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  • richardmitnick 4:34 pm on February 9, 2018 Permalink | Reply
    Tags: , , , , , ING William Herschel Telescope, J0815+4729   

    From Astronomy Magazine: “One of the oldest stars in the Milky Way discovered” 

    Astronomy magazine

    Astronomy Magazine

    February 2, 2018
    Jake Parks

    J0815+4729 is a star with both an extreme iron deficiency and a carbon surplus, which suggests it’s one of the oldest stars ever found in the Milky Way.

    1
    Astronomers recently discovered one of the first stars formed in the Milky Way, J0815+4729, shown here in this artist concept. This low-mass star is one of the most iron-poor and carbon-rich stars found to date, suggesting it formed shortly after the Big Bang. Gabriel Pérez/SMM/IAC.

    In a new study published in The Astrophysical Journal Letters, a team of Spanish astronomers announced the discovery of one of the first stars to form in the Milky Way. The unevolved star, called J0815+4729, is located 7,500 light-years away in the halo of the Milky Way and likely formed just 300 million years after the Big Bang, some 13.5 billion years ago.

    “We know of only a few stars (which can be counted on the fingers of a hand) of this type in the halo [of the Milky Way], where the oldest and most metal-poor stars in our galaxy are found,” said David Aguado, a research student at the IAC and lead author of the study, in a press release.

    The ancient star, which is only 70 percent the mass of the Sun, was initially identified from a dataset generated by the Sloan Digital Sky Survey (SDSS) — a massive survey project that has gathered deep multi-color images for about one third of sky, as well as spectra for more than three million astronomical objects. The researchers specifically selected J0815+4729 for follow-up based on its apparent lack of metals — a term which astronomers apply to any elements larger than hydrogen and helium.

    The research team analyzed the light from J0815+4729 using the ISIS spectrograph on the William Herschel Telescope and the OSIRIS spectrograph on the Gran Telescopio Canarias.

    1
    ISIS spectrograph on the William Herschel Telescope


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

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

    Based on their spectroscopic follow-up, the team determined J0815+4729 has roughly a million times less calcium and iron than the Sun. This is important because only the earliest generations of stars have such low metallicities. Older stars, on the other hand, are formed out of the accumulated material from previous generations of stars, which produce lots of metals during their final death throes.

    Although J0815+4729 is extremely deficient in calcium and iron, the researchers’ were surprised to find that the star has a comparatively large abundance of carbon, nearly 15 percent more than the Sun. Though it may seem counter-intuitive, previous research suggests that low-mass, extremely metal-poor stars likely develop an overabundance of carbon by accreting it from the first generation of low-metallicity supernovae, which lived very short lives.

    Because J0815+4729 is so metal-poor while also being so carbon-rich, the researcher are confident the star formed long, long ago, when the Milky Way was just establishing itself some 13.5 billion years ago.

    “Theory predicts that these stars could form just after — and using material from — the first supernovae, whose progenitors were the first massive stars in the Galaxy, around 300 million years after the Big Bang,” said Jonay González Hernández, a researcher at IAC and co-author of the study.

    Though the researchers’ have already shown that J0815+4729 is likely one of — if not the — most iron-poor unevolved stars known, they still plan to collect higher-resolution spectra of the star to help derive other important elemental abundances. By doing so, the researchers aim to provide “new fundamental constraints on the early stages of the universe, the formation of the first stars, and the properties of the first supernovae.”

    See the full article here .

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  • richardmitnick 9:37 am on December 11, 2017 Permalink | Reply
    Tags: , , , , , ING William Herschel Telescope, The magnetism of black holes,   

    From IAC: “The magnetism of black holes” 

    IAC

    Instituto de Astrofísica de Canarias – IAC

    11/12/17

    The magnetism of black holes is surprisingly weak.

    1
    Artistic representation of a black hole with magnetic fields. Credit: Micheal McAaler / Uf News.

    According to a study published today in the journal Science, researchers at the University of Florida have discovered, with CIRCE instrument installed in the Gran Telescopio Canarias (GTC) of the Roque de los Muchachos Observatory (Garafía, La Palma), these objects, which are characterized by an intense gravitational pull devouring stars and launches streams of matter into space at nearly the speed of light, have significantly weaker than previously thought magnetic fields.

    V404 Cygni , the first black hole seen from Earth by a team of researchers from the Institute of Astrophysics of the Canary Islands (IAC), the news again. This time, thanks to him we have obtained the first accurate measurements of the magnetic field that surrounds these celestial objects. The authors of the study, published today in the journal Science, have found that the magnetic energy around this black hole is 400 times less than the estimates provided for .

    With these new measurements, scientists can better understand how magnetism of black holes, deepening our understanding of how matter behaves under extreme conditions works. These new data could extend the limits of nuclear fusion energy and GPS systems and applied to other research to reveal how the jets (jets of particles) shoot out of these heavenly depths, while everything around them is absorbed by they.

    “Our measurements surprisingly low, will force new restrictions on the theoretical models previously focused on strong magnetic fields that accelerate and direct the jet flows” explains Stephen Eikenberry, a professor of astronomy at the College of Liberal Arts and Sciences at the University of Florida and one of the study authors. Eikenberry says they did not expect these results.


    2
    William Herschel Telescope, La Palma., La Palma.

    The study’s authors developed the measurements from data collected during the outbreak in 2015 of jet black hole. This event was observed with the infrared camera CIRCE (Canarias InfraRed Camera Experiment), installed in the Gran Telescopio would win (GTC) and through Ultracam, the William Herschel Telescope, both at the Observatorio del Roque de los Muchachos (Garafía, La Palma) . X-ray observations of the California Institute of Technology and Space Telescope NASA NuSTAR were also used; and data arcminute Microkelvin Imager telescope located in the UK.

    NASA NuSTAR X-ray telescope

    3
    Arcminute Microkelvin Imager AMI cosmic microwave background CMB telescope Mullard Observatory Cambridge

    Yigit Dalilar, lead author, said that these explosions in black holes are ephemeral. In the case of outbreaks of V404 Cygni in 2015, barely they lasted a couple of weeks. “Watching him was something that happens once or twice in the race , ” said Dalilar. He noted that “this discovery puts us one step closer to understanding how the universe works.”

    The Gran Telescopio Canarias (GTC), installed at the Observatorio del Roque de los Muchachos (Garafía, La Palma) is part of the network of Singular Scientific and Technical Infrastructures (ICTS) of Spain.

    See the full article here.

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    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).
    The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teaching and outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.


    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

     
  • richardmitnick 2:50 pm on November 3, 2017 Permalink | Reply
    Tags: , , , , HiPERCAM installed and achieves first light, , ING William Herschel Telescope, ULTRACAM moved to ESO/NTT   

    From ING: “HiPERCAM Successfully Commissioned on the William Herschel Telescope” 

    Isaac Newton Group of Telescopes Logo
    Isaac Newton Group of Telescopes

    2 November, 2017
    Javier Mendez
    outreach@ing.iac.es

    HiPERCAM was successfully commissioned on the William Herschel Telescope (WHT) on 17 October 2017 by a team from the Universities of Sheffield, Warwick and the UK Astronomy Technology Centre, Edinburgh. HiPERCAM was designed as a next generation version of ULTRACAM.


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

    The latter instrument was used at the WHT from 2002 to 2015, and is now permanently located at the ESO NTT, where it continues to do science. HiPERCAM, on the other hand, will be based on La Palma, and moved between the WHT and Gran Telescopio Canarias. The instrument is funded by a 3.5Meuro ERC Advanced Grant awarded to Vik Dhillon and will be commissioned on the GTC in January 2018.

    2
    ULTRACAM from ING to ESO NTT

    3
    Close-up of HiPERCAM mounted at the Cassegrain focus of the WHT.

    6
    First light with HiPERCAM – the spiral galaxy NGC 7331.

    HiPERCAM is a very significant advance on ULTRACAM. It is able to image simultaneously in 5 channels (ugriz), rather than the 3 channels of ULTRACAM, and uses much higher throughput, larger optics than ULTRACAM, doubling the field of view to 10′ and hence providing brighter comparison stars for differential photometry.

    HiPERCAM can frame at (windowed) rates of 1.7kHz, rather than the maximum of 300Hz available with ULTRACAM. HiPERCAM uses detectors cooled to 180K (ULTRACAM’s are only cooled to 233K), with deep-depletion CCDs in the red channels, each equipped with anti-etaloning, resulting in much lower dark current, higher quantum efficiency and lower fringing than ULTRACAM. Hence, as well as high-speed work, HiPERCAM is ideal for scientific applications requiring deep, single-shot spectral-energy distributions.

    HiPERCAM will also be the first instrument to incorporate a novel scintillation-noise correction technique, known as conjugate-plane photometry, significantly reducing noise in light curves of bright objects such as transiting exoplanet host stars.

    See the full article here .

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    Isaac Newton Group telescopes
    Isaac Newton Group telescopes

    ING William Herschel Telescope
    ING William Herschel Interior
    ING William Herschel Telescope, at the Observatorio del Roque de los Muchachos on the island of La Palma in the Canary Islands, Spain

    ING Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands
    Isaac Newton 2.5m telescope interior
    ING Isaac Newton 2.5m telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, Spain

     
  • richardmitnick 7:56 am on May 2, 2017 Permalink | Reply
    Tags: , , , , , ING William Herschel Telescope, Superbubbles in the interstellar medium   

    From IAC: “Superbubbles in the interstellar medium” 

    IAC

    Instituto de Astrofísica de Canarias – IAC

    May. 1, 2017

    1

    Their detection in the interacting galaxies, the “Antennae”, was possible thanks to a new method –BUBBLY- developed by IAC researchers and the GHaFaS instrument installed on the

    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands

    .

    A team of scientists led by members of the Instituto de Astrofísica de Canarias (IAC), in collaboration with the Universidad Nacional Autónoma de México (UNAM), have detected and measured a complete “carpet” of expanding bubbles in the interstellar medium of the “Antennae”, a pair of galaxies in interaction which will eventually merge. The work, published in Monthy Notices of the Royal Astronomical Society is based technically on observations with an instrument called GHaFaS on the 4.2 m William Herschel Telescope, at the Roque de los Muchachos Observatory, (ORM) (Garafía, La Palma, Canary Islands). This instrument is capable of making a map of the velocities of a complete galaxy using the emission from the ionized hydrogen in its interstellar medium.

    To detect the huge bubbles in the combined galaxy disc, the team has used “BUBBLY”, a method developed by some of the current authors, and has already been published in the same journal in 2015. These huge bubbles in galaxy discs are caused by the stellar winds and supernova explosions in clusters of very hot very massive stars. They can range in size from a couple of light years to a thousand light years, depending on the number of stars in the cluster and how massive they are. The larger ones are often called “superbubbles”

    In the study published today, based on observations made with GHaFaS instrument, the BUBBLY method has been applied to the “Antennae”, in which the interaction between the galaxies is causing a major burst of star formation, leading to many star clusters, each surrounded by a bubble of expanding gas. The researchers have been able to calculate how much energy is being fed into the interstellar medium from each individual bubble, and from the sum total of all the bubbles, including a decent estimate for those which are too small to be fully detected. The group has initial evidence of the presence of the expanding bubbles in a wider sample of nearby galaxies and will process the results of the sample soon.

    “The importance of the bubbles” says Artemi Camps-Fariña, the lead author on both of the articles “is that they let us measure the effects of feedback caused by massive star clusters on the rest of the galaxy in which they lie. This is being recognized as very important. Theorists who aim to model how galaxies are formed and evolve had a major problem when they made models without this feedback.

    Without the bubbles, the formation of stars was far too quick and all the available gas would have been used up by the time the universe had reached one tenth of its present age. All the galaxies would by now be passive with no new stars forming. It is more than probable that the processes which eventually gave rise to life would not have had time to operate. But the feedback process, in which massive star clusters blow large bubbles, slows down the star formation by stopping new gas from condensing so quickly into stars. It reduces the overall star formation rate by a big factor, and has let galaxies such as the Milky Way produce their stellar populations in a much more extended time-frame.”

    “Although this general idea is not new” says John Beckman, one of the authors of both articles “our ability to measure the properties of the bubbles is giving us a way to quantify the effect and to match basic theory with the observed properties of galaxies”

    Article: Physical properties of superbubbles in the Antennae galaxies, by ArtemiCamps-Fariña, et al. Monthly Notices of the Royal Astronomical Society). https://arxiv.org/abs/1703.02902

    Article of 2015: BUBBLY: a method for detecting and characterizing interstellar bubbles using Fabry-Perot spectroscopy, By Artemi camp-Fariña et al. Monthly Notices of the Royal Astronomical 2015MNRAS.447.3840C

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).
    The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teaching and outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.


    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

     
  • richardmitnick 3:37 pm on December 12, 2016 Permalink | Reply
    Tags: , , , ING William Herschel Telescope, Mug Shot of an Icy Dwarf Planet   

    From astrobites: “Mug Shot of an Icy Dwarf Planet” 

    Astrobites bloc

    Astrobites

    Dec 12, 2016
    Mara Johnson-Groh

    Title: Rotationally Resolved Spectroscopy of a dwarf planet (136472) Makemake
    Authors: V. Lorenzi, N. Pinilla-Alonso, J.Licandro,
    First Author’s Institution: Fundacion Galileo Galilei-INAF, Spain
    Paper Status: Accepted to Astronomy & Astrophysics, 23 March 2015, open access

    In the far outer reaches of our solar system reside the small dwarf planets. These kid-brothers of the big eight official planets are often forgotten. The most well known is Pluto, but there are in fact over 1,650 known minor planets that orbit out past Neptune. The larger of these trans-Neptunian objects (TNOs) are big and cold enough to retain volatiles, like nitrogen (N2) and carbon monoxide (CO), on their surface. Studying these icy realms can tell us a lot about other, even smaller, icy bodies in the outer solar system and helps us form a more complete view of our solar system.

    The third largest dwarf planet is Makemake, or as it was originally christened, “Easterbunny” (it was discovered three days after Easter in 2005).

    2
    Dwarf planet Makemake and its moon S/2015 (136472) 1.
    NASA, ESA, A. Parker and M. Buie (Southwest Research Institute), W. Grundy (Lowell Observatory), and K. Noll (NASA GSFC)
    Makemake and its moon, as seen by the Hubble Space Telescope
    Discovery
    Discovered by Michael E. Brown Chad Trujillo David Rabinowitz

    Discovery date March 31, 2005
    Designations: MPC designation (136472) Makemake

    With a diameter around 1,400km, it’s about two and half times smaller than our moon, and it takes 310 Earth-years to orbit the sun. In order to better understand it’s surface, a Spanish team observed the dwarf planet over different rotational phases in 2008, the results of which are reported for the first time in this paper. They choose to look in the near-infrared where the volatiles show absorption bands. Using a spectrograph on the William Herschel Telescope they observed Makemake’s spectra over the 0.28 – 0.52 µm and 0.70 – 0.95 µm ranges.

    ING William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands
    ING William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands

    They split the spectra they observed into four sets with each group corresponding to a different phase of the dwarf planet’s rotation. This way they could look for rough variations across different parts of the the dwarf planet instead of global uniformities. Unfortunately, the data from the last phase was too noisy to use and was discarded, so in the end only 70% of the surface was imaged over three rotational phases. The three spectra are shown in Figure 1.

    They split the spectra they observed into four sets with each group corresponding to a different phase of the dwarf planet’s rotation. This way they could look for rough variations across different parts of the the dwarf planet instead of global uniformities. Unfortunately, the data from the last phase was too noisy to use and was discarded, so in the end only 70% of the surface was imaged over three rotational phases. The three spectra are shown in Figure 1.

    3
    Figure 1. Spectra from three phases of Makemake’s rotation, vertically offset for clarity. The blue and red lines correspond to the two wavelength coverages observed. Black dots come from a study by Licandro et al. in 2006.

    You’ll notice the blue side of the spectra is fairly featureless where as the red side has lot of absorption lines. These are due to methane-ice, which is abundant on the surface. Seven of these bands are marked in Figure 2. These lines are important for learning about the surface of the dwarf planet. In icy bodies, the broadness of the line is inversely proportional to the depth of the ice layer. In other words, the weaker the line, the thicker the layer is. Although the blue part of the spectra isn’t as visually appealing as the red, it still has a lot to tell us. By measuring the slope we can identify the presence of other organic compounds.

    4
    Figure 2. Spectra from three phases of Makemake’s rotation, vertically offset for clarity. The blue and red lines correspond to the two wavelength coverages observed. Black dots come from a study by Licandro et al. in 2006.

    Analyzing the spectra, it looks like Makemake is a closer twin to Pluto than Eris (the second largest dwarf planet). Turns out, the dwarf planet has more solids than volatiles. The absorption bands show that the methane is mixed with nitrogen in a solid state on the surface. Makemake has less nitrogen than Eris or Pluto, which makes sense for a smaller planet with less gravity to retain those volatiles.

    Since the three phases turned out to be nearly identical, it seems like the surface of Makemake is fairly uniform. However, more observations would be needed to confirm this.

    The authors also compared the spectra they took with observations done three years prior. They found no differences between the spectra meaning that the surface composition didn’t change significantly over three years. This makes sense given the dwarf planet didn’t get much closer to the sun (and thus warmer) over those three years.

    Although these observations of the distant icy world are far from complete, they can begin to give us a first look at the faces of Makemake.

    See the full article here .

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    What do we do?

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

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

     
  • richardmitnick 10:45 am on July 26, 2016 Permalink | Reply
    Tags: An Extremely Weak Magnetic Field in a White Dwarf, , , , ING William Herschel Telescope   

    From ING: “An Extremely Weak Magnetic Field in a White Dwarf” 

    Isaac Newton Group of Telescopes Logo
    Isaac Newton Group of Telescopes

    A team of astronomers reports the discovery of one of the very weakest magnetic fields ever securely detected in a white dwarf. The observation was made using the ISIS spectropolarimeter on the William Herschel Telescope (WHT), in just one hour of exposure time and using the red and the blue arms of the spectrograph. This is part of a large survey of bright white dwarfs to search for such weak magnetic fields.

    1
    First observation of Zeeman splitting in the core of Hydrogen alpha due to a field of about 60 kilogauss in WD2047+372. The ISIS observation is in blue, the ESPaDOnS observation (at higher resolving power) is shown in red. The circular polarisation spectrum is shown below the intensity profile, shifted up by +0.4 to facilitate comparison with the spectral line profile. The green lines bracketing the circular polarisation are ± one sigma. Figure extracted from Landstreet et al. (2016).

    The strength of the magnetic field found in LTT 16093 = WD2047+372 is only about 60 kilogauss (6 teslas), 2 or 3 orders of magnitude smaller than the typical fields of tens of megagauss found in a few percent of white dwarfs. The field was marginally detected in polarimetery, but clear Zeeman splitting into a triplet was present in the sharp core of Hydrogen alpha. This first detection using ISIS was confirmed by a spectropolarimetric observation a month later with the higher resolving power spectropolarimeter ESPaDOnS on the Canada-France-Hawaii Telescope [CFHT].

    CFHT ESPaDOns preferred
    CFHT ESPaDOns

    CFHT Telescope, Mauna Kea, Hawaii, USA
    CFHT Interior
    CFHT

    It is not yet understood how the magnetic fields of white dwarfs are formed, or how they evolve during white dwarf cooling. In spite of many detections of megagauss fields in white dwarfs, mostly very faint, little is known about the low-field regime, and very little modelling of the fields of individual white dwarfs is available. This current ISIS survey is intended to increase the very small sample and to provide data for detailed modelling, and ultimately to provide data to constrain field formation scenarios.

    It is found that ISIS is a very powerful tool for searches for such weak fields; it is able to detect fields of tens of kilogauss using either Hydrogen-alpha spectroscopy or spectropolarimetry of Hydrogen or Helium line wings, or both, in white dwarfs fainter than V = 15.

    More information:

    J. D. Landstreet, S. Bagnulo, A. Martin, and G. Valyavin, 2016, Discovery of an extremely weak magnetic field in the white dwarf LTT 16093 WD2047+372, A&A, 591, A80 [ADS ].

    See the full article here .

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  • richardmitnick 9:59 pm on July 17, 2016 Permalink | Reply
    Tags: ING William Herschel Telescope, ,   

    From ING: “Three Supernova Shells Around a Young Star Cluster” 

    Isaac Newton Group of Telescopes Logo
    Isaac Newton Group of Telescopes

    16 July, 2016

    A group of astronomers, led by researchers at the Instituto de Astrofísica de Canarias (IAC), has found the first known case of three supernova remnants one inside the other. Using a method developed within the group for detecting huge expanding bubbles of gas in interstellar space, they were observing the galaxy M33 in our Local Group of galaxies and found an example of a triple-bubble.

    Local Group. Andrew Z. Colvin 3 March 2011
    Local Group. Andrew Z. Colvin 3 March 2011

    The results help to understand the feedback phenomenon, a fundamental process controlling star formation and the dissemination of metals produced in massive stars.

    The group has been building up a database of these superbubbles with observations of a number of galaxies and, using the very high resolution 2D spectrograph GHaFaS (Galaxy Halpha Fabry-Perot System) on the William Herschel Telescope (WHT), has been able to detect and measure some tens of them in different galaxies, which range in size from a few light years to as big as a thousand light years across.

    Superbubbles around large young star clusters are known to have a complex structure due to the effects of powerful stellar winds and supernova explosions of individual stars, whose separate bubbles may end up merging into a superbubble, but this is the first time that they, or any other observers, have found three concentric expanding supernova shells. They are concentric because the supernovae which produced them exploded at intervals of only 10,000 years, close to simultaneously on astronomical timescales, so they are still relatively spherical and surround their parent star cluster.

    1
    Expansion maps of the three detected bubbles, which show the detected expansion velocity in each pixel, all in the same velocity scale. Overlaid are contours of the region’s Hydrogen alpha emission; it can be seen that the bubbles are roughly concentric with each other and the region. Figure extracted from Camps Fariña et al. (2016).

    “This phenomenon—says John Beckman, one of the co-authors on the paper—allows us to explore the interstellar medium in a unique way, we can measure how much matter there is in a shell, approximately a couple of hundred times the mass of the sun in each of the shells”. However, if it is known that a supernova expels only around ten times the mass of the sun, where do the second and third shells get their gas from if the first supernova sweeps up all the gas?

    The answer to that must come from the structure of the surrounding gas: the inhomogeneous interstellar medium. “It must be—says Artemi Camps Fariña, who is first author on the paper—that the interstellar medium is not at all uniform, there must be dense clumps of gas, surrounded by space with gas at a much lower density. A supernova does not just sweep up gas, it evaporates the outsides of the clumps, leaving some dense gas behind which can make the second and the third shells”.

    “The presence of the bubbles—adds Artemi— explains why star formation on cosmological timescales has been much slower than simple models of galaxy evolution predicted. These bubbles are part of a widespread feedback process in galaxy discs and if it were not for feedback, spiral galaxies would have very short lives, and our own existence would be improbable”, concludes. The idea of an inhomogeneous interstellar medium is not new, but the triple bubble gives a much clearer and quantitative view of the structure and the feedback process. The results will help theorists working on feedback to a better understanding of how this process works in all galaxy discs.

    Science paper:
    Three supernova shells around a young star cluster in M33

    See the full article here .

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  • richardmitnick 3:52 pm on July 23, 2015 Permalink | Reply
    Tags: , , ING William Herschel Telescope,   

    From ING: “WHT Observes Pluto in Support of NASA’s New Horizons Mission” 

    Isaac Newton Group of Telescopes Logo
    Isaac Newton Group of Telescopes

    17 July, 2015
    No Writer Credit

    The William Herschel Telescope (WHT) has participated in 2014 and 2015 in a worldwide campaign to spectroscopically follow up Pluto from the ground in support of the encounter of NASA’s New Horizons spacecraft with Pluto.

    ING William Herschel Telescope
    ING William Herschel Interior
    ING WHT

    Constant monitoring of the surface of Pluto is necessary because it is known to be spectrally and photometrically variable from season to season, and probably during the whole secular calendar. By gathering data at different wavelengths astronomers are able to characterize the distribution of the materials which make up the surface and atmosphere in different ways, from the layers of volatile ices (bright, whitish areas made up of methane, nitrogen, and carbon monoxide) to the more complex organic residues, which are reddish.

    Last year Pluto was already observed for six nights using the WHT. The spectra, obtained using ACAM and planned as a series of overrides, showed two principal characteristics of the surface of Pluto, the clearest being the absorption bands due to methane ice. The second characteristic is the continuum slope of the spectrum which is an indicator of the colour of the surface. This colouring agent is not uniformly distributed over Pluto’s surface, but changes significantly during its rotation period, which is 6.4 Earth days.

    Temp 0
    Images of Pluto taken from the New Horizons probe. Below, spectra from the observing campaign at the WHT in 2014. The difference between the two spectra indicates differences in the composition of the surface of the planet. The spectrum printed in yellow (dark zone) has a larger slope, which is associated with the presence of very dark complexes of organic materials, which seem to be abundant in the dark region to the left of the map. The spectrum printed in red (bright zone) has somewhat deeper absorption bands, which indicate that there is more methane ice in the bright heart-shaped zone. Credits: NASA-JHUAPL-SWRI & ORM team

    This year, the observations were planned in a similar way and for a period of 11 nights, from 3rd to 14th July, coinciding with the closest approach of New Horizons spacecraft with Pluto. The new spectra will provide an important independent calibration of the MVIC (Multispectral Visible Imaging Camera on board New Horizons).

    See the full article here.

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