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  • richardmitnick 2:58 pm on September 22, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics, Planets   

    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
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics,   

    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
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    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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  • richardmitnick 7:46 pm on January 6, 2014 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From Harvard Smithsonian Center for Astrophysics: “Newfound Planet is Earth-mass But Gassy” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    See the full article here.

    Monday, January 6, 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

    An international team of astronomers has discovered the first Earth-mass planet that transits, or crosses in front of, its host star. KOI-314c is the lightest planet to have both its mass and physical size measured. Surprisingly, although the planet weighs the same as Earth, it is 60 percent larger in diameter, meaning that it must have a very thick, gaseous atmosphere.

    gassy

    “This planet might have the same mass as Earth, but it is certainly not Earth-like,” says David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA), lead author of the discovery. “It proves that there is no clear dividing line between rocky worlds like Earth and fluffier planets like water worlds or gas giants.”

    Kipping presented this discovery today in a press conference at the 223rd meeting of the American Astronomical Society.

    The team gleaned the planet’s characteristics using data from NASA’s Kepler spacecraft. KOI-314c orbits a dim, red dwarf star located approximately 200 light-years away. It circles its star every 23 days. The team estimates its temperature to be 220 degrees Fahrenheit, too hot for life as we know it.

    KOI-314c is only 30 percent denser than water. This suggests that the planet is enveloped by a significant atmosphere of hydrogen and helium hundreds of miles thick. It might have begun life as a mini-Neptune and lost some of its atmospheric gases over time, boiled off by the intense radiation of its star.

    Weighing such a small planet was a challenge. Conventionally, astronomers measure the mass of an exoplanet by measuring the tiny wobbles of the parent star induced by the planet’s gravity. This radial velocity method is extremely difficult for a planet with Earth’s mass. The previous record holder for a planet with a measured mass (Kepler-78b) weighed 70 percent more than Earth.

    To weigh KOI-314c, the team relied on a different technique known as transit timing variations (TTV). This method can only be used when more than one planet orbits a star. The two planets tug on each other, slightly changing the times that they transit their star.

    “Rather than looking for a wobbling star, we essentially look for a wobbling planet,” explains second author David Nesvorny of the Southwest Research Institute (SwRI). “Kepler saw two planets transiting in front of the same star over and over again. By measuring the times at which these transits occurred very carefully, we were able to discover that the two planets are locked in an intricate dance of tiny wobbles giving away their masses.”

    The second planet in the system, KOI-314b, is about the same size as KOI-314c but significantly denser, weighing about 4 times as much as Earth. It orbits the star every 13 days, meaning it is in a 5-to-3 resonance with the outer planet.

    TTV is a very young method of finding and studying exoplanets, first used successfully in 2010. This new measurement shows the potential power of TTV, particularly when it comes to low-mass planets difficult to study using traditional techniques.

    “We are bringing transit timing variations to maturity,” adds Kipping.

    The planet was discovered by chance by the team as they scoured the Kepler data not for exoplanets, but for exomoons. The Hunt for Exomoons with Kepler (HEK) project, led by Kipping, scans through Kepler’s planet haul looking for TTV, which can also be a signature of an exomoon.

    “When we noticed this planet showed transit timing variations, the signature was clearly due to the other planet in the system and not a moon. At first we were disappointed it wasn’t a moon but then we soon realized it was an extraordinary measurement,” says Kipping.

    This research was funded by NASA and the National Science Foundation. A paper detailing the findings has been submitted to The Astrophysical Journal. Its authors are Kipping (CfA), Nesvorny (SwRI), Lars Buchhave (Niels Bohr Institute), Joel Hartman and Gaspar Bakos (Princeton University), and Allan Schmitt (Citizen Science).

    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 4:23 pm on December 16, 2013 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From Harvard-Smithsonian: “SMA Reveals Giant Star Cluster in the Making” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    December 16, 2013
    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

    w49a
    For Release: Monday, December 16, 2013
    Roberto Galván-Madrid (ESO), Hauyu Baobab Liu (ASIAA, Taiwan), Tzu-Cheng Peng (ESO)

    W49A might be one of the best-kept secrets in our galaxy. This star-forming region shines 100 times brighter than the Orion nebula, but is so obscured by dust that very little visible or infrared light escapes. The Smithsonian’s Submillimeter Array (SMA) has peered through the dusty fog to provide the first clear view of this stellar nursery. The SMA revealed an active site of star formation being fed by streamers of infalling gas.

    We were amazed by all the features we saw in the SMA images,” says lead author Roberto Galván-Madrid, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA) and the European Southern Observatory (ESO).

    W49A is located about 36,000 light-years from Earth, on the opposite side of the Milky Way. It represents a nearby example of the sort of vigorous star formation seen in so-called “starburst” galaxies, where stars form 100 times faster than in our galaxy.

    The heart of W49A holds a giant yet surprisingly compact star cluster. About 100,000 stars already exist within a space only 10 light-years on a side. In contrast, fewer than 10 stars lie within 10 light-years of our Sun. In a few million years, the giant star cluster in W49A will be almost as crowded as a globular cluster.

    The SMA also revealed an intricate network of filaments feeding gas into the center, much like tributaries feed water into mighty rivers on Earth. The gaseous filaments in W49A form three big streamers, which funnel star-building material inward at speeds of about 4,500 miles per hour (2 km/sec).

    “Move over, Mississippi!” quips co-author Qizhou Zhang of the CfA.

    Being denser than average will help the W49A star cluster to survive. Most star clusters in the galactic disk dissolve rapidly, their stars migrating away from each other under the influence of gravitational tides. This is why none of the Sun’s sibling stars remain nearby. Since it is so compact, the cluster in W49A might remain intact for billions of years.

    The Submillimeter Array mapped the molecular gas within W49A in exquisite detail. It showed that central 30 light-years of W49A is several hundred times denser than the average molecular cloud in the Milky Way. In total, the nebula contains about 1 million suns’ worth of gas, mostly molecular hydrogen.

    “We suspect that the organized architecture seen in W49A is rather common in massive stellar cluster-formation,” adds co-author Hauyu Baobab Liu of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan.

    The team expects to continue analyzing the SMA data for some time to come.

    “It’s a mine of information,” says Galván-Madrid.

    Their research was published in the December 2013 Astrophysical Journal.

    sma
    The Submillimeter Array (SMA) is an 8-element radio interferometer located atop Mauna Kea in Hawaii. Operating at frequencies from 180 GHz to 700 GHz, the 6m dishes may be arranged into configurations with baselines as long as 509m, producing a synthesized beam of sub-arcsecond width. Each element can observe with two receivers simultaneously, with 2 GHz bandwidth each. The digital correlator backend allows flexible allocation of thousands of spectral channels to each receiver. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica.

    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 4:56 pm on December 12, 2013 Permalink | Reply
    Tags: , , , , Harvard-Smithsonian Center for Astrophysics   

    From Harvard-Smithsonian Center for Astrophysics: “Fast Radio Bursts Might Come From Nearby Stars” 

    Harvard Smithsonian Center for Astrophysics

    Center For Astrophysics

    December 12, 2013
    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

    First discovered in 2007, “fast radio bursts” continue to defy explanation. These cosmic chirps last for only a thousandth of a second. The characteristics of the radio pulses suggested that they came from galaxies billions of light-years away. However, new work points to a much closer origin – flaring stars within our own galaxy.

    flare
    No image credit

    “We propose that fast radio bursts aren’t as exotic as astronomers first thought,” says lead author Avi Loeb of the Harvard-Smithsonian Center for Astrophysics (CfA).

    Fast radio bursts are both brief and bright, packing a lot of energy into a short time. Only six have been discovered to date, all of them in archival data. Each was detected only once, making follow-up studies difficult.

    A detailed analysis of the bursts showed that the pulses passed through a large column of electrons on their way to Earth. If those electrons were spread out across intergalactic space, then the pulses must have crossed billions of light-years. As a result, they would have to come from extremely energetic events. Gamma-ray bursts don’t produce the right radio frequencies, so astronomers looked to other extreme events like the collapse of a neutron star into a black hole.

    Loeb and his colleagues reasoned that if the bursts came from a closer location, within the Milky Way galaxy, then they wouldn’t require as much energy. The explanation could be more mundane.

    Stellar flares fit the bill. Tightly packed electrons in the stellar corona would cause the same effect as the more diffuse intergalactic electrons.

    Two types of stars are known to create radio bursts: young, low mass stars and solar-mass “contact” binaries which orbit so close that they share their outer, gaseous envelopes. Both types of star system would also fluctuate in brightness at optical wavelengths (i.e. visible light).

    To test their theory Loeb and his colleagues searched the locations of three fast radio bursts to look for variable stars, using the telescopes at Tel-Aviv University’s Wise Observatory, in Israel.

    “It was straightforward to monitor these fields for several nights, to see if they showed anything unusual,” says Dani Maoz of Tel Aviv University.

    “We were surprised that, apparently, no one had done this before,” adds Yossi Shvartzvald, a graduate student who led the observations.

    They discovered a contact binary system in one location. The binary consists of two Sun-like stars orbiting each other every 7.8 hours. They are located about 2,600 light-years from Earth. Statistics of stars across the observed field of view show that there is less than a 5 percent chance that the binary star is in the right place by coincidence.

    “Whenever we find a new class of sources, we debate whether they are close or far away,” says Loeb. Gamma-ray bursts were initially thought to be coming from within the Milky Way; only later did astronomers learn they came from cosmological distances.

    “Here we have exactly the opposite,” explains Loeb. Fast radio bursts, initially thought to be distant, may actually originate from our own galaxy.

    The study has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

    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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