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  • richardmitnick 8:40 pm on September 21, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From The Daily Galaxy: “The Weekend Image: Dwarf Dark-Matter Galaxy 10 Billion Light Years from Earth” 

    Daily Galaxy
    The Daily Galaxy

    September 20, 2014
    No Writer Credit

    Galaxies such as our own Milky Way are believed to form over billions of years through the coming together of many smaller galaxies. As a result, it is expected that there should be many smaller dwarf galaxies scattered around the Milky Way. However, very few of these tiny relic galaxies have been observed, which has led astronomers to conclude that many of them must have very few stars or may be made almost exclusively of dark matter.

    In a discovery made in 2012, a team of researchers found a dark dwarf galaxy about 10 billion light years from Earth. It is only the second such galaxy ever observed outside our local region of the universe, and is by far the most distant.


    The newly discovered dwarf galaxy is a satellite, meaning it clings to the edges of a larger galaxy.

    “For several reasons, it didn’t manage to form many or any stars, and therefore it stayed dark,” said Simona Vegetti, a Pappalardo Fellow in MIT’s Department of Physics.

    Scientists theorize the existence of dark matter to explain observations that suggest there is far more mass in the universe than can be seen. They believe that dark matter should comprise about 25 percent of the universe; however, because the particles that make up dark matter do not absorb or emit light, they have so far proven impossible to detect and identify.

    Computer modeling suggests that the Milky Way should have about 10,000 satellite galaxies, but only 30 have been observed. “It could be that many of the satellite galaxies are made of dark matter, making them elusive to detect, or there may be a problem with the way we think galaxies form,” Vegetti said.

    The team turned to more distant galaxies to search for dark satellites, using a method called gravitational lensing. To use this technique, researchers find two galaxies aligned with each other, as viewed from Earth. The more distant galaxy emits light rays that are deflected by the closer galaxy (which acts as a lens). By analyzing the patterns of light rays deflected by the foreground lens galaxy, the researchers can determine if there are any satellite galaxies clustered around it and measure how massive they are.

    “It’s really exciting that we not only have a method in hand to test predictions from the cold dark matter model, but also made a discovery of such a low mass dark satellite hundreds of times farther out in the universe compared to our local group of galaxies,” said Leon Koopmans of the University of Groningen in the Netherlands.

    The researchers used the Keck-II Telescope in Hawaii to make their observations, taking advantage of a special piece of optical equipment that provides sharp images of the sky. They plan to use the same method to look for more satellite galaxies in other regions of the universe, which they believe could help corroborate or challenge predictions of how dark matter behaves.

    Keck Observatory
    Keck Observatory Interior

    “Now we have one dark satellite, but suppose that we don’t find enough of them — then we will have to change the properties of dark matter,” Vegetti said. “Or, we might find as many satellites as we see in the simulations, and that will tell us that dark matter has the properties we think it has.”

    For example, because temperature determines the mass and number of satellites that form, it may be necessary to adjust the current temperature estimates for dark matter if the number of dark satellites found is less than projected.

    “The existence of this low-mass dark galaxy is just within the bounds we expect if the universe is composed of dark matter that has a cold temperature. However, further dark satellites will need to be found to confirm this conclusion,” observed Vegetti.

    See the full article here.

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  • richardmitnick 3:35 pm on September 20, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From NASA: A Colorful Lunar Eclipse 

    NASA Science Science News

    Mark your calendar: On Oct. 8th, the Moon will pass through the shadow of Earth for a total lunar eclipse. Sky watchers in the USA will see the Moon turn a beautiful shade of celestial red and maybe turquoise, too. Watch, enjoy, learn.

    NASA leads the nation on a great journey of discovery, seeking new knowledge and understanding of our planet Earth, our Sun and solar system, and the universe out to its farthest reaches and back to its earliest moments of existence. NASA’s Science Mission Directorate (SMD) and the nation’s science community use space observatories to conduct scientific studies of the Earth from space to visit and return samples from other bodies in the solar system, and to peer out into our Galaxy and beyond. NASA’s science program seeks answers to profound questions that touch us all:

    This is NASA’s science vision: using the vantage point of space to achieve with the science community and our partners a deep scientific understanding of our planet, other planets and solar system bodies, the interplanetary environment, the Sun and its effects on the solar system, and the universe beyond. In so doing, we lay the intellectual foundation for the robotic and human expeditions of the future while meeting today’s needs for scientific information to address national concerns, such as climate change and space weather. At every step we share the journey of scientific exploration with the public and partner with others to substantially improve science, technology, engineering and mathematics (STEM) education nationwide.


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  • richardmitnick 3:21 pm on September 19, 2014 Permalink | Reply
    Tags: , Astronomy, , ,   

    FromSpace.com: “The Physics of the Death Star” 

    space-dot-com logo


    September 18, 2014
    Ethan Siegel [Starts With a Bang]

    How to destroy an Alderaan-sized planet.

    “What’s that star?
    It’s the Death Star.
    What does it do?
    It does Death. It does Death, buddy. Get out of my way!” -Eddie Izzard

    It’s one of the most iconic sequences in all of film: the evil galactic empire takes the captured princess to her home planet of Alderaan, a world not so different from Earth, threatening to destroy it unless she tells them the location of the hidden rebel base. Distressed but loyal to her cause, she lies, giving them the name of a false location, which they have no way of knowing. Nevertheless, they give the order to fire, and despite her protestations, this is what happens next.

    I want you to think about this for a moment:

    A battle station the size of the Moon,
    With a mysterious, unexplained power source at its core,
    Charges up and fires a laser-like ray at an entire, Earth-sized planet,
    And completely destroys it.

    Not only does the Death Star completely destroy Alderaan from the force of its blast, it does so in a matter of seconds, and kicks off at least a substantial fraction of the world into interplanetary space with an incredible velocity.

    See for yourself!

    blow up

    From a physics point of view — and using the Earth as a proxy for Alderaan — how much energy/power would it take to cause this destruction, and what are the physical possibilities for actually making this happen?

    First off, let’s consider the planet Earth, and force binding it together.


    As Obi-Wan famously said, “It surrounds us and penetrates us; it binds the galaxy together.” But the force binding the Earth together isn’t the mysterious one from the Star Wars Universe, but simply gravitation. And the gravitational binding energy of our planet — which is the minimum amount of energy we’d have to put into it to blast it apart — is an astounding 2.24 × 10^32 Joules, or 224,000,000,000,000,000,000,000,000,000,000 Joules of energy!

    To put that in perspective, think about the entire energy output of the Sun, a “mere” 3.8 × 10^26 Watts.


    It would take a full week’s worth of the Sun’s total energy output — delivered to an entire planet in the span of a few seconds — to cause that kind of reaction!

    Remember what goes on inside an actual Sun-like star: hydrogen is burned via the process of nuclear fusion into heavier isotopes and elements, resulting in helium. Each second in the Sun, 4.3 billion kilograms of mass are converted into pure energy, which is the source of the Sun’s energy output. Let’s imagine that’s exactly what the Death Star is doing, in the most efficient way possible.


    We could simply have the Death Star fire a beam of light into the planet (e.g., laser light), requiring that it generate all that energy on board itself, and then firing it at Alderaan. This would be catastrophically inefficient, however: imagine a solid material structure — even one as big as our Moon — trying to generate, direct and expel all that energy in just a matter of a few seconds. Releasing that much energy in one direction (2.24 × 10^32 Joules), would cause a Moon-mass object to accelerate in the opposite direction to a speed of 78 km/s from rest, something that clearly didn’t happen when the Death Star was fired.


    In fact, there was no discernible recoil at all! And that’s not even considering how such intense energy would be managed, since it would heat up everything surrounding it (by simple heat diffusion) and quite clearly melt the tubes inside. But there’s another way this planetary destruction could’ve happened, predicated on one simple, indisputable fact: Princess Leia is made up of matter, and not antimatter.

    Since she’s made of matter and grew up on Alderaan, we can assume Alderaan is made of matter as well, meaning that if if the Death Star instead fired pure antimatter at Alderaan, it would only need to supply half the total energy, since the target (Alderaan itself) would provide the other half of the fuel.

    If this were the case, “only” 1.24 trillion tonnes of antimatter would suffice to provide the minimum amount of energy needed to blast that world apart. In the grand scheme of things, that isn’t so big.

    Image credit: montage by Emily Lakdawalla of the Planetary Society, via http://www.planetary.org/blogs/emily-lakdawalla/2008/1634.html, all credits as follows: NASA / JPL / Ted Stryk except: Mathilde: NASA / JHUAPL / Ted Stryk; Steins: ESA / OSIRIS team; Eros: NASA / JHUAPL; Itokawa: ISAS / JAXA / Emily Lakdawalla; Halley: Russian Academy of Sciences / Ted Stryk; Tempel 1: NASA / JPL / UMD; Wild 2: NASA / JPL

    Here are some of the larger asteroids and comet nuclei known in the Solar System; 1.24 trillion tonnes is only about the mass of the asteroid 5535 Annefrank, or one of the smaller asteroids in this montage. It’s larger than Dactyl and smaller than Ida, and denser than any of the cometary nuclei like Halley or Tempel.

    In fact, if we were to compare 5535 Annefrank with Earth — an Alderaan-sized planet — it would be about one tenth the size of what Ida looks like.

    Image credit: Matt Francis of Galileo’s Pendulum, via http://galileospendulum.org/2012/03/05/moonday-a-bite-sized-moon/

    In other words, the “antimatter” asteroid that would theoretically destroy an entire planet would barely be a single pixel in the above image!

    It’s not completely inconceivable that such a small amount of antimatter could be generated and fired at a planet! Storing that much antimatter in a Death Star-sized object might be the hard part, but here’s the thing: just like matter binds to itself through the electromagnetic force and — if you get a large amount of “stuff” together — through gravitation, antimatter behaves exactly in the same way.

    We’ve been able to create neutral antimatter and store it, successfully, for reasonably long periods of time: not mere picoseconds, microseconds or even milliseconds, but long enough that it’s only our failure to keep normal matter away from it that causes it to annihilate in short order.

    It isn’t unreasonable that an advanced technological civilization — one that’s mastered hyperdrive and faster-than-light travel — could harness, say, the energy from an uninhabited star and use it to produce neutral antimatter. The way we do it on Earth in particle accelerators is relatively simple: we collide protons with other protons at high energies, producing three protons and one antiproton as a result. That antiproton could then be merged with a positron to produce neutral antihydrogen. You might wish for rocky, crystalline structures based on elements like silicon or carbon, but under the right conditions, hydrogen can produce a crystal-like structure.

    The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons

    The quark structure of the antiproton.

    Image credit: NASA/R.J. Hall, via http://en.wikipedia.org/wiki/File:Jupiter_interior.png

    In the interiors of gas giants like Jupiter and Saturn, the incredibly thick hydrogen atmosphere extends down for tens of thousands of kilometers. Whereas the pressure at Earth’s atmosphere is around 100,000 Pascals (where a Pascal is a N/m^2), at pressures of tens of Gigapascals (or 10^10 Pascals), hydrogen can enter a metallic phase, something that should no doubt happen in the interiors of gas giant planets.

    If we could achieve this state of matter, hydrogen would actually become an electrical conductor, and is thought to be responsible for the intense magnetic field of Jupiter. All the laws of physics suggest that if this is how matter behaves, and we can do this with hydrogen, then this must also be how antimatter — and hence, antihydrogen — behaves, too.

    So all it would take, if you want to destroy an (Earth-like) planet like Alderaan, is a little over a trillion tonnes of metallic antihydrogen, and to transport it down to the planet’s surface. Once it hits the planet’s surface, it should have no trouble clearing a path down near the core, where the densities are highest.

    Image credit: Wikimedia Commons user AllenMcC, via http://www.gps.caltech.edu/uploads/File/People/dla/DLApepi81.pdf.

    And as matter-and-antimatter annihilate according to E=mc^2, the result is the release of pure energy. So long as it’s more than the gravitational binding energy of the planet — and that’s not a whole lot of antimatter, mind you — the result could be literally world-ending!

    Image credit: user Jugus of the Halo Wikia, via http://halo.wikia.com/wiki/Shield_0459. It’s the same idea.

    But if you wanted to destroy an entire planet, it would only take a small amount of antimatter to do the job: just 0.00000002% the mass of the planet in question. For comparison, a single antimatter star — and not necessarily a behemoth, but something like a relatively common A-star like Vega — would be able to undo an entire Milky Way-sized galaxy.

    When you think about it, it should make you really, really glad that matter won out over antimatter in the Universe, and that there aren’t starships, planets, stars and galaxies made out of antimatter out there. The way the Universe is destructing — slowly and gradually — is more than sufficient as-is.

    Leave your planet-destroying comments at the Starts With A Bang forum here!

    See the full article,with video, here.

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  • richardmitnick 12:00 pm on September 19, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From Chandra: “Tarantula Nebula (30 Doradus): A New View of the Tarantula Nebula” 2012 

    NASA Chandra

    April 17, 2012

    A new composite of 30 Doradus (aka, the Tarantula Nebula) contains data from Chandra (blue), Hubble (green), and Spitzer (red). 30 Doradus is one of the largest star-forming regions located close to the Milky Way. This region contains thousands of young massive stars, making it an excellent place to study how stars are born.

    NASA Hubble Telescope
    NASA/ESA Hubble

    NASA Spitzer Telescope




    Credit X-ray: NASA/CXC/PSU/L.Townsley et al.; Optical: NASA/STScI; Infrared: NASA/JPL/PSU/L.Townsley et al.
    Release Date April 17, 2012

    To celebrate its 22nd anniversary in orbit, the Hubble Space Telescope has released a dramatic new image of the star-forming region 30 Doradus, also known as the Tarantula Nebula because its glowing filaments resemble spider legs. A new image from all three of NASA’s Great Observatories – Chandra, Hubble, and Spitzer – has also been created to mark the event.

    30 Doradus is located in the neighboring galaxy called the Large Magellanic Cloud, and is one of the largest star-forming regions located close to the Milky Way . At the center of 30 Doradus, thousands of massive stars are blowing off material and producing intense radiation along with powerful winds. The Chandra X-ray Observatory detects gas that has been heated to millions of degrees by these stellar winds and also by supernova explosions. These X-rays, colored blue in this composite image, come from shock fronts — similar to sonic booms — formed by this high-energy stellar activity.

    Large Magellanic Cloud

    The Hubble data in the composite image, colored green, reveals the light from these massive stars along with different stages of star birth including embryonic stars a few thousand years old still wrapped in cocoons of dark gas. Infrared emission from Spitzer, seen in red, shows cooler gas and dust that have giant bubbles carved into them. These bubbles are sculpted by the same searing radiation and strong winds that comes from the massive stars at the center of 30 Doradus.

    See the full article here.

    Another view:

    This first light image of the TRAPPIST national telescope at La Silla shows the Tarantula Nebula, located in the Large Magellanic Cloud (LMC) — one of the galaxies closest to us. Also known as 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of bright patches that somewhat resembles the legs of a tarantula. Taking the name of one of the biggest spiders on Earth is very fitting in view of the gigantic proportions of this celestial nebula — it measures nearly 1000 light-years across! Its proximity, the favourable inclination of the LMC, and the absence of intervening dust make this nebula one of the best laboratories to help understand the formation of massive stars better. The image was made from data obtained through three filters (B, V and R) and the field of view is about 20 arcminutes across.
    8 June 2010

    ESO TRAPPIST telescope
    ESO Trappist Interior
    ESO/TRAPPIST Telescope

    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.

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  • richardmitnick 8:47 am on September 19, 2014 Permalink | Reply
    Tags: Astronomy, , , , ,   

    From NOVA: “Build Your Own Radio Telescope” 



    Thu, 24 Jul 2014
    Tim De Chant

    In 2010, on the far northern part of New Zealand’s North Island, a satellite dish was unceremoniously decommissioned and scheduled for demolition. But thanks to pluck of a few scientists, the anticipated death of the dish ended up giving radio astronomy on the island new life.

    Lewis Woodburn, who is in charge of maintenance for Auckland University of Technology’s radio telescope, and his colleagues smelled opportunity when they heard of the decommissioning and convinced Telcom New Zealand to transfer ownership of the dish over to their department. At 30 meters, Telcom New Zealand’s dish was substantially larger than the 12-meter dish already operated by the university. If they could successfully repurpose it, the new, larger dish would boost their capabilities in radio astronomy.

    It wasn’t easy, though. Technology Review details their struggles in getting the 30-meter dish operational:

    What they inherited was a far cry from a state-of-the-art radio telescope. The dish is located near a remote township in the very north of New Zealand’s North Island. Being only five kilometers from the sea, salt corrosion was significant issue, particularly given the lack of recent maintenance.

    So the team’s first task was to clean the dish service and replace rusty bolts and equipment. In particular, the motors that move the dish had become rusted and in any case were old and inefficient.

    That’s not all; Technology Review’s Emerging Technology From the arXiv blog goes into more detail. After a series of refurbishment and upgrades, the new dish is finally a bonafide radio telescope, though it still needs a bit more work to give it the capabilities astronomers at Auckland University of Technology want.

    This clever repurposing of an old telecommunications dish led to an inevitable question: Can anyone build their own radio telescope? The answer, I discovered, is yes.

    CARMA Radio Telescope
    A DIY radio telescope won’t have the power of the CARMA Radio Telescope seen here, but you’ll have a view of the sky shared by few others.

    There are a few blog posts that detail people’s experiments with refitting old satellite TV dishes for radio telescope duty, but they vary in their level of detail. Fortunately, Jeff Lashley goes into great detail in a chapter titled “Microwave Radio Telescope Projects.” (pdf) He explains how to convert a compact satellite dish into a radio telescope and how to hook it up to software developed at MIT for a similar purpose. With all the parts in place, you can do things like observe radio waves emitted by the sun or study how the ionosphere affects those same emissions.

    A home-built radio telescope may not be as sensitive as the Very Large Array, but you’ll still be able to study the stars in ways few people can.


    See the full article here.

    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

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  • richardmitnick 8:22 am on September 19, 2014 Permalink | Reply
    Tags: Astronomy, , , , Galaxy Formation,   

    From RAS: “Monster galaxies gain weight by eating smaller neighbours” 

    Royal Astronomical Society

    Royal Astronomical Society

    Friday, 19 September 2014
    Media contact

    Kirsten Gottschalk
    Media Contact, ICRAR (Perth, GMT +8:00)
    Tel: +61 8 6488 7771
    Mob: +61 438 361 876

    University of Western Australia Media Office
    Tel: +61 8 6488 7977

    Science contacts

    Dr Aaron Robotham
    ICRAR – UWA (Currently travelling in South Africa, GMT +2:00)

    Professor Simon Driver
    Principal Investigator of the GAMA project
    ICRAR – UWA (Perth, GMT +8:00)
    Tel: +61 8 6488 7747

    Massive galaxies in the Universe have stopped making their own stars and are instead snacking on nearby galaxies, according to research by Australian scientists. They publish their results in the journal Monthly Notices of the Royal Astronomical Society.

    Astronomers looked at more than 22,000 galaxies and found that while smaller galaxies are very efficient at creating stars from gas, the most massive galaxies are much less efficient at star formation, producing hardly any new stars themselves, and instead grow by eating other galaxies.

    Dr Aaron Robotham, who is based at the University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR), said smaller ‘dwarf’ galaxies were being eaten by their larger counterparts.

    “All galaxies start off small and grow by collecting gas and quite efficiently turning it into stars,” he said.

    “Then every now and then they get completely cannibalised by some much larger galaxy.”

    Some of the many thousands of merging galaxies identified within the GAMA survey. Credit: Professor Simon Driver and Dr Aaron Robotham, ICRAR. Dr Robotham, who led the research, said our own Milky Way is at a tipping point and is expected to now grow mainly by eating smaller galaxies, rather than by collecting gas.

    “The Milky Way hasn’t merged with another large galaxy for a long time but you can still see remnants of all the old galaxies we’ve cannibalised” he said.

    “We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds, in about four billion years.”

    The two-color image shows an overview of the full Small Magellanic Cloud (SMC) and was composed from two images from the Digitized Sky Survey 2. The field of view is slightly larger than 3.5 × 3.6 degrees. N66 with the open star cluster NGC 346 is the largest of the star-forming regions seen below the center of the SMC.
    Date 10 November 2005
    Source http://www.spacetelescope.org/images/html/heic0514c.html (direct link)
    Author NASA/ESA Hubble and Digitized Sky Survey 2

    Large Magellanic Cloud
    No text

    NASA Hubble Telescope
    NASA/ESA Hubble

    Sloan Digital Sky Survey Telescope
    Sloan Digital Sky Survey Telescope at Apache Point

    But Dr Robotham said the Milky Way is eventually going to get its comeuppance when it merges with the nearby Andromeda Galaxy in about five billion years.

    Andromeda Galaxy
    The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda. The image also shows Messier Objects 32 and 110, as well as NGC 206 (a bright star cloud in the Andromeda Galaxy) and the star Nu Andromedae. This image was taken using a hydrogen-alpha filter.
    18 September 2010, Adam Evans

    “Technically, Andromeda will eat us because it’s the more massive one” he said.

    Almost all of the data for the research was collected with the Anglo-Australian Telescope in New South Wales as part of the Galaxy And Mass Assembly (GAMA) survey, which is led by Professor Simon Driver at ICRAR.

    Anglo-Australian Telescope

    The GAMA survey involves more than 90 scientists and took seven years to complete. This study is one of over 60 publications to have come from the work, with another 180 currently in progress.

    Dr Robotham said as galaxies grow, they have a stronger gravitational field and can therefore more easily pull in their neighbours. He said the reason star formation slows down in really massive galaxies is thought to be because of extreme feedback events in a very bright region at the centre of a galaxy known as an active galactic nucleus.

    “The topic is much debated, but a popular mechanism is where the active galactic nucleus basically cooks the gas and prevents it from cooling down to form stars,” Dr Robotham said.

    Ultimately, gravity is expected to cause all the galaxies in bound groups and clusters to merge into a few super-giant galaxies, although we will have to wait many billions of years before that happens.

    “If you waited a really, really, really long time that would eventually happen, but by really long I mean many times the age of the Universe so far,” Dr Robotham explained.

    See the full article here.

    The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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  • richardmitnick 4:59 pm on September 18, 2014 Permalink | Reply
    Tags: Astronomy, , , , ,   

    From Hubble- Hubblecast 77: Hubble and the Bermuda Triangle of space 

    NASA Hubble Telescope


    Hubblecast 77: Hubble and the Bermuda Triangle of space

    This Hubblecast tells the story of what happens to Hubble in the mysterious region known as the South Atlantic Anomaly. When satellites pass through this area they are bombarded with swarms of intensely high energy particles. This can produce “glitches” in astronomical data, malfunctioning of on-board electronics, and has even shut down unprepared spacecraft for weeks!

    A cross-sectional view of the Van Allen radiation belts, noting the point where the South Atlantic Anomaly occurs.

    Image of the South Atlantic Anomaly (SAA) taken by the ROSAT satellite. Image reflects the SAA at approximately 560Km.

    NASA ROSAT staellite

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

    ESA50 Logo large

    AURA Icon

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  • richardmitnick 8:00 pm on September 17, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From IceCube: “An improved measurement of the atmospheric neutrino flux in IceCube “ 

    IceCube South Pole Neutrino Observatory

    17 Sep 2014
    Silvia Bravo

    Cosmic neutrinos in IceCube are the vogue these days, but atmospheric neutrinos are the popular ones if we look at the number of hits in the detector. Those neutrinos, created by the interaction of cosmic rays in the Earth’s atmosphere, are the main background in searches for astrophysical neutrinos.

    The IceCube Collaboration has submitted a paper today to the European Physical Journal C describing a new analysis scheme for the measurement of the atmospheric neutrino spectrum with the IceCube detector. The analysis was performed using data from May 2009 to May 2010, when the detector was running with a configuration of 59 of the final 86 strings.

    The spectrum was measured introducing a novel unfolding technique in the energy range from 100 GeV to 1 PeV, extending previous results of AMANDA by almost an order of magnitude. The new analysis also uses an improved selection, with results that showed a reduced atmospheric muon background contamination of 5 to 6 orders of magnitude and an 8% increase in the signal efficiency.

    The unfolded atmospheric neutrino spectrum agrees with both previous experimental results and the current theoretical models. The new method reduces the impact of the systematic uncertainties on the measured flux, but at high energies they are still too large to allow for conclusive results about a prompt and/or an astrophysical component of the overall flux.

    Comparison of the unfolding result obtained using IceCube in the 59-string configuration to previous experiments. Theoretical models are shown for comparison. Image: IceCube Collaboration.

    The analysis scheme presented in this paper introduces a machine learning algorithm for the final event selection that uses 25 event variables to distinguish between atmospheric muon tracks and tracks produced by neutrino-induced muons.

    “IceCube is a great detector for measuring atmospheric
    muon neutrinos. Those are, in fact, the vast majority of the neutrinos we detect. And by using tools and algorithms from data mining we can detect even more,” explains Tim Ruhe, a researcher at TU Dortmund University, in Germany.

    For every neutrino detected by IceCube, about a million atmospheric muons are observed. A common way to look for neutrinos in this huge muon background consists of selecting only upgoing muon tracks, since muons created by the interaction of cosmic rays with the atmosphere will be absorbed by the Earth when approaching IceCube from below. Thus, if the event reconstruction and selection were perfect, the remaining muon tracks would have been created by the interaction of a neutrino with the ice in or around the IceCube detector.

    However, previous to this analysis, the muon background rejection in IceCube was only 99.9% efficient because about 1,000 originally downgoing muons per every neutrino seen by IceCube were falsely reconstructed as upgoing tracks. With the new selection algorithm, IceCube researchers were able to reject 99.9999% of the incoming background events.

    + Info “Development of a General Analysis and Unfolding Scheme and its Application to Measure the Energy Spectrum of Atmospheric Neutrinos with IceCube,” IceCube Collaboration: M.G. Aartsen et al. Submitted to The European Physical Journal C, arXiv.org:1409.4535

    See the full article here.

    ICECUBE neutrino detector

    IceCube is a particle detector at the South Pole that records the interactions of a nearly massless sub-atomic particle called the neutrino. IceCube searches for neutrinos from the most violent astrophysical sources: events like exploding stars, gamma ray bursts, and cataclysmic phenomena involving black holes and neutron stars. The IceCube telescope is a powerful tool to search for dark matter, and could reveal the new physical processes associated with the enigmatic origin of the highest energy particles in nature. In addition, exploring the background of neutrinos produced in the atmosphere, IceCube studies the neutrinos themselves; their energies far exceed those produced by accelerator beams. IceCube is the world’s largest neutrino detector, encompassing a cubic kilometer of ice.

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  • richardmitnick 2:07 pm on September 17, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From NASA/Chandra: “NASA’s Chandra X-ray Observatory Finds Planet That Makes Star Act Deceptively Old” 

    NASA Chandra

    September 16, 2014
    Media contacts:
    Felicia Chou
    Headquarters, Washington

    Janet Anderson
    Marshall Space Flight Center

    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.

    A giant planet appears to be weakening the magnetic field of the star it closely orbits. The planet, called WASP 18b, is over ten times Jupiter’s mass but is so close to its star that it completes an orbit in less than a day. The extreme tidal forces by this “hot Jupiter” are apparently changing the internal structure of the star. Chandra data show the star is acting much older than the age astronomers estimate it to be.

    A planet may be causing the star it orbits to act much older than it actually is, according to new data from NASA’s Chandra X-ray Observatory. This discovery shows how a massive planet can affect the behavior of its parent star.

    The star, WASP 18, and its planet, WASP-18b, are located about 330 light-years from Earth. WASP-18b has a mass about 10 times that of Jupiter and completes one orbit around its star in less than 23 hours, placing WASP-18b in the “hot Jupiter” category of exoplanets, or planets outside our solar system.

    Credit X-ray: NASA/CXC/SAO/I.Pillitteri et al; Optical: DSS; Illustration: NASA/CXC/M.Weiss
    Release Date September 16, 2014

    WASP-18b is the first known example of an orbiting planet that has apparently caused its star, which is roughly the mass of our sun, to display traits of an older star.

    “WASP-18b is an extreme exoplanet,” said Ignazio Pillitteri of the Istituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Palermo in Italy, who led the study. “It is one of the most massive hot Jupiters known and one of the closest to its host star, and these characteristics lead to unexpected behavior. This planet is causing its host star to act old before its time.”

    Pillitteri’s team determined – WASP-18 is between 500 million and 2 billion years old, based on theoretical models and other data. While this may sound old, it is considered young by astronomical standards. By comparison, our sun is about 5 billion years old and thought to be about halfway through its lifetime.

    Younger stars tend to be more active, exhibiting stronger magnetic fields, larger flares, and more intense X-ray emission than their older counterparts. Magnetic activity, flaring, and X-ray emission are linked to the star’s rotation, which generally declines with age. However, when astronomers took a long look with Chandra at WASP-18 they didn’t detect any X-rays. Using established relations between the magnetic activity and X-ray emission of stars, as well as its actual age, researchers determined WASP-18 is about 100 times less active than it should be.

    “We think the planet is aging the star by wreaking havoc on its innards,” said co-author Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

    The researchers argue that tidal forces created by the gravitational pull of the massive planet – similar to those the moon has on Earth’s tides, but on a much larger scale – may have disrupted the magnetic field of the star.

    The strength of the magnetic field depends on the amount of convection in the star, or how intensely hot gas stirs the interior of the star.

    “The planet’s gravity may cause motions of gas in the interior of the star that weaken the convection,” said co-author Salvatore Sciortino also of INAF-Osservatorio Astronomico di Palermo in Italy. “This has a domino effect that results in the magnetic field becoming weaker and the star to age prematurely.”

    WASP-18 is particularly susceptible to this effect because its convection zone is narrower than most stars. This makes it more vulnerable to the impact of tidal forces that tug at it.

    The effect of tidal forces from the planet may also explain an unusually high amount of lithium found in earlier optical studies of WASP-18. Lithium is usually abundant in younger stars, but over time convection carries lithium to the hot inner regions of a star, where it is destroyed by nuclear reactions. If there is less convection, the lithium does not circulate into the interior of the star as much, allowing more lithium to survive.

    These results were published in the July issue of Astronomy and Astrophysics and are available online.

    See the full article here.

    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.

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  • richardmitnick 1:43 pm on September 17, 2014 Permalink | Reply
    Tags: Astronomy, , , ,   

    From NASA: “Pulse of a Dead Star Powers Intense Gamma Rays” 



    September 16, 2014
    Whitney Clavin 818-354-4673
    Jet Propulsion Laboratory, Pasadena, California

    Our Milky Way galaxy is littered with the still-sizzling remains of exploded stars.

    The blue dot in this image marks the spot of an energetic pulsar — the magnetic, spinning core of star that blew up in a supernova explosion. NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, discovered the pulsar by identifying its telltale pulse — a rotating beam of X-rays, that like a cosmic lighthouse, intersects Earth every 0.2 seconds.

    The pulsar, called PSR J1640-4631, lies in our inner Milky Way galaxy about 42,000 light-years away. It was originally identified by as an intense source of gamma rays by the High Energy Stereoscopic System (H.E.S.S.) in Namibia. NuSTAR helped pin down the source of the gamma rays to a pulsar.
    HESS Cherenko Array
    H.E.S.S. Array
    The other pink dots in this picture show low-energy X-rays detected by NASA’s Chandra X-ray Observatory.
    NASA Chandra Telescope
    In this image, NuSTAR data is blue and shows high-energy X-rays with 3 to 79 kiloelectron volts; Chandra data is pink and shows X-rays with 0.5 to 10 kiloeletron volts.
    The background image shows infrared light and was captured by NASA’s Spitzer Space Telescope.

    NASA Spitzer Telescope
    NASA Spitzer

    Image credit: NASA/JPL-Caltech/SAO

    When the most massive stars explode as supernovas, they don’t fade into the night, but sometimes glow ferociously with high-energy gamma rays. What powers these energetic stellar remains?

    NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, is helping to untangle the mystery. The observatory’s high-energy X-ray eyes were able to peer into a particular site of powerful gamma rays and confirm the source: A spinning, dead star called a pulsar. Pulsars are one of several types of stellar remnants that are left over when stars blow up in supernova explosions.

    This is not the first time pulsars have been discovered to be the culprits behind intense gamma rays, but NuSTAR has helped in a case that was tougher to crack due to the distance of the object in question. NuSTAR joins NASA’s Chandra X-ray Observatory and Fermi Gamma-ray Space Telescope, and the High Energy Stereoscopic System (H.E.S.S.) in Namibia, each with its own unique strengths, to better understand the evolution of these not-so-peaceful dead stars.

    NASA Fermi Telescope

    “The energy from this corpse of a star is enough to power the gamma-ray luminosity we are seeing,” said Eric Gotthelf of Columbia University, New York. Gotthelf explained that while pulsars are often behind these gamma rays in our galaxy, other sources can be as well, including the outer shells of the supernova remnants, X-ray binary stars and star-formation regions. Gotthelf is lead author of a new paper describing the findings in the Astrophysical Journal.

    In recent years, the Max-Planck Institute for Astronomy’s H.E.S.S. experiment has identified more than 80 incredibly powerful sites of gamma rays, called high-energy gamma-ray sources, in our Milky Way. Most of these have been associated with prior supernova explosions, but for many, the primary source of observed gamma rays remains unknown.

    The gamma-ray source pinpointed in this new study, caled HESS J1640-465, is one of the most luminous discovered so far. It was already known to be linked with a supernova remnant, but the source of its power was unclear. While data from Chandra and the European Space Agency’s XMM-Newton telescopes hinted that the power source was a pulsar, intervening clouds of gas blocked the view, making it difficult to see.

    ESA XMM Newton

    NuSTAR complements Chandra and XMM-Newton in its capability to detect higher-energy range of X-rays that can, in fact, penetrate through this intervening gas. In addition, the NuSTAR telescope can measure rapid X-ray pulsations with fine precision. In this particular case, NuSTAR was able to capture high-energy X-rays coming at regular fast-paced pulses from HESS J1640-465. These data led to the discovery of PSR J1640-4631, a pulsar spinning five times per second — and the ultimate power source of both the high-energy X-rays and gamma rays.

    How does the pulsar produce the high-energy rays? The pulsar’s strong magnetic fields generate powerful electric fields that accelerate charged particles near the surface to incredible speeds approaching that of light. The fast-moving particles then interact with the magnetic fields to produce the powerful beams of high-energy gamma rays and X-rays.

    “The discovery of a pulsar engine powering HESS J1640-465 allows astronomers to test models for the underlying physics that result in the extraordinary energies generated by these rare gamma-rays sources,” said Gotthelf.

    “Perhaps other luminous gamma-ray sources harbor pulsars that we can’t detect,” said Victoria Kaspi of McGill University, Montreal, Canada, a co-author on the study. “With NuSTAR, we may be able to find more hidden pulsars.”

    The new data also allowed astronomers to measure the rate at which the pulsar slows, or spins down (about 30 microseconds per year), as well as how this spin-down rate varies over time. The answers will help researchers understand how these spinning magnets — the cores of dead stars — can be the source of such extreme radiation in our galaxy.

    See the full article here.

    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 Greenhouse Gases Observing Satellite.
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