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  • richardmitnick 12:10 pm on April 20, 2017 Permalink | Reply
    Tags: Exoplanet research, Oceans galore: new study suggests most habitable planets may lack dry land,   

    From phys.org: “Oceans galore: new study suggests most habitable planets may lack dry land” 

    physdotorg
    phys.org

    April 20, 2017
    Dr Robert Massey

    1
    Continents on other habitable worlds may struggle to break above sea level, like much of Europe in this illustration, representing Earth with an estimated 80% ocean coverage. Credit: Antartis / Depositphotos.com

    When it comes to exploring exoplanets, it may be wise to take a snorkel along. A new study, published in a paper in the journal Monthly Notices of the Royal Astronomical Society, has used a statistical model to predict that most habitable planets may be dominated by oceans spanning over 90% of their surface area.

    The author of the study, Dr Fergus Simpson of the Institute of Cosmos Sciences at the University of Barcelona, has constructed a statistical model – based on Bayesian probability – to predict the division between land and water on habitable exoplanets.

    For a planetary surface to boast extensive areas of both land and water, a delicate balance must be struck between the volume of water it retains over time, and how much space it has to store it in its oceanic basins. Both of these quantities may vary substantially across the full spectrum of water-bearing worlds, and why the Earth’s values are so well balanced is an unresolved and long-standing conundrum.

    Simpson’s model predicts that most habitable planets are dominated by oceans spanning over 90% of their surface area. This conclusion is reached because the Earth itself is very close to being a so-called ‘waterworld’ – a world where all land is immersed under a single ocean.

    “A scenario in which the Earth holds less water than most other habitable planets would be consistent with results from simulations, and could help explain why some planets have been found to be a bit less dense than we expected,” explains Simpson.

    In the new work, Simpson finds that the Earth’s finely balanced oceans may be a consequence of the anthropic principle – more often used in a cosmological context – which accounts for how our observations of the Universe are influenced by the requirement for the formation of sentient life.

    “Based on the Earth’s ocean coverage of 71%, we find substantial evidence supporting the hypothesis that anthropic selection effects are at work,” comments Simpson.

    To test the statistical model Simpson has taken feedback mechanisms into account, such as the deep water cycle, and erosion and deposition processes. He also proposes a statistical approximation to determine the diminishing habitable land area for planets with smaller oceans, as they become increasingly dominated by deserts.

    Why did we evolve on this planet and not on one of the billions of other habitable worlds? In this study Simpson suggests the answer could be linked to a selection effect involving the balance between land and water.

    “Our understanding of the development of life may be far from complete, but it is not so dire that we must adhere to the conventional approximation that all habitable planets have an equal chance of hosting intelligent life,” Simpson concludes.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:46 am on March 1, 2017 Permalink | Reply
    Tags: , , , , , Exoplanet research, Volcanic hydrogen spurs chances of finding exoplanet life   

    From Cornell: “Volcanic hydrogen spurs chances of finding exoplanet life” 

    Cornell Bloc

    Cornell University

    February 27, 2017
    Blaine Freidlander

    1
    (Photo : Wikimedia Commons/E. Klett, U.S. Fish and Wildlife Service)

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    Hunting for habitable exoplanets now may be easier: Cornell astronomers report that hydrogen pouring from volcanic sources on planets throughout the universe could improve the chances of locating life in the cosmos.

    Planets located great distances from stars freeze over. “On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes,” said lead author Ramses Ramirez, research associate at Cornell’s Carl Sagan Institute. “But if the surface is warm enough – thanks to volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures.”

    Combining the greenhouse warming effect from hydrogen, water and carbon dioxide on planets sprinkled throughout the cosmos, distant stars could expand their habitable zones by 30 to 60 percent, according to this new research. “Where we thought you would only find icy wastelands, planets can be nice and warm – as long as volcanoes are in view,” said Lisa Kaltenegger, Cornell professor of astronomy and director of the Carl Sagan Institute.

    3
    Ramses Ramirez, research associate at Cornell’s Carl Sagan Institute, left, and Lisa Kaltenegger, professor of astronomy and director of the Sagan Institute.

    Their research, “A Volcanic Hydrogen Habitable Zone,” is published today in The Astrophysical Journal Letters.

    The idea that hydrogen can warm a planet is not new, but an Earth-like planet cannot hold onto its hydrogen for more than a few million years. Volcanoes change the concept.

    “You get a nice big warming effect from volcanic hydrogen, which is sustainable as long as the volcanoes are intense enough,” said Ramirez, who suggested the possibility that these planets may sustain detectable life on their surface.

    A very light gas, hydrogen also “puffs up” planetary atmospheres, which will likely help scientists detect signs of life. “Adding hydrogen to the air of an exoplanet is a good thing if you’re an astronomer trying to observe potential life from a telescope or a space mission. It increases your signal, making it easier to spot the makeup of the atmosphere as compared to planets without hydrogen,” said Ramirez.

    In our solar system, the habitable zone extends to 1.67 times the Earth-sun distance, just beyond the orbit of Mars. With volcanically sourced hydrogen on planets, this could extend the solar system’s habitable zone reach to 2.4 times the Earth-sun distance – about where the asteroid belt is located between Mars and Jupiter. This research places a lot of planets that scientists previously thought to be too cold to support detectable life back into play.

    “We just increased the width of the habitable zone by about half, adding a lot more planets to our ‘search here’ target list,” said Ramirez.

    3
    Stellar temperature versus distance from the star compared to Earth for the classic habitable zone (shaded blue) and the volcanic habitable zone extension (shaded red). Credit: Ramses Ramirez

    Atmospheric biosignatures, such as methane in combination with ozone – indicating life – will likely be detected by the forthcoming, next-generation James Webb Space Telescope, launching in 2018, or the approaching European Extremely Large Telescope, first light in 2024.

    NASA reported Feb. 22 finding seven Earth-like planets around the star Trappist-1. “Finding multiple planets in the habitable zone of their host star is a great discovery because it means that there can be even more potentially habitable planets per star than we thought,” said Kaltenegger. “Finding more rocky planets in the habitable zone – per star – increases our odds of finding life.”

    With this latest research, Ramirez and Kaltenegger have possibly added to that number by showing that habitats can be found, even those once thought too cold, as long as volcanoes spew enough hydrogen. Such a volcanic hydrogen habitable zone might just make the Trappist-1 system contain four habitable zone planets, instead of three. “Although uncertainties with the orbit of the outermost Trappist-1 planet ‘h’ means that we’ll have to wait and see on that one,” said Kaltenegger.

    The Simons Foundation and the Cornell Center for Astrophysics and Planetary Science funded this research.

    See the full article here .

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    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 10:28 pm on February 13, 2017 Permalink | Reply
    Tags: , , , , Exoplanet research,   

    From Keck: “Over 100 New Exoplanet Candidates Discovered With W. M. Keck Observatory” 

    Keck Observatory

    Keck Observatory.
    Keck, with Subaru and IRTF (NASA Infrared Telescope Facility). Vadim Kurland

    Keck Observatory

    February 13, 2017
    Andrea Lum
    Bennet Group Strategic Communications
    808-286-9569
    andrea@bennetgroup.com

    Rich Matsuda
    W. M. Keck Observatory
    (808) 881-3822
    communications@keck.hawaii.edu

    1
    HIRES instrument helps detect potential exoplanets. Artist’s conceptions of the probable planet orbiting a star called GJ 411, courtesy of Ricardo Ramirez.

    Keck HIRES
    Keck HIRES

    International team of astronomers releases the largest-ever compilation of exoplanet-detecting observations, made from observatory atop Maunakea

    An international team of astronomers today released a compilation of almost 61,000 individual measurements made on more than 1,600 stars, used to detect exoplanets elsewhere in our Milky Way galaxy. The compilation includes data on over 100 new potential exoplanets. The entire dataset was observed using one of the twin telescopes of the W. M. Keck Observatory on Maunakea over the past two decades. The search for new worlds elsewhere in our Milky Way galaxy is one of the most exciting frontiers in astronomy today. The paper is published in the Astronomical Journal.

    HIRES instrument helps detect potential exoplanets

    “The work of this team and their willingness to share data and techniques unveils a world of new possibilities, vastly increasing the ability of astronomers everywhere to perform in-depth studies of these exoplanet systems,” said Hilton Lewis, Keck Observatory Director. “Our observatory is proud to be the source of these discoveries, thanks to our cutting-edge instrumentation and the unparalleled observing conditions atop Maunakea.”

    The astronomers used a highly specialized instrument called the High Resolution Echelle Spectrometer, or HIRES, mounted on the 10-meter Keck-I telescope. The instrument detects tiny wobbles of nearby stars caused by the gravitational pull of planets orbiting those stars -a sensitive and challenging phenomenon to measure. Powerful instrumentation and sophisticated algorithms are needed to extract the signature of the exoplanets.

    “HIRES is an incredible tool, part of the suite of sensitive instruments used to perform all kinds of extraordinary observations with our twin telescopes,” said Greg Doppmann, Keck Observatory Support Astronomer. “Our scientific and technical support team brings their A-game daily-a precise focus on even the tiniest details-to ensure that these instruments are ready to deploy for each night of observing.”

    Contributors to the international team include representatives from the Carnegie Institution for Science, University of California at Santa Cruz, Yale University, University of Hertfordshire, and Universidad de Chile.

    KCWI arrived by ship from Los Angeles on January 20 and was carefully transported up to the observatory atop Maunakea. The instrument will be installed and tested, followed by the first observations in the coming months.

    For more background information, please visit:

    https://carnegiescience.edu/node/2141

    http://news.ucsc.edu/2017/02/hires-data-release.html

    http://news.mit.edu/2017/dataset-nearby-stars-available-public-exoplanets-0213

    See the full article here .

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    Mission
    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
    Keck UCal

     
  • richardmitnick 4:32 pm on February 2, 2017 Permalink | Reply
    Tags: , , , , , Exoplanet research, High Energy Density Science instrument at the European XFEL or HED   

    From XFEL: “DFG funds investigation of exoplanets at European XFEL” 

    XFEL bloc

    European XFEL

    02 February 2017
    No writer credit found

    Interdisciplinary research project funded with 2 M€

    With the help of telescopes on Earth and in space, several thousand planets outside of our solar system have been discovered since 1996. Observation data such as mass, radius, and distance from their central star give only a few details about the composition and origin of these exoplanets. The research unit “Matter Under Planetary Interior Conditions”, led by the University of Rostock and including scientists from European XFEL will find out more about these planets in the framework of a grant funded by the German Research Foundation (DFG). The researchers want to draw inferences about exoplanets based on the planets in our own solar system and develop suitable methods for this purpose. Their interdisciplinary collaboration comprises theory, planetary modelling, and experiments. This comprises experimental investigations of materials under extreme conditions, such as those found inside of planets at, among others, the European XFEL and the research centre DESY. The DFG will fund the project for the next three years with a total contribution of around 2 million euro.

    “A strength of our proposal is that it combines theory, planetary modelling, and experiments in order to learn more about the composition and development of planets inside and outside of our solar system”, says Prof. Ronald Redmer of the University of Rostock, spokesperson for the research unit. In addition, the findings will be used for the evaluation of observation data from satellite missions.

    1
    This artist concept depicts in the foreground planet Kepler-62f, a super-Earth-size planet in the habitable zone of its star, which is seen peeking out from behind the right edge of the planet.
    NASA/JPL

    The Kepler Space Telescope has discovered a large number of planets between one and twenty times the mass of the Earth in orbits close to Sun-like stars.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

    These exoplanets are defined as so-called “super-Earths”, which have a similar density and masses up to ten times that of the Earth, and neptunian planets, which have a similar density as the planet Neptune in our solar system. Neptune has a solid core; a mantle composed of liquid water, ammonia, and methane; as well as an atmosphere made of hydrogen, helium, and methane. In the interiors of all of these types of planets pressures can be many times higher than those inside the Earth and temperatures can reach several thousand degrees Celsius. The researchers want to find out how the principal constituents of these planets—for example, magnesium oxide and silicates for super-Earths as well as water, methane, and ammonia for neptunian planets—behave under these conditions.

    The High Energy Density Science instrument at the European XFEL, or HED for short, enables experimental investigations of extreme states of matter like those found inside of planets.

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    https://www.researchgate.net/publication/273045438_Scientific_Instrument_High_Energy_Density_Physics_HED

    “In the course of these experiments, we can generate brief spikes in pressure up to a million bar on the sample”, explains Karen Appel, a scientist at HED and project leader for this part of the research unit’s proposal. “The pressure would be as strong as having the weight of the world’s tallest building, the Burj Khalifa in Dubai, on someone’s fingertip.” The high pressures and temperatures at the HED instrument are generated through a shockwave triggered by an intense laser pulse. If the material decompresses after the shock, it goes through many different combinations of pressures and temperatures with distinctive material characteristics within very small fractions of a second. The short light flashes of the European XFEL enable sharp snapshots of these states and their properties to be taken. “Through X-ray scattering and X-ray spectroscopy, we will be able to determine the time-resolved structure and properties of magnesium oxide and silicates under these conditions”, says Appel. “With that, we can gather essential data for planetary modelling.”

    Other than the Universities of Rostock and Bayreuth and European XFEL, DESY and the DLR Institute for Planetary Research in Berlin are also participating.

    See the full article here .

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    XFEL Campus

    The Hamburg area will soon boast a research facility of superlatives: The European XFEL will generate ultrashort X-ray flashes—27 000 times per second and with a brilliance that is a billion times higher than that of the best conventional X-ray radiation sources.

    The outstanding characteristics of the facility are unique worldwide. Starting in 2017, it will open up completely new research opportunities for scientists and industrial users.

     
  • richardmitnick 10:43 am on February 2, 2017 Permalink | Reply
    Tags: , , Atmospheres can protect and nurture or they can destroy, “L” is for the longevity of a potentially civilized intelligent world, , , , Exoplanet research, , , , The fate of Earth is indeed in our hands   

    From Many Worlds: “Do Intelligent Civilizations Across the Galaxies Self Destruct? For Better and Worse, We’re The Test Case” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2017-02-01
    Marc Kaufman

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    The Eastern Seaboard as seen from the International Space Station in 2012. (NASA)

    In 1950, while working at Los Alamos National Laboratory, renowned physicist Enrico Fermi was lunching with colleagues including Edward Teller, Herbert York an Emil Konopinski. The group talked and laughed about a spate of recent UFO reports during the meal, as well as a cartoon about who might be stealing garbage can top.

    A bit later in the meal Fermi famously asked more seriously, “Where are they?” Sure, there were many bogus reports back then about alien flying saucers, but Fermi was asking what has turned out to be a significant and long-lasting question.

    If there are billions of exoplanets out there — as speculated back then but proven now — why have there been no bona fide reports of advanced extraterrestrials visiting Earth, or somehow leaving behind their handiwork?

    Many answers have been offered in the following decades — that we are alone in the universe, that the distances between solar systems are too great to travel, that Earth became home to life early in the galaxy’s history and other planets are only now catching up, that life might be common in the universe but intelligent life is not.

    I would like to focus on another response, however, one that came to mind often while reading a new book by the former holder of the astrobiology chair at the Library of Congress, planetary scientist David Grinspoon.

    This potential explanation is among the most unsettling: that intelligent and technologically advanced beings are likely to ultimately destroy themselves. Along with the creativity, the prowess and the gumption, intelligence brings with it an inherent instinct for unsustainable expansion and unintentional self destruction.

    I should say right off that this is not a view shared by Grinspoon. His Earth in Human Hands, in fact, argues with data and conviction that humans are more likely than not to ultimately find ways to work together and avoid looming global threats from climate change, incoming asteroids, depleting the ozone layer and myriad other potential sources of mass extinction.

    But his larger point is the sobering one: that the fate of Earth is, indeed, in our hands. We humans are a force shaping the planet that is as powerful as a ring of volcanoes, a giant impactor from space, the long-ago rise of lifeforms that could, and did, dramatically change our atmosphere and along the way caused near global extinction.

    It may sound odd, but as he sees it we are now the planet’s most powerful and consequential force of nature.

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    Since the Industrial Revolution and the spread of technology over the past 200 years, humans have become the dominant force on the planet, says David Grinspoon, the first Chair in Astrobiology at the Library of Congress. (Credit: Tony Steele)

    “What I’ve sought to do is describe what is reality on our planet,” Grinspoon told me. “Some people have been hostile and told me it’s arrogant to say humans have so much control over the fate of the planet, and I agree that it’s a sobering thing.”

    But the Earth has been and will be dramatically changed by us. The big question for the future is whether change can be for the better, or will it be unsustainable and for the worse.”

    While Grinspoon’s major themes involve competing paths for the future of our planet, they consistently are based on and informed by knowledge gained in recent decades about planets in our solar system and those very far away. The logic and track record of the search for intelligent life beyond Earth (SETI) also plays a role, as does the author’s relationships — initially via family in childhood — with Carl Sagan and some of the scientists he mentored.

    For instance, Grinspoon has studied Venus and the evolution of its atmosphere. He says that an understanding of the runaway greenhouse effect that created surface temperatures of 800 degrees F has been instumental in the study of climate change on Earth.

    3
    David Grinspoon is a senior scientist at the Planetary Science Institute, and the author of “Earth in Human Hands.”

    Similarly, the disappearance of much of the Martian atmosphere left the once warmer planet frigid and likely lifeless. Sagan’s work on the dust storms of Mars, which have the effect of making the planet colder still, was an early scientific foray into understanding the importance of atmosphere and climate on a potential biosphere. So was Sagan’s work on the possible effects of atomic war — the globally life-destroying “nuclear winter.”

    The clear inference: Planetary atmospheres can change, as ours is doing now with major buildups in carbon dioxide. Atmospheres can protect and nurture, or they can destroy.

    And Exhibit A is the three rocky solar system planets in what is a slightly expanded habitable zone. But only one supports life.

    The buildup of carbon dioxide in the atmosphere and oceans since the onset of the industrial revolution, Grinspoon writes, is a prime example of how intelligent people and their technology can unintentionally have a huge impact on nature and the planet. The jury remains out as to how humanity will respond.

    But Grinspoon also points to the way that nations around the globe responded to the discovery that the ozone layer was being depleted as an example of how humanity can repair unintentional yet potentially extinction-threatening challenges.

    It took a while, but the artificial refrigerants — chlorofluorocarbons (CFCs) — causing the damage were ultimately curtailed and then banned, and there are signs that the worrisome holes in the ozone layer are if not shrinking, at least no longer growing.

    4
    The Drake equation, created by astronomer Frank Drake in 1961, assesses the probability of how many planets in our galaxy might have civilizations that can communicate. The last factor — the “L” for longevity — is considered key. Drake was one of the founders of SETI, and its effort to detect signals from intelligent life beyond Earth.

    This brings us back to the Fermi paradox, and the apparent absence of signs of extraterrestrial intelligence.

    Fermi, and many others, have assumed that successful, technological civilizations elsewhere would have the desire and ultimately know-how to expand beyond their original planet and colonize others. Indeed, early SETI gatherings here and in the former Soviet Union took that drive to expand for granted, a reflection of attitudes of the times.

    This presumed drive to colonize was often discussed as either a kind of biological imperative or an acknowledgement that these “intelligent” civilizations are likely to have seriously damaged their own planets through unsustainable and hazardous growth. Either way, they would be on the move.

    Yet after more than a half century of listening for signals from these presumed intelligent and mobile beings, the SETI effort to detect such life via radio telescopes has come up empty. There are many potential reasons why, but let’s focus on the one introduced earlier.

    The pioneering Drake equation, first put forward in 1961, attempts to assess the probability of finding intelligent civilizations beyond Earth based on factors such as rate of star formation in the galaxy, the number of planets formed and then the percentage with life, then the number with complex life and finally intelligent and technologically-sophisticated life. But it’s the “L” at the end of the equations, says Grinspoon, that is widely considered the most important.

    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA
    SETI/Allen Telescope Array situated at the Hat Creek Radio Observatory, 290 miles (470 km) northeast of San Francisco, California, USA

    The “L” is for the longevity of a potentially civilized, intelligent world, or “the length of time over which such civilizations release detectable signals.”

    Of all the components of the Drake equation, which is filled with unknowns and partially known estimates, L is no doubt the least well defined. After all, no extraterrestrial life, and certainly no intelligent life, has ever be detected.

    Yet as describe by Grinspoon, “L” — which for Earth is about 200 years now — is the key.

    “Let’s say that it’s impossible for a civilization with very powerful technology to last for 10,000 years, or even 1,000 years. That makes the likelihood of ever making contact with them vanishingly small even if life and intelligence are out there. The chances of them being close enough to detect and communicate with are pretty much nil.”

    If the opposite is true, if it’s possible for a civilization to get over their technological adolescence, then they ought to be detectable. Actually, they could last for millions of years using their technology to enhance and protect the planet.”

    Planets face all kinds of dire threats, and catastrophes and extinctions are the rule. But if technology can be used intentionally for the benefit the planet — like protecting it from an asteroid or avoiding the next Ice Age – longevity would clearly improve greatly.”

    This interstellar view, he says, helps to see more clearly what is happening on Earth. Now that through our technologies we have become the prime movers regarding the planet’s health and safety, it is really up to us as a species to choose between allowing these “advances” to knowingly or unintentionally harm the planet, or to consciously use technology to make it better.

    Grinspoon does not see our current century as one when the effects of technology are likely to be intentionally positive. But he does see the movement towards a more sustainable planet to be irreversible, whatever blips might come our way. What’s more, he said, fossil fuels will be largely gone by 2100 and there’s reason to believe the world’s human population will have stabilized — two enormous changes that favor a longer-lived human civilization.

    “The long-held view that humans will always expand, that they will maintain that biologically primitive imperative, that growth is always good — it’s interesting to wonder if those assumptions aren’t inherently wrong,” he said.

    “I suggest that true ‘intelligence’ able to sustain itself involves an inherent questioning of those values, and that a more measured and strategic growth pattern, or even material stasis might be values that come with a more universal intelligence.”

    Whether that intelligence is on Earth or many hundreds of light years away.

    See the full article here .

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    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 1:38 pm on January 20, 2017 Permalink | Reply
    Tags: , , , , , Exoplanet research, HATnet,   

    From AAS NOVA: “Reinflating Giant Planets” 

    AASNOVA

    American Astronomical Society

    18 January 2017
    Susanna Kohler

    1
    Artist’s impression of a hot Jupiter exoplanet transiting across the face of its host star. [NASA/ESA/C. Carreau]

    Two new, large gas-giant exoplanets have been discovered orbiting close to their host stars. A recent study examining these planets — and others like them — may help us to better understand what happens to close-in hot Jupiters as their host stars reach the end of their main-sequence lives.

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    Unbinned transit light curves for HAT-P-65b. [Adapted from Hartman et al. 2016]

    Oversized Giants

    The discovery of HAT-P-65b and HAT-P-66b, two new transiting hot Jupiters, is intriguing. These planets have periods of just under 3 days and masses of roughly 0.5 and 0.8 times that of Jupiter, but their sizes are what’s really interesting: they have inflated radii of 1.89 and 1.59 times that of Jupiter.

    These two planets, discovered using the Hungarian-made Automated Telescope Network (HATNet) in Arizona and Hawaii, mark the latest in an ever-growing sample of gas-giant exoplanets with radii larger than expected based on theoretical planetary structure models.

    HATNet telescopes at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona. Photo credit: Gaspar Bakos.pple-observatory-mount-hopkins-arizona-photo-credit-gaspar-bakos
    HATNet telescopes at Fred Lawrence Whipple Observatory, Mount Hopkins, Arizona. Photo credit: Gaspar Bakos

    HATnet, Mauna Kea Hawaii USA
    HATNet, Mauna Kea Hawaii USA

    What causes this discrepancy? Did the planets just fail to contract to the expected size when they were initially formed, or were they reinflated later in their lifetimes? If the latter, how? These are questions that scientists are only now starting to be able to address using statistics of the sample of close-in, transiting planets.

    Exploring Other Planets

    4
    Unbinned transit light curves for HAT-P-66b. [Hartman et al. 2016]

    Led by Joel Hartman (Princeton University), the team that discovered HAT-P-65b and HAT-P-66b has examined these planets’ observed parameters and those of dozens of other known close-in, transiting exoplanets discovered with a variety of transiting exoplanet missions: HAT, WASP, Kepler, TrES, and KELT. Hartman and collaborators used this sample to draw conclusions about what causes some of these planets to have such large radii.

    The team found that there is a statistically significant correlation between the radii of close-in giant planets and the fractional ages of their host stars (i.e., the star’s age divided by its full expected lifetime). The two newly discovered hot Jupiters with inflated radii, for instance, are orbiting stars that are roughly 84% and 83% through their life spans and are approaching the main-sequence turnoff point.

    6
    Fractional age of the host stars of close-in transiting exoplanets vs. the planet’s radius. There is a statistically significant correlation between age and planet radius. [Adapted from Hartman et al. 2016]

    Late-Life Reinflation

    Hartman and collaborators propose that the data support the following scenario: as host stars evolve and become more luminous toward the ends of their main-sequence lifetimes, they deposit more energy deep into the interiors of the planets closely orbiting them. These close-in planets then increase their equilibrium temperatures — and their radii reinflate as a result.

    Based on these results, we would expect to continue to find hot Jupiters with inflated radii primarily orbiting closely around older stars. Conversely, close-in giant planets around younger stars should primarily have non-inflated radii. As we continue to build our observational sample of transiting hot Jupiters in the future, we will be able to see how this model holds up.

    Citation

    J. D. Hartman et al 2016 AJ 152 182. doi:10.3847/0004-6256/152/6/182

    See the full article here .

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  • richardmitnick 7:41 am on December 10, 2016 Permalink | Reply
    Tags: , , , Could Flaring Stars Change Our Views of Their Planets?, Exoplanet research, Stellar flares   

    From AAS NOVA: “Could Flaring Stars Change Our Views of Their Planets?” 

    AASNOVA

    American Astronomical Society

    9 December 2016
    Susanna Kohler

    1
    Artist’s illustration of an exoplanet being hit by a powerful eruption from its host star. A new study suggests that flare impacts could alter the measurements we make of exoplanet atmospheres. [NASA]

    As the exoplanet count continues to increase, we are making progressively more measurements of exoplanets’ outer atmospheres through spectroscopy. A new study, however, reveals that these measurements may be influenced by the planets’ hosts.

    Spectra From Transits

    Exoplanet spectra taken as they transit their hosts can tell us about the chemical compositions of their atmospheres. Detailed spectroscopic measurements of planet atmospheres should become even more common with the next generation of missions, such as the James Webb Space Telescope (JWST), or Planetary Transits and Oscillations of Stars (PLATO).

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    ESA/PLATO
    “ESA/PLATO

    But is the spectrum that we measure in the brief moment of a planet’s transit necessarily representative of its spectrum all of the time? A team of scientists led by Olivia Venot (University of Leuven in Belgium) argue that it might not be, due to the influence of the planet’s stellar host.

    2
    Atmospheric composition of a planet before flare impacts (dotted lines), during the steady state reached after a flare impact (dashed lines), and during the steady state reached after a second flare impact (solid lines). [Venot et al. 2016]

    The team suggests that when a host’s flares impact upon a planet’s atmosphere (especially likely in the case of active M-dwarfs that commonly harbor planetary systems), this activity may modify the chemical composition of the planet’s atmosphere. This would in turn alter the spectrum that we measure from the exoplanet.

    Modeling Atmospheres

    Venot and collaborators set out to test the effect of stellar flares on exoplanet atmospheres by modeling the atmospheres of two hypothetical planets orbiting the star AD Leo — an active and flaring M dwarf located roughly 16 light-years away — at two different distances. The team then examined what happened to the atmospheres, and to the resulting spectra that we would observe, when they were hit with a stellar flare typical of AD Leo.

    3
    The difference in relative absorption between the initial steady-state and the instantaneous transmission spectra, obtained during the different phases of the flare. The left plot examines the impulsive and gradual phases, when the flare first impacts and then starts to pass. The peak photon flux occurs at 912 seconds. The right plot examines the return to a steady state over 1012 seconds, or roughly ~30,000 years. [Adapted from Venot et al. 2016]

    The authors found that the planets’ atmospheric compositions were significantly affected by the incoming stellar flare. The sudden increase in incoming photon flux changed the chemical abundances of several important molecular species, like hydrogen and ammonia — which resulted in changes to the spectrum that would be observed during the planet’s transit.

    Permanent Impact

    In addition to demonstrating that a planet’s atmospheric composition changes during and immediately after a flare impact, Venot and collaborators show that the chemical alteration isn’t temporary: the planet’s atmosphere doesn’t fully return to its original state after the flare passes. Instead, the authors find that it settles to a new steady-state composition that can be significantly different from the pre-flare composition.

    For a planet that is repeatedly hit by stellar flares, therefore, its atmospheric composition never actually settles to a steady state. Instead it is continually and permanently modified by its host’s activity.

    Venot and collaborators demonstrate that the variations of planetary spectra due to stellar flares should be easily detectable by future missions like JWST. We must therefore be careful about the conclusions we draw about planetary atmospheres from measurements of their spectra.

    Citation

    Olivia Venot et al 2016 ApJ 830 77. doi:10.3847/0004-637X/830/2/77

    See the full article here .

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  • richardmitnick 1:14 pm on December 8, 2016 Permalink | Reply
    Tags: , , , , Exoplanet research, ,   

    From NYT: Women in STEM – “‘The World Sees Me as the One Who Will Find Another Earth’” Sara Seager 

    New York Times

    The New York Times

    DEC. 7, 2016
    Chris Jones

    1
    Sara Seager

    Like many astrophysicists, Sara Seager sometimes has a problem with her perception of scale. Knowing that there are hundreds of billions of galaxies, and that each might contain hundreds of billions of stars, can make the lives of astrophysicists and even those closest to them seem insignificant. Their work can also, paradoxically, bolster their sense of themselves. Believing that you alone might answer the question “Are we alone?” requires considerable ego. Astrophysicists are forever toggling between feelings of bigness and smallness, of hubris and humility, depending on whether they’re looking out or within.

    One perfect blue-sky fall day, Seager boarded a train in Concord, Mass., on her way to her office at M.I.T. and realized she didn’t have her phone. She couldn’t seem to decide whether this was or wasn’t a big deal. Not having her phone would make the day tricky in some ways, because her sons, 13-year-old Max and 11-year-old Alex, had a soccer game after school, and she would need to coordinate a ride to watch them. She also wanted to be able to find and sit with her best friend, Melissa, who sometimes takes the same train to work. “She’s my best friend, but I know she has other best friends,” Seager said, wanting to make the nature of their relationship clear. She is an admirer of clarity. She also likes absolutes, wide-open spaces and time to think, but not too much time to think. She took out her laptop to see if she could email Melissa. The train’s Wi-Fi was down. She would have to occupy herself on the commute alone.

    Seager’s office is on the 17th floor of M.I.T.’s Green Building, the tallest building in Cambridge, its roof dotted with meteorological and radar equipment. She is a tenured professor of physics and of planetary science, certified a “genius” by the MacArthur Foundation in 2013. Her area of expertise is the relatively new field of exoplanets: planets that orbit stars other than our sun. More particular, she wants to find an Earthlike exoplanet — a rocky planet of reasonable mass that orbits its star within a temperate “Goldilocks zone” that is not too hot or too cold, which would allow water to remain liquid — and determine that there is life on it. That is as simple as her math gets.

    Seager’s office is on the 17th floor of M.I.T.’s Green Building, the tallest building in Cambridge, its roof dotted with meteorological and radar equipment. She is a tenured professor of physics and of planetary science, certified a “genius” by the MacArthur Foundation in 2013. Her area of expertise is the relatively new field of exoplanets: planets that orbit stars other than our sun. More particular, she wants to find an Earthlike exoplanet — a rocky planet of reasonable mass that orbits its star within a temperate “Goldilocks zone” that is not too hot or too cold, which would allow water to remain liquid — and determine that there is life on it. That is as simple as her math gets.

    That means Seager, who is 45, has given herself a very difficult problem to solve, the problem that has always plagued astronomy, which, at its essence, is the study of light: Light wages war with itself. Light pollutes. Light blinds.

    Seager has a commanding view of downtown Boston from her office window. She can sweep her eyes, hazel and intense, all the way from the gold Capitol dome to Fenway Park. When Seager works at night and the Red Sox are in town, she sometimes has to close her curtains, because the ballpark’s white lights are so glaring. And on this morning, after the sun completed its rise, her enviable vista became unbearable. It was searing, and she had to draw her curtains. That’s how light can be the object of her passion and also her enemy. Little lights — exoplanets — are washed out by bigger lights — their stars — the way stars are washed out by our biggest light, the sun. Seager’s challenge is that she has dedicated her life to the search for the smallest lights.

    The vastness of space almost defies conventional measures of distance. Driving the speed limit to Alpha Centauri, the nearest star grouping to the sun, would take 50 million years or so; our fastest current spacecraft would make the trip in a relatively brisk 73,000 years. The next-nearest star is six light-years away. To rocket across our galaxy would take about 23,000 times as long as a trip to Alpha Centauri, or 1.7 billion years, and the Milky Way is just one of hundreds of billions of galaxies. The Hubble Space Telescope once searched a tiny fragment of the night sky, the size of a penny held at arm’s length, that was long thought by astronomers to be dark. It contained 3,000 previously unseen points of light. Not 3,000 new stars — 3,000 new galaxies. And in all those galaxies, orbiting around some large percentage of each of their virtually countless stars: planets. Planets like Neptune, planets like Mercury, planets like Earth.

    As late as the 1990s, exoplanets remained a largely theoretical construct. Logic dictated that they must be out there, but proof of their existence remained as out of reach as they were. Some scientists dismissed efforts to find exoplanets as “stamp collecting,” a derogatory term within the community for hunting new, unreachable lights just to name them. (Even among astronomers, there can be too much stargazing.) It wasn’t until 1995 that the colossal 51 Pegasi b, the first widely recognized exoplanet orbiting a sunlike star, was found by a pair of Swiss astronomers using a light-analyzing spectrograph. The Swiss didn’t see 51 Pegasi b; no one has. By using a complex mathematical method called radial velocity, they witnessed the planet’s gravitational effect on its star and deduced that it must be there.

    There has been an explosion of knowledge in the relatively short time since, in part because of Seager’s pioneering theoretical work in using light to study the composition of alien atmospheres. When starlight passes through a planet’s atmosphere, certain potentially life-betraying gases, like oxygen, will block particular wavelengths of light. It’s a way of seeing something by looking for what’s not there.

    Light or its absence is also the root of something called the transit technique, a newer, more efficient way than radial velocity of finding exoplanets by looking at their stars. It treats light almost like music, something that can be sensed more accurately than it can be seen. The Kepler space telescope, launched in 2009 and now trailing 75 million miles behind Earth, detects exoplanets when they orbit between their stars and the telescope’s mirrors, making tiny but measurable partial eclipses.

    NASA/Kepler Telescope
    NASA/Kepler Telescope

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

    A planet the size of Jupiter passing in front of its sun might result in a 1 percent dip in the amount of starlight Kepler receives, a drop that, in time, reveals itself to be as regular as rhythm, as an orbit. The transit technique has led to a bonanza of finds. In May, NASA announced the validation of 1,284 exoplanets, by far the largest single collection of new worlds yet. There are now 3,414 confirmed exoplanets and an additional 4,696 suspected ones, the count forever increasing.

    Before Kepler, the nature of the transit technique meant that most of those exoplanets were “Hot Jupiters,” giant balls of hydrogen and helium with short orbits, making them scalding, lifeless behemoths. But in April 2014, Kepler found its first Earth-size exoplanet in its star’s habitable zone: Kepler-186f. It’s about 10 percent larger than Earth and orbits on the outer reaches of where the temperature could allow life. No one knows the mass, composition or density of Kepler-186f, but its discovery remains a revelation. Kepler was searching, somewhat blindly, an impossibly small sliver of space, and it found a potentially habitable world more quickly than anyone might have guessed.

    In August, astronomers at the European Southern Observatory announced that they had detected a somewhat similar planet orbiting Proxima Centauri, the single star closest to us after the sun.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    They named it Proxima Centauri b. Studying the data, Seager supported the discovery and agreed that it might boast a life-sustaining — or at least non-life-threatening — surface temperature. There are now nearly 300 confirmed exoplanets or candidates orbiting within the habitable zones of their stars. Extrapolating the math, NASA scientists now believe that there are tens of billions of potentially life-sustaining planets in the Milky Way alone. The odds practically guarantee that a habitable planet is somewhere out there and that someone or something else is, too.

    In some ways, the search for life is now where the search for exoplanets was 20 years ago: Common sense suggests a presence that we can’t confirm. Seager understands that we won’t know they’re out there until we more truly lay eyes on their home and see something that reminds us of ours. Maybe it’s the color blue; maybe it’s clouds; maybe, however many generations from now, it’s the orange electrical grids of alien cities, the black rectangles of their lightless Central Parks. But how could we ever begin to look that far? “Everything brave has to start somewhere,” Seager says.

    The beginning of her next potential breakthrough hangs on the wall opposite the window in her office. It is a two-thirds scale model of a single petal of something called the starshade.

    6

    She has been a leading proponent of the starshade project, and outside her teaching, it is one of her principal professional concerns.

    Imagine that far-off aliens with our present technology were trying to find us. At best, they would see Jupiter. We would be lost in the sun’s glare. The same is true for our trying to see them. The starshade is a way to block the light from our theoretical twin’s sun, an idea floated in 1962 by Lyman Spitzer, who also laid the groundwork for space telescopes like Hubble. The starshade is a huge shield, about a hundred feet across. For practical reasons that have to do with the bending of light, but also lend it a certain cosmic beauty, the starshade is shaped exactly like a sunflower. By Seager’s hopeful reckoning, one day the starshade will be rocketed into space and unfurled, working in tandem with a new space telescope like the Wfirst, scheduled to launch in the mid-2020s.

    NASA/WFIRST
    NASA/WFIRST

    When the telescope is aimed at a particular planetary system, lasers will help align the starshade, floating more than 18,000 miles away, between the telescope and the distant star, closing the curtains on it. With the big light extinguished, the little lights, including a potential Earthlike planet and everything it might represent, will become clear. We will see them.

    The trouble is that sometimes the simplest ideas are the most complicated to execute. About once a decade since Spitzer’s proposal — he could work out the math but not the mechanics — someone else has taken up the cause, advancing the starshade slightly closer to reality before technological or political inertia set in. Three years ago, Seager joined a new, NASA-sponsored study to try to overcome the final practical hurdles; NASA then chose her from among her fellow committee members to lead the effort.

    After those decades of false starts, Seager and her team have already succeeded in making the starshade seem like a real possibility. NASA recognized it as a “technology project,” which is astral-bureaucracy speak for “this might actually happen.” Today the starshade is a piece of buildable, functional hardware. Seager packs that single petal into a battered black case and wheels it, along with a miniature model of the starshade, into classrooms and conferences and the halls of Congress, trying to find the momentum and hundreds of millions of dollars that allow impossible things to exist.

    “If I want the starshade to succeed, I have to help mastermind it,” Seager says. “The world sees me as the one who will find another Earth.” She has her intelligence, and her credentials, and her audience. She has her focus. But maybe more than anything else, Seager understands in ways few of us do that sometimes you need darkness to see.

    Seager grew up in Toronto, wired in a way all her own. “Ever since I was a child, there was just something about me that wasn’t quite like the others,” she says. “Kids know how to sort through who’s the same and who’s different.” After her parents divorced, her father, Dr. David Seager, achieved a certain fame by becoming one of the world’s leaders in hair transplants. The Seager Hair Transplant Center still operates and bears his name a decade after his death. David Seager was besotted with his bright daughter and wanted her to become a physician.

    Seager did her best to fit in. Sometimes she did; mostly she didn’t. Eventually, she gave up trying. She still talks breathlessly — “without enough modulation,” she has learned by listening to other people talk. She has never had the patience to invest in something like watching TV. “Things just move too slowly,” she says. “It feels like a drag.” She sleeps a lot, but that’s just a concession to her biology; she recognizes that she’s a more efficient machine when she’s rested. But if Seager’s apartness didn’t make her insecure, it also made her feel as though the expectations of others didn’t apply to her. “I loved the stars,” she says. When she was 16, she bought a telescope.

    Friendless for most of her childhood, Seager eventually forged her way to her own vision of the good life. She found and married a quiet man named Mike Wevrick, whom she met on a ski trip with her canoe club. He had seen something in her that nobody other than her father fully saw; he saw her as special as well as strange. Later, she graduated from Harvard, an early expert in exoplanets. (51 Pegasi b was discovered just when she was searching for a thesis topic. “I was born at the perfect time,” she says.) She and Wevrick had Max and Alex; Seager was hired by M.I.T., and she and Wevrick and the boys moved into a pretty yellow Victorian in Concord, Mass. She took the train to work. Wevrick, a freelance editor, managed just about everything that didn’t involve the search for intelligent life in the universe. Seager never shopped for groceries or cooked or pumped gas. All she had to do was find another Earth.

    Then, in the fall of 2009, Wevrick got a stomachache that drove him to bed. They figured it was the flu. Wevrick didn’t have the flu, but a rare cancer of the small intestine. They were told that the initial prospects were good, and he fought the cancer sufferer’s systematic fight. But while laws govern astrophysics, cancer is an anarchist. About a year after Wevrick’s diagnosis, he and Seager went cross-country skiing, and he couldn’t keep up. A few more terrible months passed, and he began writing out a methodical three-page list, practical advice for Seager after his death. It wasn’t a love letter; it was an instruction manual for life on Earth. By June 2011, he was 47 and in home hospice. Seager asked him how to get the roof rack that carried his canoes off the car. “It’s too complicated to explain,” Wevrick said. That July, he died.

    The first couple of months after Wevrick’s death were weird. Seager felt a surprising sense of relief from the uncertainties of sickness, a kind of liberation. She didn’t care about conventions like money, which she had never needed to manage, and she took the boys on some epic trips. There are pictures of them smiling together in the deserts of New Mexico, on mountaintops in Hawaii. Then one day, she went into Boston for a haircut, got turned around and accidentally walked into a lawyer’s office next to the salon. Seager ended up talking to a woman inside. That woman was also a widow, and she told Seager that there would be a moment, as inevitable as death itself, when her feelings of release would be replaced by the more lasting aimlessness of the lost. Seager walked back outside, and just like that, the world came out from under her feet. She fell into an impossible blackness.

    Later that winter, she took the boys sledding at the big hill in Concord. Two other women and their children were there. Seager stared at them coldly. They were smiling and carefree with their perfect, blissful lives. Seager felt ugly and ruined next to them. Then Alex, who was 6 at the time, had a meltdown. He sprawled himself across the hill so that the other children couldn’t go down it. The two other mothers tried to get him to move. “He has a problem,” Seager told them. They continued to try to shift him.

    “HE HAS A PROBLEM,” Seager said. “MY HUSBAND DIED.”

    “Mine, too,” one of the other women said. That was Melissa. A few weeks later, on Valentine’s Day, Seager was invited to her first gathering of the widows.

    Today, Melissa says she could detect the telltale “flintiness” of the recently bereaved the moment she saw Seager on the hill. Now there were six widows united in Concord, each middle-aged, each in a different stage of grief, drawn together by the peculiar pull of the unlucky. Three had been widowed by cancer, two by accidents — bicycling and hiking — and one by suicide. Melissa’s husband was four years gone, Seager’s seven months.

    Widowhood was like a new universe for Seager to explore. She had never understood many social norms. The celebration of birthdays, for instance. “I just don’t see the point,” she says. “Why would I want to celebrate my birthday? Why on earth would I even care?” She had also drawn a hard line against Christmas and its myths. “I never wanted my kids to believe in Santa.” After Wevrick’s death, she became even more of a satellite, developing a deeper intolerance for life’s ordinary concerns.

    Making dinner seemed an insurmountable chore, the routine of school lunches a form of torture. The roof needed to be replaced, and she didn’t have the faintest idea how to get it fixed. She wasn’t sure how to swipe credit cards. If the answers to her questions weren’t somewhere on Wevrick’s three wrinkled sheets of paper, it could feel as though they were locked in a safe.

    There was a pendant light in her front hall, where the boys would fight with their toy lightsabers, and sometimes they would hit the light with their wild swings. Seager decided that either the light or one of the boys was going to end up damaged. She asked the widows how to do electrical work — “I have to parcel out things with logic and evidence,” she says — got out the ladder and took down the light, carefully wrapping black tape around the ends of the bare wires that now poked through the hole in the ceiling. She remembers thinking that her removing that light, all by herself, represented the height of her new accomplishment. She felt so reduced. She felt so gigantic.

    For all of her real and perceived strangeness, the most unusual thing about Seager is her blindness to her greatest gift. She is more than aware of her preternatural mathematical abilities, her possession of a rare mind that can see numbers and their functions as clearly as the rest of us see colors and shapes. “I’m good at that stuff,” she says with her brand of factual certainty that is sometimes confused with arrogance. She knows she is unusually capable of turning abstract concepts into things that can be packed into a case. What she doesn’t always see is her knack for connection between places if not always people, the unconventional grace she possesses when it comes to closing unfathomable distances.

    Seager has lined the hallway outside her office with a series of magical travel posters put out by the Jet Propulsion Laboratory. Each gives a glimpse of the alien worlds that, in part because of her, we now know exist. There’s a poster for Kepler-16b, an exoplanet that orbits a pair of stars, like Luke Skywalker’s home planet of Tatooine. Kepler-186f is depicted with red grass and red leaves on its trees, because its star is cooler and redder than the sun, which might influence photosynthesis in foliage-altering ways. There’s even one for PSO J318.5-22, a rogue planet that doesn’t orbit a star but instead wanders across the galaxy, cast in perpetual darkness, swept by rain of molten iron.

    After the discovery of Proxima Centauri b, Seager wrote a galactic postcard from it for the website Quartz. She closed her eyes and imagined a world 25 trillion miles away. “For the average earthling,” she wrote, “visiting this planet might not be much fun.” She saw a planet perhaps a third larger than Earth, with an orbit of only 11 days. Given its proximity to its small, red star, she suggested that the ultraviolet radiation on Proxima Centauri b is probably intense but the light Martian-dim. She also deduced that Proxima Centauri b is “tidally locked.” Like the moon’s relationship to Earth, one side of the planet always faces its star, which is always in the same place in its sky. Parts of Proxima Centauri b are cast in perpetual sunrise or sunset. One side is always in darkness.

    At first, after Wevrick’s death, Seager thought about abandoning her work, because she was having such a hard time with her responsibilities at home. Her dean talked her out of quitting, giving her financial support to hire caregivers for the boys and urging her to redouble her efforts. “I had worked so hard,” she says. “I had all the years I called the lost years with Mike when I ignored him. We had little tiny kids. I was working all the time, exhausted all the time. But I was like: We’ll have money some day. We’ll have time some day.”

    She paused. Her face was blank, emotionless. “Now I’ll cry.” Seconds later, tears spilled out of her eyes, and her voice modulated. “I wanted to make it up to him, and I never did.”

    Seager has always found comfort and perhaps even solace in her work, in her search for another and maybe better version of our world. In her mourning, each discovery represented one more avenue of escape. In the spring of 2013, she was given responsibility for the starshade. That July, she met a tall, fast-walking man named Charles Darrow.

    Darrow, who is now 53, was an amateur astronomer and the president of the Toronto branch of the Royal Astronomical Society of Canada, and at the last minute he decided to go to the society’s annual meeting in Thunder Bay, Ontario. Darrow was on his way out of a profoundly unhappy marriage; he worked for his family business, an engine-parts wholesaler. He needed a break, and he pointed his car north. “I wanted to be alone,” he says. At a reception on the Friday evening, Darrow noticed a hazel-eyed woman staring at him from across the room. “I thought she was looking at someone behind me,” he says. Then he went into the lecture hall, and the same woman was that night’s keynote speaker. She talked about exoplanets. The next day, lunch was in a university cafeteria. The woman was in the salad line ahead of him, and she turned around. Darrow mustered up his courage and invited Sara Seager to join him. “I knew about five minutes into the conversation that my life was going to change,” he says.

    Seager was taken with Darrow the night she saw him in Thunder Bay. She had been struck by the contrast between the whiteness of his shirt and his tanned summer skin. But she didn’t have the same certainty that possessed him at their lunch the next day. She wasn’t sure how to develop a relationship across the 549 miles between her home in Concord and his home outside Toronto. She thought they might never cross paths again.

    They might not have, except Darrow resolved during his drive back home that he had to call her. He picked up the phone five times but always hung up before she answered. On the sixth, he spoke to her, beginning a long correspondence, emails and conversations over Skype. Darrow and Seager talked every way but face to face. They fell in love remotely. “I had to follow my heart,” Darrow says. “I decided that I wasn’t going to die unhappy.”

    Melissa, meanwhile, told Seager that if she could close the gap between here and a planet like Kepler-186f — a journey that would take us 500 light-years to complete — then the 549 miles between Concord and Toronto shouldn’t seem like such an insurmountable gulf. By her usual measures, he was right next door.

    Seager and Darrow married in April 2015. In different ways, each had rescued the other. Seager was the cataclysm that allowed Darrow to make every correction. He divorced, left his family business and moved into a pretty yellow Victorian in Concord. The two boys started calling him dad. For Seager, Darrow was a second chance to know love, even deeper than the one she had known, because it seemed so improbable in her sadness. “I feel so lucky to have found him,” Seager says. “What are the chances?”

    Adapting to his new life hasn’t always been easy for Darrow. He is determined, as he puts it, “to make Sara the happiest woman in the multiverse.” He cooks dinner; he helps take care of the boys; he maintains the house; he walks with Seager to the train station every morning, and he picks her up every night. He has chosen to take care of the mundane so that she can devote herself to the extraordinary. But he banged his head more than once on Wevrick’s canoe, which still hung from the back of the garage.

    Not long ago, Darrow was looking for the right ways to assert his presence, to make a claim to a house that didn’t always feel like his. The wires dangling from the front hall ceiling bothered him. They looked bad and seemed dangerous. A few months after his arrival in Concord, he took his opening. He carved out some of the plaster, installed a plastic box, ran the wires through it and hooked up a new fixture, flush mounted, so that the boys wouldn’t hit it during their duels.

    Darrow climbed down from the ladder and flicked the switch.

    The morning after she forgot her phone, Seager woke up and decided, just like that, to skip the commute. With the house to herself, she tried to make coffee. She left out part of the machine, and after some terrible noises, the pot was bone dry. She sat down at her kitchen table with her empty mug and began talking about hundreds of billions of galaxies and their hundreds of billions of stars. Tens of billions of habitable planets, far more of them than there are people on Earth. There has to be other life somewhere out there. We can’t be that special.

    “It would be arrogant to think so,” Seager said. But in her lifetime, after the Wfirst telescope rockets into orbit, and maybe her starshade follows it — she puts the chances of success at 85 percent — she will have time to explore only the nearest hundred stars or so. A hundred stars out of all those lights in the sky, a fraction of a fraction of a fraction.

    Will one of them have a small, rocky planet like Earth? Probably. Will one of those small, rocky planets have liquid water on it? Possibly. Will the planet sustain life? Now the odds tilt. Now they are working against her, and she knows it. Now they’re maybe one in a million that she’ll find what she’s looking for.

    She did some private math. “I believe,” she said.

    Seager’s discovery will be fate-altering if it comes, but it will also be quiet, a few pixels on a screen. It will obey the laws of physics. It will be a probability equation: What are the chances? We won’t discover that there is life on other planets the way we’ve been taught that we’ll learn. There won’t be some great mother ship descending from the sky over Johannesburg or a bizarre lightning storm that monsters will ride to New Jersey. What Seager will have is a photograph from a space telescope of a distant solar system, with its star eclipsed by her starshade, and with a familiar blue dot some safe and survivable distance away from it. That’s all the evidence she will have that we’re not alone, and that will be all the evidence she will need. Her proof of life will be a small light where there wasn’t one before.

    See the full article here .

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  • richardmitnick 1:48 pm on November 29, 2016 Permalink | Reply
    Tags: , Exoplanet research, How to take pictures of exoplanets,   

    From AURA via The Economist: “How to take pictures of exoplanets” 

    AURA Icon
    Association of Universities for Research in Astronomy

    1

    The Economist

    1

    Nov 26th 2016
    No writer credit found.

    IN THE quarter of a century since the first extrasolar planets were discovered, astronomers have turned up more than 3,500 others. They are a diverse bunch. Some are baking-hot gas giants that zoom around their host stars in days. Some are entirely covered by oceans dozens of kilometres deep. Some would tax even a science-fiction writer’s imagination. One, 55 Cancri e, seems to have a graphite surface and a diamond mantle. At least, that is what astronomers think. They cannot be sure, because the two main ways exoplanets are detected—by measuring the wobble their gravity causes in their host stars, or by noting the slight decline in a star’s brightness as a planet passes in front of it—yield little detail.

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

    Using them, astronomers can infer such basics as a planet’s size, mass and orbit. Occasionally, they can interrogate starlight that has traversed a planet’s atmosphere about the chemistry of its air. All else is informed conjecture.

    What would help is the ability to take pictures of planets directly. Such images could let astronomers deduce a world’s surface temperature, analyse what that surface is made from and even—if the world were close enough and the telescope powerful enough—get a rough idea of its geography. Gathering the light needed to create such images is hard. The first picture of an extrasolar world, 2M1207b, 170 light-years away, was snapped in 2004, but the intervening dozen years have seen only a score or so of others join it in the album. That should soon change, though, as new instruments both on the ground and in space add to the tally. And a few of the targets of these telescopes may be the sorts of planets that have the best chance of supporting life, namely Earth-sized worlds at the right distance from sun-like stars, in what are known as those stars’ habitable zones—places where heat from the star might be expected to stop water freezing without actually boiling it.

    Smile, please

    Taking pictures of exoplanets is hard for two reasons. One is their distance. The other is that they are massively outshone by their host stars.

    Interstellar distances do not just make objects faint. They also reduce the apparent gap between a planet and its host, so that it is hard to separate the two in a photograph. Such apparent gaps are measured in units called arc-seconds (an arc-second is a 3,600th of a degree). This is about the size of an American dime seen from four kilometres away. The exoplanet closest to Earth orbits Proxima Centauri, the sun’s stellar neighbour.

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker
    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    Yet despite its proximity (4.25 light-years) the angular gap between this planet and its star is a mere 0.038 arc-seconds, according to Beth Biller, an exoplanet specialist at the University of Edinburgh. Separating objects which appear this close together requires a pretty big telescope.

    The second problem, glare, is best dealt with by inserting an opaque disc called a coronagraph into a telescope’s optics.

    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile
    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile

    A coronagraph’s purpose is to block light coming directly from a star while permitting any that is reflected from planets orbiting that star to shine through. This palaver is necessary because, as a common analogy puts it, photographing an exoplanet is like trying to take a picture, from thousands of kilometres away, of a firefly buzzing around a lighthouse. Seen from outside the solar system, Earth would appear to be a ten-billionth as bright as the sun.

    Those exoplanets that have had their photographs taken so far are ones for which these problems are least troublesome—gigantic orbs (which thus reflect a lot of light) circling at great distances (maximising angular separation) from dim hosts (minimising glare). In addition, these early examples of planetary photography have usually involved young worlds that are still slightly aglow with the heat of their formation. Even then, serious hardware is required. For example, four giant planets circling a star called HR8799 were snapped between 2008 and 2010 by the Keck and Gemini telescopes on Hawaii (see picture).

    4

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory Interior
    Keck Observatory, Mauna Kea, Hawaii, USA

    Gemini/North telescope at Mauna Kea, Hawaii, USA
    Gemini North Interior
    Gemini/North telescope at Mauna Kea, Hawaii, USA

    These instruments have primary mirrors that are, respectively, ten metres and 8.1 metres across. The good news for planet-snappers is that such giant telescopes are becoming more common, and that people are building special planet-photographing cameras to fit on them.

    At the moment, the three most capable are the Gemini Planet Imager, attached to the southern Gemini telescope, in Chile; the Spectro-Polarimetric High-Contrast Exoplanet Research Instrument on the Very Large Telescope, a European machine also in Chile; and the Subaru Coronagraphic Extreme Adaptive Optics Device on the Subaru telescope, a Japanese machine on Hawaii.

    NOAO Gemini Planet Imager on Gemini South
    NOAO Gemini Planet Imager on Gemini South

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile
    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile

    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile
    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile

    ESO/VLT at Cerro Paranal, Chile
    ESO/VLT at Cerro Paranal, Chile

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    Picture of SCExAO installed on the IR Nasmyth platform of the Subaru Telescope. SCExAO sits between the facility Adaptive Optics system called AO188 . Frantz Martinache

    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA
    NAOJ Subaru Telescope interior
    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA

    All of those telescopes sport a mirror more than eight metres across, making them some of the biggest in the world, and their planet-photographing attachments are fitted with the most sophisticated coronagraphs available. The result is that the Subaru device, for example, can take pictures of giant planets that orbit their stars slightly closer in than Jupiter orbits the sun.

    This improved sensitivity will let astronomers take pictures of many more worlds. The Gemini Planet Imager, for instance, is looking for planets around 600 promising stars. (Its first discovery was announced in August 2015.) But even these behemoths will still be limited to photographing gas giants. To take snaps of the next-smallest class of planets (so-called “ice giants” like Neptune and Uranus), and the class after that (large, rocky planets called “super-Earths” that have no analogue in the solar system), will require even more potent instruments.

    These are coming. The European Extremely Large Telescope (ELT) is currently under construction in the Chilean mountains.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile
    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile

    Its 39.3 metre mirror will be nearly four times the diameter of the present record-holder, the Gran Telescopio Canarias, in the Canary Islands, which has a mirror 10.4 metres across.

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

    When it is finished, in 2024, the ELT should be sensitive enough to photograph Proxima Centauri’s planet, as well as other rocky ones around nearby stars. A smaller instrument, with a 24.5 metre mirror, the Giant Magellan Telescope, should be finished in 2021.

    Giant Magellan Telescope, Las Campanas Observatory, to be built  some 115 km (71 mi) north-northeast of La Serena, Chile
    Giant Magellan Telescope, Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile

    The Thirty Metre Telescope, planned for Hawaii, will, as its name suggests, fall somewhere between those two—though its construction has been halted by legal arguments.

    TMT-Thirty Meter Telescope, proposed for Mauna Kea, Hawaii, USA
    TMT-Thirty Meter Telescope, proposed for Mauna Kea, Hawaii, USA

    For ground-based telescopes that may be the end of the line, says Matt Mountain, who is president of the Association of Universities for Research in Astronomy, and who oversaw the construction of the Gemini telescopes. The shifting currents of Earth’s atmosphere (the reason stars seem to twinkle even to the naked eye) impose limits on how good they can ever be as planetary cameras. To get around those limits means going into space. Although it is not specifically designed for the job, the James Webb space telescope, which is scheduled for launch in 2018 and which boasts both a mirror 6.5 metres across and a reasonably capable coronagraph, should be able to snap pictures of some large, nearby worlds.

    NASA/ESA/CSA Webb Telescope annotated
    NASA/ESA/CSA Webb Telescope annotated

    It will be able to sniff the atmospheres of many more, analysing starlight that has passed through those atmospheres on its way to Earth. WFIRST, a space telescope due to launch in the mid-2020s, will have picture-taking capabilities of its own, and will serve to test the latest generation of coronagraphs.

    NASA/WFIRST
    NASA/WFIRST

    After that, astronomers who want to picture truly Earth-like worlds are pinning their hopes on a set of ambitious missions which, for now, exist only as proposal documents in NASA’s in-tray. One of the most intriguing is the New Worlds Mission. This hopes to launch a giant occulter (in effect, an external coronagraph) that would fly in formation with an existing space telescope (probably the James Webb) to boost its exoplanet-imaging prowess.

    Small is beautiful

    There may, though, be an alternative to this big-machine approach. That is the belief of the members of a team of researchers led by Jon Morse, formerly director of astrophysics at NASA. Project Blue, as this team calls itself, hopes, using a mixture of private grants, taxpayers’ money and donations from the public, to pay for a space telescope costing $50m (as opposed, for example, to the $9 billion budgeted for the James Webb) that would try to take pictures of any Earth-like exoplanets orbiting in the habitable zone of Alpha Centauri A—the closest sun-like star to Earth, and a big brother to Proxima Centauri.

    Alpha Centauri is hotter than Proxima, which means its habitable zone is much further away. That, combined with its closeness, means Project Blue can get away with a mirror between 30 and 45cm across—the size of mirror an enthusiastic amateur might have in his telescope. What such an amateur would not have, though, is a computer-run “multi-star wavefront controlled” mirror. This will draw on a technology already fitted to ground-based telescopes, called adaptive optics, in which portions of the mirror are subtly deformed in order to sculpt incoming light.

    In combination with a coronagraph the wavefront controller will, according to Supriya Chakrabarti of the University of Massachusetts, Lowell, let the telescope blot out the light not only of Alpha Centauri A, but also of Alpha Centauri B, a companion even closer to it than Proxima Centauri is. Moreover, the plan is to take thousands of pictures over the course of several years. By combining these and looking for persistent signals—particularly ones that appear to follow plausible orbits—computers should be able to pluck any planets from the noise.

    If it works, Alpha Centauri A’s closeness means Project Blue’s telescope could reveal lots of information about any planets orbiting that star (and statistical analysis of known exoplanets suggests there will almost certainly be some). Examining the spectrum of light from them would reveal what their atmospheres and surfaces were made from, including any chemicals—such as oxygen and methane—that might suggest the presence of life. It might even be possible to detect vegetation, or its alien equivalent, directly. The length of a planet’s day could be inferred by watching for regular changes in light as its revolution about its axis caused continents and seas to become alternately visible and invisible. Longer-term variations might reveal planetary seasons; shorter-term, more chaotic ones might be evidence of weather.

    If they can raise the money in time, the Project Blue team hope to launch their telescope in 2019 or 2020. Being able to take a picture of a rocky planet around one of the sun’s nearest neighbours would be an enormous scientific prize. If a habitable planet were found, it would be one of the biggest scientific discoveries of the century. Donors may think that worth a punt.

    See the full article here .

    Please help promote STEM in your local schools.

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    The Association of Universities for Research in Astronomy (AURA) is a consortium of 42 US institutions and 5 international affiliates that operates world-class astronomical observatories. AURA’s role is to establish, nurture, and promote public observatories and facilities that advance innovative astronomical research. In addition, AURA is deeply committed to public and educational outreach, and to diversity throughout the astronomical and scientific workforce. AURA carries out its role through its astronomical facilities.

    Our mission

    “To promote excellence in astronomical research by providing access to information about the universe from state-of-the-art facilities, surveys, and archives”

    Our facilities

    Gemini Observatory
    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile
    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile
    Gemini/North telescope at Manua Kea, Hawaii, USA
    Gemini/North telescope at Manua Kea, Hawaii, USA
    Large Synoptic Survey Telescope (LSST)
    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
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    LSST telescope, currently under construction at Cerro Pachón Chile
    LSST telescope, currently under construction at Cerro Pachón Chile
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  • richardmitnick 1:26 pm on November 9, 2016 Permalink | Reply
    Tags: A New Planetary Architecture: Hot Earths, , Exoplanet research, Hot earths   

    From astrobites- “A New Planetary Architecture: Hot Earths” 

    Astrobites bloc

    Astrobites

    Nov 9, 2016
    Joseph Schmitt

    Title: A population of planetary systems characterized by short-period, Earth-sized planets
    Authors: Jason H. Steffen and Jeffrey L. Coughlin
    First Author’s Institution: University of Nevada, Las Vegas
    Status: Published in the Proceedings of the National Academy of Sciences (PNAS)

    The Kepler space telescope has discovered just over 2500 exoplanets to date, which is more than 70% of all exoplanets found so far. It has discovered planets and systems vastly different from what we see in our own solar system, such as Super Earths and tightly packed planetary systems. While both of these are quite easy to visually recognize in the data, other types of systems might not be so apparently obvious. The authors of this paper claim to discover one such hidden planetary architecture: a population of systems whose main signature is having a short-period (~1 day), Earth-sized planet.

    Single Transit Systems

    There are multiple types of planetary systems that Kepler has observed that can have a single observed transiting planet. Hot Jupiter systems are one such class, which is characterized by a massive, short-period planet which rarely has other planets observed in the system. This is caused by its unique, destructive formation mechanism, where the planet migrates inward through the protoplanetary disk or is scattered inward by near collisions with other planets, which disrupts the inner planetary system. Another type of single transiting system is merely a result of observational bias in the transit system. If a system with multiple planets is tilted relative to Earth, or if the planets are not perfectly aligned in a flat plane, sometimes only one planet will be observed to transit.

    The authors test the observed orbital period-planet radius distribution of planets to see if the number of single transiting systems can be explained simply by the observational bias of tilted or misaligned planetary systems. They do this by attempting to reproduce the distribution of single transiting systems by randomly drawing one planet from the multiplanet systems. If the randomly drawn planets match the distribution of single transiting systems, then it’s likely that the single transiting systems are similar to the multiplanet systems, but with just one of the planets transiting. However, any regions in the period-radius diagram for single transiting planets that do not match the random draws from multiplanet systems could indicate the existence of a different class of planetary system altogether.

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    Figure 1: The period-radius distribution for single transiting systems (top) and multiplanet systems (bottom). Taking the difference of these two plots effectively highlights regions of period-radius space where the single transiting systems cannot be reproduced by randomly sampling a single planet from the multiplanet systems.

    This experiment produced four regions where the period-radius distribution of planets randomly drawn from a multiplanet system did not match the distribution of single transiting systems. One of these four regions is the Hot Jupiters, and two other regions can be explained away by biases and inherent deficiencies in this technique. However, one region cannot be explained away: short-period, Earth-sized planets, dubbed “Hot Earths”.

    Origins of Hot Earth candidates

    The authors identify four potential origins of the Hot Earth candidates in the Kepler data.

    1.Statistical false positives: the candidates are simply caused by fluctuations in the measured starlight that look like transits. Out of 146 Hot Earth candidates, further analysis shows only two that are likely to be statistical false positives.
    2.Astrophysical false positives: the candidates are actually caused by an unresolved eclipsing binary in the background of the pixel. Using knowledge of the binary rate and the density of stars in the region near the star, they expect only 3% of the 144 Hot Earth candidates to be an astrophysical false positive.
    3. Systems with undetected distant planets: the candidates are just the innermost planet of multiplanet systems where the outer planets aren’t detected. For each Hot Earth candidate, the authors simulated outer planets that are similar in nature to the multiplanet systems that also have a Hot Earth. From their simulations, they found that an average of 77 Hot Earths could be explained by this, with an upper limit of 112.
    4. Isolated Hot Earths: the candidates are truly alone, or the outer planets are significantly farther away or more inclined than typical multiplanet systems. By process of elimination, there are about 24 Hot Earths fitting this category, or about 17% of the total sample of Hot Earth candidates.

    Isolated Hot Earth Formation

    If there truly is an excess of Hot Earths, there are a few potential causes. They could be the evaporated cores of Hot Jupiters. If true, this would nearly double the Hot Jupiter rate. Conversely, two other scenarios have these planets starting out at approximately their current mass, but farther out in the system. In one scenario, the planet migrates inward during planet formation until it hits the inner edge of the protoplanetary disk, where it stops. In the other scenario, dynamical and gravitational interactions between planets can drive the innermost planet very close to the star.

    If these Hot Earth systems are real, this adds another complication (and another test) for planetary formation models, which now need to also explain this new type of planetary architecture.

    See the full article here .

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    What do we do?

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

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

     
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