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  • richardmitnick 9:17 am on January 19, 2022 Permalink | Reply
    Tags: "Is life possible on rogue planets and moons?", "The gamma-ray binary HESS J0632+057", A hydrogen-rich atmosphere can not only prevent free-floating planets from losing their internal radioactive heat to space but could also keep surface temperatures warm., , , , Earth-like planets are not the only places where life could form., Just like Saturn’s moon Titan has a thick atmosphere a sufficiently massive moon of a free-floating planet could have one too., Microorganisms can hypothetically survive on ocean floors of Enceladus-like icy moons around free-floating planets., Oceans on worlds with no Suns but moons, Planets may have been ejected out of our solar system too over 4 billion years ago and now orbit our galaxy as dark worlds., Scientists think planets that don’t orbit any star-called free-floating planets or rogue planets-can harbor life too., Simulated hydrogen-rich environments in labs show that certain terrestrial microorganisms can thrive under such conditions., Starless free-floating worlds might represent the most common habitable real estate of the universe.,   

    From The Planetary Society (US): “Is life possible on rogue planets and moons?” 

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    From The Planetary Society (US)

    Jan 18, 2022
    Jatan Mehta

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    An artist’s illustration of a Jupiter-like planet floating freely in space without a star. Image: The National Aeronautics and Space Administration(US).

    Starless free-floating worlds might represent the most common habitable real estate of the universe.

    Our search for planets around other stars in our galaxy has yielded us more than 4,500 worlds. Quite a few of these exoplanets seem to be Earth-like, where surface conditions could sustain liquid water and life as we know it.

    But even as next generation telescopes aim to detect gases on such planets indicative of life, our search for such habitable worlds remains somewhat limited. Simply put: Earth-like planets are not the only places where life could form.

    We know from our own solar system that icy moons orbiting giant planets far away from the Sun — such as Europa, Ganymede and Enceladus — can have underground, habitable oceans too. Their liquid water isn’t due to the Sun’s heat but rather warmed by friction between parts of their interiors being tugged by their planets’ gravity. If sunlight, a surface and an atmosphere aren’t necessary to make a world habitable, then why confine our search for life to Earth-like worlds that orbit stars?

    Scientists think planets that don’t orbit any star, called free-floating planets or rogue planets, can harbor life too. These planets originally form around stars like any other but get kicked out of their system at some point due to gravitational effects of giant planets within.

    Planets may have been ejected out of our solar system too over 4 billion years ago and now orbit our galaxy as dark worlds. Without a star, how can these dark worlds conceivably host life as we know it? Our exploration of the solar system combined with two decades of exoplanet research tells us there are several possibilities.

    Oceans on worlds with no Suns but moons

    Getting kicked out of a star system early on does have at least one advantage: strong ultraviolet light from young stars can’t strip away hydrogen atmospheres of these planets, which helps retain heat.

    A 1999 research paper [Nature] suggests that a hydrogen-rich atmosphere can not only prevent free-floating planets from losing their internal radioactive heat to space but could also keep surface temperatures warm enough to sustain Earth-like oceans. Simulated hydrogen-rich environments in labs show that certain terrestrial microorganisms can thrive under such conditions. That said, life on free-floating worlds would still have to miraculously emerge using the planet’s miniscule internal energy, compared to over 99% of Earth’s energy coming from sunlight.

    Hypothetically, if a free-floating planet has a large enough moon, it could further heat the planet using tidal mechanisms, similar to our Moon and Earth. When the Moon formed more than 4.4 billion years ago, it was about 15 times closer to us than it is today. It induced such a strong tidal heating that scientists think the Moon may have played a key role in making the early Earth habitable. Even if such heating lasts only a few hundred million years, it could provide a richer source of energy than the free-floating planet’s own heat to keep an ocean warm, initiate complex geology and possibly develop microbial life.

    But how likely is it for free-floating planets to have moons in the first place?

    “There’s nothing theoretically stopping us from having a Moon-sized satellite around a free-floating planet,” said Nick Oberg, a researcher at The Kapteyn Astronomical Institute – University of Gronigen [Rijksuniversiteit Groningen] (NL) and The Delft University of Technology [Technische Universiteit Delft](NL) studying formation of Jupiter’s moons. “Orbital simulations show that more than 47% of moons can remain bound to exiled gas giant planets.” Likewise, simulations with ejected Earth-mass planets show that more than 4% of them retain their Moon-sized satellite.

    Habitable moons around starless worlds

    In addition to exiled free-floating planets being able to retain their moons, it’s also possible for free-floating planets and their satellites to coalesce directly from clouds of gas and dust in interstellar space just like stars do. We have already discovered a free-floating planet candidate surrounded by a disk from which moons like those around Jupiter could form.

    “Planets with multiple satellites, such as the Galilean moons of Jupiter, have even better chances of retaining those moons after being ejected,” said Patricio Javier Ávila, a Chilean researcher of free-floating planets at The University of Concepción [Universidad de Concepción](CL). Just as tidal heating from Jupiter and Saturn creates underground oceans on some of their icy moons, such satellites around free-floating planets could have subsurface oceans too [Astronomy and Astrophysics].

    “If a free-floating planet retains multiple moons and their elliptical orbits, tidal heating could be sustained and with it the subsurface oceans,” Oberg said.

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    Europa’s subsurface ocean cutaway An artist’s illustration of an underground liquid water ocean beneath the thick icy crust of Jupiter’s moon Europa. A similar ocean exists on Saturn’s moon Enceladus too.Image: NASA.

    When NASA’s Cassini spacecraft flew through water plumes erupting from Saturn’s icy moon Enceladus — sourced from its underground ocean — it found a variety of organic molecules, which are building blocks of life.

    National Aeronautics and Space Administration(US)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ASI Italian Space Agency [Agenzia Spaziale Italiana](IT) Cassini Spacecraft.

    Cassini’s observations suggest that Enceladus’ ocean seems to have potentially habitable hydrothermal vents similar to those found in the deepest, darkest parts of Earth’s oceans. Not only do various microorganisms like methanogens thrive near such terrestrial vents, scientists think this is how life on Earth could’ve started in the first place [Nature Reviews Microbiology].

    Microorganisms can hypothetically survive [Nature Communications] on ocean floors of Enceladus-like icy moons around free-floating planets too, well protected from asteroid impacts and harmful radiation by thick icy crusts above.

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    This graphic illustrates hydrothermal vents on Enceladus’ ocean floor that could provide habitable environments for microbial life to form and thrive.Image: NASA-JPL/Caltech (US).

    There’s another possibility, though. Just like Saturn’s moon Titan has a thick atmosphere a sufficiently massive moon of a free-floating planet could have one too. Coupled with tidal heating, Earth-mass exomoons of these could have high enough temperatures to sustain oceans on their surface for hundreds of millions of years, and be favorable to microbial life.

    Okay, but can we even detect starless worlds?

    For all their potential to host life, it’s incredibly difficult to detect dark, free-floating worlds in our galaxy using traditional exoplanet-catching methods. It’s hard enough already to find miniscule planets even when they have stars!

    Even though free-floating planets should be common, and at least one of them might be lying within (astronomically) merely 10 light years from us, we haven’t found any yet.

    “It’s challenging to verify these objects as true free-floating planets because their mass can be so difficult to accurately estimate,” said Oberg.

    In 2013, scientists directly imaged [The Astrophysical Journal] a Jupiter-like free-floating planet candidate 80 light years away, but it’s hard to tell it apart from a class of objects called brown dwarfs.

    Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech.

    Example of direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. Credit: The National Aeronautics and Space Administration(US), The European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU), and P. Kalas, The University of California-Berkeley (US) and The SETI Institute (US).

    These are more massive than Jupiter but are called “failed stars” because they aren’t massive enough to fuse hydrogen in their cores.

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    Directly image free-floating world Direct image of the free-floating planet candidate PSO J318.5-22, visible as the dot with the reddish hue.Image: N. Metcalfe / Pan-STARRS 1

    U Hawaii (US) Pan-STARRS1 (PS1) Panoramic Survey Telescope and Rapid Response System is a 1.8-meter diameter telescope situated at Haleakala Observatories near the summit of Haleakala, altitude 10,023 ft (3,055 m) on the Island of Maui, Hawaii, USA. It is equipped with the world’s largest digital camera, with almost 1.4 billion pixels.

    Fourteen more free-floating candidates have been detected using a technique called “gravitational microlensing”, wherein a planet’s gravitational field bends light from objects behind them and magnifies their view like a fish bowl. These are difficult to confirm too.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835.

    “Gravitational microlensing detections are one-time events, making them harder to follow up on,” Ávila said. “It’s also difficult to distinguish a light brown dwarf from a free-floating planet as the technique favors more massive objects.”

    Nevertheless, brown dwarfs could host habitable moons in the same way free-floating planets do. Brown dwarfs have been observed too so there’s some hope.

    Interestingly, moons of free-floating worlds may be relatively easier to detect than their parent objects. Even as we haven’t yet found an exomoon around a typical exoplanet with a host star, we might spot a free-floating object’s moon first because there would be no noise from a glaring star when the moon passes in front of the planet from our view.

    Next generation space telescopes, such as NASA’s recently launched JWST and ESA’s upcoming PLATO telescope, could detect Moon- and Titan-sized satellites orbiting free-floating planets and brown dwarfs.

    National Aeronautics Space Agency(US)/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/ Canadian Space Agency [Agence Spatiale Canadienne](CA) James Webb Infrared Space Telescope(US) annotated. Scheduled for launch in 2011 delayed to October 2021 finally launched December 25, 2021.

    ESA PLATO spacecraft depiction

    Wide-field surveys by NASA’s upcoming Nancy Grace Roman Telescope should increase our chances even more, as should better gravitational microlensing surveys in the future.

    National Aeronautics and Space Administration(US) Nancy Grace Roman Space Telescope [WFIRST] depiction.

    Detecting exomoons and the nature of their orbits will allow scientists to determine properties of their parent objects.

    Even if we discover no or few exomoons around free-floating worlds, next generation telescopes will still advance our understanding of moons in general.

    “JWST and future telescopes will vastly increase our understanding of moon-forming disks around regular exoplanets, which are not only easier to spot and study than exomoons but have already been detected,” said Jesper Tjoa, a researcher at the University of Heidelberg. An example of such a system is the moon-forming disk around the young Jupiter-like planet PDS 70c nearly 400 light years away.

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    A moon-forming disk Wide and close-up views of the moon-forming disk surrounding PDS 70c, a young Jupiter-like planet nearly 400 light-years away, as seen with the ALMA telescope on Earth.Image: The Atacama Large Millimiter/submillimeter Array (CL) / The European Southern Observatory [Observatoire européen austral][Europaiche Sûdsternwarte] (EU)(CL).

    European Southern Observatory/National Radio Astronomy Observatory(US)/National Astronomical Observatory of Japan(JP) ALMA Observatory (CL).

    European Southern Observatory(EU) , Very Large Telescope 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.

    Finding exomoons across the galaxy and understanding how they form and evolve would provide us insights into how moons in our solar system formed, and how common habitable moons are.

    The habitable worlds next door

    The possibility that icy moons of free-floating planets or of exoplanets with host stars could harbor life is tantalizing, and ties back to our solar system. Even if we do find habitable exomoons with great difficulty, there’s no way for us to be sure if they host life. The only place for us to definitively confirm alien exomoon life is our solar system, wherein we can send spacecraft to measure things with precision and even fetch samples. In fact, studying icy moons of our solar system with spacecraft is what helps us model the possibilities of habitable exomoons.

    This is precisely why some of the biggest planetary science missions launching this decade, like JUICE and Europa Clipper, are dedicated to finding if underground oceans of Jupiter’s icy moons are habitable.

    European Space Agency [Agence spatiale européenne](EU) Juice spacecraft depiction.

    European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)Juice Schematic.

    NASA Europa Clipper depiction.
    NASA/Europa Clipper annotated.

    Future mission concepts such as the Enceladus Life Finder would look for direct signs of life in Enceladus’ water plumes. NASA is launching the Dragonfly mission later in the decade to explore Titan’s surface to understand possible starting ingredients for life on early Earth and elsewhere.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    3

    In 1980, Carl Sagan, Louis Friedman, and Bruce Murray founded The Planetary Society (US) . They saw that there was enormous public interest in space, but that this was not reflected in government, as NASA’s budget was cut again and again.

    Today, The Planetary Society (US) continues this work, under the leadership of CEO Bill Nye, as the world’s largest and most influential non-profit space organization. The organization is supported by over 50,000 members in over 100 countries, and by hundreds of volunteers around the world.

    Our mission is to empower the world’s citizens to advance space science and exploration. We advocate for space and planetary science funding in government, inspire and educate people around the world, and develop and fund groundbreaking space science and technology.

    We introduce people to the wonders of the cosmos, bridging the gap between the scientific community and the general public to inspire and educate people from all walks of life.

    We give every citizen of the planet the opportunity to make their voices heard in government and effect real change in support of space exploration.

    And we bring ordinary people directly to the frontier of exploration as we crowdfund innovative and exciting space technologies.

     
  • richardmitnick 10:31 pm on January 17, 2022 Permalink | Reply
    Tags: , "The gamma-ray binary HESS J0632+057", , , , , In all but one case it is known that the stellar component is a massive hot star., In contrast the nature of the compact objects in these binary systems is usually not known., Nine known or suspected gamma-ray sources are in binary systems-compact objects orbiting a star with periodic releases of energy., Space based UV/Visible light Astronomy, The gamma-ray binary HESS J0632+057-located about five thousand light-years away in our galaxy-is coincident with the hot optical star MWC 148 and an associated X-ray source., VHE-very high energy gamma rays   

    From The Harvard-Smithsonian Center for Astrophysics (US) via phys.org: “The gamma-ray binary HESS J0632+057” 

    From The Harvard-Smithsonian Center for Astrophysics (US)

    via

    phys.org

    January 17, 2022

    1
    Credit: Harvard-Smithsonian Center for Astrophysics.

    Gamma rays are the most energetic known form of electromagnetic radiation, with each gamma-ray being at least one hundred thousand times more energetic than an optical light photon. Very high energy (VHE) gamma rays pack energies a billion times this amount, or even more. Astronomers think that VHE gamma rays are produced in the environment of the winds or jets of the compact, ultra-dense remnant ashes of massive stars left behind from supernova explosions. There are two kinds of compact remnants: black holes and neutron stars (stars made up predominantly of neutrons, with densities equivalent to the mass of the Sun packed into a volume about 10 kilometers in radius). The winds or jets from the environments of such objects can accelerate charged particles to very close to the speed of light, and radiation that scatters off such energetic particles can become energized, as well, sometimes turning into VHE gamma rays.

    Nine known or suspected gamma-ray sources are in binary systems, compact objects orbiting a star with periodic releases of energy. Every member of this class has its own unique characteristics but in all but one case it is known that the stellar component is a massive hot star, often surrounded by an equatorial disk. In contrast the nature of the compact objects in these binary systems is usually not known. The gamma-ray binary HESS J0632+057, located about five thousand light-years away in our galaxy, is coincident with the hot optical star MWC 148 and an associated X-ray source. In 2007 H.E.S.S. (The High Energy Stereoscopic System) discovered that this source emitted gamma rays, but in 2009 VERITAS (the Very Energetic Radiation Imaging Telescope Array System, located at the SAO’s Fred L. Whipple Observatory in Arizona) could not detect it and set a limit that showed the source was variable at gamma-ray energies.

    H.E.S.S. Čerenkov Telescope Array, located on the Cranz family farm, Göllschau, in Namibia, near the Gamsberg searches for cosmic rays, altitude, 1,800 m (5,900 ft).

    The University of Arizona (US) Veritas Four Čerenkov telescopes A novel gamma ray telescope under construction at the CfA Fred Lawrence Whipple Observatory (US), Mount Hopkins, Arizona (US), altitude 2,606 m 8,550 ft. A large project known as the Čerenkov Telescope Array, composed of hundreds of similar telescopes to be situated at Roque de los Muchachos Observatory [Instituto de Astrofísica de Canarias ](ES) in the Canary Islands and Chile at European Southern Observatory Cerro Paranal(EU) site. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison (US) and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.

    Then in 2009, VERITAS and the MAGIC gamma-ray telescopes detected the source with enhanced emission.

    MAGIC Čerenkov telescopes at the Observatorio del Roque de los Muchachos (Garfia, La Palma (ES), Altitude 2,396 m (7,861 ft).

    Around the same time observations taken with the Swift-XRT mission found that the source had a period in X-ray emission of about 321 days, establishing the binary nature of the object; radio observations found it had a jet a few astronomical units in length.

    National Aeronautics and Space Administration(US) Neil Gehrels Swift X-ray, and UV/Visible light Observatory.

    CfA astronomer Wystan Benbow and a large international team probed the nature of the compact object in this binary system. They completed an analysis of 15 years of gamma-ray observations, as well as X-ray observations from a number of facilities. For the first time they were able to determine the orbital period in VHE emission, 316.7 days with an uncertainty of about 1.4 percent, and consistent with the period measured at other wavelengths. The strong correlation between the X-ray and gamma-ray behaviors suggests that a single population of rapidly moving charged particles is responsible for both, while the absence of a correlation with emission lines of atomic hydrogen implies that any variations in the hot star play a negligible role. The astronomers now are planning deeper, multi-year simultaneous multiwavelength observations to further characterize the emission and the source structure.

    Science paper:
    The Astrophysical Journal

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

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

    Founded in 1973 and headquartered in Cambridge, Massachusetts, the CfA leads a broad program of research in astronomy, astrophysics, Earth and space sciences, as well as science education. The CfA either leads or participates in the development and operations of more than fifteen ground- and space-based astronomical research observatories across the electromagnetic spectrum, including the forthcoming Giant Magellan Telescope(CL) and the Chandra X-ray Observatory(US), one of NASA’s Great Observatories.

    GMT Giant Magellan Telescope(CL) 21 meters, to be at the Carnegie Institution for Science’s(US) NSF (US) NOIRLab(US) NOAO(US) Las Campanas Observatory(CL) some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high.

    National Aeronautics and Space Administration(US) Chandra X-ray telescope(US).

    Hosting more than 850 scientists, engineers, and support staff, the CfA is among the largest astronomical research institutes in the world. Its projects have included Nobel Prize-winning advances in cosmology and high energy astrophysics, the discovery of many exoplanets, and the first image of a black hole. The CfA also serves a major role in the global astrophysics research community: the CfA’s Astrophysics Data System(ADS)(US), for example, has been universally adopted as the world’s online database of astronomy and physics papers. Known for most of its history as the “Harvard-Smithsonian Center for Astrophysics”, the CfA rebranded in 2018 to its current name in an effort to reflect its unique status as a joint collaboration between Harvard University and the Smithsonian Institution. The CfA’s current Director (since 2004) is Charles R. Alcock, who succeeds Irwin I. Shapiro (Director from 1982 to 2004) and George B. Field (Director from 1973 to 1982).

    The Center for Astrophysics | Harvard & Smithsonian is not formally an independent legal organization, but rather an institutional entity operated under a Memorandum of Understanding between Harvard University and the Smithsonian Institution. This collaboration was formalized on July 1, 1973, with the goal of coordinating the related research activities of the Harvard College Observatory (HCO) and the Smithsonian Astrophysical Observatory (SAO) under the leadership of a single Director, and housed within the same complex of buildings on the Harvard campus in Cambridge, Massachusetts. The CfA’s history is therefore also that of the two fully independent organizations that comprise it. With a combined lifetime of more than 300 years, HCO and SAO have been host to major milestones in astronomical history that predate the CfA’s founding.

    History of the Smithsonian Astrophysical Observatory (SAO)

    Samuel Pierpont Langley, the third Secretary of the Smithsonian, founded the Smithsonian Astrophysical Observatory on the south yard of the Smithsonian Castle (on the U.S. National Mall) on March 1,1890. The Astrophysical Observatory’s initial, primary purpose was to “record the amount and character of the Sun’s heat”. Charles Greeley Abbot was named SAO’s first director, and the observatory operated solar telescopes to take daily measurements of the Sun’s intensity in different regions of the optical electromagnetic spectrum. In doing so, the observatory enabled Abbot to make critical refinements to the Solar constant, as well as to serendipitously discover Solar variability. It is likely that SAO’s early history as a solar observatory was part of the inspiration behind the Smithsonian’s “sunburst” logo, designed in 1965 by Crimilda Pontes.

    In 1955, the scientific headquarters of SAO moved from Washington, D.C. to Cambridge, Massachusetts to affiliate with the Harvard College Observatory (HCO). Fred Lawrence Whipple, then the chairman of the Harvard Astronomy Department, was named the new director of SAO. The collaborative relationship between SAO and HCO therefore predates the official creation of the CfA by 18 years. SAO’s move to Harvard’s campus also resulted in a rapid expansion of its research program. Following the launch of Sputnik (the world’s first human-made satellite) in 1957, SAO accepted a national challenge to create a worldwide satellite-tracking network, collaborating with the United States Air Force on Project Space Track.

    With the creation of National Aeronautics and Space Administration(US) the following year and throughout the space race, SAO led major efforts in the development of orbiting observatories and large ground-based telescopes, laboratory and theoretical astrophysics, as well as the application of computers to astrophysical problems.

    History of Harvard College Observatory (HCO)

    Partly in response to renewed public interest in astronomy following the 1835 return of Halley’s Comet, the Harvard College Observatory was founded in 1839, when the Harvard Corporation appointed William Cranch Bond as an “Astronomical Observer to the University”. For its first four years of operation, the observatory was situated at the Dana-Palmer House (where Bond also resided) near Harvard Yard, and consisted of little more than three small telescopes and an astronomical clock. In his 1840 book recounting the history of the college, then Harvard President Josiah Quincy III noted that “…there is wanted a reflecting telescope equatorially mounted…”. This telescope, the 15-inch “Great Refractor”, opened seven years later (in 1847) at the top of Observatory Hill in Cambridge (where it still exists today, housed in the oldest of the CfA’s complex of buildings). The telescope was the largest in the United States from 1847 until 1867. William Bond and pioneer photographer John Adams Whipple used the Great Refractor to produce the first clear Daguerrotypes of the Moon (winning them an award at the 1851 Great Exhibition in London). Bond and his son, George Phillips Bond (the second Director of HCO), used it to discover Saturn’s 8th moon, Hyperion (which was also independently discovered by William Lassell).

    Under the directorship of Edward Charles Pickering from 1877 to 1919, the observatory became the world’s major producer of stellar spectra and magnitudes, established an observing station in Peru, and applied mass-production methods to the analysis of data. It was during this time that HCO became host to a series of major discoveries in astronomical history, powered by the Observatory’s so-called “Computers” (women hired by Pickering as skilled workers to process astronomical data). These “Computers” included Williamina Fleming; Annie Jump Cannon; Henrietta Swan Leavitt; Florence Cushman; and Antonia Maury, all widely recognized today as major figures in scientific history. Henrietta Swan Leavitt, for example, discovered the so-called period-luminosity relation for Classical Cepheid variable stars, establishing the first major “standard candle” with which to measure the distance to galaxies. Now called “Leavitt’s Law”, the discovery is regarded as one of the most foundational and important in the history of astronomy; astronomers like Edwin Hubble, for example, would later use Leavitt’s Law to establish that the Universe is expanding, the primary piece of evidence for the Big Bang model.

    Upon Pickering’s retirement in 1921, the Directorship of HCO fell to Harlow Shapley (a major participant in the so-called “Great Debate” of 1920). This era of the observatory was made famous by the work of Cecelia Payne-Gaposchkin, who became the first woman to earn a Ph.D. in astronomy from Radcliffe College (a short walk from the Observatory). Payne-Gapochkin’s 1925 thesis proposed that stars were composed primarily of hydrogen and helium, an idea thought ridiculous at the time. Between Shapley’s tenure and the formation of the CfA, the observatory was directed by Donald H. Menzel and then Leo Goldberg, both of whom maintained widely recognized programs in solar and stellar astrophysics. Menzel played a major role in encouraging the Smithsonian Astrophysical Observatory to move to Cambridge and collaborate more closely with HCO.

    Joint history as the Center for Astrophysics (CfA)

    The collaborative foundation for what would ultimately give rise to the Center for Astrophysics began with SAO’s move to Cambridge in 1955. Fred Whipple, who was already chair of the Harvard Astronomy Department (housed within HCO since 1931), was named SAO’s new director at the start of this new era; an early test of the model for a unified Directorship across HCO and SAO. The following 18 years would see the two independent entities merge ever closer together, operating effectively (but informally) as one large research center.

    This joint relationship was formalized as the new Harvard–Smithsonian Center for Astrophysics on July 1, 1973. George B. Field, then affiliated with UC Berkeley(US), was appointed as its first Director. That same year, a new astronomical journal, the CfA Preprint Series was created, and a CfA/SAO instrument flying aboard Skylab discovered coronal holes on the Sun. The founding of the CfA also coincided with the birth of X-ray astronomy as a new, major field that was largely dominated by CfA scientists in its early years. Riccardo Giacconi, regarded as the “father of X-ray astronomy”, founded the High Energy Astrophysics Division within the new CfA by moving most of his research group (then at American Sciences and Engineering) to SAO in 1973. That group would later go on to launch the Einstein Observatory (the first imaging X-ray telescope) in 1976, and ultimately lead the proposals and development of what would become the Chandra X-ray Observatory. Chandra, the second of NASA’s Great Observatories and still the most powerful X-ray telescope in history, continues operations today as part of the CfA’s Chandra X-ray Center. Giacconi would later win the 2002 Nobel Prize in Physics for his foundational work in X-ray astronomy.

    Shortly after the launch of the Einstein Observatory, the CfA’s Steven Weinberg won the 1979 Nobel Prize in Physics for his work on electroweak unification. The following decade saw the start of the landmark CfA Redshift Survey (the first attempt to map the large scale structure of the Universe), as well as the release of the Field Report, a highly influential Astronomy & Astrophysics Decadal Survey chaired by the outgoing CfA Director George Field. He would be replaced in 1982 by Irwin Shapiro, who during his tenure as Director (1982 to 2004) oversaw the expansion of the CfA’s observing facilities around the world.

    Harvard Smithsonian Center for Astrophysics(US) Fred Lawrence Whipple Observatory(US) located near Amado, Arizona on the slopes of Mount Hopkins, Altitude 2,606 m (8,550 ft)

    European Space Agency [Agence spatiale européenne](EU)/National Aeronautics and Space Administration(US) SOHO satellite. Launched in 1995.

    National Aeronautics Space Agency(US) NASA Kepler Space Telescope (US)

    CfA-led discoveries throughout this period include canonical work on Supernova 1987A, the “CfA2 Great Wall” (then the largest known coherent structure in the Universe), the best-yet evidence for supermassive black holes, and the first convincing evidence for an extrasolar planet.

    The 1990s also saw the CfA unwittingly play a major role in the history of computer science and the internet: in 1990, SAO developed SAOImage, one of the world’s first X11-based applications made publicly available (its successor, DS9, remains the most widely used astronomical FITS image viewer worldwide). During this time, scientists at the CfA also began work on what would become the Astrophysics Data System (ADS), one of the world’s first online databases of research papers. By 1993, the ADS was running the first routine transatlantic queries between databases, a foundational aspect of the internet today.

    The CfA Today

    Research at the CfA

    Charles Alcock, known for a number of major works related to massive compact halo objects, was named the third director of the CfA in 2004. Today Alcock overseas one of the largest and most productive astronomical institutes in the world, with more than 850 staff and an annual budget in excess of $100M. The Harvard Department of Astronomy, housed within the CfA, maintains a continual complement of approximately 60 Ph.D. students, more than 100 postdoctoral researchers, and roughly 25 undergraduate majors in astronomy and astrophysics from Harvard College. SAO, meanwhile, hosts a long-running and highly rated REU Summer Intern program as well as many visiting graduate students. The CfA estimates that roughly 10% of the professional astrophysics community in the United States spent at least a portion of their career or education there.

    The CfA is either a lead or major partner in the operations of the Fred Lawrence Whipple Observatory, the Submillimeter Array, MMT Observatory, the South Pole Telescope, VERITAS, and a number of other smaller ground-based telescopes. The CfA’s 2019-2024 Strategic Plan includes the construction of the Giant Magellan Telescope as a driving priority for the Center.

    CFA Harvard Smithsonian Submillimeter Array on MaunaKea, Hawaii, USA, Altitude 4,205 m (13,796 ft).

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including The University of Chicago (US); The University of California Berkeley (US); Case Western Reserve University (US); Harvard/Smithsonian Astrophysical Observatory (US); The University of Colorado, Boulder; McGill(CA) University, The University of Illinois, Urbana-Champaign;The University of California, Davis; Ludwig Maximilians Universität München(DE); DOE’s Argonne National Laboratory; and The National Institute for Standards and Technology. The University of California, Davis; Ludwig Maximilians Universität München(DE); DOE’s Argonne National Laboratory; and The National Institute for Standards and Technology. It is funded by the National Science Foundation(US).

    Along with the Chandra X-ray Observatory, the CfA plays a central role in a number of space-based observing facilities, including the recently launched Parker Solar Probe, Kepler Space Telescope, the Solar Dynamics Observatory (SDO), and HINODE. The CfA, via the Smithsonian Astrophysical Observatory, recently played a major role in the Lynx X-ray Observatory, a NASA-Funded Large Mission Concept Study commissioned as part of the 2020 Decadal Survey on Astronomy and Astrophysics (“Astro2020”). If launched, Lynx would be the most powerful X-ray observatory constructed to date, enabling order-of-magnitude advances in capability over Chandra.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker. [/caption]

    National Aeronautics and Space Administration(US)Solar Dynamics Observatory(US)

    Japan Aerospace Exploration Agency (JAXA) (国立研究開発法人宇宙航空研究開発機構] (JP)/National Aeronautics and Space Administration(US) HINODE spacecraft.

    SAO is one of the 13 stakeholder institutes for the Event Horizon Telescope Board, and the CfA hosts its Array Operations Center. In 2019, the project revealed the first direct image of a black hole.

    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).

    The result is widely regarded as a triumph not only of observational radio astronomy, but of its intersection with theoretical astrophysics. Union of the observational and theoretical subfields of astrophysics has been a major focus of the CfA since its founding.

    In 2018, the CfA rebranded, changing its official name to the “Center for Astrophysics | Harvard & Smithsonian” in an effort to reflect its unique status as a joint collaboration between Harvard University and the Smithsonian Institution. Today, the CfA receives roughly 70% of its funding from NASA, 22% from Smithsonian federal funds, and 4% from the National Science Foundation. The remaining 4% comes from contributors including the United States Department of Energy, the Annenberg Foundation, as well as other gifts and endowments.

     
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