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  • richardmitnick 10:50 am on June 1, 2021 Permalink | Reply
    Tags: , , , , , Pulsars, Women in STEM- Victoria M Kaspi and Chryssa Kouveliotou Receive the 2021 Shaw Prize in Astronomy   

    From International Astronomical Union (FR) : “Women in STEM- Victoria M Kaspi and Chryssa Kouveliotou Receive the 2021 Shaw Prize in Astronomy” 

    From International Astronomical Union (FR)

    1 June 2021

    1
    Victoria M Kaspi and Chryssa Kouveliotou Receive the 2021 Shaw Prize in Astronomy.

    The Shaw Prize in Astronomy 2021 is shared equally by Victoria M. Kaspi, Professor of Physics and Director of McGill Space Institute, McGill University (CA), Canada and Chryssa Kouveliotou, Professor and Chair, Department of Physics at George Washington University (US) for their contributions to our understanding of magnetars, a class of highly magnetised neutron stars that are linked to a wide range of spectacular, transient astrophysical phenomena.


    This prestigious award is one way in which the Shaw Prize Foundation seeks to promote astronomy, a mission shared by the IAU and one which the two organisations have ongoing collaborations to pursue.

    Through the development of new and precise observational techniques, Victoria M. Kaspi and Chryssa Kouvelioto confirmed the existence of neutron stars with ultra-strong magnetic fields and characterised their physical properties. Their work has established magnetars as a new and important class of astrophysical objects.

    Neutron stars are the ultra-compact remnants of stellar explosions.

    Most are rapidly rotating with periods of milli-seconds to seconds and emit powerful beams of electromagnetic radiation (observed as pulsars).

    As such they are accurate ‘cosmic clocks’ that enable tests of fundamental physics in the presence of a gravitational field many billion times stronger than Earth’s. Reflecting their importance, the Nobel Prize in Physics has been awarded twice for work on pulsars (in 1974 and 1993).

    Pulsars also have strong magnetic fields, since the magnetic field lines in the progenitor star are ‘frozen in’ in the stellar remnant as it collapses to become a neutron star. These magnetic fields funnel jets of particles along the magnetic poles, but classical radio pulsars are powered mainly by rotational energy and slowly spin down over their lifetimes.

    The research carried out by Kaspi and Kouveliotou was motivated by the theoretical prediction that neutron stars with extreme magnetic fields up to a thousand times stronger than those in regular pulsars could form if dynamo action were efficient during the first few seconds after gravitational collapse in the core of the supernova. Such objects (termed magnetars) would be powered by their large reservoirs of magnetic energy, rather than by rotation, and were predicted to produce highly-energetic bursts of gamma-rays through the generation of highly energetic ionised particle pairs at their centres.

    From observations of a class of X-ray/gamma-ray sources called “soft gamma-ray repeaters” (SGRs) Chryssa Kouveliotou and her colleagues in 1998–99 established the existence of magnetars and provided a stunning confirmation of the magnetar model. By developing new techniques for pulse timing at X-ray wavelengths and applying these to data from the Rossi X-ray timing satellite (RXTE), Kouveliotou in 1998 was able to detect X-ray pulses with a period of 7.5 seconds within the persistent X-ray emission of SGR 1806-20.

    She then measured a spin-down rate for the pulsar, and derived both the pulsar age and the dipolar magnetic field strength — which lay within the range of values predicted for magnetars, close to 1014 gauss (1010 T). The spin-down measurements were extremely challenging because of the faintness of the pulsed signal and the need to correct the rotation phase across multiple epochs.

    Victoria Kaspi showed that a second class of rare X-ray emitting pulsars, the anomalous X-ray pulsars (AXPs), were also magnetars. Kaspi took the techniques used by radio astronomers to maintain phase coherence in pulsar timing and adapted them to work in the much more challenging X-ray domain. This allowed her to make extremely accurate timing measurements of X-ray pulsars with full phase coherence across intervals of months to years, and hence to measure spin-down rates far smaller than those seen in SGR 1806-20. Kaspi has also made fundamental contributions to the characterisation of magnetars as a population, through the elucidation of their physical properties and their relationship to the classical radio pulsars. Her work has cemented the recognition of magnetars as a distinct source class. Today, magnetars are routinely invoked to explain the physics underlying a diverse range of astrophysical transients including gamma-ray bursts, superluminous supernovae and nascent neutron stars.

    Magnetars probe extreme physical conditions inaccessible on Earth, such as strong gravity, ultra-nuclear densities and the strongest magnetic fields in the Universe. In this high energy environment particle-antiparticle pairs are created from the vacuum, and unique tests of general relativity and quantum electrodynamics become possible. In 2020–2021, the first associations of a Galactic magnetar with millisecond duration outbursts of radio emission, so called Fast Radio Bursts (FRBs), were established. These results may suggest that “flaring” magnetars are the central engines of at least some of the spectacular extragalactic FRBs. Future studies will undoubtedly shed further light on these exciting discoveries.

    The Shaw Prize 2021 recognises the seminal contributions of Victoria M. Kaspi and Chryssa Kouveliotou to the understanding of the enigmatic properties of magnetars, pulsars and gamma-ray bursts.

    See the full article here .

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    Please help promote STEM in your local schools.

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    The International Astronomical Union [astronomique internationale] (FR) exists to promote and safeguard the science of astronomy through international cooperation, assign official names and designations to celestial bodies, and liaise with organizations that include amateur astronomers. Founded in 1919 and based in Paris, the IAU is a member of the International Science Council.

    The International Astronomical Union is an international association of professional astronomers, at the PhD level and beyond, active in professional research and education in astronomy. Among other activities, it acts as the recognized authority for assigning designations and names to celestial bodies (stars, planets, asteroids, etc.) and any surface features on them.

    The IAU is a member of the International Science Council (ISC). Its main objective is to promote and safeguard the science of astronomy in all its aspects through international cooperation. The IAU maintains friendly relations with organizations that include amateur astronomers in their membership. The IAU has its head office on the second floor of the Institute of Astrophysics of Paris [Institut Astrophysique de Paris] (FR) in the 14th arrondissement of Paris.

    This organisation has many working groups. For example, the Working Group for Planetary System Nomenclature (WGPSN), which maintains the astronomical naming conventions and planetary nomenclature for planetary bodies, and the Working Group on Star Names (WGSN), which catalogues and standardizes proper names for stars. The IAU is also responsible for the system of astronomical telegrams which are produced and distributed on its behalf by the Central Bureau for Astronomical Telegrams at Harvard (US). The Minor Planet Center also operates under the IAU, and is a “clearinghouse” for all non-planetary or non-moon bodies in the Solar System.

     
  • richardmitnick 5:34 pm on February 23, 2021 Permalink | Reply
    Tags: "Reclusive Neutron Star May Have Been Found in Famous Supernova", , , , , For decades scientists have searched for a neutron star in SN 1987A-i.e. a dense collapsed core that should have been left behind by the explosion., If this result is upheld by future observations it would confirm the existence of a neutron star in SN 1987A., , , Pulsars, , This latest study shows that a "pulsar wind nebula" created by such a neutron star may be present.   

    From NASA Chandra and From NASA NuSTAR: “Reclusive Neutron Star May Have Been Found in Famous Supernova” 

    NASA Chandra Banner

    NASA Chandra X-ray Space Telescope

    From NASA Chandra

    February 23, 2021

    Media contacts:
    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    Molly Porter
    Marshall Space Flight Center, Huntsville, Alabama
    256-544-0034
    molly.a.porter@nasa.gov

    Astronomers now have evidence from two X-ray telescopes (Chandra and NuSTAR) for a key component of a famous supernova remnant.

    NASA/DTU/ASI NuSTAR X-ray telescope.

    Supernova 1987A was discovered on Earth on February 24, 1987, making it the first such event witnessed during the telescopic age.

    SN 1987A remnant, imaged by ALMA. The inner region is contrasted with the outer shell, lacy white and blue circles, where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation. Image credit: ALMA / ESO / NAOJ / NRAO / Alexandra Angelich, NRAO / AUI / NSF.

    SN1987A. Credit: NASA/ESA Hubble Space Telescope in January, 2017 using its Wide Field Camera 3 (WFC3).

    NASA/ESA Hubble WFC3

    NASA/ESA Hubble Telescope.

    For decades, scientists have searched for a neutron star in SN 1987A, i.e. a dense collapsed core that should have been left behind by the explosion.

    This latest study shows that a “pulsar wind nebula” created by such a neutron star may be present.
    ________________________________________________________________________________________________________

    Astronomers have found evidence for the existence of a neutron star at the center of Supernova 1987A (SN 1987A), which scientists have been seeking for over three decades. As reported in our latest press release, SN 1987A was discovered on February 24, 1987. The panel on the left contains a 3D computer simulation, based on Chandra data, of the supernova debris from SN 1987A crashing into a surrounding ring of material. The artist’s illustration (right panel) depicts a so-called pulsar wind nebula, a web of particles and energy blown away from a pulsar, which is a rotating, highly magnetized neutron star. Data collected from NASA’s Chandra X-ray Observatory and NuSTAR in a new study support the presence of a pulsar wind nebula at the center of the ring.

    If this result is upheld by future observations, it would confirm the existence of a neutron star in SN 1987A, the collapsed core that astronomers expect would be present after the star exploded. The pulsar would also be the youngest one ever found.

    3
    NuSTAR and Chandra images of Supernova 1987A. Credit: NASA.

    When a star explodes, it collapses onto itself before the outer layers are blasted into space. The compression of the core turns it into an extraordinarily dense object, with the mass of the Sun squeezed into an object only about 10 miles across. Neutron stars, as they were dubbed because they are made nearly exclusively of densely packed neutrons, are laboratories of extreme physics that cannot be duplicated here on Earth. Some neutron stars have strong magnetic fields and rotate rapidly, producing a beam of light akin to a lighthouse. Astronomers call these objects “pulsars,” and they sometimes blow winds of charged particles that can create pulsar wind nebulas.

    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.

    With Chandra and NuSTAR, the team found relatively low-energy X-rays from the supernova debris crashing into surrounding material. The team also found evidence of high-energy particles, using NuSTAR’s ability to detect higher-energy X-rays.

    There are two likely explanations for this energetic X-ray emission: either a pulsar wind nebula, or particles being accelerated to high energies by blast wave of the explosion. The latter effect doesn’t require the presence of a pulsar and occurs over much larger distances from the center of the explosion.

    The latest X-ray study supports the case for the pulsar wind nebula on a couple of fronts. First, the brightness of the higher energy X-rays remained about the same between 2012 and 2014, while the radio emission increased. This goes against expectations in the scenario of energetic particles in the explosion debris. Next, authors estimate it would take almost 400 years to accelerate the electrons up to the highest energies seen in the NuSTAR data, which is over ten times older than the age of the remnant.

    The Chandra and NuSTAR data also support a 2020 result from the Atacama Large Millimeter Array (ALMA) that provided possible evidence for the structure of a pulsar wind nebula in the radio band.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

    While this “blob” had other potential explanations, its identification as a pulsar wind nebula could be substantiated with the new X-ray data.

    The center of SN 1987A is surrounded by gas and dust. The authors used state-of-the-art simulations to understand how this material would absorb X-rays at different energies, enabling more accurate interpretation of the X-ray spectrum, that is, the spread of X-rays over wavelength. This enables them to estimate what the spectrum of the central regions of SN 1987A is without the obscuring material.

    A paper describing these results is being published this week in The Astrophysical Journal Letters. The authors of the paper are Emanuele Greco and Marco Miceli (University of Palermo[Università degli Studi di Palermo](IT)), Salvatore Orlando, Barbara Olmi and Fabrizio Bocchino (Palermo Astronomical Observatory[Giuseppe S. Vaiana Astronomical Observatory](IT), an Italian National Institute for Astrophysics [Istituto Nazionale di Astrofisica](IT) research facility); Shigehiro Nagataki and Masaomi Ono (Astrophysical Big Bang Laboratory, RIKEN Institute of Physical and Chemical Research [Kokuritsu Kenkyū Kaihatsu Hōjin Rikagaku Kenkyūsho (国立研究開発法人理化学研究所](JP) ); Akira Dohi (Kyushu University[九州大学, Kyūshū Daigaku](JP), and Giovanni Peres (University of Palermo).

    NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for the agency’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at UC Berkeley(US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech.


    Quick Look: Supernova 1987A Pulsar Wind Nebula

    See the full article here.


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NuSTAR is a Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory for the agency’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Technical University of Denmark[Danmarks Tekniske Universitet](DK) and the ASI Italian Space Agency [Agenzia Spaziale Italiana](IT). The spacecraft was built by Orbital Sciences Corporation in Dulles, Virginia(US) (now part of Northrop Grumman). NuSTAR’s mission operations center is at UC Berkeley(US), and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center(US). ASI provides the mission’s ground station and a mirror archive. JPL is a division of Caltech.


    NuSTAR’s mission operations center is at UC Berkeley, with the ASI providing its equatorial ground station located at Malindi, Kenya. The mission’s outreach program is based at Sonoma State University, Rohnert Park, Calif. NASA’s Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA.

    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 10:16 pm on February 2, 2021 Permalink | Reply
    Tags: "Einstein@Home reveals true identity of mysterious gamma-ray source", , , , , , , Pulsars, The rapidly rotating neutron star- a pulsar- PSR J2039−5617   

    From MPG Institute for Gravitational Physics [MPG Institut für Gravitationsphysik] (Albert Einstein Institut) (DE): “Einstein@Home reveals true identity of mysterious gamma-ray source” 

    From MPG Institute for Gravitational Physics [MPG Institut für Gravitationsphysik] (Albert Einstein Institut) (DE)

    February 02, 2021

    Media Contact

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

    Science Contacts
    Dr. Lars Nieder
    Junior Scientist/Postdoc
    +49 511 762-17491
    lars.nieder@aei.mpg.de

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

    Distributed volunteer computing project finds neutron star rotating 377 times a second in an exotic binary system using data from NASA’s Fermi Space Telescope.


    Einstein@home is a project running on BOINC software from The Space Science Laboratory at UC Berkeley.

    My BOINC


    As you can see above, I participated in this project when I was BOINC “cruncher”.

    An international research team including members from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover has shown that a rapidly rotating neutron star is at the core of a celestial object now known as PSR J2039−5617. They used novel data analysis methods and the enormous computing power of the citizen science project Einstein@home to track down the neutron star’s faint gamma-ray pulsations in data from NASA’s Fermi Space Telescope.

    NASA/Fermi LAT.


    NASA/Fermi Gamma Ray Space Telescope.

    Their results show that the pulsar is in orbit with a stellar companion about a sixth of the mass of our Sun. The pulsar is slowly but surely evaporating this star. The team also found that the companion’s orbit varies slightly and unpredictably over time. Using their search method, they expect to find more such systems with einstein@home in the future.

    1
    Artist’s impression of PSR J2039−5617 and its companion. The binary system consists of a rapidly rotating neutron star (right) and a stellar companion about a sixth of the mass of our Sun (left). The star is deformed by the neutron star’s strong tidal forces and it is heated by the neutron stars gamma radiation (magenta). The modelled surface temperature of the star is shown in brown (cooler) to yellow (hotter) color. The radiation from the neutron star slowly but surely evaporates the star and creates clouds of plasma in the binary system, which hamper observation at radio wavelengths. Credit: Knispel/Clark/Max Planck Institute for Gravitational Physics/NASA GSFC.

    “It had been suspected for years that there is a pulsar, a rapidly rotating neutron star, at the heart of the source we now know as PSR J2039−5617,” says Lars Nieder, a PhD student at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover and co-author of the study published today in MNRAS. “But it was only possible to lift the veil and discover the gamma-ray pulsations with the computing power donated by tens of thousands of volunteers to Einstein@Home,” he adds.

    The celestial object has been known since 2014 as a source of X-rays, gamma rays, and light. All evidence obtained so far pointed at a rapidly rotating neutron star in orbit with a light-weight star being at the heart of the source. But clear proof was missing.

    Precision observations with optical telescopes

    The first step to solving this riddle were new observations of the stellar companion with optical telescopes.

    Optical telescopes used in this work are the 3.5-m New Technology Telescope (NTT) at ESO La Silla; the 2.2-metre MPG/ESO telescope at ESO’s La Silla Observatory;the 4.2 m SOAR telescope; the Victor M. Blanco 4-meter Telescope at the NOIRLab NOAO CTIO Cerro Tololo Inter-American Observatory; the ESO Visible and Infrared Survey Telescope for Astronomy (VISTA).


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


    MPG/ESO 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.


    NOIRLab NOAO Southern Astrophysical Research [SOAR ] telescope situated on Cerro Pachón, just to the southeast of Cerro Tololo on the NOIRLab NOAO AURA site at an altitude of 2,700 meters (8,775 feet) above sea level.


    NOIRLab NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet.

    Also involved were NASA’s Swift spacecraft and ESA’s XMM-Newton X-ray space telescope.

    NASA Neil Gehrels Swift Observatory.

    ESA/XMM Newton X-ray telescope (EU).

    They provided precise knowledge about the binary system without which a gamma-ray pulsar search (even with Einstein@Home’s huge computing power) would be unfeasible.

    The system’s brightness varies during an orbital period depending on which side of the neutron star’s companion is facing the Earth. “For J2039-5617, there are two main processes at work,” explains Dr. Colin Clark from Jodrell Bank Centre for Astrophysics, lead author of the study and former PhD student at AEI Hannover. “The pulsar heats up one side of the light-weight companion, which appears brighter and more bluish. Additionally, the companion is distorted by the pulsar’s gravitational pull causing the apparent size of the star to vary over the orbit.” These observations allowed the team to get the most precise measurement possible of the binary star’s 5.5-hour orbital period, as well as other properties of the system.

    Searching with the help of tens of thousands of volunteers

    With this information and the precise sky position from Gaia data, the team used the aggregated computing power of the distributed volunteer computing project Einstein@Home for a new search of about 11 years of archival observations of NASA’s Fermi Gamma-ray Space Telescope.

    ESA (EU)/GAIA satellite .

    Improving on earlier methods they had developed for this purpose, they enlisted the help of tens of thousands of volunteers to search Fermi data for periodic pulsations in the gamma-ray photons registered by the Large Area Telescope onboard the space telescope. The volunteers donated idle compute cycles on their computers’ CPUs and GPUs to Einstein@Home.

    This search required combing very finely through the data in order not to miss any possible signals. The computing power required is enormous. The search would have taken 500 years to complete on a single computer core. By using a part of the Einstein@Home resources it was done in 2 months.

    With the computing power donated by the Einstein@Home volunteers, the team discovered gamma-ray pulsations from the rapidly rotating neutron star. This gamma-ray pulsar, now known as J2039−5617, rotates about 377 times each second.

    Surprising changes of the orbit

    “We found that the companion’s orbital period varies slightly and unpredictably over the 11 years. It only changes by up to about ten milliseconds, but since we know the arrival time of every single gamma photon from the pulsar to microsecond precision, even this little is a lot!” says Nieder. These variations of the orbital period could be linked to tiny changes in the shape of the companion caused by its magnetic activity. Similar to our Sun the companion might be going through activity cycles. The changing magnetic field interacts with the plasma inside the star and deforms it. As the shape of the star varies its gravitational field also changes, which in turn affects the pulsar orbit. This could explain the observed orbital period variations.

    “Spidery” pulsars consume their mates

    While the light-weight stellar companion is orbiting the pulsar, the strong radiation and particle wind from the pulsar evaporate the companion. “This is the reason that astronomers call systems like this one ‘redbacks’ in reference to the Australian redback spiders whose females consume the males after mating,” explains Nieder. In the case of J2039−5617 the matter ablated from the star forms clouds of charged particles in the binary system that absorb radio waves. This is one of the reasons that previous searches for pulsating radio emission from the neutron star failed. With the precise determination of the orbit from the gamma-ray data, it was also possible to detect radio pulsations and this will be published in a separate paper.

    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.

    “We know dozens of similar gamma-ray sources found by the Fermi Space Telescope, for which the true identity is still unclear,” says Prof. Dr. Bruce Allen, director at the Max Planck Institute for Gravitational Physics in Hannover and director and founder of Einstein@Home. “Many might be pulsars hidden in binary systems and we will continue to chase after them with Einstein@Home,” he adds.

    Background information

    Who made the discovery? The discovery was enabled by tens of thousands of Einstein@Home volunteers who have donated their CPU and GPU time to the project. Without them this study could not have been performed and this discovery could not have been made. The team is especially grateful to those volunteers whose computers discovered the pulsar (where the volunteer’s name is unknown, we give the Einstein@Home username in quotation marks): “Peter”.

    Neutron stars are compact remnants from supernova explosions and consist of exotic, extremely dense matter. They measure about 20 kilometers across and weigh more than our Sun. Because of their strong magnetic fields and fast rotation they emit beamed radio waves and energetic gamma rays similar to a cosmic lighthouse. If these beams point towards Earth during the neutron star’s rotation, it becomes visible as a pulsating radio or gamma-ray source – a so-called pulsar.

    Einstein@Home is a distributed volunteer computing and connects computers and smartphones from the general public from all over the world. The project volunteers donate spare computing time on their devices. Until now more than 480,000 volunteers have contributed useful computing work, making Einstein@Home one of the largest projects of this kind. The current aggregate computing power contributed by about 36,000 computers from 22,000 active volunteers is about 7.2 petaFLOPS.

    Since 2005, Einstein@Home has analyzed data from the gravitational wave detectors within the LIGO Scientific and the Virgo Collaborations for gravitational waves from unknown, rapidly rotating neutron stars.

    As of March 2009, Einstein@Home has also been involved in the search for signals from radio pulsars in observational data from the Arecibo Observatory in Puerto Rico and the Parkes Observatory in Australia.

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

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

    Since the first discovery of a radio pulsar by Einstein@Home in August 2010, the global computer network has discovered 55 new radio pulsars. A search for gamma-ray pulsars in data of the Fermi satellite was added in August 2011. It has discovered 25 new gamma-ray pulsars as of today.

    Scientific supporters are the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, Hannover) and the Center for Gravitation and Cosmology at the University of Wisconsin-Milwaukee with financial support from the National Science Foundation and the Max Planck Society.

    See the full article here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    MPG Institute for Gravitational Physics [MPG Institut für Gravitationsphysik] (Albert Einstein Institut) (DE) 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.

     
  • richardmitnick 9:17 am on August 25, 2020 Permalink | Reply
    Tags: "Will Radio Bursts Reveal Hidden Baryons?", , , , , , , , , , Pulsars   

    From AAS NOVA: “Will Radio Bursts Reveal Hidden Baryons?” 

    AASNOVA

    From AAS NOVA

    24 August 2020
    Susanna Kohler

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.


    Transients like fast radio bursts, detected with telescopes like the ASKAP array may be the key to identifying how much matter is hiding in our galaxy’s diffuse halo.

    The Earth, your body, and the electronic device you’re reading this on are all made up of ordinary, baryonic matter. A new study has now used bursts of radio emission to probe whether the outskirts of our galaxy are hiding vast quantities of “missing” baryonic matter.

    Missing Matter

    2
    The relative amounts of the different constituents of the universe. Ordinary baryonic matter makes up less than 5%. [ESA/Planck.]

    We’ve long known that only about 5% of the content of the universe is ordinary baryonic matter; the remainder is dark matter and dark energy. But when scientists have searched for this baryonic matter in the nearby universe, they found a puzzle: galaxies’ gas, dust, and stars only accounted for a small fraction of their expected baryonic matter.

    Our own Milky Way is no exception — it also has a baryon fraction much lower than the overall baryon fraction in the universe. So where are its missing baryons? Were they expelled from our galaxy at some point in the past? Or did the Milky Way retain its baryons — but we haven’t detected them yet?

    An Elusive Halo

    If our galaxy’s baryons are still around, a likely hiding place is in the Milky Way’s outskirts, in the circumgalactic medium (CGM).

    3
    The Sombrero galaxy, M104, provides an example of a galaxy and its halo — the diffuse gas that extends above and below the galaxy’s disk. [ESA/C. Carreau.]

    When our galaxy formed, gas was dragged inward with the collapsing dark-matter halo, shock heating and forming a surrounding bubble of hot, diffuse plasma — the CGM. This surrounding galactic halo may well contain our galaxy’s missing baryons today, but it’s very difficult to probe; since the gas is diffuse, we can’t measure it directly from within the Milky Way.

    A new study led by Emma Platts (University of Cape Town, South Africa) has instead measured the galactic halo’s matter by observing how distant signals interact with the CGM as they travel to us.

    Clues from Transients

    Platts and collaborators use two types of radio transients to measure CGM distribution: pulsars, which are pulsating neutron stars that reside in our galaxy’s disk, and fast radio bursts, which are brief flashes of radio emission that originate far beyond our galaxy.

    4
    Pulsars, which typically lie in the galactic disk, emit radiation that sweeps over the Earth like a lighthouse, appearing as pulses. These pulses become dispersed as they travel through the galaxy to reach us. [Bill Saxton/NRAO/AUI/NSF]

    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.

    Light from these sources travels across space to us, interacting with matter distributed along the way. The interactions slow down longer wavelengths of light more than shorter, causing the signal to spread out. The dispersion measure — the quantification of this spread — therefore tells us how much matter the signal traveled through to get to us.

    Probing Our Surroundings

    By statistically analyzing the distribution of pulsar and fast radio burst dispersion measures, Platts and collaborators placed bounds on the Milky Way halo’s dispersion measure: its minimum is set by the farthest pulsars, which lie interior to the halo, and its maximum is set by the closest fast radio bursts, which lie far beyond our halo in neighboring galaxies.

    Milky Way Halo NASA/ESA STScI

    So are the Milky Way’s missing baryons hiding in the CGM? We can’t say for certain yet, but the results suggest no, if the baryons are distributed in the same way as the dark matter. The future should hold more certainty though! Our sample of fast radio bursts is rapidly growing, and the authors estimate that once we’ve cataloged several thousand, we’ll be able to bound the content of the Milky Way’s halo more definitively.

    5
    Schematic illustrating how transient radio signals travel to us. Pulsars (marked by sun symbols) lie in the galaxy, interior to the halo; their signals are dispersed only by the Milky Way’s interstellar matter. Fast radio bursts (marked by lightning symbol) lie in other galaxies; their signals are dispersed by the Milky Way’s interstellar matter, its halo, the intergalactic medium, the host galaxy’s halo, and the host itself. These two types of transients can therefore place upper and lower bounds on the matter in the Milky Way’s halo. [Platts et al. 2020]

    Citation

    “A Data-driven Technique Using Millisecond Transients to Measure the Milky Way Halo,” E. Platts et al 2020 ApJL 895 L49.

    https://iopscience.iop.org/article/10.3847/2041-8213/ab930a

    See the full article here .


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    Please help promote STEM in your local schools.

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    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 1:16 pm on August 23, 2020 Permalink | Reply
    Tags: "The First Gamma-Ray Pulsar Confirmed by the People", (MSPs)-millisecond pulsars, 3FGL J2039.6−5618 is indeed a redback MSP now confirmed as PSR J2039-5617., A lesson in gamma-ray pulsar searching, , , , , , Pulsars, Pulsars are rapidly rotating neutron stars that emit radio waves like a light house as they rotate., The gamma-ray source 3FGL J2039.6−5618   

    From astrobites: “The First Gamma-Ray Pulsar Confirmed by the People” 

    Astrobites bloc

    From astrobites

    Title: Einstein@Home Discovery of Gamma-ray Pulsations Confirms the Redback Nature of 3FGL J2039.6-5618

    Authors: C. J. Clark, L. Nieder, G. Voisin, B. Allen, C. Aulbert, O. Behnke, R. P. Breton, C. Choquet, A. Corongiu, V. S. Dhillon, H. B. Eggenstein, H. Fehrmann, L. Guillemot, A. K. Harding, M. R. Kennedy, B. Machenschalk, T. R. Marsh, D. Mata Sánchez, R. P. Mignani, J. Stringer, Z. Wadiasingh, J. Wu

    First Author’s Institution: Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, M13 9PL, UK

    Status: Submitted to MNRAS, open access on arXiv.

    Pulsars are rapidly rotating neutron stars that emit radio waves like a light house as they rotate.

    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.

    They come in many flavors, like millisecond pulsars (MSPs), pulsars that complete a rotation in less than 30 milliseconds, many of which belong to a family of “spider” pulsars. These spider pulsars are so named because they blow away or accrete the mass of their binary companion, similar to how some spiders kill their male partners. The two (or three) types of spider pulsars are known as black widows, which have accreted most of the mass from their binary companion star, and redbacks, which are currently accreting mass from their companions.

    Spider MSPs are particularly hard to find when searching in the radio regime due to excess gas from their companions obscuring the pulsed emission. However, since the Fermi Gamma-Ray Space Telescope started publishing catalogs of unassociated gamma-ray sources, many have been found to be spider MSPs in follow up radio observations.

    NASA/Fermi LAT


    NASA/Fermi Gamma Ray Space Telescope

    But today’s paper has, for the first time, confirmed the redback MSP nature of the gamma-ray source 3FGL J2039.6−5618 by detecting gamma-ray pulses before finding the radio pulses!

    A lesson in gamma-ray pulsar searching

    Many MSPs have binary companions, which is what makes searching for their gamma-rays pulses so difficult. Unlike in radio searches, gamma-ray searches need to know the orbital parameters of the binary system extremely accurately. This is because there are so few gamma-ray photons emitted from MSPs that the Doppler shift from the orbital motion of the MSP and its companion will smear out the pulses and make them undetectable. So how did the authors of this paper find these gamma-ray pulses?

    They used observations of 3FGL J2039.6−5618 that had been taken with the XMM-Newton X-ray Observatory , and optical observations with telescopes at the European Southern Observatory, GAIA, and the SOAR telescope, to constrain the orbit.

    ESA/XMM Newton

    These telescopes all found that 3FGL J2039.6−5618 had some kind of optical companion, most likely a main sequence star, and were able to trace out its orbital parameters. This suggested that this gamma-ray source was a redback MSP.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo,

    ESA/GAIA satellite


    SART telescope (SOAR) situated on Cerro Pachón, just to the southeast of Cerro Tololo on the AURA site at an altitude of 2,700 meters (8,775 feet) above sea level

    With orbital parameters in hand, the search for gamma-ray pulsations can begin. However, searching for these pulsations is extremely computational difficult, since many properties of the pulsar, such as its spin period, are still unknown. To help with the search, the authors utilized the Einstein@Home, a BOINC volunteer computing system.

    einstein@home

    This system splits up the huge amount of computation into small chunks, and then uses idle volunteer computers to process these small chunks, greatly increasing the speed of the search (you can sign up here if you’re interested). The results of this search found a periodic signal in the gamma-ray data with a 2.65 ms period, and a minimum companion mass of 0.15 solar masses, or a mass 0.15 times that of the Sun, confirming that 3FGL J2039.6−5618 is indeed a redback MSP, now confirmed as PSR J2039-5617.

    A lesson in gamma-ray pulsar timing

    1
    Figure 1: Left: The intensity of the gamma-ray emission as a function of the pulsar spin phase over time. The two clear black lines show the periodic increase in emission that is constant over time, indicating that this source is indeed a pulsar. The initial pulsar timing model parameters were used for this plot, and the wobble in the lines shows that this model may need to be further refined. Right: Same as left, but using the pulsar timing model parameters from the MCMC fitting. The clear straight lines show that this model is a significantly better fit than the original model (Figure 1 in the paper).

    Once the pulsar has been found, its parameters can be refined even more by timing it, a process that minimizes the differences between the model of when the gamma-ray pulses are detected and when the model predicts they will be detected. This can lead to better constraints on the orbital parameters of PSR J2039-5617, which in turn allows us to learn more about its binary companion and the nature of redback systems. For gamma-ray pulsars, this is a complicated process that the authors complete through Markov Chain Monte Carlo (MCMC) sampling. In an MCMC, value of the parameter are randomly chosen according to a predefined distribution (here, based on the initial orbital and pulsar parameters). The likelihood that the randomly chosen values match the data is then computed, and new values are chosen until the most likely values for each parameter are found. While this is a computationally long process, the results are worthwhile, as shown by the improvement in the pulsar binary model in the right panel of Figure 1 compared to the left panel.

    The timing model found using the gamma-ray detection can then be used to look for pulses in the X-ray emission of PSR J2039-5617, which were detected and are clearly shown with the gamma-ray pulses in Figure 2. From this modeling, the authors of today’s paper were able to learn more about PSR J2039-5617 than we have time to discuss here!

    2
    Figure 2: Top: Gamma-ray pulse profile of PSR J2039-5617. The profile is shown twice for clarity, with peaks at an orbital phase of 0.25 and 1.25 clearly visible. The y-axis shows the number of gamma-ray photons detected at each orbital phase, and the red line shows what the expected background gamma-ray count would be if there were no pulsar observed. Bottom: X-ray pulse profile of PSR J2039-5617. Here the number of X-ray photons observed per second as a function of the pulsar’s orbital phase. The peaks around phases of 0.6 and 1.6 clearly show a pulse of X-ray emission (Figure 3 in the paper.)

    Class takeaways

    There are many more unidentified gamma-ray sources from Fermi. If an X-ray or optical companion and orbit can be found, these sources can be searched for pulses and possibly confirmed as MSPs. While this may be just a small number of systems, they may be easier to confirm as pulsars by searching the gamma-rays than the radio observations. Additionally, the discovery of more redback MSPs will help us learn more about pulsar evolution and binary system formation. Timing these gamma-ray pulsars also improve models used to find pulses at other wavelengths. The model for PSR J2039-5617 was even used to detect radio pulses from it, as discussed in this companion paper [MNRAS]. With the first confirmation of a pulsar through gamma-ray pulsations, the future looks bright, literally.

    See the full article here .


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    Please help promote STEM in your local schools.

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    What do we do?

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

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

     
  • richardmitnick 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 .

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    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.

     
  • 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 .


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    Please help promote STEM in your local schools.

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    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.


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    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.

     
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