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

    From astrobites: “Great News for Impatient Scientists!” 

    Astrobites bloc

    Astrobites

    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.

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    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.

    2
    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 .

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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” 

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    Astrobites

    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
    harvard-smithsonian-center-for-astrophysics-bloc
    Status: Accepted into the Astronomical Journal, open access

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

    2
    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 CRIRES
    ESO CRIRES
    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.

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    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.

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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 2:22 pm on January 17, 2017 Permalink | Reply
    Tags: , , Exoplanets, , SF State,   

    From SF State: “SF State astronomer searches for signs of life on Wolf 1061 exoplanet” 

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    San Fransisco State University

    January 13, 2017
    Jamie Oppenheim

    1
    An artist’s rendering of an exoplanet is shown. An exoplanet is a planet that exists outside Earth’s solar system. Illustration credit: NASA/Ames/JPL-Caltech

    SF State astronomer Stephen Kane searches for signs of life in one of the extrasolar systems closest to Earth.

    Is there anybody out there? The question of whether Earthlings are alone in the universe has puzzled everyone from biologists and physicists to philosophers and filmmakers. It’s also the driving force behind San Francisco State University astronomer Stephen Kane’s research into exoplanets — planets that exist outside Earth’s solar system.

    As one of the world’s leading “planet hunters,” Kane focuses on finding “habitable zones,” areas where water could exist in a liquid state on a planet’s surface if there’s sufficient atmospheric pressure. Kane and his team, including former undergraduate student Miranda Waters, examined the habitable zone on a planetary system 14 light years away. Their findings will appear in the next issue of Astrophysical Journal in a paper titled Characterization of the Wolf 1061 Planetary System.

    “The Wolf 1061 system is important because it is so close and that gives other opportunities to do follow-up studies to see if it does indeed have life,” Kane said.

    But it’s not just Wolf 1061’s proximity to Earth that made it an attractive subject for Kane and his team. One of the three known planets in the system, a rocky planet called Wolf 1061c, is entirely within the habitable zone. With assistance from collaborators at Tennessee State University and in Geneva, Switzerland, they were able to measure the star around which the planet orbits to gain a clearer picture of whether life could exist there.

    When scientists search for planets that could sustain life, they are basically looking for a planet with nearly identical properties to Earth, Kane said. Like Earth, the planet would have to exist in a sweet spot often referred to as the “Goldilocks zone” where conditions are just right for life. Simply put, the planet can’t be too close or too far from its parent star. A planet that’s too close would be too hot. If it’s too far, it may be too cold and any water would freeze, which is what happens on Mars, Kane added.

    Conversely, when planets warm, a “runaway greenhouse effect” can occur where heat gets trapped in the atmosphere. Scientists believe this is what happened on Earth’s twin, Venus. Scientists believe Venus once had oceans, but because of its proximity to the sun the planet became so hot that all the water evaporated, according to NASA. Since water vapor is extremely effective in trapping in heat, it made the surface of the planet even hotter. The surface temperature on Venus now reaches a scalding 880 degrees Fahrenheit.

    Since Wolf 1061c is close to the inner edge of the habitable zone, meaning closer to the star, it could be that the planet has an atmosphere that’s more similar to Venus. “It’s close enough to the star where it’s looking suspiciously like a runaway greenhouse,” Kane said.

    Kane and his team also observed that unlike Earth, which experiences climatic changes such as an ice age because of slow variations in its orbit around the sun, Wolf 1061c’s orbit changes at a much faster rate, which could mean the climate there could be quite chaotic. “It could cause the frequency of the planet freezing over or heating up to be quite severe,” Kane said.

    These findings all beg the question: Is life possible on Wolf 1061c? One possibility is that the short time scales over which Wolf 1061c’s orbit changes could be enough that it could actually cool the planet off, Kane said. But fully understanding what’s happening on the planet’s surface will take more research.

    In the coming years, there will be a launch of new telescopes like the James Webb Space Telescope, the successor to the Hubble Space Telescope, Kane said, and it will be able to detect atmospheric components of the exoplanets and show what’s happening on the surface.

    See the full article here .

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    SFSU Campus

    San Francisco State University (commonly referred to as San Francisco State, SF State and SFSU) is a public comprehensive university located in San Francisco, California, United States. As part of the 23-campus California State University system, the university offers 118 different Bachelor’s degrees, 94 Master’s degrees, 5 Doctoral degrees including two Doctor of Education, a Doctor of Physical Therapy, a Ph.D in Education and Doctor of Physical Therapy Science, along with 26 teaching credentials among six academic colleges.

     
  • richardmitnick 8:26 am on January 3, 2017 Permalink | Reply
    Tags: , , , , Exoplanets, Multi-fractal temporally weighted detrended fluctuation analysis, Searching a sea of ‘noise’ to find exoplanets — using only data as a guide,   

    From Yale: “Searching a sea of ‘noise’ to find exoplanets — using only data as a guide” 

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    Yale University

    December 20, 2016

    Jim Shelton
    james.shelton@yale.edu
    203-361-8332

    1
    (Illustration by Michael S. Helfenbein)

    Yale researchers have found a data-driven way to detect distant planets and refine the search for worlds similar to Earth.

    The new approach, outlined in a study published Dec. 20 in The Astronomical Journal, relies on mathematical methods that have their foundations in physics research. Rather than trying to filter out the signal “noise” from stars around which exoplanets are orbiting, Yale scientists studied all of the signal information together to understand the intricacies within its structure.

    “It requires nothing but the data itself, which is a game changer,” said senior author John Wettlaufer, the A.M. Bateman Professor of Geophysics, Mathematics and Physics at Yale. “Moreover, it allows us to compare our findings with other, traditional approaches and improve whatever modeling assumptions they use.”

    The search for exoplanets — planets found outside our own solar system — has increased dramatically in recent years. The effort is motivated, in part, by a desire to discover Earth analogs that might also support life.

    Scientists have employed many techniques in this effort, including pulsar timing, direct imaging, and measuring the speed at which stars and galaxies move either toward or away from Earth. Yet each of these techniques, individually or in combination, presents challenges.

    Primarily, those challenges have to do with eliminating extraneous data — noise — that doesn’t match existing models of how planets are expected to behave. In this traditional interpretation of noise, searches can be hampered by data that obscures or mimics exoplanets.

    Wettlaufer and his colleagues decided to look for exoplanets in the same way they had sorted through satellite data to find complex changes in Arctic sea ice. The formal name for the approach is “multi-fractal temporally weighted detrended fluctuation analysis” (MF-TWDFA). It sifts data at all time scales and extracts the underlying processes associated with them.

    “A key idea is that events closer in time are more likely to be similar than those farther away in time,” Wettlaufer said. “In the case of exoplanets, it is the fluctuations in a star’s spectral intensity that we are dealing with.”

    The use of multi-fractals in science and mathematics was pioneered at Yale by Benoit B. Mandelbrot and Katepalli Sreenivasan. For expertise in the search for exoplanets, the researchers consulted with Yale astrophysicist Debra Fischer, who has pioneered many approaches in the field.

    The researchers confirmed the accuracy of their methodology by testing it against observations and simulation data of a known planet orbiting a star in the constellation Vulpecula, approximately 63 light years from Earth.

    Sahil Agarwal, a graduate student in the Yale Program in Applied Mathematics, is first author. Fabio Del Sordo, a joint postdoctoral fellow at Yale and in Stockholm, is co-author.

    Grants from NASA and the Swedish Research Council helped to fund the research, as did a Royal Society Wolfson Research Merit Award.

    See the full article here .

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    Yale University Campus

    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 9:46 pm on December 15, 2016 Permalink | Reply
    Tags: , , Exoplanets, Hubblecast 97,   

    From Hubble: Hubblecast 97 video 

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    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Published on Dec 15, 2016

    Since astronomers discovered that the stars in the sky are other suns, humanity has wondered if they are also orbited by planets and if those planets host alien life. Since the discovery of the first exoplanet only 25 years ago Hubble is among the many instruments trying to answer these questions. This new Hubblecast tells the story of what we know so far and what we can hope for in the future.

    More information and download options: http://www.spacetelescope.org/videos/…

    Subscribe to Hubblecast in iTunes! https://itunes.apple.com/gb/podcast/h…

    Receive future episodes on YouTube by pressing the Subscribe button above or follow us on Vimeo: https://vimeo.com/hubbleesa

    Watch more Hubblecavideo.web_category.allst episodes: http://www.spacetelescope.org/videos/…

    Credit:
    Directed by: Mathias Jäger
    Visual design and editing: Martin Kornmesser
    Written by: Calum Turner, Eleanor Spring, Mathias Jäger
    Narration: Sara Mendes da Costa
    Images: NASA, ESA/Hubble, M. Kornmesser, H. Schweiker/WIYN and NOAO/AURA/NSF, GBT/NAOJ
    Videos: NASA, ESA/Hubble
    Time-lapse videos: Martin Kornmesser
    Animations: NASA, ESA/Hubble, M. Kornmesser, L. Calçada
    Music: Johan B. Monell (www.johanmonell.com)
    Web and technical support: Mathias André and Raquel Yumi Shida
    Executive producer: Lars Lindberg Christensen

    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 12:02 pm on October 21, 2016 Permalink | Reply
    Tags: , , Exoplanets, Hot Jupiter clouds,   

    From Many Worlds- “Exoplanet Clouds: Friend and Foe” 

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    NASA NExSS

    Many Worlds

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    2016-10-21
    Marc Kaufman

    1
    An illustration representing how hot Jupiters of different temperatures and different cloud compositions might appear to a person flying over the day side of these planets on a spaceship, based on computer modeling. (NASA/JPL-Caltech/University of Arizona/V. Parmentier)

    Understanding the make-up and dynamics of atmospheric clouds is crucial to our interpretations of how weather and climate behave on Earth, and so it should come as no surprise that clouds are similarly essential to learning the nature and behavior of exoplanets.

    On many exoplanets, thick clouds and related, though different, hazes have been impediments to learning what lies in the atmospheres and on surfaces below. Current technologies simply can’t pierce many of these coverings, and scientists have struggled to find new approaches to the problem.

    One class of exoplanets that has been a focus of cloud studies has been, perhaps unexpectedly, hot Jupiters — those massive and initially most surprising gas balls that orbit very close to their suns.

    Because of their size and locations, the first exoplanets detected were hot Jupiters. But later work by astronomers, and especially the Kepler Space Telescope, has established that they are not especially common in the cosmos.

    Due to their locations close to suns, however, they have been useful targets of study as the exoplanet community moves from largely detecting new objects to trying to characterize them, to understanding their basic features. And clouds are a pathway to that characterization.

    For some time now, scientists have understood that the night sides of the tidally-locked hot Jupiters generally do have clouds, as do the transition zones between day and night. But more recently, some clouds on the super-hot day sides — where temperatures can reach 2400 degrees Fahrenheit –have been identified as well.

    Vivien Parmentier, a Sagan Fellow at the University of Arizona, Tucson, as well as planetary scientist Jonathan Fortney of the University of California at Santa Cruz have been studying those day side hot Jupiter clouds to see what they might be made of, and how and why they behave as they do.

    “Cloud composition changes with planet temperature,” said Parmentier, who used a 3D General Circulation Model (GCM) to track where clouds form in hot Jupiter atmospheres, and what impact they have on the light emitted and reflected by the planets. “The offsetting light curves tell the tale of cloud composition. It’s super interesting, because cloud composition is very hard to get otherwise.”

    The paper by Parmentier, Fortney and others was published in The Astrophysical Journal.

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    Artist’s impression of a hot Jupiter. (NASA)

    Solid observational evidence of clouds on the days sides of hot Jupiters has been collected for only a short time, and is done by measuring parent starlight being reflected off the atmosphere. Enough information has accumulated by now, Fortney said, to begin to offer theoretical explanations of the measurements being made.

    “What this suggests is that the cloud behavior is quite complex — there is no ‘uniform planet-wide cloud,’ for these tidally locked planets,” he said in an email.

    “The hot day side may sometimes lack clouds, compared to the cooler night side, where many clouds form. Energy redistribution, via winds, leads to gas that is moving into “sunset” from day to night being cloud-free, but gas going into “sunrise,” moving from night to day is full our cloud material that will evaporate when the gas warms up.

    The atmospheres are way too hot for water clouds. Instead, the cloud material detected has been iron and silicate rocks (well-known from brown dwarf atmospheres), and manganese sulfide (which has been suggested for brown dwarf as well.)

    The different elements and compounds in the clouds give hints about the appearance of the planets, and Parmentier used the GCM model to predict what these planets would look like to the human eye.

    The differences in color, said Fortney, are a function of the amount of heat coming off the planet and the stellar scattered light coming off of atmospheric gases and clouds. “Not all clouds are the same color, which is fun.”

    He also said that “this is the first in what will be a longer study to better understand the transport of cloud material around the planets.

    For this first study, we only suggest that clouds will form when the temperature is right, but we didn’t track how the cloud material moves with the flow. That is the next step for a more comprehensive and accurate model.”

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    Hot Jupiters often have cloud or haze layers in their atmospheres. This may prevent space telescopes from detecting atmospheric water that lies beneath the clouds, according to an earlier study in the Astrophysical Journal. (NASA/JPL-Caltech)

    he new insights into hot Jupiter clouds via the GCM allowed the team to draw conclusions about wind and temperature differences.

    Just before the hotter planets passed behind their stars, a blip in the planet’s optical light curve revealed a “hot spot” on the planet’s eastern side. And on cooler eclipsing planets, a blip was seen just after the planet re-emerged on the other side of the star, this time on the planet’s western side.

    The early blip on hotter worlds was interpreted as being powerful winds that were pushing the hottest, cloud-free part of the day side atmosphere to the east. Meanwhile, on cooler worlds, clouds could bunch up and reflect more light on the “colder,” western side of the planet, causing the post-eclipse blip.

    “We’re claiming that the west side of the planet’s day side is more cloudy than the east side,” Parmentier said in a JPL release.

    While the puzzling pattern has been seen before, this research was the first to study all the hot Jupiters showing this behavior.

    This led to another first. By teasing out out how clouds are distributed, which is intimately tied to the planet’s overall temperature, scientists were able to determine the compositions of the clouds — likely formed as exotic vapors condense to form minerals, chemical compounds like aluminum oxide, or even metals, like iron.

    The science team found that manganese sulfide clouds probably dominate on “cooler” hot Jupiters, while silicate clouds prevail at higher temperatures. On these planets, the silicates likely “rain out” into the planet’s interior, vanishing from the observable atmosphere.

    So while exoplanet clouds can and do mask important information about what lies below in a planet’s atmosphere, scientists are learning ways to use the information that clouds provide to push forward on that process of characterizing the vast menagerie of exoplanets being found.

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    Analysis of data from the Kepler space telescope has shown that roughly half of the dayside of the exoplanet Kepler-7b is covered by a large cloud mass. Statistical comparison of more than 1,000 atmospheric models show that these clouds are most likely made of enstatite, a common Earth mineral that is in vapor form at the extreme temperature on Kepler-7b. These models varied the altitude, condensation, particle size, and chemical composition of the clouds to find the right reflectivity and color properties to match the observed signal from the exoplanet. (NASA, edited by Jose-Luis Olivares/MIT)

    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 4:38 pm on August 1, 2016 Permalink | Reply
    Tags: , , Exoplanets, Habitability Index, , Virtual Planetary Laboratory   

    From Many Worlds: “Ranking Exoplanet Habitability” The Lost Post 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2016-03-23 [Finally!!]
    Marc Kaufman

    1
    The Virtual Planetary Lab at the University of Washington has been working to rank exoplanets (or exoplanet candidates) by how likely they are to be habitable. (Rory Barnes)

    Now that we know that there are billions and billions of planets beyond our solar system, and we even know where thousands of confirmed and candidate planets are located, where should we be looking for those planets that could in theory support extraterrestrial life, and might just possibly support it now?

    The first order answer is, of course, the habitable zone — that region around a host star that would allow orbiting planets to have liquid water on the surface at least some of the time.

    That assertion is by definition a theoretical one — at this point we have no detection of an exoplanet with liquid water orbiting a distant star — and it is actually a rather long-held view.

    For instance, this is what William Whewell, the prominent British natural philosopher-scientist-theologian (and Master of Trinity College at Cambridge) wrote in 1853:

    “The Earth is really the domestic hearth of this solar system; adjusted between the hot and fiery haze on one side, the cold and watery vapour on the other. This region is fit to be the seat of habitation; and in this region is placed the largest solid globe of our system; and on this globe, by a series of creative operations…has been established, in succession, plants, and animals, and man…The Earth alone has become a World.”

    Whewell wrongly limited his analysis to our solar system, but he was pretty much on target regarding the crude basics of a habitable zone. His was followed over the decades by other related theoretical assessments, including in more modern times Steven Dole for the Rand Corporation in 1964 and NASA’s Michael Hart in 1979. All pretty much based on an Earth-centric view of habitable zones throughout the cosmos.

    It was this approach, even in its far more sophisticated modern versions, that got some of the scientists at the University of Washington’s Virtual Planetary Laboratory thinking three years ago about how they might do better. What they wanted to do was to join the theory of the habitable (or more colloquially, the “Goldilocks zone”) with actual data now coming in from measurements of transiting exoplanets.

    Although the measurements remain pretty limited, the group was convinced that the process could come up with the beginnings of a “Habitability Index” that would rate — based on evidence-based calculations and models — which exoplanets had the best chance of being able to support life.

    “We certainly are constrained by the observations being made, but we do have some important physical measurements to work with,” said Rory Barnes, a astrophysical theorist with the VPL. “And what we’ve done is to connect the possibility of life with the fundamental observables we do have….This really hasn’t been done before.”

    2
    Of the 1,030 confirmed planets from Kepler, a dozen are less than twice the size of Earth and reside in the habitable zone of their host star. They are arranged by by size and by the type of star they orbit — from the M stars that are significantly cooler and smaller than the sun, to the K stars that are somewhat cooler and smaller than the sun, to the G stars that include the sun. The sizes of the planets are enlarged by 25 times compared to the stars. The Earth is shown for reference. (NASA Ames/JPL-CalTech/R. Hurt)

    The result was a detailed paper in the Astrophysical Journal that showed observations and modeling that can be harnessed together to come up with a list of the 10 exo-objects most likely to support life. I specifically didn’t write “exoplanets” because nine of the ten remain “candidate” planets detected by the Kepler Space Telescope as transiting objects that block out a small bit of light from the host star. But they have not yet been confirmed through other detection techniques.

    And why do the hard work of teasing out the potentially most habitable planets (objects) from the many thousands of others identified? Clearly, it’s not because the data will point to some planet/objects that have a very good chance of being habitable. The information available just won’t allow for that.

    Rather, the next-generation James Webb Space Telescope is scheduled to launch in 2018, and it will be able to measure the components of exoplanets and their atmospheres in a whole new way.But access to a telescope like the JWST is costly and the observing and analyzing is and time-consuming. And so the Virtual Planetary Laboratory’s index is designed to help fellow astronomers identify which worlds might have the best chance of hosting life, and so are worthy of all the necessary time and money.

    Is the Habitability Index that much more useful than the more traditional habitable zone assessments based on a planet’s proximity to a particular star of a particular strength? And is it more predictive than some related assessments such as the Earth Similarity Index, created by Abel Mendez at the University of Puerto Rico at Arecibo.

    Because it takes into account so much more information, it certainly seems likely that it is more predictive, especially as new and better information is added to the system. While the traditional habitable zone points to a locations, the Habitability Index identifies distinctions within a habitable zone that would make an exoplanet more or less likely to support life.

    The new index is more nuanced, producing a continuum of values that astronomers can punch into a Virtual Planetary Laboratory Web form to arrive at the single-number habitability index.

    In creating the index, the researchers factored in estimates of a planet’s rockiness, rocky planets being the more Earth-like. They also accounted for a phenomenon called “eccentricity-albedo degeneracy,” which comments on a sort of balancing act between the a planet’s albedo — the energy reflected back to space from its surface — and the circularity of its orbit, which affects how much energy it receives from its host star.

    The two counteract each other. The higher a planet’s albedo, the more light and energy are reflected off to space, leaving less at the surface to warm the world and aid possible life. But the more non-circular or eccentric a planet’s orbit, the more intense is the energy it gets when passing close to its star in its elliptic journey.

    A life-friendly energy equilibrium for a planet near the inner edge of the habitable zone — in danger of being too hot for life — Barnes said, would be a higher albedo, to cool the world by reflecting some of that heat into space. Conversely, a planet near the cool outer edge of the habitable zone would perhaps need a higher level of orbital eccentricity to provide the energy needed for life.

    These are the kinds of measurements being analyzed as well by the NASA’s Kepler Habitable Zone Working Group, a collection of scientists within the Kepler team with the task of identifying some of the most promising targets for future observation.

    Stephen Kane is leading the group, and expects to come out with an assessment this summer.

    Barnes, Meadows and Evans ranked in this way planets so far found by the Kepler Space Telescope, in its original mission as well as its “K2” follow-up mission. They found that the best candidates for habitability and life are those planets that get about 60 percent to 90 percent of the solar radiation that the Earth receives from the sun, which is in keeping with current thinking about a star’s habitable zone.

    The research is part of the ongoing work of the Virtual Planetary Laboratory to study faraway planets in the ongoing search for life, and was funded by the NASA Astrobiology Institute.

    “This innovative step allows us to move beyond the two-dimensional habitable zone concept to generate a flexible framework for prioritization that can include multiple observable characteristics and factors that affect planetary habitability,” said Meadows.

    “The power of the habitability index will grow as we learn more about exoplanets from both observations and theory.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 5:30 am on July 28, 2016 Permalink | Reply
    Tags: Biosignatures, Exoplanets, , ,   

    From Many Worlds: “Coming to Terms With Biosignatures” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    2016-07-27
    Marc Kaufman
    marc.kaufman@manyworlds.space

    1
    Exoplanets are much too far away for missions to visit and explore, so scientists are learning about them remotely. That includes the question of whether they might support life — an aspect of exoplanet science that is getting new attention. This is artist Ron Miller’s impression of an exoplanet.

    The search for life beyond our solar system has focused largely on the detection of an ever-increasing number of exoplanets, determinations of whether the planets are in a habitable zone, and what the atmospheres of those planets might look like. It is a sign of how far the field has progressed that scientists are now turning with renewed energy to the question of what might, and what might not, constitute a sign that a planet actually harbors life.

    The field of “remote biosignatures” is still in its early stages, but a NASA-sponsored workshop underway in Seattle has brought together dozens of researchers from diverse fields to dig aggressively into the science and ultimately convey its conclusions back to the exoplanet community and then to the agency.

    While a similar NASA-sponsored biosignatures workshop put together a report in 2002, much has changed since then in terms of understanding the substantial complexities and possibilities of the endeavor. There is also a new sense of urgency based on the observing capabilities of some of the space and ground telescopes scheduled to begin operations in the next decade, and the related need to know with greater specificity what to look for.

    “The astrobiology community has been thinking a lot more about what it means to be a biosignature,” said Shawn Domogal-Goldman of the Goddard Space Flight Center, one of the conveners of the meeting. Some of the reason why is to give advice to those scientists and engineers putting together space telescope missions, but some is the pressing need to maintain scientific rigor for the good of one of humankind’s greatest challenges.

    “We don’t want to spend 20 years of our lives and billions in taxpayer money working for a mission to find evidence of life, and learn too late that our colleagues don’t accept our conclusions,” he told me. “So we’re bringing them all together now so we can all learn from each other about what would be, and what would not be, a real biosignature.”

    2
    How to measure the chemical signatures in the atmosphere of a transiting exoplanet. The total light measured off-transit (B in the lower left figure) decreases during the transit, when only the light from the star is measured (A). By subtracting A from B, we get the planet counterpart, and from this the “chemical fingerprints” of the planet atmosphere can be revealed. ( NASA/JPL-Caltech)

    The 3-day workshop is bringing together some 50 scientists ranging from astronomers, astrobiologists and planetary scientists to microbiologists and specialists in photosynthesis. Organized by NASA’s Nexus for Exoplanet System Science (NExSS) — an initiative created to encourage interdisciplinary collaboration — it has been tasked with putting together a report for the larger exoplanet community and ultimately for NASA.

    The first day of the workshop featured a review of previous work on biosignatures, which initially put forward the presence of oxygen in an exoplanet atmosphere as a strong and almost certain sign that biology was at work below. This is because oxygen, which is a byproduct of much life, bonds quickly with other molecules and so would be undetectable unless it was continuously replenished.

    But as outlined by Victoria Meadows, director of the Virtual Planet Laboratory at the University of Washington, more recent research has shown large amounts of oxygen can be produced without biology under a number of (usually extreme) conditions. There has been a resulting focus on potential false positive signals regarding oxygen and other molecules.

    From another perspective, Tim Lyons, a biogeochemist from the University of California, Riverside, used the early and middle Earth as an example how easy it is to arrive at a false negative result.

    He said that current thinking is that for as long as two billion years, Earth was inhabited but the lifeforms produced little oxygen. If analyzed from afar for all those years, the result would be a complete misreading of life on Earth.

    With these kinds of false positives and negatives in mind, Meadows said that the current approach to understanding biosignatures is to look beyond a single molecule to the broader planetary and solar environment.

    “We have to look not just at single biosignatures, but at their their context on the planet. How might life have modified an environment in a potentially detectable way? And having stepped back a bit, does the biosignature make sense?”

    As one example, while oxygen alone is no longer considered a sure biosignature, oxygen in an atmosphere in the presence of methane would be convincing because of the known results of the chemical interactions of the two.

    3
    Schematic for the concept of considering all small molecules in the search for biosignature gases.
    The goal is to start with chemistry and generate a list of all small molecules and filter them for the set that is stable and volatile in temperature and pressure conditions relevant for exoEarth planetary atmospheres. In the ideal situation, this overall conceptual process would lead to a finite but comprehensive list of molecules that could be considered in the search for exoplanet biosignature gases. (S. Seager and D. Beckner)

    In part because of the false positive/false negative issues involving oxygen, some have begun a concerted effort to produce a list of additional possible biosignatures. William Bains, a member of Sara Seager’s team at the Massachusetts Institute of Technology, described the blunderbuss approach they have adopted: examining some 14,000 compounds simple (fewer than six non-hydrogen atoms) and stable enough to exist in the atmosphere of an exoplanet.

    In their Astrobiology Journal article, Seager, Bains and colleagues wrote that “To maximize our chances of recognizing biosignature gases, we promote the concept that all stable and potentially volatile molecules should initially be considered as viable biosignature gases.”

    Elaborating during the workshop, Bains asked: “Why does life produce the gases that it does? We really don’t know, so we’re bringing in everything as a possibility.” Not surprisingly, he said, “The more you search, the more you find.”

    And as for the possibility of life existing in extreme environments, Bains referred to the microbes known to live in radioactive environments, in plastic, and virtually everywhere else on Earth.

    Because the science of remote biosignatures is still in its early stages, the unknowns can seem to overwhelm the knowns, making the whole endeavor seem near impossible. After all, it’s proven extremely difficult to determine whether there was ever life on “nearby” Mars, and scientists have Martian meteorites to study and rovers sending back information about the geology, the geochemistry, the weather, the atmospheric conditions and the composition of the planet.

    By comparison, learning how to probe the atmospheres of faraway exoplanets and assess what might or might not be a biosignature will have to be done entirely with next generation space telescopes and the massive ground telescopes in development. The information in the photons they collect will tell scientists what compounds are present, whether liquid water is present on the surface, and potentially whether the surface is changing with seasons. And then the interpretation begins.

    That’s why Mary Voytek, the originator of NExSS and the head of the NASA astrobiology program, said at the workshop that the goal was to test and ultimately provide as many biosignatures as possible. She wants many molecules potentially associated with life to be identified and then studied and restudied in the same critical way that oxygen has been — embraced for the biosignature possibilities it offers, and understood for the false positives and false negatives that might mislead.

    “What we need is an arsenal,” she said, as many ways to sniff out the byproducts of exoplanet life as that daunting task demands.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 12:02 pm on June 23, 2016 Permalink | Reply
    Tags: , , Exoplanets, Qatar exoplanet survey   

    From Astronomy: “Qatar exoplanet project announces the discovery of three new exoplanets” 

    Astronomy magazine

    Astronomy Magazine

    June 23, 2016
    John Wenz

    The Qatar Exoplanet Survey announced the discovery of three new exoplanets in a paper accepted for publication at the Monthly Notices of the Royal Astronomical Society.

    The three planets are called Qatar-3b, Qatar-4b, and Qatar-5b. All three are “hot Jupiter” planets, gas giants in orbits spanning just a few Earth days around their parent stars. 3b and 5b are roughly the same mass, at 4.31 and 4.32 Jupiter masses, while 4b is about 5.85 Jupiter masses. All three are slightly larger than Jupiter as well, with 4b weighing in as the largest at 1.55 times Jupiter’s radius. 3b orbits in 2.5 days around its parent star, while 4b takes 1.8 days, and 5b takes 2.87 days. All three parent stars are roughly the size of the sun.

    The planets were discovered using the transit method, where dips in starlight give away the presence of a planet. Through the analysis, the astronomers also discovered the Qatar-5 is a metal-rich planet, meaning it comes from later, newer generations of stars that utilize heavier elements in stellar fusion alongside hydrogen-helium fusion.

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

    As the names imply, these are the third, fourth, and fifth planetary objects found by the Qatar Exoplanet Survey. All five planets discovered are hot Jupiters, which are easier to detect due to their large size and swift orbits, making transit events more common. The last planet found by the survey was in 2011. Since that time, the survey has upgraded their systems and added more telescopes.

    As the names imply, these are the third, fourth, and fifth planetary objects found by the Qatar Exoplanet Survey. All five planets discovered are hot Jupiters, which are easier to detect due to their large size and swift orbits, making transit events more common. The last planet found by the survey was in 2011. Since that time, the survey has upgraded their systems and added more telescopes.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 12:26 pm on June 22, 2016 Permalink | Reply
    Tags: , , , Exoplanets, , Where the Wild (Planet)Things Are   

    From Astrobites: Where the Wild (Planet)Things Are 

    New research shows hot Jupiters find safety in numbers. According to radial velocity data, these giant exoplanets are more commonly found around stars in open clusters.

    Source: Where the Wild (Planet)Things Are

    Title: Search for giant planets in M67 III: excess of hot Jupiters in dense open clusters
    Authors: A. Brucalassi, L. Pasquini, R. Saglia, M.T. Ruiz, P. Bonifacio, I. Leão, B.L. Canto Martins, J.R. de Medeiros, L. R. Bedin, K. Biazzo, C. Melo, C. Lovis, and S. Randich

    First Author’s Institution: Max-Planck für extraterrestrische Physik, Garching bei München, Germany

    Status: Accepted for publication in A&A Journal Letters

    If you wanted to discover a new giant exoplanet, where would you look? New research, shows that star clusters are a good place to start, at least if you want to look for giant exoplanets close to their host star.

    Hot Jupiters are a breed of exoplanets that have masses about or larger than Jupiter and orbit a star in 10 days or less (for comparison, Mercury takes 88 days to go around the Sun). When they were first discovered, they posed a problem to planet formation models as it was thought gas giants could only form far from their host star where it was cool enough for ices to form, which allows for larger planets to be made. Since then, studies have shown these planets could form far out and migrate inwards over their lifetime. This can happen through interactions with the disk in which the planet forms (known as Type II migration), or through gravitational scattering with other planets or nearby stars.

    Brucalassi and her team decided to investigate an open cluster in the Milky Way (Messier 67) to look for hot Jupiters. Over several years they used three different telescopes (the ESO 3.6m telescope, the Hobby Eberly Telescope and the TNG on La Palma of the Canary Islands) to take high-precision spectra of 88 stars, 12 of which are binary stars. This spectra could then be analyzed for small blue- and redshifts which indicate the star is moving slightly. In this case, that movement is caused by the presence of another body, the exoplanet. This method is known as the radial velocity method and is the method that was used in the first exoplanet discoveries. To make sure that each star’s own activity wasn’t affecting its spectra, the group measured the Hα line which shows how active the star’s chromosphere is. Figure 1 shows an example of the radial velocity measurements.

    1
    Figure 1: Radial velocity measurements for YBP401. The coloured dots represent the different telescopes the measurements were made at. The measurements show an exoplanet with a period of just 4.08 days.

    The group’s measurements revealed a new exoplanet around the main sequence star YBP401. They were also able to get better measurements on two stars (YBP1194 and YBP1514) with known hot Jupiters. This brought the total number of hot Jupiters to 3 out of 88 stars. Although 3 might not seem like a very big number, it is larger than the number of hot Jupiters found around field stars (stars not in clusters). For the statistical analysis, Brucalassi compares the number of exoplanets with the number of main sequence and subgiant stars, i.e. stars that are not yet at the ends of their lives. Of the 88 stars, 66 are main sequence or subgiant, and of those only 53 are not binary stars. Most radial velocity studies choose to not observe binary stars so it is important to compare numbers with that in mind. A previous study from 2012 found a hot Jupiter frequency of 1.2% ± 0.38 around field stars. Brucalassi finds 4.5+4.5-2.5% when comparing with only single stars (not including binaries) in M67. To compare with statistics from the Kepler mission, binaries are included, as Kelper also surveys binaries, and the percentage for hot Jupiters in a cluster is 5.6+5.4-2.6%. The Kepler mission finds a frequency of hot Jupiters of just ~0.4%, which is considerably lower. And this trend isn’t seen just in M67. Combining radial velocity surveys for the clusters M67, Hyades, and Praesepe, there are 6 hot Jupiters in 240 surveyed stars, whereas the study from 2012 found only 12 in survey of 836 field stars.

    It’s known that systems with more metals tend to produce more planets and the star’s mass may also have an effect on planet production. However, the clusters stars and field stars are on average the same mass, so this alone cannot account for the differneces. M67 is also at solar metallicity (i.e. it’s stars tend to have the same amount of metals as our Sun) so this can also not account for the excess of hot Jupiters. Brucalassi concludes that the high number of hot Jupiters is due to the environment. Past simulations show that stars in a crowded cluster environment will experience at least one close encounter with another star, which is all that is needed to drive a Jupiter in to a closer orbit. This new research gives further evidence to this theory, putting us one step closer to understanding how exoplanets can form.

    3
    Figure 2: An artist’s rendition of the new hot Jupiter. Click on the image for a full animated video of the M67 cluster. Courtesy of the ESO press release (#eso1621).

     
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