the stars and galaxies of today.

    A small fraction of the CMB is polarised – it vibrates in a preferred direction. This is a result of the last encounter of this light with electrons, just before starting its cosmic journey. For this reason, the polarisation of the CMB retains information about the distribution of matter in the early Universe, and its pattern on the sky follows that of the tiny fluctuations observed in the temperature of the CMB.

    In this image, the colour scale represents temperature differences in the CMB, while the texture indicates the direction of the polarised light. The curly textures are characteristic of ‘E-mode’ polarisation, which is the dominant type for the CMB.

    In this image, both data sets have been filtered to show mostly the signal detected on scales around 20 arcminutes on the sky. This shows the fine structure of the measurement obtained by Planck, revealing fluctuations in both the CMB temperature and polarisation on very small angular scales.

    ESA has backed the development of a ‘metamaterial’ device to sift through the faint afterglow of the Big Bang, to search for evidence of primordial gravitational waves triggered by the rapidly expanding newborn Universe.

    “This technological breakthrough widens the potential for a future follow-on to ESA’s 2009-launched Planck mission, which would significantly increase our detailed understanding of the Universe as it began,” explains Peter de Maagt, heading ESA’s Antennas and Sub-Millimetre Wave section.

    ESA/Planck
    ESA/Planck

    Planck mapped the ‘cosmic microwave background’ (CMB) – leftover light from the creation of the cosmos, subsequently redshifted to microwave wavelengths – across the deep sky in more detail than ever before.

    CMB per ESA/Planck
    CMB per ESA/Planck

    The CMB retains properties of ordinary light, including its tendency to polarise in differing directions – employed in everyday life by polarised sunglasses to cut out glare, or 3D glasses used to see alternating differently polarised cinema images through separate eyes.

    2
    Title Metamaterial-reflective half-wave plate
    Released 10/02/2017 4:16 pm
    Copyright Cardiff University
    Description

    Cardiff University’s magnetic mirror half-wave plate design for b-mode polarisation modulation across wide bandwidths. Less than 1 mm thick, this metamaterial-based design employs a combination of a grid-based ‘artificial magnetic conductor’ and metal ‘perfect electrical conductor’ surfaces. The overall effect is to create a differential phase-shift between orthogonal polarisations equal to 180 degrees. The rotation of the plate causes modulation of the polarisation signal.

    Researchers are now searching for one particular corkscrew polarisation of the CMB, known as ‘B-mode polarisation’, predicted to have been caused by gravitational waves rippling through the early Universe as it underwent exponential expansion – surging from a subatomic singularity to its current vastness.

    Identifying these theorised ‘stretchmarks’ within the CMB would offer solid proof that expansion did indeed occur, bringing cosmologists a big step closer to unifying the physics of the very large and the very small.

    “This would be the holy grail of cosmology,” comments Giampaolo Pisano of Cardiff University, heading the team that built the new prototype B-mode polarisation device for ESA.

    3
    The history of the Universe

    Into what is the universe expanding NASA Goddard, Dana Berry
    Into what is the universe expanding NASA Goddard, Dana Berry

    “Our contribution is only a small bit of the hugely complex instrument that will be necessary to accomplish such a detection. It won’t be easy, not least because it involves only a tiny fraction of the overall CMB radiation.”

    One of the main obstacles in detecting primordial B-modes is additional sources of polarisation located between Earth and the CMB, such as dust within our own galaxy.

    Such polarised foreground contributions have different spectral signatures to that of the CMB, however, enabling their removal if measurements are taken over a large frequency range.

    The challenge is therefore to devise a polarisation modulator that operates across a wide frequency bandwidth with high efficiency.

    “Our new ‘magnetic mirror’-based modulator can do just that, thanks to the quite new approach we adopted,” said Giampaolo Pisano.

    Polarisation modulation is often achieved with rotating ‘half-wave plates’. These induce the rotation of the polarised signals which can ‘stick out’ from the unpolarised background. However, the physical thickness of these devices defines their operational bandwidths, which cannot be too large.

    “Our new solution is based on a combination of metal grids embedded in a plastic substrate – what we call a ‘metamaterial’ – possessing customised electromagnetic properties not found in nature.

    “This flat surface transforms and reflects the signal back like a half-wave plate, facing none of the geometrical constraints of previous designs.”

    The team’s prototype multiband magnetic mirror polarisation modulator measures 20 cm across. Any post-Planck space mission would need one larger than a metre in diameter, its design qualified to survive the harsh space environment. The team are now working on enlarging it.

    “To come so far, the University of Cardiff team has had to develop all the equipment and engineering processes making it possible,” adds Peter. “Their work has been supported through ESA’s long-running Basic Technology Research Programme, serving to investigate promising new ideas to help enable future missions.”

    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 7:35 am on February 21, 2017 Permalink | Reply
    Tags: Astronomy, , , , , Faintest galaxies ever seen explain the ‘Missing Link’ in the Universe   

    From Ethan Siegel: “Faintest galaxies ever seen explain the ‘Missing Link’ in the Universe” 

    From Ethan Siegel
    2.20.17

    How gravitational magnification allows us to see what we’ve never seen before.

    “The problem is, you’re trying to find these really faint things, but you’re looking behind these really bright things. The brightest galaxies in the universe are in clusters, and those cluster galaxies are blocking the background galaxies we’re trying to observe.” -Rachael Livermore

    To see farther than ever, we point our most powerful space telescopes at a single region and collect light for days.

    1
    One of the most massive, distant galaxy clusters of all, MACS J0717.5+3745, was revealed by the Hubble Frontier Fields program. Image credit: NASA / STScI / Hubble Frontier Fields.

    The Hubble Frontier Fields program focused on massive galaxy clusters, using their gravity to enhance our sight even further.

    2
    Ultra-distant, colliding galaxy clusters have been revealed by the Hubble Frontier Fields program, looking fainter, wider-field and deeper than any other survey before it. Image credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK), the Hubble SM4 ERO Team, ST-ECF, ESO, D. Coe (STScI), J. Merten (Heidelberg/Bologna), HST Frontier Fields, Harald Ebeling(University of Hawaii at Manoa), Jean-Paul Kneib (LAM)and Johan Richard (Caltech, USA).

    By warping space, the light from background objects gets magnified, revealing extraordinarily faint galaxies.

    3
    Gravitational lenses, magnifying and distorting a background source, allow us to see fainter, more distant objects than ever before. Image credit: ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al.

    The only problem? The cluster itself is closer and overwhelmingly luminous, making it impossible to tease out the distant signals.

    4
    The overwhelmingly large brightness of the galaxies within a foreground cluster, like Abell S1063, shown here, make it a challenge to use gravitational lensing to identify ultra-faint, ultra-distant background galaxies. Image credit: NASA, ESA, and J. Lotz (STScI).

    Until now. Thanks to a superior new technique devised by Rachael Livermore, light from the foreground cluster galaxies can be modeled and subtracted, revealing faint, distant galaxies never seen before.

    5
    The ultra-distant, lensed galaxy candidate, MACS0647-JD, appears magnified and in three disparate locations thanks to the incredible gravity of the gravitational lens of the foreground cluster, MACS J0647. Image credit: NASA, ESA, M. Postman and D. Coe (STScI), and the CLASH Team.

    With Steven Finkelstein and Jennifer Lotz, Livermore has applied this technique to two Frontier Fields clusters already: Abell 2744 and MACS 0416.

    6
    The galaxy cluster MACS 0416 from the Hubble Frontier Fields, with the mass shown in cyan and the magnification from lensing shown in magenta. Image credit: STScI/NASA/CATS Team/R. Livermore (UT Austin).

    The galaxies that came out were up to 100 times fainter than the dimmest galaxies in the Hubble eXtreme Deep Field, setting a new record.

    7
    The smallest, faintest, most distant galaxies identified in the deepest Hubble image ever taken. This new study has them beat, thanks to stronger gravitational lenses. Image credit: NASA, ESA, R. Bouwens and G. Illingworth (UC, Santa Cruz).

    From when the Universe was less than 10% of its current age, the light from these faint, young galaxies made the Universe transparent.

    8
    The reionization and star-formation history of our Universe, where reionization was driven by these faint, early but theoretically numerous galaxies. At last, thanks to Livermore’s work, we’re discovering them. Image credit: NASA / S.G. Djorgovski & Digital Media Center / Caltech.

    Four more Frontier Fields clusters await, while James Webb, launching next year, will extend this technique even further.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    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 5:21 pm on February 20, 2017 Permalink | Reply
    Tags: , Astronomy, , , , , Structures in the Interstellar Medium   

    From AAS NOVA: “Featured Image: Structures in the Interstellar Medium” 

    AASNOVA

    American Astronomical Society

    20 February 2017
    Susanna Kohler

    1

    This beautiful false-color image (which covers ~57 degrees2; click for the full view!) reveals structures in the hydrogen gas that makes up the diffuse atomic interstellar medium at intermediate latitudes in our galaxy. The image was created by representing three velocity channels with colors — red for gas moving at 7.59 km/s, green for 5.12 km/s, and blue for 2.64 km/s — and it shows the dramatically turbulent and filamentary structure of this gas. This image is one of many stunning, high-resolution observations that came out of the DRAO HI Intermediate Galactic Latitude Survey, a program that used the Synthesis Telescope at the Dominion Radio Astrophysical Observatory in British Columbia to map faint hydrogen emission at intermediate latitudes in the Milky Way.

    Synthesis Telescope at the Dominion Radio Astrophysical Observatory in BC,CA
    Synthesis Telescope at the Dominion Radio Astrophysical Observatory in BC,CA

    The findings from the program were recently published in a study led by Kevin Blagrave (Canadian Institute for Theoretical Astrophysics, University of Toronto); to find out more about what they learned, check out the paper below!
    Citation

    K. Blagrave et al 2017 ApJ 834 126. doi:10.3847/1538-4357/834/2/126

    See the full article here .

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  • richardmitnick 4:56 pm on February 20, 2017 Permalink | Reply
    Tags: Astronomy, , , Nickel is the key to unlocking the mystery, Why are there different “flavors” of iron around the Solar System?   

    From Carnegie: “Why are there different “flavors” of iron around the Solar System?” 

    Carnegie Institution for Science
    Carnegie Institution for Science

    February 20, 2017
    Reference to Person:
    Anat Shahar

    New work from Carnegie’s Stephen Elardo and Anat Shahar shows that interactions between iron and nickel under the extreme pressures and temperatures similar to a planetary interior can help scientists understand the period in our Solar System’s youth when planets were forming and their cores were created. Their findings are published by Nature Geoscience.

    Earth and other rocky planets formed as the matter surrounding our young Sun slowly accreted. At some point in Earth’s earliest years, its core formed through a process called differentiation—when the denser materials, like iron, sunk inward toward the center. This formed the layered composition the planet has today, with an iron core and a silicate upper mantle and crust.

    Scientists can’t take samples of the planets’ cores. But they can study iron chemistry to help understand the differences between Earth’s differentiation event and how the process likely worked on other planets and asteroids.

    One key to researching Earth’s differentiation period is studying variations in iron isotopes in samples of ancient rocks and minerals from Earth, as well as from the Moon, and other planets or planetary bodies.

    Every element contains a unique and fixed number of protons, but the number of neutrons in an atom can vary. Each variation is a different isotope. As a result of this difference in neutrons, isotopes have slightly different masses. These slight differences mean that some isotopes are preferred by certain reactions, which results in an imbalance in the ratio of each isotope incorporated into the end products of these reactions.

    One outstanding mystery on this front has been the significant variation between iron isotope ratios found in samples of hardened lava that erupted from Earth’s upper mantle and samples from primitive meteorites, asteroids, the Moon, and Mars. Other researchers had suggested these variations were caused by the Moon-forming giant impact or by chemical variations in the solar nebula.

    Elardo and Shahar were able to use laboratory tools to mimic the conditions found deep inside the Earth and other planets in order to determine why iron isotopic ratios can vary under different planetary formation conditions.

    They found that nickel is the key to unlocking the mystery.

    Under the conditions in which the Moon, Mars, and the asteroid Vesta’s cores were formed, preferential interactions with nickel retain high concentrations of lighter iron isotopes in the mantle. However, under the hotter and higher-pressure conditions expected during Earth’s core formation process, this nickel effect disappears, which can help explain the differences between lavas from Earth and other planetary bodies, and the similarity between Earth’s mantle and primitive meteorites.

    “There’s still a lot to learn about the geochemical evolution of planets,” Elardo said. “But laboratory experiments allow us to probe to depths we can’t reach and understand how planetary interiors formed and changed through time.”

    1
    A scanning electron microscope image of one of the experiments in Elardo and Shahar’s paper that shows a bright, semi-spherical metal (representing a core) next to a gray, quenched silicate (representing a magma ocean). Image is courtesy of Stephen Elardo.

    This work was funded by a grant from the National Science Foundation.

    See the full article here .

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    Carnegie Institution of Washington Bldg

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

     
  • richardmitnick 12:27 pm on February 20, 2017 Permalink | Reply
    Tags: and Pluto Could Soon Be Back, Astronomy, , , , NASA Scientists Have Proposed a New Definition of Planets,   

    From Science Alert: “NASA Scientists Have Proposed a New Definition of Planets, and Pluto Could Soon Be Back” 

    ScienceAlert

    Science Alert

    20 FEB 2017
    BEC CREW

    1
    Pluto’s redemption? Credit: NASA/JHUAPL/SwRI

    NASA scientists have published a manifesto that proposes a new definition of a planet, and if it holds, it will instantly add more than 100 new planets to our Solar System, including Pluto and our very own Moon.

    The key change the team is hoping to get approved is that cosmic bodies in our Solar System no longer need to be orbiting the Sun to be considered planets – they say we should be looking at their intrinsic physical properties, not their interactions with stars.

    “In keeping with both sound scientific classification and peoples’ intuition, we propose a geophysically-based definition of ‘planet’ that importantly emphasises a body’s intrinsic physical properties over its extrinsic orbital properties,” the researchers explain.

    The team is led by Alan Stern, principle investigator of NASA’s New Horizons mission to Pluto, which in 2015 achieved the first-ever fly-by of the controversial dwarf planet.

    Pluto was famously ‘demoted’ to dwarf planet status back in August 2006, when astronomer Mike Brown from the California Institute of Technology (Caltech) proposed a rewrite of the definition of planets.

    The International Astronomical Union (IAU), which controls such things, declared that the definition of a planet reads as follows:

    “A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.”

    Having not yet cleared the neighbourhood of its orbit in space, Pluto could no longer hold the designation of a planet under these new guidelines.

    Stern, who obviously has a great fondness for Pluto, having led the mission that showed us all its adorable heart pattern for the first time, recently called the decision “bullshit”.

    “Why would you listen to an astronomer about a planet?” Stern, a planetary scientist, pointed out to Kelly Dickerson at Business Insider in 2015.

    He said asking an astronomer, who studies a wide variety of celestial objects and cosmic phenomena, rather than a planetary scientist, who focusses solely on planets, moons, and planetary systems, for the definition of a planet is like going to a podiatrist for brain surgery.

    “Even though they’re both doctors, they have different expertise,” Stern said. “You really should listen to planetary scientists that know something about this subject. When we look at an object like Pluto, we don’t know what else to call it.”

    Now, Stern and his colleagues have rewritten the definition of a planet, and are submitting it to the IAU for consideration.

    “We propose the following geophysical definition of a planet for use by educators, scientists, students, and the public,” they write.

    “A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.”

    If that’s a little too jargony for you, their ‘layman’s version’ is simply: “Round objects in space that are smaller than stars.”

    The definition sounds incredibly simple, but it’s deceptively narrow – there aren’t a whole lot of objects objects in the known Universe that would qualify, as it excludes things like stars and stellar objects such as white dwarfs, plus neutron stars and black holes.

    “In keeping with emphasising intrinsic properties, our geophysical definition is directly based on the physics of the world itself, rather than the physics of its interactions with external objects,” the researchers explain.

    This would mean that our Moon, and other moons in the Solar System such as Titan, Enceladus, Europa, and Ganymede, would all qualify as planets, as would Pluto itself, which has already been looking more and more ‘planet-like’ of late.

    The researchers don’t just argue that their definition holds more merit than the current one in terms of what properties we should be using to classify a planet – they say the current definition is inherently flawed for several reasons.

    “First, it recognises as planets only those objects orbiting our Sun, not those orbiting other stars or orbiting freely in the galaxy as ‘rogue planets’,” they explain.
    Second, the fact that it requires zone-clearing means “no planet in our Solar System” can satisfy the criteria, since a number of small cosmic bodies are constantly flying through planetary orbits – including Earth’s.

    Finally, and “most severely”, they say, this zone-clearing stipulation means the mathematics used to confirm if a cosmic body is actually a planet must be distance-dependent, because a “zone” must be clarified.

    This would require progressively larger objects in each successive zone, and “even an Earth-sized object in the Kuiper Belt would not clear its zone”.

    Of course, nothing changes until the IAU makes a decision, and if it decides to rejig the definition of a planet, either by these recommendations or others in the future, it’s going to take a whole lot of deliberating before it becomes official.

    But the team claims to have the public on their side, and if this public debate is anything to go on, maybe it’s time for a rethink – even if Stern just really wants to stop having to answer the question: “Why did you send New Horizons to Pluto if it’s not a planet anymore?”

    You can read the proposal in full here.

    See the full article here .

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  • richardmitnick 11:03 am on February 20, 2017 Permalink | Reply
    Tags: , , Astronomy, , , , Helioseismology, The Sun In A Distant Mirror   

    From astrobites: “The Sun In A Distant Mirror” 

    Astrobites bloc

    Astrobites

    Title: A Distant Mirror: Solar Oscillations Observed on Neptune by the Kepler K2 Mission
    Authors: P. Gaulme et al.
    First Author’s Institution: Department of Astronomy, New Mexico State University
    1
    Status: Published in The Astrophysical Journal Letters, open access

    1
    Figure 1: Snapshot of the line-of-sight velocity variations on the Sun’s surface, measured from the Doppler shift of atmospheric absorption lines. (Image: GONG/NSO/AURA/NSF)

    How can we learn what lies beneath the surface of a star? One approach, called asteroseismology, is to study a star’s vibrations to infer its internal structure. The inside structure of the Sun in particular can be studied in great detail, because its vibrations are actually apparent on its surface (Fig. 1, see also: Helioseismology): The visible pattern of surface quivers shows the imprint of global acoustic oscillations, which are caused by resonant waves traveling through the Sun on peculiar paths, probing various depths. The same must be happening in faraway stars, yet due to their distance only the variability of their overall properties can be measured, for instance changes in brightness or temperature, which are however similarly caused by the stars’ intrinsic oscillations.

    An impressive instrument that has been built specifically to measure the brightness of stars with extreme precision over time is the Kepler space telescope.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    Its primary aim is to detect the transits of exoplanets, but its features make it suitable for asteroseismology as well. The authors of today’s paper investigate how Kepler would see a Sun-like star from far away, by pointing it at Neptune.

    Methods

    The key idea of the paper is to determine the oscillation characteristics of the Sun by analyzing the intensity variations of the sunlight reflected by Neptune. This kind of measurement would allow a novel check of the calibration of widely used scaling relations, by observing the reference star – the Sun – with the same instrument as the actual target stars. These scaling relations are equations that connect the measurable (asteroseismic) quantities with the fundamental stellar properties, for example mass and radius.

    The main parameters of interest are the oscillation frequency of the Sun at maximum amplitude (\nu_{max}), which corresponds to the dominant “5-minute oscillation”, and the mean frequency separation between overtones (\Delta\nu), which are weaker oscillations that are also excited. The paper’s authors split up into seven teams to independently measure these parameters, all using slightly different methods of analysis. The underlying data, namely the light curve and its power spectrum (a decomposition of the light curve into frequency components), are treated just like the data of any other Kepler target (Fig. 2).

    2
    Figure 2: Left: The full Neptune light curve taken with Kepler, showing the intensity variations of the reflected sunlight over 49 days in 1 minute intervals. Right: The gray and black lines are the raw and smoothed power spectrum of the Neptune light curve. The solid red line is the best-fit model, which includes several noise components indicated by the dashed red lines. The main signal due to the 5-minute oscillations of the Sun appears at the bottom right of the plot, around 3100 μHz. For comparison, the green line shows simultaneous VIRGO data (see text). The blue peaks are caused by Neptune’s rotation. (Figure 1 from the paper.)

    Results

    Surprisingly, all teams consistently overestimate the mass and radius of the Sun significantly by about 14% and 4%, assuming the standard solar reference values. However, this discrepancy can be explained by comparison with another, simultaneous light curve that was taken with the dedicated Sun-observing instrument VIRGO (on board the SOHO satellite).

    ESA/NASA SOHO
    ESA/NASA SOHO

    The true value of \nu_{max} was larger than usual during the time of observations, simply due to the random nature of the Sun’s oscillations.

    In addition, the teams attempted to determine not just the frequency spacing, but also the heights and widths of the individual overtones (“peak-bagging”), to create a complete model of the observed oscillation spectrum. The results are rather uncertain due to noise, but the findings of the teams are generally consistent, and they agree well with the VIRGO measurements, after differences in the technical design have been taken into account (e.g. different bandpasses).

    The successful indirect detection of the Sun’s acoustic oscillations in intensity measurements, with Neptune as “a distant mirror”, is a marvelous technological achievement. Not only that, but the lessons learned from this experiment will help further explore the limits of high-precision asteroseismology with Kepler.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 9:21 am on February 20, 2017 Permalink | Reply
    Tags: Astronomy, , , ,   

    From COSMOS: “Fast radio bursts: enigmatic and infuriating” 

    Cosmos Magazine bloc

    COSMOS

    13 February 2017
    Katie Mack

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia
    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    The best science stories are mystery stories. Something unexplained occurs, the detectives gather their clues, theories are proposed and shot down. In the end, if all goes well, the mystery is solved – at least until the next time something goes bump in the night.

    One of the most perplexing mysteries in astronomy today is the fast radio burst, or FRB. Almost 10 years ago, astronomer Duncan Lorimer at West Virginia University noticed a shockingly bright, incredibly quick signal in data collected by the Parkes radio telescope observatory in New South Wales a few years before. Only a few milliseconds long, the burst was as brilliant as some of the brightest galaxies radio astronomers had ever observed.

    Intriguingly, the signal swept across radio frequencies, mimicking the behaviour of bright flashes of radiation from very distant pulsars – ultra-dense stars that emit regular pulses of light. A signal that spreads across frequencies usually indicates that cosmic matter is dispersing the light, in the same way a prism spreads white light into a rainbow.

    But while the burst looked a lot like a pulsar blip, it didn’t repeat the way pulsar signals do, and no other telescope detected it. Dubbed the “Lorimer Burst”, it stood for years as a one-off event.

    Given its uniqueness, some suggested it must have been some kind of Earth-based interference, or perhaps simply a glitch in the Parkes telescope.

    Today, fast radio bursts are no longer anomalies. With a hint of what to look for – very short, bright events – astronomers have scoured data from the Parkes telescope and other radio telescopes around the world. FRBs are now so numerous it’s hard to keep up with their discovery.

    Yet FRBs are a study in contradictions. So far, only one source repeats, but at such irregular intervals that astronomers have not been able to determine a pattern. Only two bursts have coincided with emissions in visible or any other kind of light, which is necessary to pinpoint the source of the FRB since the radio telescopes can’t give an exact location.

    However, one of those two bursts now appears more likely to be a chance alignment than a true correlation, and the other paints the picture of an explosion with such odd characteristics it is hard to reconcile with any known model.

    Careful analysis of different FRB signals has suggested explosions of young stars, or old stars, or even collisions between stars, but none of those fit with an FRB that repeats.

    One of the biggest open questions is exactly how far away FRBs are. Every attempt to work out their distance has been inconclusive. Even the pattern of their locations in the sky is odd. If they’re all far beyond our own galaxy, we would expect them to appear at random places in the sky.

    If they’re all in our galaxy, we should see them mostly along the plane of the Milky Way, where most of the stars are. In actuality, we’ve found them to lie somewhat more often above or below the plane of the galaxy, not randomly like distant sources, and not in the plane like close ones. But with only 20 or so seen so far, it is hard to draw a conclusion.

    Thanks to FRBs, we are now looking at the universe in a new way, redesigning our observation strategies and scouring the data for super-short-duration events. Just as every new observing wavelength we try or instrumental technique we develop opens a new window to the universe, this new frontier may allow us to see an entire zoo of cosmic events that were happening all along, unseen. It wouldn’t be surprising to find that FRBs represent a diverse family of cosmic explosions rather than one kind of thing.

    The key to solving this mystery will be to catch an FRB in the act and, at the same time, see its fingerprints on a signal detected with another kind of light, thus allowing us to see the galaxy it came from.

    Astronomers are already designing surveys that watch for FRBs with radio telescopes and scour the sky with optical, infrared, or gamma ray telescopes around the world simultaneously. Once we have a handful of real-time FRBs along with their host galaxies, we will start to close this case and, more likely than not, open several exciting new ones.

    See the full article here .

    Please help promote STEM in your local schools.

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  • richardmitnick 6:27 pm on February 19, 2017 Permalink | Reply
    Tags: Astronomy, , , , , , NAOJ Nobeyama Radio Observatory, Supernova Remnant W44   

    From EarthSky: “Hints of a quiet, stray black hole” 

    1

    EarthSky
    Via NAOJ Nobeyama Radio Observatory
    No writer credit

    1
    Supernova Remnant W44. https://earthspacecircle.blogspot.com/2015/12/supernova-remnant-w44.html

    Graduate student Masaya Yamada and professor Tomoharu Oka, both of Keio University, led a research team that was surveying gas clouds around the supernova remnant W44, located 10,000 light-years away from us, when they noticed something unusual. Their statement explained:

    “During the survey, the team found a compact molecular cloud with enigmatic motion. This cloud, [nicknamed] the ‘Bullet,’ has a speed of more than 100 km/second [60 miles/second], which exceeds the speed of sound in interstellar space by more than two orders of magnitude. In addition, this cloud, with the size of two light-years, moves backward against the rotation of the Milky Way galaxy.”

    The energy of motion of the Bullet is many times larger than that injected by the original W44 supernova. The astronomers think this energy must come from a quiet, stray black hole, and they proposed two scenarios to explain the Bullet:

    ” In both cases, a dark and compact gravity source, possibly a black hole, has an important role. One scenario is the ‘explosion model’ in which an expanding gas shell of the supernova remnant passes by a static black hole. The black hole pulls the gas very close to it, giving rise to an explosion, which accelerates the gas toward us after the gas shell has passed the black hole. In this case, the astronomers estimated that the mass of the black hole would 3.5 times the solar mass or larger.

    The other scenario is the ‘irruption model’ in which a high speed black hole storms through a dense gas and the gas is dragged along by the strong gravity of the black hole to form a gas stream. In this case, researchers estimated the mass of the black hole would be 36 times the solar mass or larger. With the present dataset, it is difficult for the team to distinguish which scenario is more likely.”

    Via NAOJ Nobeyama Radio Observatory

    ASTE Atacama Submillimeter telescope
    ASTE Atacama Submillimeter telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Telescope

    3
    (a) CO (J=3-2) emissions (color) and 1.4 GHz radio continuum emissions (contours) around the supernova remnant W44. (b) Galactic longitude-velocity diagram of CO (J=3-2) emissions at the galactic latitude of -0.472 degrees. (c -f): Galactic longitude-velocity diagrams of the Bullet in CO (J=1-0), CO (J=3-2), CO (J=4-3), and HCO+ (J=1-0), from left to right. Galactic longitude-velocity diagrams show the speed of the gas at a specific position. Structures elongated in the vertical direction in the diagrams have a large velocity width. Credit: Yamada et al. (Keio University), NAOJ

    4
    Schematic diagrams of two scenarios for the formation mechanism of the Bullet. (a) explosion model and (b) irruption model. Both diagrams show a part of the shock front produced by the expansion of the supernova remnant W44. The shock wave enters into quiescent gas and compresses it to form dense gas. The Bullet is located in the center of the diagram and has completely different motion compared to the surrounding gas. Credit: Yamada et al. (Keio University)

    These astronomers published their findings in January, 2017 in the peer-reviewed Astrophysical Journal Letters.

    A black hole is a place in space where matter is squeezed into a tiny space, and where gravity pulls so hard that even light can’t escape. Black holes are black. No light comes from them. Up to now, most known stellar black holes are those with companion stars. The black hole pulls gas from the companion, which piles up around it and forms a disk. The disk heats up due to the enormous gravitational pull by the black hole and emits intense radiation.

    On the other hand, if a black hole is floating alone in space – as many must be – its lack of light or any sort of emission would make it very, very hard to find.

    See the full article here .

    Please help promote STEM in your local schools.

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  • richardmitnick 2:29 pm on February 18, 2017 Permalink | Reply
    Tags: Astronomy, , , , Hubble Spotlights a Celestial Sidekick,   

    From Hubble: “Hubble Spotlights a Celestial Sidekick” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Feb. 17, 2017
    Image credit: ESA/Hubble & NASA
    Text Credit: European Space Agency
    Last Updated: Feb. 17, 2017
    Editor: Karl Hille

    1

    This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), a highly efficient wide-field camera covering the optical and near-infrared parts of the spectrum. While this lovely image contains hundreds of distant stars and galaxies, one vital thing is missing — the object Hubble was actually studying at the time!

    This is not because the target has disappeared. The ACS actually uses two detectors: the first captures the object being studied — in this case an open star cluster known as NGC 299 — while the other detector images the patch of space just ‘beneath’ it. This is what can be seen here.

    Technically, this picture is merely a sidekick of the actual object of interest — but space is bursting with activity, and this field of bright celestial bodies offers plenty of interest on its own. It may initially seem to show just stars, but a closer look reveals many of these tiny objects to be galaxies. The spiral galaxies have arms curving out from a bright center. The fuzzier, less clearly shaped galaxies might be ellipticals. Some of these galaxies contain millions or even billions of stars, but are so distant that all of their starry residents are contained within just a small pinprick of light that appears to be the same size as a single star!

    The bright blue dots are very hot stars, sometimes distorted into crosses by the struts supporting Hubble’s secondary mirror. The redder dots are cooler stars, possibly in the red giant phase when a dying star cools and expands.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    ESA50 Logo large

    AURA Icon

    NASA image

     
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