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  • richardmitnick 5:25 pm on December 26, 2021 Permalink | Reply
    Tags: "Active Galactic Nuclei have a history of causing trouble", , , , , Cessation of star formation is known as “quenching”., , , It turns out that the most important factor in quenching a galaxy is the mass of the central supermassive black hole which powers an AGN., Messier 87* black hole, Spiral galaxies and elliptical galaxies., , The Eagle simulation, The Illustris Simulation, The IllustrisTNG collaboration, The Sloan Digital Sky Survey   

    From astrobites : “Active Galactic Nuclei have a history of causing trouble” 

    Astrobites bloc

    From astrobites

    Title: On the quenching of star formation in observed and simulated central galaxies: Evidence for the role of integrated AGN feedback

    Authors: Joanna M. Piotrowska, Asa F. L. Bluck, Roberto Maiolino, Yingjie Peng

    First Author’s Institution: The University of Cambridge (UK)

    Status: Accepted for publication in MNRAS.

    When studying galaxies, we can usually split them into two main families: spiral galaxies, and elliptical galaxies. The obvious difference between these two is their shape. Spiral galaxies, like the Milky Way, have a fragile, detailed structure, with spiral arms stretching out from their centres.

    Credit: R. Hurt/NASA JPL-Caltech(US) Milky Way The bar is visible in this image.

    This is strikingly different to the plain, featureless shapes of elliptical galaxies.

    Hubble Illuminates Cluster of Diverse Galaxies (Abell S0740) – This image from NASA’s Hubble Space Telescope shows the diverse collection of galaxies in the cluster Abell S0740 that is over 450 million light-years away in the direction of the constellation Centaurus.
    The giant elliptical ESO 325-G004 looms large at the cluster’s center. The galaxy is as massive as 100 billion of our suns. Hubble resolves thousands of globular star clusters orbiting ESO 325-G004. Globular clusters are compact groups of hundreds of thousands of stars that are gravitationally bound together. At the galaxy’s distance they appear as pinpoints of light contained within the diffuse halo.
    Other fuzzy elliptical galaxies dot the image. Some have evidence of a disk or ring structure that gives them a bow-tie shape. Several spiral galaxies are also present. The starlight in these galaxies is mainly contained in a disk and follows along spiral arms.
    This image was created by combining Hubble science observations taken in January 2005 with Hubble Heritage observations taken a year later to form a 3-color composite. The filters that isolate blue, red and infrared light were used with the Advanced Camera for Surveys aboard Hubble.
    However, the other difference between these is their colours. Spiral galaxies usually have a much more blue colour, compared to orange or red elliptical galaxies. This is because spiral galaxies contain large supplies of gas that can be used to form new stars, which have a bright blue colour due to their higher temperatures. Elliptical galaxies, which are not forming many new stars, mostly contain old, cool, red stars.

    National Aeronautics and Space Administration(US)/European Space Agency [Agence spatiale européenne] [Europäische Weltraumorganisation](EU) Hubble Space Telescope.

    National Aeronautics Space Agency(US)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU) Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope(US)

    This cessation of star formation is known as “quenching”. But what causes certain galaxies to quench? One suspect is supermassive black holes, which live right in the centres of galaxies. As their name suggests, these objects are big, with masses ranging from millions to billions of times that of our Sun. This means that they produce tremendously strong gravitational fields, which can accelerate nearby material almost to the speed of light. When lots of material surrounds a black hole, it can form an accretion disk, a structure made out of incredibly fast-moving material that throws out vast amounts of light and energy.

    This kind of supermassive black hole is referred to as an Active Galactic Nucleus, or AGN. These are some of the brightest objects in the Universe. A now-famous example is the AGN in the centre of the galaxy Messier 87, which was the subject of the first ever photograph of a black hole, taken in 2019 by the Event Horizon Telescope.

    Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via The Event Horizon Telescope Collaboration released on 10 April 2019 via National Science Foundation(US).

    EHT map.

    The energy thrown out by an AGN can heat up the gas in a galaxy, or eject this gas from a galaxy altogether, and either of these mechanisms has the ability to stop star formation in its tracks. Today’s paper investigates the properties of AGN in quenched and star-forming galaxies, to gain an even deeper understanding of the role that AGN play in quenching.

    Winding back the clock

    The authors of today’s paper use data from the Sloan Digital Sky Survey (SDSS), a huge observational survey of galaxies.

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft).

    Apache Point Observatory near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).

    They also combine this with data from three different computer simulations of galaxies: EAGLE, Illustris and IllustrisTNG.

    Eagle simulation. https://icc.dur.ac.uk/Eagle/highlights.php
    The Eagle simulation.

    Credit: The Illustris Simulation.

    Visualization of the intensity of shock waves in the cosmic gas (blue) around collapsed dark matter structures (orange/white). Similar to a sonic boom, the gas in these shock waves is accelerated with a jolt when impacting on the cosmic filaments and galaxies. Credit: The IllustrisTNG collaboration.

    This allows them to observe galaxies at the present day, and then use simulations to study how these galaxies looked in the past. Using both simulations and observations, they investigate how a range of AGN and galaxy properties correlate with quenching; these properties include the supermassive black hole mass, mass of stars in the galaxy, and the mass of gas in the halo that surrounds each galaxy.

    Several parameters correlate with the likelihood of galaxies to be quenched – for example, quenched galaxies generally contain a greater mass of stars. However, using Machine Learning techniques, the authors are able to pick up causal relationships, to determine which properties are truly responsible for quenching. Figure 1 shows the relative impact of each property on the quenching of galaxies.

    Figure 1: Relative importance of supermassive black hole mass, black hole growth rate, mass of gas surrounding a galaxy, and mass of stars in a galaxy, on the probability of the galaxy being quenched, in the three simulations used. Adapted from Fig. 6 in today’s paper.

    It turns out that the most important factor in quenching a galaxy is the mass of the central supermassive black hole which powers an AGN: quenched galaxies contain much larger black holes than star-forming galaxies. Conversely, the rate at which the black hole mass is growing does not affect galaxy quenching. These black hole properties correspond to properties of an AGN: fast-growing black holes lead to bright, luminous AGN, while a black hole with a large mass tells us that it has had a high total AGN activity over its entire lifetime.

    The chequered pasts of AGN

    Previously, we might have expected that galaxies containing bright, powerful AGN would be quenched, as the AGN heat up their star-forming gas and expel it from the galaxy. The authors do indeed show that a period of intense AGN activity can result in both of these processes occurring. However, whether a galaxy is quenched depends instead on the total amount of AGN activity over its entire lifetime, not just its activity at the present day; Figure 2 clearly shows how quenched galaxies have greater supermassive black hole masses.

    Figure 2: Histogram showing masses of central supermassive black holes in star-forming and passive (i.e. quenched) galaxies in SDSS. Star-forming galaxies are shown by the solid blue line, passive galaxies by the dashed red line. Fig. 9 in today’s paper.

    This means that a period of AGN activity (corresponding to a rapid increase in supermassive black hole mass) will lead to a galaxy being quenched, irrespective of whether this burst of energy was recent, or a long time in the past. Not only that, but this activity is more important than any other galaxy properties in stopping the formation of new stars in a galaxy. This is a testament to the power of AGN: regardless of what a galaxy is experiencing now, a powerful AGN in its past can impact its star formation rate for billions of years to come. In the future, studies on the entire histories of AGN will hopefully shed even more light on the dramatic impact that they have on their host galaxies.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    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 9:38 pm on December 7, 2021 Permalink | Reply
    Tags: "VLA Reveals Double-Helix Structure in Massive Galaxy’s Jet", A jet of material propelled from the a giant galaxy is a channeled corkscrew-shaped magnetic field to nearly 3300 light-years from the galaxy’s supermassive black hole [Messier 87*] ., , , , Messier 87 is a giant elliptical galaxy about 55 million light-years from Earth., Messier 87* black hole, , ,   

    From The National Radio Astronomy Observatory (US) : “VLA Reveals Double-Helix Structure in Massive Galaxy’s Jet” 

    From The National Radio Astronomy Observatory (US)

    NRAO Banner

    Credit: Pasetto et al., Sophia Dagnello, NRAO/Associated Universities Inc(US)/The National Science Foundation (US).

    Astronomers using the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) have shown that a jet of material propelled from the core of a giant galaxy is channeled by a corkscrew-shaped magnetic field out to nearly 3300 light-years from the galaxy’s central supermassive black hole. That is much farther than such a magnetic field previously had been detected in a galactic jet.

    “By making high-quality VLA images at several different radio wavelengths of the galaxy Messier 87, we were able to reveal the 3-dimensional structure of the magnetic field in this jet for the first time,” said Alice Pasetto of The National Autonomous University of Mexico [Universidad Nacional Autónoma de México](MX), leader of the team. “The material in this jet traces a double helix similar to the structure of DNA,” she added.

    Messier 87 is a giant elliptical galaxy about 55 million light-years from Earth. A supermassive black hole some 6.5 billion times more massive than the Sun lurks at the center of Messier 87.

    Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via The Event Horizon Telescope Collaboration released on 10 April 2019 via National Science Foundation(US).

    That black hole is the first one ever to be imaged — an achievement done with the world-wide Event Horizon Telescope (EHT) collaboration and announced in 2019.

    EHT map.

    Earlier this year, new EHT images traced the magnetic field in the vicinity of the black hole event horizon.

    An image of the Messier 87 black hole, showing, for the first time, how it looks in polarized light. The lines mark the orientation of polarization, which is related to the magnetic field around the shadow of the black hole.Credit…Event Horizon Telescope Collaboration.

    Pasetto and her colleagues used the VLA to reveal details of the magnetic field by tracing the polarization, or alignment, of radio waves emitted from it, and by measuring the field’s strength across different parts of the jet. Their observations, made using the VLA’s widest configuration that provides the highest resolution, produced very detailed images of the galaxy’s jet.

    “Helical magnetic fields are expected close to the black hole, and are thought to play a highly important role in channeling the material into a narrow jet, but we didn’t expect to find such a strong helical field extending so far outward,” said Jose M. Marti, of The University of Valencia [Universitat de València [univeɾsiˈtad de vaˈlensia]](ES).

    The magnetic field is expected to weaken with its distance from the black hole. However, the scientists suggested that instabilities in the flow of material within the jet could make the magnetic field more ordered at the distances seen in the new VLA images. The instabilities produce regions of higher pressure which also compress the magnetic field lines.

    The astronomers think that this interaction between instabilities in the flow and the magnetic field is what produces the double-helix structure shown by the VLA images. If this is happening in the Messier 87* jet, it likely also is happening in similar jets from galaxies throughout the Universe, they said.

    “Messier 87* is relatively near to us and its jet is very powerful, making it an excellent target for study. The clues it gives us can help us understand this very important and ubiquitous phenomenon in the Universe,” said Jose L. Gomez, of The Instituto de Astrofísica de Andalucía – The The Spanish National Research Council [Consejo Superior de Investigaciones Científicas](ES).

    The scientists are reporting their findings in The Astrophysical Journal Letters.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition
    The National Radio Astronomy Observatory (NRAO)(US) is a Federally Funded Research and Development Center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc for the purpose of radio astronomy. NRAO designs, builds, and operates its own high sensitivity radio telescopes for use by scientists around the world.

    Charlottesville, Virginia(US)

    The National Radio Astronomy Observatory (US) headquarters is located on the campus of the University of Virginia (US). The North American ALMA Science Center (US) and the NRAO Technology Center and Central Development Laboratory are also in Charlottesville, Virginia.

    Green Bank, West Virginia (US)

    NRAO was, until October 2016, the operator of the world’s largest fully steerable radio telescope, the Robert C. Byrd Green Bank Telescope, which stands near Green Bank, West Virginia.

    Green Bank Radio Telescope, West Virginia, USA, now the center piece of the Green Bank Observatory(US), being cut loose by the National Science Foundation(US), supported by Breakthrough Listen Project.

    The observatory contains several other telescopes, among them the 140-foot (43 m) telescope that utilizes an equatorial mount uncommon for radio telescopes, three 85-foot (26 m) telescopes forming the Green Bank Interferometer, a 40-foot (12 m) telescope used by school groups and organizations for small scale research, a fixed radio “horn” built to observe the radio source Cassiopeia A, as well as a reproduction of the original antenna built by Karl Jansky while he worked for Bell Labs to detect the interference that was discovered to be previously unknown natural radio waves emitted by the universe.

    Green Bank is in the National Radio Quiet Zone, which is coordinated by NRAO for protection of the Green Bank site as well as the Sugar Grove, West Virginia monitoring site operated by the NSA. The zone consists of a 13,000-square-mile (34,000 km2) piece of land where fixed transmitters must coordinate their emissions before a license is granted. The land was set aside by the Federal Communications Commission in 1958. No fixed radio transmitters are allowed within the area closest to the telescope. All other fixed radio transmitters including TV and radio towers inside the zone are required to transmit such that interference at the antennas is minimized by methods including limited power and using highly directional antennas. With the advent of wireless technology and microprocessors in everything from cameras to cars, it is difficult to keep the sites free of radio interference. To aid in limiting outside interference, the area surrounding the Green Bank Observatory was at one time planted with pines characterized by needles of a certain length to block electromagnetic interference at the wavelengths used by the observatory. At one point, the observatory faced the problem of North American flying squirrels tagged with United States Fish and Wildlife Service telemetry transmitters. Electric fences, electric blankets, faulty automobile electronics, and other radio wave emitters have caused great trouble for the astronomers in Green Bank. All vehicles on the premises are powered by diesel motors to minimize interference by ignition systems.

    Socorro, New Mexico

    The NRAO’s facility in Socorro is the Pete Domenici Array Operations Center (AOC). Located on the New Mexico Technical University campus, the AOC serves as the headquarters for the NRAO Jansky Very Large Array (VLA), which was the setting for the 1997 movie Contact, and is also the control center for the NRAO Very Long Baseline Array (VLBA)(US). The ten VLBA telescopes are in Hawaii, the U.S. Virgin Islands, and eight other sites across the continental United States.

    National Radio Astronomy Observatory(US)Karl G Jansky Very Large Array located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes.

    ngVLA, to be located near the location of the NRAO Karl G. Jansky Very Large Array (US) site on the plains of San Agustin, fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m) with additional mid-baseline stations currently spread over greater New Mexico, Arizona, Texas, and Mexico.

    The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

    NRAO Very Long Baseline Array(US)-Very Long Baseline Array-USA

    San Pedro de Atacama, Chile

    The Atacama Large Millimeter Array (ALMA) site in Chile is at ~5000 m (~16,500 ft) altitude near Cerro Chajnantor in northern Chile. This is about 40 km (about 25 miles) east of the historic village of San Pedro de Atacama, 130 km (about 80 miles) southeast of the mining town of Calama, and about 275 km (about 170 miles) east-northeast of the coastal port of Antofagasta.

    [Observatoire européen austral][Europäische Südsternwarte] (EU)/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Observatory (CL)

    Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).

  • richardmitnick 11:53 am on April 15, 2021 Permalink | Reply
    Tags: "Dazzling dispatches from the heart of a galaxy", , Messier 87* black hole,   

    From Yale University (US) : “Dazzling dispatches from the heart of a galaxy” 

    From Yale University (US)

    April 14, 2021

    Fred Mamoun

    By Jim Shelton

    Credit: Event Horizon Telescope

    Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration released on 10 April 2019 Messier 87*, via National Science Foundation(US)


    Mislav Baloković, a postdoctoral fellow at the Yale Center for Astronomy and Astrophysics (US), has a prime viewing spot for the most famous black hole humans have ever seen.

    That would be the supermassive black hole in the galaxy Messier 87, located 55 million light years from Earth.

    Two years ago, the Event Horizon Telescope Collaboration (EHTC) — a global collaboration of astrophysicists and observatories that created a virtual, Earth-sized telescope, released an image of Messier 87*. It was the first photograph of a black hole and a technical achievement lauded by scientists around the world.

    Balcković, who came to Yale last fall, is a member of EHTC. He is a core contributor and co-author of a study published April 14 in The Astrophysical Journal Letters that sheds new light on the cosmic environment surrounding M87’s black hole.

    EHTC data will allow scientists to conduct new lines of investigation into some of the most challenging areas of astrophysics. For example, scientists will use the data to improve tests of Albert Einstein’s theory of general relativity. Currently, the main hurdles for these tests are uncertainties about the material rotating around a black hole and being blasted away from the black hole in jets that produce light spanning the entire electromagnetic spectrum, from radio waves to visible light to gamma rays.

    The new study also provides information about the origin of cosmic rays — energetic particles that continually bombard the Earth from space. The huge jets launched from black holes are thought to be the most likely source of the highest energy cosmic rays, but scientists have many questions about how this occurs.

    Baloković talked with YaleNews about the new findings and what they mean for further study of the universe.

    How do black holes influence our lives and the cosmos around us?

    Black holes reside at the heart of nearly every galaxy, including our own Milky Way. These “supermassive” black holes contain the combined mass of a million to a billion stars within a volume smaller than our solar system. Despite their relatively small size on the cosmic scale, supermassive black holes manage to influence the evolution of their entire host galaxy. Huge amounts of radiation are emitted from their immediate environment and they launch jets of fast-moving particles that can escape the galaxies’ boundaries. Though details of these processes are not well understood, we already have ample observational evidence that supermassive black holes play an important role in shaping galaxies over cosmic timescales.

    What, for you, are the most important findings from the new study?

    We assembled a dataset gathered from nearly all observable parts of the electromagnetic spectrum, matched in time to the now iconic image of the black hole in the galaxy Messier 87. Studying this dataset, we established that the emission pattern of the jet is structured so that low-energy emission mostly originates from the immediate surroundings of the black hole, while high-energy emission was predominantly generated farther out along the jet during the observations in 2017.

    This insight helps us to better understand how particles in the jet get accelerated to nearly the speed of light, producing some of the highest-energy cosmic rays that pervade deep space. It is also important that we defined a baseline for studies of changes in the following years and enabled more detailed comparisons of theoretical models to real data in the near future.

    What was your role in the research?

    I participated in the work of the core team leading the study and I coordinated consolidation of the data between teams of experts for each of 19 participating observatories. I specialize in observations in the X-ray portion of the electromagnetic spectrum, using NASA’s space-borne X-ray observatories NuSTAR, Chandra, and Swift.

    I also participated in observations performed in 2018 and in planning for the 2021 observing campaign that is going on at the moment. These additional observations will further improve the data quality and let us examine in detail how images and emission patterns change over time.

    How long have you been a member of the Event Horizon Telescope Collaboration and what is it like to be part of such a large team?

    I joined the EHTC after finishing my Ph.D. thesis in 2017, several months after the first observations were performed. I quickly met many new colleagues from all over the world and I remember how excited everyone was that the 2017 observing campaign was a success. Having even a small role in such a complex and ambitious undertaking can be very rewarding.

    Until recently, I worked as a coordinator of the group for communication with the public, having covered the world-wide announcement of the first black hole image in April 2019. I love the global character of the EHTC and the diversity of both culture and expertise that it contains — one learns something new in each group meeting. I firmly believe that the different perspectives collaboration members bring into our discussions make it possible to deliver scientific results that are both impactful and reliable.

    Do you remember your reaction when you saw the first image of a black hole?

    Naturally, it was very exciting to lay eyes on something so few have ever seen. This was during a workshop at Harvard, where I worked at the time, attended by many members of the EHTC. I remember thinking what a remarkable crowning achievement this result must be for my senior colleagues who steadily worked towards it for as long as two decades.

    It was also a relief that so much previous work on black holes was validated and strongly propelled forward. Many astronomical phenomena, starting with the discovery of the first quasar in 1963, have been explained assuming that supermassive black holes exist.

    How will this new information guide or inspire future research?

    The first image of the black hole in the galaxy Messier 87, and the more recent polarized image, are groundbreaking in their own right. However, in order to improve our understanding of the environment in which the black hole resides and further sharpen tests of the General Theory of Relativity, we needed to complement them with information uniquely available in other portions of the electromagnetic spectrum.

    The newly published dataset will enable many research groups around the world to test whether their theoretical models can reproduce the pattern of emission from M87 at the time the iconic image was taken. Complex theoretical models based on our cutting-edge understanding of black hole environments will help us gain new insight into how supermassive black holes launch jets of fast-moving particles into the galaxies that surround them, consequently influencing their evolution.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Yale University comprises three major academic components: Yale College (the undergraduate program); the Graduate School of Arts and Sciences; and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

    Yale University (US) is a private Ivy League research university in New Haven, Connecticut. Founded in 1701 as the Collegiate School, it is the third-oldest institution of higher education in the United States and one of the nine Colonial Colleges chartered before the American Revolution. Collegiate School was renamed Yale College in 1718 to honor the school’s largest benefactor, Elihu Yale.

    Chartered by Connecticut Colony, the Collegiate School was established in 1701 by clergy to educate Congregational ministers. It moved to New Haven in 1716 and shortly after was renamed Yale College in recognition of a gift from East India Company governor Elihu Yale. Originally restricted to theology and sacred languages, the curriculum began to incorporate humanities and sciences by the time of the American Revolution. In the 19th century, the college expanded into graduate and professional instruction, awarding the first PhD in the United States in 1861 and organizing as a university in 1887. Yale’s faculty and student populations grew after 1890 with rapid expansion of the physical campus and scientific research.

    Yale is organized into fourteen constituent schools: the original undergraduate college; the Yale Graduate School of Arts and Sciences; and twelve professional schools. While the university is governed by the Yale Corporation, each school’s faculty oversees its curriculum and degree programs. In addition to a central campus in downtown New Haven, the university owns athletic facilities in western New Haven, a campus in West Haven, Connecticut, and forests and nature preserves throughout New England. As of September 2019, the university’s assets include an endowment valued at $30.3 billion, the second largest endowment of any educational institution in North America. The Yale University Library, serving all constituent schools, holds more than 15 million volumes and is the third-largest academic library in the United States. Students compete in intercollegiate sports as the Yale Bulldogs in the NCAA Division I – Ivy League.

    As of October 2020, 65 Nobel laureates, five Fields Medalists and three Turing award winners have been affiliated with Yale University. In addition, Yale has graduated many notable alumni, including five U.S. Presidents; 19 U.S. Supreme Court Justices; 31 living billionaires; and many heads of state. Hundreds of members of Congress and many U.S. diplomats; 78 MacArthur Fellows; 252 Rhodes Scholars; 123 Marshall Scholars; and nine Mitchell Scholars have been affiliated with the university.

    Yale traces its beginnings to “An Act for Liberty to Erect a Collegiate School”, a would-be charter passed during a meeting in New Haven by the General Court of the Colony of Connecticut on October 9, 1701. The Act was an effort to create an institution to train ministers and lay leadership for Connecticut. Soon after, a group of ten Congregational ministers, Samuel Andrew; Thomas Buckingham; Israel Chauncy; Samuel Mather (nephew of Increase Mather); Rev. James Noyes II (son of James Noyes); James Pierpont; Abraham Pierson; Noadiah Russell; Joseph Webb; and Timothy Woodbridge, all alumni of Harvard University(US), met in the study of Reverend Samuel Russell located in Branford, Connecticut to donate their books to form the school’s library. The group, led by James Pierpont, is now known as “The Founders”.

    Originally known as the “Collegiate School”, the institution opened in the home of its first rector, Abraham Pierson, who is today considered the first president of Yale. Pierson lived in Killingworth (now Clinton). The school moved to Saybrook and then Wethersfield. In 1716, it moved to New Haven, Connecticut.

    Meanwhile, there was a rift forming at Harvard between its sixth president, Increase Mather, and the rest of the Harvard clergy, whom Mather viewed as increasingly liberal, ecclesiastically lax, and overly broad in Church polity. The feud caused the Mathers to champion the success of the Collegiate School in the hope that it would maintain the Puritan religious orthodoxy in a way that Harvard had not.

    Naming and development

    Coat of arms of the family of Elihu Yale, after whom the university was named in 1718

    In 1718, at the behest of either Rector Samuel Andrew or the colony’s Governor Gurdon Saltonstall, Cotton Mather contacted the successful Boston born businessman Elihu Yale to ask him for financial help in constructing a new building for the college. Through the persuasion of Jeremiah Dummer, Elihu “Eli” Yale, who had made a fortune in Madras while working for the East India Company overseeing its slave trading activities, donated nine bales of goods, which were sold for more than £560, a substantial sum of money at the time. Cotton Mather suggested that the school change its name to “Yale College.” The name Yale is the Anglicized spelling of the Iâl, which the family estate at Plas yn Iâl, near the village of Llandegla, was called.

    Meanwhile, a Harvard graduate working in England convinced some 180 prominent intellectuals to donate books to Yale. The 1714 shipment of 500 books represented the best of modern English literature; science; philosophy; and theology at the time. It had a profound effect on intellectuals at Yale. Undergraduate Jonathan Edwards discovered John Locke’s works and developed his original theology known as the “new divinity.” In 1722 the Rector and six of his friends, who had a study group to discuss the new ideas, announced that they had given up Calvinism, become Arminians, and joined the Church of England. They were ordained in England and returned to the colonies as missionaries for the Anglican faith. Thomas Clapp became president in 1745 and while he attempted to return the college to Calvinist orthodoxy, he did not close the library. Other students found Deist books in the library.


    Yale College undergraduates follow a liberal arts curriculum with departmental majors and is organized into a social system of residential colleges.

    Yale was swept up by the great intellectual movements of the period—the Great Awakening and the Enlightenment—due to the religious and scientific interests of presidents Thomas Clap and Ezra Stiles. They were both instrumental in developing the scientific curriculum at Yale while dealing with wars, student tumults, graffiti, “irrelevance” of curricula, desperate need for endowment and disagreements with the Connecticut legislature.

    Serious American students of theology and divinity particularly in New England regarded Hebrew as a classical language along with Greek and Latin and essential for the study of the Hebrew Bible in the original words. The Reverend Ezra Stiles, president of the college from 1778 to 1795, brought with him his interest in the Hebrew language as a vehicle for studying ancient Biblical texts in their original language (as was common in other schools) requiring all freshmen to study Hebrew (in contrast to Harvard, where only upperclassmen were required to study the language) and is responsible for the Hebrew phrase אורים ותמים (Urim and Thummim) on the Yale seal. A 1746 graduate of Yale, Stiles came to the college with experience in education, having played an integral role in the founding of Brown University(US), in addition to having been a minister. Stiles’ greatest challenge occurred in July 1779 when British forces occupied New Haven and threatened to raze the college. However, Yale graduate Edmund Fanning, Secretary to the British General in command of the occupation, intervened and the college was saved. In 1803, Fanning was granted an honorary degree LL.D. for his efforts.


    As the only college in Connecticut from 1701 to 1823, Yale educated the sons of the elite. Punishable offenses for students included cardplaying; tavern-going; destruction of college property; and acts of disobedience to college authorities. During this period, Harvard was distinctive for the stability and maturity of its tutor corps, while Yale had youth and zeal on its side.

    The emphasis on classics gave rise to a number of private student societies, open only by invitation, which arose primarily as forums for discussions of modern scholarship literature and politics. The first such organizations were debating societies: Crotonia in 1738, Linonia in 1753 and Brothers in Unity in 1768. While the societies no longer exist, commemorations to them can be found with names given to campus structures, like Brothers in Unity Courtyard in Branford College.

    19th century

    The Yale Report of 1828 was a dogmatic defense of the Latin and Greek curriculum against critics who wanted more courses in modern languages, mathematics, and science. Unlike higher education in Europe, there was no national curriculum for colleges and universities in the United States. In the competition for students and financial support, college leaders strove to keep current with demands for innovation. At the same time, they realized that a significant portion of their students and prospective students demanded a classical background. The Yale report meant the classics would not be abandoned. During this period, all institutions experimented with changes in the curriculum, often resulting in a dual-track curriculum. In the decentralized environment of higher education in the United States, balancing change with tradition was a common challenge because it was difficult for an institution to be completely modern or completely classical. A group of professors at Yale and New Haven Congregationalist ministers articulated a conservative response to the changes brought about by the Victorian culture. They concentrated on developing a person possessed of religious values strong enough to sufficiently resist temptations from within yet flexible enough to adjust to the ‘isms’ (professionalism; materialism; individualism; and consumerism) tempting him from without. William Graham Sumner, professor from 1872 to 1909, taught in the emerging disciplines of economics and sociology to overflowing classrooms of students. Sumner bested President Noah Porter, who disliked the social sciences and wanted Yale to lock into its traditions of classical education. Porter objected to Sumner’s use of a textbook by Herbert Spencer that espoused agnostic materialism because it might harm students.

    Until 1887, the legal name of the university was “The President and Fellows of Yale College, in New Haven.” In 1887, under an act passed by the Connecticut General Assembly, Yale was renamed to the present “Yale University.”

    Sports and debate

    The Revolutionary War soldier Nathan Hale (Yale 1773) was the prototype of the Yale ideal in the early 19th century: a manly yet aristocratic scholar, equally well-versed in knowledge and sports, and a patriot who “regretted” that he “had but one life to lose” for his country. Western painter Frederic Remington (Yale 1900) was an artist whose heroes gloried in combat and tests of strength in the Wild West. The fictional, turn-of-the-20th-century Yale man Frank Merriwell embodied the heroic ideal without racial prejudice, and his fictional successor Frank Stover in the novel Stover at Yale (1911) questioned the business mentality that had become prevalent at the school. Increasingly the students turned to athletic stars as their heroes, especially since winning the big game became the goal of the student body, and the alumni, as well as the team itself.

    Along with Harvard and Princeton University(US), Yale students rejected British concepts about ‘amateurism’ in sports and constructed athletic programs that were uniquely American, such as football. The Harvard–Yale football rivalry began in 1875. Between 1892, when Harvard and Yale met in one of the first intercollegiate debates and 1909 (the year of the first Triangular Debate of Harvard, Yale and Princeton) the rhetoric, symbolism, and metaphors used in athletics were used to frame these early debates. Debates were covered on front pages of college newspapers and emphasized in yearbooks, and team members even received the equivalent of athletic letters for their jackets. There even were rallies sending off the debating teams to matches, but the debates never attained the broad appeal that athletics enjoyed. One reason may be that debates do not have a clear winner, as is the case in sports, and that scoring is subjective. In addition, with late 19th-century concerns about the impact of modern life on the human body, athletics offered hope that neither the individual nor the society was coming apart.

    In 1909–10, football faced a crisis resulting from the failure of the previous reforms of 1905–06 to solve the problem of serious injuries. There was a mood of alarm and mistrust, and, while the crisis was developing, the presidents of Harvard, Yale, and Princeton developed a project to reform the sport and forestall possible radical changes forced by government upon the sport. President Arthur Hadley of Yale, A. Lawrence Lowell of Harvard, and Woodrow Wilson of Princeton worked to develop moderate changes to reduce injuries. Their attempts, however, were reduced by rebellion against the rules committee and formation of the Intercollegiate Athletic Association. The big three had tried to operate independently of the majority, but changes did reduce injuries.


    Yale expanded gradually, establishing the Yale School of Medicine (1810); Yale Divinity School (1822); Yale Law School (1843); Yale Graduate School of Arts and Sciences (1847); the Sheffield Scientific School (1847); and the Yale School of Fine Arts (1869). In 1887, as the college continued to grow under the presidency of Timothy Dwight V, Yale College was renamed Yale University, with the name Yale College subsequently applied to the undergraduate college. The university would later add the Yale School of Music (1894); the Yale School of Forestry & Environmental Studies (founded by Gifford Pinchot in 1900); the Yale School of Public Health (1915); the Yale School of Nursing (1923); the Yale School of Drama (1955); the Yale Physician Associate Program (1973); the Yale School of Management (1976); and the Jackson School of Global Affairs which will open in 2022. It would also reorganize its relationship with the Sheffield Scientific School.

    Expansion caused controversy about Yale’s new roles. Noah Porter, moral philosopher, was president from 1871 to 1886. During an age of tremendous expansion in higher education, Porter resisted the rise of the new research university, claiming that an eager embrace of its ideals would corrupt undergraduate education. Many of Porter’s contemporaries criticized his administration, and historians since have disparaged his leadership. Levesque argues Porter was not a simple-minded reactionary, uncritically committed to tradition, but a principled and selective conservative. He did not endorse everything old or reject everything new; rather, he sought to apply long-established ethical and pedagogical principles to a rapidly changing culture. He may have misunderstood some of the challenges of his time, but he correctly anticipated the enduring tensions that have accompanied the emergence and growth of the modern university.

    20th century

    Behavioral sciences

    Between 1925 and 1940, philanthropic foundations, especially ones connected with the Rockefellers, contributed about $7 million to support the Yale Institute of Human Relations and the affiliated Yerkes Laboratories of Primate Biology. The money went toward behavioral science research, which was supported by foundation officers who aimed to “improve mankind” under an informal, loosely defined human engineering effort. The behavioral scientists at Yale, led by President James R. Angell and psychobiologist Robert M. Yerkes, tapped into foundation largesse by crafting research programs aimed to investigate, then suggest, ways to control sexual and social behavior. For example, Yerkes analyzed chimpanzee sexual behavior in hopes of illuminating the evolutionary underpinnings of human development and providing information that could ameliorate dysfunction. Ultimately, the behavioral-science results disappointed foundation officers, who shifted their human-engineering funds toward biological sciences.


    Slack (2003) compares three groups that conducted biological research at Yale during overlapping periods between 1910 and 1970. Yale proved important as a site for this research. The leaders of these groups were Ross Granville Harrison; Grace E. Pickford; and G. Evelyn Hutchinson and their members included both graduate students and more experienced scientists. All produced innovative research, including the opening of new subfields in embryology; endocrinology; and ecology, respectively, over a long period of time. Harrison’s group is shown to have been a classic research school. Pickford’s and Hutchinson’s were not. Pickford’s group was successful in spite of her lack of departmental or institutional position or power. Hutchinson and his graduate and postgraduate students were extremely productive, but in diverse areas of ecology rather than one focused area of research or the use of one set of research tools. Hutchinson’s example shows that new models for research groups are needed, especially for those that include extensive field research.


    Milton Winternitz led the Yale School of Medicine as its dean from 1920 to 1935. Dedicated to the new scientific medicine established in Germany, he was equally fervent about “social medicine” and the study of humans in their culture and environment. He established the “Yale System” of teaching, with few lectures and fewer exams, and strengthened the full-time faculty system. He also created the graduate-level Yale School of Nursing and the Psychiatry Department and built numerous new buildings. Progress toward his plans for an Institute of Human Relations, envisioned as a refuge where social scientists would collaborate with biological scientists in a holistic study of humankind, unfortunately, lasted for only a few years before the opposition of resentful anti-Semitic colleagues drove him to resign.

    Before World War II, most elite university faculties counted among their numbers few, if any, Jews, blacks, women, or other minorities. Yale was no exception. By 1980, this condition had been altered dramatically, as numerous members of those groups held faculty positions. Almost all members of the Faculty of Arts and Sciences—and some members of other faculties—teach undergraduate courses, more than 2,000 of which are offered annually.

    History and American studies

    The American studies program reflected the worldwide anti-Communist ideological struggle. Norman Holmes Pearson, who worked for the Office of Strategic Studies in London during World War II, returned to Yale and headed the new American studies program. Popular among undergraduates, the program sought to instill a sense of nationalism and national purpose. Also during the 1940s and 1950s, Wyoming millionaire William Robertson Coe made large contributions to the American studies programs at Yale University and at the University of Wyoming. Coe was concerned to celebrate the ‘values’ of the Western United States in order to meet the “threat of communism”.


    In 1793, Lucinda Foote passed the entrance exams for Yale College, but was rejected by the President on the basis of her gender. Women studied at Yale University as early as 1892, in graduate-level programs at the Yale Graduate School of Arts and Sciences.

    In 1966, Yale began discussions with its sister school Vassar College(US) about merging to foster coeducation at the undergraduate level. Vassar, then all-female and part of the Seven Sisters—elite higher education schools that historically served as sister institutions to the Ivy League when most Ivy League institutions still only admitted men—tentatively accepted, but then declined the invitation. Both schools introduced coeducation independently in 1969. Amy Solomon was the first woman to register as a Yale undergraduate; she was also the first woman at Yale to join an undergraduate society, St. Anthony Hall. The undergraduate class of 1973 was the first class to have women starting from freshman year; at the time, all undergraduate women were housed in Vanderbilt Hall at the south end of Old Campus.

    A decade into co-education, student assault and harassment by faculty became the impetus for the trailblazing lawsuit Alexander v. Yale. In the late 1970s, a group of students and one faculty member sued Yale for its failure to curtail campus sexual harassment by especially male faculty. The case was party built from a 1977 report authored by plaintiff Ann Olivarius, now a feminist attorney known for fighting sexual harassment, A report to the Yale Corporation from the Yale Undergraduate Women’s Caucus. This case was the first to use Title IX to argue and establish that the sexual harassment of female students can be considered illegal sex discrimination. The plaintiffs in the case were Olivarius, Ronni Alexander (now a professor at Kobe University[神戸大学; Kōbe daigaku](JP)); Margery Reifler (works in the Los Angeles film industry), Pamela Price (civil rights attorney in California), and Lisa E. Stone (works at Anti-Defamation League). They were joined by Yale classics professor John “Jack” J. Winkler, who died in 1990. The lawsuit, brought partly by Catharine MacKinnon, alleged rape, fondling, and offers of higher grades for sex by several Yale faculty, including Keith Brion professor of flute and Director of Bands; Political Science professor Raymond Duvall (now at the University of Minnesota(US)); English professor Michael Cooke and coach of the field hockey team, Richard Kentwell. While unsuccessful in the courts, the legal reasoning behind the case changed the landscape of sex discrimination law and resulted in the establishment of Yale’s Grievance Board and the Yale Women’s Center. In March 2011 a Title IX complaint was filed against Yale by students and recent graduates, including editors of Yale’s feminist magazine Broad Recognition, alleging that the university had a hostile sexual climate. In response, the university formed a Title IX steering committee to address complaints of sexual misconduct. Afterwards, universities and colleges throughout the US also established sexual harassment grievance procedures.


    Yale, like other Ivy League schools, instituted policies in the early 20th century designed to maintain the proportion of white Protestants from notable families in the student body, and was one of the last of the Ivies to eliminate such preferences, beginning with the class of 1970.

    Town–gown relations

    Yale has a complicated relationship with its home city; for example, thousands of students volunteer every year in a myriad of community organizations, but city officials, who decry Yale’s exemption from local property taxes, have long pressed the university to do more to help. Under President Levin, Yale has financially supported many of New Haven’s efforts to reinvigorate the city. Evidence suggests that the town and gown relationships are mutually beneficial. Still, the economic power of the university increased dramatically with its financial success amid a decline in the local economy.

    21st century

    In 2006, Yale and Peking University [北京大学](CN) established a Joint Undergraduate Program in Beijing, an exchange program allowing Yale students to spend a semester living and studying with PKU honor students. In July 2012, the Yale University-PKU Program ended due to weak participation.

    In 2007 outgoing Yale President Rick Levin characterized Yale’s institutional priorities: “First, among the nation’s finest research universities, Yale is distinctively committed to excellence in undergraduate education. Second, in our graduate and professional schools, as well as in Yale College, we are committed to the education of leaders.”

    In 2009, former British Prime Minister Tony Blair picked Yale as one location – the others are Britain’s Durham University(UK) and Universiti Teknologi Mara (MY) – for the Tony Blair Faith Foundation’s United States Faith and Globalization Initiative. As of 2009, former Mexican President Ernesto Zedillo is the director of the Yale Center for the Study of Globalization and teaches an undergraduate seminar, Debating Globalization. As of 2009, former presidential candidate and DNC chair Howard Dean teaches a residential college seminar, Understanding Politics and Politicians. Also in 2009, an alliance was formed among Yale, University College London(UK), and both schools’ affiliated hospital complexes to conduct research focused on the direct improvement of patient care—a growing field known as translational medicine. President Richard Levin noted that Yale has hundreds of other partnerships across the world, but “no existing collaboration matches the scale of the new partnership with UCL”.

    In August 2013, a new partnership with the National University of Singapore(SG) led to the opening of Yale-NUS College in Singapore, a joint effort to create a new liberal arts college in Asia featuring a curriculum including both Western and Asian traditions.

    In 2020, in the wake of protests around the world focused on racial relations and criminal justice reform, the #CancelYale movement demanded that Elihu Yale’s name be removed from Yale University. Yale was president of the East India Company, a trading company that traded slaves as well as goods, and his singularly large donation led to Yale relying on money from the slave-trade for its first scholarships and endowments.

    In August 2020, the US Justice Department claimed that Yale discriminated against Asian and white candidates on the basis of their race. The university, however, denied the report. In early February 2021, under the new Biden administration, the Justice Department withdrew the lawsuit. The group, Students for Fair Admissions, known for a similar lawsuit against Harvard alleging the same issue, plans to refile the lawsuit.

    Yale alumni in Politics

    The Boston Globe wrote that “if there’s one school that can lay claim to educating the nation’s top national leaders over the past three decades, it’s Yale”. Yale alumni were represented on the Democratic or Republican ticket in every U.S. presidential election between 1972 and 2004. Yale-educated Presidents since the end of the Vietnam War include Gerald Ford; George H.W. Bush; Bill Clinton; and George W. Bush. Major-party nominees during this period include Hillary Clinton (2016); John Kerry (2004); Joseph Lieberman (Vice President, 2000); and Sargent Shriver (Vice President, 1972). Other Yale alumni who have made serious bids for the Presidency during this period include Amy Klobuchar (2020); Tom Steyer (2020); Ben Carson (2016); Howard Dean (2004); Gary Hart (1984 and 1988); Paul Tsongas (1992); Pat Robertson (1988); and Jerry Brown (1976, 1980, 1992).

    Several explanations have been offered for Yale’s representation in national elections since the end of the Vietnam War. Various sources note the spirit of campus activism that has existed at Yale since the 1960s, and the intellectual influence of Reverend William Sloane Coffin on many of the future candidates. Yale President Richard Levin attributes the run to Yale’s focus on creating “a laboratory for future leaders,” an institutional priority that began during the tenure of Yale Presidents Alfred Whitney Griswold and Kingman Brewster. Richard H. Brodhead, former dean of Yale College and now president of Duke University(US), stated: “We do give very significant attention to orientation to the community in our admissions, and there is a very strong tradition of volunteerism at Yale.” Yale historian Gaddis Smith notes “an ethos of organized activity” at Yale during the 20th century that led John Kerry to lead the Yale Political Union’s Liberal Party; George Pataki the Conservative Party; and Joseph Lieberman to manage the Yale Daily News. Camille Paglia points to a history of networking and elitism: “It has to do with a web of friendships and affiliations built up in school.” CNN suggests that George W. Bush benefited from preferential admissions policies for the “son and grandson of alumni”, and for a “member of a politically influential family”. New York Times correspondent Elisabeth Bumiller and The Atlantic Monthly correspondent James Fallows credit the culture of community and cooperation that exists between students, faculty, and administration, which downplays self-interest and reinforces commitment to others.

    During the 1988 presidential election, George H. W. Bush (Yale ’48) derided Michael Dukakis for having “foreign-policy views born in Harvard Yard’s boutique”. When challenged on the distinction between Dukakis’ Harvard connection and his own Yale background, he said that, unlike Harvard, Yale’s reputation was “so diffuse, there isn’t a symbol, I don’t think, in the Yale situation, any symbolism in it” and said Yale did not share Harvard’s reputation for “liberalism and elitism”. In 2004 Howard Dean stated, “In some ways, I consider myself separate from the other three (Yale) candidates of 2004. Yale changed so much between the class of ’68 and the class of ’71. My class was the first class to have women in it; it was the first class to have a significant effort to recruit African Americans. It was an extraordinary time, and in that span of time is the change of an entire generation”.


    The President and Fellows of Yale College, also known as the Yale Corporation, or board of trustees, is the governing body of the university and consists of thirteen standing committees with separate responsibilities outlined in the by-laws. The corporation has 19 members: three ex officio members, ten successor trustees, and six elected alumni fellows.

    Yale’s former president Richard C. Levin was, at the time, one of the highest paid university presidents in the United States. Yale’s succeeding president Peter Salovey ranks 40th.

    The Yale Provost’s Office and similar executive positions have launched several women into prominent university executive positions. In 1977, Provost Hanna Holborn Gray was appointed interim President of Yale and later went on to become President of the University of Chicago(US), being the first woman to hold either position at each respective school. In 1994, Provost Judith Rodin became the first permanent female president of an Ivy League institution at the University of Pennsylvania(US). In 2002, Provost Alison Richard became the Vice-Chancellor of the University of Cambridge(UK). In 2003, the Dean of the Divinity School, Rebecca Chopp, was appointed president of Colgate University(US) and later went on to serve as the President of the Swarthmore College(US) in 2009, and then the first female chancellor of the University of Denver(US) in 2014. In 2004, Provost Dr. Susan Hockfield became the President of the Massachusetts Institute of Technology. In 2004, Dean of the Nursing school, Catherine Gilliss, was appointed the Dean of Duke University’s School of Nursing and Vice Chancellor for Nursing Affairs. In 2007, Deputy Provost H. Kim Bottomly was named President of Wellesley College(US).

    Similar examples for men who’ve served in Yale leadership positions can also be found. In 2004, Dean of Yale College Richard H. Brodhead was appointed as the President of Duke University(US). In 2008, Provost Andrew Hamilton was confirmed to be the Vice Chancellor of the University of Oxford(UK).

    The university has three major academic components: Yale College (the undergraduate program); the Graduate School of Arts and Sciences; and the professional schools.


    Yale’s central campus in downtown New Haven covers 260 acres (1.1 km2) and comprises its main, historic campus and a medical campus adjacent to the Yale–New Haven Hospital. In western New Haven, the university holds 500 acres (2.0 km2) of athletic facilities, including the Yale Golf Course. In 2008, Yale purchased the 17-building, 136-acre (0.55 km2) former Bayer HealthCare complex in West Haven, Connecticut, the buildings of which are now used as laboratory and research space. Yale also owns seven forests in Connecticut, Vermont, and New Hampshire—the largest of which is the 7,840-acre (31.7 km2) Yale-Myers Forest in Connecticut’s Quiet Corner—and nature preserves including Horse Island.

    Yale is noted for its largely Collegiate Gothic campus as well as several iconic modern buildings commonly discussed in architectural history survey courses: Louis Kahn’s Yale Art Gallery and Center for British Art; Eero Saarinen’s Ingalls Rink and Ezra Stiles and Morse Colleges; and Paul Rudolph’s Art & Architecture Building. Yale also owns and has restored many noteworthy 19th-century mansions along Hillhouse Avenue, which was considered the most beautiful street in America by Charles Dickens when he visited the United States in the 1840s. In 2011, Travel+Leisure listed the Yale campus as one of the most beautiful in the United States.

    Many of Yale’s buildings were constructed in the Collegiate Gothic architecture style from 1917 to 1931, financed largely by Edward S. Harkness, including the Yale Drama School. Stone sculpture built into the walls of the buildings portray contemporary college personalities, such as a writer; an athlete; a tea-drinking socialite; and a student who has fallen asleep while reading. Similarly, the decorative friezes on the buildings depict contemporary scenes, like a policemen chasing a robber and arresting a prostitute (on the wall of the Law School) or a student relaxing with a mug of beer and a cigarette. The architect, James Gamble Rogers, faux-aged these buildings by splashing the walls with acid, deliberately breaking their leaded glass windows and repairing them in the style of the Middle Ages and creating niches for decorative statuary but leaving them empty to simulate loss or theft over the ages. In fact, the buildings merely simulate Middle Ages architecture, for though they appear to be constructed of solid stone blocks in the authentic manner, most actually have steel framing as was commonly used in 1930. One exception is Harkness Tower, 216 feet (66 m) tall, which was originally a free-standing stone structure. It was reinforced in 1964 to allow the installation of the Yale Memorial Carillon.

    Other examples of the Gothic style are on the Old Campus by architects like Henry Austin; Charles C. Haight; and Russell Sturgis. Several are associated with members of the Vanderbilt family, including Vanderbilt Hall; Phelps Hall; St. Anthony Hall (a commission for member Frederick William Vanderbilt); the Mason, Sloane and Osborn laboratories; dormitories for the Sheffield Scientific School (the engineering and sciences school at Yale until 1956) and elements of Silliman College, the largest residential college.

    The oldest building on campus, Connecticut Hall (built in 1750), is in the Georgian style. Georgian-style buildings erected from 1929 to 1933 include Timothy Dwight College, Pierson College, and Davenport College, except the latter’s east, York Street façade, which was constructed in the Gothic style to coordinate with adjacent structures.

    Interior of Beinecke Library

    The Beinecke Rare Book and Manuscript Library, designed by Gordon Bunshaft of Skidmore, Owings & Merrill, is one of the largest buildings in the world reserved exclusively for the preservation of rare books and manuscripts. The library includes a six-story above-ground tower of book stacks, filled with 180,000 volumes, that is surrounded by large translucent Vermont marble panels and a steel and granite truss. The panels act as windows and subdue direct sunlight while also diffusing the light in warm hues throughout the interior. Near the library is a sunken courtyard, with sculptures by Isamu Noguchi that are said to represent time (the pyramid), the sun (the circle), and chance (the cube). The library is located near the center of the university in Hewitt Quadrangle, which is now more commonly referred to as “Beinecke Plaza.”

    Alumnus Eero Saarinen, Finnish-American architect of such notable structures as the Gateway Arch in St. Louis; Washington Dulles International Airport main terminal; Bell Labs Holmdel Complex; and the CBS Building in Manhattan, designed Ingalls Rink, dedicated in 1959, as well as the residential colleges Ezra Stiles and Morse. These latter were modeled after the medieval Italian hill town of San Gimignano – a prototype chosen for the town’s pedestrian-friendly milieu and fortress-like stone towers. These tower forms at Yale act in counterpoint to the college’s many Gothic spires and Georgian cupolas.

    Yale’s Office of Sustainability develops and implements sustainability practices at Yale. Yale is committed to reduce its greenhouse gas emissions 10% below 1990 levels by the year 2020. As part of this commitment, the university allocates renewable energy credits to offset some of the energy used by residential colleges. Eleven campus buildings are candidates for LEED design and certification. Yale Sustainable Food Project initiated the introduction of local organic vegetables fruits and beef to all residential college dining halls. Yale was listed as a Campus Sustainability Leader on the Sustainable Endowments Institute’s College Sustainability Report Card 2008, and received a “B+” grade overall.

    Notable nonresidential campus buildings

    Notable nonresidential campus buildings and landmarks include Battell Chapel; Beinecke Rare Book Library; Harkness Tower; Ingalls Rink; Kline Biology Tower; Osborne Memorial Laboratories; Payne Whitney Gymnasium; Peabody Museum of Natural History; Sterling Hall of Medicine; Sterling Law Buildings; Sterling Memorial Library; Woolsey Hall; Yale Center for British Art; Yale University Art Gallery; Yale Art & Architecture Building and the Paul Mellon Centre for Studies in British Art in London.

    Yale’s secret society buildings (some of which are called “tombs”) were built both to be private yet unmistakable. A diversity of architectural styles is represented: Berzelius; Donn Barber in an austere cube with classical detailing (erected in 1908 or 1910); Book and Snake; Louis R. Metcalfe in a Greek Ionic style (erected in 1901); Elihu, architect unknown but built in a Colonial style (constructed on an early 17th-century foundation although the building is from the 18th century); Mace and Chain, in a late colonial early Victorian style (built in 1823). (Interior moulding is said to have belonged to Benedict Arnold); Manuscript Society, King Lui-Wu with Dan Kniley responsible for landscaping and Josef Albers for the brickwork intaglio mural. Buildings constructed in a mid-century modern style: Scroll and Key; Richard Morris Hunt in a Moorish- or Islamic-inspired Beaux-Arts style (erected 1869–70); Skull and Bones; possibly Alexander Jackson Davis or Henry Austin in an Egypto-Doric style utilizing Brownstone (in 1856 the first wing was completed, in 1903 the second wing, 1911 the Neo-Gothic towers in rear garden were completed); St. Elmo, (former tomb) Kenneth M. Murchison, 1912, designs inspired by Elizabethan manor. Current location, brick colonial; and Wolf’s Head, Bertram Grosvenor Goodhue, erected 1923–1924, Collegiate Gothic.

    Relationship with New Haven

    Yale is the largest taxpayer and employer in the City of New Haven, and has often buoyed the city’s economy and communities. Yale, however has consistently opposed paying a tax on its academic property. Yale’s Art Galleries, along with many other university resources, are free and openly accessible. Yale also funds the New Haven Promise program, paying full tuition for eligible students from New Haven public schools.

  • richardmitnick 4:46 pm on January 7, 2021 Permalink | Reply
    Tags: "After decades of effort scientists are finally seeing black holes—or are they?, , , , , Messier 87* black hole, , Richard Genzel-MPE,   

    From Science Magazine: “After decades of effort scientists are finally seeing black holes—or are they? 

    From Science Magazine

    Jan. 7, 2021
    Adrian Cho

    General relativity makes very specific predictions about what black holes are and how they should appear, as shown in this simulation. Credit: GODDARD SPACE FLIGHT CENTER/JEREMY SCHNITTMAN.

    While working on his doctorate in theoretical physics in the early 1970s, Saul Teukolsky solved a problem that seemed purely hypothetical. Imagine a black hole, the ghostly knot of gravity that forms when, say, a massive star burns out and collapses to an infinitesimal point. Suppose you perturb it, as you might strike a bell. How does the black hole respond?

    Teukolsky, then a graduate student at the California Institute of Technology (Caltech), attacked the problem with pencil, paper, and Albert Einstein’s theory of gravity, general relativity. Like a bell, the black hole would oscillate at one main frequency and multiple overtones, he found. The oscillations would quickly fade as the black hole radiated gravitational waves—ripples in the fabric of space itself. It was a sweet problem, says Teukolsky, now at Cornell University. And it was completely abstract—until 5 years ago.

    In February 2016, experimenters with the Laser Interferometer Gravitational-Wave Observatory (LIGO), a pair of huge instruments in Louisiana and Washington, reported the first observation of fleeting gravitational ripples, which had emanated from two black holes, each about 30 times as massive as the Sun, spiraling into each other 1.3 billion light-years away.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    LIGO even sensed the “ring down”: the shudder of the bigger black hole produced by the merger. Teukolsky’s old thesis was suddenly cutting-edge physics.

    The thought that anything I did would ever have implications for anything measurable in my lifetime was so far-fetched that the last 5 years have seemed like living in a dream world,” Teukolsky says. “I have to pinch myself, it doesn’t feel real.”

    Fantastical though it may seem, scientists can now study black holes as real objects. Gravitational wave detectors have spotted four dozen black hole mergers since LIGO’s breakthrough detection. In April 2019, an international collaboration called the Event Horizon Telescope (EHT) produced the first image of a black hole. By training radio telescopes around the globe on the supermassive black hole in the heart of the nearby galaxy Messier 87 (M87), EHT imaged a fiery ring of hot gas surrounding the black hole’s inky “shadow.”

    Messier 87*, The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration released on 10 April 2019.

    EHT map.

    Meanwhile, astronomers are tracking stars that zip close to the black hole in the center of our own Galaxy, following paths that may hold clues to the nature of the black hole itself.

    The observations are already challenging astrophysicists’ assumptions about how black holes form and influence their surroundings. The smaller black holes detected by LIGO and, now, the European gravitational wave detector Virgo in Italy have proved heavier and more varied than expected, straining astrophysicists’ understanding of the massive stars from which they presumably form. And the environment around the supermassive black hole in our Galaxy appears surprisingly fertile, teeming with young stars not expected to form in such a maelstrom. But some scientists feel the pull of a more fundamental question: Are they really seeing the black holes predicted by Einstein’s theory?

    Some theorists say the answer is most likely a ho-hum yes. “I don’t think we’re going to learn anything more about general relativity or the theory of black holes from any of this,” says Robert Wald, a gravitational theorist at the University of Chicago. Others aren’t so sure. “Are black holes strictly the same as you would expect with general relativity or are they different?” asks Clifford Will, a gravitational theorist at the University of Florida. “That’s going to be a major thrust of future observations.” Any anomalies would require a rethink of Einstein’s theory, which physicists suspect is not the final word on gravity, as it doesn’t jibe with the other cornerstone of modern physics, quantum mechanics.

    Using multiple techniques, researchers are already gaining different, complementary views of these strange objects, says Andrea Ghez, an astrophysicist at the University of California, Los Angeles, who shared the 2020 Nobel Prize in Physics for inferring the existence of the supermassive black hole in the heart of our Galaxy. “We’re still a long way from putting a complete picture together,” she says, “but we’re certainly getting more of the puzzle pieces in place.”

    Andrea Ghez has centered her work at the W.M Keck Observatory.

    W.M. Keck Observatory, two ten meter telescopes operated by Caltech and the University of California, Maunakea Hawaii USA, altitude 4,207 m (13,802 ft). Credit: Caltech.

    Consisting of pure gravitational energy, a black hole is a ball of contradictions. It contains no matter, but, like a bowling ball, possesses mass and can spin. It has no surface, but has a size. It behaves like an imposing, weighty object, but is really just a peculiar region of space.

    Or so says general relativity, which Einstein published in 1915. Two centuries earlier, Isaac Newton had posited that gravity is a force that somehow reaches through space to attract massive objects to one another. Einstein went deeper and argued that gravity arises because massive things such as stars and planets warp space and time—more accurately, spacetime—causing the trajectories of freely falling objects to curve into, say, the parabolic arc of a thrown ball.

    Early predictions of general relativity differed only slightly from those of Newton’s theory. Whereas Newton predicted that a planet should orbit its star in an ellipse, general relativity predicts that the orientation of the ellipse should advance slightly, or precess, with each orbit. In the first triumph of the theory, Einstein showed it accounted for the previously unexplained precession of the orbit of the planet Mercury. Only years later did physicists realize the theory also implied something far more radical.

    In 1939, theorist J. Robert Oppenheimer and colleagues calculated that when a sufficiently massive star burned out, no known force could stop its core from collapsing to an infinitesimal point, leaving behind its gravitational field as a permanent pit in spacetime. Within a certain distance of the point, gravity would be so strong that not even light could escape. Anything closer would be cut off from the rest of the universe, David Finkelstein, a theorist at Caltech, argued in 1958. This “event horizon” isn’t a physical surface. An astronaut falling past it would notice nothing special. Nevertheless, reasoned Finkelstein, who died just days before LIGO’s announcement in 2016, the horizon would act like a one-way membrane, letting things fall in, but preventing anything from getting out.

    According to general relativity, these objects—eventually named black holes by famed theorist John Archibald Wheeler—should also exhibit a shocking sameness. In 1963, Roy Kerr, a mathematician from New Zealand, worked out how a spinning black hole of a given mass would warp and twist spacetime. Others soon proved that, in general relativity, mass and spin are the only characteristics a black hole can have, implying that Kerr’s mathematical formula, known as the Kerr metric, describes every black hole there is. Wheeler dubbed the result the no-hair theorem to emphasize that two black holes of the same mass and spin are as indistinguishable as bald pates. Wheeler himself was bald, Teukolsky notes, “so maybe it was bald pride.”

    Some physicists suspected black holes might not exist outside theorists’ imaginations, says Sean Carroll, a theorist at Caltech. Skeptics argued that black holes might be an artifact of general relativity’s subtle math, or that they might only form under unrealistic conditions, such as the collapse of a perfectly spherical star. However, in the late 1960s, Roger Penrose, a theorist at the University of Oxford, dispelled such doubts with rigorous math, for which he shared the 2020 Nobel Prize in Physics. “Penrose exactly proved that, no, no, even if you have a lumpy thing, as long as the density became high enough, it was going to collapse to a black hole,” Carroll says.

    Soon enough, astronomers began to see signs of actual black holes. They spotted tiny x-ray sources, such as Cygnus X-1, each in orbit around a star. Astrophysicists deduced that the x-rays came from gas flowing from the star and heating up as it fell onto the mysterious object. The temperature of the gas and the details of the orbit implied the x-ray source was too massive and too small to be anything but a black hole. Similar reasoning suggested quasars, distant galaxies spewing radiation, are powered by supermassive black holes in their centers.

    But no one could be sure those black holes actually are what theorists had pictured, notes Feryal Özel, an astrophysicist at the University of Arizona (UA). For example, “Very little that we have done so far establishes the presence of an event horizon,” she says. “That is an open question.”

    Now, with multiple ways to peer at black holes, scientists can start to test their understanding and look for surprises that could revolutionize physics. “Even though it’s very unlikely, it would be so amazingly important if we found that there was any deviation” from the predictions of general relativity, Carroll says. “It’s a very high-risk, high-reward question.”

    Scientists hope to answer three specific questions: Do the observed black holes really have event horizons? Are they as featureless as the no-hair theorem says? And do they distort spacetime exactly as the Kerr metric predicts?

    Perhaps the simplest tool for answering them is one that Ghez developed. Since 1995, she and colleagues have used the 10-meter Keck telescope in Hawaii to track stars around a radio source known as Sagittarius A* (Sgr A*) in the center of our Galaxy. In 1998, the stars’ high speeds revealed they orbit an object 4 million times as massive as the Sun. Because Sgr A* packs so much mass into such a small volume, general relativity predicts it must be a supermassive black hole. Reinhard Genzel, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics, independently tracked the stars to reach the same conclusion and shared the Nobel Prize with Ghez.

    Richard Genzel studied back holes at the VLT of the European Southern Observatory.

    ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
    •KUEYEN (UT2; The Moon ),
    •MELIPAL (UT3; The Southern Cross ), and
    •YEPUN (UT4; Venus – as evening star).
    elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

    Much of the information comes from a single star, dubbed SO2 by Ghez, which whips around Sgr A* once every 16 years.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the Milky Way.

    Just as the orbit of Mercury around the Sun precesses, so, too, should the orbit of SO2. Ghez and colleagues are now trying to tease out that precession from the extremely complicated data. “We’re right on the cusp,” she says. “We have a signal, but we’re still trying to convince ourselves that it’s real.” (In April 2020, Genzel and colleagues claimed to have seen the precession.)

    If they get a little lucky, Ghez and company hope to look for other anomalies that would probe the nature of the supermassive black hole. Close to the black hole, its spin should modify the precession of a star’s orbit in a way that’s predictable from Kerr’s mathematical description. “If there were stars even closer than the ones they’ve seen—maybe 10 times closer—then you could test whether the Kerr metric is exactly correct,” Will says.

    The star tracking will likely never probe very close to the event horizon of Sgr A*, which could fit within the orbit of Mercury. But EHT, which combines data from 11 radio telescopes or arrays around the world to form, essentially, one big telescope, has offered a closer look at a different supermassive black hole, the 6.5-billion-solar-mass beast in M87.

    The famous image the team released 2 years ago, which resembles a fiery circus hoop, is more complicated than it looks. The bright ring emanates from hot gas, but the dark center is not the black hole itself. Rather it is a “shadow” cast by the black hole as its gravity distorts or “lenses” the light from the gas in front of it. The edge of shadow marks not the event horizon, but rather a distance about 50% farther out where spacetime is distorted just enough so that passing light circles the black hole, neither escaping nor falling into the maw.

    Even so, the image holds clues about the object at its center. The spectrum of the glowing ring could reveal, for example, whether the object has a physical surface rather than an event horizon. Matter crashing onto a surface would shine even brighter than stuff sliding into a black hole, Özel explains. (So far researchers have seen no spectral distortion.) The shadow’s shape can also test the classical picture of a black hole. A spinning black hole’s event horizon should bulge at the equator. However, other effects in general relativity should counteract that effect on the shadow. “Because of a very funky cancellation of squishing in different directions, the shadow still looks circular,” Özel says. “That’s why the shape of the shadow becomes a direct test of the no-hair theorem.”

    Some researchers doubt EHT can image the black hole with enough precision for such tests. Samuel Gralla, a theorist at UA, questions whether EHT is even seeing a black hole shadow or merely viewing the disk of gas swirling around the black hole from the top down, in which case the dark spot is simply the eye of that astrophysical hurricane. But Özel says that even with limited resolution, EHT can contribute significantly to testing general relativity in the conceptual terra incognita around a black hole.

    Gravitational waves, in contrast, convey information straight from the black holes themselves. Churned out when black holes spiral together at half the speed of light, these ripples in spacetime pass unimpeded through ordinary matter. LIGO and Virgo have now detected mergers of black holes with masses ranging from three to 86 solar masses.

    The mergers can probe the black holes in several ways, says Frank Ohme, a gravitational theorist and LIGO member at the Max Planck Institute for Gravitational Physics. Assuming the objects are classical black holes, researchers can calculate from general relativity how the chirplike gravitational wave signal from a merger should speed up, climax in a spike, and then ring down. If the massive partners are actually larger material objects, then as they draw close they should distort each other, altering the peak of the signal. So far, researchers see no alterations, Ohme says.

    The merger produces a perturbed black hole just like the one in Teukolsky’s old thesis, offering another test of general relativity. The final black hole undulates briefly but powerfully, at one main frequency and multiple shorter lived overtones. According to the no-hair theorem, those frequencies and lifetimes only depend on the final black hole’s mass and spin. “If you analyze each mode individually, they all have to point to the same black hole mass and spin or something’s wrong,” Ohme says.

    In September 2019, Teukolsky and colleagues teased out the main vibration and a single overtone from a particularly loud merger. If experimenters can improve the sensitivity of their detectors, Ohme says, they might be able to spot two or three overtones—enough to start to test the no-hair theorem.

    Future instruments may make such tests much easier. The 30-meter optical telescopes being built in Chile and Hawaii should scrutinize the neighborhood of Sgr A* with a resolution roughly 80 times better than current instruments, Ghez says, possibly spying closer stars. Similarly, EHT researchers are adding more radio dishes to their network, which should enable them to image the black hole in M87 more precisely. They’re also trying to image Sgr A*.

    Meanwhile, gravitational wave researchers are already planning the next generation of more sensitive detectors, including the Laser Interferometer Space Antenna (LISA), made up of three satellites flying in formation millions of kilometers apart. To be launched in the 2030s, LISA would be so sensitive that it could spot an ordinary stellar-mass black hole spiraling into a much bigger supermassive black hole in a distant galaxy, says Nicolas Yunes, a theoretical physicist at the University of Illinois, Urbana-Champaign.

    The smaller black hole would serve as a precise probe of the spacetime around the bigger black hole, revealing whether it warps and twists exactly as the Kerr metric dictates. An affirmative result would cement the case that black holes are what general relativity predicts, Yunes says. “But you have to wait for LISA.”

    In the meantime, the sudden observability of black holes has changed the lives of gravitational physicists. Once the domain of thought experiments and elegant but abstract calculations like Teukolsky’s, general relativity and black holes are suddenly the hottest things in fundamental physics, with experts in general relativity feeding vital input to billion-dollar experiments. “I felt this transition very literally myself,” Ohme says. “It was really a small niche community, and with the detection of gravitational waves that all changed.”


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