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  • richardmitnick 4:25 am on September 2, 2014 Permalink | Reply
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    From ESO: “Unravelling the Mystery of Massive Star Birth ” 2010 


    European Southern Observatory

    14 July 2010
    Contacts
    Stefan Kraus
    University of Michigan
    USA
    Tel: +1 734 615 7374
    Email: stefankr@umich.edu

    Richard Hook
    ESO
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Email: rhook@eso.org

    Henri Boffin
    ESO, La Silla Paranal and E-ELT Press Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6222
    Cell: +49 174 515 43 24
    Email: hboffin@eso.org

    All Stars are Born the Same Way

    Astronomers have obtained the first image of a dusty disc closely encircling a massive baby star, providing direct evidence that massive stars form in the same way as their smaller brethren. This discovery, made thanks to a combination of ESO’s telescopes, is described in an article in this week’s issue of Nature.

    star

    “Our observations show a disc surrounding an embryonic young, massive star, which is now fully formed,” says Stefan Kraus, who led the study. “One can say that the baby is about to hatch!”

    The team of astronomers looked at an object known by the cryptic name of IRAS 13481-6124. About twenty times the mass of our Sun and five times its radius, the young central star, which is still surrounded by its pre-natal cocoon, is located in the constellation of Centaurus, about 10 000 light-years away.

    From archival images obtained by the NASA Spitzer Space Telescope as well as from observations done with the APEX 12-metre submillimetre telescope, astronomers discovered the presence of a jet.

    NASA Spitzer Telescope
    NASA/Spitzer

    ESO APEX
    ESO/APEX

    “Such jets are commonly observed around young low-mass stars and generally indicate the presence of a disc,” says Kraus.

    Circumstellar discs are an essential ingredient in the formation process of low-mass stars such as our Sun. However, it is not known whether such discs are also present during the formation of stars more massive than about ten solar masses, where the strong light emitted might prevent mass falling onto the star. For instance, it has been proposed that massive stars might form when smaller stars merge.

    In order to discover and understand the properties of this disc, astronomers employed ESO’s Very Large Telescope Interferometer (VLTI). By combining light from three of the VLTI’s 1.8-metre Auxiliary Telescopes with the AMBER instrument, this facility allows astronomers to see details equivalent to those a telescope with a mirror of 85 metres in diameter would see. The resulting resolution is about 2.4 milliarcseconds, which is equivalent to picking out the head of a screw on the International Space Station, or more than ten times the resolution possible with current visible-light telescopes in space.

    ESO VLT Interferometer
    ESO VLT Interior
    ESO VLT

    With this unique capability, complemented by observations done with another of ESO’s telescopes, the 3.58-metre New Technology Telescope at La Silla, Kraus and colleagues were able to detect a disc around IRAS 13481-6124.

    ESO NTT
    ESO NTT Interior
    ESO/NTT

    ESO LaSilla Long View
    ESO/LaSilla

    “This is the first time we could image the inner regions of the disc around a massive young star”, says Kraus. “Our observations show that formation works the same for all stars, regardless of mass.”

    The astronomers conclude that the system is about 60 000 years old, and that the star has reached its final mass. Because of the intense light of the star — 30 000 times more luminous than our Sun — the disc will soon start to evaporate. The flared disc extends to about 130 times the Earth–Sun distance — or 130 astronomical units (AU) — and has a mass similar to that of the star, roughly twenty times the Sun. In addition, the inner parts of the disc are shown to be devoid of dust.

    “Further observations with the Atacama Large Millimeter/submillimeter Array (ALMA), currently being constructed in Chile, could provide much information on these inner parts, and allow us to better understand how baby massive stars became heavy,” concludes Kraus.

    ALMA Array
    ALMA

    More information

    This research was presented in a paper to appear in this week issue of Nature (A hot compact dust disk around a massive young stellar object, by S. Kraus et al.).

    The team is composed of Stefan Kraus (University of Michigan, USA), Karl-Heinz Hofmann, Karl M. Menten, Dieter Schertl, Gerd Weigelt, Friedrich Wyrowski, and Anthony Meilland (Max-Planck-Institut für Radioastronomie, Bonn, Germany),Karine Perraut (Laboratoire d’Astrophysique de Grenoble, France), Romain Petrov and Sylvie Robbe-Dubois (Université de Nice Sophia-Antipolis/CNRS/Observatoire de la Côte d’Azur, France), Peter Schilke (Universität zu Köln, Germany), and Leonardo Testi (ESO).

    See the full article here.

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    ESO, European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.

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  • richardmitnick 7:42 pm on September 1, 2014 Permalink | Reply
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    Seth Shostak of SETI Institute at his Eloquent Best. 


    SETI Institute

    Seth Shostak. ’nuff said.

    SETI Institute – 189 Bernardo Ave., Suite 100
    Mountain View, CA 94043
    Phone 650.961.6633 – Fax 650-961-7099
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  • richardmitnick 9:24 am on September 1, 2014 Permalink | Reply
    Tags: , , , , , Magnetar   

    From ESA: “Magnetar discovered close to supernova remnant Kesteven 79″ 

    ESASpaceForEuropeBanner
    European Space Agency

    01/09/2014
    Massive stars end their life with a bang, exploding as supernovas and releasing massive amounts of energy and matter. What remains of the star is a small and extremely dense remnant: a neutron star or a black hole.

    bh
    ESA/XMM-Newton/ Ping Zhou, Nanjing University, China

    Neutron stars come in several flavours, depending on properties such as their ages, the strength of the magnetic field concealed beneath their surface, or the presence of other stars nearby. Some of the energetic processes taking place around neutron stars can be explored with X-ray telescopes, like ESA’s XMM-Newton.

    ESA XMM Newton
    ESA/XMM-Newton

    This image depicts two very different neutron stars that were observed in the same patch of the sky with XMM-Newton. The green and pink bubble dominating the image is Kesteven 79, the remnant of a supernova explosion located about 23,000 light-years away from us.

    From the properties of the hot gas in Kesteven 79 and from its size, astronomers estimate that it is between 5000 and 7000 years old. Taking account of the time needed for light to travel to Earth, this means that the supernova that created it must have exploded almost 30,000 years ago. The explosion left behind a a young neutron star with a weak magnetic field, which can be seen as the blue spot at the centre of Kesteven 79.

    Beneath it, a blue splotch indicates an entirely different beast: a neutron star boasting an extremely strong magnetic field, known as a magnetar. Astronomers discovered this magnetar, named 3XMM J185246.6+003317, in 2013 by looking at images that had been taken in 2008 and 2009. After the discovery, they looked at previous images of the same patch of the sky, taken before 2008, but did not find any trace of the magnetar. This suggests that the detection corresponded to an outburst of X-rays released by the magnetar, likely caused by a dramatic change in the structure of its magnetic field.

    While the neutron star in the supernova remnant is relatively young, the magnetar is likely a million years old; the age difference means that it is very unlikely that the magnetar arose from the explosion that created Kesteven 79, but must have formed much earlier.

    This false-colour image is a composite of 15 observations performed between 2004 and 2009 with the EPIC MOS camera on board XMM-Newton. The image combines data collected at energies from 0.3 to 1.2 keV (shown in red), 1.2 to 2 keV (shown in green) and 2 to 7 keV (shown in blue).

    epic mos

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 8:50 am on September 1, 2014 Permalink | Reply
    Tags: , , Biota, , RNA   

    From Astrobio: “DNA May Have Had Humble Beginnings As Nutrient Carrier” 

    Astrobiology Magazine

    Astrobiology Magazine

    Sep 1, 2014
    Adam Hadhazy

    New research intriguingly suggests that DNA, the genetic information carrier for humans and other complex life, might have had a rather humbler origin. In some microbes, a study shows, DNA pulls double duty as a storage site for phosphate. This all-important biomolecule contains phosphorus, a sometimes hard-to-get nutrient.

    dna

    Maintaining an in-house source of phosphate is a newfound tactic for enabling microorganisms to eke out a living in harsh environments, according to a new study published in the open-access, peer reviewed scientific journal PLOS ONE. The finding bodes well for life finding a way, as it were, in extreme conditions on worlds less hospitable than Earth.

    The results also support a second insight: DNA might have come onto the biological scene merely as a means of keeping phosphate handy. Only later on in evolutionary history did the mighty molecule perhaps take on the more advanced role of genetic carrier.

    “DNA might have initially evolved for the purpose of storing phosphate, and the various genetic benefits evolved later,” said Joerg Soppa, senior author of the paper and a molecular biologist at Goethe University in Frankfurt, Germany.

    Unraveling life’s origins

    Scientists continue to investigate the development of self-replicating, intricate sets of chemistry — in other words, life — from the chemical compounds thought available on early Earth. Out of this mixture of prebiotic chemicals, two nucleic acids — RNA and DNA — emerged as champions.

    early
    Early Earth, in an artist’s impression, where somehow complex, self-replicating chemistry (in other words, life) emerged. Credit: Peter Sawyer / Smithsonian Institution

    Today, these two types of biomolecules serve as the genetic information carriers for all Earthly biota. RNA on its own suffices for the business of life for simpler creatures, such as some viruses. Complex life, like humans, however, relies on DNA as its genetic carrier.

    Astrobiologists want to understand the origin of DNA and its genetic cousin, RNA, because figuring out how life got started here on Earth is key for gauging if it might ever develop on alien planets.

    Many researchers think RNA must have preceded DNA as the genetic molecule of choice. RNA is more versatile, acting as both genetic code and a catalyst for chemical reactions. Explicating the rise of DNA as a genetic material directly from RNA, however, is tricky. Compared to RNA, DNA needs significantly more supporting players for it to work well in a biological setting.

    “The switch from RNA to DNA is not easy because many additional enzymes are required for DNA genomes,” said Soppa.

    This unclear transition from RNA to DNA opens the door for a precursor to DNA possibly having a more mundane job. The new study offers an attractive explanation: that DNA was a fancy way to store nutrients in cells.

    Phosphate depot?

    DNA is chock-full of phosphate. Cells depend on phosphate to form not only DNA and RNA, but also related genetic machinery, such as the ribosome. Phosphate, furthermore, is a must for building the molecule ATP, life’s energy carrier, as well as fatty membrane molecules, certain phospho-proteins and phospho-sugars, and more.

    ds
    The shores of the Dead Sea, which borders Jordan, Palestine and Israel. As the lowest and saltiest lake in the world, it is home to some extreme creatures. Image Credit: Aaron L. Gronstal

    “Phosphate is important for an immense set of biomolecules,” said Soppa.

    Unfortunately for some microbes, ample phosphate is not always available. For example, in salty, nutrient-poor habitats, such as the Dead Sea in the Middle East, an organism called Haloferax volcanii must regularly “eat” ambient DNA to obtain phosphate (plus some other nutritional goodies, such as nitrogen).

    Notably, H. volcanii can still survive and reproduce when phosphorus, the element needed to make phosphate, is lacking. Somehow, then, the microbe must turn to an inner source of phosphate, for otherwise it should cease to grow.

    In their study, Soppa and colleagues from Germany, the United States and Israel sought out this source. The nature of H. volcanii provided some clues. The organism is classified as archaea, one of the three domains of life, in addition to bacteria and eukarya, the latter encompassing all multicellular organisms, from fungi to fruit flies. Many archaea and bacteria — collectively, “prokaryotes”— have just one, circular chromosome. Eukaryotes, like us, on the other hand, can have any number of the chunky pieces of DNA, RNA and proteins. (Humans have 23 pairs of different chromosomes, for the record.) H. volcanii is unusual. It has 20 copies of the same chromosome when it’s growing happily under favorable conditions, and 10 when nutrients are exhausted and it reaches a stationary phase.

    Strength in numbers

    Lots of chromosome copies are good to have in a pinch. So-called polyploidal organisms like H. volcanii use their copious chromosomes to tough it out through bad situations, such as high radiation exposure or total dry-outs, called desiccation. Either scenario causes the strands in chromosomal DNA to break. For single-chromosome species, only a few breaks lead to death because it is impossible to repair a chromosome scattered into fragments.

    But if there are multiple copies of the cracked chromosomes, fragments can fortuitously line up. Rather like how a jigsaw puzzle is easier to put together if there are numerous duplicates of each necessary piece, the chromosome shards can sync up and restore a functional chromosome.

    hv
    H. Volcanii grown in culture. Credit: Yejineun/Wikipedia

    “In polyploid species, the fragments generated from different copies of the chromosome overlap, and it is possible to regenerate an intact chromosome from overlapping fragments,” said Soppa.

    Desperate times, desperate measures

    To investigate if H. volcanii‘s extra chromosomes might help the archaeon survive low phosphate conditions, Soppa and colleagues starved the organism in the lab of the critical substance. The microbe continued to reproduce by splitting one cell apart into two. Interestingly, chromosome counts diminished in the “parent” and the “daughter” cells.

    “From quantifying the number of chromosomes prior to and after growth in the absence of phosphate, we have found that about 30 percent of the chromosomes are ‘missing’ afterwards,” said Soppa.

    The numbers for another potential in-house source of phosphate, H. volcanii‘s ribosomes, however, remained steady. The most likely explanation, then, of the microorganism’s hardiness when facing a phosphate nutrient shortage: H. volcanii simply cannibalizes some of its own chromosomes.

    As further verification, Soppa and colleagues tested the survival skills of H. volcanii cells that contained varying numbers of chromosome copies. Those archaea with just two copies of their chromosome turned out to be more than five times as sensitive to desiccation as those H. volcanii with a hefty complement of 20 chromosomes.

    Life, undaunted

    This newly described benefit of polyploidy in H. volcanii is a fresh demonstration of how life can make do in severe environments. So-called extremophiles have been discovered in recent decades thriving in strongly acidic hot springs, within liquid asphalt, and in other eyebrow-raising niches. Salt-tolerant bacteria and archaea, like H. volcanii, have been found to survive in deserts, simulated Mars conditions, and even the rigors of a space flight. We should not be surprised, perhaps, if life has managed to take hold on formidable worlds.

    rw
    Extremophile microbes have been found that can survive in the polluted Rio Tinto River in Spain. Mining in the river’s vicinity has led to its waters having a high heavy metal content and very low pH, though the bacteria themselves, through their metabolism, also likely contribute to the intense acidity. Image credit: Leslie Mullen

    “The understanding of how harsh the conditions can be that can be survived by some archaea and bacteria helps us to be more optimistic that life could have evolved at very rough and unsuitable places on early Earth or on other planets,” said Soppa.

    The new role ascribed to DNA, as phosphate storage, might help to explain how a completely RNA-dominated primordial era began sharing genetic duties with DNA. Life did not leap from RNA to DNA. Rather, DNA, slowly but surely, learned new tricks.

    “The hypothesis that DNA might have evolved as a storage polymer and became genetic material later, makes the step from RNA to DNA as genetic material easier, because it then would be a two-step and not a one-step process,” said Soppa. “DNA would have been around, and during long time spans additional roles could have been evolved.”

    See the full article here.
    Astrobiology Magazine is a NASA-sponsored online popular science magazine. Our stories profile the latest and most exciting news across the wide and interdisciplinary field of astrobiology — the study of life in the universe. In addition to original content, Astrobiology Magazine also runs content from non-NASA sources in order to provide our readers with a broad knowledge of developments in astrobiology, and from institutions both nationally and internationally. Publication of press-releases or other out-sourced content does not signify endorsement or affiliation of any kind.
    Established in the year 2000, Astrobiology Magazine now has a vast archive of stories covering a broad array of topics.

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  • richardmitnick 8:29 am on September 1, 2014 Permalink | Reply
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    From Hubble: “Spiral in Serpens” 

    NASA Hubble Telescope

    Hubble

    September 1, 2014

    This new NASA/ESA Hubble Space Telescope image shows a beautiful spiral galaxy known as PGC 54493, located in the constellation of Serpens (The Serpent). This galaxy is part of a galaxy cluster that has been studied by astronomers exploring an intriguing phenomenon known as weak gravitational lensing.

    pbc
    Credit: NASA/ESA Hubble Judy Schmidt
    Hubble Space Telescope ACS

    NASA Hubble ACS
    ACS

    This effect, caused by the uneven distribution of matter (including dark matter) throughout the Universe, has been explored via surveys such as the Hubble Medium Deep Survey. Dark matter is one of the great mysteries in cosmology. It behaves very differently from ordinary matter as it does not emit or absorb light or other forms of electromagnetic energy — hence the term “dark”.

    Even though we cannot observe dark matter directly, we know it exists. One prominent piece of evidence for the existence of this mysterious matter is known as the “galaxy rotation problem“. Galaxies rotate at such speeds and in such a way that ordinary matter alone — the stuff we see — would not be able to hold them together. The amount of mass that is “missing” visibly is dark matter, which is thought to make up some 27% of the total contents of the Universe, with dark energy and normal matter making up the rest. PGC 55493 has been studied in connection with an effect known as cosmic shearing. This is a weak gravitational lensing effect that creates tiny distortions in images of distant galaxies.

    A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Judy Schmidt.

    See the full article here.

    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.

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  • richardmitnick 7:42 pm on August 31, 2014 Permalink | Reply
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    From SPACE.com: “Milky Way Galaxy: Facts About Our Galactic Home” 2013 

    space-dot-com logo

    SPACE.com

    February 22, 2013
    Nola Taylor Redd

    The Milky Way galaxy is most significant to humans because it is home sweet home. But when it comes down to it, our galaxy is a typical barred spiral, much like billions of other galaxies in the universe. Let’s take a look at the Milky Way.

    mw

    Location, location, location

    A glance up at the night sky reveals a broad swath of light. Described by the ancients as a river, as milk, and as a path, among other things, the band has been visible in the heavens since Earth first formed. In reality, this intriguing line of light is the center of our galaxy, as seen from one of its outer arms.

    The Milky Way is a barred spiral galaxy, about 100,000 light-years across. If you could look down on it from the top, you would see a central bulge surrounded by four large spiral arms that wrap around it. Spiral galaxies make up about two-third of the galaxies in the universe.

    ngc6744
    A Milky Way look-alike, NGC 6744
    This picture of the nearby galaxy NGC 6744, a Milky Way look-alike, was taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla.
    Credit: ESO/MPG/ESO 2.2-metre telescope at La Silla

    ESO Wide Field Imager 2.2m LaSilla
    ESO WFI
    ESO 2.2 meter telescope
    ESO/ 2.2 meter telescope at LaSilla

    Unlike a regular spiral, a barred spiral contains a bar across its center region, and has two major arms. The Milky Way also contains two significant minor arms, as well as two smaller spurs. One of the spurs, known as the Orion Arm, contains the sun and the solar system. The Orion arm is located between two major arms, Perseus and Sagittarius. [The writer is incorrect as to the second major arm. It is, in fact, Scutum-Centaurus]

    mw
    Artist’s conception of the Milky Way galaxy as seen from far Galactic North (in Coma Berenices) by NASA/JPL-Caltech/R. Hurt [2] annotated with arms (colour-coded according to Milky Way article) as well as distances from the Solar System and galactic longitude with corresponding constellation.

    bs
    Barred Spiral Galaxy NGC 1300, photographed by NASA/ESA Hubble Space Telescope

    NASA Hubble Telescope
    NASA/ESA Hubble

    The Milky Way does not sit still, but is constantly rotating. As such, the arms are moving through space. The sun and the solar system travel with them. The solar system travels at an average speed of 515,000 miles per hour (828,000 kilometers per hour). Even at this rapid speed, the solar system would take about 230 million years to travel all the way around the Milky Way.

    Curled around the center of the galaxy, the spiral arms contain a high amount of dust and gas. New stars are constantly formed within the arms. These arms are contained in what is called the disk of the galaxy. It is only about 1,000 light-years thick.

    mw map
    Milky Way map

    At the center of the galaxy is the galactic bulge. The heart of the Milky Way is crammed full of gas, dust, and stars. The bulge is the reason that you can only see a small percentage of the total stars in the galaxy. Dust and gas within it are so thick that you can’t even peer into the bulge of the Milky Way, much less see out the other side.

    mw2
    VISTA Telescope’s View of Milky Way’s Center
    This very wide-field view of the Milky Way shows the extent of the 84-million-star VISTA infrared image of the center of the galaxy (delineated by red rectangle).
    Credit: ESO/Nick Risinger (skysurvey.org)

    ESO Vista Telescope
    ESO/VISTA Telescope

    Tucked inside the very center of the galaxy is a monstrous black hole, billions of times as massive as the sun. This supermassive black hole may have started off smaller, but the ample supply of dust and gas allowed it to gorge itself and grow into a giant. The greedy glutton also consumes whatever stars it can get a grip on. Although black holes cannot be directly viewed, scientists can see their gravitational effects as they change and distort the paths of the material around it, or as they fire off jets. Most galaxies are thought to have a black hole in their heart.

    The bulge and the arms are the most obvious components of the Milky Way, but they are not the only pieces. The galaxy is surrounded by a spherical halo of hot gas, old stars and globular clusters. Although the halo stretches for hundreds of thousands of light-years, it only contains about two percent as many stars as are found within the disk.

    gc
    Globular cluster Messier 80

    Dust, gas, and stars are the most visible ingredients in the galaxy, but the Milky Way is also made up of dark matter. Scientists can’t directly detect the material, but like black holes, they can measure it based on its effect on the objects around it. As such, dark matter is estimated to make up 90 percent of the mass of the galaxy.

    Collision course

    Not only is the Milky Way spinning, it is also moving through the universe. Despite how empty space might appear in the movies, it is filled with dust and gas — and other galaxies. The massive collections of stars are constantly crashing into one another, and the Milky Way is not immune.

    In about four billion years, the Milky Way will collide with its nearest neighbor, the Andromeda Galaxy. The two are rushing towards each other at about 70 miles per second (112 km per second). When they collide, they will provide a fresh influx of material that will kick of star formation anew.

    andro
    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. Adam Evans

    The Andromeda Galaxy is obviously not the most careful of drivers. It shows signs of having already crashed into another galaxy in the past. Although it is the same age as the Milky Way, it hosts a large ring of dust in its center, and several older stars.

    The dark Coalsack is readily apparent in the middle of the image. The stars Alpha Centauri (the closest star to our solar system at 4.3-light years away) and Beta Centauri are to the left of the Coalsack, while the famous Southern Cross (Crux) is poised just above and to the right of the Coalsack. The Southern Milky Way is far more spectacular than the Milky Way that those of us situated north of the equator can ever see.

    coalsack
    Coalsack Nebula, Don Pettit, ISS Expedition 6, NASA (prepared by Adrian Pingstone in December 2003)

    Of course, the imminent collision shouldn’t be a problem for inhabitants of Earth. By the time the two galaxies ram headlong, the sun will already have ballooned into a red giant, making our planet uninhabitable.

    Milky Way facts

    *The Milky Way contains over 200 billion stars, and enough dust and gas to make billions more.
    *The solar system lies about 30,000 light-years from the galactic center, and about 20 light-years above the plane of the galaxy.
    *More than half the stars found in the Milky Way are older than the 4.5 billion year old sun.
    *The most common stars in the galaxy are red dwarfs, a cool star about a tenth the mass of the sun. Once thought unsuitable for potential life-bearing planets because such bodies would have to be too close to meet the criteria, red dwarfs are now considered potential suspects.

    As late as the 1920s, astronomers thought all of the stars in the universe were contained inside of the Milky Way. It wasn’t until Edwin Hubble discovered a special star known as a Cepheid variable, which allowed him to precisely measure distances, that astronomers realized that the fuzzy patches once classified as nebula were actually separate galaxies.

    r puppis
    RS Puppis, a Cepheid variable as imaged by Hubble

    See the full article here.

    This video is the best set of lessons on the Milky Way that one can find. Please watch, enjoy and learn.

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  • richardmitnick 10:08 am on August 31, 2014 Permalink | Reply
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    From ESO: “Possible Planetary System Photographed Around Nearby Star” 1987 A Good Piece of ESO History 


    European Southern Observatory

    5 January 1987
    Contacts
    Richard West
    ESO
    Garching, Germany
    Tel: +49 89 3200 6276
    Email: information@eso.org

    Based on observations obtained at the European Southern Observatory (ESO), astronomers at the Space Telescope Science Institute (STScI) have uncovered the strongest evidence yet for the presence of a giant planetary or protoplanetary system accompanying a nearby star [1].

    image

    Using special observational and image analysis techniques, Francesco Paresce and Christopher Burrows, of STScI and the European Space Agency (ESA), have made the first visible light images of a large disc of material closely bound to the star Beta Pictoris. The disc is at least 80.000 million kilometres across, or more than three times the diameter of our solar system.

    bp
    The red dot shows the location of Beta Pictoris.

    The observations were made at the ESO La Silla observatory in the Atacama desert in Chile. The astronomers will present their findings at the 169th meeting of the American Astronomical Society in Pasadena, California on January 5th.

    ESO LaSilla
    ESO/LaSilla

    An unusual excess of infrared radiation, indicative of circumstellar matter, was initially detected around Beta Pictoris by the Infrared Astronomy Satellite (IRAS) in 1983. Subsequent ground-based observations revealed the presence of a disc-like feature at near-infrared wavelengths.

    Caltech IRAS
    Caltech IRAS

    When Paresce and Burrows made detailed observations of the disc at several regions of the visible light spectrum, they found that the reflectivity of the disc material was neutral, or wavelength independent. This means that the colour and spectral characteristics of light reflected from the disc almost exactly matched the spectrum of light emitted from the star itself.

    This observation offers the strongest indications yet that the disc is made up of relatively large solid particles. If it were extremely fine dust, which is commonly found in interstellar space, it would scatter only the bluer wavelengths of starlight. The observational data alone cannot establish the true size of the reflecting particles but does set a lower limit of about 0.001 millimetre (1 micron). At this diametre or greater, the particles found around Beta Pictoris are at least ten times larger than material normally observed in interstellar space.

    “The observations show unequivocally that an agglomeration process is in an advanced state, where fine interstellar grains stuck together to form larger clumps”, reports Dr. Paresce. It is believed that as such a ‘snowballing’ process continues, the disc material may eventually accrete into planet-sized objects, if they have not done so already. Our solar system may have condensed or accreted out of thick dust grains which formed a circumstellar nebula that accompanied the birth of our sun, approximately 4600 million years ago.

    The presently available observational data cannot determine the composition of the particles, though they likely contain silicates, carbonaceous materials, and water ice – common elements abundant within our own solar system.

    The evidence for planetary formation is also supported by the fact that the large dust particles are arranged in a flattened disc. The disc likely formed out of an immense, protostellar nebula that contracted and collapsed into the feature seen today. Most of the nebula’s gas and dust concentrated at the centre of the disc to form the star Beta Pictoris. The remaining material now continues to orbit the star.

    At present it is not known if planets already formed within the disc or if it is still in a protoplanetary stage. “All that can be said for sure is that the disc has progressed from a ‘fine sand’ stage into at least a ‘pebble’ stage”, says Dr. Paresce.

    Beta Pictoris is a relatively young star estimated to be no older than 1000 million years, or about one fifth the age of our sun. Approximately 50 light years away, it is a socalled ‘main-sequence dwarf‘, like our sun.

    Paresce and Burrows made their observations of Beta Pictoris, which is visible as a fourth magnitude star in the southern hemisphere, with the ESO 2.2 metre telescope. Attaching a coronograph of their own design and fabrication, the researchers blocked out the brilliant image of the star, so that the faint circumstellar features could be photographed with a CCD (Charge Coupled Device) detector. To allow analysis of the disc at various wavelengths of light, a series of exposures were then taken through bandpass filters across the visible spectrum. These difficult observations were facilitated by the excellent atmospheric conditions at the ESO La Silla observatory.

    ESO 2.2 meter telescope
    2.2
    ESO/ 2.2 meter telescope

    As a control, an identical observing sequence was performed on the stars Delta Hydrus and Alpha Pictoris which are not expected to have prominent circumstellar disc features visible from Earth.

    Through special data analysis techniques developed by Paresce and Burrows, the two stellar images were corrected for known instrumental effects, precisely registered, and differences between the two images were evaluated. This was an especially challenging task since the researchers were probing the near vicinity of Beta Pictoris and had to contend with intense scattered light from the star itself. They also had to be sure that they were seeing reflected light from a true disc feature and not contamination produced by the instrument optics.

    Their resulting data yields the first true, photometrically accurate image of the Beta Pictoris disc, down to about four arcseconds from the star. Never before has such a relatively faint feature been photographed within such close proximity to such a bright star.

    The resulting images reveal a highly flattened disc which extends symmetrically outward from Beta Pictoris, into a northeast and southwest direction on the sky. The disc’s apparent angular width may indicate that it is slightly tilted to our line of sight. The disc dramatically increases in brightness toward its center, though its structure closer to Beta Pictoris is not visible due to the occulting finger which blocks out most of the light from the star.

    Astronomers are eager to find evidence of extrasolar planetary systems to learn whether our own solar system was created out of very unique conditions, or whether it is the result of common and fundamental processes that accompany stellar formation. These questions can not be satisfactorily answered until astronomers have carefully studied examples of planetary formation other than our own solar system.

    Paresce and Burrows have images of planetary or protoplanetary around other stars to analyze. They also plan to make detailed observations of Beta Pictoris with the NASA/ESA Hubble Space Telescope, which is now scheduled for launch in late 1988. With its significant increase in resolution over present ground-based instruments, the Space Telescope will have the capability to provide a far more detailed view of the disc’s structure, closer to the star. It will also have the potential for detecting the extremely faint glow of planets which may accompany the star. It is also expected that this fascinating area of astronomical research will greatly benefit from future, giant telescopes on the ground, such as the ESO 16 metre Very Large Telescope (VLT), now in the final planning stage.

    NASA Hubble Telescope
    NASA/ESA Hubble

    ESO VLT
    ESO VLT Interior
    ESO/VLT

    Notes

    [1] The text of this Press Release is published simultaneously by STScI and ESO. A B/W picture is available on request from both organisations.
    More information

    The Hubble Space Telescope is a project of international collaboration between NASA and ESA. The Space Telescope Science Institute is operated for NASA by the Association of Universities for Research in Astronomy (AURA). It is located on the Johns Hopkins University Campus in Baltimore, Maryland, U.S.A.

    See the full article here.

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    ESO, European Southern Observatory, builds and operates a suite of the world’s most advanced ground-based astronomical telescopes.

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  • richardmitnick 2:55 pm on August 30, 2014 Permalink | Reply
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    From Chandra: “Kes 75: One Weird Star Starts Acting Like Another” 2008 

    NASA Chandra

    This deep Chandra X-ray Observatory image shows the supernova remnant Kes 75, located almost 20,000 light years away. The explosion of a massive star created the supernova remnant, along with a pulsar, a rapidly spinning neutron star.

    kes75
    Credit NASA/CXC/GSFC/F.P.Gavriil et al.
    Release Date February 21, 2008

    The low energy X-rays are colored red in this image and the high energy X-rays are colored blue. The pulsar is the bright spot near the center of the image. The rapid rotation and strong magnetic field of the pulsar have generated a wind of energetic matter and antimatter particles that rush out at near the speed of light. This pulsar wind has created a large, magnetized bubble of high-energy particles called a pulsar wind nebulae, seen as the blue region surrounding the pulsar.

    The magnetic field of the pulsar in Kes 75 is thought to be more powerful than most pulsars, but less powerful than magnetars, a class of neutron star with the most powerful magnetic fields known in the Universe. Scientists are seeking to understand the relationship between these two classes of object.

    Using NASA’s Rossi X-ray Timing Explorer (RXTE), Fotis Gavriil of Goddard Space Flight Center, and colleagues discovered powerful bursts of X-rays from this pulsar that are similar to bursts previously seen from magnetars. These bursts are believed to occur when the surface of the neutron star is disrupted by sudden changes in the magnetic field. These bursts were accompanied by magnetar-like changes in the rate of spin of the pulsar. Fortuitously, Chandra observed the pulsar near the time of the bursts and it was much brighter than it had been in Chandra observations obtained six years earlier. This brightening, and changes in the X-ray spectrum of the pulsar obtained with Chandra are also consistent with behavior expected for a magnetar. The behavior of this object may, therefore, fill a gap between that of pulsars and magnetars.

    NASA RXTE
    NASA/RXTE

    Harsha Sanjeev Kumar and Samar Safi-Harb of the University of Manitoba have independently used Chandra observations to argue that the pulsar in Kes 75 is revealing itself as a magnetar.

    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 2:12 pm on August 30, 2014 Permalink | Reply  

    From Astrobiology: “What lit up the universe?” 

    Astrobiology Magazine

    Astrobiology Magazine

    [Two earlier articles referred to in this article are included with their dates in this post. Most necessary links are given at their first instance in any of the three articles.]

    Aug 30, 2014
    Source: University College of London
    Bex Caygill Tel: +44 (0)20 3108 3846

    New research shows we will soon uncover the origin of the ultraviolet light that bathes the cosmos, helping scientists understand how galaxies were built.

    The study published this month in The Astrophysical Journal Letters by UCL cosmologists Dr Andrew Pontzen and Dr Hiranya Peiris (both UCL Physics & Astronomy), together with collaborators at Princeton and Barcelona Universities, shows how forthcoming astronomical surveys will reveal what lit up the cosmos.

    lace
    A computer model shows one scenario for how light is spread through the early universe on vast scales (more than 50 million light years across). Astronomers will soon know whether or not these kinds of computer models give an accurate portrayal of light in the real cosmos.
    Credit: Andrew Pontzen/Fabio Governato

    “Which produces more light? A country’s biggest cities or its many tiny towns?” asked Dr Pontzen, lead author of the study. “Cities are brighter, but towns are far more numerous. Understanding the balance would tell you something about the organisation of the country. We’re posing a similar question about the universe: does ultraviolet light come from numerous but faint galaxies, or from a smaller number of quasars?”

    Quasars are the brightest objects in the Universe; their intense light is generated by gas as it falls towards a black hole. Galaxies can contain millions or billions of stars, but are still dim by comparison. Understanding whether the numerous small galaxies outshine the rare, bright quasars will provide insight into the way the universe built up today’s populations of stars and planets. It will also help scientists properly calibrate their measurements of dark energy, the agent thought to be accelerating the universe’s expansion and determining its far future.

    The new method proposed by the team builds on a technique already used by astronomers in which quasars act as beacons to understand space. The intense light from quasars makes them easy to spot even at extreme distances, up to 95% of the way across the observable universe. The team think that studying how this light interacts with hydrogen gas on its journey to Earth will reveal the main sources of illumination in the universe, even if those sources are not themselves quasars.

    Two types of hydrogen gas are found in the universe – a plain, neutral form and a second charged form which results from bombardment by UV light. These two forms can be distinguished by studying a particular wavelength of light called ‘Lyman-alpha’ which is only absorbed by the neutral type of hydrogen. Scientists can see where in the universe this ‘Lyman-alpha’ light has been absorbed to map the neutral hydrogen.

    Since the quasars being studied are billions of light years away, they act as a time capsule: looking at the light shows us what the universe looked like in the distant past. The resulting map will reveal where neutral hydrogen was located billions of years ago as the universe was vigorously building its galaxies.

    An even distribution of neutral hydrogen gas would suggest numerous galaxies as the source of most light, whereas a much less uniform pattern, showing a patchwork of charged and neutral hydrogen gas, would indicate that rare quasars were the primary origin of light.

    Current samples of quasars aren’t quite big enough for a robust analysis of the differences between the two scenarios; however, a number of surveys currently being planned should help scientists find the answer.

    Chief among these is the DESI (Dark Energy Spectroscopic Instrument) survey which will include detailed measurements of about a million distant quasars. Although these measurements are designed to reveal how the expansion of the universe is accelerating due to dark energy, the new research shows that results from DESI will also determine whether the intervening gas is uniformly illuminated. In turn, the measurement of patchiness will reveal whether light in our universe is generated by ‘a few cities’ (quasars) or by ‘many small towns’ (galaxies).

    DECam
    DECam

    Co-author Dr Hiranya Peiris, said: “It’s amazing how little is known about the objects that bathed the universe in ultraviolet radiation while galaxies assembled into their present form. This technique gives us a novel handle on the intergalactic environment during this critical time in the universe’s history.”

    Dr Pontzen, said: “It’s good news all round. DESI is going to give us invaluable information about what was going on in early galaxies, objects that are so faint and distant we would never see them individually. And once that’s understood in the data, the team can take account of it and still get accurate measurements of how the universe is expanding, telling us about dark energy. It illustrates how these big, ambitious projects are going to deliver astonishingly rich maps to explore. We’re now working to understand what other unexpected bonuses might be pulled out from the data.”

    See this article here.

    Milky Way May Have Formed ‘Inside-Out’

    Jan 20, 2014

    Gaia provides new insight into Galactic evolution

    ESA Gaia Camera
    ESA/Gaia Camera
    ESA Gaia satellite
    ESA/Gaia spacecraft

    A breakthrough using data from the [ESA]/Gaia-ESO project has provided evidence backing up theoretically predicted divisions in the chemical composition of the stars that make up the Milky Way’s disc – the vast collection of giant gas clouds and billions of stars that give our Galaxy its ‘flying saucer’ shape.

    By tracking the fast-produced elements, specifically magnesium in this study, astronomers can determine how rapidly different parts of the Milky Way were formed. The research suggests that stars in the inner regions of the Galactic disc were the first to form, supporting ideas that our Galaxy grew from the inside-out.

    Using data from the 8-m VLT in Chile, one of the world’s largest telescopes, an international team of astronomers took detailed observations of stars with a wide range of ages and locations in the Galactic disc to accurately determine their ‘metallicity’: the amount of chemical elements in a star other than hydrogen and helium, the two elements most stars are made from.

    ESO VLT Interferometer
    ESO VLT Interior
    ESO/VLT

    Immediately after the Big Bang, the Universe consisted almost entirely of hydrogen and helium, with levels of “contaminant metals” growing over time. Consequently, older stars have fewer elements in their make-up – so have lower metallicity.

    “The different chemical elements of which stars – and we – are made are created at different rates – some in massive stars which live fast and die young, and others in sun-like stars with more sedate multi-billion-year lifetimes,” said Professor Gerry Gilmore, lead investigator on the Gaia-ESO Project.

    big
    This is a figure illustrating latest Gaia-ESO research findings. (Click image for larger size) Credit: Amanda Smith/Institute of Astronomy

    Massive stars, which have short lives and die as ‘core-collapse supernovae’, produce huge amounts of magnesium during their explosive death throes. This catastrophic event can form a neutron star or a black hole, and even trigger the formation of new stars.

    The team have shown that older, ‘metal-poor’ stars inside the Solar Circle – the orbit of our Sun around the centre of the Milky Way, which takes roughly 250 million years to complete – are far more likely to have high levels of magnesium. The higher level of the element inside the Solar Circle suggests this area contained more stars that “lived fast and die young” in the past.

    The stars that lie in the outer regions of the Galactic disc – outside the Solar Circle – are predominantly younger, both ‘metal-rich’ and ‘metal-poor’, and have surprisingly low magnesium levels compared to their metallicity.

    This discovery signifies important differences in stellar evolution across the Milky Way disc, with very efficient and short star formation timescales occurring inside the Solar Circle; whereas, outside the Sun’s orbit, star formation took much longer.

    “We have been able to shed new light on the timescale of chemical enrichment across the Milky Way disc, showing that outer regions of the disc take a much longer time to form,” said Maria Bergemann from Cambridge’s Institute of Astronomy, who led the study.

    “This supports theoretical models for the formation of disc galaxies in the context of Cold Dark Matter cosmology, which predict that galaxy discs grow inside-out.”

    The findings offer new insights into the assembly history of our Galaxy, and are the part of the first wave of new observations from the Gaia-ESO survey, the ground-based extension to the Gaia space mission – launched by the European Space Agency at the end of last year – and the first large-scale survey conducted on one the world’s largest telescopes: the 8-m VLT in Paranal, Chile.

    The study is published online today through the astronomical database Astro-ph, and has been submitted to the journal Astronomy and Astrophysics.

    range
    This digitally enhanced double-exposure was taken in May 2003 over the Kofa Mountains in Arizona, USA. Dark dust, millions of stars, and bright glowing red gas highlight the plane of our Milky Way Galaxy. Photo credit: Richard Payne (Arizona Astrophotography)

    The new research also sheds further light on another much debated “double structure” in the Milky Way’s disc – the so-called ‘thin’ and ‘thick’ discs.

    “The thin disc hosts spiral arms, young stars, giant molecular clouds – all objects which are young, at least in the context of the Galaxy,” explains Aldo Serenelli from the Institute of Space Sciences (Barcelona), a co-author of the study. “But astronomers have long suspected there is another disc, which is thicker, shorter and older. This thick disc hosts many old stars that have low metallicity.”

    During the latest research, the team found that:

    • Stars in the young, ‘thin’ disc aged between 0 – 8 billion years all have a similar degree of metallicity, regardless of age in that range, with many of them considered ‘metal-rich’.
    • There is a “steep decline” in metallicity for stars aged over 9 billion years, typical of the ‘thick’ disc, with no detectable ‘metal-rich’ stars found at all over this age.
    • But stars of different ages and metallicity can be found in both discs.

    “From what we now know, the Galaxy is not an ‘either-or’ system. You can find stars of different ages and metal content everywhere!” said Bergemann. “There is no clear separation between the thin and thick disc. The proportion of stars with different properties is not the same in both discs – that’s how we know these two discs probably exist – but they could have very different origins.”

    Added Gilmore: “This study provides exciting new evidence that the inner parts of the Milky Way’s thick disc formed much more rapidly than did the thin disc stars, which dominate near our Solar neighbourhood.”

    In theory, say astronomers, the thick disc – first proposed by Gilmore 30 years ago – could have emerged in a variety of ways, from massive gravitational instabilities to consuming satellite galaxies in its formative years. “The Milky Way has cannibalised many small galaxies during its formation. Now, with the Gaia-ESO Survey, we can study the detailed tracers of these events, essentially dissecting the belly of the beast,” said Greg Ruchti, a researcher at Lund Observatory in Sweden, who co-leads the project.

    With upcoming releases of Gaia-ESO, an even better handle on the age-metallicity relation and the structure of the Galactic disc is expected, say the team. In a couple of years, these data will be complemented by positions and kinematics provided by the Gaia satellite and together will revolutionise the field of Galactic astronomy.

    See this article here.

    The Universe in 3D

    May 3, 2011

    The biggest 3-D map of the distant universe ever made, using light from 14,000 quasars – supermassive black holes at the centers of galaxies billions of light years away – has been constructed by scientists with the third Sloan Digital Sky Survey (SDSS-III).

    Sloan Digital Sky Survey Telescope
    SDSS Camera

    The map is the first major result from the Baryon Oscillation Spectroscopic Survey (BOSS), SDSS-III’s largest survey, whose principal investigator is David Schlegel of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). The huge new map was presented at the April meeting of the American Physical Society in Anaheim, CA, by Anže Slosar of Brookhaven National Laboratory.

    sprerad
    BOSS is extending the existing Sloan Digital Sky Survey map of the universe based on galaxies, center, into the realm of intergalactic gas in the distant universe, using the light from bright quasars (blue dots). Credit: Sloan Digital Sky Survey – See more at: http://www.astrobio.net/topic/deep-space/cosmic-evolution/the-universe-in-3d/#sthash.aQus5jw9.dpuf

    BOSS is the first attempt to use baryon acoustic oscillation (BAO) as a precision tool to measure dark energy. Baryon oscillation refers to how matter clumps in a regular way throughout the Universe, a physical manifestation of the expansion of the Universe. Until now, 3-D maps showing this oscillation have been based on the distribution of visible galaxies. BOSS is the first survey to map intergalactic hydrogen gas as well, using distant quasars whose light is produced by supermassive black holes at the centers of active galaxies.

    “Quasars are the brightest objects in the Universe, which we use as convenient backlights to illuminate the intervening hydrogen gas that fills the Universe between us and them,” Slosar says. “We can see their shadows, and the details in their shadows” – specifically, the absorption features in their spectra known as the Lyman-alpha forest – “allowing us to see how the gas is clumped along our line of sight. The amazing thing is that this allows us to see the Universe so very far away, where measuring positions of individual galaxies in large numbers is impractical.”

    “BOSS is the first attempt to use the Lyman-alpha forest to measure dark energy,” says principal investigator Schlegel. “Because the Sloan Telescope has such a wide field of view, and because these quasars are so faint, there was no one who wasn’t nervous about whether we could really bring it off.”

    By using 14,000 of the quasars collected by the Sloan Telescope at Apache Point Observatory in New Mexico during the first year of BOSS’s planned five-year run, the new map demonstrates that indeed it is possible to determine variations in the density of intergalactic hydrogen gas at cosmological distances and thus to measure the effects of dark energy at those distances.

    Slosar, who leads BOSS’s Lyman-alpha cosmology working group, says that while similar measurements have been made with individual quasars or small groups of quasars in the past, “These have given only one-dimensional information about fluctuations in density along the line of sight. Before now there has never been enough density of quasars for a 3-D view.”

    The distance scale of the new map corresponds to an early time in the history of the Universe, when the distribution of matter was nearly uniform. Any effects of dark energy detected so early would settle basic questions about its nature.

    Measuring the expansion history of the Universe

    Baryon acoustic oscillation is cosmologists’ shorthand for the periodic clustering (oscillation) of matter (baryons), which originated as pressure (acoustic) waves moving through the hot, opaque, liquid-like early universe. The pressure differences resulted in differences in density and left their signature as small variations in the temperature of the cosmic microwave background. Later – because the denser regions formed by the pressure waves seeded galaxy formation and the accumulation of other matter – the original acoustic waves were echoed in the net-like filaments and voids of the clustering of galaxies and in variations in the density of intergalactic hydrogen gas.

    Cosmic Background Radiation Planck
    CMB from ESA/Planck

    2d
    A 2-D slice through BOSS´s full 3-D map of the universe to date. The black dots going out to about 7 billion light years are relatively nearby galaxies. The colored region beginning at about 10 billion light years is intergalactic hydrogen gas; red areas have more gas and blue areas have less. The blank region between is inaccessible to the Sloan Telescope, but the proposed BigBOSS survey would be able to observe it. Credit: Anže Slosar and BOSS Lyman-alpha cosmology working group

    The oscillations repeat at about 500-million-light-year intervals, and because this scale is firmly anchored in the cosmic microwave background it provides a ruler – a very big one – to measure the history of the expanding universe. With this cosmic yardstick it will be possible to determine just how fast the Universe was expanding at the redshift of the objects in the BOSS survey – in other words, how the expansion rate has changed over time. (Redshift is the degree to which the light from an object speeding away from the viewer is shifted toward the red end of the spectrum.) Knowing whether expansion has accelerated at a constant rate or has varied over time will help decide among the major theories of dark energy.

    Over its five-year extent, BOSS is using two distinct methods to calibrate the markings on the cosmic yardstick. The first method, well tested, will precisely measure 1.5 million luminous red galaxies at “low” redshifts around z = 0.7 (z stands for redshift). The second method will eventually measure the Lyman-alpha forest of 160,000 quasars with high redshifts around z = 2.5. These redshifts correspond to galaxies at distances of 2 to 6 billion light years and quasars at 10 to 11 billion light years.

    Lyman-alpha is the name given to a line in the spectrum of hydrogen, marking the wavelength of light emitted when an excited hydrogen electron falls back to its ground state; it’s a strong signal in the light from quasars. As the quasar’s light passes through intervening clouds of hydrogen gas, additional lines accumulate where the gas clouds absorb the signal, echoing it but shifting by different degrees according to factors including the redshift of the gas cloud and its density. The spectrum of a distant quasar may have hundreds of lines, clumped and blended into a messy, wiggly structure in the spectrum: this is what astronomers call the Lyman-alpha forest.

    “In theory, you can turn any of these absorption lines directly into redshifts and locate the gas cloud precisely,” says Bill Carithers of Berkeley Lab’s Physics Division, who concentrates on extracting relevant information from the noisy data that comes straight from the telescope. “But in practice only the spectra of the very brightest quasars are clean enough to make things that simple.”

    Carithers says that “while a very long exposure could improve the signal-to-noise ratio, that comes at a price. We need lots and lots of quasars to make a map. We can only afford to spend so much telescope time on each.”

    Since the heart of BAO is the correlation distance among density oscillations, the trick turns out to be not overconcentrating on individual spectra but instead measuring the correlations among them. “For any correlation distance, many quasars will contribute,” says Carithers, “so the noise will average and the signal will get stronger. We can say, ‘I’ll use my data, noise and all.’”

    If the attempt to measure density variations in the intergalactic gas is indeed successful, what will the BAO correlation signal from the Lyman-alpha forest look like? Shirley Ho of Berkeley Lab’s Physics Division, working with Slosar and Berkeley Lab’s Martin White, developed simulations to find out.

    zoom
    Zooming in on the map slice shows areas with more gas (red) and less gas (blue) as revealed by correlations of the Lyman-alpha forest data from the spectra of thousands of quasars. A distance of one billion light years is indicated by the scale bar. Credit: Anže Slosar and BOSS Lyman-alpha cosmology working group

    “”We modeled what you would see when you have a BOSS-like data set, and through the simulations we understand the possible sources of systematics when we try with real data to detect the acoustic peak from the Lyman-alpha forest, the signature of baryon acoustic oscillations,” Ho says. Comparing the real data to the simulation confirms whether the search is working as hoped.

    With Peter Nugent, who heads the Computational Cosmology Center at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC), Ho established a 30-terabyte BOSS Project Directory to store the Lyman-alpha simulations, plus the entire Lyman-alpha raw data set as it arrives. The directory also contains a subset of galaxy data and is available to all BOSS collaborators and to the public. The total BOSS data set is stored in a dedicated cluster of computers nicknamed Riemann.

    Targeting the search

    The wide-field Sloan Telescope covers a wide expanse of sky at moderate magnification. To measure both galaxies and quasars, a thousand targets for each BOSS exposure are selected in advance from existing surveys. At the telescope’s focal plane, “plug plates” are precision-machine-drilled with tiny holes at positions of known galaxies and quasars. These holes are plugged with optical fibers that channel the light from each chosen galaxy or quasar to a spectrograph, which isolates the spectrum of each individual object. Schlegel credits Berkeley Lab’s Nicholas Ross for doing much of the “incredibly hard work” involved in this targeting.

    Slosar says, “Our exploratory paper includes less than a tenth of the 160,000 quasars that BOSS will study, but already that’s enough to establish a proof of the concept. This is a potentially revolutionary technique for mapping the very distant universe. We’re paving the way for future BAO experiments like BigBOSS to follow suit.” BigBOSS is a proposed survey that will find precise locations for 20 million galaxies and quasars and go beyond BOSS to encompass 10 times the volume of the finished BOSS map.

    “By the time BOSS ends, we will be able to measure how fast the Universe was expanding 11 billion years ago with an accuracy of a couple of percent,” says Patrick McDonald of Berkeley Lab and Brookhaven, who pioneered techniques for measuring the Universe with the Lyman-alpha forest. “Considering that no one has ever measured the cosmic expansion rate so far back in time, that’s a pretty astonishing prospect.”

    Says Slosar, “We now know we can use the Lyman-alpha forest to look at the dark energy. There is all this structure at the distant universe that has never been seen before. Sometimes I feel like an adventuring cartographer from the Middle Ages!”

    Studying the nature of the Universe can help astrobiologists identify the conditions in which habitable planets are most likely to form around distant stars.

    See this article here.

    Astrobiology Magazine is a NASA-sponsored online popular science magazine. Our stories profile the latest and most exciting news across the wide and interdisciplinary field of astrobiology — the study of life in the universe. In addition to original content, Astrobiology Magazine also runs content from non-NASA sources in order to provide our readers with a broad knowledge of developments in astrobiology, and from institutions both nationally and internationally. Publication of press-releases or other out-sourced content does not signify endorsement or affiliation of any kind.
    Established in the year 2000, Astrobiology Magazine now has a vast archive of stories covering a broad array of topics.

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  • richardmitnick 12:18 pm on August 30, 2014 Permalink | Reply
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    From Don Lincoln at Fermilab: “Particle Detectors Subatomic Bomb Squad ” a Great Video 


    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    The manner in which particle physicists investigate collisions in particle accelerators is a puzzling process. Using vaguely-defined “detectors,” scientists are able to somehow reconstruct the collisions and convert that information into physics measurements. In this video, Fermilab’s Dr. Don Lincoln sheds light on this mysterious technique. In a surprising analogy, he draws a parallel between experimental particle physics and bomb squad investigators and uses an explosive example to illustrate his points. Be sure to watch this video… it’s totally the bomb.

    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

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