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  • richardmitnick 4:44 pm on April 1, 2019 Permalink | Reply
    Tags: Asteroseismology, , , , , , , The planet TOI 197.01 (TOI is short for “TESS Object of Interest”)   

    From Iowa State University: “Data flows from NASA’s TESS Mission, leads to discovery of Saturn-sized planet” 

    From Iowa State University

    Mar 27, 2019

    Steve Kawaler
    Physics and Astronomy
    515-294-9728
    sdk@iastate.edu

    Mike Krapfl
    News Service
    515-294-4917
    mkrapfl@iastate.edu

    1
    A “hot Saturn” passes in front of its host star in this illustration. Astronomers who study stars used “starquakes” to characterize the star, which provided critical information about the planet. See a video illustration of the planet orbiting the star. llustration by Gabriel Perez Diaz, Instituto de Astrofísica de Canarias.

    Astronomers who study stars are providing a valuable assist to the planet-hunting astronomers pursuing the primary objective of NASA’s new TESS Mission.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    In fact, asteroseismologists – stellar astronomers who study seismic waves (or “starquakes”) in stars that appear as changes in brightness – often provide critical information for finding the properties of newly discovered planets.

    This teamwork enabled the discovery and characterization of the first planet identified by TESS for which the oscillations of its host star can be measured.

    The planet – TOI 197.01 (TOI is short for “TESS Object of Interest”) – is described as a “hot Saturn” in a recently accepted scientific paper [The Astronomical Journal by an international team of 141 astronomers. Daniel Huber, an assistant astronomer at the University of Hawaii at Manoa’s Institute for Astronomy, is the lead author of the paper. Steve Kawaler, a professor of physics and astronomy; and Miles Lucas, an undergraduate student, are co-authors from Iowa State University.]. That’s because the planet is about the same size as Saturn and is also very close to its star, completing an orbit in just 14 days, and therefore very hot.

    “This is the first bucketful of water from the firehose of data we’re getting from TESS,” Kawaler said.

    TESS – the Transiting Exoplanet Survey Satellite, led by astrophysicists from the Massachusetts Institute of Technology – launched from Florida’s Cape Canaveral Air Force Station on April 18, 2018. The spacecraft’s primary mission is to find exoplanets, planets beyond our solar system. The spacecraft’s four cameras are taking nearly month-long looks at 26 vertical strips of the sky – first over the southern hemisphere and then over the northern. After two years, TESS will have scanned 85 percent of the sky.

    Astronomers (and their computers) sort through the images, looking for transits, the tiny dips in a star’s light caused by an orbiting planet passing in front of it.

    Planet transit. NASA/Ames

    NASA’s Kepler Mission – a predecessor to TESS – looked for planets in the same way, but scanned a narrow slice of the Milky Way galaxy and focused on distant stars.

    TESS is targeting bright, nearby stars, allowing astronomers to follow up on its discoveries using other space and ground observations to further study and characterize stars and planets. In another paper recently published online by The Astrophysical Journal Supplement Series, astronomers from the TESS Asteroseismic Science Consortium (TASC) identified a target list of sun-like oscillating stars (many that are similar to our future sun) to be studied using TESS data – a list featuring 25,000 stars.

    Kawaler – who witnessed the launch of Kepler in 2009, and was in Florida for the launch of TESS (but a last-minute delay meant he had to miss liftoff to return to Ames to teach) – is on the seven-member TASC Board. The group is led by Jørgen Christensen-Dalsgaard of Aarhus University in Denmark.

    TASC astronomers use asteroseismic modeling to determine a host star’s radius, mass and age. That data can be combined with other observations and measurements to determine the properties of orbiting planets.

    In the case of host star TOI-197, the asteroseismolgists used its oscillations to determine it’s about 5 billion years old and is a little heavier and larger than the sun. They also determined that planet TOI-197.01 is a gas planet with a radius about nine times the Earth’s, making it roughly the size of Saturn. It’s also 1/13th the density of Earth and about 60 times the mass of Earth.

    Those findings say a lot about the TESS work ahead: “TOI-197 provides a first glimpse at the strong potential of TESS to characterize exoplanets using asteroseismology,” the astronomers wrote in their paper.

    Kawaler is expecting that the flood of data coming from TESS will also contain some scientific surprises.

    “The thing that’s exciting is that TESS is the only game in town for a while and the data are so good that we’re planning to try to do science we hadn’t thought about,” Kawaler said. “Maybe we can also look at the very faint stars – the white dwarfs – that are my first love and represent the future of our sun and solar system.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Iowa State University is a public, land-grant university, where students get a great academic start in learning communities and stay active in 800-plus student organizations, undergrad research, internships and study abroad. They learn from world-class scholars who are tackling some of the world’s biggest challenges — feeding the hungry, finding alternative fuels and advancing manufacturing.

    Iowa Agricultural College and Model Farm (now Iowa State University) was officially established on March 22, 1858, by the legislature of the State of Iowa. Story County was selected as a site on June 21, 1859, and the original farm of 648 acres was purchased for a cost of $5,379. The Farm House, the first building on the Iowa State campus, was completed in 1861, and in 1862, the Iowa legislature voted to accept the provision of the Morrill Act, which was awarded to the agricultural college in 1864.

    Iowa State University Knapp-Wilson Farm House. Photo between 1911-1926

    Iowa Agricultural College (Iowa State College of Agricultural and Mechanic Arts as of 1898), as a land grant institution, focused on the ideals that higher education should be accessible to all and that the university should teach liberal and practical subjects. These ideals are integral to the land-grant university.

    The first official class entered at Ames in 1869, and the first class (24 men and 2 women) graduated in 1872. Iowa State was and is a leader in agriculture, engineering, extension, home economics, and created the nation’s first state veterinary medicine school in 1879.

    In 1959, the college was officially renamed Iowa State University of Science and Technology. The focus on technology has led directly to many research patents and inventions including the first binary computer (the ABC), Maytag blue cheese, the round hay baler, and many more.

    Beginning with a small number of students and Old Main, Iowa State University now has approximately 27,000 students and over 100 buildings with world class programs in agriculture, technology, science, and art.

    Iowa State University is a very special place, full of history. But what truly makes it unique is a rare combination of campus beauty, the opportunity to be a part of the land-grant experiment, and to create a progressive and inventive spirit that we call the Cyclone experience. Appreciate what we have here, for it is indeed, one of a kind.

     
  • richardmitnick 12:44 pm on February 5, 2019 Permalink | Reply
    Tags: Asteroseismology, , , , , , Massive collision in the planetary system Kepler 107   

    From Instituto de Astrofísica de Canarias – IAC via Manu: “Massive collision in the planetary system Kepler 107” 


    From Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.

    IAC

    From Instituto de Astrofísica de Canarias – IAC

    Feb. 4, 2019
    Savita Mathur
    smathur@iac.es

    Two of the planets which are orbiting the star Kepler 107 could be the result of an impact similar to that which affected the Earth to produce the Moon. An international team whose members include a researcher from the Instituto de Astrofísica de Canarias and the University of La Laguna, are publishing the results of this work today in the journal Nature Astronomy.

    1
    Hydrodynamics simulation of a high-speed frontal collision between two planets of the landmass. The temperature range of the material is represented by four colors: gray, orange, yellow and red, where the gray is the coldest and the hottest red. Such collisions expel a large amount of silicate mantle material leaving a remaining planet high iron and similar to the observed characteristics of high density Kepler-107c. Credit: ZM Leinhardt and T. Denman (Bristol Univ.)

    Since, in 1995 the first extrasolar planet was discovered almost 4,000 planets have been found around the nearest stars. This allows us to study a large variety of configurations for these planetary systems. The evolution of the planets orbiting other stars can be affected, mainly, by two phenomena: the evaporation of the upper layers of the planet due to the effect of the X-rays and ultraviolet emitted by the central star, and by the impacts of other celestial bodies of the size of a planet.

    The former effect has been observed a number of times in extrasolar systems, but until now there have been no proof of the existence of major impacts, as has apparently occurred in the Kepler 107 system.

    The central star, Kepler 107, is a bit bigger than the Sun, and has four planets rotating around it; it was the two innermost planets which drew the interest of the astrophysicists. Using data from NASA’s Kepler satellite and from the National Galileo Telescope (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands), the team determined the parameters of the star, and measured the radii and masses of these planets. Although the innermost two have similar radii their masses are very different. In fact the second is three times denser than the first.

    NASA/Kepler

    After nine years in deep space, collecting data revealed that
    our night sky was full of thousands of millions of hidden planets, more
    planets even star Kepler space telescope NASA has
    run out of fuel for other scientific operations. NASA has decided to withdraw
    the spacecraft in its current orbit safely and away from Earth. Kepler leaves a
    legacy of more than 2,600 discoveries of planets outside our solar system,
    many of which could be promising places for life.
    More information: http://www.nasa.gov/kepler .
    Credit: NASA / Ames Research Center / W. Stenzel / D. Rutter.
    Last updated: November 2, 2018. Editor: Rick Chen.


    INAF Telescopio Nazionale Galileo, a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain, Altitude 2,396 m (7,861 ft)

    The extraordinarily high density of the planet Kepler 107c is more than double that of the Earth. This exceptional density for a planet has intrigued researchers, and suggests that its metallic core, its densest part, is anomalously big for a planet.

    This would be still considered normal if it were not for the prediction that photo-evaporation causes the densest planet in a system to be the nearest to its star. To explain how it is possible that, in this case, the nearest has only half the density of the second, the hypothesis was proposed that the planet Kepler 107c was formed as the result of a major impact. This impact must have ripped away its outer layers, thus leaving the central core as a much bigger fraction than before. After tests carried out via simulations, this hypothesis seems to be the most likely.

    This study will allow us to better understand the formation and evolution of exoplanets. Specifically it picks out the importance of the relationship between stellar physics and exoplanetary research. “We need to know the star to better understand the planets which are in orbit around it” says Savita Mathur, a researcher at the IAC in Tenerife, and one of the authors of the article. “In this study we made a seismic analysis to estimate the parameters of the star which hosts the planet. Asteroseismology is playing a key role in the field of the exoplanets, because it has been shown that it is one of the best methods for a precise characterization of the stars”. That is why during the past decade it has become one of the main methods for characterizing stars, and it will remain so in the coming years, thanks to the space missions for discovering exoplanets: TESS (NASA) and PLATO (ESA).

    NASA/MIT TESS

    ESA/PLATO


    See the full article here.


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teaching and outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.



    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

     
  • richardmitnick 3:24 pm on September 23, 2018 Permalink | Reply
    Tags: 'Latitudinal differential rotation’, Asteroseismology, Latitudinal differential rotation can be much stronger in some stars than in the Sun, , , Photometric light curves, Solar equators rotate faster than higher latitudes, , Stars are too far away to be resolved in astronomical images. However scientists can indirectly obtain spatial information about stellar interiors using stellar oscillations, Stellar rotation, Stellar rotation is determined by tracking starspots at different latitudes in photometric light curves   

    From Max Planck Institute for Solar System Research: “A new twist on stellar rotation” 

    From Max Planck Institute for Solar System Research

    September 21, 2018

    Prof. Dr. Laurent Gizon
    Max Planck Institute for Solar System Research, Göttingen
    +49 551 384979-439
    gizon@mps.mpg.de

    Dr. Birgit Krummheuer
    Press Office
    Max Planck Institute for Dynamics and Self-Organization, Göttingen
    +49 551 5176-668
    birgit.krummheuer@ds.mpg.de

    Like our sun, distant stars are rotating spheres of hot gas.

    1
    Sun-like stars rotate differentially, with the equator rotating faster than the higher latitudes. The green arrows in the figure represent rotation speed in the stellar convection zone. Differential rotation is inferred from the oscillatory motions of the star seen as orange/blue shades on the right side of the picture. Differential rotation is thought to be an essential ingredient for generating magnetic activity and starspots. © MPS / MarkGarlick.com

    Stars, however, do not rotate like solid spheres: regions at different latitudes rotate at different rates. A group of researchers from New York University and the Max Planck Institute for Solar System Research (MPS) in Germany has now measured the rotational patterns of a sample of Sun-like stars.

    They have identified 13 stars that rotate in a similar fashion as our Sun: their equators rotate faster than their mid latitudes. This rotation pattern is, however, much more pronounced than in the Sun: the stars’ equators are found to rotate up to twice as quickly as their mid-latitudes. This difference in rotation speed is much larger than theories had suggested.

    What do we know about distant stars aside from their brightness and colors? Is our Sun a typical star? Or does it show certain properties that make it special, or maybe even unique? One property that is not fully understood is rotation. In its outer layers the Sun has a rotation pattern that scientists refer to as `latitudinal differential rotation’. This means that different latitudes rotate at different rates. While at the Sun’s equator one full rotation takes approximately 25 days, the higher latitudes rotate more slowly. Near the Sun’s poles, one full rotation takes approximately 31 days.

    In their new work the scientists studied the rotation of 40 stars that resemble the Sun with respect to mass. Among those, the 13 stars for which differential rotation could be measured with confidence all show solar-like differential rotation: equators rotate faster than higher latitudes. In some cases, however, the difference in rotational speed between the equator and the mid-latitudes is much larger than in the Sun.

    Classically, stellar rotation is determined by tracking starspots at different latitudes in photometric light curves. This method is limited, however, because we do not know the latitudes of the starspots. “Using observations from NASA’s Kepler mission we can now probe the interior of stars with asteroseismology and determine their rotational profiles at different latitudes and depths”, says Laurent Gizon, director at MPS.

    Stars are too far away to be resolved in astronomical images. They are point like. However scientists can indirectly obtain spatial information about stellar interiors using stellar oscillations. Stars undergo global acoustic oscillations that are excited by convective motions in their outer layers. Different modes of oscillations probe different regions in a star. Thus the frequencies of oscillation inform us about different regions. In this study the scientists used stellar oscillations to measure rotation at different latitudes in the outer convection zone. “Modes of oscillation that propagate in the direction of rotation move faster than the modes that propagate in the opposite direction, thus their frequencies are slightly different”, says Gizon.

    “Our best measurements all reveal stars with solar-like rotation”, says Gizon. The most surprising aspect of this research is that latitudinal differential rotation can be much stronger in some stars than in the Sun. The scientists did not expect such large values, which are not predicted by numerical models.

    This work is important as it shows that asteroseismology has fantastic potential to help us understand the inner workings of stars. “Information about stellar differential rotation is key to understanding the processes that drive magnetic activity”, says Gizon. Combining information about internal rotation and activity, together with modeling, will most likely reveal the root causes of magnetic activity in stars. However, many more Sun-like stars must be studied for this to happen. In 2026 the European Space Agency will launch the PLATO mission (an exoplanet mission, like Kepler) to characterize tens of thousands of bright Sun-like stars using precision asteroseismology.

    ESA/PLATO

    Large-number statistics will be key to studying the physics of stars and their evolution.

    Science paper:
    Asteroseismic detection of latitudinal differential rotation in 13 Sun-like stars
    Science, 21. September 2018

    See the full article here .

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    Please help promote STEM in your local schools.

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    Max Planck Institute for Solar System Research

    The Max Planck Institute for Solar System Research has had an eventful history – with several moves, changes of name, and structural developments. The first prototype of the current institute was founded in 1934 in Mecklenburg; it moved to Katlenburg-Lindau in 1946. Not just the location of the buildings changed – the topic of research also moved, from Earth to outer space. In the first decades the focus of research was the stratosphere and ionosphere of the Earth, but since 1997 the institute exclusively researches the physics of planets and the Sun. In January 2014 the Max Planck Institute for Solar System Research has relocated to it’s new home: a new building in Göttingen close to the Northern Campus of the University of Göttingen.

     
  • richardmitnick 2:33 pm on March 2, 2018 Permalink | Reply
    Tags: Asteroseismology, , , Bart Bok, , , KIC 08626021, UA's Bok Telescope,   

    From University of Arizona: “Bok to the Future: Sounding the Depths of a Dying Star” 

    U Arizona bloc

    University of Arizona

    March 1, 2018
    Daniel Stolte

    A small, aging telescope can still do mighty science, even helping astrophysicists undertake a virtual journey to the center of a dead star. What they discovered may change our knowledge of how stars — including our sun — evolve and age.

    1
    Vintage workhorse: Dedicated in 1969 and named after Bart Bok, who was director of the UA’s Steward Observatory at the time, the UA’s Bok Telescope has pointed its 90-inch primary mirror at the skies every night except Christmas Eve and a maintenance period during the summer rainy season. (Image courtesy of Steward Observatory)

    U Arizona Steward Observatory at Kitt Peak, AZ, USA, altitude 2,096 m (6,877 ft)

    There are times when having the latest and greatest in technology is not the only thing that counts, even in a field where success depends critically on technological advances, as it does in astronomy.

    This is the story of a telescope and instrument considered “vintage” by today’s standards, and how they allowed one group of researchers to succeed in making a discovery they wouldn’t otherwise have been able to make, had they relied exclusively on the advanced satellite instrument that collected the initial data.

    It all began when data taken by NASA’s Kepler spacecraft revealed that a white dwarf named KIC 08626021, the “corpse” of a star not unlike the sun, was pulsating. That in itself was not unusual. By the time a star becomes a white dwarf, it has burned all of its nuclear fuel and is cooling down for the last time. At several points during the cooling process, a white dwarf becomes unstable, causing it to pulsate simultaneously at multiple different frequencies. These deep vibrations are the key to unveiling the interior of the stellar remnant. The internal chemical stratification of the white dwarf star creates a unique signature in the modulation of the light coming out of the star, which, once deciphered, allows scientists to obtain a cartography of its internal structure.

    Astronomers who study how stars are born, how they age and how they die believe that white dwarfs, especially pulsators such as KIC 08626021, give us a preview of the afterlife of our sun, long after it has consumed our planet in its fiery throes of death. In fact, the vast majority of stars in the universe will end up as white dwarfs. These stellar relics retain the imprints of past physical processes such as nuclear burning and episodes of convective mixing — phenomena that are not all that well understood in the actual modeling of stellar evolution theory. To have a glimpse at the internal structure and composition of these stars allows scientists to better elucidate the physics at play during all phases of stellar evolution, including those occurring in our sun.

    But in the case of KIC 08626021, something was off. The pulsations that Kepler observed in this star were too rapid for the type of white dwarf that it was initially reported to be, based on the models astronomers commonly use to investigate these stars.

    “A light spectrum taken with the William Herschel Telescope on La Palma in the Canary Islands suggested that its atmosphere contained only helium and no hydrogen,” says Elizabeth Green, an associate astronomer at the University of Arizona’s Steward Observatory who helped decipher the star’s true nature.


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

    “This was a problem because a white dwarf of that type should have a cooler temperature and therefore slower oscillations than what Kepler saw.”

    Journey to the Center of a Star

    Green was part of an international team of astrophysicists from Toulouse, France; Montreal; Tucson; Liège, Belgium; and Beijing who set out to unravel the internal composition of KIC 08626021 by deciphering the brightness oscillations observed at its surface, using asteroseismology, a technique similar to methods that geophysicists use to study the structure of the Earth, analyzing the seismic waves caused by earthquakes. The researchers published their results in a recent article in the journal Nature.

    “In order to successfully model a star with asteroseismology, one needs to make the model as realistic as possible,” Green says. “This means that the values for a large number of different parameters must be specified: the total mass and radius of the star, the atmospheric temperature, the thickness and composition of the atmosphere and, in the case of a white dwarf like this one, whose interior is stratified in layers of different elements, the mass, thickness and composition of each interior layer.”

    In the process of modeling the interiors of stars, theoreticians first construct a range of theoretical stellar models covering all the possible values of every unknown parameter, and determine what pulsational frequencies would be excited in each one. Then they compare the resulting sets of model frequencies to the observed frequencies to see if there are any matches, and if so, which ones match the observations the best.

    “For stellar asteroseismology,” Green explains, “one of the best ways to prove that your models are realistic is to analyze a spectrum of the light from the star, determine its effective temperature and gravity, and show that these values agree with the temperature and gravity of the best asteroseismic model.”

    To do this, Green spent several nights pointing Steward’s Bok Telescope on Kitt Peak at the white dwarf KIC 08626021 — 1,376 light-years away in the constellation Cygnus. Using the telescope’s B&C spectrograph, she measured the amount of light that the star emits at different wavelengths, to obtain the so-called spectrum that her colleagues later analyzed to determine the actual atmospheric parameters of the dead star.

    Light Hits Arizona Mountaintop

    “Obtaining enough individual spectra to combine into a single useful spectrum was no small feat considering that this was a rather faint star for a telescope of this size,” Green says. “Nevertheless, we had enough time allocated to do the job properly. It would have been much more difficult to do with other, more powerful telescopes and instruments elsewhere, which have much more intense competition for observing time.”

    Green’s observations helped clear up a mystery that resulted in the proper classification of KIC 08626021. Her spectrum was the first to show convincingly that this white dwarf’s atmosphere was not composed entirely of helium, but contained significant traces of hydrogen as well. “Since hydrogen has a large effect on the opacity of the atmosphere, the slightly different atmospheric composition resulted in a higher calculated effective temperature for the star, consistent with its relatively rapid pulsations,” she says.

    The best-fitting asteroseismic solution not only matched the pulsational frequencies observed by the Kepler satellite “beautifully,” according to Green, “but now it also agreed extremely well with the temperature and gravity determined from the Bok Telescope spectrum.”

    Peeling back the different layers of the white dwarf revealed that the stellar core of these stars is bigger and richer in oxygen than predicted, and provided clues to all the main chemical elements present. In addition, a precise knowledge of the internal chemical composition of white dwarfs also is useful as a “cosmological chronometer” allowing astronomers to determine the ages of the various stellar populations of our galaxy.

    “To me, the most exciting part about this study is that we now have ‘observed’ values for things like the core size and oxygen abundance at the very center of a star that is nearing the end of its stellar life,” Green says. “It’s almost like real X-ray vision. These new results will be used to refine our knowledge of physical processes that take place in extreme conditions in the interiors of nearly all stars.”

    The study, “A large oxygen-dominated core from the seismic cartography of a pulsating white dwarf,” was led by Noemi Giammichele at the Institut de Recherche en Astrophysique et Planétologie (IRAP) of Toulouse, France.

    See the full article here .

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    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
  • richardmitnick 3:36 pm on January 2, 2018 Permalink | Reply
    Tags: 16 Cyg A and 16 Cyg B, A deep look into the hearts of stars, Asteroseismology, , , , , Inverse method-derived the local properties of the stellar interior from the observed frequencies,   

    From Max Planck Institute for Solar System Research: “A deep look into the hearts of stars” 


    Max Planck Institute for Solar System Research

    January 02, 2018

    Dr. Birgit Krummheuer
    Press and Public Relations
    Max Planck Institute for Solar System Research, Göttingen
    +49 551 384979-462
    Krummheuer@mps.mpg.de

    Earl Bellinger
    Max Planck Institute for Solar System Research, Göttingen
    +49 551 384979-518
    Bellinger@mps.mpg.de

    Dr. Saskia Hekker
    Max Planck Institute for Solar System Research, Göttingen
    +49 551 384979-264
    Hekker@mps.mpg.de

    Researchers measure the inner structure of distant suns from their pulsations

    1
    A glimpse into the heart: Artist’s impression of the interior of the star, which was studied through its surface oscillations.
    © Earl Bellinger / ESA

    At first glance, it would seem to be impossible to look inside a star. An international team of astronomers, under the leadership of Earl Bellinger and Saskia Hekker of the Max Planck Institute for Solar System Research in Göttingen, has, for the first time, determined the deep inner structure of two stars based on their oscillations.

    Our Sun, and most other stars, experience pulsations that spread through the star’s interior as sound waves. The frequencies of these waves are imprinted on the light of the star, and can be later seen by astronomers here on Earth. Similar to how seismologists decipher the inner structure of our planet by analyzing earthquakes, astronomers determine the properties of stars from their pulsations—a field called asteroseismology. Now, for the first time, a detailed analysis of these pulsations has enabled Earl Bellinger, Saskia Hekker and their colleagues to measure the internal structure of two distant stars.

    The two stars they analyzed are part of the 16 Cygni system (known as 16 Cyg A and 16 Cyg B) and both are very similar to our own Sun.

    2
    http://www.daviddarling.info/encyclopedia/A/16Cyg.html

    “Due to their small distance of only 70 light years, these stars are relatively bright and thus ideally suited for our analysis,” says lead author Earl Bellinger [The Astrophysical Journal]. “Previously, it was only possible to make models of the stars’ interiors. Now we can measure them.”

    To make a model of a star’s interior, astrophysicists vary stellar evolution models until one of them fits to the observed frequency spectrum. However, the pulsations of the theoretical models often differ from those of the stars, most likely due to some stellar physics still being unknown.

    Bellinger and Hekker therefore decided to use the inverse method. Here, they derived the local properties of the stellar interior from the observed frequencies. This method depends less on theoretical assumptions, but it requires excellent measurement data quality and is mathematically challenging.

    Using the inverse method, the researchers looked more than 500,000 km deep into the stars—and found that the speed of sound in the central regions is greater than predicted by the models. “In the case of 16 Cyg B, these differences can be explained by correcting what we thought to be the mass and the size of the star,” says Bellinger. In the case of 16 Cyg A, however, the cause of the discrepancies could not be identified.

    It is possible that as-yet unknown physical phenomena are not sufficiently taken into account by the current evolutionary models. “Elements that were created in the early phases of the star’s evolution may have been transported from the core of the star to its outer layers,” explains Bellinger. “This would change the internal stratification of the star, which then affects how it oscillates.”

    This first structural analysis of the two stars will be followed by more. “Ten to twenty additional stars suitable for such an analysis can be found in the data from the Kepler Space Telescope,” says Saskia Hekker, who leads the Stellar Ages and Galactic Evolution (SAGE) Research Group at the Max Planck Institute in Göttingen. In the future, NASA’s TESS mission (Transiting Exoplanet Survey Satellite) and the PLATO (Planetary Transits and Oscillation of Stars) space telescope planned by the European Space Agency (ESA) will collect even more data for this research field.

    NASA/Kepler Telescope

    NASA/TESS

    ESA/PLATO

    The inverse method delivers new insights that will help to improve our understanding of the physics that happens in stars. This will lead to better stellar models, which will then improve our ability to predict the future evolution of the Sun and other stars in our Galaxy.

    See the full article here .

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    Max Planck Institute for Solar System Research

    The Max Planck Institute for Solar System Research has had an eventful history – with several moves, changes of name, and structural developments. The first prototype of the current institute was founded in 1934 in Mecklenburg; it moved to Katlenburg-Lindau in 1946. Not just the location of the buildings changed – the topic of research also moved, from Earth to outer space. In the first decades the focus of research was the stratosphere and ionosphere of the Earth, but since 1997 the institute exclusively researches the physics of planets and the Sun. In January 2014 the Max Planck Institute for Solar System Research has relocated to it’s new home: a new building in Göttingen close to the Northern Campus of the University of Göttingen.

     
  • richardmitnick 11:03 am on February 20, 2017 Permalink | Reply
    Tags: Asteroseismology, , , , , , , The Sun In A Distant Mirror   

    From astrobites: “The Sun In A Distant Mirror” 

    Astrobites bloc

    Astrobites

    Title: A Distant Mirror: Solar Oscillations Observed on Neptune by the Kepler K2 Mission
    Authors: P. Gaulme et al.
    First Author’s Institution: Department of Astronomy, New Mexico State University
    1
    Status: Published in The Astrophysical Journal Letters, open access

    1
    Figure 1: Snapshot of the line-of-sight velocity variations on the Sun’s surface, measured from the Doppler shift of atmospheric absorption lines. (Image: GONG/NSO/AURA/NSF)

    How can we learn what lies beneath the surface of a star? One approach, called asteroseismology, is to study a star’s vibrations to infer its internal structure. The inside structure of the Sun in particular can be studied in great detail, because its vibrations are actually apparent on its surface (Fig. 1, see also: Helioseismology): The visible pattern of surface quivers shows the imprint of global acoustic oscillations, which are caused by resonant waves traveling through the Sun on peculiar paths, probing various depths. The same must be happening in faraway stars, yet due to their distance only the variability of their overall properties can be measured, for instance changes in brightness or temperature, which are however similarly caused by the stars’ intrinsic oscillations.

    An impressive instrument that has been built specifically to measure the brightness of stars with extreme precision over time is the Kepler space telescope.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    Its primary aim is to detect the transits of exoplanets, but its features make it suitable for asteroseismology as well. The authors of today’s paper investigate how Kepler would see a Sun-like star from far away, by pointing it at Neptune.

    Methods

    The key idea of the paper is to determine the oscillation characteristics of the Sun by analyzing the intensity variations of the sunlight reflected by Neptune. This kind of measurement would allow a novel check of the calibration of widely used scaling relations, by observing the reference star – the Sun – with the same instrument as the actual target stars. These scaling relations are equations that connect the measurable (asteroseismic) quantities with the fundamental stellar properties, for example mass and radius.

    The main parameters of interest are the oscillation frequency of the Sun at maximum amplitude (\nu_{max}), which corresponds to the dominant “5-minute oscillation”, and the mean frequency separation between overtones (\Delta\nu), which are weaker oscillations that are also excited. The paper’s authors split up into seven teams to independently measure these parameters, all using slightly different methods of analysis. The underlying data, namely the light curve and its power spectrum (a decomposition of the light curve into frequency components), are treated just like the data of any other Kepler target (Fig. 2).

    2
    Figure 2: Left: The full Neptune light curve taken with Kepler, showing the intensity variations of the reflected sunlight over 49 days in 1 minute intervals. Right: The gray and black lines are the raw and smoothed power spectrum of the Neptune light curve. The solid red line is the best-fit model, which includes several noise components indicated by the dashed red lines. The main signal due to the 5-minute oscillations of the Sun appears at the bottom right of the plot, around 3100 μHz. For comparison, the green line shows simultaneous VIRGO data (see text). The blue peaks are caused by Neptune’s rotation. (Figure 1 from the paper.)

    Results

    Surprisingly, all teams consistently overestimate the mass and radius of the Sun significantly by about 14% and 4%, assuming the standard solar reference values. However, this discrepancy can be explained by comparison with another, simultaneous light curve that was taken with the dedicated Sun-observing instrument VIRGO (on board the SOHO satellite).

    ESA/NASA SOHO
    ESA/NASA SOHO

    The true value of \nu_{max} was larger than usual during the time of observations, simply due to the random nature of the Sun’s oscillations.

    In addition, the teams attempted to determine not just the frequency spacing, but also the heights and widths of the individual overtones (“peak-bagging”), to create a complete model of the observed oscillation spectrum. The results are rather uncertain due to noise, but the findings of the teams are generally consistent, and they agree well with the VIRGO measurements, after differences in the technical design have been taken into account (e.g. different bandpasses).

    The successful indirect detection of the Sun’s acoustic oscillations in intensity measurements, with Neptune as “a distant mirror”, is a marvelous technological achievement. Not only that, but the lessons learned from this experiment will help further explore the limits of high-precision asteroseismology with Kepler.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 1:08 pm on December 22, 2016 Permalink | Reply
    Tags: Asteroseismology, , , ,   

    From Kavli: “Revealing the Orbital Shape Distributions of Exoplanets with China’s LAMOST Telescope” 

    KavliFoundation

    The Kavli Foundation

    12/22/2016

    Using data from China’s LAMOST telescope, a team of astronomers have derived how the orbital shapes distribute for extrasolar planets. The work is recently published in the journal Proceedings of the National Academy of Sciences of the United States of America” (PNAS). The lead authors are Prof. Jiwei Xie from Nanjing University and Prof. Subo Dong, a faculty member of the Kavli Institute of Astronomy & Astrophysics (KIAA) at Peking University.

    LAMOST telescope located in Xinglong Station, Hebei Province, China
    The Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) telescope in Hebei, China. It is the most efficient spectroscopy machine in the world.

    Until two decades ago, the only planetary system known to mankind was our own solar system. Most planets in the solar system revolve around the Sun on nearly circular orbits, and their orbits are almost on the same plane within about 3 degrees on average (i.e., the averaged inclination angle is about 3 degrees). Astronomers use the parameter called eccentricity to describe the shape of a planetary orbit. Eccentricity takes the value between 0 and 1, and the larger the eccentricity, the more an orbit deviates from circular. The averaged eccentricity of solar system planets is merely 0.06. Hundreds of years ago, motivated by circular and coplanar planetary orbits, Kant and Laplace hypothesized that planets should form in disks, and this theory has developed into the “standard model” on how planets form.

    In 1995, astronomers discovered the first exoplanet around a Sun-like star 51 Pegasi with a technique called Radial Velocity, and this discovery started an exciting era of exoplanet exploration. At the beginning of the 21st Century, people had discovered hundreds of exoplanets with the Radial Velocity technique, and most of them are giant planets comparable in mass with the Jupiter. These Jovian planets are relatively rare, found around approximately one tenth of stars studied by the Radial Velocity technique. The shapes of their orbits were a big surprise: a large fraction of them are on highly eccentric orbits, and all the giant planets found by Radial Velocity have a mean eccentricity of about 0.3. This finding challenges the “standard model” of planet formation and raises a long-standing puzzle for astronomers – are the nearly circular and coplanar planetary orbits in the solar system common or exceptional?

    The Kepler satellite launched by NASA in 2009 has discovered thousands of exoplanets by monitoring tiny dimming in the brightness of stars when their planets happen to cross in the front (called “transit”).

    Planet transit. NASA/Ames
    Planet transit. NASA/Ames

    Many of the planets discovered by Kepler have sizes comparable to that of the Earth. Kepler’s revolutionary discoveries show that Earth-size planets are prevalent in our galaxy. However, data from the Kepler satellite alone cannot be used to measure the shape of a transiting exoplanet’s orbit. To do so, one way is to use the size of the planet host star as a “ruler” to measure against the length of the planet transit, while implementing this method needs precise information on the host star parameters such as size and mass. This method has previously been applied to the host stars characterized with the asteroseismology technique but the sample is limited to a relatively small number of stars with high-frequency, exquisite brightness information required by asteroseismology.

    With its innovative design, the LAMOST telescope in China can observe spectra of thousands of celestial objects simultaneously within its large field of view, and it is currently the most efficient spectroscopy machine in the world (Figure 1). In recent years, LAMOST has obtained tens of thousands of stellar spectra in the sky region where the Kepler satellite monitors planet transits, and they include many hundreds of stars hosting transiting exoplanets. By comparing with other methods such as asteroseismology, the research team finds that, high-accuracy characterization of stellar parameters can be reliably obtained from LAMOST spectra, and they can subsequently be used to measure the the orbital shape distributions of Kepler exoplanets.

    They analyze a large sample of about 700 exoplanets whose host stars have LAMOST spectra, and with the LAMOST stellar parameters and Kepler transit data, they measure the eccentricity and inclination angle distributions. They find that about 80% of the analyzed planet orbits are nearly circular (averaged eccentricity less than 0.1) like those in the solar system, and only about 20% of the planets are on relatively eccentric orbits that significantly deviate from circular (average eccentricity large than 0.3). They also find that the average eccentricity and inclination angle for the Kepler systems with multiple planets fit into the pattern of the solar system objects (Figure 2).

    Therefore, circular orbits are not exceptional for planetary systems, and the orbital shapes of most planets inside and outside the solar system appear to distribute in a similar fashion. This implies that the formation and evolution processes leading to the distributions of the orbital shapes of the solar system may be common in the Galaxy.

    See the full article here .

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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

     
    • vegetarian dash diet meal pla 1:39 pm on December 22, 2016 Permalink | Reply

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      • richardmitnick 2:27 pm on December 22, 2016 Permalink | Reply

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  • richardmitnick 9:10 am on January 16, 2016 Permalink | Reply
    Tags: Asteroseismology, , , Stellar Revelations,   

    From UCSB: “Stellar Revelations” 

    UC Santa Barbara Name bloc

    January 4, 2016
    Julie Cohen

    Temp 1
    Internal magnetic fields of red giants are up to 10 million times stronger than the Earth’s. No image credit found.

    Temp 2
    Jim Fuller, Matteo Cantiello and Lars Bildsten.Photo Credit: Bill Wolf

    Using a recently developed technique to detect magnetic fields inside stars, a group of astronomers — including Matteo Cantiello and Lars Bildsten from UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP) — has discovered that strong magnetic fields are very common in stars. The group’s findings appear in the journal Nature.

    “We have applied a novel theoretical idea that we developed just a few months ago to thousands of stars and the results are just extraordinary,” said Cantiello, a specialist in stellar astrophysics at KITP.

    Previously, only a very small percentage of stars were known to have strong magnetic fields. Therefore, current scientific models of how stars evolve do not include magnetic fields as a fundamental component.

    “Such fields have simply been regarded as insignificant for our general understanding of stellar evolution,” said lead author Dennis Stello, an astrophysicist at the University of Sydney in Australia. “Our result clearly shows this assumption needs to be revisited because we found that up to 60 percent of stars host strong fields.”

    3
    The life cycle of a Sun-like star.

    4
    Born from clouds of gas and dust, stars like our Sun spend most of their lifetime slowly burning their primary nuclear fuel, hydrogen, into the heavier element helium. After leading this bright and shiny life for several billion years, their fuel is almost exhausted and they start swelling, pushing the outer layers away from what has turned into a small and very hot core. These “middle-aged” stars become enormous, hence cool and red — red giants. All red giants exhibit a slow oscillation in brightness due their rhythmic “breathing” in and out, and one third of them are also affected by additional, slower and mysterious changes in their luminosity. After this rapid and tumultuous phase of their later life, these stars do not end in dramatic explosions, but die peacefully as planetary nebulae, blowing out everything but a tiny remnant, known as white dwarf.

    Until now, astronomers have been unable to detect these magnetic fields because such fields hide deep in the stellar interior, out of sight from conventional observation methods that measure only the surface properties of stars. The research team turned to asteroseismology, a technique that probes beyond the stellar surface, to determine the presence of very strong magnetic fields near the stellar core.

    “The stellar core is the region where the star produces most of its energy through thermonuclear reactions,” Cantiello explained. “So the field is likely to have important effects on how stars evolve since it can alter the physical processes that take place in the core.”

    Most stars — like the sun — are subject to continuous oscillations. “Their interior is essentially ringing like a bell,” noted co-author Jim Fuller, a postdoctoral scholar from the California Institute of Technology in Pasadena. “And like a bell or a musical instrument, the sound produced reveals physical properties, such as size, temperature and what they are made of.”

    The researchers used very precise data from NASA’s Kepler space telescope to measure tiny brightness variations caused by the ringing sound inside thousands of stars.

    NASA Kepler Telescope
    NASA/Kepler

    They found that certain oscillation frequencies were missing in 60 percent of the stars due to suppression by strong magnetic fields in the stellar cores.

    “It’s like having a trumpet that doesn’t sound normal because something is hiding inside it, altering the sound it produces,” Stello said.

    This magnetic suppression effect had previously been seen in only a few dozen stars. However, the new analysis of the full data set from Kepler revealed that this effect is prevalent in stars that are only slightly more massive than the sun.

    According to Cantiello, such intermediate mass stars are hotter and more luminous, and their cores are stirred by convection. “We believe that the magnetic field is created by this ‘boiling’ sequence and stored inside the star for the remaining evolutionary phase. Astrophysicists previously have suggested this but it was very speculative; now it seems clear that this is the case,” he said.

    “This is a very important result that will enable scientists to test more directly current theories for how magnetic fields form and evolve in stellar interiors,” said co-author Bildsten, the director of KITP. “When a star dies, the presence of strong magnetic fields can have a profound impact, possibly resulting in some of the brightest explosions in the universe.”

    This research could potentially lead to a better general understanding of stellar magnetic dynamos, including the one controlling the sun’s 11-year sunspot cycle, which is known to affect communication systems and cloud cover on Earth.

    “So far, the study of stellar magnetic dynamos principally relied on computer simulations, which now can be tested using these new exciting observations,” said Fuller.

    See the full article here .

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    UC Santa Barbara Seal

    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 5:33 am on October 27, 2015 Permalink | Reply
    Tags: Asteroseismology, , ,   

    From UCSB: “Magnetic Hide and Seek” 

    UC Santa Barbara Name bloc

    KITP Kavli Institute for Theoretical Physics UCSB

    October 22, 2015
    Julie Cohen

    Researchers at the Kavli Institute for Theoretical Physics develop a new technique to detect magnetic fields inside stars

    1
    This artist’s representation of a red giant star with a strong internal magnetic field shows sound waves propagating in the stellar outer layers, while gravity waves propagate in the inner layers where a magnetic field is present.

    Magnetic fields have important consequences in all stages of stellar evolution, from a star’s formation to its demise. Now, for the first time, astrophysicists are able to determine the presence of strong magnetic fields deep inside pulsating giant stars.

    A consortium of international researchers, including several from UC Santa Barbara’s Kavli Institute for Theoretical Physics (KITP), used asteroseismology — a discipline similar to seismology — to track waves traveling through stars in order to determine their inner properties. Their findings appear in the journal Science.

    2
    Jim Fuller, Matteo Cantiello and Lars Bildsten Photo Credit: Bill Wolf

    “We can now probe regions of the star that were previously hidden,” said co-lead author Matteo Cantiello, a specialist in stellar astrophysics at KITP. “The technique is analogous to a medical ultrasound, which uses sound waves to image otherwise invisible parts of the human body.”

    Cantiello’s curiosity and that of his co-authors was sparked when astrophysicist Dennis Stello of the University of Sydney presented puzzling data from the Kepler satellite, a space telescope that measures stellar brightness variations with very high precision.

    NASA Kepler Telescope
    NASA/Kepler

    Cantiello, KITP director Lars Bildsten and Jim Fuller, a postdoctoral fellow at the California Institute of Technology, agreed that this was a mystery worth solving. After much debate, many calculations and the additional involvement of Rafael García, a staff scientist at France’s Commissariat à l’Énergie Atomique, a solution emerged. The data were explained by the presence of strong magnetic fields in the inner regions of these stars.

    The puzzling phenomenon was observed in a group of red giants imaged by Kepler. Red giants are stars much older and larger than the sun. Their outer regions are characterized by turbulent motion that excites sound waves, which interact with gravity waves that travel deep into the stellar core. Magnetic fields in the core can hinder the motions produced by the gravity waves.

    “Imagine the magnetic field as stiff rubber bands embedded in the stellar gas, which affect the propagation of gravity waves,” Fuller explained. “If the magnetic field is strong enough, the gravity waves become trapped in the star’s core. We call this the magnetic greenhouse effect.”

    The trapping occurs because the incoming wave is reflected by the magnetic field into waves with a lower degree of symmetry, which are prevented from escaping the core. As a result, stellar surface oscillations have smaller amplitude compared to a similar star without a strong magnetic field.

    “We used these observations to put a limit on — or even measure — the internal magnetic fields for these stars,” Cantiello said. “We found that red giants can possess internal magnetic fields nearly a million times stronger than a typical refrigerator magnet.

    “This is exciting as internal magnetic fields play an important role both for the evolution of stars and for the properties of their remnants,” Cantiello added. “For example, some of the most powerful explosions in the universe — long gamma-ray bursts — are associated with the death of some huge stars. These behemoths — 10 or more times more massive than our sun — most likely ended their lives with strong magnetic fields in their cores.”

    This work was written collaboratively on the web. A public, open Science version of the published paper can be found on Authorea, including a layman’s summary.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

    University of California Seal

     
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