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  • richardmitnick 2:49 pm on September 25, 2015 Permalink | Reply
    Tags: , , , Sun studies   

    From ESO- ESOcast 76: A Polarised View of Stellar Magnetism 


    European Southern Observatory

    Sep 25, 2015

    ESO telescopes are being used to search for the subtle signs of magnetic fields in other stars and even to map out the star spots on their surfaces. This information is beginning to reveal how and why so many stars, including our own Sun, are magnetic, and what the implications might be for life on Earth and elsewhere in the Universe.


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

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    Atacama Pathfinder Experiment (APEX) Telescope

     
  • richardmitnick 7:28 pm on September 6, 2015 Permalink | Reply
    Tags: , , , Sun studies   

    From NASA: “NASA’s ‘CLASP’ Mission Set to Gauge Upper Solar Chromosphere’s Magnetic Field” 

    NASA

    NASA

    Sep. 4, 2015
    Janet Anderson
    Marshall Space Flight Center, Huntsville, Ala.
    256-544-0034
    janet.l.anderson@nasa.gov

    1
    A NASA worker in a clean room at the National Space Science Technology Center in Huntsville, Alabama, checks out the CLASP instrument prior to shipping to White Sands Missile Range in New Mexico for its Sept. 3 launch. Credits: NASA/MSFC

    2
    Workers at Marshall conduct vertical cooling testing on the CLASP instrument during integration of the instrument hardware. Credits: NASA/MSFC

    The Chromospheric Lyman-Alpha Spectro-Polarimeter, or CLASP, payload developed by joint team from United States, Japan, Spain and France and led by the NASA Marshall Space Flight Center, was successfully flown on a NASA Black Brant IX suborbital sounding rocket at 1:01 p.m. EDT (11:01 a.m. MDT), September 3, from the White Sands Missile Range in New Mexico. The 1270 pound payload flew to an estimated altitude of 167 miles. Preliminary analysis shows that data was collected by the payload.

    Conducting science in space is never simple. Imagine trying to study a specific region of the sun, for example, from a vantage point some 93 million miles away, probing that area at a level of precision less than 0.1 percent — with less than five minutes to do the job.

    That’s the task facing scientists preparing to launch NASA’s CLASP instrument, a joint effort between the United States, Japan, Spain and France, to the edge of space on September 3. CLASP is shorthand for the Chromospheric Lyman-Alpha Spectro-Polarimeter, a high-tech telescope that will obtain unprecedented observations during that tiny window of opportunity, when it will study the sun for some 300 seconds.

    During that time, scientists anticipate CLASP will deliver the first-ever measurement of the magnetic field in the sun’s middle layers, the upper chromosphere and the transition region. To accomplish this, “it will measure the Hanle effect polarization of Lyman-Alpha in the solar chromosphere,” said Amy Winebarger, principal investigator for CLASP and a researcher in the Science Research Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

    She explained: “That’s is a very technical way of saying this instrument will attempt to measure a specific wavelength of ultraviolet light emitted by hydrogen ions in this solar region, and the polarization of this light can be correlated to the intensity and direction of the magnetic field. The polarization of this specific spectral line is extremely sensitive to magnetic fields, making CLASP more effective than previous measuring methods by a factor of 100.”

    What’s so important about that magnetic field? “It plays a crucial role in dictating the structure of the sun’s atmosphere,” said Winebarger’s CLASP colleague, NASA astrophysicist Jonathan Cirtain. “It also acts as a conduit for mass and energy to flow into the solar corona and solar wind — some of it heading toward us as powerful solar flares that can disrupt Earth satellites. It’s critical to understand the process by which the sun releases these bursts of energy.”

    Winebarger, Cirtain and their team are no strangers to this research. They developed two previous sounding-rocket solar experiments, the High Resolution Coronal Imager, or Hi-C, which launched in 2012, and the Solar Ultraviolet Magnetograph Instrument, or SUMI, which completed its second research flight in 2012. Cirtain also was project scientist for Hinode, the joint Japanese-American mission launched in 2006 to study the sun. Hinode’s Solar Optical Telescope conducted some of the same spectropolarimetric observations CLASP will make — but peered much deeper into the sun’s photosphere, or surface, studying more readily accessible optical light and vector magnetic fields.

    CLASP owes a lot to those previous missions — and to its international team of contributors, Winebarger said. It is based on pioneering theoretical research by Javier Trujillo-Bueno and his team at the Instituto de Astrofísica de Canarias in Santa Cruz de Tenerife, Spain. SUMI and Hi-C provided the inspiration for CLASP’s optical layout, electronics and electrical interface. Its internal structure and optics were provided by the National Astronomical Observatory of Japan in Tokyo. Additional optical contributions were made by the Institut d’Astrophysique Spatiale in Paris. Finally, the cameras that will image the sun, delivering more stable, high-speed images and less noise than their predecessors, were developed in-house at Marshall by researchers in the Engineering Directorate’s Space Systems Department.

    The flight experiment will ride on a Black Brant IX sounding rocket launched from White Sands Missile Range in New Mexico. CLASP is supported through NASA’s Sounding Rocket Program at the agency’s Wallops Flight Facility on Wallops Island, Virginia, which is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. NASA’s Heliophysics Division manages the sounding-rocket program.

    The mission is a joint effort between NASA, the Japan Aerospace Exploration Agency headquartered in Chofu, the Instituto de Astrofísica de Canarias and the Institut d’Astrophysique Spatiale. Additional partners include the Lockheed Martin Solar Astrophysics Laboratory in Palo Alto, California, and the University of Alabama in Huntsville.

    Learn more about NASA space science and heliophysics research at http://www.nasa.gov.

    See the full article here .

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

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

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

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

     
  • richardmitnick 12:47 pm on May 22, 2015 Permalink | Reply
    Tags: , , Sun studies   

    From NASA: “Coronal Loops Over a Sunspot Group” 

    NASA

    NASA

    May 22, 2015
    Sarah Loff

    1
    Image Credit: NASA SDO

    The Atmospheric Imaging Assembly (AIA) instrument aboard NASA’s Solar Dynamics Observatory (SDO) images the solar atmosphere in multiple wavelengths to link changes in the surface to interior changes. Its data includes images of the sun in 10 wavelengths every 10 seconds. When AIA images are sharpened a bit, such as this AIA 171Å channel image, the magnetic field can be readily visualized through the bright, thin strands that are called “coronal loops”. Loops are shown here in a blended overlay with the magnetic field as measured with SDO’s Helioseismic and Magnetic Imager underneath. Blue and yellow represent the opposite polarities of the magnetic field. The combined images were taken on Oct. 24, 2014, at 23:50:37 UT.

    NASA SDO
    SDO

    See the full article here.

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

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

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

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

     
  • richardmitnick 6:46 pm on May 14, 2015 Permalink | Reply
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    From Subaru: “Subaru Telescope Observers Superflare Stars with Large Starspots” 

    NAOJ

    NAOJ

    May 11, 2015
    No Writer Credit

    A team of astronomers has used the High Dispersion Spectrograph on the Subaru Telescope to conduct spectroscopic observations of Sun-like “superflare” stars first observed and cataloged by the Kepler Space Telescope.

    NASA Kepler Telescope
    NASA/Kepler

    The investigations focused on the detailed properties of these stars and confirmed that Sun-like stars with large starspots can experience superflares.

    The team, made up of astronomers from Kyoto University, University of Hyogo, the National Astronomical Observatory of Japan (NAOJ), and Nagoya University, targeted a set of solar-type stars emitting very large flares that release total energies 10-10000 times greater than the biggest solar flares. Solar flares are energetic explosions in the solar atmosphere and are thought to occur by intense releases of magnetic energy around the sunspots. Large flares often cause massive bursts of high-speed plasma called coronal mass ejections (CMEs), can lead to geomagnetic storms on Earth. Such storms can have severe impacts on our daily life by affecting such systems as communications and power grids.

    This work follows up on observations made in 2012 (Maehara et al. Nature on 2012 May 24), where the team reported finding several hundred superflares on solar-type stars by analyzing stellar observation data from Kepler Space Telescope. This discovery was very important since it enabled the astronomers to conduct statistical analysis of superflares for the first time. However, more detailed observations were needed to investigate detailed properties of superflare stars and whether such massive flares can occur on ordinary single stars similar to our Sun.

    1
    Figure 1: Left: The brightness variation of solar-type superflare stars (from Kepler data). In addition to the sudden brightenings caused by flares, quasi-periodic brightness variations with periods of about 15 days are seen. Right: An artificial image of a superflare star seen with visible light. This figure shows a large superflare (shown in white) occurring in the large starspot area. (Credit: Kyoto University)

    Based on the initial discovery, the team carried out spectroscopic observations on 50 solar-type superflare stars selected from the Kepler Space Telescope’s data. From the investigation of the detailed properties of spectral lines, the team obtained the following results:

    1. More than half the observed 50 stars show no evidence of binarity (that is, they are not binary stars). The team confirmed the characteristics of the target stars as similar to those of the Sun.
    2. On the basis of the Kepler data, superflare stars show somewhat regular, periodic changes in their brightnesses. The typical periods range from one day to a few tens of days. Such variations are explained by the rotation of the star and its starspots. As shown in Figure 1, the stars seem to become dimmer when their starspots are on their visible sides. Moreover, the timescales of the brightness variations should correspond to the stars’ rotation speeds. Spectroscopic observations allow observers to estimate the rotation velocity from the broadening of absorption lines (Figure 2), and confirm that a velocity derived from spectroscopic data matches the brightness variation timescale as the star rotates. In addition, the measured rotation velocity of some target superflare stars is as slow as that of the Sun.
    3. Based on solar observations, astronomers know that if there are large dark star spots on a stellar surface, the “core depth” (the depth and width of a spectral line) of the Ca II 854.2[nm] (ionized Calcium) absorption line becomes shallow. Using this, they investigated the core depth of Ca II 854.2 [nm] line, and found that superflare stars have large starspots compared to sunspots (Figure 3).

    The results of these observations and analysis confirm that stars similar to the Sun can have superflares if they have large starspots. In the future, in addition to the continuing spectroscopic observations with Subaru Telescope, the team will conduct observations with the Kyoto University’s Okayama 3.8m telescope, which is now under construction.

    4
    Kyoto University’s Okayama 3.8m telescope

    This will allow them to investigate more detailed properties and changes in long-term activity of superflare stars.

    2
    Figure 2: Left: Four neutral iron (Fe I) absorption lines are shown. As mentioned above, spectral lines show some broadening because of the Doppler effect on the light from the rotating stellar surface. Slowly rotating stars like the Sun have a narrow line profile, while rapidly rotating stars have a wide line profile. Measuring these broadenings allows an estimate of the stellar rotation velocity. Right: The wavelength of light from the surface of a rotating star shifts because of the Doppler effect. For example, the wavelength of light from point A becomes a bit short (is blue-shifted) since this point is approaching us (the observer). By contrast, the wavelength of light from point C is a bit long (is red-shifted) since this point moves away from us. The wavelengths of light from point B have no shifts since this point moves perpendicular to the line of sight. Finally, this line-shift effect results in broadening of spectral lines. (Credit: Kyoto University)

    3
    Figure 3: Left: The bottom two images show the Sun in visible light (left) and the Ca II line (right) (These two pictures are from the Big Bear Solar Observatory). The upper two images are imaginary drawings of a superflare star in visible light (left) and the Ca II line (right) where the areas around the starspots are bright. Right:Absorption line of Ca II 854.2[nm] (ionized calcium). Superflare stars (the upper two spectra, shown in red and blue) have a shallow (bright) core depth compared to the Sun (the bottom spectrum, in black). This suggests that these two superflare stars have large starspots. (Credit: Kyoto University)

    Research Team Members

    Yuta Notsu (Department of Astronomy, Kyoto University)
    Satoshi Honda (Center for Astronomy, University of Hyogo)
    Hiroyuki Maehara (Okayama Astrophysical Observatory, NAOJ)
    Shota Notsu (Department of Astronomy, Kyoto University)
    Takuya Shibayama (Solar-Terrestrial Environment Laboratory, Nagoya University)
    Daisaku Nogami (Department of Astronomy, Kyoto University)
    Kazunari Shibata (Kwasan and Hida Observatories, Kyoto University)

    This research is based on the following two research papers.
    Paper 1:
    High Dispersion Spectroscopy of Solar-type Superflare Stars. I. Temperature, Surface Gravity, Metallicity, and v sin i
    Paper 2:
    High Dispersion Spectroscopy of Solar-type Superflare Stars. II. Stellar Rotation, Starspots, and Chromospheric Activities
    Authors of both papers:
    Notsu, Y., Honda, S., Maehara, H., Notsu, S., Shibayama, T., Nogami, D., and Shibata, K.
    To be published on Publications of the Astronomical Society of Japan June 25, 2015 issue (Online versions are published in February 22, 2015 and March 29, 2015, respectively)

    This work was supported by the Grant-in-Aids from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No.25287039, 26400231, and 26800096).

    See the full article here.

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    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ALMA Array
    ALMA

    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
  • richardmitnick 1:04 pm on May 4, 2015 Permalink | Reply
    Tags: , , , Sun studies   

    From NASA: “Bright Filament Eruption” 

    NASA

    NASA

    May 4, 2015
    Holly Zell

    1

    An elongated solar filament that extended almost half the sun’s visible hemisphere erupted into space on April 28-29, 2015, in a large burst of bright plasma. Filaments are unstable strands of solar material suspended above the sun by magnetic forces. Solar astronomers around the world had their eyes on this unusually large filament and kept track as it erupted. Both of the coronagraph instruments on the joint ESA/NASA Solar and Heliospheric Observatory, or SOHO, show the coronal mass ejection associated with the eruption.

    NASA SOHO
    SOHO

    The top image was taken by SOHO’s LASCO C2 coronagraph and the bottom by LASCO C3.

    LASCO, which stands for Large Angle Spectrometric Coronagraph [ on board SOHO], is able to take images of the solar corona by blocking the light coming directly from the Sun with an occulter disk, creating an artificial eclipse within the instrument itself. C2 images show the inner solar corona up to 8.4 million kilometers (5.25 million miles) away from the Sun. C3 images have a larger field of view: They encompass 32 diameters of the Sun. To put this in perspective, the diameter of the images is 45 million kilometers (about 30 million miles) at the distance of the Sun, or half of the diameter of the orbit of Mercury. The white circle in the center of the round disk represents the size of the sun, which is being blocked by the telescope in order to see the fainter material around it.

    Credit: ESA/NASA/SOHO

    See the full article here.

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

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

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

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

     
  • richardmitnick 8:42 am on April 30, 2015 Permalink | Reply
    Tags: , , , , Sun studies   

    From phys.org: ” New solar telescope unveils the complex dynamics of sunspots’ dark cores” 

    physdotorg
    phys.org

    NJIT Bloc

    April 29, 2015
    No Writer Credit

    NJIT Big Bear Solar Observatory
    NJIT Big Bear Solar Observatory Interior
    NJIT Big Bear Solar Observatory

    1

    Groundbreaking images of the Sun captured by scientists at NJIT’s Big Bear Solar Observatory (BBSO) give a first-ever detailed view of the interior structure of umbrae – the dark patches in the center of sunspots – revealing dynamic magnetic fields responsible for the plumes of plasma that emerge as bright dots interrupting their darkness. Credit: NJIT’s Big Bear Solar Observatory

    Their research is being presented this week at the first Triennial Earth-Sun Summit meeting between the American Astronomical Society’s Solar Physics Division and the American Geophysical Union’s Space Physics and Aeronomy section in Indianapolis, Ind.

    The high-resolution images, taken through the observatory’s New Solar Telescope (NST), show the atmosphere above the umbrae to be finely structured, consisting of hot plasma intermixed with cool plasma jets as wide as 100 kilometers.

    NJIT Big Bear Solar Observatory New Solar Telescope
    NST

    “We would describe these plasma flows as oscillating cool jets piercing the hot atmosphere. Until now, we didn’t know they existed. While we have known for a long time that sunspots oscillate – moderate resolution telescopes show us dark shadows, or penumbral waves, moving across the umbra toward the edge of a sunspot – we can now begin to understand the underlying dynamics,” said Vasyl Yurchyshyn, a research professor of physics at NJIT and the lead author of two recent journal articles based on the NST observations.

    Called spikes, the oscillating jets result from the penetration of magnetic and plasma waves from the Sun’s photosphere – the light-giving layer of its atmosphere – into the abutting chromosphere, which they reach by traveling outward along magnetic tubes that serve as energy conduits. “This process can be likened to a blowhole at a rocky beach, where relentless onshore waves jet sea water high into the air,” Yurchyshyn said.

    Sunspots are formed when strong magnetic fields rise up from the convection zone, a region beneath the photosphere that transfers energy from the interior of the Sun to its surface. At the surface, the magnetic fields concentrate into bundles, which prevent the hot rising plasma from reaching the surface. This energy deficit causes the magnetic bundles to cool down to temperatures about 1,000 degrees lower than their surroundings. They therefore appear darker against the hotter, brighter background.

    “But the magnetic field is not a monolith and there are openings in the umbra from which plasma bursts out as lava does from a volcano’s side vents. These plumes create the bright, nearly circular patches we call umbral dots,” Yurchyshyn noted. “Sunspots that are very dark have strong magnetic fields and thus fewer openings.”

    Compact groups of fast-changing sunspots create tension in their magnetic systems, which at some point erupt to relieve the stress. It is those eruptions that cause intense “space weather” events in the Earth’s magnetosphere affecting communications, power lines, and navigation systems.

    “We had no sense of what happens inside an umbra until we were able to see it in the high-resolution images obtained with the world’s largest solar telescope. These data revealed to us unprecedented details of small-scale dynamics that appear to be similar in nature to what we see in other parts of the Sun,” Yurchyshyn said. “There is growing evidence that these dynamic events are responsible for the heating of coronal loops, seen in ultraviolet images as bright magnetic structures that jet out from the Sun’s surface. This is a solar puzzle we have yet to solve.”

    Since it began operating in 2009, Big Bear’s NST has given scientists a closer look at sunspot umbrae, among other solar regions. It has also allowed them to measure the shape of chromospheric spectral lines, enabling scientists to probe solar conditions.

    “These measurements tell us about the speed, temperature, and pressure of the plasma elements we are observing, as well as the strength and the direction of the solar magnetic fields,” said Yurchyshyn, who is also a distinguished scholar at the Korea Astronomy and Space Science Institute. “Thus we were able to find that spikes, or oscillating jets, are caused by chromospheric shocks, which are abrupt fluctuations in the magnetic field and plasma that constantly push plasma up along nearly the same magnetic channels.”

    The study on umbral spikes was published in the Astrophysical Journal in 2014.

    In a second paper published in the Astrophysical Journal in 2015, he is presenting another set of NST observations, taking a closer look at the sunspot oscillations that occur every three minutes and are thought to produce bright umbral flashes – emissions of plasma heated by shock waves.

    The NST takes snapshots of the Sun every 10 seconds, which are then strung together as a video to reveal fast-evolving small explosions, plasma flows and the movement of magnetic fields. “We were able to obtain photographs of these flashes of unique clarity that allowed us to follow their development inside the umbra,” he said. Previously believed to be diffuse patches randomly distributed over the umbra, the researchers found their location is in fact not random. They mainly form along so-called sunspot umbral light bridges, which are very large openings in the sunspot magnetic fields that often split an umbra into two or more parts.

    “Even more importantly, we found that umbral flash lanes tend to appear on the side of light bridges that face the center of the sunspot,” he added. “This finding is significant because it indicates that sunspot oscillations may be driven by one energy source located under the umbra. There are simulations that appear to reproduce what we have observed, which is very encouraging. We, as a community, are finally in the position to be able to directly compare the observations and the state-of-the-art simulation results, which is the key to making further progress in our field.”

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) 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, Phys.org’s readership has grown steadily to include 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 11:16 am on February 7, 2015 Permalink | Reply
    Tags: , , , Sun studies   

    From NYT: “Living With a Star” 

    New York Times

    The New York Times

    FEB. 4, 2015
    Dennis Overbye

    1

    It is a fact rarely appreciated by the general public that to professional astronomers, the Sun is a pretty boring star. Which in fact is great news for the rest of us.

    It doesn’t oscillate or explode, periodically scorching us or freezing us out. In all of recorded history, as far as scientists have been able to tell, the sun’s output has varied by only a tenth of a percent.

    But it is still a star that we live with, and stars can be temperamental — ask any Hollywood agent.

    Our star is an enormous thermonuclear furnace more than a million times as big as Earth. At its center, where the temperature is 15 million degrees, 600 million tons of hydrogen are fused into 596 million tons of helium every second.

    The missing four million tons are transformed into energy. They become sunshine; they are the mortgage payment for life on Earth.

    Even a slight change in this precariously controlled violence can have drastic consequences on Earth. And so astronomers have been keeping careful watch on the sun in recent years as the number of sunspots blotting its surface approached an 11-year peak in 2014, ushering in what is often a season of dangerous storms on the sun.

    Glimpsed in the light of glowing hydrogen, the solar surface seethes and bubbles like boiling oatmeal. Guided by intense magnetic fields, jets of gas rise and fall like rain along arcs that can reach far into the corona, a thin haze of million-degree electrified gas visible during solar eclipses.

    So-called sunspots, which look dark only compared with the brilliance of the disk around them, occur in some regions where intense magnetic fields choke off the rising energy. They wax and wane in concert with the sun’s magnetic field, which reverses its direction every 11 years.

    Every sunspot cycle is slightly different and unpredictable. For the last half of the 17th century and partway into the next, sunspots nearly disappeared from the sun. That period corresponded to a prolonged era of European winters known as the Little Ice Age, and some astronomers have suggested there is a connection between low magnetic and sunspot activity and cooler temperatures on Earth.

    Along with high sunspot numbers comes a greater frequency of storms known as solar flares that can rattle the entire solar system.

    Recent observations with NASA’s Solar Dynamics Observatory have detailed how magnetic lines of force can snap like overstretched rubber bands, releasing as much energy as 160 billion hydrogen bombs on the sun’s surface.

    NASA Solar Dynamics Observatory
    NASA/SDO

    These explosions can launch monstrous globs of high-energy particles and radiation into space. Radiation from these storms is one of the major health threats that astronauts could face on the long voyage to Mars.

    When such a glob of gas hits our planet, Earth’s magnetosphere cushions the blow. High-energy particles are funneled to the magnetic poles, where they create the dazzling displays known as the Northern or Southern Lights. But they can also wreak electrical havoc, causing blackouts and blinding satellites crucial to modern life and the national defense.

    A solar flare in 1859 produced auroral lights as far south as Hawaii and set telegraphs sparking.

    Sunspots recently peaked again in 2014 and are still dangerously high. So far the planet has escaped any direct hits this time around, but scientists are keeping a weather eye on the good old sun.

    Living with a star is exciting, but it requires eternal vigilance for the inevitable outbursts.

    See the full article here.

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  • richardmitnick 8:05 am on February 1, 2015 Permalink | Reply
    Tags: , , Sun studies   

    From Space.com: “Earth’s Sun: Facts About the Sun’s Age, Size and History” 

    space-dot-com logo

    SPACE.com

    November 20, 2014
    Charles Q. Choi

    temp
    Credit: NASA

    The sun lies at the heart of the solar system, where it is by far the largest object. It holds 99.8 percent of the solar system’s mass and is roughly 109 times the diameter of the Earth — about one million Earths could fit inside the sun.

    The visible part of the sun is about 10,000 degrees Fahrenheit (5,500 degrees Celsius), while temperatures in the core reach more than 27 million F (15 million C), driven by nuclear reactions. One would need to explode 100 billion tons of dynamite every second to match the energy produced by the sun, according to NASA.

    The sun is one of more than 100 billion stars in the Milky Way. It orbits some 25,000 light-years from the galactic core, completing a revolution once every 250 million years or so. The sun is relatively young, part of a generation of stars known as Population I, which are relatively rich in elements heavier than helium. An older generation of stars is called Population II, and an earlier generation of Population III may have existed, although no members of this generation are known yet.

    Formation & evolution

    The sun was born about 4.6 billion years ago. Many scientists think the sun and the rest of the solar system formed from a giant, rotating cloud of gas and dust known as the solar nebula. As the nebula collapsed because of its gravity, it spun faster and flattened into a disk. Most of the material was pulled toward the center to form the sun.

    The sun has enough nuclear fuel to stay much as it is now for another 5 billion years. After that, it will swell to become a red giant. Eventually, it will shed its outer layers, and the remaining core will collapse to become a white dwarf. Slowly, this will fade, to enter its final phase as a dim, cool theoretical object sometimes known as a black dwarf.

    2
    A huge solar filament snakes around the southwestern horizon of the sun in this full disk photo taken by NASA’s Solar Dynamics Observatory on Nov. 17, 2010.
    Credit: NASA SDO

    Internal structure and atmosphere

    The sun and its atmosphere are divided into several zones and layers. The solar interior, from the inside out, is made up of the core, radiative zone and the convective zone. The solar atmosphere above that consists of the photosphere, chromosphere, a transition region and the corona. Beyond that is the solar wind, an outflow of gas from the corona.

    The core extends from the sun’s center to about a quarter of the way to its surface. Although it only makes up roughly 2 percent of the sun’s volume, it is almost 15 times the density of lead and holds nearly half of the sun’s mass. Next is the radiative zone, which extends from the core to 70 percent of the way to the sun’s surface, making up 32 percent of the sun’s volume and 48 percent of its mass. Light from the core gets scattered in this zone, so that a single photon often may take a million years to pass through.

    The convection zone reaches up to the sun’s surface, and makes up 66 percent of the sun’s volume but only a little more than 2 percent of its mass. Roiling “convection cells” of gas dominate this zone. Two main kinds of solar convection cells exist — granulation cells about 600 miles (1,000 kilometers) wide and supergranulation cells about 20,000 miles (30,000 kilometers) in diameter.

    The photosphere is the lowest layer of the sun’s atmosphere, and emits the light we see. It is about 300 miles (500 km) thick, although most of the light comes from its lowest third. Temperatures in the photosphere range from 11,000 F (6,125 C) at bottom to 7,460 F (4,125 C) at top. Next up is the chromosphere, which is hotter, up to 35,500 F (19,725 C), and is apparently made up entirely of spiky structures known as spicules typically some 600 miles (1,000 km) across and up to 6,000 miles (10,000 km) high.

    After that is the transition region a few hundred to a few thousand miles or kilometers thick, which is heated by the corona above it and sheds most of its light as ultraviolet rays. At the top is the super-hot corona, which is made of structures such as loops and streams of ionized gas. The corona generally ranges from 900,000 F (500,000 C) to 10.8 million F (6 million C) and can even reach tens of millions of degrees when a solar flare occurs. Matter from the corona is blown off as the solar wind.

    Magnetic field

    The strength of the sun’s magnetic field is typically only about twice as strong as Earth’s field. However, it becomes highly concentrated in small areas, reaching up to 3,000 times stronger than usual. These kinks and twists in the magnetic field develop because the sun spins more rapidly at the equator than at the higher latitudes and because the inner parts of the sun rotate more quickly than the surface. These distortions create features ranging from sunspots to spectacular eruptions known as flares and coronal mass ejections. Flares are the most violent eruptions in the solar system, while coronal mass ejections are less violent but involve extraordinary amounts of matter — a single ejection can spout roughly 20 billion tons (18 billion metric tons) of matter into space.

    Chemical composition

    Just like most other stars, the sun is made up mostly of hydrogen, followed by helium. Nearly all the remaining matter consists of seven other elements — oxygen, carbon, neon, nitrogen, magnesium, iron and silicon. For every 1 million atoms of hydrogenin the sun, there are 98,000 of helium, 850 of oxygen, 360 of carbon, 120 of neon, 110 of nitrogen, 40 of magnesium, 35 of iron and 35 of silicon. Still, hydrogen is the lightest of all elements, so it only accounts for roughly 72 percent of the sun’s mass, while helium makes up about 26 percent.

    Sunspots & solar cycles

    Sunspots are relatively cool, dark features on the sun’s surface that are often roughly circular. They emerge where dense bundles of magnetic field lines from the sun’s interior break through the surface. [Related: Largest Sunspot in 24 Years Wows Scientists, But Also Mystifies]

    The number of sunspots varies as solar magnetic activity does— the change in this number, from a minimum of none to a maximum of roughly 250 sunspots or clusters of sunspots and then back to a minimum, is known as the solar cycle, and averages about 11 years long. At the end of a cycle, the magnetic field rapidly reverses its polarity.
    Observation & history

    Ancient cultures often modified natural rock formations or built stone monuments to mark the motions of the sun and moon, charting the seasons, creating calendars and monitoring eclipses. Many believed the sun revolved around the Earth, with ancient Greek scholar Ptolemy formalizing this “geocentric” model in 150 B.C. Then, in 1543, Nicolaus Copernicus described a heliocentric, sun-centered model of the solar system, and in 1610, Galileo Galilei’s discovery of Jupiter’s moons revealed that not all heavenly bodies circled the Earth.

    To learn more about how the sun and other stars work, after early observations using rockets, scientists began studying the sun from Earth orbit. NASA launched a series of eight orbiting observatories known as the Orbiting Solar Observatory between 1962 and 1971. Seven of them were successful, and analyzed the sun at ultraviolet and X-ray wavelengths and photographed the super-hot corona, among other achievements.

    NASA Orbiting Solar Observatory
    OSO

    In 1990, NASA and the European Space Agency launched the Ulysses probe to make the first observations of its polar regions. In 2004, NASA’s Genesis spacecraft returned samples of the solar wind to Earth for study. In 2007, NASA’s double-spacecraft Solar Terrestrial Relations Observatory (STEREO) mission returned the first three-dimensional images of the sun.

    NASA Ulysses
    Ulysses

    NASA Genesis spacecraft
    Genesis

    NASA STEREO spacecraft
    Stereo

    One of the most important solar missions to date has been the Solar and Heliospheric Observatory (SOHO), which was designed to study the solar wind, as well as the sun’s outer layers and interior structure. It has imaged the structure of sunspots below the surface, measured the acceleration of the solar wind, discovered coronal waves and solar tornadoes, found more than 1,000 comets, and revolutionized our ability to forecast space weather. Recently, NASA’s Solar Dynamics Observatory (SDO), the most advanced spacecraft yet designed to study the sun, has returned never-before-seen details of material streaming outward and away from sunspots, as well as extreme close-ups of activity on the sun’s surface and the first high-resolution measurements of solar flares in a broad range of extreme ultraviolet wavelengths.

    NASA SOHO
    SOHO

    NASA SDO
    SDO

    Additional reporting by Nola Taylor Redd

    See the full article here.

    Please help promote STEM in your local schools.

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