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  • richardmitnick 10:51 am on May 27, 2020 Permalink | Reply
    Tags: , , , , , Pulsars   

    From phys.org: “Study unveils properties of 11 recently discovered pulsars” 


    From phys.org

    May 26, 2020
    Tomasz Nowakowski

    1
    Mode-changing behaviour in a 1-hr observation of PSR J0344−0901 recorded on October 16, 2018. Credit: Cameron et al., 2020.

    An international team of astronomers has conducted a detailed study of 11 pulsars recently discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST).

    FAST [Five-hundred-meter Aperture Spherical Telescope] radio telescope, with phased arrays from CSIRO engineers Australia [located in the Dawodang depression in Pingtang County, Guizhou Province, south China

    The new research, presented in a paper published May 19 on arXiv.org [ https://arxiv.org/abs/2005.09171 ], delivers essential information about the properties of these objects.

    Pulsars are highly magnetized, rotating neutron stars emitting a beam of electromagnetic radiation. They are usually detected in the form of short bursts of radio emission, however some of them are also observed using optical, X-ray and gamma-ray telescopes. To date, most pulsars have been discovered using the Parkes Observatory in Australia.

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia, 414.80m above sea level

    Recently, 11 new pulsars have been identified by China’s FAST telescope and confirmed using the 64-meter Parkes Radio Telescope of Parkes Observatory. A group of astronomers, led by Andrew Cameron of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia, investigated these newfound pulsars in detail, hoping to get more insights into their properties. For this purpose, they conducted follow-up observations of this objects with the Parkes Radio Telescope and the 100-meter Effelsberg Radio Telescope located in Germany.

    MPIFR/Effelsberg Radio Telescope, in the Ahrgebirge (part of the Eifel) in Bad Münstereifel, Germany

    “In this paper, we describe 11 pulsars, discovered by FAST with the UWB [ultra-wide-bandwidth] receiver, that have now been monitored with the Parkes telescope for at least one year, thereby enabling a timing solution for each pulsar to be determined,” the astronomers wrote in the paper.

    In general, the study obtained timing models of each pulsar’s spin properties and detailed evaluation of their emission properties, including flux calibration and polarization properties. The investigated pulsars were found to have spin periods ranging from 0.56 to 4.76 seconds, and characteristic ages between 0.65 and 320 million years.

    According to the paper, one of the 11 pulsars, designated PSR J0344−0901, showcases a type of mode-changing behavior in its pulsations. The pulsar was found to transition between its “normal” and “moded” state, which takes place gradually over the course of many tens of seconds. It has a spin period of about 1.23 seconds, dispersion measure of 30.9 parsecs/cm3, and characteristic age of 5.58 million years.

    Another interesting object in the sample is PSR J1926−0652, which exhibits many emission phenomena, including nulling and sub-pulse drifting. With a characteristic age of approximately 650,000 years, it is the youngest pulsar out of the 11 studied objects. It has a spin period of about 1.6 seconds and dispersion measure of 85.3 parsecs/cm3.

    The most unremarkable of the pulsars presented in the paper is PSR J1931−0144. It exhibits a broad, single-component Gaussian pulse, a spin period of about 0.59 seconds, dispersion measure of 38.3 parsecs/cm3, and is the oldest pulsar in the studied sample.

    Summing up the results, the astronomers say that their study paves the way for next-generation pulsar surveys on telescopes like FAST, MeerKAT and Square Kilometre Array (SKA).

    SKA SARAO Meerkat telescope(s), 90 km outside the small Northern Cape town of Carnarvon, SA

    ______________________________________________
    Women in STEM – Dame Susan Jocelyn Bell Burnell discovered pulsars

    Dame Susan Jocelyn Bell Burnell discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Biography

    British astrophysicist, scholar and trailblazer Jocelyn Bell Burnell discovered the space-based phenomena known as pulsars, going on to establish herself as an esteemed leader in her field.Who Is Jocelyn Bell Burnell?
    Jocelyn Bell Burnell is a British astrophysicist and astronomer. As a research assistant, she helped build a large radio telescope and discovered pulsars, providing the first direct evidence for the existence of rapidly spinning neutron stars. In addition to her affiliation with Open University, she has served as dean of science at the University of Bath and president of the Royal Astronomical Society. Bell Burnell has also earned countless awards and honors during her distinguished academic career.

    Early Life

    Jocelyn Bell Burnell was born Susan Jocelyn Bell on July 15, 1943, in Belfast, Northern Ireland. Her parents were educated Quakers who encouraged their daughter’s early interest in science with books and trips to a nearby observatory. Despite her appetite for learning, however, Bell Burnell had difficulty in grade school and failed an exam intended to measure her readiness for higher education.

    Undeterred, her parents sent her to England to study at a Quaker boarding school, where she quickly distinguished herself in her science classes. Having proven her aptitude for higher learning, Bell Burnell attended the University of Glasgow, where she earned a bachelor’s degree in physics in 1965.

    Little Green Men

    In 1965, Bell Burnell began her graduate studies in radio astronomy at Cambridge University. One of several research assistants and students working under astronomers Anthony Hewish, her thesis advisor, and Martin Ryle, over the next two years she helped construct a massive radio telescope designed to monitor quasars. By 1967, it was operational and Bell Burnell was tasked with analyzing the data it produced. After spending endless hours pouring over the charts, she noticed some anomalies that did not fit with the patterns produced by quasars and called them to Hewish’s attention.

    Over the ensuing months, the team systematically eliminated all possible sources of the radio pulses—which they affectionately labeled Little Green Men, in reference to their potentially artificial origins—until they were able to deduce that they were made by neutron stars, fast-spinning collapsed stars too small to form black holes.

    Pulsars and Nobel Prize Controversy

    Their findings were published in the February 1968 issue of Nature and caused an immediate sensation. Intrigued as much by the novelty of a woman scientist as by the astronomical significance of the team’s discovery, which was labeled pulsars—for pulsating radio stars—the press picked up the story and showered Bell Burnell with attention. That same year, she earned her Ph.D. in radio astronomy from Cambridge University.

    However, in 1974, only Hewish and Ryle received the Nobel Prize for Physics for their work. Many in the scientific community raised their objections, believing that Bell Burnell had been unfairly snubbed. However, Bell Burnell humbly rejected the notion, feeling that the prize had been properly awarded given her status as a graduate student, though she has also acknowledged that gender discrimination may have been a contributing factor.

    Life on the Electromagnetic Spectrum

    Nobel Prize or not, Bell Burnell’s depth of knowledge regarding radio astronomy and the electromagnetic spectrum has earned her a lifetime of respect in the scientific community and an esteemed career in academia. After receiving her doctorate from Cambridge, she taught and studied gamma ray astronomy at the University of Southampton. Bell Burnell then spent eight years as a professor at University College London, where she focused on x-ray astronomy.

    During this same time, she began her affiliation with Open University, where she would later work as a professor of physics while studying neurons and binary stars, and also conducted research in infrared astronomy at the Royal Observatory, Edinburgh. She was the Dean of Science at the University of Bath from 2001 to 2004, and has been a visiting professor at such esteemed institutions as Princeton University and Oxford University.

    Array of Honors and Achievements

    In recognition of her achievements, Bell Burnell has received countless awards and honors, including Commander and Dame of the Order of the British Empire in 1999 and 2007, respectively; an Oppenheimer prize in 1978; and the 1989 Herschel Medal from the Royal Astronomical Society, for which she would serve as president from 2002 to 2004. She was president of the Institute of Physics from 2008 to 2010, and has served as president of the Royal Society of Edinburgh since 2014. Bell Burnell also has honorary degrees from an array of universities too numerous to mention.

    Personal Life

    In 1968, Jocelyn married Martin Burnell, from whom she took her surname, with the two eventually divorcing in 1993. The two have a son, Gavin, who has also become a physicist.

    A documentary on Bell Burnell’s life, Northern Star, aired on the BBC in 2007.
    ______________________________________________

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

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  • richardmitnick 9:33 am on April 28, 2020 Permalink | Reply
    Tags: "Searching Pulsars for Planets", , , , , , Pulsars   

    From AAS NOVA: “Searching Pulsars for Planets” 

    AASNOVA

    From AAS NOVA

    27 April 2020
    Susanna Kohler

    1
    Artist’s illustration of a multi-planet system orbiting a millisecond pulsar. [NASA/JPL-Caltech/R. Hurt (SSC)]

    Are there more hidden exoplanets lurking around extreme pulsar hosts? A recent study explores a well-observed set of pulsars in the hunt for planetary companions.

    2
    An artist’s illustration showing a network of pulsars whose precisely timed flashes of light are observed from Earth. Could some of these pulsars host planets? [David Champion/NASA/JPL]

    Ushering in the Age of Exoplanets

    The first planets ever confirmed beyond our solar system were discovered in 1992 around the pulsar PSR B1257+12. By studying the pulses from this spinning, magnetized neutron star, scientists confirmed the presence of two small orbiting companions. Two years later, a third planet was found in the same system — and it seemed that pulsars showed great promise as hosts for exoplanets.

    But then the discoveries slowed. Other detection methods, such as radial velocity and transits, dominated the emerging exoplanet scene. Of the more than 4,000 confirmed exoplanets we’ve discovered overall, a grand total of only six have been found orbiting pulsars.

    Is this dearth because pulsar planets are extremely rare? Or have we just not performed enough systematic searches for pulsar planets? A new study led by Erica Behrens (The Ohio State University) addresses this question by using a unique dataset to explore rapidly spinning millisecond pulsars, looking for signs of hidden planets.

    The Advantage of Precise Clocks

    How are pulsar planets found? Pulsars have beams of hot radiation that flash across our line of sight each time they spin. The regularity of these flashes is remarkably stable, and when we observe them over long periods of time, we can predict the arrival time of the pulses with a precision of microseconds!

    4
    Sample periodograms for two pulsars. The top panel includes a simulated planet signal injected into the data, producing a strong peak at the planet’s orbital period. The bottom panel is an actual periodogram for one of the pulsars in this study, showing no evidence of a planetary companion. [Adapted from Behrens et al. 2020]

    Because these pulses are so predictable, any perturbation that might change their timing can be measured and modeled. In particular, the presence of a companion body around the pulsar will cause both objects to orbit the system’s center of mass, introducing a periodic signature in the pulsar’s pulse arrival times. This fluctuation in the pulse timing allows us to measure the period and mass of potential companions.

    A Multi-Use Dataset

    To search for these signatures in pulse data, Behrens and collaborators turn to observations of 45 separate millisecond pulsars, which were made as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project.

    NANOGrav’s primary goal is to use the precise timing of these pulsars to measure the warping of spacetime caused by gravitational waves. But in the process of this work, the project has been carefully monitoring pulse arrival times for these pulsars for 11 years, producing a remarkably detailed dataset in which we can search for evidence of planets orbiting any of the 45 pulsars.

    5
    Lower limits of detectable masses in the 11-year NANOGrav data set, as shown with black lines. The colored data shows the masses of the least massive 10% of confirmed exoplanets we’ve detected with other methods. Pulsar timing provides the ability to detect remarkably low-mass companion bodies.[Behrens et al. 2020]

    Pushing Down to Moon Masses

    Looking for periodic signals in the data, Behrens and collaborators rule out the presence of planets that have periods between 7 and 2,000 days. By injecting simulated signals into the data, the authors show that their analysis is sensitive to companions with masses of less than the Earth — in fact, for some pulsars, they’ve eliminated the possibility of all companions with more than a fraction of the mass of our Moon!

    This study shows the incredible power and sensitivity of extended pulsar monitoring in the hunt for small exoplanets. While it may well be true that pulsar planets are very rare objects, those out there can’t stay hidden for long.

    Citation

    “The NANOGrav 11 yr Data Set: Constraints on Planetary Masses Around 45 Millisecond Pulsars,” E. A. Behrens et al 2020 ApJL 893 L8.

    https://iopscience.iop.org/article/10.3847/2041-8213/ab8121

    __________________________________________________________
    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Biography

    British astrophysicist, scholar and trailblazer Jocelyn Bell Burnell discovered the space-based phenomena known as pulsars, going on to establish herself as an esteemed leader in her field.Who Is Jocelyn Bell Burnell?
    Jocelyn Bell Burnell is a British astrophysicist and astronomer. As a research assistant, she helped build a large radio telescope and discovered pulsars, providing the first direct evidence for the existence of rapidly spinning neutron stars. In addition to her affiliation with Open University, she has served as dean of science at the University of Bath and president of the Royal Astronomical Society. Bell Burnell has also earned countless awards and honors during her distinguished academic career.

    Early Life

    Jocelyn Bell Burnell was born Susan Jocelyn Bell on July 15, 1943, in Belfast, Northern Ireland. Her parents were educated Quakers who encouraged their daughter’s early interest in science with books and trips to a nearby observatory. Despite her appetite for learning, however, Bell Burnell had difficulty in grade school and failed an exam intended to measure her readiness for higher education.

    Undeterred, her parents sent her to England to study at a Quaker boarding school, where she quickly distinguished herself in her science classes. Having proven her aptitude for higher learning, Bell Burnell attended the University of Glasgow, where she earned a bachelor’s degree in physics in 1965.

    Little Green Men

    In 1965, Bell Burnell began her graduate studies in radio astronomy at Cambridge University. One of several research assistants and students working under astronomers Anthony Hewish, her thesis advisor, and Martin Ryle, over the next two years she helped construct a massive radio telescope designed to monitor quasars. By 1967, it was operational and Bell Burnell was tasked with analyzing the data it produced. After spending endless hours pouring over the charts, she noticed some anomalies that did not fit with the patterns produced by quasars and called them to Hewish’s attention.

    Over the ensuing months, the team systematically eliminated all possible sources of the radio pulses—which they affectionately labeled Little Green Men, in reference to their potentially artificial origins—until they were able to deduce that they were made by neutron stars, fast-spinning collapsed stars too small to form black holes.

    Pulsars and Nobel Prize Controversy

    Their findings were published in the February 1968 issue of Nature and caused an immediate sensation. Intrigued as much by the novelty of a woman scientist as by the astronomical significance of the team’s discovery, which was labeled pulsars—for pulsating radio stars—the press picked up the story and showered Bell Burnell with attention. That same year, she earned her Ph.D. in radio astronomy from Cambridge University.

    However, in 1974, only Hewish and Ryle received the Nobel Prize for Physics for their work. Many in the scientific community raised their objections, believing that Bell Burnell had been unfairly snubbed. However, Bell Burnell humbly rejected the notion, feeling that the prize had been properly awarded given her status as a graduate student, though she has also acknowledged that gender discrimination may have been a contributing factor.

    Life on the Electromagnetic Spectrum

    Nobel Prize or not, Bell Burnell’s depth of knowledge regarding radio astronomy and the electromagnetic spectrum has earned her a lifetime of respect in the scientific community and an esteemed career in academia. After receiving her doctorate from Cambridge, she taught and studied gamma ray astronomy at the University of Southampton. Bell Burnell then spent eight years as a professor at University College London, where she focused on x-ray astronomy.

    During this same time, she began her affiliation with Open University, where she would later work as a professor of physics while studying neurons and binary stars, and also conducted research in infrared astronomy at the Royal Observatory, Edinburgh. She was the Dean of Science at the University of Bath from 2001 to 2004, and has been a visiting professor at such esteemed institutions as Princeton University and Oxford University.

    Array of Honors and Achievements

    In recognition of her achievements, Bell Burnell has received countless awards and honors, including Commander and Dame of the Order of the British Empire in 1999 and 2007, respectively; an Oppenheimer prize in 1978; and the 1989 Herschel Medal from the Royal Astronomical Society, for which she would serve as president from 2002 to 2004. She was president of the Institute of Physics from 2008 to 2010, and has served as president of the Royal Society of Edinburgh since 2014. Bell Burnell also has honorary degrees from an array of universities too numerous to mention.

    Personal Life

    In 1968, Jocelyn married Martin Burnell, from whom she took her surname, with the two eventually divorcing in 1993. The two have a son, Gavin, who has also become a physicist.

    A documentary on Bell Burnell’s life, Northern Star, aired on the BBC in 2007.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 10:57 am on April 18, 2020 Permalink | Reply
    Tags: , , , , , Dame Susan Jocelyn Bell Burnell discovered of the first pulsar in 1967., , PSR J1717+408A, Pulsars, Pulsars are the compact remnants of dead stars that shine powerful beams of emission into space as they spin.,   

    From AAS NOVA: “Pulsar Discovery from an Enormous Telescope” 

    AASNOVA

    From AAS NOVA

    17 April 2020
    Susanna Kohler

    FAST [Five-hundred-meter Aperture Spherical Telescope] radio telescope, with phased arrays from CSIRO engineers Australia [located in the Dawodang depression in Pingtang County, Guizhou Province, south China

    Magnetized neutron stars in distant globular clusters are a challenge to detect — but it’s a job made easier by the world’s largest filled-aperture radio telescope. Recent high-sensitivity observations have uncovered an erratic new star system.

    Pulses from Distant Clusters

    Pulsars are the compact remnants of dead stars that shine powerful beams of emission into space as they spin.

    The brightness of these beams and the regular timing of their pulsations makes pulsars valuable targets for observatories; not only can they tell us about stellar evolution and their environments, but they also serve as probes of the interstellar medium, space-time, and more.

    Since the discovery of the first pulsar in 1967, we’ve found thousands of these stellar clocks in our galaxy.

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    While many are located relatively nearby in the galactic disk, we’ve also observed a population of pulsars in the distant globular clusters that orbit the Milky Way. These pulsars are a useful tool for probing a very different environment: the dense stellar cores made up of an old population of stars.

    Until recently, we’d only discovered 156 pulsars in 29 globular clusters; due to these clusters’ large distances (tens to hundreds of thousands of light-years away), it takes very powerful and sensitive radio telescopes to find them using deep surveys. Now, a new observatory has entered the game.

    A Powerful Telescope

    The Five-hundred-meter Aperture Spherical radio Telescope (FAST), built into the hilly landscape in southwest China, is the world’s largest filled-aperture telescope. Its size dwarfs that of the Arecibo Observatory in Puerto Rico, and its dish has the advantage of being shapable — the panels that make up its surface can be tilted by a computer to change the telescope’s focus.


    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

    2
    Comparison of the FAST (bottom) and Arecibo Observatory (top) radio dish profiles at the same scale. [Cmglee]

    FAST achieved first light in 2016, and it’s been going undergoing testing and commissioning for the last few years. As of January 2020, the FAST is officially open for business, and we’re now seeing some of the major results coming from this powerful radio observatory.

    Among them: the first discovery of an eclipsing binary pulsar in globular cluster M92, as reported in a recent publication led by Zichen Pan (NAO, Chinese Academy of Sciences).

    3
    Hubble image of the globular cluster M92. [ESA/Hubble]

    4
    Phase-folded pulse data for PSR J1717+408A, as observed by FAST (left panel) and by the Green Bank Telescope (right panel). Eclipses are visible as breaks in the data. The difference in sensitivity between the two telescopes is starkly evident. [Adapted from Pan et al. 2020]



    GBO radio telescope, Green Bank, West Virginia, USA

    An Exotic System

    Pan and collaborators announce the FAST detection of a pulsar with a pulse period of 3.16 milliseconds orbiting around a low-mass companion in a globular cluster that’s about 27,000 light-years away.

    This pulsar, PSR J1717+408A, is in a close (period of 0.20 days) eclipsing orbit with its companion, making it what’s known as a “red-back pulsar”. Radiation from the pulsar has pummeled its companion star, creating a cloud of ionized material that surrounds it and causes the pulsar’s eclipses to vary in duration and timing.

    The discovery of this object demonstrates the potential of FAST as a probe of the globular cluster pulsar population. More observations of M92 are planned in the future, as well as observations of dozens of even richer clusters. Keep an eye out for more FAST results as this telescope ramps up operations!

    Citation

    “The FAST Discovery of an Eclipsing Binary Millisecond Pulsar in the Globular Cluster M92 (NGC 6341),” Zhichen Pan et al 2020 ApJL 892 L6.

    https://iopscience.iop.org/article/10.3847/2041-8213/ab799d

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 3:34 pm on February 12, 2020 Permalink | Reply
    Tags: "What is a neutron star?", , , , , , , Pulsars   

    From EarthSky: “What is a neutron star?” And Dame Susan Jocelyn Bell Burnell Who Discovered Pulsars 

    1

    From EarthSky

    February 12, 2020
    Andy Briggs

    1
    Artist’s concept of a neutron star. The star’s tiny size and extreme density give it incredibly powerful gravity at its surface. Thus this image portrays the space around the neutron star as being curved. Image via Raphael.concorde/ Daniel Molybdenum/ NASA/ Wikimedia Commons.

    When – at the end of its life – a massive star explodes as a supernova, its core can collapse to end up as a tiny and superdense object with not much more than our sun’s mass. These small, incredibly dense cores of exploded stars are neutron stars. They’re among the most bizarre objects in the universe.

    A typical neutron star has about about 1.4 times our sun’s mass, but they range up to about two solar masses. Now consider that our sun has about 100 times Earth’s diameter. In a neutron star, all its large mass – up to about twice as much as our sun’s – is squeezed into a star that’s only about 10 miles (15 km) across, or about the size of an earthly city.

    So perhaps you can see that neutron stars are very, very dense! A tablespoon of neutron star material would weigh more than 1 billion U.S. tons (900 billion kg). That’s more than the weight of Mount Everest, Earth’s highest mountain.

    2
    Neutron stars are the collapsed cores of massive stars. They pack roughly the mass of our sun into a sphere with the diameter of a city. Here’s a comparison of a neutron star’s typical diameter with the city of Chicago. Graphic via M. Coleman Miller.

    Here’s how neutron stars form. Throughout much of their lives, stars maintain a delicate balancing act. Gravity tries to compress the star while the star’s internal pressure exerts an outward push. The outward pressure is caused by nuclear fusion at the star’s core. This fusion “burning” is the process by which stars shine.

    In a supernova explosion, gravity suddenly and catastrophically gets the upper hand in the war it has been waging with the star’s internal pressure for millions or billions of years. With its nuclear fuel exhausted and the outward pressure removed, gravity suddenly compresses the star inward. A shock wave travels to the core and rebounds, blowing the star apart. This whole process takes perhaps a couple of seconds.

    But gravity’s victory is not yet complete. With most of the star blown into space, the core remains, which may only possess a couple of times the mass of our sun. Gravity continues to compress it, to a point where the atoms become so compacted and so close together that electrons are violently thrust into their parent nuclei, combining with the protons to form neutrons.

    Thus the neutron star gets its name from its composition. What gravity has created is a superdense, neutron-rich material – called neutronium – in a city-sized sphere.


    Ask a Spaceman: Neutron star weirdness

    What neutron stars are, and are not. If, after the supernova, the core of the star has enough mass, then – according to current understanding – the gravitational collapse will continue. A black hole will form instead of a neutron star. In terms of mass, the dividing line between neutron stars and black holes is the subject of much debate. Astrophysicists refer to a kind of “missing mass,” occurring between about two solar masses (the theoretical maximum mass of a neutron star) and five solar masses (the theoretical minimum mass of a black hole). Some expect that this mass bracket will eventually be found to be populated by ultra-lightweight black holes, but until now none have been found.

    The exact internal structure of a neutron star is also the subject of much debate. Current thinking is that the star possesses a thin crust of iron, perhaps a mile or so thick. Under that, the composition is largely neutrons, taking various forms the further down in the neutron star they are.

    A neutron star does not generate any light or heat of its own after its formation. Over millions of years its latent heat will gradually cool from an intial 600,000 degrees Kelvin (1 million degrees Fahrenheit), eventually ending its life as the cold, dead remnant of a once-glorious star.

    Because neutron stars are so dense, they have intense gravitational and magnetic fields. The gravity of a neutron star is about a thousand billion times stronger than that of the Earth. Thus the surface of a neutron star is exceedingly smooth; gravity does not permit anything tall to exist. Neutron stars are thought to have “mountains,” but they are only inches tall.

    Pulsars: How we know about neutron stars. Although neutron stars were long predicted in astrophysical theory, it wasn’t until 1967 that the first was discovered, as a pulsar, by Dame Susan Jocelyn Bell Burnell. Since then, hundreds more have been discovered, including the famous pulsar at the heart of the Crab Nebula, a supernova remnant seen to explode by the Chinese in 1054.

    Supernova remnant Crab nebula. NASA/ESA Hubble

    X-ray picture of Crab pulsar, taken by NASA/Chandra

    On a neutron star, intense magnetic fields focus radio waves into two beams firing into space from its magnetic poles, much like the beam of a lighthouse. If the object is oriented just so with respect to Earth – so that these beams become visible from our earthly viewpoint – we see flashes of radio light at regular and extremely precise intervals. Neutron stars are, in fact, the celestial timekeepers of the cosmos, their accuracy rivalling that of atomic clocks.

    3
    Anatomy of a pulsar. They are neutron stars that are oriented in a particular way with respect to Earth, so that we see them “pulse” at regular intervals. Image via Roen Kelly/ Discovermagazine.com.

    Read more about Dame Susan Jocelyn Bell Burnell, who discovered pulsars

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    Biography

    British astrophysicist, scholar and trailblazer Jocelyn Bell Burnell discovered the space-based phenomena known as pulsars, going on to establish herself as an esteemed leader in her field.Who Is Jocelyn Bell Burnell?
    Jocelyn Bell Burnell is a British astrophysicist and astronomer. As a research assistant, she helped build a large radio telescope and discovered pulsars, providing the first direct evidence for the existence of rapidly spinning neutron stars. In addition to her affiliation with Open University, she has served as dean of science at the University of Bath and president of the Royal Astronomical Society. Bell Burnell has also earned countless awards and honors during her distinguished academic career.

    Early Life

    Jocelyn Bell Burnell was born Susan Jocelyn Bell on July 15, 1943, in Belfast, Northern Ireland. Her parents were educated Quakers who encouraged their daughter’s early interest in science with books and trips to a nearby observatory. Despite her appetite for learning, however, Bell Burnell had difficulty in grade school and failed an exam intended to measure her readiness for higher education.

    Undeterred, her parents sent her to England to study at a Quaker boarding school, where she quickly distinguished herself in her science classes. Having proven her aptitude for higher learning, Bell Burnell attended the University of Glasgow, where she earned a bachelor’s degree in physics in 1965.

    Little Green Men

    In 1965, Bell Burnell began her graduate studies in radio astronomy at Cambridge University. One of several research assistants and students working under astronomers Anthony Hewish, her thesis advisor, and Martin Ryle, over the next two years she helped construct a massive radio telescope designed to monitor quasars. By 1967, it was operational and Bell Burnell was tasked with analyzing the data it produced. After spending endless hours pouring over the charts, she noticed some anomalies that did not fit with the patterns produced by quasars and called them to Hewish’s attention.

    Over the ensuing months, the team systematically eliminated all possible sources of the radio pulses—which they affectionately labeled Little Green Men, in reference to their potentially artificial origins—until they were able to deduce that they were made by neutron stars, fast-spinning collapsed stars too small to form black holes.

    Pulsars and Nobel Prize Controversy

    Their findings were published in the February 1968 issue of Nature and caused an immediate sensation. Intrigued as much by the novelty of a woman scientist as by the astronomical significance of the team’s discovery, which was labeled pulsars—for pulsating radio stars—the press picked up the story and showered Bell Burnell with attention. That same year, she earned her Ph.D. in radio astronomy from Cambridge University.

    However, in 1974, only Hewish and Ryle received the Nobel Prize for Physics for their work. Many in the scientific community raised their objections, believing that Bell Burnell had been unfairly snubbed. However, Bell Burnell humbly rejected the notion, feeling that the prize had been properly awarded given her status as a graduate student, though she has also acknowledged that gender discrimination may have been a contributing factor.

    Life on the Electromagnetic Spectrum

    Nobel Prize or not, Bell Burnell’s depth of knowledge regarding radio astronomy and the electromagnetic spectrum has earned her a lifetime of respect in the scientific community and an esteemed career in academia. After receiving her doctorate from Cambridge, she taught and studied gamma ray astronomy at the University of Southampton. Bell Burnell then spent eight years as a professor at University College London, where she focused on x-ray astronomy.

    During this same time, she began her affiliation with Open University, where she would later work as a professor of physics while studying neurons and binary stars, and also conducted research in infrared astronomy at the Royal Observatory, Edinburgh. She was the Dean of Science at the University of Bath from 2001 to 2004, and has been a visiting professor at such esteemed institutions as Princeton University and Oxford University.

    Array of Honors and Achievements

    In recognition of her achievements, Bell Burnell has received countless awards and honors, including Commander and Dame of the Order of the British Empire in 1999 and 2007, respectively; an Oppenheimer prize in 1978; and the 1989 Herschel Medal from the Royal Astronomical Society, for which she would serve as president from 2002 to 2004. She was president of the Institute of Physics from 2008 to 2010, and has served as president of the Royal Society of Edinburgh since 2014. Bell Burnell also has honorary degrees from an array of universities too numerous to mention.

    Personal Life

    In 1968, Jocelyn married Martin Burnell, from whom she took her surname, with the two eventually divorcing in 1993. The two have a son, Gavin, who has also become a physicist.

    A documentary on Bell Burnell’s life, Northern Star, aired on the BBC in 2007.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

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

     
  • richardmitnick 3:47 pm on January 30, 2020 Permalink | Reply
    Tags: "Astronomers witness the dragging of space-time in stellar cosmic dance", , , , , If Einstein was right (Theory of General Relativity) all rotating bodies should 'drag' the very fabric of space time around with them., OzGrav ARC Centre of Excellence, , Pulsars,   

    From Swinburne University of Technology via phys.org: “Astronomers witness the dragging of space-time in stellar cosmic dance” 

    Swinburne U bloc

    From Swinburne University of Technology

    via


    phys.org

    1
    Artist’s depiction of ‘frame-dragging’: two spinning stars twisting space and time. Credit: Mark Myers, OzGrav ARC Centre of Excellence.

    An international team of astrophysicists led by Australian Professor Matthew Bailes, from the ARC Centre of Excellence of Gravitational Wave Discovery (OzGrav), has shown exciting new evidence for ‘frame-dragging’—how the spinning of a celestial body twists space and time—after tracking the orbit of an exotic stellar pair for almost two decades. The data, which is further evidence for Einstein’s theory of General Relativity, is published today the journal Science.

    More than a century ago, Albert Einstein published his iconic theory of General Relativity—that the force of gravity arises from the curvature of space and time and that objects, such as the Sun and the Earth, change this geometry. Advances in instrumentation have led to a flood of recent (Nobel prize-winning) science from phenomena further afield linked to General Relativity. The discovery of gravitational waves was announced in 2016; the first image of a black hole shadow and stars orbiting the supermassive black hole at the centre of our own galaxy was published just last year.

    Almost 20 years ago, a team led by Swinburne University of Technology’s Professor Bailes—director of the ARC Centre of Excellence in Gravitational Wave Discovery (OzGrav)—started observing two stars rotating around each other at astonishing speeds with the CSIRO Parkes 64-metre radio telescope. One is a white dwarf, the size of the Earth but 300,000 times its density; the other is a neutron star which, while only 20 kilometres in diameter, is about 100 billion times the density of the Earth. The system, which was discovered at Parkes, is a relativistic-wonder system that goes by the name “PSR J1141-6545.”

    Before the star blew up (becoming a neutron star), a million or so years ago, it began to swell up discarding its outer core which fell onto the white dwarf nearby. This falling debris made the white dwarf spin faster and faster, until its day was only measured in terms of minutes.

    In 1918 (three years after Einstein published his Theory), Austrian mathematicians Josef Lense and Hans Thirring realised that if Einstein was right all rotating bodies should ‘drag’ the very fabric of space time around with them. In everyday life, the effect is miniscule and almost undetectable. Earlier this century, the first experimental evidence for this effect was seen in gyroscopes orbiting the Earth, whose orientation was dragged in the direction of the Earth’s spin. A rapidly spinning white dwarf, like the one in PSR J1141-6545, drags space-time 100 million times as strongly!

    A pulsar in orbit around such a white dwarf presents a unique opportunity to explore Einstein’s theory in a new ultra-relativistic regime.

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    3
    Artist’s depiction of a rapidly spinning neutron star and a white dwarf dragging the fabric of space time around its orbit. Credit: Mark Myers, OzGrav ARC Centre of Excellence.

    Lead author of the current study, Dr. Vivek Venkatraman Krishnan (from Max Planck Institute for Radio Astronomy—MPIfR) was given the unenviable task of untangling all of the competing relativistic effects at play in the system as part of his Ph.D. at Swinburne University of Technology. He noticed that unless he allowed for a gradual change in the orientation of the plane of the orbit, General Relativity made no sense.

    MPIfR’s Dr. Paulo Friere realised that frame-dragging of the entire orbit could explain their tilting orbit and the team presents compelling evidence in support of this in today’s journal article—it shows that General Relativity is alive and well, exhibiting yet another of its many predictions.

    The result is especially pleasing for team members Bailes, Willem van Straten (Auckland University of Tech) and Ramesh Bhat (ICRAR-Curtin) who have been trekking out to the Parkes 64m telescope since the early 2000s, patiently mapping the orbit with the ultimate aim of studying Einstein’s Universe. “This makes all the late nights and early mornings worthwhile,” said Bhat.

    Expert commentary:

    Lead author Vivek Venkatraman Krishnan, Max Planck Institute for Radio Astronomy (MPIfR): “At first, the stellar pair appeared to exhibit many of the classic effects that Einstein’s theory predicted. We then noticed a gradual change in the orientation of the plane of the orbit.”

    “Pulsars are cosmic clocks. Their high rotational stability means that any deviation to the expected arrival time of its pulses is probably due to the pulsar’s motion or due to the electrons and magnetic fields that the pulses encounter. Pulsar timing is a powerful technique where we use atomic clocks at radio telescopes to estimate the arrival time of the pulses from the pulsar to very high precision. The motion of the pulsar in its orbit modulates the arrival time, thereby enabling its measurement.”


    Dragging the Space-time Continuum

    Dr. Paulo Freire: “We postulated that this might be, at least in-part, due to the so-called ‘frame-dragging’ that all matter is subject to in the presence of a rotating body as predicted by the Austrian mathematicians Lense and Thirring in 1918.”

    Professor Thomas Tauris, Aarhus University: “In a stellar pair, the first star to collapse is often rapidly rotating due to subsequent mass transfer from its companion. Tauris’s simulations helped quantify the magnitude of the white dwarf’s spin. In this system the entire orbit is being dragged around by the white dwarf’s spin, which is misaligned with the orbit.”

    Dr. Norbert Wex, Max Planck Institute for Radio Astronomy (MPIfR): “One of the first confirmations of frame-dragging used four gyroscopes in a satellite in orbit around the Earth, but in our system the effects are 100 million times stronger.”

    Evan Keane (SKA Organisation): “Pulsars are super clocks in space. Super clocks in strong gravitational fields are Einstein’s dream laboratories. We have been studying one of the most unusual of these in this binary star system. Treating the periodic pulses of light from the pulsar like the ticks of a clock we can see and disentangle many gravitational effects as they change the orbital configuration, and the arrival time of the clock-tick pulses. In this case we have seen Lens-Thirring precession, a prediction of General Relativity, for the first time in any stellar system.”

    Willem van Straten (AUT): “After ruling out a range of potential experimental errors, we started to suspect that the interaction between the white dwarf and neutron star was not as simple as had been assumed to date.”

    See the full article here .

    Please help promote STEM in your local schools.


    Stem Education Coalition

    About Science X in 100 words

    Science X™ is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004 (Physorg.com), Science X’s readership has grown steadily to include 5 million scientists, researchers, and engineers every month. Science X publishes approximately 200 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Science X community members enjoy access to many personalized features such as social networking, a personal home page set-up, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.
    Mission 12 reasons for reading daily news on Science X Organization Key editors and writersinclude 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

    Swinburne U Campus

    Swinburne University of Technology (often simply called Swinburne) is an Australian public university based in Melbourne, Victoria. It was founded in 1908 as the Eastern Suburbs Technical College by George Swinburne in order to serve those without access to further education in Melbourne’s eastern suburbs. Its main campus is located in Hawthorn, a suburb of Melbourne which is located 7.5 km from the Melbourne central business district.

    In addition to its main Hawthorn campus, Swinburne has campuses in the Melbourne metropolitan area at Wantirna and Croydon as well as a campus in Sarawak, Malaysia.
    In the 2016 QS World University Rankings, Swinburne was ranked 32nd for art and design, making it one of the top art and design schools in Australia and the world.

     
  • richardmitnick 10:08 am on December 18, 2019 Permalink | Reply
    Tags: , , , Pulsar J0030, Pulsars   

    From NASA via EarthSky: “Scientists map a pulsar for the 1st time” 

    From NASA

    via

    1

    EarthSky

    Using a revolutionary X-ray telescope aboard the International Space Station, scientists have finally created the 1st pulsar surface “map.” It shows odd hot spots and suggests that pulsar magnetic fields are more complicated than anyone had assumed.

    NASA/NICER on the ISS

    1
    New “map” of hotspots on pulsar J0030, from observations from July 2017 to December 2018. Image via Goddard Space Flight Center/ NASA.

    Pulsars – the extremely dense but tiny remnants of exploded stars – have been known for decades, but remain one of the most enigmatic phenomena in the known universe. They’re not easy to study, in part due to their immense distances. Now, using a special X-ray telescope launched to the International Space Station (ISS) in 2017, scientists have been able to map a pulsar and take precise measurements of its size and mass, for the first time. These momentous findings also include odd hot spots on the pulsar’s surface.

    NASA announced the findings on December 12, 2019, and these results have been published in a series of new peer-reviewed papers in a special issue of The Astrophysical Journal Letters.

    The study focuses on a pulsar called J0030+0451 (J0030), in an isolated region of space 1,100 light-years away in the direction of the constellation Pisces.

    Astrophysicist Paul Hertz, at NASA headquarters, said in a statement that, from its perch above Earth aboard ISS, NASA’s NICER telescope – which stands for Neutron star Interior Composition Explorer – is revolutionizing our understanding of pulsars:

    “Pulsars were discovered more than 50 years ago as beacons of stars that have collapsed into dense cores, behaving unlike anything we see on Earth. With NICER we can probe the nature of these dense remnants in ways that seemed impossible until now.”

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    The researchers – two groups of scientists – used NICER observations from July 2017 to December 2018, and came up with similar results for the size and mass of the pulsar, as well as hot spots on its surface.

    With the help of computer simulations, NICER found three million-degree hot spots on the pulsar, all in its southern hemisphere, but the spots didn’t look like what textbooks had predicted. One spot was small and circular, while another was longer and crescent-shaped. The third spot, a bit cooler, was slightly askew of the pulsar’s south rotational pole. Previous models had suggested that the locations and shapes of the spots would vary more.

    This is the first time that such surface features have been positively identified on a pulsar. The findings indicate that pulsar magnetic fields are more complicated than the traditional two-pole model had implied.

    3
    Simulation of a possible quadrupole magnetic field configuration – 2 pairs of oppositely charged poles – for a pulsar with hot spots only in its southern hemisphere. The new pulsar map suggests that pulsar magnetic fields are more complicated than anyone knew. Image via Goddard Space Flight Center/ NASA.

    NICER was also able to determine a pulsar’s size and mass much more accurately than ever before.

    One of the research teams, led by Thomas Riley, a doctoral student in computational astrophysics, and his supervisor Anna Watts, a professor of astrophysics at the University of Amsterdam, found that the pulsar is about 1.3 times the sun’s mass and 15.8 miles (25.4 km) across.

    The second team, led by Cole Miller, an astronomy professor at the University of Maryland, came up with very similar results: 1.4 times the sun’s mass and about 16.2 miles (26 km) wide. Riley said:

    “When we first started working on J0030, our understanding of how to simulate pulsars was incomplete, and it still is. But thanks to NICER’s detailed data, open-source tools, high-performance computers and great teamwork, we now have a framework for developing more realistic models of these objects.”

    Miller said:

    “NICER’s unparalleled X-ray measurements allowed us to make the most precise and reliable calculations of a pulsar’s size to date, with an uncertainty of less than 10%. The whole NICER team has made an important contribution to fundamental physics that is impossible to probe in terrestrial laboratories.”

    NICER is so accurate it can measure the arrival of each X-ray from a pulsar to better than a hundred nanoseconds (one nanosecond is a billionth of a second). That precision is about 20 times greater than any previously available.

    Pulsars are the rapidly spinning, dense and tiny remnants of stars that exploded in a supernova. They are one type of neutron star and can spin up to hundreds of times per second, sweeping beams of radiation energy toward us with every rotation. J0030 revolves 205 times per second.

    Pulsars are unimaginably dense; their gravity actually warps nearby space-time, the “fabric” of the universe as described by Einstein’s general theory of relativity. Their rotations are so regular, that it was first thought that they might be evidence of extraterrestrial intelligence, until it was determined they were a natural phenomenon.

    Scientists now want to determine the masses and sizes of several more pulsars besides J0030. By doing so, they can better understand the state of matter in the cores of such neutron stars. The pressures and densities are well beyond anything that can be replicated in laboratories on Earth. According to Zaven Arzoumanian, NICER science lead at NASA’s Goddard Space Flight Center:

    “It’s remarkable, and also very reassuring, that the two teams achieved such similar sizes, masses and hot spot patterns for J0030 using different modeling approaches. It tells us NICER is on the right path to help us answer an enduring question in astrophysics: What form does matter take in the ultra-dense cores of neutron stars?”

    The new findings are a breakthrough in pulsar and neutron star research, and will help scientists learn more about these very mysterious objects. For more, check out the video below.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 5:00 pm on November 7, 2019 Permalink | Reply
    Tags: "NASA's NICER Catches Record-setting X-ray Burst", , , , , , Pulsars, SAX J1808.4-3658   

    From NASA: “NASA’s NICER Catches Record-setting X-ray Burst” 

    NASA image
    From NASA

    Nov. 7, 2019

    Francis Reddy
    francis.j.reddy@nasa.gov
    NASA’s Goddard Space Flight Center, Greenbelt, Md.

    1
    Illustration depicting a Type I X-ray burst. The explosion first blows off the hydrogen layer, which expands and ultimately dissipates. Then rising radiation builds to the point where it blows off the helium layer, which overtakes the expanding hydrogen. Some of the X-rays emitted in the blast scatter off of the accretion disk. The fireball then quickly cools, and the helium settles back onto the surface. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA)

    NASA/NICER on the ISS

    NASA’s Neutron star Interior Composition Explorer (NICER) telescope on the International Space Station detected a sudden spike of X-rays at about 10:04 p.m. EDT on Aug. 20. The burst was caused by a massive thermonuclear flash on the surface of a pulsar, the crushed remains of a star that long ago exploded as a supernova.

    The X-ray burst, the brightest seen by NICER so far, came from an object named SAX J1808.4-3658, or J1808 for short. The observations reveal many phenomena that have never been seen together in a single burst. In addition, the subsiding fireball briefly brightened again for reasons astronomers cannot yet explain.

    “This burst was outstanding,” said lead researcher Peter Bult, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park. “We see a two-step change in brightness, which we think is caused by the ejection of separate layers from the pulsar surface, and other features that will help us decode the physics of these powerful events.”

    The explosion, which astronomers classify as a Type I X-ray burst, released as much energy in 20 seconds as the Sun does in nearly 10 days. The detail NICER captured on this record-setting eruption will help astronomers fine-tune their understanding of the physical processes driving the thermonuclear flare-ups of it and other bursting pulsars.


    A thermonuclear blast on a pulsar called J1808 resulted in the brightest burst of X-rays seen to date by NASA’s Neutron star Interior Composition Explorer (NICER) telescope. The explosion occurred on Aug. 20, 2019, and released as much energy in 20 seconds as our Sun does in almost 10 days. Watch to see how scientists think this incredible explosion occurred. Credits: NASA’s Goddard Space Flight Center

    A pulsar is a kind of neutron star, the compact core left behind when a massive star runs out of fuel, collapses under its own weight, and explodes. Pulsars can spin rapidly and host X-ray-emitting hot spots at their magnetic poles. As the object spins, it sweeps the hot spots across our line of sight, producing regular pulses of high-energy radiation.

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    J1808 is located about 11,000 light-years away in the constellation Sagittarius. It spins at a dizzying 401 rotations each second, and is one member of a binary system. Its companion is a brown dwarf, an object larger than a giant planet yet too small to be a star. A steady stream of hydrogen gas flows from the companion toward the neutron star, and it accumulates in a vast storage structure called an accretion disk.

    Gas in accretion disks doesn’t move inward easily. But every few years, the disks around pulsars like J1808 become so dense that a large amount of the gas becomes ionized, or stripped of its electrons. This makes it more difficult for light to move through the disk. The trapped energy starts a runaway process of heating and ionization that traps yet more energy. The gas becomes more resistant to flow and starts spiraling inward, ultimately falling onto the pulsar.

    Hydrogen raining onto the surface forms a hot, ever-deepening global “sea.” At the base of this layer, temperatures and pressures increase until hydrogen nuclei fuse to form helium nuclei, which produces energy — a process at work in the core of our Sun.

    “The helium settles out and builds up a layer of its own,” said Goddard’s Zaven Arzoumanian, the deputy principal investigator for NICER and a co-author of the paper. “Once the helium layer is a few meters deep, the conditions allow helium nuclei to fuse into carbon. Then the helium erupts explosively and unleashes a thermonuclear fireball across the entire pulsar surface.”

    Astronomers employ a concept called the Eddington limit — named for English astrophysicist Sir Arthur Eddington — to describe the maximum radiation intensity a star can have before that radiation causes the star to expand. This point depends strongly on the composition of the material lying above the emission source.

    “Our study exploits this longstanding concept in a new way,” said co-author Deepto Chakrabarty, a professor of physics at the Massachusetts Institute of Technology in Cambridge. “We are apparently seeing the Eddington limit for two different compositions in the same X-ray burst. This is a very powerful and direct way of following the nuclear burning reactions that underlie the event.”

    As the burst started, NICER data show that its X-ray brightness leveled off for almost a second before increasing again at a slower pace. The researchers interpret this “stall” as the moment when the energy of the blast built up enough to blow the pulsar’s hydrogen layer into space.

    The fireball continued to build for another two seconds and then reached its peak, blowing off the more massive helium layer. The helium expanded faster, overtook the hydrogen layer before it could dissipate, and then slowed, stopped and settled back down onto the pulsar’s surface. Following this phase, the pulsar briefly brightened again by roughly 20 percent for reasons the team does not yet understand.

    During J1808’s recent round of activity, NICER detected another, much fainter X-ray burst that displayed none of the key features observed in the Aug. 20 event.

    In addition to detecting the expansion of different layers, NICER observations of the blast reveal X-rays reflecting off of the accretion disk and record the flickering of “burst oscillations” — X-ray signals that rise and fall at the pulsar’s spin frequency but that occur at different surface locations than the hot spots responsible for its normal X-ray pulses.

    A paper describing the findings has been published by The Astrophysical Journal Letters.

    NICER is an Astrophysics Mission of Opportunity within NASA’s Explorer program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined, and efficient management approaches within the heliophysics and astrophysics science areas. NASA’s Space Technology Mission Directorate supports the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA] Greenhouse Gases Observing Satellite.

     
  • richardmitnick 1:22 pm on October 22, 2019 Permalink | Reply
    Tags: "A chance encounter with a pulsar", , , , , , , Pulsars   

    From CSIROscope: “A chance encounter with a pulsar” 

    CSIRO bloc

    From CSIROscope

    22 October 2019
    Louise Jeckells

    1
    The ASKAP radio telescope in all it’s glory.

    When you think you’ve seen it all, look again – there might be a pulsar staring back at you.

    Our scientists accidentally stumbled upon a pulsar, which is not an easy, or simple, task.

    Ok, hold on – what is a pulsar?

    When a giant star explodes, the core it leaves behind is a neutron star
    Neutron stars are roughly 10 km in radius and about 1.4 times heavier than the Sun
    A teaspoon of neutron star material would weigh about 10 million tons
    A highly-magnetized rotating neutron star that emits a beam of electromagnetic radiation (think of a lighthouse) is a pulsar.

    Astrophysicist Jocelyn Bell Burnell discovered the first pulsar in 1967.

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Today, astronomers have discovered most of the brighter and slower pulsars using large telescopes like our Parkes Radio Telescope (aka The Dish).

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

    Emil Lenc is a research scientist with our Astronomy and Space Science team. He’s not a pulsar astronomer. Emil works on the Australian Square Kilometre Array Pathfinder (ASKAP) in remote Western Australia. His job is to put the telescope through its paces. To experiment with innovative ways to process telescope data.

    SKA Square Kilometer Array

    But Emil, alongside a group of other scientists, discovered one of these highly-magnetized rotating neutron stars. It’s called PSR J1431-6328. Very creative.

    3
    The densely packed matter of a pulsar spins at incredible speeds, and emit radio waves that can be observed from Earth. Credit: Swinburne Astronomy Productions/CAASTRO.

    The accidental discovery

    In May, PhD student Andrew Zic planned to observe the red dwarf star Proxima Centauri – the closest star to the Sun. He wanted to better understand the flaring process and the implications for life on exoplanets around that star. But his four-day observation helped discovered something new.

    During the Proxima Centauri observation, Emil wanted to test a new feature on ASKAP. The feature gave ASKAP the ability to see in circular polarisation. This is where the wave component of light from a source rotates in a circular motion. This form of light is not common in astronomical sources but can be seen in flaring stars and some pulsars.

    “Our eyes can’t distinguish between circularly polarised light and unpolarised light. But ASKAP has the equivalent of polaroid sunglasses that can help highlight such sources against the glare of thousands of unpolarised sources,” Emil said.

    “It worked a treat. Proxima Centauri stood out like a sore thumb. But I noticed another weaker source at the edge of the image. I had one of those ‘hmm, that’s weird’ moments.”

    Emil let the Variable and Slow Transients (VAST) team that he collaborates with know of the potential discovery. They gathered clues from any previous observations to track down the culprit. Was it a flare star, a new pulsar, or perhaps something else?

    “My colleague Shi Dai used the Parkes Radio Telescope to confirm that our mystery source had periodic pulses and was indeed a newly discovered pulsar.”

    A rare sighting

    Not only was this the first pulsar discovered with ASKAP but also the first pulsar revealed by its circular polarisation. As it turns out, it’s also in the top 90 fastest spinning pulsars (out of about 2700 known pulsars). And it’s spinning at a rate of around 360 times a second!

    “When you’re looking at the sky for the first time through a new instrument, you’re bound to find something fascinating. In this case, there was nothing else in the field. It’s very rare you have something that sticks out so much.”

    “There are hints the pulsar we discovered is part of a binary system,” Emil explained.

    A binary system is simply one in which two objects orbit around a common centre of mass. That is, they are gravitationally bound to each other. Binary systems with pulsars are of immense importance to astronomers as they allow them to test our understanding of gravity.

    “Being part of this system would affect the timing of the pulsar ever so slightly depending on whether it is heading towards us or away from us during its orbit around a companion.”

    The team has been given extra time with the Parkes Radio Telescope to get a better estimate of the timing. And to see if they can find evidence of its companion.

    If you’d like to read more, these findings have been published in The Astrophysical Journal.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    SKA/ASKAP radio telescope at the Murchison Radio-astronomy Observatory (MRO) in Mid West region of Western Australia

    So what can we expect these new radio projects to discover? We have no idea, but history tells us that they are almost certain to deliver some major surprises.

    Making these new discoveries may not be so simple. Gone are the days when astronomers could just notice something odd as they browse their tables and graphs.

    Nowadays, astronomers are more likely to be distilling their answers from carefully-posed queries to databases containing petabytes of data. Human brains are just not up to the job of making unexpected discoveries in these circumstances, and instead we will need to develop “learning machines” to help us discover the unexpected.

    With the right tools and careful insight, who knows what we might find.

    CSIRO campus

    CSIRO, the Commonwealth Scientific and Industrial Research Organisation, is Australia’s national science agency and one of the largest and most diverse research agencies in the world.

     
  • richardmitnick 12:31 pm on October 10, 2019 Permalink | Reply
    Tags: , , , , , , , , Pulsars   

    From AAS NOVA: “Should We Blame Pulsars for Too Much Antimatter?” 

    AASNOVA

    From AAS NOVA

    9 October 2019
    Susanna Kohler

    1
    Artist’s illustration of Geminga, a nearby pulsar that has been proposed to be the source of excess positrons measured at Earth. [Nahks Tr’Ehnl]

    The Earth is constantly being bombarded by cosmic rays — high energy protons and atomic nuclei that speed through space at nearly the speed of light. Where do these energetic particles come from? A new study examines whether pulsars are the source of one particular cosmic-ray conundrum.

    Cosmic rays produced by high-energy astrophysics sources (ASPERA collaboration – AStroParticle ERAnet)

    An Excess of Positrons

    In 2008, our efforts to understand the origin of cosmic rays hit a snag: data from a detector called PAMELA showed that more high-energy positrons were reaching Earth in cosmic rays than theory predicted.

    INFN PAMELA spacecraft


    INFN PAMELA Schematic

    Positrons — the antimatter counterpart to electrons — are thought to be primarily produced by high-energy protons scattering off of particles within our galaxy. These interactions should produce decreasing numbers of positrons at higher energies — yet the data from PAMELA and other experiments show that positron numbers instead go up with increasing energy.

    Something must be producing these extra high-energy positrons — but what?

    Clues from Gamma-rays

    One of the leading theories is that the excess positrons are produced by nearby pulsars — rapidly rotating, magnetized neutron stars. We know that pulsars gradually spin slower and slower over time, losing power as they spew a stream of high-energy electrons and positrons into the surrounding interstellar medium. If the pulsar is close enough to us, positrons produced in and around pulsars might make it to Earth before losing energy to interactions as they travel.

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    3
    Observations from the High-Altitude Water Čerenkov (HAWC) Gamma-Ray Observatory show TeV nebulae around pulsars Geminga and PSR B0656+14. But do these sources also have extended GeV nebulae that would provide more direct constraints on positron density? [John Pretz]

    HAWC High Altitude Čerenkov Experiment, located on the flanks of the Sierra Negra volcano in the Mexican state of Puebla at an altitude of 4100 meters(13,500ft), at WikiMiniAtlas 18°59′41″N 97°18′30.6″W. searches for cosmic rays

    Could nearby pulsars produce enough positrons — and could they diffuse out from the pulsars efficiently enough — to account for the high-energy excess we observe here at Earth? A team of scientists now addresses these questions in a new publication led by Shao-Qiang Xi (Nanjing University and Chinese Academy of Sciences).

    To test whether pulsars are responsible for the positrons we see, Xi and collaborators argue that we should look for GeV emission around candidate sources. As the pulsar-produced positrons diffuse outward, they should scatter off of infrared and optical background photons in the surrounding region. This would create a nebula of high-energy emission around the pulsars that glows at 10–500 GeV — detectable by observatories like the Fermi Gamma-ray Space Telescope.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    6
    Fermi LAT gamma-ray count map (top) and residuals after the background is subtracted (bottom) for the region containing Geminga and PSR B0656+14. [Adapted from Xi et al. 2019]

    Two Pulsars Get an Alibi

    Xi and collaborators carefully analyze 10 years of Fermi LAT observations for two nearby pulsars that have been identified as likely candidates for the positron excess: Geminga and PSR B0656+14, located roughly 800 and 900 light-years away from us.

    The result? They find no evidence of extended GeV emission around these sources. The authors’ upper limits on emission from Geminga and PSR B0656+14 give these objects an alibi, suggesting that pulsars can likely account for only a small fraction of the positron excess we observe.

    So where does this leave us? If pulsars are cleared, we will need to look to other candidate sources of high-energy positrons: either other nearby cosmic accelerators like supernova remnants, or more exotic explanations, like the annihilation or decay of high-energy dark matter.

    Citation

    “GeV Observations of the Extended Pulsar Wind Nebulae Constrain the Pulsar Interpretations of the Cosmic-Ray Positron Excess,” Shao-Qiang Xi et al 2019 ApJ 878 104.
    https://iopscience.iop.org/article/10.3847/1538-4357/ab20c9

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

     
  • richardmitnick 9:50 am on September 22, 2019 Permalink | Reply
    Tags: , , , , , , , , Pulsars, The radio pulsar J0952-0607   

    From Max Planck Institute for Gravitational Physics: “Pulsating gamma rays from neutron star rotating 707 times a second” 

    From Max Planck Institute for Gravitational Physics

    September 19, 2019

    Media contact

    Dr. Benjamin Knispel
    Press Officer AEI Hannover
    Phone:+49 511 762-19104
    Fax:+49 511 762-17182
    benjamin.knispel@aei.mpg.de

    Science contacts
    Lars Nieder
    Phone:+49 511 762-17491
    Fax:+49 511 762-2784
    lars.nieder@aei.mpg.de

    Prof. Dr. Bruce Allen
    Director
    Phone:+49 511 762-17148
    Fax:+49 511 762-17182
    bruce.allen@aei.mpg.de

    1
    A black widow pulsar and its small stellar companion, viewed within their orbital plane. Powerful radiation and the pulsar’s “wind” – an outflow of high-energy particles — strongly heat the facing side of the star to temperatures twice as hot as the sun’s surface. The pulsar is gradually evaporating its partner, which fills the system with ionized gas and prevents astronomers from detecting the pulsar’s radio beam most of the time. NASA’s Goddard Space Flight Center/Cruz deWilde

    Second fastest spinning radio pulsar known is a gamma-ray pulsar, too. Multi-messenger observations look closely at the system and raise new questions.

    An international research team led by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover has discovered that the radio pulsar J0952-0607 also emits pulsed gamma radiation. J0952-0607 spins 707 times in one second and is 2nd in the list of rapidly rotating neutron stars. By analyzing about 8.5 years worth of data from NASA’s Fermi Gamma-ray Space Telescope, LOFAR radio observations from the past two years, observations from two large optical telescopes, and gravitational-wave data from the LIGO detectors, the team used a multi-messenger approach to study the binary system of the pulsar and its lightweight companion in detail.

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain, sited on a volcanic peak 2,267 metres (7,438 ft) above sea level

    TFC HiPERCAM mounted on the Gran Telescopio Canarias,

    ESO/NTT at Cerro La Silla, Chile, at an altitude of 2400 metres

    ESO La Silla NTT ULTRACAM is an ultra fast camera capable of capturing some of the most rapid astronomical events. It can take up to 500 pictures a second in three different colours simultaneously. It was designed and built by scientists from the Universities of Sheffield and Warwick (United Kingdom), in collaboration with the UK Astronomy Technology Centre in Edinburgh. ULTRACAM employs the latest in charged coupled device (CCD) detector technology in order to take, store and analyse data at the required sensitivities and speeds. CCD detectors can be found in digital cameras and camcorders, but the devices used in ULTRACAM are special because they are larger, faster and most importantly, much more sensitive to light than the detectors used in today’s consumer electronics products. Since it was built, it has operated at the William Herschel Telescope, the New Technology Telescope, and the Very Large Telescope. It is now permanently mounted on the Thai National Telescope.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    ASTRON LOFAR European Map


    ASTRON LOFAR Radio Antenna Bank, Netherlands

    Their study published in The Astrophysical Journal shows that extreme pulsar systems are hiding in the Fermi catalogues and published in the Astrophysical Journal today shows that extreme pulsar systems are hiding in the Fermi catalogues and motivates further searches. Despite being very extensive, the analysis also raises new unanswered questions about this system.

    MIT /Caltech Advanced aLigo

    Pulsars are the compact remnants of stellar explosions which have strong magnetic fields and are rapidly rotating.

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Dame Susan Jocelyn Bell Burnell at work on first plusar chart 1967 pictured working at the Four Acre Array in 1967. Image courtesy of Mullard Radio Astronomy Observatory.

    Dame Susan Jocelyn Bell Burnell 2009

    Dame Susan Jocelyn Bell Burnell (1943 – ), still working from http://www. famousirishscientists.weebly.com

    They emit radiation like a cosmic lighthouse and can be observable as radio pulsars and/or gamma-ray pulsars depending on their orientation towards Earth.

    The fastest pulsar outside globular clusters

    PSR J0952-0607 (the name denotes the position in the sky) was first discovered in 2017 by radio observations of a source identified by the Fermi Gamma-ray Space Telescope as possibly being a pulsar. No pulsations of the gamma rays in data from the Large Area Telescope (LAT) onboard Fermi had been detected. Observations with the radio telescope array LOFAR identified a pulsating radio source and – together with optical telescope observations – allowed to measure some properties of the pulsar. It is orbiting the common center of mass in 6.2 hours with a companion star that only weighs a fiftieth of our Sun. The pulsar rotates 707 times in a single second and is therefore the fastest spinning in our Galaxy outside the dense stellar environments of globular clusters.

    Searching for extremely faint signals

    Using this prior information on the binary pulsar system, Lars Nieder, a PhD student at the AEI Hannover, set out to see if the pulsar also emitted pulsed gamma rays. “This search is extremely challenging because the Fermi gamma-ray telescope only registered the equivalent of about 200 gamma rays from the faint pulsar over the 8.5 years of observations. During this time the pulsar itself rotated 220 billion times. In other words, only once in every billion rotations was a gamma ray observed!” explains Nieder. “For each of these gamma rays, the search must identify exactly when during each of the 1.4 millisecond rotations it was emitted.”

    This requires combing through the data with very fine resolution in order not to miss any possible signals. The computing power required is enormous. The very sensitive search for faint gamma-ray pulsations would have taken 24 years to complete on a single computer core. By using the Atlas computer cluster at the AEI Hannover it finished in just 2 days.

    MPG Institute for Gravitational Physics Atlas Computing Cluster

    A strange first detection

    “Our search found a signal, but something was wrong! The signal was very faint and not quite where it was supposed to be. The reason: our detection of gamma rays from J0952-0607 had revealed a position error in the initial optical-telescope observations which we used to target our analysis. Our discovery of the gamma-ray pulsations revealed this error,” explains Nieder. “This mistake was corrected in the publication reporting the radio pulsar discovery. A new and extended gamma-ray search made a rather faint – but statistically significant – gamma-ray pulsar discovery at the corrected position.”

    Having discovered and confirmed the existence of pulsed gamma radiation from the pulsar, the team went back to the Fermi data and used the full 8.5 years from August 2008 until January 2017 to determine physical parameters of the pulsar and its binary system. Since the gamma radiation from J0952-0607 was so faint, they had to enhance their analysis method developed previously to correctly include all unknowns.

    3
    The pulse profile (distribution of gamma-ray photons during one rotation of the pulsar) of J0952-0607 is shown at the top. Below is the corresponding distribution of the individual photons over the ten years of observations. The greyscale shows the probability (photon weights) for individual photons to originate from the pulsar. From mid 2011 on, the photons line up along tracks corresponding to the pulse profile. This shows the detection of gamma-ray pulsations, which is not possible before mid 2011. L. Nieder/Max Planck Institute for Gravitational Physics.

    Another surprise: no gamma-ray pulsations before July 2011

    The derived solution contained another surprise, because it was impossible to detect gamma-ray pulsations from the pulsar in the data from before July 2011. The reason for why the pulsar only seems to show pulsations after that date is unknown. Variations in how much gamma rays it emitted might be one reason, but the pulsar is so faint that it was not possible to test this hypothesis with sufficient accuracy. Changes in the pulsar orbit seen in similar systems might also offer an explanation, but there was not even a hint in the data that this was happening.

    Optical observations raise further questions

    The team also used observations with the ESO’s New Technology Telescope at La Silla and the Gran Telescopio Canarias on La Palma to examine the pulsar’s companion star. It is most likely tidally locked to the pulsar like the Moon to the Earth so that one side always faces the pulsar and gets heated up by its radiation. While the companion orbits the binary system’s center of mass its hot “day” side and cooler “night” side are visible from the Earth and the observed brightness and color vary.

    These observations create another riddle. While the radio observations point to a distance of roughly 4,400 light-years to the pulsar, the optical observations imply a distance about three times larger. If the system was relatively close to Earth, it would feature a never-seen-before extremely compact high density companion, while larger distances are compatible with the densities of known similar pulsar companions. An explanation for this discrepancy might be the existence of shock waves in the wind of particles from the pulsar, which could lead to a different heating of the companion. More gamma-ray observations with Fermi LAT observations should help answer this question.

    Searching for continuous gravitational waves

    Another group of researchers at the AEI Hannover searched for continuous gravitational wave emission from the pulsar using LIGO data from the first (O1) and second (O2) observation run. Pulsars can emit gravitational waves when they have tiny hills or bumps. The search did not detect any gravitational waves, meaning that the pulsar’s shape must be very close to a perfect sphere with the highest bumps less than a fraction of a millimeter.

    Rapidly rotating neutron stars

    Understanding rapidly spinning pulsars is important because they are probes of extreme physics. How fast neutron stars can spin before they break apart from centrifugal forces is unknown and depends on unknown nuclear physics. Millisecond pulsars like J0952-0607 are rotating so rapidly because they have been spun up by accreting matter from their companion. This process is thought to bury the pulsar’s magnetic field. With the long-term gamma-ray observations, the research team showed that J0952-0607 has one of the ten lowest magnetic fields ever measured for a pulsar, consistent with expectations from theory.

    Einstein@Home searches for test cases of extreme physics

    “We will keep studying this system with gamma-ray, radio, and optical observatories since there are still unanswered questions about it. This discovery also shows once more that extreme pulsar systems are hiding in the Fermi LAT catalogue,” says Prof. Bruce Allen, Nieder’s PhD supervisor and Director at the AEI Hannover. “We are also employing our citizen science distributed computing project Einstein@Home to look for binary gamma-ray pulsar systems in other Fermi LAT sources and are confident to make more exciting discoveries in the future.”

    Einstein@home, a BOINC project

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Max Planck Institute for Gravitational Physics (Albert Einstein Institute) is the largest research institute in the world specializing in general relativity and beyond. The institute is located in Potsdam-Golm and in Hannover where it is closely related to the Leibniz Universität Hannover.

     
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