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  • richardmitnick 9:39 pm on May 13, 2021 Permalink | Reply
    Tags: "Mixing Massive Stars", , , , , NASA Kepler and K2, , ,   

    From University of California-Santa Barbara (US) : “Mixing Massive Stars” 

    UC Santa Barbara Name bloc

    From University of California-Santa Barbara (US)

    May 13, 2021
    Harrison Tasoff
    (805) 893-7220
    harrisontasoff@ucsb.edu

    1
    A simulation of a 3-solar-mass star shows the central, convective core and the waves it generates in the rest of the star’s interior. Photo Credit: Philipp Edelmann.

    Astronomers commonly refer to massive stars as the chemical factories of the Universe. They generally end their lives in spectacular supernovae, events that forge many of the elements on the periodic table. How elemental nuclei mix within these enormous stars has a major impact on our understanding of their evolution prior to their explosion. It also represents the largest uncertainty for scientists studying their structure and evolution.

    A team of astronomers led by May Gade Pedersen, a postdoctoral scholar at UC Santa Barbara’s Kavli Institute for Theoretical Physics, have now measured the internal mixing within an ensemble of these stars using observations of waves from their deep interiors. While scientists have used this technique before, this paper marks the first time this has been accomplished for such a large group of stars at once. The results, published in Nature Astronomy, show that the internal mixing is very diverse, with no clear dependence on a star’s mass or age.

    Stars spend the majority of their lives fusing hydrogen into helium deep in their cores. However, the fusion in particularly massive stars is so concentrated at the center that it leads to a turbulent convective core similar to a pot of boiling water. Convection, along with other processes like rotation, effectively removes helium ash from the core and replaces it with hydrogen from the envelope. This enables the stars to live much longer than otherwise predicted.

    Astronomers believe this mixing arises from various physical phenomena, like internal rotation and internal seismic waves in the plasma excited by the convecting core. However, the theory has remained largely unconstrained by observations as it occurs so deep within the star. That said, there is an indirect method of peering into stars: asteroseismology, the study and interpretation of stellar oscillations. The technique has parallels to how seismologists use earthquakes to probe the interior of the Earth.

    “The study of stellar oscillations challenges our understanding of stellar structure and evolution,” Pedersen said. “They allow us to directly probe the stellar interiors and make comparisons to the predictions from our stellar models.”

    Pedersen and her collaborators from Katholieke Universiteit Leuven [Katholieke Universiteit te Leuven] (BE), the Hasselt University [Universiteit Hasselt] (BE), and the The University of Newcastle (AU) have been able to derive the internal mixing for an ensemble of such stars using asteroseismology. This is the first time such a feat has been achieved, and was possible thanks only to a new sample of 26 slowly pulsating B-type stars with identified stellar oscillations from NASA’s Kepler mission.

    2
    Mixing transports fused material away and replaces it with more hydrogen fuel from the star’s outer layers.
    Credit: MAY GADE PEDERSEN.

    Slowly pulsating B-type stars are between three and eight times more massive than the Sun. They expand and contract on time scales of the order of 12 hours to 5 days, and can change in brightness by up to 5%. Their oscillation modes are particularly sensitive to the conditions near the core, Pedersen explained.

    “The internal mixing inside stars has now been measured observationally and turns out to be diverse in our sample, with some stars having almost no mixing while others reveal levels a million times higher,” Pedersen said. The diversity turns out to be unrelated to the mass or age of the star. Rather, it’s primarily influenced by the internal rotation, though that is not the only factor at play.

    “These asteroseismic results finally allow astronomers to improve the theory of internal mixing of massive stars, which has so far remained uncalibrated by observations coming straight from their deep interiors,” she added.

    The precision at which astronomers can measure stellar oscillations depends directly on how long a star is observed. Increasing the time from one night to one year results in a thousand-fold increase in the measured precision of oscillation frequencies.

    “May and her collaborators have really shown the value of asteroseismic observations as probes of the deep interiors of stars in a new and profound way,” said KITP Director Lars Bildsten, the Gluck Professor of Theoretical Physics. “I am excited to see what she finds next.”

    The best data currently available for this comes from the Kepler space mission, which observed the same patch of the sky for four continuous years. The slowly pulsating B-type stars were the highest mass pulsating stars that the telescope observed. While most of these are slightly too small to go supernova, they do share the same internal structure as the more massive stellar chemical factories. Pedersen hopes insights gleaned from studying the B type stars will shed light on the inner workings of their higher mass, O type counterparts.

    She plans to use data from NASA’s Transiting Exoplanet Survey Satellite (TESS) to study groups of oscillating high-mass stars in OB associations.

    National Aeronautics Space Agency (US)/Massachusetts Institute of Technology (US) TESS

    Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Center for Astrophysics – Harvard and Smithsonian; MIT Lincoln Laboratory; and the NASA Space Telescope Science Institute (US) in Baltimore.

    These groups comprise 10 to more than 100 massive stars between 3 and 120 solar masses. Stars in OB associations are born from the same molecular cloud and share similar ages, she explained. The large sample of stars, and constraint from their common ages, provides exciting new opportunities to study the internal mixing properties of high-mass stars.

    In addition to unveiling the processes hidden within stellar interiors, research on stellar oscillations can also provide information on other properties of the stars.

    “The stellar oscillations not only allow us to study the internal mixing and rotation of the stars, but also determine other stellar properties such as mass and age,” Pedersen explained. “While these are both two of the most fundamental stellar parameters, they are also some of the most difficult to measure.”

    See the full article here .


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    UC Santa Barbara Seal

    The University of California-Santa Barbara (US) is a public land-grant research university in Santa Barbara, California, and one of the ten campuses of the University of California(US) system. Tracing its roots back to 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944, and is the third-oldest undergraduate campus in the system.

    The university is a comprehensive doctoral university and is organized into five colleges and schools offering 87 undergraduate degrees and 55 graduate degrees. It is classified among “R1: Doctoral Universities – Very high research activity”. According to the National Science Foundation(US), UC Santa Barbara spent $235 million on research and development in fiscal year 2018, ranking it 100th in the nation. In his 2001 book The Public Ivies: America’s Flagship Public Universities, author Howard Greene labeled UCSB a “Public Ivy”.

    UC Santa Barbara is a research university with 10 national research centers, including the Kavli Institute for Theoretical Physics (US) and the Center for Control, Dynamical-Systems and Computation. Current UCSB faculty includes six Nobel Prize laureates; one Fields Medalist; 39 members of the National Academy of Sciences; 27 members of the National Academy of Engineering; and 34 members of the American Academy of Arts and Sciences. UCSB was the No. 3 host on the ARPANET and was elected to the Association of American Universities in 1995. The faculty also includes two Academy and Emmy Award winners and recipients of a Millennium Technology Prize; an IEEE Medal of Honor; a National Medal of Technology and Innovation; and a Breakthrough Prize in Fundamental Physics.

    The UC Santa Barbara Gauchos compete in the Big West Conference of the NCAA Division I. The Gauchos have won NCAA national championships in men’s soccer and men’s water polo.

    History

    UCSB traces its origins back to the Anna Blake School, which was founded in 1891, and offered training in home economics and industrial arts. The Anna Blake School was taken over by the state in 1909 and became the Santa Barbara State Normal School which then became the Santa Barbara State College in 1921.

    In 1944, intense lobbying by an interest group in the City of Santa Barbara led by Thomas Storke and Pearl Chase persuaded the State Legislature, Gov. Earl Warren, and the Regents of the University of California to move the State College over to the more research-oriented University of California system. The State College system sued to stop the takeover but the governor did not support the suit. A state constitutional amendment was passed in 1946 to stop subsequent conversions of State Colleges to University of California campuses.

    From 1944 to 1958, the school was known as Santa Barbara College of the University of California, before taking on its current name. When the vacated Marine Corps training station in Goleta was purchased for the rapidly growing college Santa Barbara City College moved into the vacated State College buildings.

    Originally the regents envisioned a small several thousand–student liberal arts college a so-called “Williams College (US) of the West”, at Santa Barbara. Chronologically, UCSB is the third general-education campus of the University of California, after UC Berkeley (US) and UCLA (US) (the only other state campus to have been acquired by the UC system). The original campus the regents acquired in Santa Barbara was located on only 100 acres (40 ha) of largely unusable land on a seaside mesa. The availability of a 400-acre (160 ha) portion of the land used as Marine Corps Air Station Santa Barbara until 1946 on another seaside mesa in Goleta, which the regents could acquire for free from the federal government, led to that site becoming the Santa Barbara campus in 1949.

    Originally only 3000–3500 students were anticipated but the post-WWII baby boom led to the designation of general campus in 1958 along with a name change from “Santa Barbara College” to “University of California, Santa Barbara,” and the discontinuation of the industrial arts program for which the state college was famous. A chancellor- Samuel B. Gould- was appointed in 1959.

    In 1959 UCSB professor Douwe Stuurman hosted the English writer Aldous Huxley as the university’s first visiting professor. Huxley delivered a lectures series called The Human Situation.

    In the late ’60s and early ’70s UCSB became nationally known as a hotbed of anti–Vietnam War activity. A bombing at the school’s faculty club in 1969 killed the caretaker Dover Sharp. In the spring of 1970 multiple occasions of arson occurred including a burning of the Bank of America branch building in the student community of Isla Vista during which time one male student Kevin Moran was shot and killed by police. UCSB’s anti-Vietnam activity impelled then-Gov. Ronald Reagan to impose a curfew and order the National Guard to enforce it. Armed guardsmen were a common sight on campus and in Isla Vista during this time.

    In 1995 UCSB was elected to the Association of American Universities– an organization of leading research universities with a membership consisting of 59 universities in the United States (both public and private) and two universities in Canada.

    On May 23, 2014 a killing spree occurred in Isla Vista, California, a community in close proximity to the campus. All six people killed during the rampage were students at UCSB. The murderer was a former Santa Barbara City College student who lived in Isla Vista.

    Research activity

    According to the National Science Foundation (US), UC Santa Barbara spent $236.5 million on research and development in fiscal 2013, ranking it 87th in the nation.

    From 2005 to 2009 UCSB was ranked fourth in terms of relative citation impact in the U.S. (behind Massachusetts Institute of Technology (US), California Institute of Technology(US), and Princeton University (US)) according to Thomson Reuters.

    UCSB hosts 12 National Research Centers, including the Kavli Institute for Theoretical Physics, the National Center for Ecological Analysis and Synthesis, the Southern California Earthquake Center, the UCSB Center for Spatial Studies, an affiliate of the National Center for Geographic Information and Analysis, and the California Nanosystems Institute. Eight of these centers are supported by the National Science Foundation. UCSB is also home to Microsoft Station Q, a research group working on topological quantum computing where American mathematician and Fields Medalist Michael Freedman is the director.

    Research impact rankings

    The Times Higher Education World University Rankings ranked UCSB 48th worldwide for 2016–17, while the Academic Ranking of World Universities (ARWU) in 2016 ranked UCSB 42nd in the world; 28th in the nation; and in 2015 tied for 17th worldwide in engineering.

    In the United States National Research Council rankings of graduate programs, 10 UCSB departments were ranked in the top ten in the country: Materials; Chemical Engineering; Computer Science; Electrical and Computer Engineering; Mechanical Engineering; Physics; Marine Science Institute; Geography; History; and Theater and Dance. Among U.S. university Materials Science and Engineering programs, UCSB was ranked first in each measure of a study by the National Research Council of the NAS.

    The Centre for Science and Technologies Studies at

     
  • richardmitnick 12:20 pm on January 24, 2020 Permalink | Reply
    Tags: "NASA's Kepler Witnesses Vampire Star System Undergoing Super-Outburst", , , , , , NASA Kepler and K2   

    From NASA/ESA Hubble Telescope and NASA/Kepler: “NASA’s Kepler Witnesses Vampire Star System Undergoing Super-Outburst” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope


    From NASA/ESA Hubble Telescope

    and

    NASA Kepler Logo

    NASA Kepler Telescope
    From NASA/Kepler

    January 24, 2020

    Christine Pulliam
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4366
    cpulliam@stsci.edu

    Ryan Ridden-Harper
    Space Telescope Science Institute, Baltimore, Maryland, and
    Australian National University, Canberra, Australia
    rridden@stsci.edu

    1
    NASA and L. Hustak

    This illustration shows a newly discovered dwarf nova system, in which a white dwarf star is pulling material off a brown dwarf companion. The material collects into an accretion disk until reaching a tipping point, causing it to suddenly increase in brightness. Using archival Kepler data, a team observed a previously unseen, and unexplained, gradual intensification followed by a super-outburst in which the system brightened by a factor of 1,600 over less than a day.

    Archival data reveals earliest stages of a dramatic event

    Astronomers searching archival data from NASA’s Kepler exoplanet hunting mission identified a previously unknown dwarf nova that underwent a super-outburst, brightening by a factor of 1,600 times in less than a day. While the outburst itself has a theoretical explanation, the slow rise in brightness that preceded it remains a mystery. Kepler’s rapid cadence of observations were crucial for recording the entire event in detail.

    The dwarf nova system consists of a white dwarf star with a brown dwarf companion. The white dwarf is stripping material from the brown dwarf, sucking its essence away like a vampire. The stripped material forms an accretion disk around the white dwarf, which is the source of the super-outburst. Such systems are rare and may go for years or decades between outbursts, making it a challenge to catch one in the act.

    NASA’s Kepler spacecraft was designed to find exoplanets by looking for stars that dim as a planet crosses the star’s face. Fortuitously, the same design makes it ideal for spotting other astronomical transients – objects that brighten or dim over time. A new search of Kepler archival data has uncovered an unusual super-outburst from a previously unknown dwarf nova. The system brightened by a factor of 1,600 over less than a day before slowly fading away.

    The star system in question consists of a white dwarf star with a brown dwarf companion about one-tenth as massive as the white dwarf. A white dwarf is the leftover core of an aging Sun-like star and contains about a Sun’s worth of material in a globe the size of Earth. A brown dwarf is an object with a mass between 10 and 80 Jupiters that is too small to undergo nuclear fusion.

    The brown dwarf circles the white dwarf star every 83 minutes at a distance of only 250,000 miles (400,000 km) – about the distance from Earth to the Moon. They are so close that the white dwarf’s strong gravity strips material from the brown dwarf, sucking its essence away like a vampire. The stripped material forms a disk as it spirals toward the white dwarf (known as an accretion disk).

    It was sheer chance that Kepler was looking in the right direction when this system underwent a super-outburst, brightening by more than 1,000 times. In fact, Kepler was the only instrument that could have witnessed it, since the system was too close to the Sun from Earth’s point of view at the time. Kepler’s rapid cadence of observations, taking data every 30 minutes, was crucial for catching every detail of the outburst.

    The event remained hidden in Kepler’s archive until identified by a team led by Ryan Ridden-Harper of the Space Telescope Science Institute (STScI), Baltimore, Maryland, and the Australian National University, Canberra, Australia. “In a sense, we discovered this system accidentally. We weren’t specifically looking for a super-outburst. We were looking for any sort of transient,” said Ridden-Harper.

    Kepler captured the entire event, observing a slow rise in brightness followed by a rapid intensification. While the sudden brightening is predicted by theories, the cause of the slow start remains a mystery. Standard theories of accretion disk physics don’t predict this phenomenon, which has subsequently been observed in two other dwarf nova super-outbursts.

    “These dwarf nova systems have been studied for decades, so spotting something new is pretty tricky,” said Ridden-Harper. “We see accretion disks all over – from newly forming stars to supermassive black holes – so it’s important to understand them.”

    Theories suggest that a super-outburst is triggered when the accretion disk reaches a tipping point. As it accumulates material, it grows in size until the outer edge experiences gravitational resonance with the orbiting brown dwarf. This might trigger a thermal instability, causing the disk to get superheated. Indeed, observations show that the disk’s temperature rises from about 5,000–10,000° F (2,700–5,300° C) in its normal state to a high of 17,000–21,000° F (9,700–11,700° C) at the peak of the super-outburst.

    This type of dwarf nova system is relatively rare, with only about 100 known. An individual system may go for years or decades between outbursts, making it a challenge to catch one in the act.

    “The detection of this object raises hopes for detecting even more rare events hidden in Kepler data,” said co-author Armin Rest of STScI.

    The team plans to continue mining Kepler data, as well as data from another exoplanet hunter, the Transiting Exoplanet Survey Satellite (TESS) mission, in search of other transients.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    “The continuous observations by Kepler/K2, and now TESS, of these dynamic stellar systems allows us to study the earliest hours of the outburst, a time domain that is nearly impossible to reach from ground-based observatories,” said Peter Garnavich of the University of Notre Dame in Indiana.

    This work was published in the Oct. 21, 2019 issue of the Monthly Notices of the Royal Astronomical Society.

    The Space Telescope Science Institute is expanding the frontiers of space astronomy by hosting the science operations center of the Hubble Space Telescope, the science and operations center for the James Webb Space Telescope, and the science operations center for the future Wide Field Infrared Survey Telescope (WFIRST). STScI also houses the Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Kepler, K2, TESS missions and more.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST

    STScI also houses the Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Kepler, K2, TESS missions and more.

    See the full article here .


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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    ESA50 Logo large

     
  • richardmitnick 5:42 pm on January 8, 2020 Permalink | Reply
    Tags: "NASA’s new exoplanet hunter found its first potentially habitable world", , , , , , NASA Kepler and K2, , Planet TOI 700 d   

    From MIT Technology Review: “NASA’s new exoplanet hunter found its first potentially habitable world” 

    MIT Technology Review
    From MIT Technology Review

    1.8.20
    Neel V. Patel

    1
    TOI 700 d

    NASA’s Transiting Exoplanet Survey Satellite (TESS) has just found a new potentially habitable exoplanet the size of Earth, located about 100 light-years away. It’s the first potentially habitable exoplanet the telescope has found since it was launched in April 2018.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    It’s called TOI 700 d [science paper https://arxiv.org/abs/2001.00952 ]. It orbits a red dwarf star about 40% less massive than the sun and half as cool. The planet itself is about 1.2 times the size of Earth and orbits the host star every 37 days, receiving close to 86% of the amount of sunlight Earth does.

    Most notably, TOI 700 d is in what’s thought to be its star’s habitable zone, meaning it’s at a distance where temperatures ought to be moderate enough to support liquid water on the surface. This raises hopes TOI 700 d could be amenable to life—even though no one can agree on what it means for a planet to be habitable.

    A set of 20 different simulations meant to model TOI 700 d suggest the planet is rocky and has an atmosphere that helps it retain water, but there’s a chance it might simply be a gaseous mini-Neptune. We won’t know for sure until follow-up observations are made with some sharper instruments, such as the upcoming James Webb Space Telescope, which is planned for launch in March 2021.

    NASA/ESA/CSA Webb Telescope annotated

    TESS finds exoplanets using the tried-and-true technique of looking for objects as they’re transiting in front of their host stars.

    Planet transit. NASA/Ames

    Data from NASA’s Spitzer Space Telescope was also used to get some closer measurements of the planet’s size and orbit.

    NASA/Spitzer Infrared Telescope

    Tess is NASA’s newest exoplanet-hunting space telescope, the successor to the renowned Kepler Space Telescope that was used to find some 2,600 exoplanets.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    TESS, able to survey 85% of the night sky (400 times more than what Kepler could monitor), is about to finish its primary two-year mission but has fallen woefully short of expectations. NASA initially thought TESS was going to find more than 20,000 transiting exoplanets, but with only months left it has only identified 1,588 candidates. Even so, the telescope’s mission will almost surely be extended.

    See the full article here .


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    The mission of MIT Technology Review is to equip its audiences with the intelligence to understand a world shaped by technology.

     
  • richardmitnick 12:02 pm on December 31, 2019 Permalink | Reply
    Tags: , , , , , ESA’s Characterising Exoplanet Satellite Cheops, , Future giant ground based optical telescopes, NASA Kepler and K2,   

    From ars technica: “The 2010s: Decade of the exoplanet” 

    Ars Technica
    From ars technica

    12/31/2019
    John Timmer

    1
    Artist conception of Kepler-186f, the first Earth-size exoplanet found in a star’s “habitable zone.”

    ESO Belgian robotic Trappist National Telescope at Cerro La Silla, Chile

    A size comparison of the planets of the TRAPPIST-1 system, lined up in order of increasing distance from their host star. The planetary surfaces are portrayed with an artist’s impression of their potential surface features, including water, ice, and atmospheres. NASA

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    The last ten years will arguably be seen as the “decade of the exoplanet.” That might seem like an obvious thing to say, given that the discovery of the first exoplanet was honored with a Nobel Prize this year. But that discovery happened back in 1995—so what made the 2010s so pivotal?

    One key event: 2009’s launch of the Kepler planet-hunting probe.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    Kepler spawned a completely new scientific discipline, one that has moved from basic discovery—there are exoplanets!—to inferring exoplanetary composition, figuring out exoplanetary atmosphere, and pondering what exoplanets might tell us about prospects for life outside our Solar System.

    To get a sense of how this happened, we talked to someone who was in the field when the decade started: Andrew Szentgyorgyi, currently at the Harvard-Smithsonian Center for Astrophysics, where he’s the principal investigator on the Giant Magellan Telescope’s Large Earth Finder instrument.

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

    In addition to being famous for having taught your author his “intro to physics” course, Szentgyorgyi was working on a similar instrument when the first exoplanet was discovered.

    Two ways to find a planet

    The Nobel-winning discovery of 51 Pegasi b came via the “radial velocity” method, which relies on the fact that a planet exerts a gravitational influence on its host star, causing the star to accelerate slightly toward the planet.

    Radial Velocity Method-Las Cumbres Observatory

    Radial velocity Image via SuperWasp http http://www.superwasp.org-exoplanets.htm

    Unless the planet’s orbit is oriented so that it’s perpendicular to the line of sight between Earth and the star, some of that acceleration will draw the star either closer to or farther from Earth. This acceleration can be detected via a blue or red shift in the star’s light, respectively.

    The surfaces of stars can expand and contract, which also produces red and blue shifts, but these won’t have the regularity of acceleration produced by an orbital body. But it explains why, back in the 1990s, people studying the surface changes in stars were already building the necessary hardware to study radial velocity.

    “We had a group that was building instruments that I’ve worked with to study the pulsations of stars—astroseismology,” Szentgyorgyi told Ars, “but that turns out to be sort of the same instrumentation you would use” to discern exoplanets.

    He called the discovery of 51 Pegasi b a “seismic event” and said that he and his collaborators began thinking about how to use their instruments “probably when I got the copy of Nature” that the discovery was published in. Because some researchers already had the right equipment, a steady if small flow of exoplanet announcements followed.

    During this time, researchers developed an alternate way to find exoplanets, termed the “transit method.”

    Planet transit. NASA/Ames

    The transit method requires a more limited geometry from an exoplanet’s orbit: the plane has to cause the exoplanet to pass through the line of sight between its host star and Earth. During these transits, the planet will eclipse a small fraction of light from the host star, causing a dip in its brightness. This doesn’t require the specialized equipment needed for radial velocity detections, but it does require a telescope that can detect small brightness differences despite the flicker caused by the light passing through our atmosphere.

    By 2009, transit detections were adding regularly to the growing list of exoplanets.

    The tsunami

    In the first year it was launched, Kepler started finding new planets. Given time and a better understanding of how to use the instrument, the early years of the 2010s saw thousands of new planets cataloged. In 2009, Szentgyorgyi said, “it was still ‘you’re finding handfuls of exoplanetary systems.’ And then with the launch of Kepler, there’s this tsunami of results which has transformed the field.”

    Suddenly, rather than dozens of exoplanets, we knew about thousands.

    2
    The tsunami of Kepler planet discoveries.

    The sheer numbers involved had a profound effect on our understanding of planet formation. Rather than simply having a single example to test our models against—our own Solar System—we suddenly had many systems to examine (containing over 4,000 currently known exoplanets). These include objects that don’t exist in our Solar System, things like hot Jupiters, super-Earths, warm Neptunes, and more. “You found all these crazy things that, you know, don’t make any sense from the context of what we knew about the Solar System,” Szentgyorgyi told Ars.

    It’s one thing to have models of planet formation that say some of these planets can form; it’s quite another to know that hundreds of them actually exist. And, in the case of hot Jupiters, it suggests that many exosolar systems are dynamic, shuffling planets to places where they can’t form and, in some cases, can’t survive indefinitely.

    But Kepler gave us more than new exoplanets; it provided a different kind of data. Radial velocity measurements only tell you how much the star is moving, but that motion could be caused by a relatively small planet with an orbital plane aligned with the line of sight from Earth. Or it could be caused by a massive planet with an orbit that’s highly inclined from that line of sight. Physics dictates that, from our perspective, these will produce the same acceleration of the star. Kepler helped us sort out the differences.

    3
    A massive planet orbiting at a steep angle (left) and a small one orbiting at a shallow one will both produce the same motion of a star relative to Earth.

    “Kepler not only found thousands and thousands of exoplanets, but it found them where we know the geometry,” Szentgyorgyi told Ars. “If you know the geometry—if you know the planet transits—you know your orbital inclination is in the plane you’re looking.” This allows follow-on observations using radial velocity to provide a more definitive mass of the exoplanet. Kepler also gave us the radius of each exoplanet.

    “Once you know the mass and radius, you can infer the density,” Szentgyorgyi said. “There’s a remarkable amount of science you can do with that. It doesn’t seem like a lot, but it’s really huge.”

    Density can tell us if a planet is rocky or watery—or whether it’s likely to have a large atmosphere or a small one. Sometimes, it can be tough to tell two possibilities apart; density consistent with a watery world could also be provided by a rocky core and a large atmosphere. But some combinations are either physically implausible or not consistent with planetary formation models, so knowing the density gives us good insight into the planetary type.

    Beyond Kepler

    Despite NASA’s heroic efforts, which kept Kepler going even after its hardware started to fail, its tsunami of discoveries slowed considerably before the decade was over. By that point, however, it had more than done its job. We had a new catalog of thousands of confirmed exoplanets, along with a new picture of our galaxy.

    For instance, binary star systems are common in the Milky Way; we now know that their complicated gravitational environment isn’t a barrier to planet formation.

    We also know that the most common type of star is the low-mass red dwarf. It was previously possible to think that the star’s low mass would be matched by a low-mass planet-forming disk, preventing the generation of large planets and the generation of large families of smaller planets. Neither turned out to be true.

    “We’ve moved into a mode where we can actually say interesting, global, statistical things about exoplanets,” Szentgyorgyi told Ars. “Most exoplanets are small—they’re sort of Earth to sub-Neptune size. It would seem that probably most of the solar-type stars have exoplanets.” And, perhaps most important, there’s a lot of them. “The ubiquity of exoplanets certainly is a stunner… they’re just everywhere,” Szentgyorgyi added.

    That ubiquity has provided the field with two things. First, it has given scientists the confidence to build new equipment, knowing that there are going to be planets to study. The most prominent piece of gear is NASA’s Transiting Exoplanet Survey Satellite, a space-based telescope designed to perform an all-sky exoplanet survey using methods similar to Kepler’s.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    But other projects are smaller, focused on finding exoplanets closer to Earth. If exoplanets are everywhere, they’re also likely to be orbiting stars that are close enough so we can do detailed studies, including characterizing their atmospheres. One famous success in this area came courtesy of the TRAPPIST telescopes [above], which spotted a system hosting at least seven planets. More data should be coming soon, too; on December 17, the European Space Agency launched the first satellite dedicated to studying known exoplanets.

    ESA/CHEOPS

    With future telescopes and associated hardware similar to what Szentgyorgyi is working on, we should be able to characterize the atmospheres of planets out to about 30 light years from Earth. One catch: this method requires that the planet passes in front of its host star from Earth’s point of view.

    When an exoplanet transits in front of its star, most of the light that reaches Earth comes directly to us from the star. But a small percentage passes through the atmosphere of the exoplanet, allowing it to interact with the gases there. The molecules that make up the atmosphere can absorb light of specific wavelengths—essentially causing them to drop out of the light that makes its way to Earth. Thus, the spectrum of the light that we can see using a telescope can contain the signatures of various gases in the exoplanet’s atmosphere.

    There are some important caveats to this method, though. Since the fraction of light that passes through the exoplanet atmosphere is small compared to that which comes directly to us from the star, we have to image multiple transits for the signal to stand out. And the host star has to have a steady output at the wavelengths we’re examining in order to keep its own variability from swamping the exoplanetary signal. Finally, gases in the exoplanet’s atmosphere are constantly in motion, which can make their signals challenging to interpret. (Clouds can also complicate matters.) Still, the approach has been used successfully on a number of exoplanets now.

    In the air

    Understanding atmospheric composition can tell us critical things about an exoplanet. Much of the news about exoplanet discoveries has been driven by what’s called the “habitable zone.” That zone is defined as the orbital region around a star where the amount of light reaching a planet’s surface is sufficient to keep water liquid. Get too close to the star and there’s enough energy reaching the planet to vaporize the water; get too far away and the energy is insufficient to keep water liquid.

    These limits, however, assume an atmosphere that’s effectively transparent at all wavelengths. As we’ve seen in the Solar System, greenhouse gases can play an outsized role in altering the properties of planets like Venus, Earth, and Mars. At the right distance from a star, greenhouse gases can make the difference between a frozen rock and a Venus-like oven. The presence of clouds can also alter a planet’s temperature and can sometimes be identified by imaging the atmosphere. Finally, the reflectivity of a planet’s surface might also influence its temperature.

    The net result is that we don’t know whether any of the planets in a star’s “habitable zone” are actually habitable. But understanding the atmosphere can give us good probabilities, at least.

    The atmosphere can also open a window into the planet’s chemistry and history. On Venus, for example, the huge levels of carbon dioxide and the presence of sulfur dioxide clouds indicate that the planet has an oxidizing environment and that its atmosphere is dominated by volcanic activity. The composition of the gas giants in the outer Solar System likely reflects the gas that was present in the disk that formed the planets early in the Solar System’s history.

    But the most intriguing prospect is that we could find something like Earth, where biological processes produce both methane and the oxygen that ultimately converts it to carbon dioxide. The presence of both in an atmosphere indicates that some process(es) are constantly producing the gases, maintaining a long-term balance. While some geological phenomena can produce both these chemicals, finding them together in an atmosphere would at least be suggestive of possible life.

    Interdisciplinary

    Just the prospect of finding hints of life on other worlds has rapidly transformed the study of exoplanets, since it’s a problem that touches on nearly every area of science. Take the issue of atmospheres and habitability. Even if we understand the composition of a planet’s atmosphere, its temperature won’t just pop out of a simple equation. Distance from the star, type of star, the planet’s rotation, and the circulation of the atmosphere will all play a role in determining conditions. But the climate models that we use to simulate Earth’s atmosphere haven’t been capable of handling anything but the Sun and an Earth-like atmosphere. So extensive work has had to be done to modify them to work with the conditions found elsewhere.

    Similar problems appear everywhere. Geologists and geochemists have to infer likely compositions given little more than a planet’s density and perhaps its atmospheric compositions. Their results need to be combined with atmospheric models to figure out what the surface chemistry of a planet might be. Biologists and biochemists can then take that chemistry and figure out what reactions might be possible there. Meanwhile, the planetary scientists who study our own Solar System can provide insight into how those processes have worked out here.

    “I think it’s part of the Renaissance aspect of exoplanets,” Szentgyorgyi told Ars. “A lot of people now think a lot more broadly, there’s a lot more cross-disciplinary interaction. I find that I’m going to talks about geology, I’m going to talks about the atmospheric chemistry on Titan.”

    The next decade promises incredible progress. A new generation of enormous telescopes is expected to come online, and the James Webb space telescope should devote significant time to imaging exosolar systems.

    NASA/ESA/CSA Webb Telescope annotated


    ____________________________________________
    Other giant 30 meter class telescopes planned

    ESO/E-ELT,39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

    TMT-Thirty Meter Telescope, proposed and now approved for Mauna Kea, Hawaii, USA4,207 m (13,802 ft) above sea level, the only giant 30 meter class telescope for the Northern hemisphere


    ____________________________________________

    We’re likely to end up with much more detailed pictures of some intriguing bodies in our galactic neighborhood.

    The data that will flow from new experiments and new devices will be interpreted by scientists who have already transformed their field. That transformation—from proving that exoplanets exist to establishing a vibrant, multidisciplinary discipline—really took place during the 2010s, which is why it deserves the title “decade of exoplanets.”

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Ars Technica was founded in 1998 when Founder & Editor-in-Chief Ken Fisher announced his plans for starting a publication devoted to technology that would cater to what he called “alpha geeks”: technologists and IT professionals. Ken’s vision was to build a publication with a simple editorial mission: be “technically savvy, up-to-date, and more fun” than what was currently popular in the space. In the ensuing years, with formidable contributions by a unique editorial staff, Ars Technica became a trusted source for technology news, tech policy analysis, breakdowns of the latest scientific advancements, gadget reviews, software, hardware, and nearly everything else found in between layers of silicon.

    Ars Technica innovates by listening to its core readership. Readers have come to demand devotedness to accuracy and integrity, flanked by a willingness to leave each day’s meaningless, click-bait fodder by the wayside. The result is something unique: the unparalleled marriage of breadth and depth in technology journalism. By 2001, Ars Technica was regularly producing news reports, op-eds, and the like, but the company stood out from the competition by regularly providing long thought-pieces and in-depth explainers.

    And thanks to its readership, Ars Technica also accomplished a number of industry leading moves. In 2001, Ars launched a digital subscription service when such things were non-existent for digital media. Ars was also the first IT publication to begin covering the resurgence of Apple, and the first to draw analytical and cultural ties between the world of high technology and gaming. Ars was also first to begin selling its long form content in digitally distributable forms, such as PDFs and eventually eBooks (again, starting in 2001).

     
  • richardmitnick 11:49 am on September 20, 2019 Permalink | Reply
    Tags: "Unpacking the proposed exo-planet imaging telescope HabEx", , , , , Exoplanet hunting, NASA Kepler and K2,   

    From NASA Spaceflight: “Unpacking the proposed exo-planet imaging telescope HabEx” 

    NASA Spaceflight

    From NASA Spaceflight

    September 19, 2019
    Roland Winkler

    NASA Habitable Exoplanet Imaging Mission (HabEx) The Planet Hunter depiction

    1

    As part of NASA’s continued effort to ensure a steady supply of astrophysics and astronomy missions, the agency is undertaking the Astro2020: Decadal Survey on Astronomy and Astrophysics. Currently, in the “Concept Study” phase, the survey includes proposals for four large-scale space telescopes – including the Habitable Exoplanet Observatory (HabEx).

    HabEx would facilitate direct observation of exoplanets, carry a primary focus on imaging Earth-like planets around Sun-like stars, and be able to detect biomarkers or signs of possible life in those exoplanets’ atmospheres via spectroscopic observations.

    HabEx – taking exoplanet research to the next level:

    For millennia, the question of whether or not humanity is alone in the universe has captivated the minds of explorers and scientists.

    But until recently, an important part of that equation remained elusive: exactly how many exoplanets exist in our galaxy and the universe?

    The first confirmed detection of an exoplanet occurred in the early 1990s, with subsequent observations confirming the earliest detection actually occurred in the 1980s. But ground-based observations were slow and far between.

    To help solve the question once and for all, NASA launched the Kepler Space Telescope in 2009 – a telescope tasked solely with searching for exoplanets and determining how common they are.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    Kepler shattered all expectations of the number of exoplanets near Earth, revealing over the course of its multi-year mission that not only are exoplanets common throughout all regions within the visible space surrounding Earth but that almost every single star hosts at least one planet.

    What’s more, Kepler revealed an astonishing number of exoplanets that orbit within the so-called habitable zone of their parent stars – the zone in which liquid water can exist on the surface of a terrestrial planet.

    As of 1 September 2019, there are 4,109 confirmed exoplanets in 3,059 systems, with 667 systems having more than one planet.

    With that discovery, the desire to create better telescopes capable of directly imaging exoplanets and sampling their atmospheres catapulted to the top of the astrophysics mission wish lists.

    But so far only very large planets, many times larger than Jupiter and far away from their host stars have been imaged directly. Spectroscopic observations of exoplanet atmospheres are possible using telescopes and technology is possible but rare and very limited. The holy grail of directly imaging Earth-like planets around Sun-like stars is currently not possible.

    Thus, the holy grail of directly imaging Earth-like planets around Sun-like stars is currently not possible.

    3
    HabEx with its starshade performing operations NASA/JPLK-Caltech

    Enter HabEx. This proposed mission carries the stated goals of:

    Seeking out nearby worlds and exploring their habitability
    Mapping out nearby planetary systems and understanding the diversity of the worlds they contain, and
    Enabling new explorations of astrophysical systems from our solar system to galaxies and the universe by extending our reach in the ultraviolet, optical, and near-infrared spectrum.

    How will HabEx work?

    When directly observing exoplanets, the biggest problem to overcome is the glare of the host star, which is billions of times brighter than the exoplanet.

    Two of HabEx’s four instruments are designed to do exactly that.

    The first instrument is a star shade, which is actually a second spacecraft that would fly in formation at an average distance of 124,000 km in front of HabEx and block most of the host star’s light but not the light of planets in orbit of the host star.

    A dedicated instrument on HabEx would then pick up the light of these exoplanets and measure their spectrum.

    With enough observation time, HabEx’s instruments would be able to measure the concentration of water vapor, oxygen, ozone, and dust through Rayleigh scattering.


    SETI Institute “Next-Generation NASA Space Telescopes” 1:13:30

    The telescope would also be able to detect carbon dioxide and methane in an exoplanet’s atmosphere if they were present in higher concentrations than on Earth.

    The observation campaign would theoretically involve nine nearby solar systems at a distance of 10 to 20 light years.

    They would be observed three times each with an accumulated observation time of three months within the first five years of the telescope’s operation.

    Due to the nature of formation flying, pointing the star shade on a different target would be a slow, time-consuming process. Therefore, during times when the star shade would be repositioned on another star system, HabEx would use its other instruments, including a vector vortex coronagraph, to create family portraits of around 110 exosolar systems.

    The coronagraph, a telescopic attachment designed to block out the direct light from a star so that nearby objects – which otherwise would be hidden in the star’s bright glare – can be resolved, would block the light of the host star but not the light of the exoplanets in the system.

    Within the first 5 years, the coronagraph would be used for 3.5 years to create family images of 110 exosolar systems and detect dust, asteroid belts, and Kuiper Belt-like regions of exosolar systems. From these observed star systems, the ones with rocky planets in their respective habitable zones would be scheduled with star shade observations.

    4
    Exoplanet observation with HaBEx and its star shade. NASA/JPL-Caltech

    Together, the star shade and coronagraph would take about 75% of the first 5 years of observation time. The remaining 25% would be dedicated to the scientific community, which would submit observation proposals via a similar selection process as used today for the Hubble Space Telescope.

    In addition to the coronagraph and star shade, HabEx is proposed to contain two other important instruments: the HabEx Workhorse Camera (HWC) and the UV Spectrograph (UVS).

    The UVS intended for HabEx would provide 10 times larger area coverage compared to Hubble’s equivalent: the Cosmic Origins Spectrograph. With the Hubble Space Telescope close to the end of its life, the astronomic community will lose its only UV spectrograph with HST. UVS would fill that gap.

    Additionally, HabEx’s Workhorse Camera (HWC) would be an evolutionary step from Hubble’s Wide-Field Camera 3 and would provide imaging and multi-slit spectroscopy for two channels ranging from the near UV to the near IR.

    When executing exoplanet observations, both HWC and UVS could also be used in parallel with the star shade and coronagraph.

    What’s in a star shade?:

    The star shade for the HabEx Observatory would have a diameter of 72 m, consists of several thin sheets of material, and would be scaled relative to its operational distance from HabEx so that the telescope would be able to observe Earth-like planets around sun-like stars at a distance between 10 and 20 light years.

    4
    A breakdown of HabEX. NASA/JPL-Caltech

    It would have a 40 m diameter disk and 24 petals, each 16 m long and 5.25 m wide at its base for a structure tip-to-tip of 72 m. The total mass of the star shade is currently estimated at 2,520 kg with an additional 500 kg for the deployment mechanism.

    The material used to create the shade would be made of multiple layers of carbon-impregnated black Kapton. A gap between the individual layers would minimize the risk of a micrometeorite hit inducing a direct line of sight path between the target star and the telescope.

    The edges of each petal would also be chemically etched to produce a very sharp and smooth edge that minimizes light scattering.

    The star shade would be attached to its control hub, which is currently projected to weigh in at 6,394 kg.

    The hub would consist of propellant and control systems, including 12 hydrazine thrusters for station keeping with HabEx. These thrusters would use 1,407 kg of liquid bipropellant.

    Additionally, the hub would be equipped with six xenon Solar Electric Propulsion (SEP) thrusters for retargeting. This would require 5,600 kg of xenon gas.

    The amount of propellant planned would be enough for 100 individual pointings with an initial mission design of 18 pointings for the first 5 years.

    Using a coronagraph on HabEx:

    Coronagraphs are already in use for solar observations as well as in various ground-based telescopes and upcoming space missions such as the James Webb Space Telescope (JWST) and WFIRST.

    NASA/ESA/CSA Webb Telescope annotated

    NASA/WFIRST

    Like these telescopes, HabEx’s coronagraph could only work well if the light path through the telescope is extremely stable and matches its design exactly. Any deformation due to thermal gradients, vibration in the spacecraft, polarization, and other effects would diminish its functionality.

    The quality of optical surfaces must also be very high, which is why the coronagraph is the design driving element for many aspects of the HabEx telescope.

    To limit the vibration of HabEx, the telescope would not employ reaction wheels for pointing. Instead, microthrusters would be used, as demonstrated by NASA’s Gravity Probe B and ESA’s (European Space Agency’s) Gaia and LISA Pathfinder missions.

    The microthrusters would induce far less vibration to the system and would not be prone to failures as reaction wheels are.

    To limit the thermal stress on the primary mirror, the instruments are housed on the side of the telescope.

    6
    Images: Hubble left, HabEX right

    The diameter of HabEx main mirror is proposed at 4 m and designed to be made of 0-expansion glass ZERODUR, which would be heavier than other options but can be handled by the usual manufacturers without major hassle contrary to the Beryllium mirrors of JWST.

    Moreover, the coronagraph would drive the focal length of the optical design (i.e.: the length of the telescope) to a long telescope.

    How to launch HabEx:

    Should HabEx be approved as a mission, the immediate question would become how to launch it.

    In all, an integrated launch of HabEx and its star shade would place the launch mass at a little less than 35,000 kg with the launch needing to inject HabEx into the Earth-Sun L2 Lagrangian Point 1.5 million km from Earth.

    In short, there aren’t many options.

    NASA’s SLS Block 1B would be capable of launching the telescope. SpaceX’s Starship vehicle, while still in development with fluid performance numbers, is in a similar class as SLS 1B, and is thus another potential option

    However, neither of those rockets exist operationally at this point, and even when/if they do, there are questions as to what they will ultimately be capable of doing.

    8
    SLS’s Block 1B future is precarious at best with an unknown funding situation of the crucial Exploration Upper Stage – which has already been delayed multiple years and has forced NASA to switch several early SLS missions to the Block 1 configuration – as well as an “at any cost” lunar landing objective by 2024 for which the Block 1B is in no way required and would divert funds and attention away from.

    If SLS Block 1B does come to fruition and is used to launch HabEx, the telescope would benefit from the rocket’s capacity to throw more than 36,000 kg to the Earth-Sun L2 point.

    The Earth-Sun L2 point would be the primary operation location for HabEx given the area’s flat gravitational gradient and an undisturbed thermal environment.

    It would also allow for relatively easy servicing of HabEx as now mandated by the U.S. Congress in 2010 that all large spacecraft be serviceable.

    See the full article here .

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

    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA Spaceflight , now in its eighth year of operations, is already the leading online news resource for everyone interested in space flight specific news, supplying our readership with the latest news, around the clock, with editors covering all the leading space faring nations.

    Breaking more exclusive space flight related news stories than any other site in its field, NASASpaceFlight.com is dedicated to expanding the public’s awareness and respect for the space flight industry, which in turn is reflected in the many thousands of space industry visitors to the site, ranging from NASA to Lockheed Martin, Boeing, United Space Alliance and commercial space flight arena.

    With a monthly readership of 500,000 visitors and growing, the site’s expansion has already seen articles being referenced and linked by major news networks such as MSNBC, CBS, The New York Times, Popular Science, but to name a few.

     
  • richardmitnick 7:48 am on August 19, 2019 Permalink | Reply
    Tags: "How many Earth-like planets are around sun-like stars?", , , , , NASA Kepler and K2, ,   

    From Pennsylvania State University: “How many Earth-like planets are around sun-like stars?” 

    Penn State Bloc

    From Pennsylvania State University

    14 August 2019
    Sam Sholtis

    Media Contacts
    Eric B. Ford
    Professor of Astronomy and Astrophysics
    ebf11@psu.edu
    814- 863-5558

    Sam Sholtis
    Science Writer
    samsholtis@psu.edu
    (814) 865-1390

    1
    Artist’s impression of NASA’s Kepler space telescope, which discovered thousands of new planets. New research, using Kepler data, provides the most accurate estimate to date of how often we should expect to find Earth-like planets near sun-like stars. Credit: NASA/Ames Research Center/W. Stenzel/D. Rutter

    A new study provides the most accurate estimate of the frequency that planets that are similar to Earth in size and in distance from their host star occur around stars similar to our Sun. Knowing the rate that these potentially habitable planets occur will be important for designing future astronomical missions to characterize nearby rocky planets around sun-like stars that could support life. A paper describing the model appears August 14, 2019 in The Astronomical Journal.

    Thousands of planets have been discovered by NASA’s Kepler space telescope.

    NASA/Kepler Telescope, and K2 March 7, 2009 until November 15, 2018

    Kepler, which was launched in 2009 and retired by NASA in 2018 when it exhausted its fuel supply, observed hundreds of thousands of stars and identified planets outside of our solar system—exoplanets—by documenting transit events.*

    [On July 14, 2012, one of the spacecraft’s four reaction wheels used for pointing the spacecraft stopped turning, and completing the mission would only be possible if all other reaction wheels remained reliable. Then, on May 11, 2013, a second reaction wheel failed, disabling the collection of science data and threatening the continuation of the mission. This was the origin of the K2 misson.]

    Planet transit. NASA/Ames

    Transits events occur when a planet’s orbit passes between its star and the telescope, blocking some of the star’s light so that it appears to dim. By measuring the amount of dimming and the duration between transits and using information about the star’s properties astronomers characterize the size of the planet and the distance between the planet and its host star.

    “Kepler discovered planets with a wide variety of sizes, compositions and orbits,” said Eric B. Ford, professor of astronomy and astrophysics at Penn State and one of the leaders of the research team. “We want to use those discoveries to improve our understanding of planet formation and to plan future missions to search for planets that might be habitable. However, simply counting exoplanets of a given size or orbital distance is misleading, since it’s much harder to find small planets far from their star than to find large planets close to their star.”

    To overcome that hurdle, the researchers designed a new method to infer the occurrence rate of planets across a wide range of sizes and orbital distances. The new model simulates ‘universes’ of stars and planets and then ‘observes’ these simulated universes to determine how many of the planets would have been discovered by Kepler in each `universe.’

    “We used the final catalog of planets identified by Kepler and improved star properties from the European Space Agency’s Gaia spacecraft to build our simulations,” said Danley Hsu, a graduate student at Penn State and the first author of the paper.

    ESA/GAIA satellite

    “By comparing the results to the planets cataloged by Kepler, we characterized the rate of planets per star and how that depends on planet size and orbital distance. Our novel approach allowed the team to account for several effects that have not been included in previous studies.”

    The results of this study are particularly relevant for planning future space missions to characterize potentially Earth-like planets. While the Kepler mission discovered thousands of small planets, most are so far away that it is difficult for astronomers to learn details about their composition and atmospheres.

    “Scientists are particularly interested in searching for biomarkers—molecules indicative of life—in the atmospheres of roughly Earth-size planets that orbit in the ‘habitable-zone’ of Sun-like stars,” said Ford. “The habitable zone is a range of orbital distances at which the planets could support liquid water on their surfaces. Searching for evidence of life on Earth-size planets in the habitable zone of sun-like stars will require a large new space mission.”

    How large that mission needs to be will depend on the abundance of Earth-size planets. NASA and the National Academies of Science are currently exploring mission concepts that differ substantially in size and their capabilities. If Earth-size planets are rare, then the nearest Earth-like planets are farther away and a large, ambitious mission will be required to search for evidence of life on potentially Earth-like planets. On the other hand, if Earth-size planets are common, then there will be Earth-size exoplanets orbiting stars that are close to the sun and a relatively small observatory may be able to study their atmospheres.

    “While most of the stars that Kepler observed are typically thousands of light years away from the Sun, Kepler observed a large enough sample of stars that we can perform a rigorous statistical analysis to estimate of the rate of Earth-size planets in the habitable zone of nearby sun-like stars.” said Hsu.

    Based on their simulations, the researchers estimate that planets very close to Earth in size, from three-quarters to one-and-a-half times the size of earth, with orbital periods ranging from 237 to 500 days, occur around approximately one in six stars. Importantly, their model quantifies the uncertainty in that estimate. They recommend that future planet-finding missions plan for a true rate that ranges from as low about one planet for every 33 stars to as high as nearly one planet for every two stars.

    “Knowing how often we should expect to find planets of a given size and orbital period is extremely helpful for optimize surveys for exoplanets and the design of upcoming space missions to maximize their chance of success,” said Ford. “Penn State is a leader in bringing state-of-the-art statistical and computational methods to the analysis of astronomical observations to address these sorts of questions. Our Institute for CyberScience (ICS) and Center for Astrostatistics (CASt) provide infrastructure and support that makes these types of projects possible.”

    The Center for Exoplanets and Habitable Worlds at Penn State includes faculty and students who are involved in the full spectrum of extrasolar planet research. A Penn State team built the Habitable Zone Planet Finder, an instrument to search for low-mass planets around cool stars, which recently began science operations at the Hobby-Eberly Telescope, of which Penn State is a founding partner.

    U Texas Austin McDonald Observatory Hobby-Eberly Telescope, Altitude 2,026 m (6,647 ft)

    A second Penn State-built spectrograph is in being tested before it begins a complementary survey to discover and measure the masses of low-mass planets around sun-like stars. This study makes predictions for what such planet surveys will find and will help provide context for interpreting their results.

    In addition to Ford and Hsu, the research team includes Darin Ragozzine and Keir Ashby at Brigham Young University. The research was supported by NASA; the U.S. National Science Foundation (NSF); and the Eberly College of Science, the Department of Astronomy and Astrophysics, the Center for Exoplanets and Habitable Worlds, and the Center for Astrostatistics at Penn State. Advanced computing resources and services were provided by the Penn State Institute for CyberScience, including the NSF funded CyberLAMP cluster.

    • Kepler has been replaced by the TESS spacecraft.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    TESS is designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Penn State Campus

    WHAT WE DO BEST

    We teach students that the real measure of success is what you do to improve the lives of others, and they learn to be hard-working leaders with a global perspective. We conduct research to improve lives. We add millions to the economy through projects in our state and beyond. We help communities by sharing our faculty expertise and research.

    Penn State lives close by no matter where you are. Our campuses are located from one side of Pennsylvania to the other. Through Penn State World Campus, students can take courses and work toward degrees online from anywhere on the globe that has Internet service.

    We support students in many ways, including advising and counseling services for school and life; diversity and inclusion services; social media sites; safety services; and emergency assistance.

    Our network of more than a half-million alumni is accessible to students when they want advice and to learn about job networking and mentor opportunities as well as what to expect in the future. Through our alumni, Penn State lives all over the world.

    The best part of Penn State is our people. Our students, faculty, staff, alumni, and friends in communities near our campuses and across the globe are dedicated to education and fostering a diverse and inclusive environment.

     
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