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  • richardmitnick 4:05 pm on December 15, 2014 Permalink | Reply
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    From CfA: “Magnetic Fields on Solar-Type Stars” 

    Smithsonian Astrophysical Observatory
    Smithsonian Astrophysical Observatory

    Friday, December 12, 2014
    No Writer Credit

    The Sun rotates slowly, about once every 24 days at its equator although the hot gas at every latitude rotates at a slightly different rate. Rotation helps to drive the mechanisms that power stellar magnetic fields, and in slowly rotating solar-type stars also helps to explain the solar activity cycle. In the case of solar-type stars that rotate much faster than does the modern-day Sun, the dynamo appears to be generated by fundamentally different mechanisms that, along with many details of solar magnetic field generation, are not well understood. Astronomers trying to understand dynamos across a range of solar-type stars (and how they evolve) have been observing a variety of active stars, both slow and fast rotators, to probe how various physical parameters of stars enhance or inhibit dynamo processes.

    f
    Vivid orange streamers of super-hot, electrically charged gas (plasma) arc from the surface of the Sun reveal the structure of the solar magnetic field rising vertically from a sunspot. Astronomers are now studying the magnetic fields on solar-type stars using techniques of polarimetry.
    Hinode, JAXA/NASA

    Most techniques used to observe stellar magnetism rely on indirect proxies of the field, for example on characteristics of the radiation emitted by atoms. Surveys using these proxies have found clear dependencies between rotation and the stellar dynamo and the star’s magnetic cycles, among other things. Recent advances in instrumentation that can sense the polarization of the light extend these methods and have made it possible to directly measure solar-strength magnetic fields on other stars.

    CfA astronomer Jose-Dias do Nascimento is a member of a team of astronomers that has just completed the most extensive polarization survey of stars to date. They detected magnetic fields on sixty-seven stars, twenty-one of them classified as solar-type, about four times as many solar-type stars as had been previously classified. The scientists found that the average field increases with the stellar rotation rate and decreases with stellar age, and that its strength correlates with emission from the stars’ hot outer layers, their chromospheres. Not only does this paper represent the most extensive survey to date of its kind, it demonstrates the power of the polarization technique. It signals that it is possible to greatly expand the study of magnetic fields in solar-type stars, which efforts will continue to improve our understanding of the surface fields in the Sun.

    See the full article here.

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    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.

     
  • richardmitnick 3:04 pm on December 11, 2014 Permalink | Reply
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    From NOVA: “Preserving the Astronomical Past” 

    PBS NOVA

    NOVA

    Wed, 10 Dec 2014
    Shraddha Chakradhar

    On a small hill in the heart of Cambridge, Massachusetts, 170 tons of glass, imprinted with history, sit in a dimly lit corner. Each rectangular plate is about the size of a sheet of paper and, with the exception of black ink spots, the collection is surprisingly clear, especially when you consider that some date as far back as 1885. A casual eye might easily mistake one of the 500,000 photographic plates for nothing more than a dirt-specked piece of glass.

    Slide them into a plate viewer—a device reminiscent of an X-ray light box in a doctor’s office—pick up an eyepiece, and suddenly the universe appears. The spots resolve into stars, planets, even entire galaxies. The Plate Stacks Collection of the Harvard-Smithsonian Center for Astrophysics (CfA) is the largest of its kind in the world. The collection spans more than a century’s worth of astronomical images, from the first taken in 1885 to the last in 1992. Among its firsts, the collection includes an early image of the Andromeda galaxy in 1897 as well as the 1910 sighting of Halley’s comet. Thanks to the foresight of Edward Pickering, director of the observatory in the late 19th and early 20th centuries who began to collect images from observatories in Peru, the collection spans both hemispheres, too. It is an astronomical record of unprecedented proportions.

    i
    An [unidentified] image taken at the Harvard Observatory, now the CfA, on July 24, 1952

    And one of historical significance. These plates are what Pickering’s Women, known as the Harvard Computers, pored over to observe and record stellar variability, the natural change in brightness that all stars demonstrate throughout their lives. (Similar studies today are called “time domain astronomy.”) Edwin Hubble used many of the images in the collection, like those of the Magellanic Clouds, in addition to the Computers’ work on stellar variability, to hone his model for the universe’s expansion.

    “You can really tell what I like to call ‘sea change’ in the understanding of the skies when you look at these plates,” says Alison Doane, curator of the collection. “What we now know as the Andromeda galaxy is labeled as Andromeda nebula because they didn’t know at the time” that it was a galaxy, she adds.
    It is an astronomical record of unprecedented proportions.

    Despite its importance, many astronomers don’t have access to the collection’s rich data—100-year-old glass plates [because they]aren’t easily shipped around the world, so scientists must make a trip to Cambridge to dig through the archive. Making sense of it all requires scouring through old notebooks kept by the Computers or spending hours hunched over the plates, meticulously noting distance between stars or measuring their relative brightness.

    But now, a project dedicated to digitizing the plates in the collection, is changing that. Known as Digital Access to a Sky Century @Harvard, or DASCH, the project is the brainchild of Jonathan Grindlay, professor of astronomy at Harvard University, and is enabling astronomical discoveries of the future. “This collection is proving to be very important for time domain astronomy, which is the hot field in astronomy right now,” Grindlay says. And the Harvard glass plate collection is, “the only collection that offers both a large duration of 100 years as well as coverage of both hemispheres.”
    Historical Markings

    Despite the string of superlatives attached to the project, getting astronomers on board with digitization projects like DASCH has proven difficult. When Elizabeth Griffin, an astrophysicist at the Dominion Astrophysical Observatory in Victoria, Canada, speaks to people individually, she says that they see the reasoning behind preserving photographic plates and agree that something needs to be done. “But when the community comes together and needs to make a formal decision, it’s much more in the vein of, ‘Who wants this old stuff when we have all this other interesting new material?’”

    To Wayne Osborn, formerly at the University of Chicago’s Yerkes Observatory in Wisconsin, preserving astronomical glass plates is of tremendous importance. “I got interested in this because I was surprised to find that a couple of major observatories had taken a series of photographs [with these plates] and had gotten rid of them,” Osborn says. “My initial interest was of rescue and preservation. And I’ve since been trying to encourage people to keep their photographic plates and catalog them.”

    For both Griffin and Osborn, plate collections like the one at Harvard contain more than just astronomical information—they are historical artifacts. For instance, Gerard Kuiper, the astronomer and the namesake of the Kuiper belt, moved from Yerkes Observatory to the University of Arizona in the 1960s, taking with him nearly 2,500 plates. These plates were never returned to Yerkes, and so Osborn and his wife made a trip down to the University of Arizona to retrieve them. “We found several notebooks [of Kuiper’s] along with the collection, including some notebooks that belonged to astronomers from Princeton University,” Osborn says. “It included documentation of the 1900 solar eclipse,” one of the first eclipses to be photographed.

    a
    The 10 ½ inch round Armagh-Dunsink-Harvard telescope

    Many of plates have notes directly on them, too. “Comments, handwriting, markings—these plates have all kinds of annotations,” Osborn says. “So then it becomes a matter of capturing not just what’s within these plates, but also what’s on them.” In the case of DASCH, when Doane and her team of volunteers who work on scanning these plates come upon a plate with markings, they take a digital photograph of the plate itself, to capture the markings, but then erase any markings before the plate is loaded onto the scanner. It becomes, then, a struggle between preservation for the sake of history versus for the sake of science. So far, science seems to be winning.

    “The project was not done to preserve history,” Grindlay says. “We’re obviously doing that by making the data available. But in the competitive climate [of funding] these days, that never would have carried the day.”

    Digital Discovery

    At the CfA, the custom-built DASCH scanner is busy scanning plates. The device is massive, resembling a large microscope attached to a futuristic table saw. It can handle two plates at a time, taking 60 mini-images of each in 90 seconds and knitting them together. The entire process of loading, scanning, and unloading a plate takes about two minutes. Cleaning each plate before the scanning process eats up more time. Now at the rate of roughly 300 plates per day, DASCH has successfully scanned close to 80,000 plates since its inception in 2006. Still, that’s only about 20% of the sky. To accomplish the task, the sky has been split up into 12 sections of 15˚ of galactic latitude each, and the data is released upon completion. In June 2014, the team released the third set of data. So far, the data that has been scanned from the three sets contains nearly 3.5 billion magnitudes.

    f
    Alison Doane inspects a plate of the Small Magellanic Cloud taken on a 24[?]

    The process doesn’t stop at just creating a digital copy of the photographic images on the plates. The software behind the scanner, which was written from scratch, calculates magnitudes of stellar variability within the plates and compares it with calibrated data from preexisting catalogs of stellar variability. Already, Grindlay and other astronomers analyzing the data have discovered several new objects and new kinds of stellar variables, the existence of which were previously unknown.

    “There are anywhere from 30-50 thousand stars in every plate that we scan, sometimes even 100,000,” Doane says. “That’s a lot of information that can be tapped into to learn about our universe.”

    n
    Alison Doane places a positive copy of the Small Magellanic Cloud on top of a negative of the same image. The Computers would pore over these composites to discover new variable stars.

    For instance, Grindlay and his team have been studying the data from DASCH for stellar mass black holes, which are black holes formed by the collapse of massive stars. Their formation is often preceded by a sudden flare-up, from a nova or supernova, so Grindlay began to look for these stellar black holes by looking for outbursts. “We started looking at the ones in regions of the sky we had already scanned and, lo and behold, we found four of these objects that have had previous outbursts,” he says. “They had occurred 50 to even 100 years before the outbursts that occurred in modern times.” One of these objects was only discovered because, in 1999, a modern X-ray telescope detected an outburst—but Grindlay was able to identify its 1901 outburst using DASCH data. Another similar object, which was discovered in 1999, seems to have had an outburst in 1928, according to Grindlay’s findings.

    “It’s not just on one plate—each of these has maybe three or four—in some cases even eight—observations that allow us to measure the duration of the outburst,” added Grindlay. Given that these are rare events, “if you only see them 1% of the time, and you see a few that are very similar in their outburst duration and intervals between outbursts, then you can immediately infer that there are many, many more than you would have otherwise thought.”

    Given that less than a fifth of the sky has been scanned at DASCH, it remains to be seen what else might emerge from the plates. And while the DASCH project holds tremendous promise for the discovery and better understanding of astronomical phenomena, it’s not yet a success story. Astronomers have been trying, largely unsuccessfully, to preserve historical plates ever since they went out of use in the late 1980s.

    For Griffin, the Dominion astrophysicist, “It’s been a lifelong involvement.” “When I started my career in the ’60s, these were the only way to record such images.” Griffin, who studies stellar spectra and the evolution of stars, really began to champion the preservation of these plates since much of her work also depended on looking at data from the past. “I often found myself thinking, wouldn’t it be great if I didn’t have to track down these plates, then make the trip to get them, and then scan them before I even got to analyzing the data.”

    Plate Shelter

    The CfA’s plate collection sits in a crowded corner, and neither Doane nor Grindlay has a plan for where the plates will go if the CfA is further pressed for space. DASCH’s plight is not unique. One of the main reasons only about 50 plate collections exist in the entire world is because of space constraints. “The challenge is storing them correctly and having a place to store them,” Osborn says. “The conditions under which they’re stored are critical. They can’t be in very high temperatures nor can they withstand high humidity.”

    Fortunately, there is one place that’s interested in storing as many plates as possible—the Pisgah Astronomical Research Institute, or PARI. Affiliated with the University of North Carolina system, this educational facility has opened its own center for the preservation of photographic plates, the Astronomical Photographic Data Archive (APDA), largely to help other institutions that are looking to get rid of their glass plate collections.

    “I got a call in 2004 about an astronomer, Nancy Houk at the University of Michigan, who was retiring and looking to donate her collection,” says Michael Castelaz, the science director at PARI and an associate professor of physics at Brevard College. “We took her collection and word started to spread about our place taking collections.” APDA was formally established in 2007 and is now home to more than 40 collections—nearly 220,000 plates—from all over the country. And though the archive’s primary goal is to accept and preserve collections, the group is also making the move toward digitization. But unlike DASCH, which is supported by National Science Foundation grants, APDA has largely had to fend for itself.

    h
    The Harvard Observatory in 1899

    Castelaz and PARI set up a Kickstarter campaign in 2013 to help raise funds to begin the digitization, but less than a third of its $67,000 goal was met, so the group had to return the money. They then turned to Indiegogo in February 2014, knowing that they would be able to keep whatever money they did raise, and were able to raise enough money—more than $20,000—to restore one of the two scanners they had acquired to help with the digitization.

    “We finally restored this machine,” Castelaz says, “and only just started our first round of scans. We don’t yet know what kinds of things we will find.” But for many, like Osborn and Griffin, discovery isn’t the sole motivation. “Astronomical data is part of our scientific heritage,” Griffin emphasizes. “It’s very wide and broad. You just do not know how science will evolve, and we don’t know which of these data will be important.” Osborn echoes this sentiment, adding that simply digitizing these records to make the data freely available isn’t enough.

    “I think it’s good to keep the original record,” Osborn says. “My preference would be to keep several storage locations, perhaps divided up based on specialties,” he says, referring to the different astronomical phenomena captured on the plates—eclipses, asteroids, galaxies, and so on. Because many of the plates were not stored under proper conditions even when they were in active use, he says it would be beneficial to “get the data off of them as soon as possible” before they deteriorate in condition.
    “You just do not know how science will evolve, and we don’t know which of these data will be important.”

    Digitizing the data could also open up a treasure trove of historical data to a new generation. Given how difficult the plates have been to access, few newly minted astronomers think to use them. “These collections are stored away somewhere, and younger astronomers tend to not have an interest in these,” says Castelaz, echoing a sentiment shared by nearly everyone who works with these plates. “But I expect it to be more dynamic as time goes by and these digitized files gain more traction.”

    “The best way at all to generate interest is to discover very unexpected and possibly controversial things,” Griffin says. Currently, she adds, “They’re finding hundreds of variable stars, which are still only getting the interest of people that are really interested in that particular field of study.”

    For Grindlay and his team, however, discovery is enough. “The average person wouldn’t have much reason to believe why there would be more black holes than we originally thought,” says Grindlay, adding, “but this is basic science. These are very exotic objects that are being formed in very bizarre ways and we’re trying to peel back layers of the onion to understand how nature produces these things.”

    For the others, preservation of these plates for the potential they hold is worth fighting for. “One of the biggest misconceptions is that they’re old and therefore useless,” says Castelaz. “But I would say that they are old and therefore timeless.”

    See the full article here.

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    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.

     
  • richardmitnick 11:04 am on October 24, 2014 Permalink | Reply
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    From CfA: “Accreting Supermassive Black Holes in the Early Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    October 24, 2014
    No Writer Credit

    Supermassive black holes containing millions or even billions of solar-masses of material are found at the nuclei of galaxies. Our Milky Way, for example, has a nucleus with a black hole with about four million solar masses of material. Around the black hole, according to theories, is a torus of dust and gas, and when material falls toward the black hole (a process called accretion) the inner edge of the disk can be heated to millions of degrees. Such accretion heating can power dramatic phenomena like bipolar jets of rapidly moving charged particles. Such actively accreting supermassive black holes in galaxies are called active galactic nuclei (AGN).

    torus
    Torus

    The evolution of AGN in cosmic time provides a picture of their role in the formation and co-evolution of galaxies. Recently, for example, there has been some evidence that AGN with more modest luminosities and accretion rates (compared to the most dramatic cases) developed later in cosmic history (dubbed “downsizing”), although the reasons for and implications of this effect are debated. CfA astronomers Eleni Kalfontzou, Francesca Civano, Martin Elvis and Paul Green and a colleague have just published the largest study of X-ray selected AGN in the universe from the time when it was only 2.5 billion years old, with the most distant AGN in their sample dating from when the universe was about 1.2 billion years old.

    The astronomers studied 209 AGN detected with the Chandra X-ray Observatory.

    NASA Chandra Telescope
    NASA/Chandra

    image
    A multicolor image of galaxies in the field of the Chandra Cosmic Evolution Survey. A large, new study of 209 galaxies in the early universe with X-ray bright supermassive black holes finds that more modest AGN tend to peak later in cosmic history, and that obscured and unobscured AGN evolve in similar ways.
    X-ray: NASA/CXC/SAO/F.Civano et al. Optical: NASA/STScI

    They note that the X-ray observations are less contaminated by host galaxy emission than optical surveys, and consequently that they span a wider, more representative range of physical conditions. The team’s analysis confirms the proposed trend towards downsizing, while it also can effectively rule out some alternative proposals. The scientists also find, among other things, that this sample of AGN represents nuclei with a wide range of molecular gas and dust extinction. Combined with the range of AGN dates, this result enables them to conclude that obscured and unobscured phases of AGN evolve in similar ways.

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

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  • richardmitnick 2:58 pm on September 22, 2014 Permalink | Reply
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    From CfA: “Is Pluto a Planet? The Votes Are In “ 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    September 22, 2014
    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    What is a planet? For generations of kids the answer was easy. A big ball of rock or gas that orbited our Sun, and there were nine of them in our solar system. But then astronomers started finding more Pluto-sized objects orbiting beyond Neptune. Then they found Jupiter-sized objects circling distant stars, first by the handful and then by the hundreds. Suddenly the answer wasn’t so easy. Were all these newfound things planets?

    Pluto

    Since the International Astronomical Union (IAU) is in charge of naming these newly discovered worlds, they tackled the question at their 2006 meeting. They tried to come up with a definition of a planet that everyone could agree on. But the astronomers couldn’t agree. In the end, they voted and picked a definition that they thought would work.

    The current, official definition says that a planet is a celestial body that:

    is in orbit around the Sun,
    is round or nearly round, and
    has “cleared the neighborhood” around its orbit.

    But this definition baffled the public and classrooms around the country. For one thing, it only applied to planets in our solar system. What about all those exoplanets orbiting other stars? Are they planets? And Pluto was booted from the planet club and called a dwarf planet. Is a dwarf planet a small planet? Not according to the IAU. Even though a dwarf fruit tree is still a small fruit tree, and a dwarf hamster is still a small hamster.

    Eight years later, the Harvard-Smithsonian Center for Astrophysics decided to revisit the question of “what is a planet?” On September 18th, we hosted a debate among three leading experts in planetary science, each of whom presented their case as to what a planet is or isn’t. The goal: to find a definition that the eager public audience could agree on!

    Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU’s viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the exoplanet scientist’s viewpoint.

    Gingerich argued that “a planet is a culturally defined word that changes over time,” and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as “the smallest spherical lump of matter that formed around stars or stellar remnants,” which means Pluto is a planet.

    After these experts made their best case, the audience got to vote on what a planet is or isn’t and whether Pluto is in or out. The results are in, with no hanging chads in sight.

    According to the audience, Sasselov’s definition won the day, and Pluto IS a planet.

    The video of the debate and audience vote can be seen on YouTube at https://www.youtube.com/user/ObsNights. [Or, you can watch it right here.]

    Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

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  • richardmitnick 10:20 pm on July 11, 2014 Permalink | Reply
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    From CfA: “Sun-like Stars Reveal Their Ages” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 10, 2014
    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    Defining what makes a star “Sun-like” is as difficult as defining what makes a planet “Earth-like.” A solar twin should have a temperature, mass, and spectral type similar to our Sun. We also would expect it to be about 4.5 billion years old. However, it is notoriously difficult to measure a star’s age so astronomers usually ignore age when deciding if a star counts as “Sun-like.”

    star

    A new technique for measuring the age of a star using its spin – gyrochronology – is coming into its own. Today astronomers are presenting the gyrochronological ages of 22 Sun-like stars. Before this, only two Sun-like stars had measured spins and ages.

    “We have found stars with properties that are close enough to those of the Sun that we can call them ‘solar twins,'” says lead author Jose Dias do Nascimento of the Harvard-Smithsonian Center for Astrophysics (CfA). “With solar twins we can study the past, present, and future of stars like our Sun. Consequently, we can predict how planetary systems like our solar system will be affected by the evolution of their central stars.”

    To measure a star’s spin, astronomers look for changes in its brightness caused by dark spots known as starspots crossing the star’s surface. By watching how long it takes for a spot to rotate into view, across the star and out of view again, we learn how fast the star is spinning.

    The change in a star’s brightness due to starspots is very small, typically a few percent or less. NASA’s Kepler spacecraft excels at such exacting brightness measurements.

    NASA Kepler Telescope
    NASA/Kepler

    Using Kepler, do Nascimento and his colleagues found that the Sun-like stars in their study spin once every 21 days on average, compared to the 25-day rotation period of our Sun at its equator.

    Younger stars spin faster than older ones because stars slow down as they age, much like humans. As a result, a star’s rotation can be used like a clock to derive its age. Since most of the stars the team studied spin slightly faster than our sun, they tend to be younger too.

    This work expands on previous research done by CfA astronomer (and co-author on the new study) Soren Meibom. Meibom and his collaborators measured the rotation rates for stars in a 1-billion-year-old cluster called NGC 6811. Since the stars had a known age, astronomers could use them to calibrate the gyrochronology “clock.” The new research led by do Nascimento examines free-floating “field” stars that are not members of a cluster.

    Since stars and planets form together at the same time, by learning a star’s age we learn the age of its planets. And since it takes time for life to develop and evolve, knowing the ages of planet-hosting stars could help narrow down the best targets to search for signs of alien life. Although none of the 22 stars in the new study are known to have planets, this work represents an important step in the hunt for Sun-like stars that could host Earth-like planets.

    The paper was accepted for publication in The Astrophysical Journal Letters and is available online.

    Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.


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  • richardmitnick 8:46 am on June 13, 2014 Permalink | Reply
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    From CfA: “Mining Data Archives Yields Haul of ‘Red Nuggets'” 

    Smithsonian Astrophysical Observatory

    CfA

    June 11, 2014
    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    Leslie Sage
    Canadian Astronomical Society
    301-675-8957
    cascapressofficer@gmail.com

    The world of astronomy has changed. An astronomer used to have to travel to a remote location and endure long, cold nights, patiently guiding a telescope to collect precious photons of light. Now, a proliferation of online archives allows astronomers to make discoveries from the comfort of their own offices.

    By mining such archives, a team of astronomers led by Ivana Damjanov of the Harvard-Smithsonian Center for Astrophysics (CfA) has found a treasure trove of “red nugget” galaxies. These galaxies are compact and densely packed with old, red stars. Their abundance provides new constraints on theoretical models of galaxy formation and evolution.

    rn

    “These red nugget galaxies were hiding in plain view, masquerading as stars,” says Damjanov. She presented the team’s research today at a meeting of the Canadian Astronomical Society (CASCA) in Quebec, QC.

    When the universe was young, dense, massive galaxies nicknamed “red nuggets” were common. These galaxies are ten times more massive than the Milky Way, but their stars are packed into a volume a hundred times smaller than our Galaxy.

    Mysteriously, astronomers searching the older, nearer universe could not find any of these objects. Their apparent disappearance, if real, signaled a surprising turn in galaxy evolution.

    To find nearby examples, Damjanov and her colleagues Margaret Geller, Ho Seong Hwang, and Igor Chilingarian (Smithsonian Astrophysical Observatory) combed through the database of the largest survey of the universe, the Sloan Digital Sky Survey. The red nugget galaxies are so small that they appear like stars in Sloan photographs, due to blurring from Earth’s atmosphere. However, their spectra give away their true nature.

    The team identified several hundred red nugget candidates in the Sloan data. Then they searched a variety of online telescope archives in order to confirm their findings. In particular, high-quality images from the Canada-France-Hawaii Telescope and the Hubble Space Telescope showed that about 200 of the candidates were galaxies very similar to their red-nugget cousins in the distant, young universe.

    “Now we know that many of these amazingly small, dense, but massive galaxies survive. They are a fascinating test of our understanding of the way galaxies form and evolve,” explains Geller.

    The large number of red nuggets discovered in Sloan told the team how abundant those galaxies were in the middle-aged universe. That number then can be compared to computer models of galaxy formation. Different models for the way galaxies grow predict very different abundances.

    The picture that matches the observations is one where red nuggets begin their lives as very small objects in the young universe. During the next ten billion years some of them collide and merge with other, smaller and less massive galaxies. Some red nuggets manage to avoid collisions and remain compact as they age. The result is a variety of elliptical galaxies with different sizes and masses, some very compact and some more extended.

    “Many processes work together to shape the rich landscape of galaxies we see in the nearby universe,” says Damjanov.

    See the full article here.

    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.


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  • richardmitnick 5:10 pm on May 7, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From CFA: “Astronomers Create First Realistic Virtual Universe” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    May 7, 2014
    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    Move over, Matrix – astronomers have done you one better. They have created the first realistic virtual universe using a computer simulation called “Illustris.” Illustris can recreate 13 billion years of cosmic evolution in a cube 350 million light-years on a side with unprecedented resolution.

    ill

    “Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously,” says lead author Mark Vogelsberger (MIT/Harvard-Smithsonian Center for Astrophysics), who conducted the work in collaboration with researchers at several institutions, including the Heidelberg Institute for Theoretical Studies in Germany.

    These results are being reported in the May 8th issue of the journal Nature.

    Previous attempts to simulate the universe were hampered by lack of computing power and the complexities of the underlying physics. As a result those programs either were limited in resolution, or forced to focus on a small portion of the universe. Earlier simulations also had trouble modeling complex feedback from star formation, supernova explosions, and supermassive black holes.

    Illustris employs a sophisticated computer program to recreate the evolution of the universe in high fidelity. It includes both normal matter and dark matter using 12 billion 3-D “pixels,” or resolution elements.

    The team dedicated five years to developing the Illustris program. The actual calculations took 3 months of “run time,” using a total of 8,000 CPUs running in parallel. If they had used an average desktop computer, the calculations would have taken more than 2,000 years to complete.

    The computer simulation began a mere 12 million years after the Big Bang. When it reached the present day, astronomers counted more than 41,000 galaxies in the cube of simulated space. Importantly, Illustris yielded a realistic mix of spiral galaxies like the Milky Way and football-shaped elliptical galaxies. It also recreated large-scale structures like galaxy clusters and the bubbles and voids of the cosmic web. On the small scale, it accurately recreated the chemistries of individual galaxies.

    Since light travels at a fixed speed, the farther away astronomers look, the farther back in time they can see. A galaxy one billion light-years away is seen as it was a billion years ago. Telescopes like Hubble can give us views of the early universe by looking to greater distances. However, astronomers can’t use Hubble to follow the evolution of a single galaxy over time.

    “Illustris is like a time machine. We can go forward and backward in time. We can pause the simulation and zoom into a single galaxy or galaxy cluster to see what’s really going on,” says co-author Shy Genel of the CfA.

    The team is releasing a high-definition video, which morphs between different components of the simulation to highlight various layers (e.g. dark matter density, gas temperature, or chemistry). They also are releasing several smaller videos and associated imagery online at http://www.illustris-project.org/

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.


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  • richardmitnick 2:37 pm on March 14, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From CfA: “The Billion-Dollar Telecope Race” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    Thursday, March 13, 2014

    When Warner Brothers animators wanted to include cutting-edge astronomy in a 1952 Bugs Bunny cartoon they set a scene at an observatory that looks like Palomar Observatory in California. The then-newly unveiled Hale Telescope, stationed at Palomar, had a 5-meter-diameter mirror, the world’s largest. In 1989, when cartoonist Bill Watterson included a mention of the world’s largest telescope in a “Calvin and Hobbes” cartoon, he again set the action at Palomar. Although computers had grown a million times faster during those 38 years, and eight different particle colliders had been built and competed for their field’s top ranking, astronomy’s king of the hill stayed perched on its throne.

    Palomar Observatory
    Palomar

    This changed in 1992, with the introduction of the Keck telescope and its compound, 10-meter mirror. About a dozen 8-10 meter telescopes have been built since. But it has been more than 20 years since this last quantum leap in telescope technology. Now, finally, the next generation is coming. Three telescopes are on their way, and the race among them has already begun.

    Keck Observatory
    Keck I and II on Mauna Kea, Hawaii

    ESO VLT
    ESO’s 8.2 meter VLT intsallation at Cerro Paranal, high in the Atacama Desert, Chile

    Three new observatories are on the drawing boards, all with diameters, or apertures, between 25 and 40 meters, and all with estimated first light being collected in 2022: the Giant Magellan Telescope (GMT, headquartered in Pasadena, Calif.), the Thirty Meter Telescope (TMT, also in Pasadena) and the European Extremely Large Telescope (E-ELT, headquartered in Garching, Germany). At stake are the mapping of asteroids, dwarf planets, and planetary moons in our solar system; imaging whole planetary systems; observing close-in the Goliathan black hole at the Milky Way’s core; discovering the detailed laws governing star and galaxy formation; and taking baby pictures of the farthest objects in the early universe.

    Giant Magellan Telescope
    Giant Magellan Telescope, to be built in Chile

    Thirty Meter Telescope
    TMT, destined for Mauna Kea Hawaii

    ESO E-ELT
    ESO’s E-ELT, to be built at Cerro Armazones, Chile

    Thanks to these telescopes, astronomy is poised to reinvent itself over the next few decades. Renown and glory, headlines and prestige, and perhaps a few Nobel Prizes too, will go to those astronomers that first reveal a bit of new cosmic machinery. Surprisingly, the story of this race will be written, not just in the technical specifications and design breakthroughs of the instruments themselves, but also in the organizational approaches that each team has taken. The horse race is a unique window both into technology, and into the process of science itself.

    [It needs to be noted here, and it never is, that time on almost all of the great observatories of the world is alloted to a great extent to those astronomers who reside the the countries that spend the money to build and maintain the observatories. So, again, to the greatest extent, U.S. astronomers are for the most part, not completely, but for the most part, shut out of ESO searches. Similarly, most of the time on NASA observatories goes to U.S. astronomers, except that ESA funded 15% of Hubble. The U.S. has contributed to various ESA observatories, so U.S. astronomers get some time there. It is quite possible for a U.S. astronomer to get attached to an ESO team. I have seen evidence of this, and similar associations across other borders. But, make no mistake: money counts.

    It will greatly help with ALMA that there is European, U.S., and Japanese money in the program. We will see what happens with SKA.]

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.


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  • richardmitnick 2:21 pm on March 14, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From CfA: “The Workings of an X-ray Binary Star” 

    Smithsonian Astrophysical Observatory

    March 14, 2014
    No Writer Credit

    LMC-X-3
    LMX X-3

    xray
    A schematic image of the X-ray binary source LMC X-3 (not to scale). The disk around the black hole (on the right) is heated by accretion of material falling from the star (at the left) onto the disk, while some X-ray emission from the disk then heats the companion star. Astronomers were able to explain this process by modeling the time delay between the infrared and X-ray flares.

    The bright X-ray source known as LMC X-3 resides in the Large Magellanic Cloud, the dwarf galaxy that is the Milky Way’s nearest neighbor. Two decades ago astronomers discovered that the source is actually a binary system with a normal star rapidly orbiting a nearby black hole (whose mass is about 2.3 solar-masses) in only 1.7 days. In X-ray binary systems like this one, material from the normal star falls onto a disk around the black hole, causing it to glow and emit radiation – at X-ray wavelengths from the inner portion of the disk closest to the black hole, and at infrared wavelengths from the outer portions of the disk. The emission typically varies in time, presumably because the infalling matter arrives in clumps or in an uneven stream. The infrared and X-ray emissions also vary from one another, and astronomers have long thought that modeling their behaviors might lead to an enhanced understanding of black hole accretion processes.

    CfA astronomers James Steiner and Jeff McClintock, along with a team of five colleagues, analyzed a ten-year collection of optical, infrared and X-ray data on LMC X-3. They discovered from the relative timing of the flares as seen in the two bands that the X-ray emission events lagged the infrared emission by about two weeks, and were able to develop a model that can successfully explain the processes at work. They considered the radiation as coming from three locations: the star itself (normal starlight dominates the emission), the disk (it is heated by accretion and emits in both X-rays and infrared), and other hot material in the disk and/or the star (it is heated by X-rays from the hot inner disk).

    The scientists are able to conclude that the infrared probably arises from a narrow annular region of the disk, a somewhat surprising result because it had been thought that infrared would come from a much wider area. They also derive a more precise orbital period for the binary (1.704805 days) and key parameters of the disk. The authors note, however, that their model has about thirty parameters; their proposed scenario is the one that best fits the whole set of data. The new work is an impressive success at understanding a complex and dramatic extragalactic black hole system.

    See the full article here.
    About CfA

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy. The long relationship between the two organizations, which began when the SAO moved its headquarters to Cambridge in 1955, was formalized by the establishment of a joint center in 1973. The CfA’s history of accomplishments in astronomy and astrophysics is reflected in a wide range of awards and prizes received by individual CfA scientists.

    Today, some 300 Smithsonian and Harvard scientists cooperate in broad programs of astrophysical research supported by Federal appropriations and University funds as well as contracts and grants from government agencies. These scientific investigations, touching on almost all major topics in astronomy, are organized into the following divisions, scientific departments and service groups.


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  • richardmitnick 2:59 pm on January 8, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics,   

    From Harvard- Smithsonian Center for Astrophysics: “A One-Percent Measure of Galaxies Half the Universe Away” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    Wednesday, January 8, 2014
    For more information, contact:

    David A. Aguilar
    Director of Public Affairs
    Harvard-Smithsonian Center for Astrophysics
    617-495-7462
    daguilar@cfa.harvard.edu

    Christine Pulliam
    Public Affairs Specialist
    Harvard-Smithsonian Center for Astrophysics
    617-495-7463
    cpulliam@cfa.harvard.edu

    Researchers from the Baryon Oscillation Spectroscopic Survey (BOSS) today announced that they have measured the distance to galaxies more than six billion light years away to an unprecedented accuracy of just one percent. Their measurements place new constraints on the properties of the mysterious “dark energy” thought to permeate empty space, which causes the expansion of the Universe to accelerate.

    uni

    “There are not many things in our daily life that we know to one-percent accuracy,” said David Schlegel, a physicist at Lawrence Berkeley National Laboratory (LBNL) and the principal investigator of BOSS. “I now know the size of the Universe better than I know the size of my house.”

    The new distance measurements were presented today at a meeting of the American Astronomical Society by astronomer Daniel Eisenstein (Harvard-Smithsonian Center for Astrophysics), the director of the Sloan Digital Sky Survey III (SDSS-III), the worldwide collaboration of which BOSS is a part.

    “Determining distance is a fundamental challenge of astronomy,” said Eisenstein. “You see something in the sky – how far away is it? Once you know how far away it is, learning everything else about it is suddenly much easier.”

    Throughout history, astronomers have met this challenge using many different techniques: for example, distances to planets in the solar system can be measured quite accurately using radar, but for more distant objects, astronomers must turn to less-direct methods.

    Regardless of the method, every measurement has some uncertainty, which can be expressed as a percentage of the thing being measured. For example, if you measure the distance from Washington, D.C. to New York (200 miles) to within two miles of the true value, you have measured to an accuracy of one percent.

    Only a few hundred stars and a few star clusters are close enough to have distances measured to one-percent accuracy. Nearly all of these stars are only a few thousand light-years away, and all are still within our own Milky Way galaxy. Reaching out a million times farther away, the new BOSS measurements probe far beyond our Galaxy to map the Universe with unparalleled accuracy.

    With these new, highly accurate distance measurements, BOSS astronomers are making new inroads in the quest to understand dark energy. “We don’t yet understand what dark energy is,” explained Eisenstein, “but we can measure its properties. Then, we compare those values to what we expect them to be, given our current understanding of the Universe. The better our measurements, the more we can learn.”

    Making a one-percent measurement at a distance of six billion light-years requires a completely different technique from measurements in the solar system or the Milky Way. BOSS, the largest of the four projects that make up the Sloan Digital Sky Survey III (SDSS-III), was built to take advantage of this technique: measuring the so-called “baryon acoustic oscillations” (BAOs), subtle periodic ripples in the distribution of galaxies in the cosmos.

    These ripples are imprints of pressure waves that moved through the early Universe, which was so hot and dense that particles of light (photons) moved along with the protons and neutrons (known collectively as “baryons”) that today make up the nuclei of atoms. The original size of these ripples is known, and their size today can be measured by mapping galaxies.

    Making these measurements required mapping the locations of 1.2 million galaxies. BOSS uses a specialized instrument that can make detailed measurements of 1000 galaxies at a time.

    The BOSS measurements are consistent with a form of dark energy that stays constant through the history of the Universe. This “cosmological constant” is one of just six numbers needed to make a model that matches the shape and large-scale structure of the Universe. Schlegel likens this six-number model to a pane of glass, which is pinned in place by bolts that represent different measurements of the history of the Universe.

    “BOSS now has one of the tightest of those bolts, and we just gave it another half-turn,” said Schlegel. “Each time you ratchet up the tension and the glass doesn’t break, that’s a success of the model.”

    See the full article here.

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.


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