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  • richardmitnick 7:49 am on April 17, 2018 Permalink | Reply
    Tags: , , , , Exoplanets, From NASA Spaceflight: TESS,   

    From NASA Spaceflight: TESS 

    NASA Spaceflight

    NASA Spaceflight

    April 16, 2018
    Chris Gebhardt

    TESS background/overview:


    The original idea for TESS goes back to 2005 when Dr. George Ricker was the Principle Investigator High Energy Transient Explorer (HETE) – the first satellite mission dedicated to the study of gamma-ray bursts. Slowly, the idea evolved in 2008 and 2009, with Dr. Ricker, now TESS’s Principal Investigator at MIT (Massachusetts Institute of Technology), saying “We wanted to initially try to do this as a privately funded system, and MIT was very helpful for us. We had support from Google for some of the studies that were originally going to be done.”

    That led to a collaboration with NASA Ames to create a proposal for a small-class explorer exoplanet mission that was ultimately not selected for flight. That then led to a partnership with Orbital ATK and the Goddard Space Flight Center in Greenbelt, Maryland, for a revised mission proposal over 2011 and 2012.

    TESS was officially selected for inclusion in NASA’s Medium Explorer mission program on 5 April 2013, and with just over five years of design and build operations, now stands ready to launch. “It’s been a long time coming. It’s been 13 years, but for the last five years, basically, pretty much [everything with the mission has been] the same,” said Dr. Ricker.

    TESS undergoes final pre-launch processing at the Kennedy Space Flight Center. Credit: Chris Gebhart for NSF/L2

    While TESS is generally perceived as a follow-on to NASA’s Kepler planet hunting satellite, it will perform a very different kind of mission. Where Kepler was a prolonged, deep, and narrow field observatory that looked continuously at specific stars in one quarter of 1% of the sky at an optimal range of 2,000 to 3,000 light years distance, TESS will perform a wide- and shallow-field survey covering 85% of the sky with an optimal distance stretching to 300 light years.

    TESS will accomplish its observations by using the sole science instrument onboard: a package of four wide-field-of-view CCD cameras with a low-noise, low-power 16.8 megapixel CCD detector. Each camera as a 24° x 24° field of view, a 100 mm (4 in) pupil diameter, a lens assembly with seven optical elements, and a bandpass range of 600 to 1,000 nm.

    When functioning together – as designed – the four cameras have a 24° x 96° field of view.

    The overall spacecraft is built on a LEOStar-2 satellite bus by Orbital ATK. The spacecraft bus is capable of three-axis stabilization via four hydrazine thrusters as well as four reaction wheels. This provides TESS’s cameras with greater than three-arc-second fine pointing control – necessary for the sensitive light observations TESS will perform once in its science orbit.

    The data collected during TESS’s observational campaigns – as well as general spacecraft communications – will route through a Ka-band antenna with a 100 Mbit/s downlink capability. The entire craft is powered by two solar arrays capable of generating 400 watts.

    “There’s more than 100 scientists and other personnel cooperating on the mission,” said Dr. Ricker, “and as far as the mission itself is concerned, all the work that was involved in designing, developing, and building the hardware, we’ve estimated that there’s more than a million person-hours that have gone into that over the past five years.”

    Launch and Orbit:

    The launch phase of the mission will see a Falcon 9 deliver TESS into a lunar transfer orbit, sending the craft to a precise point when the moon’s gravity will grab TESS and fling it out into a farther orbit than it’s initially launched into.

    At 350 kg (772 lb), TESS is the lightest-known payload to have ever launched on a Falcon 9. After lifting off from SLC-40 at the Cape Canaveral Air Force Station, FL, the Falcon 9 will fly due east from the pad. The first stage, after 2 minutes 29 seconds of powered flight, will separate from the second stage and perform a landing on the Of Course I Still Love You drone ship in the Atlantic.

    SpaceX will also attempt to recover the payload fairing, but as there is no fairing catching boat – yet – on the east coast, the fairing will parachute into the ocean for intact recovery, serving primarily as a test of the new recovery systems.

    For the launch, after stage separation, the second stage will continue to fire its single MVac (vacuum optimized Merlin engine) until SECO-1 (Stage Engine Cut Off -1) at 8minutes 22 seconds into flight. This will be followed by a 32 minute 33 second coast of the stage and TESS before the second stage engine re-starts for a burn to send TESS into a Lunar Transfer Orbit.

    Shortly after SECO-2, TESS will separate from the top of the Falcon 9 second stage at 48 minutes 42 seconds after launch having been placed into a super synchronous transfer orbit of 200 x 270,000 km (124 x 167,770 mi). The second stage will then perform a third burn to inject itself into a disposal hyperbolic (Earth-escape) orbit.

    Over the first five days, TESS’s control teams will check out the overall health of the spacecraft before activating TESS’s science instruments 7-8 days after launch. TESS will then perform a final lunar flyby on 16 May – one month after launch, a lunar gravity assist which will change the the craft’s orbital inclination to send it into its 13.7 day, 108,000 x 373,000 km (67,000 x 232,000 mi) science orbit of Earth – an orbit that is in perfect 2:1 resonance with the moon.

    The maneuvers and encounters Leading to the final TESS orbit. PLEA and PLEP are the post lunar-encounter-apogee and perigee, respectively. Credit Ricker et al. 2015.

    The specific orbit, referred to as the P/2 lunar resonant orbit, will place TESS completely outside the Van Allen Radiation belts, with TESS’s apogee (farthest point in orbit from the Earth) approximately 90 degrees away from the position of the Moon. This will minimize the Moon’s potential destabilizing effect on TESS and maintain a stable orbit for decades while also providing a consistent, good camera temperature range for the observatory’s operations.

    Moreover, this orbit will provide TESS with unobstructed views of both the Northern and Southern Hemispheres. For almost all of its orbit, TESS will be in data gathering mode, only transmitting its stored data to Earth once per orbit during the three hours of its closest approach to Earth, or perigee. Assuming an on-time launch, TESS will enter operations on 12 June.

    Overall, TESS has daily launch opportunities from 16-21 April, no launch opportunity on the 22nd (per NASA documentation), and then daily opportunities again from 23-26 April. There is no opportunity on 22 April because the amount of time between the consecutive daily opportunities on 21 and 23 April is just slightly longer than 24 hours, thus barely skipping over all times on the 22nd.

    However, if for some reason TESS is not off the ground by 26 April, the exoplanet hunter must stand down launch operations so that NASA’s Launch Services Provider (LSP) group can shift gears to support the agency’s InSight mission launch to Mars from Vandenberg Air Force Base, California.

    The LSP does not have a large enough staff to support two missions from both coasts, and since InSight has a short interplanetary launch window it must launch within, InSight would get priority over TESS. After InSight, TESS has additional launch opportunities in both May and June.


    Once its checkout phase is complete, TESS will begin its 26 observational campaigns (13 for each hemisphere) to survey 85% of the sky for transiting exoplanets near Earth. Observations will start with the Southern Hemisphere, and those 13 campaigns will last approximately one year.

    According to Dr. Ricker, choosing to survey the Southern Hemisphere first was “a function of the follow-up resources that are currently available. Many of the most powerful telescopes that ground-based astronomers use are located in the Southern Hemisphere.”

    TESS will then be re-aimed to perform the 13 observational campaigns needed to cover the Northern Hemisphere. During all 26 campaigns, the entire south and north polar sky regions will receive near-continuous year-long assessments from TESS’s cameras – as each observation campaign for the Southern and Northern Hemispheres overlap completely at their respective pole.

    Dr. Ricker shows the number of exoplanets TESS is predicted to find within 100 parsecs (326 lightyears) of Earth. Credit Ricker et al. for NSF/L2

    Every 13.7 days, when TESS swings closest to Earth, the craft will downlink its observation data to scientists at MIT who will process it and make it available to other scientists and the public. Specifically, TESS’s team will focus on the 1,000 closest red dwarf stars to Earth as well as nearby G, K, and M type stars with apparent magnitudes greater than 12.

    Over its primary 2 year mission, TESS will observe about half a million stars in an area 400 times larger than the Kepler mission and is expected to find 20,000 exoplanets – including 500-1,000 Earth-sized planets and Super-Earths.

    These planets will be added to the growing number of known exoplanets. According to NASA’s Exoplanet Archive hosted by CalTech, as of 12 April 2018, there are 3,717 known exoplanets with 2,652 of those found by the Kepler Space Telescope.

    TESS’s primary mission duration is two years, during which all of its science objectives are scheduled to be completed. While a mission extension is never a guarantee, TESS can be extended for additional observations based on its design and orbit. “We can extend, because the orbit will be operating and aligned for more than two decades,” said Dr. Ricker. “Now, as is the case for many Explorer missions, we fully expect that there will be an extended mission for TESS, so we pre-designed the satellite and the operation so that it can go on for a much longer time.”

    See the full article here .

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

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

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

  • richardmitnick 9:25 am on February 4, 2018 Permalink | Reply
    Tags: Exoplanets, , ,   

    From Universe Today: “For the First Time, Planets Have Been Discovered in ANOTHER Galaxy!” 


    Universe Today

    3 Feb , 2018
    Matt Williams

    Using the microlensing metthod, a team of astrophysicists have found the first extra-galactic planets! Credit: NASA/Tim Pyle

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

    The first confirmed discovery of a planet beyond our Solar System (aka. an Extrasolar Planet) was a groundbreaking event. And while the initial discoveries were made using only ground-based observatories, and were therefore few and far between, the study of exoplanets has grown considerably with the deployment of space-based telescopes like the Kepler space telescope.

    As of February 1st, 2018, 3,728 planets have been confirmed in 2,794 systems, with 622 systems having more than one planet. But now, thanks to a new study by a team of astrophysicists from the University of Oklahoma, the first planets beyond our galaxy have been discovered! Using a technique predicting by Einstein’s Theory of General Relativity, this team found evidence of planets in a galaxy roughly 3.8 billion light years away.

    The study which details their discovery, titled Probing Planets in Extragalactic Galaxies Using Quasar Microlensing, recently appeared in The Astrophysical Journal Letters. The study was conducted by Xinyu Dai and Eduardo Guerras, a postdoctoral researcher and professor from the Homer L. Dodge Department of Physics and Astronomy at the University of Oklahoma, respectively.

    See the full article here .

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  • richardmitnick 12:29 pm on October 26, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, , Water Worlds Don’t Stay Wet for Very Long   

    From Universe Today: “Water Worlds Don’t Stay Wet for Very Long” 


    Universe Today

    25 Oct , 2017
    Matt Williams

    Artist’s depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)

    When hunting for potentially habitable exoplanets, one of the most important things astronomers look for is whether or not exoplanet candidates orbit within their star’s habitable zone. This is necessary for liquid water to exist on a planet’s surface, which in turn is a prerequisite for life as we know it. However, in the course of discovering new exoplanets, scientists have become aware of an extreme case known as “water worlds“.

    Water worlds are essentially planets that are up to 50% water in mass, resulting in surface oceans that could be hundreds of kilometers deep. According to a new study by a team of astrophysicists from Princeton, the University of Michigan and Harvard, water worlds may not be able to hang on to their water for very long. These findings could be of immense significance when it comes to the hunt for habitable planets in our neck of the cosmos.

    This most recent study, titled The Dehydration of Water Worlds via Atmospheric Losses, recently appeared in The Astrophysical Journal Letters. Led by Chuanfei Dong from the Department of Astrophysical Sciences at Princeton University, the team conducted computer simulations that took into account what kind of conditions water worlds would be subject to.

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  • richardmitnick 11:34 am on September 10, 2017 Permalink | Reply
    Tags: , , At Least 9 Exoplanets Could See Earth With Present-Day Human Technology, , , Exoplanets, , , , Transit photometry   

    From Queens University Belfast and Max Planck Institute for Solar System Research via Motherboard: “At Least 9 Exoplanets Could See Earth With Present-Day Human Technology”… 

    Max Planck Institute for Solar System Research

    QUB bloc

    Queens University Belfast (QUB)



    …But that doesn’t mean anybody’s looking.

    Since the first exoplanet was discovered in 1995, well over 3,500 planets orbiting stars other than our own have been detected. This explosion in exoplanet discovery has largely happened in the last decade due to drastically improved methods of observation. Today, the main instrument in the exoplanet hunter’s toolbox is transit photometry, which detects exoplanets by measuring the decrease in a star’s brightness as a planet passes in front of it.

    Planet transit. NASA/Ames

    Now, a team of scientists from Queen’s University Belfast and the Max Planck Institute for Solar System Research want to know if the same methods could be used by aliens to observe Earth. Based on their initial research [MNRAS], it seems at least nine known exoplanets have a good view of Earth—although none of these are capable of sustaining life as we know it. Still, the researchers estimate that there are ten other planets that are ideally situated to observe Earth and habitable.

    This illustration depicts how Earth causes light from the Sun to dim as it passes in front of it from the vantage point of an observer on an exoplanet. Image: Robert Wells/Queen’s University Belfast

    To understand how an alien on one of these exoplanets might see Earth, the researchers first identified the areas in the sky in which the transit zones—where a planet passes in front of the Sun—of Mercury, Venus, Earth and Mars could be seen. The researchers only focused on the four innermost planets of our solar system because these are the most likely to be observed by an ET using transit photometry.

    “Larger planets would naturally block out more light as they pass in front of their star,” said Robert Wells, a graduate student at Queen’s University Belfast and the paper’s lead author. “However the more important factor is actually how close the planet is to its parent star. Since the terrestrial planets are much closer to the sun than the gas giants, they’ll be more likely to be seen in transit.”

    To determine which exoplanets would have the best chance of observing our solar system, the researchers determined which parts of the sky would be able to see more than one planet’s transit in front of the Sun. As Wells and his colleagues discovered, at most three of the four terrestrial planets could be observed in transit from any point outside of our solar system.

    The image depicts where in our galaxy an observer would be able to see planetary transits in our solar system (the blue line represents Earth’s transit). The points where these lines converge are our best bets for being seen. Image: Robert Wells/Queen’s University Belfast

    Statistically speaking, this means that a randomly placed alien outside the solar system has a 1 in 40 chance of observing a single terrestrial planet in our solar system. “The probability of detecting two planets would be about ten times lower, and to detect three would be a further ten times smaller than this,” said Katja Poppenhaeger, an astrophysicist at Queen’s University Belfast.

    Of the 3,500 known exoplanets, the team calculated that only 68 are situated such that they could observe at least one planet in our solar system. Of these, nine are ideally situated to observe Earth, but none of these nine planets are habitable.

    All hope is not lost for cosmic voyeurism, however. The team also estimated that based on the current distribution of exoplanets, there may be dozens of yet-to-be-discovered planets in the habitable zones of their star that can also see Earth.

    The team hopes to confirm this based on data from NASA’s K2 mission, which is hunting for exoplanet transits in certain areas of the sky.

    NASA/Kepler Telescope

    Each K2 campaign, or the time the orbital telescope spends observing a certain region of the sky, lasts for around 83 days. The researchers expect K2 to discover around a dozen exoplanets that would be able to see planetary transits in our solar system during each campaign.

    With any luck, one of those exoplanets might be gazing back at us.

    The future is wonderful, the future is terrifying. We should know, we live there. Whether on the ground or on the web, Motherboard travels the world to uncover the tech and science stories that define what’s coming next for this quickly-evolving planet of ours.

    Motherboard is a multi-platform, multimedia publication, relying on longform reporting, in-depth blogging, and video and film production to ensure every story is presented in its most gripping and relatable format. Beyond that, we are dedicated to bringing our audience honest portraits of the futures we face, so you can be better informed in your decision-making today.

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    QUB campus

    An international institution

    Queen’s is in the top one per cent of global universities.

    With more than 23,000 students and 3,700 staff, it is a dynamic and diverse institution, a magnet for inward investment, a major employer and investor, a patron of the arts and a global player in areas ranging from cancer studies to sustainability, and from pharmaceuticals to creative writing.
    World-leading research

    Queen’s is a member of the Russell Group of 24 leading UK research-intensive universities, alongside Oxford, Cambridge and Imperial College London.

    In the UK top ten for research intensity

    The Research Excellence Framework (REF) 2014 results placed Queen’s joint 8th in the UK for research intensity, with over 75 per cent of Queen’s researchers undertaking world-class or internationally leading research.

    The University also has 14 subject areas ranked within the UK’s top 20 and 76 per cent of its research classified in the top two categories of world leading and internationally excellent.

    This validates Queen’s as a University with world-class researchers carrying out world-class or internationally leading research.

    Globally recognised education

    The University has won the Queen’s Anniversary Prize for Higher and Further Education on five occasions – for Northern Ireland’s Comprehensive Cancer Services programme and for world-class achievement in green chemistry, environmental research, palaeoecology and law.

    Max Planck Institute for Solar System Research

    The Max Planck Institute for Solar System Research has had an eventful history – with several moves, changes of name, and structural developments. The first prototype of the current institute was founded in 1934 in Mecklenburg; it moved to Katlenburg-Lindau in 1946. Not just the location of the buildings changed – the topic of research also moved, from Earth to outer space. In the first decades the focus of research was the stratosphere and ionosphere of the Earth, but since 1997 the institute exclusively researches the physics of planets and the Sun. In January 2014 the Max Planck Institute for Solar System Research has relocated to it’s new home: a new building in Göttingen close to the Northern Campus of the University of Göttingen.

  • richardmitnick 3:30 pm on August 18, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, Gliese 832b and Gliese 832c were discovered by the radial velocity technique, Star system Gliese 832,   

    From U Texas Arlington: “UTA astrophysicists predict Earth-like planet may exist in star system only 16 light years away” 

    U Texas Arlington

    University of Texas at Arlington

    August 17, 2017
    Louisa Kellie
    Office: 817‑272‑0864
    Cell: 817-524-8926

    Astrophysicists at the University of Texas at Arlington have predicted that an Earth-like planet may be lurking in a star system just 16 light years away.

    The team investigated the star system Gliese 832 for additional exoplanets residing between the two currently known alien worlds in this system. Their computations revealed that an additional Earth-like planet with a dynamically stable configuration may be residing at a distance ranging from 0.25 to 2.0 astronomical unit (AU) from the star.

    “According to our calculations, this hypothetical alien world would probably have a mass between 1 to 15 Earth’s masses,” said the lead author Suman Satyal, UTA physics researcher, lecturer and laboratory supervisor. The paper is co-authored by John Griffith, UTA undergraduate student and long-time UTA physics professor Zdzislaw Musielak.

    The astrophysicists published their findings this week as Dynamics of a probable Earth-Like Planet in the GJ 832 System in The Astrophysical Journal.

    UTA Physics Chair Alexander Weiss congratulated the researchers on their work, which underscores the University’s commitment to data-driven discovery within its Strategic Plan 2020: Bold Solutions | Global Impact.

    “This is an important breakthrough demonstrating the possible existence of a potential new planet orbiting a star close to our own,” Weiss said. “The fact that Dr. Satyal was able to demonstrate that the planet could maintain a stable orbit in the habitable zone of a red dwarf for more than 1 billion years is extremely impressive and demonstrates the world class capabilities of our department’s astrophysics group.”

    Gliese 832 is a red dwarf and has just under half the mass and radius of our sun. The star is orbited by a giant Jupiter-like exoplanet designated Gliese 832b and by a super-Earth planet Gliese 832c. The gas giant with 0.64 Jupiter masses is orbiting the star at a distance of 3.53 AU, while the other planet is potentially a rocky world, around five times more massive than the Earth, residing very close its host star—about 0.16 AU

    For this research, the team analyzed the simulated data with an injected Earth-mass planet on this nearby planetary system hoping to find a stable orbital configuration for the planet that may be located in a vast space between the two known planets.

    Gliese 832b and Gliese 832c were discovered by the radial velocity technique, which detects variations in the velocity of the central star, due to the changing direction of the gravitational pull from an unseen exoplanet as it orbits the star. By regularly looking at the spectrum of a star – and so, measuring its velocity – one can see if it moves periodically due to the influence of a companion.

    “We also used the integrated data from the time evolution of orbital parameters to generate the synthetic radial velocity curves of the known and the Earth-like planets in the system,” said Satyal, who earned his Ph.D. in Astrophysics from UTA in 2014. “We obtained several radial velocity curves for varying masses and distances indicating a possible new middle planet,” the astrophysicist noted.

    For instance, if the new planet is located around 1 AU from the star, it has an upper mass limit of 10 Earth masses and a generated radial velocity signal of 1.4 meters per second. A planet with about the mass of the Earth at the same location would have radial velocity signal of only 0.14 m/s, thus much smaller and hard to detect with the current technology.

    “The existence of this possible planet is supported by long-term orbital stability of the system, orbital dynamics and the synthetic radial velocity signal analysis”, Satyal said. “At the same time, a significantly large number of radial velocity observations, transit method studies, as well as direct imaging are still needed to confirm the presence of possible new planets in the Gliese 832 system.”

    In 2014, Noyola, Satyal and Musielak published findings related to radio emissions indicating that an exomoon could be orbiting an exoplanet in The Astrophysical Journal, where they suggested that interactions between Jupiter’s magnetic field and its moon Io may be used to detect exomoons at distant exoplanetary systems.

    Zdzislaw Musielak joined the UTA physics faculty in 1998 following his doctoral program at the University of Gdansk in Poland and appointments at the University of Heidelberg in Germany; Massachusetts Institute of Technology, NASA Marshall Space Flight Center and the University of Alabama in Huntsville.

    Suman Satyal is a research assistant, laboratory supervisor and physics lecturer at UTA and his research area includes the detection of exoplanets and exomoons, and orbital stability analysis of Exoplanets in single and binary star systems. He previously worked in the National Synchrotron Light Source located at the Brookhaven National Laboratory in New York, where he measured the background in auger-photoemission coincidence spectra associated with multi-electron valence band photoemission processes.

    See the full article here .

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    U Texas Arlington Campus

    The University of Texas at Arlington is a growing research powerhouse committed to life-enhancing discovery, innovative instruction, and caring community engagement. An educational leader in the heart of the thriving North Texas region, UT Arlington nurtures minds within an environment that values excellence, ingenuity, and diversity.

    Guided by world-class faculty members, the University’s more than 48,000 students in Texas and around the world represent 120 countries and pursue more than 180 bachelor’s, master’s, and doctoral degrees in a broad range of disciplines. UT Arlington is dedicated to producing the lifelong learners and critical thinkers our region and nation demand. More than 60 percent of the University’s 190,000 alumni live in North Texas and contribute to our annual economic impact of $12.8 billion in the region.

    With a growing number of campus residents, UT Arlington has become a first-choice university for students seeking a vibrant college experience. In addition to receiving a first-rate education, our students participate in a robust slate of co-curricular activities that prepare them to become the next generation of leaders.

  • richardmitnick 1:23 pm on June 21, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, Mini-Neptunes, NASA Has Discovered Hundreds of Potential New Planets - And 10 May Be Like Earth, , , , The new Earths next door?, You'd need 400 Keplers to cover the whole sky   

    From Science Alert: “NASA Has Discovered Hundreds of Potential New Planets – And 10 May Be Like Earth” 


    Science Alert

    20 JUN 2017

    An illustration of Earth-like planets Image: NASA/JPL-Caltech/R. Hurt

    Astronomers are ecstatic.

    NASA scientists on Monday announced the discovery of 219 new objects beyond our solar system that are almost certainly planets. What’s more, 10 of these worlds may be rocky, about the size of Earth, and habitable.

    The data comes from the space agency’s long-running Kepler exoplanet-hunting mission. From March 2009 through May 2013, Kepler stared down about 145,000 sun-like stars in a tiny section of the night sky near the constellation Cygnus.

    Most of the stars in Kepler’s view were hundreds or thousands of light-years away, so there’s little chance humans will ever visit them – or at least any time soon. However, the data could tell astronomers how common Earth-like planets are, and what the chances of finding intelligent extraterrestrial life might be.

    “We have taken our telescope and we have counted up how many planets are similar to the Earth in this part of the sky,” Susan Thompson, a Kepler research scientist at the SETI Institute, said during a press conference at NASA Ames Research Center on Monday.

    SETI Institute

    “We said, ‘how many planets there are similar to Earth?’ With the data I have, I can now make that count,” she said.

    “We’re going to determine how common other planets are. Are there other places we could live in the galaxy that we don’t yet call home?”

    Added to Kepler’s previous discoveries, the 10 new Earth-like planet candidates make 49 total, Thompson said. If any of them have stable atmospheres, there’s even a chance they could harbour alien life.

    The new Earths next door?


    Scientists wouldn’t say too much about the 10 new planets, only that they appear to be roughly Earth-sized and orbit in their stars’ ‘habitable zone’ – where water is likely to be stable and liquid, not frozen or boiled away.

    That doesn’t guarantee these planets are actually habitable, though. Beyond harboring a stable atmosphere, things like plate tectonics and not being tidally locked may also be essential.

    However, Kepler researchers suspect that almost countless Earth-like planets are waiting to be found. This is because the telescope can only ‘see’ exoplanets that transit, or pass, in front of their stars.

    Planet transit. NASA/Ames

    The transit method of detecting planets that Kepler scientists use involves looking for dips in a star’s brightness, which are caused by a planet blocking out a fraction of the starlight (similar to how the Moon eclipses the Sun).

    Because most planets orbit in the same disk or plane, and that plane is rarely aligned with Earth, that means Kepler can only see a fraction of distant solar systems. (Exoplanets that are angled slightly up or down are invisible to the transit method.)

    Despite those challenges, Kepler has revealed the existence of 4,034 planet candidates, with 2,335 of those confirmed as exoplanets. And these are just the worlds in 0.25 percent of the night sky.

    “In fact, you’d need 400 Keplers to cover the whole sky,” Mario Perez, a Kepler program scientist at NASA, said during the briefing.

    The biggest number of planets appear to be a completely new class of planets, called “mini-Neptunes”, Benjamin Fulton, an astronomer at the University of Hawaii at Manoa and California Institute of Technology, said during the briefing.

    Such worlds are between the size of Earth and the gas giants of our solar system, and are likely the most numerous kind in the universe. ‘Super-Earths’, which are rocky planets that can be up to 10 times more massive than our own, are also very common.

    A popular new image I have used before. NASA/Kepler/Caltech (T. Pyle)

    “This number could have been very, very small,” Courtney Dressing, an astronomer at Caltech, said during the briefing. “I, for one, am ecstatic.”

    Kepler’s big back-up plan

    NASA Ames/W. Stenzel and JPL-Caltech/R. Hurt

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

    Kepler finished collecting its first mission’s data in May 2013. It has taken scientists years to analyse that information because it’s often difficult parse, interpret, and verify.

    Thompson said this new Kepler data analysis will be the last for this leg of the telescope’s first observations. Kepler suffered two hardware failures (and then some) that limited its ability to aim at one area of the night sky, ending its mission to look at stars that are similar to the Sun.

    But scientists’ back-up plan, called the K2 mission, kicked off in May 2014. It takes advantage of Kepler’s restricted aim and uses it to study a variety of objects in space, including supernovas, baby stars, comets, and even asteroids.

    Although K2 is just getting off the ground, other telescopes have had success in these types of endeavours. In February, for example, a different one revealed the existence of seven rocky, Earth-size planets circling a red dwarf star.

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

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

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

    Such dwarf stars are the most common in the universe and can have more angry outbursts of solar flares and coronal mass ejections than sun-like stars.

    But paradoxically, they seem to harbour the most small, rocky planets in a habitable zone in the universe – and thus may be excellent places to look for signs of alien life.

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  • richardmitnick 6:01 pm on June 5, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, HAT-P-38 b, , , WASP-67 b   

    From Hubble: “Hubble’s Tale of Two Exoplanets: Nature vs. Nurture” 

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    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Release type: American Astronomical Society Meeting

    Atmospheres of Two Hot Jupiters: Cloudy and Clear

    Astronomers once thought that the family of planets that orbit our sun were typical of what would eventually be found around other stars: a grouping of small rocky planets like Earth huddled close to their parent star, and an outer family of monstrous gaseous planets like Jupiter and Saturn.

    But ever since the discovery of the first planet around another star (or exoplanet) the universe looks a bit more complicated — if not downright capricious. There is an entire class of exoplanets called “hot Jupiters.” They formed like Jupiter did, in the frigid outer reaches of their planetary system, but then changed Zip code! They migrated inward to be so close to their star that temperatures are well over 1,000 degrees Fahrenheit.

    Astronomers would like to understand the weather on these hot Jupiters and must tease out atmospheric conditions by analyzing how starlight filters through a planet’s atmosphere. If the spectral fingerprint of water can be found, then astronomers conclude the planet must have relatively clear skies that lets them see deep into the atmosphere. If the spectrum doesn’t have any such telltale fingerprints, then the planet is bland-looking with a high cloud deck.

    Knowing the atmospheres on these distant worlds yields clues to how they formed and evolved around their parent star. In a unique experiment, astronomers aimed the Hubble Space Telescope at two “cousin” hot Jupiters that are similar in several respects. However, the researchers were surprised to learn that one planet is very cloudy, and the other has clear skies.

    The Full Story
    Ann Jenkins
    Space Telescope Science Institute, Baltimore, Maryland

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland

    Giovanni Bruno
    Space Telescope Science Institute, Baltimore, Maryland


    Is it a case of nature versus nurture when it comes to two “cousin” exoplanets? In a unique experiment, scientists used NASA’s Hubble Space Telescope to study two “hot Jupiter” exoplanets. Because these planets are virtually the same size and temperature, and orbit around nearly identical stars at the same distance, the team hypothesized that their atmospheres should be alike. What they found surprised them.

    Lead researcher Giovanni Bruno of the Space Telescope Science Institute in Baltimore, Maryland, explained, “What we’re seeing in looking at the two atmospheres is that they’re not the same. One planet—WASP-67 b—is cloudier than the other—HAT-P-38 b. We don’t see what we’re expecting, and we need to understand why we find this difference.”

    The team used Hubble’s Wide Field Camera 3 to look at the planets’ spectral fingerprints, which measure chemical composition.

    NASA/ESA Hubble WFC3

    “The effect that clouds have on the spectral signature of water allows us to measure the amount of clouds in the atmosphere,” Bruno said. “More clouds mean that the water feature is reduced.” The teams found that for WASP-67 b there are more clouds at the altitudes probed by these measurements.

    “This tells us that there had to be something in their past that is changing the way these planets look,” said Bruno.

    Today the planets whirl around their yellow dwarf stars once every 4.5 Earth days, tightly orbiting their stars closer than Mercury orbits our sun. But in the past, the planets probably migrated inward toward the star from the locations where they formed.

    Perhaps one planet formed differently than the other, under a different set of circumstances. “You can say it’s nature versus nurture,” explains co-investigator Kevin Stevenson. “Right now, they appear to have the same physical properties. So, if their measured composition is defined by their current state, then it should be the same for both planets. But that’s not the case. Instead, it looks like their formation histories could be playing an important role.”

    The clouds on these hot, Jupiter-like gas giants are nothing like those on Earth. Instead, they are probably alkali clouds, composed of molecules such as sodium sulfide and potassium chloride. The average temperature on each planet is more than 1,300 degrees Fahrenheit.

    The exoplanets are tidally locked, with the same side always facing the parent star. This means they have a very hot day-side and a cooler night-side. Instead of sporting multiple cloud bands like Jupiter does, each probably has just one broad equatorial band that slowly moves the heat around from the day-side to the night-side.

    The team is just beginning to learn what factors are important in making some exoplanets cloudy and some clear. To better understand what the planets’ pasts may have been, scientists will need future observations with Hubble and the soon-to-be-launched James Webb Space Telescope.

    The team’s results were presented on June 5 at the 230th meeting of the American Astronomical Society in Austin, Texas.

    The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

    Illustration: NASA, ESA, and Z. Levy (STScI)
    Science: NASA, ESA, and G. Bruno (STScI)

    See the full article here .

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

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  • richardmitnick 7:08 am on June 2, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, , , Nobel laureate Jack Szostak, Nobel Laureate Jack Szostak: Exoplanets Gave The Origin of Life Field a Huge Boost   

    From Many Worlds: “Nobel Laureate Jack Szostak: Exoplanets Gave The Origin of Life Field a Huge Boost” 

    NASA NExSS bloc


    Many Words icon

    Many Worlds

    Marc Kaufman

    Jack Szostak, Nobel laureate and pioneering researcher in the origin-of-life field, was the featured speaker at a workshop this week at the Earth-Life Science Institute (ELSI) in Tokyo. One goal of his Harvard lab is to answer this once seemingly impossible question: was the origin of life on Earth essentially straight-forward and “easy,” or was it enormously “hard” and consequently rare in the universe. (Nerissa Escandar)

    Sometimes tectonic shifts in scientific disciplines occur because of discoveries and advances in the field. But sometimes they occur for reasons entirely outside the field itself. Such appears to be case with origins-of-life studies.

    Nobel laureate Jack Szostak was recently in Tokyo to participate in a workshop at the Earth-Life Science Institute (ELSI) on “Reconstructing the Phenomenon of Life To Retrace the Emergence of Life.”

    The talks were technical and often cutting-edge, but the backstory that Szostak tells of why he and so many other top scientists are now in the origins of life field was especially intriguing and illuminating in terms of how science progresses.

    Those ground-shifting discoveries did not involve traditional origin-of-life questions of chemical transformations and pathways. They involved exoplanets.

    “Because of the discovery of all those exoplanets, astronomy has been transformed along with many other fields,” Szostak said after the workshop.

    “We now know there’s a large range of planetary environments out there, and that has stimulated a huge amount of interest in where else in the universe might there be life. Is it just here? We know for sure that lots of environments could support life and we also would like to know: do they?

    “This has stimulated much more laboratory-based work to try to address the origins question. What’s really important is for us to know whether the transition from chemistry to biology is easy and can happen frequently and anywhere, or are there one or many difficult steps that make life potentially very rare?”

    In other words, the explosion in exoplanet science has led directly to an invigorated scientific effort to better understand that road from a pre-biotic Earth to a biological Earth — with chemistry that allows compounds to replicate, to change, to surround themselves in cell walls, and to grow ever more complex.

    With today’s increased pace of research, Szostak said, the chances of finding some solid answers have been growing. In fact, he’s quite optimistic that an answer will ultimately be forthcoming to the question of how life began on Earth.

    “The field is making real progress in understanding the pathway from pre-biotic chemistry to the earliest life,” Szostak told. “We think this is a difficult but solvable problem.”

    And any solution would inevitably shed light on both the potential make-up and prevalence of extraterrestrial life.

    This artist’s concept depicts select planetary discoveries made to date by NASA’s Kepler space telescope. (NASA/W. Stenzel)

    NASA/Kepler Telescope

    Whether it’s ultimately solvable or not, that pathway from non-life to life would appear to be nothing if not winding and complex. And since it involves trying to understand something that happened some 4 billion years ago, the field has had its share of fits and starts.

    It is no trivial fact that probably the biggest advance in modern origin-of-life science — the renown Miller-Urey experiment that produced important-for-life amino acids out of a sparked test tube filled with gases then believed to be prevalent on early Earth — took place more than 60 years ago.

    Much has changed since then, including an understanding that the gases used by Miller and Urey most likely did not reflect the early Earth atmosphere. But no breakthrough has been so dramatic and paradigm shifting since Miller-Urey. Scientists have toiled instead in the challenging terrain of how and why a vast array of chemicals associated with life just might be the ones crucial to the enterprise.

    But what’s new, Szostak said, is that the chemicals central to the pathway are much better understood today. So, too, are the mechanisms that help turn non-living compounds into self-replicating complex compounds, the process through which protective yet fragile cell walls can be formed, and the earliest dynamics involved in the essential task of collecting energy for a self-replicating chemical system to survive.

    The simple protocells that may have enabled life to develop four billion years ago consist of only genetic material surrounded by a fatty acid membrane. This pared down version of a cell—which has not yet been completely recreated in a laboratory—is thought to have been able to grow, replicate, and evolve. (Howard Hughes Medical Institute)

    This search for a pathway is a major international undertaking; a collective effort involving many labs where obstacles to understanding the origin-of-life process are being overcome one by one.

    Here’s an example from Szostak: The early RNA replicators needed the element magnesium to do their copying. Yet magnesium destroyed the cell membranes needed to protect the RNA.

    A possible solution was to find potential acids to bond with magnesium and protect the membranes, while still allowing the element to be available for RNA chemistry. His team found that citric acid, or citrate, worked well when added to the cells. Problem solved, in the lab at least.

    The Szostak lab at Harvard University and the Howard Hughes Medical Institute has focused on creating “protocells” that are engineered by researchers yet can help explain how origin-of-life processes may have taken place on the early Earth.


    Their focus, Szostak said, is on “what happens when we have the right molecules and how do they get together to form a cell that can grow and divide.”

    It remains a work in progress, but Szostak said much has been accomplished. Protocells have been engineered with the ability to replicate, to divide, to metabolize food for energy and to form and maintain a protective membrane.

    The perhaps ultimate goal is to develop a protocell with with the potential for Darwinian evolution. Were that to be achieved, then an essentially full system would have been created.

    How did something alive emerge from a non-living world. It’s a question as old as humanity, but may in time prove to be solvable. Here blue-green algae in Morning Glory Pool, Yellowstone National Park, Wyoming.

    Just as the discovery of a menagerie of exoplanets jump-started the origin of life field, it also changed forever its way of doing business.

    No longer was the field the singular realm of chemists, but began to take in geochemists, planetary scientists, evolutionary biologists, atmospheric scientists and even astronomers (one of whom works in Szostak’s lab.)

    “A lot of labs are focused on different points in the process,” he said. “And because origins are now viewed as a process, that means you need to know how planets are formed and what happens on the planetary surface and in the atmospheres when they’re young.

    “Then there’s the question of essential volatiles (such as nitrogen, water, carbon dioxide, ammonia, hydrogen, methane and sulfur dioxide); when do they come in and are they too much or not enough.”

    These were definitely not issues of importance to Stanley Miller and Harold Urey when they sought to make building blocks of life from some common gases and an electrical charge.

    But seeing the origin of life question as a long pathway as opposed to a singular event leaves some researchers cold. With so many steps needed, and with the precisely right catalysts and purified compounds often essential to allow the next step take place, they argue that these pathways produced in a chemistry lab are unlikely to have anything to do with what actually happened on Earth.

    Szostak disagrees, strongly. “That just not true. The laws of chemistry haven’t changed since early Earth, and what we’re trying to understand is the fundamental chemistry of these compounds associated with life so we can work out plausible pathways.”

    If and when a plausible chemical pathway is established, Szostak said, it would then be time to turn the scientific process around and see if there is a possible model for the presence of the needed pathway ingredients on early Earth.

    And that involves the knowledge of geochemists, researchers expert in photochemistry and planetary scientists who have insight into what conditions were like at a particular time.

    Szostak and David Deamer, an evolutionary biologist at the University of California, Santa Cruz, at the ELSI origins workshop.

    Deamer supports the view that life on Earth may well have begun in and around hydrothermal springs on land. That’s where essential compounds could concentrate, where energy was present and organic compounds on interstellar dust could have landed, as they do today. (Nerissa Escandar)

    Given the work that Szostak, his group and others have done to understand possible pathways that lead from simple starting materials to life, the inevitable question is whether there was but one pathway or many.

    Szostak is of the school that there may well have been numerous pathways that resulted in life, although only one seems to have won out. He bases his view, in part at least, on a common experience in his lab. He and his colleagues can bang their collective heads together for what seems forever on a hard problem only to later find there was not one or two but potentially many answers to it.

    An intriguing implication of this “many pathways” hypothesis is that it would seemingly increase the possibility of life starting beyond Earth. The underlying logic of Szostak’s approach is to find how chemicals can interact to form life-like and then more complex living systems within particular environments. And those varied environments could be on early Earth or on a planet or moon far away.

    “All of this looked very, very hard at the start, trying to identify the pathways that could lead to life. And sure, there are gaps remaining in our understanding. But we’ve solved a lot of problems and the remaining big problems are a rather small number. So I’m optimistic we’ll find the way.”

    “And when we get discouraged about our progress I think, you know, life did get started here. And actually it must quite simple. We’re just not smart enough to see the answer right away.

    “But in the end it generally turns out to be simple and you wonder 20 years later, why didn’t we think of that before?”

    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 7:25 am on May 15, 2017 Permalink | Reply
    Tags: , , , , , , Exoplanets, Great News for Impatient Scientists!   

    From astrobites: “Great News for Impatient Scientists!” 

    Astrobites bloc


    May 15, 2017
    Mara Zimmerman

    Title: Orbits for the Impatient: A Bayesian Rejection Sampling Method for Quickly Fitting the Orbits of Long-Period Exoplanets
    Authors: Sarah Blunt, Eric L. Nielsen, Robert J. De Rosa, et al.
    Leading Author’s Institution: Department of Physics, Brown University, Providence, RI 02912, USA

    Status: Accepted for publication in ApJ [open access]

    Discoveries of exoplanets happen quite often these days, so much so that the discovery alone is not enough to satisfy collective scientific curiosity. Discovery with direct imaging, in particular, does not usually reveal much about the planet, other than its existence. However, unlike the transit method and radial velocity measurements, direct imaging allows us to observe exoplanets with very long periods, which is an under-sampled population in the list of currently known exoplanets. Still, this double-edged method of measurement cannot give us full orbital parameters of the planetary system. This population of exoplanets cannot be easily observed by any other method but direct imaging, so the question arises—how can we find the orbital properties of this planetary system with the measurements we have?

    The authors of this paper use a new rejection sampling method to quickly find the orbits of these exoplanets, called Orbits for the Impatient (OFTI) . This method generates random orbital fits from astrometric measurements, then scales and rotates the orbits, and then reject orbits too unlikely. A visualization of this process is shown in Figure 1.

    Figure 1: This shows a visualization of the OFTI method sampling, scaling and rotating a randomly selected orbit of the fitted exoplanet. In the lowest image, the red lines are the accepted orbits while the gray lines show the rejected orbits.

    This method uses astrometric observations and their uncertainties with prior probability density functions to produce posterior probability density functions of generated orbits. The main process of a rejection sampling method goes like this: the code generates random sets of orbital parameters, calculates a probability for each value, then rejects values with lower probabilities. The rejection process in OFTI is determined by comparing the generated probability to a selected number in (0,1). If the generated probability is greater than the random variable, then the orbit is accepted. This process repeats until any desired numbers of orbits have been selected.

    Usually, algorithms such as Metropolis-Hastings MCMC are used for orbital fitting problems. However, this method takes far less time than an MCMC approach. The OFTI trials are independent, so the fitting and rejection-sampling can be done several times without incurring a bias in fitting. Running OFTI for several successive trials gives an unbiased estimate of the orbit up to 100 times faster than traditional Metropolis-Hasting MCMC fitting.

    You may wonder how this method manages to run quickly without compromising the accuracy of its results. The answer to this musing is, of course, clever computational and statistical techniques tricks. OFTI uses vectorized arrays rather then iterative loops when possible and is specifically designed to run multiple trials in parallel. Since there is an associated error with the astrometric measurements that OFTI uses to generate orbits, it first calculates the minimum χ 2 value of all orbits tested during an initial run. Then it subtracts the minimum χ 2 value from all other generated χ 2. This way, orbits with an artificially high χ 2 are not unfairly flat-out rejected. OFTI also confines the inclination and mass based on prior measurements, then uses the maximum, minimum an standard deviation of the array to change the range of values for these parameters, which prevents the generation of obviously unlikely orbits.

    Figure 2: This shows the orbit sampling of the planet GJ 504 b around star GJ 504 A. The 100 most probable orbits are colored accordingly. The right section of the image shows the measurements made of the object in black, and the red line shows the minimum orbit.

    In this paper, the authors use this fitting method to find orbital parameters for 10 directly imaged exoplanets and other objects, including brown-dwarfs and low-mass stars. The objects have at least two measured epochs of astrometry each; however in these cases, the orbit has not yet been measured because the measurements only cover a short range of the objects’s orbit, but using OFTI they successfully solved for the orbit of all of the aforementioned sub-stellar objects. The fitting for one of these objects,GJ 504 b, the current coldest imaged exoplanet, is shown in Figure 2.

    The most obvious application of this new process is long-period exoplanets, but the authors also solve for the orbits of a variety of other systems, including trinary stars and brown dwarf systems. OFTI is also very useful in planning follow-up observations of targets. This method is incredibly useful to not only planetary scientists but also to all kinds of stellar specialists. Impatient scientists can now use this method to achieve quick and accurate results, which are, quite frankly, the best kind of results.

    See the full article here .

    Please help promote STEM in your local schools.

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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 12:48 pm on February 1, 2017 Permalink | Reply
    Tags: 51 Peg b, , , , , , Exoplanets   

    From astrobites: “Discovery of Water on 51 Peg b” 

    Astrobites bloc


    Feb 1, 2017
    Joseph Schmitt

    Title: Discovery of water at high spectral resolution in the atmosphere of 51 Peg b
    Authors: J. L. Birkby, R. J. de Kok, M. Brogi, H. Schwarz, and I. A. G. Snellen
    First Author’s Institution: Harvard-Smithsonian Center for Astrophysics
    Status: Accepted into the Astronomical Journal, open access

    51 Peg b was the first exoplanet ever discovered orbiting another main sequence star (51 Peg).

    51 Peg b.http://www.bbc.co.uk/science/space/universe/key_places/51_pegasi

    This Jupiter-sized planet, found orbiting in a 4 day orbit, revolutionized astronomy and upended our understanding of planet formation. It was discovered by measuring the star’s spectrum and seeing periodic shifts in the star’s radial velocity. This radial velocity shift was caused by the planet gravitationally pulling on the star, which indirectly proves the existence of the planet. However, even early on, it was realized that astronomers should be able to see a similar radial velocity shift in the light reflected by the planet. Critically, this method could used to determine the planet’s inclination, mass, and atmospheric composition, properties that would otherwise be near impossible to measure. First used in 2010, it has now been used on several hot Jupiters.

    The Data

    The authors used 2010 data from the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT) in Chile to observe the star 51 Peg in the near-infrared.

    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level
    ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    The observations were taken continuously for 4 hours to measure the change in radial velocity as the planet orbited the star. The biggest challenge in reducing the data to a usable form was the correction/removal of the telluric lines (contamination from seeing the Earth’s atmosphere). Several rounds of data reduction were required to remove the telluric lines, which are much stronger than the star’s spectrum.

    After obtaining a clean spectrum, the authors then searched for signs of 51 Peg b’s spectrum, a difficult task since the star’s spectrum is suspected to be about 1,000-10,000 times stronger than the planet’s spectrum. Luckily, planetary atmospheres at the observed wavelength might be thick with gases that have dense spectral line signatures, making them easier to see. However, since the planet’s spectrum was not known beforehand, a grid of atmospheric models with calculated spectra was created. Many different atmospheric models were generated using the spectra of water, carbon dioxide, and methane at several different abundances, temperatures, and pressures, and by making some additional assumptions about the structure of the atmosphere (e.g., no clouds).

    However, as mentioned before, the signal of the planet’s spectrum is very weak, and only by using all lines simultaneously can one find the right model. A technique called cross-correlation is able to tease out a weak signal from many lines. Effectively, this technique “slides” each of the planet’s modeled spectra across the star+planet’s spectrum. The specific model that has the best global fit somewhere during the “slide” is likely close to the planet’s spectrum, and the location in the star+planet’s spectrum that the “slide” gave the best fit gives you that planet’s radial velocity. This is shown in two dimensions in Figure 1 (this was done by also shifting the entire star+planet spectrum back and forth too to get an accurate systemic velocity for the star+planet). These results can then be refined to gain more precision and accuracy.

    Figure 1: Significance of cross-correlation in two dimensions. The x-axis is the star+planet’s system velocity, while the y-axis is the planet’s velocity relative velocity to the star. Whiter regions have higher significance (better fits), while darker regions have lower significance (worse fits). The dashed vertical line represents the velocity of the entire star-planet system. The top horizontal dashed line is the best fit velocity of the planet. If this were a false positive signal, one might expect a similar white region in the same spot, but at the negative of the planet velocity, due to the potential of correlated noise interacting with the model spectrum in a similar way. However, no signal is seen. The black ‘+’ represents the best-fit solution to both the system’s velocity as a whole and the planet’s velocity in particular.

    The Results

    While the grid of model atmospheres was successful in finding the planet’s velocity, it did not successfully determine much about the planet’s atmosphere. However, two important conclusions can be gleaned from the study. First, 51 Peg b has an atmosphere with an appreciable amount of water in it (about 1 part in 10,000). Models that included significant (aka, detectable amounts of) carbon dioxide and methane did not result in good fits; only models of water did. This implies that the abundance of carbon dioxide and methane are below the detection threshold. Second, 51 Peg b’s mass is finally conclusively calculated to be 0.476 times the mass of Jupiter (with 7% error bars).

    The radial velocity method has come a long way. In 1995, it was barely able to measure the radial velocity shifts of bright stars. Now it’s being used to measure the radial velocities of their extremely faint planets. This technique is difficult, yet powerful. It allows for the planet’s mass, inclination, and atmospheric composition to be measured. This could be an important tool in the future for extracting information from close-in, potentially habitable worlds orbiting the coolest stars in the Galaxy.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    What do we do?

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

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

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