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  • richardmitnick 10:59 am on December 26, 2018 Permalink | Reply
    Tags: Aliens? Or Alien Impostors? Finding Oxygen Might Not Mean Life After All, , , , , , Radial velocity method,   

    From Ethan Siegel: “Aliens? Or Alien Impostors? Finding Oxygen Might Not Mean Life, After All” 

    From Ethan Siegel
    Dec 25, 2018

    Both reflected sunlight on a planet and absorbed sunlight filtered through an atmosphere are two techniques humanity is presently developing to measure the atmospheric content and surface properties of distant worlds. In the future, this could include the search for organic signatures as well. (MELMAK / PIXABAY)

    The most surefire, easily-seen signature of life on Earth might be a cosmic red herring around other worlds.

    In our quest for life beyond the Solar System, it makes sense to look for a world like our own. We’ve long hoped to find an Earth-sized world around a Sun-like star at the right distance for liquid water as our first step, and with thousands of planets in our coffers already, we’re extremely close. But not every world with the right physical properties is going to have life; we need additional information to know whether a potentially habitable world is actually inhabited.

    The follow-up would be to analyze the planet’s atmosphere for Earth-like signatures: potential signs of life. Earth’s combination of atmospheric gases — nitrogen, oxygen, water vapor, carbon dioxide and more — has been assumed to be a dead giveaway for a planet with life on it. But a new study by planetary scientist Dr. Sarah Hörst’s team throws that into doubt [see paper below]. Even worlds rich in oxygen might not harbor aliens, but an impostor process that could fool us all.

    Most of the planets we know of that are comparable to Earth in size have been found around cooler, smaller stars than the Sun. This makes sense with the limits of our instruments; these systems have larger planet-to-star size ratios than our Earth does with respect to the Sun. (NASA / AMES / JPL-CALTECH)

    The scientific story of how to even reach that point is fascinating, and closer to becoming a reality than ever before. We can understand how this happens by imagining we were aliens, looking at our Sun from a large distance away, trying to determine if it possessed an inhabited world.

    By measuring the slight variations in the frequency of the Sun’s light over long periods of time, we’d be able to deduce the gravitational influence of the planets on them. This detection method is known either the radial velocity or the stellar wobble method, and can tell us information about a planet’s mass and orbital period. Most of the early (pre-Kepler) exoplanets were discovered with this technique, and it’s still the best method we have for both determining planetary masses and confirming the existence of candidate exoplanets.

    Radial Velocity Method-Las Cumbres Observatory

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

    Veloce Rosso, Australia’s next premier astronomical instrument. On the the Anglo-Australian Telescope (AAT). a precision radial velocity spectrograph, capable of detecting Earth-like planets

    AAO Anglo Australian Telescope near Siding Spring, New South Wales, Australia, Altitude 1,100 m (3,600 ft)

    Today, we know of over 3,500 confirmed exoplanets, with more than 2,500 of those found in the Kepler data. These planets range in size from larger than Jupiter to smaller than Earth. Yet because of the limitations on the size of Kepler and the duration of the mission, there have been zero Earth-sized planets found around Sun-like stars that fall into Earth-like orbits. (NASA/AMES RESEARCH CENTER/JESSIE DOTSON AND WENDY STENZEL; MISSING EARTH-LIKE WORLDS BY E. SIEGEL)

    We also need to know the size of the planet. With the stellar wobble alone, we’ll only know what the mass of the world is relative to the angle-of-inclination of its orbit. A world that’s the mass of Earth could be well-suited to life if it’s got an Earth-like atmosphere, but it could be disastrous for life if it’s an iron-like world with no atmosphere at all, or a low-density, puffy world with a large gaseous envelope.

    The transit method, where a planet passes in front of its parent star, is our most prolific method for measuring a planet’s radius.

    Planet transit. NASA/Ames

    By calculating how much of the parent star’s light it blocks when it crosses our line-of-sight, we can determine its size. For an alien civilization whose line-of-sight was properly aligned with Earth orbiting the Sun, we’d be able to detect it with technology only about 20% more sensitive than Kepler was.

    Kepler was designed to look for planetary transits, where a large planet orbiting a star could block a tiny fraction of its light, reducing its brightness by ‘up to’ 1%. The smaller a world is relative to its parent star, the more transits you need to build up a robust signal, and the longer its orbital period, the longer you need to observe to get a detection signal that rises above the noise. (MATT OF THE ZOONIVERSE/PLANET HUNTERS TEAM)

    This is roughly where we are today. We’ve found hundreds of worlds that we suspect are rocky orbiting their stars, many of them right around Earth-sized. For a large fraction of them, we’ve measured their mass, radius, and orbital period, with a small percentage being at the right orbital distance to have Earth-like temperatures.

    Most of them orbit red dwarf stars — the most common class of star in the Universe — which means the forces should tidally lock them: the same side should always face the star. These stars flare often, posing a danger to any potential atmospheres on these worlds.

    But a significant fraction will orbit K, G, or F-class stars, where they can rotate on their axes, maintain an atmosphere, and have the potential for Earth-like life. That’s where we want to look.

    When a planet transits in front of its parent star, some of the light is not only blocked, but if an atmosphere is present, filters through it, creating absorption or emission lines that a sophisticated-enough observatory could detect. If there are organic molecules or large amounts of molecular oxygen, we might be able to find that, too. (ESA / DAVID SING)

    And that’s where future technology is hoping to take us. If a larger Kepler-like telescope were equipped with the right instruments, we could break up the light passing through an exoplanet’s atmosphere during a transit, and determine its atomic and molecular contents. If we were looking at Earth, we could determine that it was composed of nitrogen, oxygen, argon, water vapor, and carbon dioxide, along with other trace signatures.

    Even without an ideal alignment, direct imaging will still be possible.

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley and SETI Institute

    Potential NASA flagship missions, such as HabEx or LUVOIR (with either a starshade or a coronagraph), could block the light of the parent star and detect the light from an orbiting planet directly. This light could again be broken up into its individual wavelengths, determining its molecular content.

    NASA Habitable Exoplanet Imaging Mission (HabEx) The Planet Hunter

    NASA Large UV Optical Infrared Surveyor (LUVOIR)

    Whether from absorption (transit) or emission (direct imaging), we could learn what a potential Earth-twin’s atmosphere is composed of.

    The Starshade concept could enable direct exoplanet imaging as early as the 2020s. This concept drawing illustrates a telescope using a star shade, enabling us to image the planets that orbit a star while blocking the star’s light to better than one part in 10 billion. (NASA AND NORTHROP GRUMMAN)

    So what if we find an oxygen-rich world? No other planets, dwarf planets, moons, or other objects contain even 1% oxygen that we know of. Earth’s atmosphere transformed over nearly 2 billion years before it had an oxygen content comparable to what it does today, and it was anaerobic life processes that created our modern atmosphere that’s rich in molecular oxygen. Because of how easily oxygen is destroyed by ultraviolet light and how difficult it is to produce in large quantities via inorganic, chemical processes, oxygen has long been taken as the one biosignature we could rely on to indicate a living world.

    If organic molecules were found there as well, it would seem like a surefire indicator that life, indeed, must have taken hold on such a planet.

    And that’s where the Hörst lab’s new findings come into play. In a paper just published in ACS Earth and Space Chemistry, a specially-designed chamber to mimic the environment of a hazy exoplanet atmosphere showed that molecular oxygen (O2) could be created in a number of environmental conditions likely to occur naturally, with no life necessary to create it.

    The ingenious method was to create a gas mixture that would be consistent with what we expect an Earth-like or super-Earth-like environment might hold. That mixture was then inserted into a specially-designed chamber and subjected to a variety of temperature, pressure, and energy-injection conditions that would likely mimic the activity that could occur on actual exoplanets.

    Chao He explaining how the study’s PHAZER setup works, where PHAZER is the specially-designed Planetary HAZE chamber found in the Hörst lab at Johns Hopkins University. (CHANAPA TANTIBANCHACHAI / JOHNS HOPKINS UNIVERSITY)

    A total of nine different gas mixtures were used at temperatures ranging from 27 °C (80 °F) up to approximately 370 °C (700 °F), representing the temperature range expected to naturally occur. The energy injection came in two different forms: from ultraviolet light and from plasma discharges, which represent natural conditions likely to be caused by sunlight or lightning-like activity.

    The results? There were multiple scenarios that resulted in the production of both organic molecules (like sugar and amino acid precursors) and oxygen, yet didn’t require any life at all to get them. According to first author Chao He,

    People used to suggest that oxygen and organics being present together indicates life, but we produced them abiotically in multiple simulations. This suggests that even the co-presence of commonly accepted biosignatures could be a false positive for life.

    By heating atmospheric gases thought to mimic exoplanet atmospheres to various temperatures and subjecting them to ultraviolet and plasma-based energy injections, organic molecules and oxygen can be produced. We must be careful that we don’t mistake an abiotic signature of coincidence oxygen and organics for life. (C. HE ET AL., ‘GAS PHASE CHEMISTRY OF COOL EXOPLANET ATMOSPHERES: INSIGHT FROM LABORATORY SIMULATIONS,’ ACS EARTH SPACE CHEM. (2018))

    The experiment wasn’t some cherry-picked design to attempt to produce this false-positive result, either. The gases inside the chamber were designed to mimic the contents of known exoplanetary atmospheres, with the ultraviolet energy injection designed to simulate sunlight. The experiments simulated a variety of atmospheric (hydrogen-rich, water-rich, and carbon dioxide-rich) environments, and all of them created haze particles and yielded organic molecules such as hydrogen cyanide, acetylene, and methanimine.

    Multiple environments generated organic molecules, prebiotic precursor molecules, and oxygen all at once, at Earth-like temperatures and much hotter temperatures as well. The paper itself states the main conclusion very succinctly:

    Our laboratory results indicate that complex atmospheric photochemistry can happen in diverse exoplanet atmospheres and lead to the formation of new gas products and haze particles, including compounds (O2 and organics) that could be falsely identified as biosignatures.

    The amount of molecular oxygen produced in these experiments was relatively small by some metrics; Hörst herself wouldn’t call the atmospheres created in the lab “oxygen-rich.” But it’s nevertheless possible that these processes would translate into an oxygen-rich atmosphere on an exoplanet, given the right conditions and enough time. At this point, it appears possible that finding the presence of both organics and molecular oxygen could be due to abiotic, non-life processes exclusively.

    Signatures of organic, life-giving molecules are found all over the cosmos, including in the largest, nearby star-forming region: the Orion Nebula. Someday soon, we may be able to look for biosignatures in the atmospheres of Earth-sized worlds around other stars, or we may detect simple life directly on another world in our Solar System. (ESA, HEXOS AND THE HIFI CONSORTIUM; E. BERGIN)

    This doesn’t mean that finding an Earth-like world with an oxygen-rich atmosphere won’t be incredibly interesting; it absolutely will be. It doesn’t mean that finding organic molecules coincident with the oxygen won’t be compelling; it will be a finding worth getting excited over. It doesn’t even mean that it won’t be indicative of life; a world with oxygen and organic molecules may well be overflowing with living organisms. But it does mean that we have to be careful.

    Historically, when we’ve looked to the skies for evidence of life beyond Earth, we’ve been biased by hope and what we know on Earth. Theories of dinosaurs on Venus or canals on Mars still linger in our memories, and we must be careful that extraterrestial oxygen signatures don’t lead us to falsely optimistic conclusions. We now know that both abiotic processes and life-dependent ones can create an oxygen-rich atmosphere.

    The hard problem, then, will be disentangling the potential causes when we actually find our first oxygen-rich, Earth-like exoplanet. Our reward, if we’re successful, will be the knowledge of whether or not we’ve actually found life around another star.

    See the full article here .


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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 9:33 am on September 22, 2018 Permalink | Reply
    Tags: , , , , , , NASA/MIT TESS finds 1st two exoplanet candidates during first science orbit, Radial velocity method, TESS in excellent health,   

    From NASA Spaceflight: “TESS in excellent health, finds 1st two exoplanet candidates during first science orbit” 

    NASA Spaceflight

    From NASA Spaceflight

    September 20, 2018
    Chris Gebhardt

    The joint NASA / Massachusetts Institute of Technology (MIT) Transiting Exoplanet Survey Satellite, or TESS, has completed its first science orbit after launch and orbital activations/checkouts. Unsurprisingly given TESS’s wide range of view, a team of scientists have already identified the planet-hunting telescope’s first two exoplanet candidates.
    No image credit.

    The yet-to-be-confirmed exoplanets are located 59.5 light years from Earth in the Pi Mensae system and 49 light years away in the LHS 3844 system.

    TESS’s overall health:

    Following a successful launch on 18 April 2018 aboard a SpaceX Falcon 9 rocket from SLC-40 at the Cape Canaveral Air Force Station, Florida, TESS was injected into an orbit aligned for a gravity assist maneuver one month later with the Moon to send the telescope into its operational 13.65-day orbit of Earth.

    TESS’s orbit is highly unique, with the trajectory designed so the telescope is in a 2:1 resonance with the Moon at a 90° phase offset at apogee (meaning the telescope maintains a separation from the Moon so the lunar gravity field doesn’t perturb TESS’ orbit but at the same time keeps the orbit stable) to allow the spacecraft to use as little of its maneuvering fuel as possible to achieve a hoped-for 20 year life.

    At the time of launch, mission scientists and operators noted that first light images were expected from TESS in June 2018 following a 60-day commissioning phase.

    While it is not entirely clear what happened after launch, what is known is that the commissioning phase lasted 27 days longer than expected, stretching to the end of July. TESS’ first science and observational campaign began not in June but on 25 July 2018.

    By 7 August, the halfway point in the first science observation period, TESS took what NASA considers to be the ceremonial “first light” images of the telescope’s scientific ventures.

    TESS acquired the image using all four cameras during a 30-minute period on Tuesday, 7 August. The images include parts of a dozen constellations from Capricornus to Pictor, both the Large and Small Magellanic Clouds, and the galaxies nearest to our own.

    Ceremonial first light image captured by TESS on 7 August 2018 showing the full Sector 1 image (center) and close-ups of each of the four camera groups (left and right) Credit NASA/MIT/TESS

    “In a sea of stars brimming with new worlds, TESS is casting a wide net and will haul in a bounty of promising planets for further study,” said Paul Hertz, astrophysics division director at NASA Headquarters. “This first light science image shows the capabilities of TESS’ cameras and shows that the mission will realize its incredible potential in our search for another Earth.”

    George Ricker, TESS’ principal investigator at the Massachusetts Institute of Technology’s Kavli Institute for Astrophysics and Space Research, added, “This swath of the sky’s southern hemisphere includes more than a dozen stars we know have transiting planets based on previous studies from ground observatories.”

    While TESS orbits Earth every 13.65 days, its data collection phase for each of its 26-planned observation sectors of near-Earth sky lasts for two orbits so the telescope can collect light data from each section for a total of 27.4 days.

    With science operations formerly commencing on 25 July, the first observational campaign stretched to 22 August.

    Unlike some missions which only transmit data back to Earth after observational campaigns end, TESS transmits its data both in the middle and at the end of each campaign when the telescope swings past its perigee (closest orbital approach to Earth).

    On 22 August, after TESS completed its first observation campaign of a section of the Southern Hemisphere sky, the telescope transmitted the second batch of light data to Earth through the Deep Space Network.

    From there, the information was processed and analyzed at NASA’s Science Processing and Operations Center at the Ames Research Center in California – which provided calibrated images and refined light curves for scientists to analyze and find promising exoplanet transit candidates.

    NASA and MIT then made that data available to scientists as they search for the more than 22,000 exoplanets (most of those within a 300 light-year radius of Earth) that TESS is expected to find during the course of its two-year primary mission.

    First TESS exoplanet candidate:

    Given the sheer number of exoplanets TESS is expected to find in the near-Earth neighborhood, it is not surprising that the first observation campaign has already returned potential exoplanet candidates – the first of which was confirmed by NASA via a tweet on Wednesday, 19 September.

    TESS’ first exoplanet candidate is Pi Mensae c – a super-Earth with an orbital period of 6.27 days. According to a draft of the paper announcing the discovery, several methods were used to eliminate the possibility of this being a false detection or the detection of a previously unknown companion star.

    The Pi Mensae system is located 59.5 light years from Earth, and the new exoplanet – if confirmed – would be officially classified Pi Mensae c, the second known exoplanet of the system.

    Exoplanet’s official classifications derive from the name of the star they orbit followed by a lowercase letter indicating the order in which they were discovered in a particular system.

    The order in which exoplanets are discovered does not necessarily match the order (distance from closest to farthest) in which they orbit their parent star.

    Moreover, the lowercase letter designation begins with the letter “b”, not the letter “a”. Thus, the first discovered exoplanet in a particular system will bear the name of its parent star followed by a lowercase “b”.

    Subsequent exoplanets orbiting the same start or stars (as the case may be), regardless of whether they orbit closer to or farther away from the parent star than the first discovered exoplanet will then bear the letters c, d, e, etc.

    NASA/Ames – Wendy Stenzel

    Therefore, confirmation of the new exoplanet candidate in the Pi Mensae system would make the planet Pi Mensae c.

    Pi Mensae b, a superjovian, was discovered on 15 October 2001 using the radial-velocity method of detection via the Anglo-Australian Telescope operated by the Australian Astronomical Observatory at Siding Spring Observatory.

    In the search for exoplanets, two general methods of detection are used – direct observation of a transiting exoplanet that passes between its star and the observation point on or near Earth (the method employed by TESS) and the radial-velocity, or doppler spectroscopy, method of detection which measures the wobble or gravitational tug on a parent star caused by an orbiting planet that does not pass between the star and the observation point on or near Earth.

    Overall, roughly 30% of the total number of known exoplanets have been discovered via the radial-velocity method, with the other 70% being discovered via the transiting method of detection.

    Radial Velocity Method-Las Cumbres Observatory

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

    Planet transit. NASA/Ames

    Upon Pi Mensae b’s discovery in 2001, the planet was found to be in a highly eccentric 5.89 Earth-year (2,151 day) orbit – coming as close at 1.21 AU and passing as far as 5.54 AU from its star.

    Artist’s depiction of a Super-Juiter orbiting its host star

    With a 1.21 AU periastron, Pi Mensae b passes through its parent star’s habitable zone before arcing out to apastron (which lies farther out than Jupiter’s orbit of our Sun).

    Given the extreme eccentricity and the fact that the planet passes through the habitable zone during each orbit, it would likely have disrupted the orbit of any potentially Earth-like planet in that zone due to its extreme mass of more than 10 times that of Jupiter.

    As for Pi Mensae itself, the star is a 3.4 billion year old (roughly 730 million years younger than the Sun) yellow dwarf that is 1.11 times the mass of the Sun, 1.15 times the Sun’s radius, and 1.5 times the Sun’s luminosity.

    Due to its proximity to Earth and its high luminosity, the star has an apparent magnitude of 5.67 and is visible to the naked eye in dark, clear skies.

    The star’s brightness – unsurprisingly – gives a potential instant “win” for the TESS team, whose stated pre-mission goal was to find near-Earth transiting exoplanets around exceptionally bright stars.

    Pi Mensae is currently the second brightest star to host a confirmed transiting exoplanet, Pi Mensae b.

    As an even greater testament to TESS’ power, just hours before publication of this article, the TESS team confirmed a second exoplanet candidate from the first observation campaign.

    The second exoplanet candidate is LHS 3844 b. It orbits its parent star – an M dwarf – every 11 hours and is located 49 light years from Earth.

    The exoplanet candidate is described by NASA and the TESS team as a “hot Earth.”

    Given the wealth of light data for scientists to pour through from the now-completed first two of 26 observation sectors, it is highly likely that hundreds if not thousands of exoplanets candidates will be identified in the coming months and years — with tens of thousands of candidate planets to follow in the remaining 24 sectors of sky to be searched.

    See the full article here .


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  • richardmitnick 8:26 am on August 30, 2018 Permalink | Reply
    Tags: , , , , Dyson spheres, Dyson spheres are hypothetical megastructures built by extraterrestrials for the purpose of harvesting all of a star’s energy, , , Radial velocity method, The star TYC 6111-1162-1   

    From ESA GAIA Mission via EarthSky: “How Gaia could help find Dyson spheres” 

    ESA/GAIA satellite

    From ESA GAIA Mission



    August 30, 2018
    Paul Scott Anderson

    Dyson spheres are hypothetical megastructures built by extraterrestrials for the purpose of harvesting all of a star’s energy. Here’s how the European Space Agency’s Gaia mission might help find one.

    Artists’ concept of a Dyson sphere. Notice the little moon or planet on the left side, being ravaged for raw materials. This image – called Shield World Construction – is by Adam Burn. Via http://www.FantasyWallpapers.com.

    When contemplating extraterrestrial intelligence, one of the most tantalizing ideas is that a super-advanced alien civilization could build an enormous structure around its home star, to collect a significant portion of the star’s energy. This hypothetical megastructure is popularly known as a Dyson sphere. It’s a sci-fi-sounding concept, but some scientists have also seriously considered it. This week, a story emerged about how the European Space Agency’s Gaia mission – whose primary purpose is to create a 3D map of our Milky Way galaxy – might be instrumental in the search for Dyson spheres.

    In the past, searches for Dyson spheres have focused on looking for signs of excess infrared or heat radiation in the vicinity of a star. That would be a telltale signature, but those attempts have come up empty, so far. The new peer-reviewed study – which was published in The Astrophysical Journal on July 18, 2018, and later described in Astrobites – proposes looking for Dyson spheres with little or no infrared excess. In other words, it describes a technique not attempted before.

    Erik Zackrisson at Uppsala University in Sweden led the new study. It focuses on a type of Dyson sphere that would’ve been missed by prior searches focused on infrared radiation.

    Suppose you were looking toward a Dyson sphere. What would you see? The visible light of the star would be reduced significantly since the Dyson sphere itself – by its nature – would mostly surround the star for purposes of energy collection. The star would continue shining; it would be shining on the inner portion of the Dyson sphere. Presumably, the star’s radiation would heat the sphere. According to earlier thoughts by scientists on the subject, a Dyson sphere should have a temperature between 50 and 1,000 Kelvin (-370 to 1300 degrees Fahrenheit; -220 to 730 degrees Celsius). At that temperature, radiation from the sphere would peak in infrared wavelengths.

    That was the earlier idea, until Zackrisson’s study.

    An all-sky view of the Milky Way and neighboring galaxies from the Gaia mission. This view includes measurements of nearly 1.7 billion stars. Image via Gaia Data Processing and Analysis Consortium (DPAC)/A. Moitinho/A. F. Silva/M. Barros/C. Barata – University of Lisbon, Portugal/H. Savietto – Fork Research, Portugal.

    His study suggests the possibility that the sphere might be composed of a different kind of material than what had been previously supposed. Suppose this material had the ability to dim the star’s light equally at all wavelengths? That would make it a so-called gray absorber and would significantly affect methods used to search for Dyson spheres. If you measured the star’s distance spectrophotometrically – by comparing the star’s observed flux and spectrum to standard stellar emission models – then the measurements would suggest that the star is farther away than it actually is.

    But then if you measured the star’s distance using the parallax method, you’d get a different number.

    Parallax method ESA

    The parallax method compares the apparent movement of a nearby star against the stellar background, as Earth moves from one side of its orbit to another across a period of, say, six months.

    The size of a Dyson sphere could be determined by comparing the difference in distances between these two methods. The greater the difference, the greater the amount of the star’s surface that is being obscured by the sphere.

    Now, thanks to new data from the Gaia mission, astronomers can do these kinds of comparisons, which could – in theory – detect a Dyson sphere. From the new study:

    “A star enshrouded in a Dyson sphere with a high covering fraction may manifest itself as an optically subluminous object with a spectrophotometric distance estimate significantly in excess of its parallax distance. Using this criterion, the Gaia mission will in coming years allow for Dyson sphere searches that are complementary to searches based on waste-heat signatures at infrared wavelengths. A limited search of this type is also possible at the current time, by combining Gaia parallax distances with spectrophotometric distances from ground-based surveys. Here, we discuss the merits and shortcomings of this technique and carry out a limited search for Dyson sphere candidates in the sample of stars common to Gaia Data Release 1 and Radial Velocity Experiment (RAVE) Data Release 5. We find that a small fraction of stars indeed display distance discrepancies of the type expected for nearly complete Dyson spheres.”

    In other words, using this new method, astronomers have found candidate Dyson sphere stars.

    Graph showing distribution of covering fractions for all stars in the Gaia-RAVE database overlap (left) and just those stars with less than 10 percent error in their Gaia parallax distance and less than 20 percent error in their RAVE spectrophotometric distance (right). If the parallax distance is smaller than the spectrophotometric distance, that is interpreted this as a negative covering fraction, and could be an indication of a Dyson sphere surrounding that star. Image via Zackrisson et al. 2018.

    The Gaia mission is currently charting a three-dimensional map of our galaxy, providing unprecedented positional and radial velocity measurements with the highest accuracy ever. The goal is to produce a stereoscopic and kinematic census of about one billion stars in the Milky Way galaxy and throughout the Local Group of galaxies.

    As it happens, these data are very useful when searching for Dyson spheres.

    Using the parallax distances from the first data release of Gaia, Zackrisson and his colleagues compared that data to previously measured spectrophotometric distances from the Radial Velocity Experiment (RAVE), which takes spectra of stars in the Milky Way. This resulted in an estimate of what percentage of each star could be blocked by Dyson sphere material.

    Radial Velociity Method. ESO

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

    Radial Velocity Method-Las Cumbres Observatory

    Illustration of how Gaia is measuring the distances to most stars in the Milky Way with unprecedented accuracy. Image via S. Brunier/ESO; Graphic source: ESA.

    Of course, figuring out if any of these could actually be Dyson sphere candidates required further analysis. Zackrisson and his team decided to focus on main-sequence stars (like the sun), spectral types F, G and K, and narrowed those down to those which displayed a potential blocking fraction greater than 0.7. Larger giant stars were removed from the data set since their spectrophotometric distances tend to be overestimated compared to main-sequence stars.

    This alone left only six possible candidates. Those in turn were then narrowed down to only two, after eliminating four candidates due to problems with the data itself. One of those, the star TYC 6111-1162-1, was then considered to be the best remaining candidate.

    So … has the first Dyson Sphere been found? The simple answer is we don’t know yet. The star, a garden-variety late-F dwarf, seems to exhibit the sought-after characteristics, but more data is needed. No other glitch-related weirdness was found in the data, but the star was also found to be a binary system consisting of two stars (the other being a small white dwarf) which might explain the results – but none of that is certain yet. Additional study of the star will be required, including using future Gaia data releases, to determine what is really happening here. From the new study:

    “To shed light on the properties of objects in this outlier population, we present follow-up high-resolution spectroscopy for one of these stars, the late F-type dwarf TYC 6111-1162-1. The spectrophotometric distance of this object is about twice that derived from its Gaia parallax, and there is no detectable infrared excess. While our analysis largely confirms the stellar parameters and the spectrophotometric distance inferred by RAVE, a plausible explanation for the discrepant distance estimates of this object is that the astrometric solution has been compromised by an unseen binary companion, possibly a rather massive white dwarf. This scenario can be further tested through upcoming Gaia data releases.”


    See the full article here .


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    A global space astrometry mission, Gaia will make the largest, most precise three-dimensional map of our Galaxy by surveying more than a thousand million stars.

    Gaia will monitor each of its target stars about 70 times over a five-year period. It will precisely chart their positions, distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and observe hundreds of thousands of asteroids within our own Solar System. The mission will also study about 500 000 distant quasars and will provide stringent new tests of Albert Einstein’s General Theory of Relativity.

    Gaia will create an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy and beyond, mapping their motions, luminosity, temperature and composition. This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy.

    For example, Gaia will identify which stars are relics from smaller galaxies long ago ‘swallowed’ by the Milky Way. By watching for the large-scale motion of stars in our Galaxy, it will also probe the distribution of dark matter, the invisible substance thought to hold our Galaxy together.

    Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye).

    For all objects brighter than magnitude 15 (4000 times fainter than the naked eye limit), Gaia will measure their positions to an accuracy of 24 microarcseconds. This is comparable to measuring the diameter of a human hair at a distance of 1000 km.

    It will allow the nearest stars to have their distances measured to the extraordinary accuracy of 0.001%. Even stars near the Galactic centre, some 30 000 light-years away, will have their distances measured to within an accuracy of 20%.

    The vast catalogue of celestial objects expected from Gaia’s scientific haul will not only benefit studies of our own Solar System and Galaxy, but also the fundamental physics that underpins our entire Universe.

  • richardmitnick 11:06 am on August 20, 2018 Permalink | Reply
    Tags: , , , , , Radial velocity method   

    From European Space Agency: “Infant exoplanet weighed by Hipparcos and Gaia” 

    ESA Space For Europe Banner

    From European Space Agency

    20 August 2018

    The mass of a very young exoplanet has been revealed for the first time using data from ESA’s star mapping spacecraft Gaia and its predecessor, the quarter-century retired Hipparcos satellite.

    Astronomers Ignas Snellen and Anthony Brown from Leiden University, the Netherlands, deduced the mass of the planet Beta Pictoris b from the motion of its host star over a long period of time as captured by both Gaia and Hipparcos. ([Nature Astronomy])

    Beta Pictoris system

    ESA/GAIA satellite

    ESA/Hipparcos satellite

    The planet is a gas giant similar to Jupiter but, according to the new estimate, is 9 to 13 times more massive. It orbits the star Beta Pictoris, the second brightest star in the constellation Pictor.

    The planet was only discovered in 2008 in images captured by the Very Large Telescope at the European Southern Observatory in Chile.

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

    Both the planet and the star are only about 20 million years old – roughly 225 times younger than the Solar System. Its young age makes the system intriguing but also difficult to study using conventional methods.

    “In the Beta Pictoris system, the planet has essentially just formed,” says Ignas. “Therefore we can get a picture of how planets form and how they behave in the early stages of their evolution. On the other hand, the star is very hot, rotates fast, and it pulsates.”

    This behaviour makes it difficult for astronomers to accurately measure the star’s radial velocity – the speed at which it appears to periodically move towards and away from the Earth. Tiny changes in the radial velocity of a star, caused by the gravitational pull of planets in its vicinity, are commonly used to estimate masses of exoplanets. But this method mainly works for systems that have already gone through the fiery early stages of their evolution.

    In the case of Beta Pictoris b, upper limits of the planet’s mass range had been arrived at before using the radial velocity method. To obtain a better estimate, the astronomers used a different method, taking advantage of Hipparcos’ and Gaia’s measurements that reveal the precise position and motion of the planet’s host star in the sky over time.

    Astrometric measurements to detect exoplanets

    “The star moves for different reasons,” says Ignas. “First, the star circles around the centre of the Milky Way, just as the Sun does. That appears from the Earth as a linear motion projected on the sky. We call it proper motion. And then there is the parallax effect, which is caused by the Earth orbiting around the Sun. Because of this, over the year, we see the star from slightly different angles.”

    And then there is something that the astronomers describe as ‘tiny wobbles’ in the trajectory of the star across the sky – minuscule deviations from the expected course caused by the gravitational pull of the planet in the star’s orbit.

    Planet transit. NASA/Ames

    This is the same wobble that can be measured via changes in the radial velocity, but along a different direction – on the plane of the sky, rather than along the line of sight.

    Radial Velocity Method-Las Cumbres Observatory

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

    “We are looking at the deviation from what you expect if there was no planet and then we measure the mass of the planet from the significance of this deviation,” says Anthony. “The more massive the planet, the more significant the deviation.”

    To be able to make such an assessment, astronomers need to observe the trajectory of the star for a long period of time to properly understand the proper motion and the parallax effect.

    The Gaia mission, designed to observe more than one billion stars in our Galaxy, will eventually be able to provide information about a large amount of exoplanets.

    In the 22 months of observations included in Gaia’s second data release, published in April, the satellite has recorded the star Beta Pictoris about thirty times. That, however, is not enough.

    “Gaia will find thousands of exoplanets, that’s still on our to-do list,” says Timo Prusti, ESA’s Gaia project scientist. “The reason that the exoplanets can be expected only late in the mission is the fact that to measure the tiny wobble that the exoplanets are causing, we need to trace the position of stars for several years.”

    Combining the Gaia measurements with those from ESA’s Hipparcos mission, which observed Beta Pictoris 111 times between 1990 and 1993, enabled Ignas and Anthony to get their result much faster.

    This led to the first successful estimate of a young planet’s mass using astrometric measurements.

    “By combining data from Hipparcos and Gaia, which have a time difference of about 25 years, you get a very long term proper motion,” says Anthony.

    “This proper motion also contains the component caused by the orbiting planet. Hipparcos on its own would not have been able to find this planet because it would look like a perfectly normal single star unless we had measured it for a much longer time.

    “Now, by combining Gaia and Hipparcos and looking at the difference in the long term and the short term proper motion, we can see the effect of the planet on the star.”

    The result represents an important step towards better understanding the processes involved in planet formation, and anticipates the exciting exoplanet discoveries that will be unleashed by Gaia’s future data releases.

    See the full article here .

    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 1:50 pm on May 13, 2018 Permalink | Reply
    Tags: , , , , , , , Radial velocity method, ,   

    From ASU via Science News: “The recipes for solar system formation are getting a rewrite” 

    ASU Bloc

    From Arizona State University

    Science News

    May 11, 2018
    Lisa Grossman

    Exoplanets: Left to right Kepler-22b, Kepler-69c, Kepler-62e, Kepler-62f, with Earth-except for Earth these are artists’ concepts. Image credit: NASA Ames/ JPL-Caltech

    With a mortar and pestle, Christy Till blends together the makings of a distant planet. In her geology lab at Arizona State University in Tempe, Till carefully measures out powdered minerals, tips them into a metal capsule and bakes them in a high-pressure furnace that can reach close to 35,000 times Earth’s atmospheric pressure and 2,000° Celsius.

    In this interplanetary test kitchen, Till and colleagues are figuring out what might go into a planet outside of our solar system.

    “We’re mixing together high-purity powders of silica and iron and magnesium in the right proportions to make the composition we want to study,” Till says. She’s starting with the makings of what might resemble a rocky planet that’s much different from Earth. “We literally make a recipe.”

    Scientists have a few good ideas for how to concoct our own solar system. One method: Mix up a cloud of hydrogen and helium, season generously with oxygen and carbon, and sprinkle lightly with magnesium, iron and silicon. Condense and spin until the cloud forms a star surrounded by a disk. Let rest about 10 million years, until a few large lumps appear. After about 600 million years, shake gently.

    GET COOKING Geologist Christy Till mixes up a mock exoplanet from powdered minerals in her Arizona lab. Abigail Weibel Photography

    But that’s only one recipe in the solar systems cookbook. Many of the planets orbiting other stars are wildly different from anything seen close to home. As the number of known exoplanets has climbed — 3,717 confirmed as of April 12 — scientists are creating new recipes.

    Seven of those exoplanets are in the TRAPPIST-1 system, one of the most exciting families of planets astronomers have discovered to date.

    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

    The TRAPPIST-1 star, an ultracool dwarf, is orbited by seven Earth-size planets (NASA).

    At least three TRAPPIST-1 planets might host liquid water on their surface, making them top spots to look for signs of life (SN: 12/23/17, p. 25).

    Yet those planets shouldn’t exist. Astronomers calculated that the small star’s preplanet disk shouldn’t have contained enough rocky material to make even one Earth-sized orb, says astrophysicist Elisa Quintana of NASA’s Goddard Space Flight Center in Greenbelt, Md. Yet the disk whipped up seven.

    TRAPPIST-1 is just one of the latest in a long line of rule breakers.
    Other systems host odd characters not seen in our solar system: super-Earths, mini-Neptunes, hot Jupiters and more. Many exoplanets must have had chaotic beginnings to exist where we find them.

    These oddballs raise exciting questions about how solar systems form. Scientists want to know how much of a planet’s ultimate fate depends on its parent star, which ingredients are essential for planet building and which are just frosting on the planetary cake.

    NASA’s Transiting Exoplanet Survey Satellite, or TESS, which launched April 18, should bring in some answers.


    TESS is expected to find thousands more exoplanets in the next two years. That crowd will help illuminate which planetary processes are the most common — and will help scientists zero in on the best planets to check for signs of life.

    CAKE POP PLANETS Yes, baking actually makes a nice analogy for planet formation. Take a look.

    Beyond the bare necessities

    All solar system recipes share some basic elements. The star and its planets form from the same cloud of gas and dust. The densest region of the cloud collapses to form the star, and the remaining material spreads itself into a rotating disk, parts of which will eventually coalesce into planets. That similarity between the star and its progeny tells Till and other scientists what to toss into the planetary stand mixer.

    “If you know the composition of the star, you can know the composition of the planets,” says astronomer Johanna Teske of the Carnegie Observatories in Pasadena, Calif. A star’s composition is revealed in the wavelengths of light the star emits and absorbs.

    When a planet is born can affect its final makeup, too. A gas giant like Jupiter first needs a rocky core about 10 times Earth’s mass before it can begin gobbling up gas. That much growth probably happens well before the disk’s gas disappears, around 10 million years after the star forms. Small, rocky planets like Earth probably form later.

    Finally, location matters. Close to the hot star, most elements are gas, which is no help for building planets from scratch. Where the disk cools toward its outer edge, more elements freeze to solid crystals or condense onto dust grains. The boundary where water freezes is called the snow line. Scientists thought that water-rich planets must either form beyond their star’s snow line, where water is abundant, or must have water delivered to them later (SN: 5/16/15, p. 8). Giant planets are also thought to form beyond the snow line, where there’s more material available.

    But the material in the disk might not stay where it began, Teske says. “There’s a lot of transport of material, both toward and away from the star,” she says. “Where that material ends up is going to impact whether it goes into planets and what types of planets form.” The amount of mixing and turbulence in the disk could contribute to which page of the cookbook astronomers turn to: Is this system making a rocky terrestrial planet, a relatively small but gaseous Neptune or a massive Jupiter?


    In the disk around a star, giant planets form beyond the “snow line,” where water freezes and more solids are available. Turbulence closer in knocks things around.

    Source: T. Henning and D. Semenov/Chemical Reviews 2013

    Some like it hot

    Like that roiling disk material, a full-grown planet can also travel far from where it formed.

    Consider “Hoptunes” (or hot Neptunes), a new class of planets first named in December in Proceedings of the National Academy of Sciences. Hoptunes are between two and six times Earth’s size (as measured by the planet’s radius) and sidled up close to their stars, orbiting in less than 10 days. That close in, there shouldn’t have been enough rocky material in the disk to form such big planets. The star’s heat should mean no solids, just gases.

    Hoptunes share certain characteristics — and unanswered questions — with hot Jupiters, the first type of exoplanet discovered, in the mid-1990s.

    “Because we’ve known about hot Jupiters for so long, some people kind of think they’re old hat,” says astronomer Rebekah Dawson of Penn State, who coauthored a review about hot Jupiters posted in January at arXiv.org. “But we still by no means have a consensus about how they got so close to their star.”

    Since the first known hot Jupiter, 51 Pegasi b, was confirmed in 1995, two explanations for that proximity have emerged. A Jupiter that formed past the star’s snow line could migrate in smoothly through the disk by trading orbital positions with the disk material itself in a sort of gravitational do-si-do. Or interactions with other planets or a nearby star could knock the planet onto an extremely elliptical or even backward orbit (SN Online: 11/1/13). Over time, the star’s gravity would steal energy from the orbit, shrinking it into a tight, close circle. Dawson thinks both processes probably happen.

    Hot Jupiters are more common around stars that contain a lot of elements heavier than hydrogen and helium, which astronomers call metals, astronomer Erik Petigura of Caltech and colleagues reported in February in The Astronomical Journal. High-metal stars probably form more planets because their disks have more solids to work with. Once a Jupiter-sized planet forms, a game of gravitational billiards could send it onto an eccentric orbit — and send smaller worlds out into space. That fits the data, too; hot Jupiters tend to lack companion worlds.

    Hoptunes follow the same pattern: They prefer metal-rich stars and have few sibling planets. But Hoptunes probably arrived at their hot orbits later in the star’s life. Getting close to a young star, a Hoptune would risk having its atmosphere stripped away. “They’re sort of in the danger zone,” Dawson says. Since Hoptunes do, in fact, have atmospheres, they were probably knocked onto an elliptical, and eventually close-in, orbit later.

    One striking exception to the hot loner rule is WASP-47b, [ApJL] a hot Jupiter with two nearby siblings between the sizes of Earth and Neptune. That planet is one reason Dawson thinks there’s more than one way to cook up a hot Jupiter.

    Rock or gas

    Hot Jupiters are so large that astronomers assume these exoplanets have thick atmospheres. But it’s harder to tell if a smaller planet is gassy like Neptune or rocky like Earth.

    To make a first guess at a planet’s composition, astronomers need to know the planet’s size and mass. Together, those numbers yield the planet’s density, which gives a sense of how much of the planet is solid like rock or diffuse like an atmosphere.

    HOME SWEET HOMES New images from the Very Large Telescope in Chile reveal that dust disks around young stars can take on many different forms. The shape of a disk can affect – and be affected by – the presence of baby planets.

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    ESO/H. Avenhaus et al./E. Sissa et al./DARTT-S and SHINE collaborations

    The most popular planet detection strategies each measure one of those factors. The transit method, used by the Kepler space telescope, watches a star wink as the planet passes in front.

    NASA/Kepler Telescope

    Planet transit. NASA/Ames

    Comparing the star’s light before and during the transit reveals the planet’s size. The radial velocity method, used with telescopes on the ground, watches the star wobble in response to a planet’s gravity, which reveals the planet’s mass.

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

    Radial Velocity Method-Las Cumbres Observatory

    [Left out of the discussion, Direct Imaging.

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging.

    To me, this is a lapse in journalistic coverage as Direct Imaging is becomeing ao more powerful tool with new telescope capabilities.]

    Most of the stars observed by Kepler are too far away and too dim for direct, accurate measures of planet masses. But astronomers have inferred a size cutoff for rocky planets. Last June, researchers analyzing the full Kepler dataset noticed a surprising lack of planets between 1.5 and two times Earth’s size and suggested those 1.5 times Earth’s radius or smaller are probably rocky; two to 3.5 times Earth’s radius are probably gassy (SN Online: 6/19/17).

    Dozens more planets have had their masses inferred indirectly, mostly those in multiplanet systems where astronomers can observe how planets tug on one another. From what astronomers can tell, super-Earths — planets between one and about 10 times Earth’s mass — come in a wide range of compositions.

    The Kepler mission is about to end, as the spacecraft’s fuel is running out. TESS will pick up where Kepler leaves off. The new planet-hunting space telescope will revolutionize the study of super-Earth densities. It will scan 85 percent of the sky for bright, nearby stars to pick out the best planets for follow-up study. As part of its primary mission, TESS will find at least 50 planets smaller than Neptune that can have their masses measured precisely, too. “Having masses … will help us understand the compositions,” says Quintana, a TESS team member. “We can see: Is there a true transition line where planets go rocky to gaseous? Or is it totally random? Or does it depend on the star?”

    Star power

    All kinds of planets’ fates do, in fact, depend on the stars, Petigura’s recent work suggests. In a February report in The Astronomical Journal, he and colleagues measured the metal contents of 1,305 planet-hosting stars in Kepler’s field of view.

    The researchers learned that large planets and close-in planets — with orbital periods of 10 days or less — are more common around metal-rich stars. But the team was surprised to find that small planets and planets that orbit far from their stars show up around stars of all sorts of compositions. “They form efficiently everywhere,” Petigura says.

    That could mean that metal-rich stars had disks that extended closer to the stars. With enough material close to the star, hot super-Earths could have formed where they currently spin. The existence of hot super-Earths might even suggest that hot Jupiters can form close to the star after all. A super-Earth or mini-Neptune could represent the core of what was once a hot Jupiter that didn’t quite gather enough gas before the disk dissipated, or whose atmosphere was blown off by the star (SN Online: 10/31/17).

    Weird water

    Some scientists are looking to stars to reveal what’s inside a planet. The help is welcome because density is a crude measure for understanding what a planet is made of. Planets with the same mass and radius can have very different compositions and natures — look at hellish Venus and livable Earth.

    Take the case of TRAPPIST-1, which has seven Earth-sized worlds and is 39 light-years away. Astronomers are anxious to check at least three of the planets for signs of life
    (SN: 12/23/17, p. 25). But those planets might be so waterlogged that any signs of life would be hard to detect, says exogeologist Cayman Unterborn of Arizona State. So much water would change a planet’s chemistry in a way that makes it hard to tell life from nonlife. Based on the planets’ radii (measured by their transits) and their masses (measured by their gravitational influence on one another), Unterborn and colleagues used density to calculate a bizarre set of interiors for the worlds, which the team reported March 19 in Nature Astronomy.

    The TRAPPIST-1 planets have low densities for their size, Unterborn says, suggesting that their masses are mostly light material like water ice. TRAPPIST-1b, the innermost planet, seems to be 15 percent water by mass (Earth is less than 0.1 percent water). The fifth planet out, TRAPPIST-1f, may be at least half water by mass. If the planet formed with all that water already in it, it would have had 1,000 Earth oceans’ worth of water. That amount of water would compress into exotic phases of ice not found at normal pressures on Earth. “That is so much water that the chemistry of how that planet crystallized is not something we have ever imagined,” Unterborn says.

    Size it up

    Measuring a planet’s mass and radius gives astronomers a sense of planetary makeup. This plot compares the TRAPPIST-1 planets (purple) with Earth, Venus, an exoplanet named K2-229b and a couple of other worlds.


    Source: A. Santerne et al/Nature Astronomy 2018


    But there’s a glitch. Unterborn’s analysis was based on the most accurate published masses for the TRAPPIST-1 worlds at the time. But on February 5, the same day his paper was accepted in Nature Astronomy, a group led by astronomer Simon Grimm of the University of Bern in Switzerland posted more precise mass measurements at Astronomy and Astrophysics. Those masses make the soggiest planets look merely damp.

    Clearly, Unterborn says, density is not destiny. Studying a planet based on its mass and radius has its limits.

    Looking deeper

    As a next step, Unterborn and colleagues have published a series of papers suggesting how stellar compositions can tell the likelihood that a group of planets have plate tectonics, or how much oxygen the planet atmospheres may have. Better geologic models may ultimately help reveal if a single planet is habitable.

    But Unterborn is wary of translating composition from a star to any individual planet — existing geochemical models aren’t good enough. The recent case of K2-229b makes that clear. Astronomer Alexandre Santerne of the Laboratory of Astrophysics of Marseille in France and colleagues recently tried to see if a star’s composition could describe the interior of its newly discovered exoplanet, K2-229b. The team reported online March 26 in Nature Astronomy that the planet has a size similar to Earth’s but a makeup more like Mercury’s: 70 percent metallic core, 30 percent silicate mantle by mass. (The researchers nicknamed the planet Freddy, for Queen front man Freddie Mercury, Santerne wrote on Twitter.) That composition is not what they’d expect from the star alone.

    Hints from the star

    Based on its mass and radius, an exoplanet named K2-229b is about Earth’s size but more similar to Mercury in composition, astronomers suggest.


    Source: A. Santerne et al/Nature Astronomy 2018


    Geologic models need to catch up quickly. After TESS finds the best worlds for follow-up observations, the James Webb Space Telescope, due to launch in 2020, will search some of those planets’ atmospheres for signs of life (SN: 4/30/16, p. 32). For that strategy to work, Unterborn says, scientists need a better read on the exoplanet cookbook.

    Christy Till’s pressure-packed test kitchen may help. Till is primarily a volcanologist who studies how magma erupting onto Earth’s surface can reveal conditions in Earth’s interior. “The goal is to start doing that for exoplanets,” she says.

    Till and colleagues are redoing some foundational experiments conducted for Earth 50 years ago but not yet done for exoplanets. The experiments predict which elements can go into planets’ mantles and cores, and which will form solid crusts. (Early results that Till presented in December in New Orleans at the American Geophysical Union meeting suggest that multiplying the sun’s magnesium-to-silicon ratio by 1.33 still bakes a rocky planet, but with a different flavored crust than Earth’s.)

    Till uses three piston cylinders to squash and singe synthetic exoplanets for 24 hours to see what minerals form and melt at different pressures and temperatures. The results may help answer questions like what kind of lava would erupt on a planet’s surface, what would the crust be made of and what gases might end up in the planet’s atmosphere.

    It’s early days, but Till’s recipe testing may mean scientists won’t have to wait decades for telescopes to get a close enough look at an exoplanet to judge how much like home it really is. With new cookbook chapters, Unterborn says, “we can figure out which stars are the best places to build an Earth.”

    Related journal articles
    See the full article for further references with links.

    See the full article here .

    Please help promote STEM in your local schools.


    Stem Education Coalition

    ASU is the largest public university by enrollment in the United States.[11] Founded in 1885 as the Territorial Normal School at Tempe, the school underwent a series of changes in name and curriculum. In 1945 it was placed under control of the Arizona Board of Regents and was renamed Arizona State College.[12][13][14] A 1958 statewide ballot measure gave the university its present name.
    ASU is classified as a research university with very high research activity (RU/VH) by the Carnegie Classification of Institutions of Higher Education, one of 78 U.S. public universities with that designation. Since 2005 ASU has been ranked among the Top 50 research universities, public and private, in the U.S. based on research output, innovation, development, research expenditures, number of awarded patents and awarded research grant proposals. The Center for Measuring University Performance currently ranks ASU 31st among top U.S. public research universities.[15]

    ASU awards bachelor’s, master’s and doctoral degrees in 16 colleges and schools on five locations: the original Tempe campus, the West campus in northwest Phoenix, the Polytechnic campus in eastern Mesa, the Downtown Phoenix campus and the Colleges at Lake Havasu City. ASU’s “Online campus” offers 41 undergraduate degrees, 37 graduate degrees and 14 graduate or undergraduate certificates, earning ASU a Top 10 rating for Best Online Programs.[16] ASU also offers international academic program partnerships in Mexico, Europe and China. ASU is accredited as a single institution by The Higher Learning Commission.

    ASU Tempe Campus
    ASU Tempe Campus

  • richardmitnick 10:43 am on May 4, 2018 Permalink | Reply
    Tags: , , , , Radial velocity method, ,   

    From MIT News: “Ushering in the next phase of exoplanet discovery” 

    MIT News
    MIT Widget

    MIT News

    May 3, 2018
    Lauren Hinkel | Oceans at MIT


    “TESS is trying to take everything that people have already done and do it better and do it across the whole sky,” says Sara Seager, the Class of 1941 Professor at MIT.
    Photo: Justin Knight.

    TESS will survey the sky in a series of 13 observing segments, each 27-days long. It will spend the first year on the southern ecliptic hemisphere and the second year on the northern ecliptic hemisphere. Depending on sky position, TESS targets will be observed for a minimum of 27 days up to a maximum of 351 days. Image: Roland Vanderspek.

    Professor Sara Seager previews a new era of discovery as a leader of the TESS mission, which is expected to find some 20,000 extrasolar planets.

    A SpaceX Falcon 9 rocket lifted off on April 18 from Cape Canaveral Air Force Station carrying NASA’s Transiting Exoplanet Survey Satellite, or TESS. The MIT-led mission is the next step in the search for planets outside of the solar system and orbiting other nearby stars. The mission is designed to find exoplanets by blocking their light while the planets transition across. Video: NASA

    Ever since scientists discovered the first planet outside of our solar system, 51 Pegasi b, the astronomical field of exoplanets has exploded, thanks in large part to the Kepler Space Telescope.

    NASA/Kepler Telescope

    Now, with the successful launch of the Transiting Exoplanet Survey Satellite (TESS), Professor Sara Seager sees a revolution not only in the amount of new planetary data to analyze, but also in the potential for new avenues of scientific discovery.

    “TESS is going to essentially provide the catalog of all of the best planets for following up, for observing their atmospheres and learning more about them,” Seager says. “But it would be impossible to really describe all the different things that people are hoping to do with the data.”

    For Seager, the goal is to sift through the plethora of incoming TESS data to identify exoplanet candidates. Ultimately, she says she wants to find the best planets to follow up with atmosphere studies for signs that the planet might be suitable for life.

    “When I came to MIT 10 years ago, [MIT scientists] were starting to work on TESS, so that was the starting point,” said Seager, the Class of 1941 Professor Chair in MIT’s Department of Earth, Atmospheric and Planetary Sciences with appointments in the departments of Physics and Aeronautics and Astronautics.

    Seager is the deputy science director of TESS, an MIT-led NASA Explorer-class mission. Her credentials include pioneering exoplanet characterization, particularly of atmospheres, that form the foundation of the field. Seager is currently hunting for exoplanets with signs of life, and TESS is the next step on that path.

    So far, scientists have confirmed 3,717 exoplanets in 2,773 systems. As an all-sky survey, TESS will build on this, observing 85 percent of the cosmos containing more than 200,000 nearby stars, and researchers expect to identify some 20,000 exoplanets.

    “TESS is trying to take everything that people have already done and do it better and do it across the whole sky,” Seager says. While this mission relies on exoplanet hunting techniques developed years ago, the returns on this work should extend far into the future.

    Planet transit. NASA/Ames

    Radial Velocity Method-Las Cumbres Observatory

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

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging.

    “TESS is almost the culmination of a couple of decades of hard work, trying to iron out the wrinkles of how to find planets by the transiting method. So, TESS isn’t changing the way we look for planets, more like it’s riding on the wave of success of how we’ve done it already.”

    The TESS science leadership team have committed to delivering at least 50 exoplanets with radii less than four times that of Earth’s along with measured masses. As part of the TESS mission, an international effort to further characterize the planet candidates and their host stars down to the list of 50 with measured masses will be ongoing, using the best ground-based telescopes available.

    For the best exoplanets for follow up, Seager likens photons reaching the satellite’s cameras to money: the more photons you have, the better. Accordingly, the cameras are optimized for nearby, bright stars. Furthermore, the cameras are calibrated to favor small, red M dwarf stars, around which small planets with a rocky surface are more easily detected than around the larger, yellow sun-size stars. Additionally, researchers tuned the satellite to exoplanets with orbits of less than 13 days, so that two transits are used for discovery.

    See the full article here .

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  • richardmitnick 9:23 pm on May 2, 2018 Permalink | Reply
    Tags: , , , , , Exoplanet Fomalhaut b On the Move, , Radial velocity method,   

    From Many Worlds: “Exoplanet Fomalhaut b On the Move” 

    NASA NExSS bloc


    Many Words icon

    Many Worlds

    Marc Kaufman

    Enlarge on the full blog post or the full article and enjoy. Fomalhaut b on its very long (1,700 year) and elliptica orbit, as seen here in five images taken by the Hubble Space Telescope over seven years. The reference to “20 au” means that the bar shows a distance of 20 astronomical units, or 20 times the distance from the sun to the Earth. (Jason Wang/Paul Kalas; UC Berkeley)

    Direct imaging of exoplanets remains in its infancy, but goodness what a treat it is already and what a promise of things to come.

    Almost all of the 3,714 exoplanets confirmed so far were detected via the powerful but indirect transit and radial velocity methods — measures of slightly decreased light as a planet crosses in front of its star, or the measured wobble of a star caused by the gravitational pull of a planet.

    But now 44 planets have also been detected by telescopes — in space and on the ground — looking directly at distant stars. Using increasingly sophisticated coronagraphs to block out the blinding light of the stars, these tiny and often difficult-to-identify specks are nonetheless results that are precious to scientists and the public.

    To me, they make exoplanet science accessible as perhaps nothing else so far. Additionally, they strike me as moving — and I don’t mean in orbit. Rather, as when you see your own insides via x-rays or MRIs, direct imaging of exoplanets provides a glimpse into the otherwise hidden realities of our world.

    And in the years ahead – actually, most likely the decades ahead — this kind of direct imaging of our astronomical neighborhood will become increasingly powerful and common.

    This is how the astronomers studying the Fomalhaut system describe what you are seeing:

    “The Fomalhaut system harbors a large ring of rocky debris that is analogous to our Kuiper belt. Inside this ring, the planet Fomalhaut b is on a trajectory that will send it far beyond the ring in a highly elliptical orbit.

    “The nature of the planet remains mysterious, with the leading theory being the planet is surrounded by its own ring or a sphere of dust.”

    An animated simulation of one possible orbit for Fomalhaut b derived from the analysis of Hubble Space Telescope data between 2004 and 2012, presented in January 2013 by astronomers Paul Kalas and James Graham of Berkeley, Michael Fitzgerald of UCLA and Mark Clampin of NASA/Goddard. (Paul Kalas)

    Fomalhaut b was first described in 2008 by Paul Kalas, James Graham and colleagues at the University of California, Berkeley. If not the first object identified through direct imaging — a brown dwarf failed star preceded it, as well as other objects that remain planet candidates — Fomalhaut was among the very first.

    Direct imaging-This false-color composite image traces the motion of the planet Fomalhaut b, a world captured by direct imaging. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley and SETI Institute)

    The data came via the Advanced Camera for Surveys [ACS] on the Hubble Space Telescope.

    NASA/ESA Hubble ACS

    NASA/ESA Hubble Telescope

    But Fomalhaut b is an unusual planet by any standard, and that resulted in a lot of early debate about whether it really was a planet. Early efforts to confirm the presence of the planet failed, in part because the efforts were made in the infrared portion of the spectrum.

    Instead, Fomalhaut b had been detected only in the optical portion of the spectrum, which is uncommon for a directly imaged planet. More specifically, it reflects bluish light, which again is unusual for a planet. Some contended that the planet detection made by Hubble was actually a noise artifact.

    A pretty serious debate ensued in 2011 but by 2013 the original Hubble data had been confirmed by two teams and its identity as a planet was broadly embraced, although the noise of the earlier debate to some extent remains.

    As Kalas told me, this is probably because “no one likes to cover the end of a debate.” Nonetheless, he said, it is over.

    “Fomalhaut b at age 440 Myr (.44 billion years) is much older than the other directly imaged planets,” Kalas explained. “The younger the planet, the greater the infrared light it emits. Thus it is not particularly unusual that it is hard to image planets in the Fomalhaut system using infrared techniques.”

    Kalas believes that a ring system around the planet could be reflecting the light. Another possibility, he said, is that two dwarf planets collided and a compact dust cloud surrounding a dwarf planet is moving through the Fomalhaut system.

    That scenario would be very difficult to test, he said, but the alternate possibility of a Saturnian exoplanet with a ring is something that the James Webb Space Telescope will be able to explore.

    In any case, the issue of whether or not the possibly first directly-imaged planet is in fact a planet has been resolved for now.

    When the International Astronomical Union held a global contest to name some of the better known exoplanets several years ago, one selected for naming was Fomalhaut b, which also now has the name “Dagon.” The star Fomalhaut is the brightest in the constellation Pisces Australis — the Southern Fish — and Dagon was a fish god of the ancient Philistines.

    This animated video of Beta Pictoris and its exoplanet was made using nine images taken with the Gemini Planet Imager over more than two years years. The planet is expected to come our from behind its star later this year, and the GPI team hopes to capture that event. (Jason Wang; UC Berkeley, Gemini Planet Imager Exoplanet Survey)

    NOAO Gemini Planet Imager on Gemini South

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    While instruments on the W.M. Keck Observatory in Hawaii, the European Very Large Telescope in Chile and the Hubble Space Telescope have succeeded in directly imaging some planets, the attention has been most focused on the two relatively newcomers. They are the Gemini Planet Imager (GPI), now on the Gemini South Telescope in Chile [above] and funded largely by American organizations and universities, and the largely European Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument, also in Chile.

    Keck Observatory, Maunakea, Hawaii, USA.4,207 m (13,802 ft), above sea level, showing also NASA’s IRTF and NAOJ Subaru

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    ESO/SPHERE extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    ESO SPHERE extreme adaptive optics system and coronagraphic facility on the extreme adaptive optics system and coronagraphic facility on the VLT, Cerro Paranal, Chile, with an elevation of 2,635 metres (8,645 ft) above sea level

    In real time, the two instruments correct for distorting atmospheric turbulences around Earth and also block the intense light of the host stars. Any residual incoming light is then scrutinized, and the brightest spots suggest a possible planet and can be photographed as such.

    The ultimate goal is have similar instruments improved until they are powerful enough to read the atmospheres of the planets through spectroscopy, which has been done so far only to a limited extent.

    Kalas, Graham and Jason Wang (a graduate student at Berkeley who put together the direct imaging movies ) are part of the GPI team, which since 2014 has been searching for Jupiter-sized and above planets orbiting some distance from their suns. The group is a member of NASA’s NExSS initiative to encourage exoplanet scientists from many disciplines to work together.

    While GPI has had successes detecting important exoplanets such as 51 Eridani b, it also studies already identified planets to increase understanding of their orbits and their characteristics.

    The Gemini Planet Imager when it was being connected to the Gemini South Telescope in Chile. (Gemini Observatory)

    GPI has been especially active in studying the planet Beta Pictoris b, a super Jupiter discovered using data collected by the European Southern Observatory Very Large Telescope. While the data was first collected in 2003, it took five years to tease out the planet orbiting the young star and it took several more years to confirm the discovery and begin characterizing the planet.

    GPI has followed Beta Pictoris b for several years now, compiling orbital and other data used for video above.

    The planet is currently behind its sun and so cannot be observed. But James Graham told me that the planet is expected to emerge late this year or early next year. It remains unclear, Graham said, whether GPI will be able to capture that emergence because it will soon be moved from the Gemini telescope in Chile to the Gemini North Telescope on Hawaii. But he certainly hopes that it will be allowed to operate until the planet reappears.

    The planet 51 Eridani b was the first exoplanet discovered by the GPI and remains one of its most important. The planet is a million times fainter than its parent star and shows the strongest methane signature ever detected on an alien planet, which should yield additional clues as to how the planet formed.

    The four-year GPI campaign from Chile has not discovered as many Jupiter-and-greater sized planets as earlier expected. Graham said that may well be because there are fewer of them than astronomers predicted, or it may be because direct imaging is difficult to do.

    But Graham said the campaign is actually nowhere near over. Much of the data collected since 2014 remains to be studied and teased apart, and other Jupiters and super Jupiters likely are hidden in the data.

    Right now the exoplanet science community, and especially those active in direct imaging, are anxiously awaiting a decision by NASA, and then Congress, about the fate of the Wide Field Infrared Survey Telescope (WFIRST.)

    Designed to be the first space telescope to carry a coronagraph and consequently a major step forward for direct imaging, it was scheduled to be NASA’s big new observatory of the 2020s.

    But the Trump Administration cancelled the mission earlier this year, Congress then restored it but with the caveat that NASA had to provide a detailed plan for its science, its technology and its cost. That plan remains an eagerly-awaited work in progress.

    Meanwhile, here is another example of what direct imaging, with the help of soon-to-be Caltech postdoc Jason Wang, can provide. The video of the HR 8799 system went viral when first made public in early last year.

    The four planet system orbiting the planet HR 8977, first partially identified in 2008 by Christian Marois of the National Research Council of Canada’s Herzberg Institute of Astrophysics and Bruce Macintosh of Stanford and others. The video was created in 2017 after all four planets had been identified via direct imagine and their orbits had been followed for some years. (Jason Wang of UC Berkeley/Christian Marois of NRC Herzberg.)

    The promise of direct imaging is enormous. The collected photons can be used for spectroscopy that can potentially tell scientists about a planet’s radius, mass, age, effective temperature, clouds, molecular composition, rotation rate and atmospheric dynamics.

    For a small, potentially habitable planet, direct imaging can measure surface temperate and pressure and determine whether it can support liquid water. It can also potentially determine if the atmosphere is in the kind of disequilibrium regarding oxygen, ozone and perhaps methane that signal the presence of life.

    But almost all this is in the future since none of the current instruments are powerful enough to collect that data.

    University of California at Berkeley astronomy grad student Lea Hirsch at [the very important to me] Lick Observatory [at UCSC, on Mt Hamilton This was the location running the UCO system under the great Sandra Faber, who was a major contributor to the salvation of Hubble with COSTAR]. She will be going soon to Stanford University for a postdoc with Gemini Planet Imager Principal Investigator Bruce Macintosh.

    In the meantime, researchers such as Berkeley graduate student Lea Hirsch, soon to be a Stanford postdoc, are focused on using the strengths of the different detection methods to come up with constraints on exoplanetary characteristics (such as mass and radius) that one technique alone could not provide.

    For instance, the transit technique works best for identifying planets close to their stars, direct imaging is the opposite and radial velocity is best that detecting large and relatively close-in planets. Radial velocity gives a minimum (but not maximum) mass, while transits provide an exoplanet radius.

    Planet transit. NASA/Ames

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

    Radial Velocity Method-Las Cumbres Observatory

    What Hirsch would like to do is determine constraints (limits) on the size of exoplanets using both radial velocity measurements and direct imaging.

    As she explained, radial velocity will give that minimum mass, but nothing more in terms of size. But in an indirect way for now, direct imaging can provide some maximum mass.

    If, for instance, astronomers know through the radial velocity method that exoplanet X orbits a certain star and is twice the size of Jupiter, they can then look for it using direct imaging with confidence that something is there. Let’s say the precision of the imaging is such that if a planet six times the size of Jupiter was present they would — over a period of time — detect it.

    A detection would indeed be great and the planet’s mass (and more) would then be known. But if no planet is detected — as often happens — then astronomers still collect important information. They know that the planet they are looking for is less than six Jupiter masses. Since the radial velocity method already determined it was at least larger than two Jupiters, scientists would then know that the planet has a mass of between two and six Jupiters.

    “All the techniques in our toolkit {of exoplanet searching} have their strengths and weaknesses,” she said. “But using those techniques together is part of our future because there’s a potential to know much more.”

    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 12:57 pm on December 24, 2017 Permalink | Reply
    Tags: , , , , Can we constrain planetary mineralogy of the closest stars?, , Radial velocity method,   

    From astrobites: “Can we constrain planetary mineralogy of the closest stars?” 

    Astrobites bloc


    Dec 23, 2017
    Leonardo dos Santos

    Article: The Star-Planet Connection I: Using Stellar Composition to Observationally Constrain Planetary Mineralogy for the Ten Closest StarsAuthors: Natalie Hinkel and Cayman Unterborn
    First author’s institution: Department of Physics & Astronomy, Vanderbilt University

    Status: Submitted to AAS Journals

    Phase diagram of the simulated interior of an Earth-like planet. It shows the different compounds that make up the mantle for varying depths. No image credit.

    We get excited when hearing the news of a newly discovered planet inside the habitability zone of a star. But caution is advised: being actually habitable is much more involved than simply having the right amount of irradiation. Other aspects such as the chemical composition of a planet’s atmosphere and crust are key for life as we know it to flourish. The challenging nature of precisely measuring the chemistry of stars is daunting but, according to today’s paper, we may actually be capable of inferring about planetary mineralogy for our closest extrasolar neighbors.

    Another dimension to habitability

    Since directly measuring the composition of the solid innards of an exoplanet is far beyond our current capabilities, we often rely on indirect methods to infer about their bulk composition. For instance, if we measure the radius of a planet using the transit method and then its mass using radial velocities, then we can estimate its density.

    Planet transit. NASA/Ames

    Las Cumbres Observatory

    But this relation doesn’t provide enough fine details to allow an inference about, say, the size and composition of the core and mantle of the planet — i.e., its mineralogy. However, our current hypotheses on how planetary systems form suggest that the chemical composition of a star and the planets that orbit around it should be strongly connected. This means that, in principle, we could infer about the mineralogy of a planet if know the composition of the host star well enough.

    Relative chemical abundances are key to habitability, such as the molar (number of atoms) ratio between iron and magnesium (Fe/Mg), which affects the size of a planet’s core and consequently the heat transfer to the surface. Another example is the presence of volatile elements (those that like to stay in gaseous phase) in the crust, which influence tectonic movement and geochemical cycles. The major controls in planetary mineralogy are the ratios of the elements magnesium, aluminum, silicon, calcium, and iron. Such ratios are routinely measured in atmospheres of stars, although with varying degrees of precision.

    The overall idea of today’s paper is to assess if we can measure these abundances in stars in the solar neighborhood precisely enough to make any inferences about the mineralogy of putative rocky planets around them. In order to do that, the authors used the Hypatia Catalog of stellar measurements: they selected 10 nearby well-known stars with reliable chemical abundance estimates and started digging (see Fig. 1).

    Figure 1. Molar ratios (fraction of the number of atoms) of silicon and iron over magnesium for the entire Hypatia Catalog (red symbols) and the selected 10-star sample plus the Sun (black dots). These stars were selected for their low uncertainties in molar ratios.

    See the full article here .

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    What do we do?

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

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

  • richardmitnick 3:22 pm on December 7, 2017 Permalink | Reply
    Tags: , , , , , Radial velocity method, This telescope is supposed to measure the diameter of exoplanets which are light-years away from us and pass in front of their host star, ,   

    From University of Bern: ‘The history of CHEOPS” 

    The University of Bern

    Engineers at the University of Bern are developing the CHEOPS space telescope. From Earth´s orbit, this telescope is supposed to measure the diameter of exoplanets which are light-years away from us and pass in front of their host star. Swiss astronomers had the idea for CHEOPS back in 2008.


    Willy Benz, professor at the Physics Institute at the University of Bern, actually wanted to travel during a semester-long sabbatical in 2008. Instead of spending this sabbatical at foreign universities, the astrophysicist sat at his desk at home and worked on a research proposal. The Swiss National Science Foundation had announced that they would be appointing new National Centres of Competence in Research (NCCR) and Willy Benz wanted to submit a proposal for planetary research together with his colleague in Geneva, Didier Queloz.

    In 1995 the former doctoral student Queloz and his supervising professor Michel Mayor discovered the first exoplanet orbiting a sun-like star. Benz also received his doctorate from Mayor at the University of Geneva nine years earlier. Already in 2000, Benz submitted a proposal for a National Centre of Competence in Research on exoplanetary research to the National Science Foundation, but his proposal was rejected. “That’s science fiction, they told me in an interview back then,” recalls the astrophysicist. In the year 2000, dozens of exoplanets had already been identified, in 2008 there were 300, today there are more than 3,000.

    Testing CHEOPS in the thermal vacuum chamber at the University of Bern. (Photo UniBern)

    The first of these distant planets orbiting sun-like stars were discovered by astronomers who were able to demonstrate that the host stars move periodically towards and away from us because both star and planet rotate around their common centre of mass under the influence of gravity. This technique is called the radial velocity method. It works well with bright stars (at least 11 mag) and provides measurements to calculate the mass of the planet. Soon astronomers also used a second method: If a planet passes directly in front of its star, it causes a kind of mini-eclipse; the brightness of the star periodically decreases by a tiny fraction. Thanks to these so-called transits, the diameter of the planet can be determined. The French satellite COROT, which was launched in 2006, and later NASA’s Kepler mission, used the transit method with great success.

    Raial Veocity Method. Las Cumbres Observatory

    Planet transit. NASA/Ames


    NASA/Kepler Telescope

    Progress thanks to new instruments

    “In the field of astrophysics today, progress is mostly made thanks to new instruments,” explains Benz. “When we worked on our second NCCR proposal in 2008, we wanted to propose not only scientific research projects but also the construction of hardware, including a Swiss exoplanetary satellite.” This satellite was supposed to be unique because of a new observation strategy. “Transit measurement is a great method,” explains the expert, “but, unfortunately, it has almost only identified planets whose stars are not very bright.” Their average magnitude is only 14 to 15. The explanation for this is that only a very small percentage of the stars are orbited by planets whose orbits lie exactly in our line of sight. If you really want to discover transits, you have to target a large number of stars. COROT and Kepler targeted about 100,000, but this was only possible because the satellites were limited to a narrow region. The bright stars, however, are spread all over the sky.

    “At the time, we thought it would be possible to build a small satellite that would not focus on a narrow area, but would observe bright stars everywhere in the sky, stars that are already known to possess a planet because of the radial velocity method,” Benz explains. The combination of the two detection methods is particularly interesting. If the mass is known on the basis of the radial velocity and the diameter of a planet is known due to the transit, its density can be calculated. “We then know whether the planet is mainly composed of rock or gas,” says Benz – a particularly important result in the context of the search for Earth-like planets.

    Professor Willy Benz with a 1:2 scale model of CHEOPS. (Photo Alessandro Della Bella)

    In 2009, Benz and Queloz submitted their applications for a National Centre of Competence in Research, including a feasibility study for a space telescope. When searching for the name of the satellite, the astrophysicists knew that “CH” for Switzerland would come at the beginning and that the abbreviation should be catchy. This is how they came up with “CH ExOPlanet Satellite” or CHEOPS for short. The application for planetary research was one of 13 projects that the National Science Foundation rated as excellent with a grade of A. “Unfortunately, the project was not chosen in the end,” Benz says, “I was very disappointed, having sacrificed my entire sabbatical.”

    Persistence pays off

    The astrophysicist did not give up and was later able to negotiate with the rector of the University of Berne and the State Secretary for Education and Research on how the dream of a Swiss satellite could still be pursued. As a result of his persistence, the federal government and RUAG financed the feasibility report as industrial representatives, and the University of Bern founded the “Center for Space and Habitability” (CSH). “In the feasibility report, we quickly realized that the satellite project alone would be too expensive for Switzerland,” Benz says. Sweden and Austria, where RUAG operated its branches, were the first European partners, and others soon followed.

    While the Swiss were still working on the CHEOPS feasibility study, the European Space Agency (ESA) was discussing the possibility of a new satellite programme. In addition to the existing large and medium-sized (L- and M-class) missions, the smaller ESA member states in particular wanted to launch an S-class mission. The development time for these missions should not exceed four years and the cost should not exceed a prescribed limit set by ESA. The ESA Member States agreed on an experiment and issued a first S-mission call in March 2012.

    As chairman of the scientific committee advising ESA, Benz was well informed about the discussions and decisions of the ESA delegates – and was prepared to participate in the call for proposals with the CHEOPS study. While most of the others had only three months to work out their proposals, the Swiss could rely on the extensive preparatory work done in the feasibility study and benefit from Benz’s ‘insider’ knowledge. “I knew the objections and doubts that some ESA delegates had previously put forward, and I made sure that we went in the right direction in our proposal and, for example, prevented cost explosions.” Although they originally wanted to use CHEOPS to observe the transits in two different wavelengths, they decided against an infrared instrument for cost reasons.

    No holiday plans

    The CHEOPS team at the University of Bern assembles the flight model in the clean room. (Photo PlanetS)

    In June 2012, Benz submitted the proposal for the CHEOPS mission, now called ‘CHaracterizing ExOPlanets Satellite’. It was one of 26 proposed projects submitted. When the ESA Scientific Panel met in Madrid in October 2012 to select the winner, Chairman Benz stayed away from the conference because of his conflict of interest and waited in his Bern office for a call from the committee’s secretary. “I remember his first sentence very well,” Benz says. “He said, ‘you shouldn’t make any plans for holidays in the next four years’.”

    CHEOPS started as a joint project between Switzerland and ESA. The University of Bern is responsible for the construction of the space telescope and heads the consortium of 11 ESA member states participating in the mission. The satellite platform will be built in Spain. The mission’s operations centre is also located there, while the research centre is being set up at the University of Geneva. The launch is scheduled for the end of 2018 with a Soyuz rocket from Kourou. ESA will bear half of the total costs of around 100 million Euros. Switzerland will contribute around 30 million Euros, while the other partners involved will contribute the remainder of the finances needed for this undertaking.

    “Although we were not selected by the National Science Foundation in 2009, everything worked out very nicely in the end,” concludes Benz. “Despite the additional stress and a lot of work, we were able to start our projects and are now close to the launch!” In addition, The National Research Centre was also awarded to the planetary scientists on their third attempt. In June 2014, Willy Benz and co-director Stéphane Udry, professor at the University of Geneva, launched the NCCR PlanetS, in which the ETH Zurich and ETH Lausanne, as well as the University of Zurich are also involved. “This shows that you should never give up,” says Willy Benz. (bva)

    For more information please visit http://cheops.unibe.ch

    See the full article here .

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    The University of Bern (German: Universität Bern, French: Université de Berne, Latin: Universitas Bernensis) is a university in the Swiss capital of Bern and was founded in 1834.[2] It is regulated and financed by the Canton of Bern. It is a comprehensive university offering a broad choice of courses and programs in eight faculties and some 150 institutes. With around 17,512 students, the University of Bern is the third biggest University in Switzerland.

    The University of Bern operates at three levels: university, faculties and institutes. Other organizational units include interfaculty and general university units. The university’s highest governing body is the Senate, which is responsible for issuing statutes, rules and regulations. Directly answerable to the Senate is the University Board of Directors, the governing body for university management and coordination. The Board comprises the Rector, the Vice-Rectors and the Administrative Director. The structures and functions of the University Board of Directors and the other organizational units are regulated by the Universities Act. The University of Bern offers about 39 bachelor and 72 master programs, with enrolments of 7,747 and 4,523, respectively. The university also has 2,776 doctoral students. Around 1,561 bachelor, 1,489 master’s degree students and 570 PhD students graduate each year. For some time now, the university has had more female than male students; at the end of 2016, women accounted for 56% of students.

  • richardmitnick 1:37 pm on April 13, 2016 Permalink | Reply
    Tags: , , , Radial velocity method   

    From Many Worlds: “Storming the One-Meter-Per-Second Barrier” 

    NASA NExSS bloc


    Many Worlds

    Many Words icon

    Marc Kaufman

    NOAO Kitt Peak National Observatory
    NOAO Kitt Peak National Observatory
    The Kitt Peak National Observatory, on the Tohono O’odham reservation outside Tucson, will be home to a next-generation spectrometer and related system which will allow astronomers to detect much smaller exoplanets through the radial velocity method. P. Marenfeld (NOAO/AURA/NSF)

    When the first exoplanet was identified via the radial velocity method, the Swiss team was able to detect a wobble in the star 51 Pegasi at a rate of 50 meters per second. The wobble is the star’s movement back and forth caused by the gravitational pull of the planet, and in that first case it was dramatic — the effects of a giant Jupiter-sized planet orbiting extremely close to the star.

    Many of the early exoplanet discoveries were of similarly large planets close to their host stars, but it wasn’t because there are so many of them in the cosmos. Rather, it was a function of the capabilities of the spectrographs and other instruments used to view the star. They were pioneering breakthroughs, but they didn’t have the precision needed to measure wobbles other than the large, dramatic ones caused by a close-in, huge planet.

    That was the mid 1990s, and radial velocity astronomers have worked tirelessly since to “beat down” that 50 meters per second number. And twenty years later, RV astronomers using far more precise instruments and more refined techniques have succeeded substantially: 1 meter per second of wobble is now achieved for the quietest stars. That has vastly improved their ability to find smaller exoplanets further from their stars and is a major achievement. But it has nonetheless been a major frustration for astronomers because to detect terrestrial exoplanets in the Earth-sized range, they have to get much more precise — in the range of tens of centimeters per second.

    A number of efforts to build systems that can get that low are underway, most notably the ESPRESSO spectrograph scheduled to begin work on the High Accuracy Radial Vlocity Planet Searcher (HARPS) in Chile next year. Then earlier this month an ambitious NASA-National Science Foundation project was awarded to Penn State University to join the race. The next-generation spectrograph is scheduled to be finished in 2019 and installed at the Kitt Peak National Observatory in Arizona, and its stated goal is to reach the 20 to 30 centimeters per second range.

    Suvrath Mahadevan, an assistant professor at Penn State, is principal investigator for the project. It is called NEID, which means ‘to see’ in the language of the Tohono O’odham, on whose land the Kitt Peak observatory is located.

    “For many reasons, the (radial velocity) community has been desperate for an instrument that would allow for detections of smaller planets, and ones in habitable zones,” he said. “We’re confident that the instrument we’re building will — in time — provide that capability.”

    A illustration of how the radial velocity method of planet hunting works. The wobble of the stars is far away miniscule in galactic terms, making extreme precision essential in measuring the movement. (Las Cumbres Observatory Global Telescope Network)

    LCOGT Las Cumbres Observatory Global Telescope Network  at Haleakala
    LCOGT Las Cumbres Observatory Global Telescope Network

    Project scientist Jason Wright, associate professor of astronomy and astrophysics at Penn State, put it this way: “NEID will be more stable than any existing spectrograph, allowing astronomers around the world to make the precise measurements of the motions of nearby, Sun-like stars.” He said his Penn State team will use the instrument “to discover and measure the orbits of rocky planets at the right distances from their stars to host liquid water on their surfaces.”

    NASA and the NSF wanted the new spectrograph built on an aggressive timetable to meet major coming opportunities and needs, Mahadevan said.

    The speedy three-year finish date is a function of the role that radial velocity detection plays in exoplanet research. While many planets have been, and will be, first detected through the technique, it is also essential in the confirming of candidate planets identified by NASA space telescopes such as Kepler, the soon-to-be launched TESS (the Transiting Exoplanet Survey Satellite) and others into the future. There is a huge backlog of planets to be confirmed, and many more expected in the relatively near future.

    What’s more, as Mahadevan explained, an instrument like NEID could significantly help NASA’s planning for a possible 2030s Flagship space telescope mission focused on exoplanets. Two of the four NASA contenders under study are in that category — LUVOIR (Large Ultraviolet Visible Infrared) Surveyor and Hab-Ex — and their capabilities, technologies, timetables and cost are all now under consideration.

    If NEID can identify some clearly Earth-sized planets in habitable zones, he said, then the planning for LUVOIR or Hab-Ex could be more focused (and the proposal potentially less costly.) This is because the observatory could be designed to look at a limited number of exoplanets and their host stars, rather than scanning the skies for a clearly Earth-like planet.

    “Right now we have no definite Earth-sized planets in a habitable zone, so a LUVOIR or Hab_ex design would have to include a blind search. But if we know of maybe 15 planets we’re pretty sure are in their habitable zones, the targets get more limited and the project becomes a lot cheaper.”

    These possibilities, however, are for the future. Now, Mahadevan said, the Penn State team has to build a re-considered spectrograph, a significant advance on what has come before. With its track record of approaching their work through interdisciplinary collaboration, the Penn State team will be joined by collaborators from NASA Goddard Space Flight Center, University of Colorado, National Institute of Standards and Technology, Macquarie University in Australia, Australian Astronomical Observatory, and Physical Research Laboratory in India. Much of the work will be done over the next three years at Penn State, but some at the partner institutions as well.

    Key to their assembly approach is that the instrument will be put together in vacuum-sealed environment and will have no vibrating or moving parts. This design stability will prevent, or minimize, instrument-based misreadings of the very distant starlight being analyzed.

    A major issue confronting radial velocity astronomers is that light from stars can fluctuate for many reasons other than a nearby planet — from sunspots, storms, and other magnetic phenomena. The NEID instrument will try to minimize these stellar disruptors by providing the broadest wavelength coverage so far in an exoplanet spectrograph, Mahadevan said, collecting light from well into the blue range of the spectrum to almost the end of the red.

    “We’re not really building a spectorograph but a radial velocity system, he said. That includes upgrades to the telescope port, the data pipeline and more.

    This is how Lori Allen, Associate Director for Kitt Peak, described that new “system”: “The extreme precision (of NEID) results from numerous design factors including the extreme stability of the spectrometer environment, image stabilization at the telescope, innovative fiber optic design, as well as state-of-the-art calibration and data reduction techniques”.

    NOAO WIYN 3.5 meter telescope at Kitt Peak, AZ, USA
    NOAO WIYN 3.5 meter telescope at Kitt Peak, AZ, USA interior
    The new generation spectrograph will be installed on the 3.5 meter WYN telescope at Kitt Peak. The site is managed by the National Optical Astronomy Observatory, and $10 million spectrograph project is a collaboration of NASA and the National Science Foundation.

    Sixteen teams ultimately competed to build the spectrograph, and the final two contenders were Penn State and MIT. Mahadevan said that, in addition to its spectrograph design, he believed several factors helped the Penn State proposal prevail.

    His team has worked for several years on another advanced spectrograph for the Hobby-Eberly Telescope in Texas, one that required complex vacuum-sealed and very cold temperature construction. Although the challenges slowed the design, the team ultimately succeeded in demonstrating the environmental stability in the lab. So Penn State had a track record. What’s more, the school and its Center for Exoplanets and Habitable Worlds have a history of working in an interdisciplinary manner, and have been part of several NASA Astrobiology Institute projects.

    The Kitt Peak observatory, which saw first light in 1994, has been the sight of many discoveries, but in recent years has faced cutbacks in NSF funding. There was some discussion of reducing its use, and the NASA-NSF decision t0 upgrade the spectrograph was in part an effort to make it highly relevant again. And given the scientific need to confirm so many planets — a need that will grow substantially after TESS launches in 2017 or 2018 and begins sending back information on thousands of additional transiting exoplanets — enhancing the capabilities of the Kitt Peak 3.5 meter telescope made sense.

    Kitt Peak is unusual in being open to all comers with a great proposal, whether they’re from the U.S. or abroad. The Penn State team and partners will get a certain number of dedicated night to observe, but many others will be allocated through competitive reviews. And so when NEID is completed, astronomers from around will have a shot at using this state-of-the-art planet finder.

    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.

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