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  • richardmitnick 9:28 am on February 23, 2019 Permalink | Reply
    Tags: , , , , , Trappist 1 system   

    From AAS NOVA: ” A Hazy Day Around TRAPPIST-1?” 

    AASNOVA

    From AAS NOVA

    22 February 2019
    Susanna Kohler

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    Artist’s illustration of the view from one of the TRAPPIST-1 planets. A new study explores limits on the clouds and hazes in the atmospheres of the outer TRAPPIST-1 planets. [ESO/M. Kornmesser]

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


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


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


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    The multi-planet system around the star TRAPPIST-1 is an excellent target for probing exoplanet atmospheres. A new study explores whether the skies of these exoplanets are likely cloudy or clear.

    It’s All Unclear

    Much like a spherical cow, a clear hydrogen atmosphere is a simple, clean, easy-to-work-with model. And much like real-life, lumpy, leggy cows, most exoplanet atmospheres are probably more complicated than the simple model. In particular, atmospheric aerosols muddy things up. These particles come in two forms: clouds, condensations of solid or liquid particles, and hazes, solid suspended particles that result from photochemical reactions in the atmosphere.

    Atmospheric aerosols have pesky side effects for observations — like washing out spectral features, preventing us from easily learning about an exoplanet’s composition. But they also have intriguing benefits — like protecting hypothetical life on those planets’ surfaces from the high-energy radiation of their host stars. For this reason, understanding aerosol content in exoplanetary atmospheres is an important component of learning about distant worlds.

    Observing the TRAPPIST-1 Family

    Unfortunately, this is also a challenging process! We learn about atmospheres through transmission spectroscopy, in which we examine spectral lines in the light that filters through a planet’s atmosphere as it transits its host. The James Webb Space Telescope (JWST) will do a better job of making observations like these once it launches — but in the meantime, we’re learning as much as we can with Hubble.

    Recent Hubble observations of the TRAPPIST-1 family of exoplanets — a system of seven planets, many of which lie in their host’s habitable zone — revealed some muted spectral features from a few of their atmospheres; from these, we’ve tried to build an understanding of their properties. Now, a new study led by Sarah Moran (Johns Hopkins University) has used the latest TRAPPIST-1 mass constraints and some recent laboratory astrophysics results to update this picture.

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    Different models (colored lines) for four TRAPPIST-1 planet atmospheres, with varying metallicities and cloud-deck heights. The black data points show the Hubble observations. Click to enlarge. [Moran et al. 2018]

    Setting Limits

    By comparing new models to the Hubble spectra for TRAPPIST-1 planets d, e, f, and g, Moran and collaborators explore the possible clouds and hazes these four planets could host. The authors vary different components of their models independently, placing limits on the planet atmospheres’ haze scattering cross sections, their metallicities, and the heights of their possible cloud decks.

    The authors then take a unique step: they compare their results to recent laboratory astrophysics experiments studying haze formation under a range of planetary temperatures and atmospheric compositions. By comparing their model limits to the laboratory experiment results, Moran and collaborators are able to make sure that their limits are physically realistic.

    Future Answers

    So what do Moran and collaborators find? We still don’t know exactly what the atmospheres of the TRAPPIST planets look like, but the authors’ limits suggest that planets d, e, and f could have volatile-rich atmospheres that didn’t form at the same time as the planet. For TRAPPIST-1 g, we can’t yet rule out the spherical-cow picture of a clear hydrogen-rich atmosphere.

    This isn’t the end of the story though: the authors show that increased-precision observations will help break many degeneracies in their models. As soon as JWST is on the job, we can hope for more answers!

    Citation

    “Limits on Clouds and Hazes for the TRAPPIST-1 Planets,” Sarah E. Moran et al 2018 AJ 156 252.
    https://iopscience.iop.org/article/10.3847/1538-3881/aae83a/meta

    See the full article here .


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    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

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  • richardmitnick 6:21 am on August 27, 2018 Permalink | Reply
    Tags: , , , , Globular star cluster Omega Centauri, Trappist 1 system, Why This Star-Packed Region of Space Is Likely Devoid of Life   

    From GIZMODO: “Why This Star-Packed Region of Space Is Likely Devoid of Life” 

    GIZMODO bloc

    From GIZMODO

    8/10/18
    George Dvorsky

    1
    A section of the globular star cluster Omega Centauri. Image: NASA, ESA, and the Hubble SM4 ERO Team

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

    Globular clusters are among the most fascinating celestial phenomena in the galaxy, packing a hideous amount of stars into a relatively tiny region of space. Given the sheer number and variety of stars within these clusters, it seems reasonable to think they’d also be packed with life. But as new research suggests, globular clusters are likely cosmic-scale wastelands.

    Stars within the Omega Centauri globular cluster are located too close together to provide the necessary long-term conditions required to sustain life, according to new research set to be published in The Astrophysical Journal. So what appears to be an excellent candidate in the search for extraterrestrial life is instead a vast expanse of sterile space, if this conclusion is correct. The finding could very well apply to other globular clusters, too.

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    The Omega Centauri star cluster. Image: ESO

    The two authors of the new study, Stephen Kane from the University of California, Riverside, and Sarah Deveny from San Francisco State University, set about the task of estimating the number of potentially habitable exoplanets within the Omega Centauri globular cluster. This cluster, the largest in the Milky Way, is packed with some 10 million stars. It’s located about 16,000 light-years from Earth, making it a good observational target for the Hubble Space Telescope.

    NASA/ESA Hubble Telescope

    “Despite the large number of stars concentrated in Omega Centauri’s core, the prevalence of exoplanets remains somewhat unknown,” said Kane in a statement. “However, since this type of compact star cluster exists across the universe, it is an intriguing place to look for habitability.”

    Out of a selection of 470,000 stars of various types, Kane and Deveny whittled down their sample pool to about 350,000, all of which, due to their temperature and age, could allow for the presence of habitable zones, and by consequence, habitable exoplanets. The area of each star’s habitable zone—that sweet-spot orbital range within which liquid water could exist on a planet’s surface—was calculated by the researchers. Most stars in the study were small red dwarfs, resulting in habitable zones at close distances owing to the stars’ low temperatures.

    “The core of Omega Centauri could potentially be populated with a plethora of compact planetary systems that harbor habitable-zone planets close to a host star,” Kane said. “An example of such a system is TRAPPIST-1, a miniature version of our own Solar System that is 40 light-years away and is currently viewed as one of the most promising places to look for alien life.”

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

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

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

    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    But when the researchers looked at the resulting data, they came to a rather grim realization: These stars are located too close together for stable planetary systems to exist. Take Earth, for example, which is located about 4.22 light-years from our nearest neighboring star, Alpha Centauri; it’s too far away for its gravity to influence the orientation of our planets.

    Such is not the case in the Omega Centauri globular cluster, where the average distance between stars is about 0.16 light-years. At this distance, each star endures a close encounter with a neighboring star about once every million years. These encounters fundamentally alter the planetary architecture of each star system. An exoplanet once parked within the cozy confines of a habitable zone would suddenly find itself flung into the frigid outer realms of its star system, or tossed into a toasty closer orbit.

    As the example on Earth shows, life requires thousands of millions of years to evolve complexity, so with this kind of disruption, it’s highly unlikely that Omega Centauri, or any globular cluster for that matter (there are about 200 globular clusters in the Milky Way, most of them located in the galactic halo beyond the galaxy’s bright center), contains the long-term conditions required to sustain life. If life did manage to emerge, say some kind of microbe, it would likely be snuffed out within a million years or so, unable to acquire complexity and evolve into things like fish, terrestrial vertebrates, or animals with human-like intelligence.

    “The rate at which stars gravitationally interact with each other would be too high to harbor stable habitable planets,” explained Deveny. “Looking at clusters with similar or higher encounter rates to Omega Centauri’s could lead to the same conclusion. So, studying globular clusters with lower encounter rates might lead to a higher probability of finding stable habitable planets.”

    This isn’t the first study to question the habitability of globular clusters, but it does provide the first quantitative analysis of Omega Centauri and its potential for habitability. Still, other scientists have previously argued that star clusters could in fact harbor life.

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    The central portion of star cluster RCW 38. Image: ESO/K. Muzic

    Needless to say, this study carries implications for both astrobiologists and SETI (the search for extraterrestrial intelligence). Life may be rarer in the galaxy than we thought—but that doesn’t mean globular clusters aren’t attractive to star-hopping alien intelligences. For advanced space-faring civilizations, a globular cluster, with its stars in close proximity, could be an ideal place to build an array of superstructures, such as Dyson spheres. Should they venture into these star-packed regions of space, they’d better bring their sunglasses.

    See the full article here .

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  • richardmitnick 2:30 pm on May 17, 2018 Permalink | Reply
    Tags: , , , , , Trappist 1 system   

    From SETI Institute: “An Update on the Potential Habitability of TRAPPIST-1. No Aliens yet, but We’ve Learned a lot.” 

    SETI Logo new
    From SETI Institute

    April 24, 2018
    Franck Marchis, Exoplanet Research Chair, Senior Scientist

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


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


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    One year ago, I wrote an article about the remarkable discovery of the TRAPPIST-1 planetary system, a system of seven temperate terrestrial planets orbiting an ultra-cool red dwarf star. This was an enormous astronomical discovery because these low-mass stars are the most numerous ones in our galaxy, and the discovery of potentially habitable planets around one of them led many people to speculate about the existence of life there and elsewhere in our galaxy around similar stars.

    This announcement also inspired a lot of additional studies by astronomers worldwide, who have used additional instruments and run complex models to better understand this planetary system and its potential for hosting life.

    One year later, it seems to me that the time is right to give you an update on what we’ve learned about this planetary system, which is located only 41 light-years from Earth.

    Better Understanding of the Planetary System

    Between December 2016 and March 2017, additional data on TRAPPIST-1 were collected using the Kepler spacecraft in the K2 program.

    NASA/Kepler Telescope

    Kepler was designed to measure transits of exoplanets, but observations of TRAPPIST-1 were a huge challenge even for this remarkable planet-hunting spacecraft because TRAPPIST-1 is very faint in visible light.

    Planet transit. NASA/Ames

    During its lifetime, astronomers have learned a lot about Kepler’s many capabilities, including better ways to reach the sensitivity necessary to detect the signatures of TRAPPIST-1-type transits (typically 0.1% the flux of the star). The authors of an article published in May 2017 in Nature were able to constrain the orbital period of the outermost planet, TRAPPIST-1h (P=18.766 days). Their work shows that the seven planets are, as suspected, in three-body resonances in a complex chain that suggests good stability over a very long period of time.

    Keep in mind that we do not see the planets but detect only their shadow using the transit technique that gives us a good estimate of a planet’s size and its orbit. However, to truly understand the nature of a planet, we also need to determine its density, and hence its mass. In an effort to estimate mass in multiple systems, astronomers have used a technique called transit-timing variations (or TTV). This technique consists of measuring a small shift in the timing of a transit caused by gravitational interaction with the other planets in the system. Using a new algorithm and a complete set of data, including data from both TRAPPIST and K2, a team of scientists has significantly improved the density measurements of the TRAPPIST-1 planets, which range from 0.6 to 1.0 times the density of Earth, or a density measurement similar to what we see in the terrestrial planets in our solar system. If we also consider the amount of light we receive from these planets, TRAPPIST-1 e is probably the most Earth-like one in the system. A paper published in February 2018 [Astronomy and Astrophysics] also included a discussion of the interior of these planets and suggested that TRAPPIST-1 c and e have large rocky interiors and -b, -d, -f, -g should have thick atmospheres, oceans, or icy crusts.

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    Figure 2: Revised density and incident flux received by the TRAPPIST-1 planets (in red) compared to our solar system’s terrestrial planets (from Grimms et al. 2018)

    To understand a planetary system, we need accurate information about its most massive object, its star. Stellar astronomers have improved their knowledge of TRAPPIST-1’s star and now estimate its age to be between 5 and 10 billion years, which makes it older than our sun. This estimate is based on various methods, including the study of its activity, its rotation rate, and its location in the Milky Way. Its mass has also been revised to 9% the mass of our sun, which slightly affects the distance of the planet from the host star.

    While observing the TRAPPIST system, astronomers have also detected strong star- like flares (seen, for instance, toward the end of the K2 observations). UV monitoring by the Hubble Space Telescope and by XMM/Newton combined with modeling revealed that the inner planets may have lost a large amount of water, but the outermost ones probably retain most of theirs. The complexity of these outgassing models and interactions with the stellar wind, when combined with planetary masses, are key to understand the nature of TRAPPIST-1’s planets and their potential habitability.

    Dynamicists, who represent another important astronomical subdiscipline, have also taken an interest in this complex system. With seven planets surrounding a low-mass star, one can legitimately wonder about system stability. Their models show us that the system can be stable over billions of years, which is outstanding news if you want life to flourish there.

    New Experiments and Innovative Ideas

    We now have unambiguous proof of the existence of the TRAPPIST-1 planets, and we know about their orbits, their size, and their mass, but a lot still remains to be learned before we can claim that they have liquid water on their surface, and we need to know far more than that before we can conclude that these planets might be habitable, or inhabited.

    One of the key challenges to computing the surface temperature of a planet is the existence and composition of its atmosphere. The atmosphere can act like a blanket, warming up the planetary surface. Using the Hubble Space Telescope, astronomers have attempted to detect the presence of rich hydrogen-dominated atmospheres around TRAPPIST-1 planets d, e, f, and g. Multi-color transit events taken in the near-infrared have ruled out such an atmosphere for planets d, e, and f. A H2-dominated atmosphere would lead to high surface temperatures and pressures, which are incompatible with the presence of liquid water. This negative detection suggests that these planets could have an Earth-like atmosphere with a temperate surface climate, which is more good news if, like me, you’re interested in habitability.

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    Figure 3: The Hubble observations revealed that the planets do not have hydrogen-dominated atmospheres. The flatter spectrum shown in the lower illustration indicates that Hubble did not spot any traces of water or methane, which are abundant in hydrogen-rich atmosphere (Credit: NASA, ESA and Z. Levy (STScI)

    If life appeared on one TRAPPIST-1 planet at a time when it was hospitable, what are the chances that it spread throughout the entire system? Two astronomers discussed this hypothesis in a short article published in June 2017 and used a simple model for lithopanspermia (the transfer of organisms in rocks from one planet to another) to discover that the likelihood of that happening is orders of magnitude higher than for the Earth-to-Mars system. In compact TRAPPIST-1, the probability of impact is higher and the transit time between planets is shorter, which makes contamination among planets more likely. They concluded that the probably of abiogenesis (the appearance of life) is enhanced for TRAPPIST-1. Of course, this is pure speculation based on physical considerations that need to be backed up by observations, but it reinforced the importance of finding such compact mini-planetary systems elsewhere the galaxy.

    Life can exist on moons as well as planets, and a moon can be a significant contributor to the presence of life because its sheer presence can stabilize the planet’s axis of rotation and create tidal pools that may be necessary for complex molecules to form and interact. No moons have been detected around the TRAPPIST-1 planets, even though the Spitzer observations were able to detect a moon as large as Earth’s. Theoretical study shows that the inner planets (-b to -e) are unlikely to have small moons because of the proximity of their star and other planets. We are not yet able to detect the presence of a small moon circling one of the outermost planets, and will not be able to detect one without using bigger telescopes in space and on the ground.

    Induction heating is a process used on Earth to melt metal. It occurs when we change the magnetic field in a conducting medium, which then dissipates the energy through heat. Astronomers have known for a few years that M-type stars like TRAPPIST-1 have a strong magnetic field. A group of astronomers [Nature Astronomy] studied the effect of such a strong magnetic field on the interior of planets in a system tilted with respect to the magnetic field of their star. Assuming a planetary interior and composition similar to Earth, they determined that the three innermost planets (-b, -c, -d) should experience enhanced volcanic activity and outgassing, and in some extreme cases have developed a magma ocean with plate tectonics and large-scale earthquakes, comparable to Io, a satellite of Jupiter. Again, this result is extremely model-dependent since we don’t yet have a clear idea of the internal composition of those planets, which will directly affect the strength of the induction heating. However, if they are truly Earth-like in composition, they could be a hellish version of our own planet.

    Other scientists have also discussed the existence of significant plate tectonics and intense earthquakes in this system due to tidal stress introduced by planet-to-star and planet-to-planet interactions. If the activity is right, some of the TRAPPIST-1 planets could indeed be similar to Earth with the equivalent of continental plates, ocean floors, and active volcanoes, but one day we will need to take a picture to confirm this.

    What’s next?

    I have summarized some of the latest articles published over the past two years about the wonderful TRAPPIST-1 system. This list is not exhaustive and I probably missed some interesting ideas and new hypotheses about this complex system.
    But one thing is crystal-clear: My readings have left me (and a lot of other people) stoked about what we might find from additional observations with large ground-based telescopes, including an Extremely Large Telescope (like the TMT, ELT, or GMT), or the James Webb Space Telescope (JWST).

    TMT-Thirty Meter Telescope, proposed and now approved for Mauna Kea, Hawaii, USA4,207 m (13,802 ft) above sea level

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile, at an altitude 3,046 m (9,993 ft)

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

    Each of these facilities is needed to constrain our models and refine our understanding of this system. For instance, long-term monitoring of the system with these facilities will place further constraints on the presence of moons in the system. Using the accurate photometry made possible by JWST, astronomers hope to constrain planetary masses and orbits to a great accuracy, derive the composition of their atmospheres, construct crude temperature maps of all of the planets in the TRAPPIST-1 system.
    After 2020, if everything goes well with JWST and if the space telescope provides the superb data that we expect, we might have a crude map of the TRAPPIST-1 planets, similar to the rough image of Pluto made with Hubble Space Telescope and later validated by the New Horizons Spacecraft.

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    Figure 4: A comparison between images of Pluto obtained by New Horizons by direct imaging and the Hubble Space Telescope by lightcurve reconstruction. Credit: NASA; (Picture combined and labeled by S. Hariri)

    NASA/ESA Hubble Telescope

    NASA/New Horizons spacecraft

    In less than two decades, nearby planetary systems like TRAPPIST-1 will become our cosmic backyard, and if everything goes as planned with missions like TESS, PLATO, ARIEL, and JWST as well as the ELTs, we will soon learn the secrets of those exotic worlds which, I am convinced, will surprise us by their diversity, just as our own solar system has surprised us over the past two decades, surprises us today, and will surely continue to surprise us in the future.
    Clear skies,

    Franck M.

    If you want to learn more about the TRAPPIST-1 system, check out some of those articles (all available for free on ArXiV).

    Boss, Alan P., Alycia J. Weinberger, Sandra A. Keiser, Tri L. Astraatmadja, Guillem Anglada-Escude, and Ian B. Thompson. 2017. Astrometric Constraints on the Masses of Long-Period Gas Giant Planets in the TRAPPIST-1 Planetary System. The Astronomical Journal, Volume 154, Issue 3, article id. 103, 6 pp. (2017). 154. doi:10.3847/1538-3881/aa84b5.

    Bourrier, V., J. de Wit, E. Bolmont, V. Stamenkovic, P. J. Wheatley, A. J. Burgasser, L. Delrez, et al. 2017. Temporal evolution of the high-energy irradiation and water content of TRAPPIST-1 exoplanets. The Astronomical Journal, Volume 154, Issue 3, article id. 121, 17 pp. (2017). 154. doi:10.3847/1538-3881/aa859c.

    Burgasser, Adam J., and Eric E. Mamajek. 2017. On the Age of the TRAPPIST-1 System. The Astrophysical Journal, Volume 845, Issue 2, article id. 110, 10 pp. (2017). 845. doi:10.3847/1538-4357/aa7fea. de Wit, J., H. R. Wakeford, N. Lewis, L. Delrez, M. Gillon, F. Selsis, J. Leconte, et al. 2018. Atmospheric reconnaissance of the habitable-zone Earth-sized planets orbiting TRAPPIST-1. Nature Astronomy, Volume 2, p. 214-219 2: 214–219. doi:10.1038/s41550-017-0374-z.

    Grimm, S, B-O Demory, M Gillon, C Dorn, E Agol, A Burdanov, L Delrez, et al. 2018. The nature of the TRAPPIST-1 exoplanets. Astronomy & Astrophysics. doi:10.1051/0004-6361/201732233.

    Kane, Stephen R., and Stephen R. 2017. Worlds Without Moons: Exomoon Constraints for Compact Planetary Systems. The Astrophysical Journal Letters, Volume 839, Issue 2, article id. L19, 4 pp. (2017). 839. doi:10.3847/2041-8213/aa6bf2.
    Kislyakova, K. G., L. Noack, C. P. Johnstone, V. V. Zaitsev, L. Fossati, H. Lammer, M. L. Khodachenko, P. Odert, and M. Guedel. 2017. Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating. Nature Astronomy, Vol. 1, p. 878-885 (2017) 1: 878–885. doi:10.1038/s41550-017-0284-0.

    Lingam, Manasvi, and Abraham Loeb. 2017. Enhanced interplanetary panspermia in the TRAPPIST-1 system. Proceedings of the National Academy of Sciences, vol. 114, issue 26, pp.6689-6693 114: 6689–6693. doi:10.1073/pnas.1703517114.

    Luger, Rodrigo, Marko Sestovic, Ethan Kruse, Simon L. Grimm, Brice-Olivier Demory, Eric Agol, Emeline Bolmont, et al. 2017. A seven-planet resonant chain in TRAPPIST-1. Nature Astronomy, Volume 1, id. 0129 (2017). 1. doi:10.1038/s41550-017-0129.

    Tamayo, Daniel, Hanno Rein, Cristobal Petrovich, and Norman Murray. 2017. Convergent Migration Renders TRAPPIST-1 Long-lived. The Astrophysical Journal Letters, Volume 840, Issue 2, article id. L19, 6 pp. (2017). 840. doi:10.3847/2041-8213/aa70ea.

    Van Grootel, Valerie, Catarina S. Fernandes, Michaël Gillon, Emmanuel Jehin, Jean Manfroid, Richard Scuflaire, Adam J. Burgasser, et al. 2017. Stellar parameters for TRAPPIST-1. The Astrophysical Journal, Volume 853, Issue 1, article id. 30, 7 pp. (2018). 853. doi:10.3847/1538-4357/aaa023.

    Zanazzi, J. J., and Amaury Triaud. 2017. Initiation of Plate Tectonics on Exoplanets with Significant Tidal Stress. eprint arXiv:1711.09898.

    See the full article here .

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  • richardmitnick 12:00 pm on February 5, 2018 Permalink | Reply
    Tags: , , , , , ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, , Trappist 1 system   

    From Hubble: “Hubble Probes Atmospheres of Exoplanets in TRAPPIST-1 Habitable Zone” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Feb 5, 2018

    Donna Weaver
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4493
    dweaver@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    Nikole Lewis
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4820
    nlewis@stsci.edu

    1
    Featured Image: Abstract Concept of TRAPPIST-1 System.


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    Astronomers using NASA’s Hubble Space Telescope have conducted the first spectroscopic survey of the Earth-sized planets (d, e, f, and g) within the habitable zone around the nearby star TRAPPIST-1. This study is a follow-up to Hubble observations made in May 2016 of the atmospheres of the inner TRAPPIST-1 planets b and c.

    Hubble reveals that at least three of the exoplanets (d, e, and f) do not seem to contain puffy, hydrogen-rich atmospheres similar to gaseous planets such as Neptune.

    Additional observations are needed to determine the hydrogen content of the fourth planet’s (g) atmosphere. Hydrogen is a greenhouse gas, which smothers a planet orbiting close to its star, making it hot and inhospitable to life. The results, instead, favor more compact atmospheres like those of Earth, Venus, and Mars.

    By not detecting the presence of a large abundance of hydrogen in the planets’ atmospheres, Hubble is helping to pave the way for NASA’s James Webb Space Telescope, scheduled to launch in 2019. Webb will probe deeper into the planetary atmospheres, searching for heavier gases such as carbon dioxide, methane, water, and oxygen. The presence of such elements could offer hints of whether life could be present, or if the planet were habitable.

    “Hubble is doing the preliminary reconnaissance work so that astronomers using Webb know where to start,” said Nikole Lewis of the Space Telescope Science Institute (STScI) in Baltimore, Maryland, co-leader of the Hubble study. “Eliminating one possible scenario for the makeup of these atmospheres allows the Webb telescope astronomers to plan their observation programs to look for other possible scenarios for the composition of these atmospheres.”

    The planets orbit a red dwarf star that is much smaller and cooler than our Sun. The four alien worlds are members of a seven-planet system around TRAPPIST-1. All seven of the planetary orbits are closer to their host star than Mercury is to our Sun. Despite the planets’ close proximity to TRAPPIST-1, the star is so much cooler than our Sun that liquid water could exist on the planets’ surfaces.

    Two of the planets were discovered in 2016 by TRAPPIST (the Transiting Planets and Planetesimals Small Telescope) in Chile. NASA’s Spitzer Space Telescope and several ground-based telescopes uncovered five additional ones, increasing the total number to seven. The TRAPPIST-1 system is located about 40 light-years from Earth. The ground based telescopes enumerated in the ESO article on this subject are ESO’s HAWK-I instrument on the Very Large Telescope at the Paranal Observatory in Chile; the 3.8-metre UKIRT in Hawaii; the 2-metre Liverpool and 4-metre William Herschel telescopes on La Palma in the Canary Islands; and the 1-metre SAAO telescope in South Africa.

    ESO HAWK-I on the ESO VLT

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


    UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory,4,207 m (13,802 ft) above sea level

    2-metre Liverpool Telescope at La Palma in the Canary Islands, Altitude 2,363 m (7,753 ft)


    ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)

    NASA/Spitzer Infrared Telescope


    SAAO 1.9 meter Telescope, at the SAAO observation station 15Kms from the small Karoo town of Sutherland in the Northern Cape, a 4-hour drive from Cape Town.

    “No one ever would have expected to find a system like this,” said team member Hannah Wakeford of STScI. “They’ve all experienced the same stellar history because they orbit the same star. It’s a goldmine for the characterization of Earth-sized worlds.”

    The Hubble observations took advantage of the fact that the planets cross in front of their star every few days. Using the Wide Field Camera 3, astronomers made spectroscopic observations in infrared light, looking for the signature of hydrogen that would filter through a puffy, extended atmosphere, if it were present. “The planets are close enough to their host star, and they have very short orbital periods, which means there are lots of opportunities to make observations,” Lewis said.

    Although Hubble did not find evidence of hydrogen, the researchers suspect the planetary atmospheres could have contained this lightweight gaseous element when they first formed. The planets may have formed farther away from their parent star in a colder region of the gaseous protostellar disk that once encircled the infant star.

    “The system is dynamically stable now, but the planets could not have formed in this tight pack,” Lewis said. “They’re too close together now, so they must have migrated to where we see them. Their primordial atmospheres, largely composed of hydrogen, could have boiled away as they got closer to the star, and then the planets formed secondary atmospheres.”

    In contrast, the rocky planets in our solar system likely formed in the hotter, dryer region closer to the Sun. “There are no analogs in our solar system for these planets,” Wakeford said. “One of the things researchers are finding is that many of the more common exoplanets don’t have analogs in our solar system. So the Hubble observations are a unique opportunity to probe an unusual system.”

    The Hubble team plans to conduct follow-up observations in ultraviolet light to search for trace hydrogen escaping the planets’ atmospheres, produced from processes involving water or methane lower in their atmospheres.

    Astronomers will then use the Webb telescope to help them better characterize those planetary atmospheres. The exoplanets may possess a range of atmospheres, just like the terrestrial planets in our solar system.

    “One of these four could be a water world,” Wakeford said. “One could be an exo-Venus, and another could be an exo-Mars. It’s interesting because we have four planets that are at different distances from the star. So we can learn a little bit more about our own diverse solar system, because we’re learning about how the TRAPPIST star has impacted its array of planets.”

    The team’s results will appear in the Feb. 5 issue of Nature Astronomy.

    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 8:16 pm on November 22, 2017 Permalink | Reply
    Tags: , , , Can You Overwater a Planet?, , , Trappist 1 system   

    From Many Worlds: “Can You Overwater a Planet?” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    Many Worlds

    Posted on 2017-11-22 by Marc Kaufman
    By guest columnist Elizabeth Tasker

    Wherever we find water on Earth, we find life. It is a connection that extends to the most inhospitable locations, such as the acidic pools of Yellowstone, the black smokers on the ocean floor or the cracks in frozen glaciers. This intimate relationship led to the NASA maxim, “Follow the Water”, when searching for life on other planets.

    Yet it turns out you can have too much of a good thing. In the November NExSS Habitable Worlds workshop in Wyoming, researchers discussed what would happen if you over-watered a planet. The conclusions were grim.

    Despite oceans covering over 70% of our planet’s surface, the Earth is relatively water-poor, with water only making up approximately 0.1% of the Earth’s mass. This deficit is due to our location in the Solar System, which was too warm to incorporate frozen ices into the forming Earth. Instead, it is widely — though not exclusively — theorized that the Earth formed dry and water was later delivered by impacts from icy meteorites. It is a theory that two asteroid missions, NASA’s OSIRIS-REx and JAXA’s Hayabusa2, will test when they reach their destinations next year.

    NASA OSIRIS-REx Spacecraft

    JAXA/Hayabusa 2

    But not all planets orbit where they were formed. Around other stars, planets frequently show evidence of having migrated to their present orbit from a birth location elsewhere in the planetary system.

    One example are the seven planets orbiting the star, TRAPPIST-1.

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


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

    Discovered…


    ESO Belgian robotic Trappist-South National Telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    …in February this year, these Earth-sized worlds orbit in resonance, meaning that their orbital times are nearly exact integer ratios. Such a pattern is thought to occur in systems of planets that formed further away from the star and migrated inwards.

    The TRAPPIST-1 worlds currently orbit in a temperate region where the levels of radiation from the star are similar to that received by our terrestrial worlds. Three of the planets orbit in the star’s habitable zone, where a planet like the Earth is most likely to exist.

    However, if these planets were born further from the star, they may have formed with a high fraction of their mass in ices. As the planets migrated inwards to more clement orbits, this ice would have melted to produce a deep ocean. The result would be water worlds.

    With more water than the Earth, such planets are unlikely to have any exposed land. This does not initially sound like a problem; life thrives in the Earth’s seas, from photosynthesizing algae to the largest mammals on the planet. The problem occurs with the planet itself.

    The clement environment on the Earth’s surface is dependent on our atmosphere. If this envelope of gas was stripped away, the Earth’s average global temperature would be about -18°C (-0.4°F): too cold for liquid water. Instead, this envelope of gases results in a global average of 15°C (59°F).

    Exactly how much heat is trapped by our atmosphere depends on the quantity of greenhouse gases such as carbon dioxide. On geological timescales, the carbon dioxide levels can be adjusted by a geological process known as the “carbon-silicate cycle”.

    In this cycle, carbon dioxide in the air dissolves in rainwater where it splashes down on the Earth’s silicate rocks. The resulting reaction is termed weathering. Weathering forms carbonates and releases minerals from the rocks that wash into the oceans. Eventually, the carbon is released back into the air as carbon dioxide through volcanoes.

    3
    Continents are not only key for habitability because they sources of minerals and needed elements but also because they allow for plate tectonics — the movements and subsequent crackings of the planet’s crust that allow gases to escape. Those gases are needed to produce an atmosphere. (National Oceanic and Atmospheric Administration)

    The rate of weathering is sensitive to temperature, slowing when he planet is cool and increasing when the temperature rises. This allows the Earth to maintain an agreeable climate for life during small variations in our orbit due to the tug of our neighboring planets or when the sun was young and cooler. The minerals released by weathering are used by all life on Earth, in particular phosphorous which forms part of our DNA.

    However, this process requires land. And that is a commodity a water world lacks. Speaking at the Habitable Worlds workshop, Theresa Fisher, a graduate student at Arizona State University, warned against the effects of submerging your continents.

    Fisher considered the consequences of adding roughly five oceans of water to an Earth-sized planet, covering all land in a global sea. Feasible, because weathering could still occur with rock on the ocean floor, though at a much reduced efficiency. The planet might then be able to regulate carbon dioxide levels, but the large reduction in freed minerals with underwater weathering would be devastating for life.

    Despite being a key element for all life on Earth, phosphorus is not abundant on our planet. The low levels are why phosphorous is the main ingredient in fertilizer. Reduce the efficiency with which phosphorous is freed from rocks and life will plummet.

    Such a situation is a big problem for finding a habitable world, warns Steven Desch, a professor at Arizona State University. Unless life is capable of strongly influencing the composition of the atmosphere, its presence will remain impossible to detect from Earth.

    “You need to have land not to have life, but to be able to detect life,” Desch concludes.

    However, considerations of detectability become irrelevant if even more water is added to the planet. Should an Earth-sized planet have fifty oceans of water (roughly 1% of the planet’s mass), the added weight will cause high pressure ices to form on the ocean floor. A layer of thick ice would seal the planet rock away from the ocean and atmosphere, shutting down the carbon-silicate cycle. The planet would be unable to regulate its surface temperature and trapped minerals would be inaccessible for life.

    Add still more water and Cayman Unterborn, a postdoctoral fellow at Arizona State, warns that the pressure will seal the planet’s lid. The Earth’s surface is divided into plates that are in continual motion. The plates melt as they slide under one another and fresh crust is formed where the plates pull apart. When the ocean weight reaches 2% of the planet’s mass, melting is suppressed and the planet’s crust grinds to a halt.

    A stagnant lid would prevent any gases trapped in the rocks during the planet’s formation from escaping. Such “degassing” is the main source of atmosphere for a rocky planet. Without such a process, the Earth-sized deep water world could only cling to an envelop of water vapor and any gas that may have escaped before the crust sealed shut.

    Unterborn’s calculations suggest that this fate awaits the TRAPPIST-1 planets, with the outer worlds plausibly having hundreds of oceans worth of water pressing down on the planet.

    So can we prove if TRAPPIST-1 and similarly migrated worlds are drowning in a watery grave? Aki Roberge, an astrophysicist at NASA Goddard Space Flight Center, notes that exoplanets are currently seen only as “dark shadows” briefly reducing their star’s light.

    However, the next generation of telescopes such as NASA’s James Webb Space Telescope, will aim to change this with observations of planetary atmospheres.

    NASA/ESA/CSA Webb Telescope annotated

    Intertwined with the planet’s geological and biological processes, this cloak of gases may reveal if the world is living or dead.

    Elizabeth Tasker is a planetary scientist and communicator at the Japanese space agency JAXA and the Earth-Life Science Institute (ELSI) in Tokyo. She is also author of a new book about planet formation titled The Planet Factory.

    See the full article here .

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    About Many Worlds

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

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

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

    About NExSS

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

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

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

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

     
  • richardmitnick 1:35 pm on August 31, 2017 Permalink | Reply
    Tags: , , , , , Trappist 1 system   

    From Hubble: “Hubble delivers first hints of possible water content of TRAPPIST-1 planets” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    31 August 2017
    Vincent Bourrier
    Observatoire de l’Université de Genève
    Sauverny, Switzerland
    Tel: +41 22 379 24 49
    Email: vincent.bourrier@unige.ch

    Julien de Wit
    Massachusetts Institute of Technology
    Cambridge, USA
    Tel: +1 617 258 0209
    Email: jdewit@mit.edu

    Mathias Jäger
    ESA/Hubble, Public Information Officer
    Garching bei Múnchen, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    1
    An international team of astronomers used the NASA/ESA Hubble Space Telescope to estimate whether there might be water on the seven earth-sized planets orbiting the nearby dwarf star TRAPPIST-1. The results suggest that the outer planets of the system might still harbour substantial amounts of water. This includes the three planets within the habitable zone of the star, lending further weight to the possibility that they may indeed be habitable.

    2
    Trappist-1 System

    3
    Comparison between the Sun and the ultracool dwarf star TRAPPIST-1

    On 22 February 2017 astronomers announced the discovery of seven Earth-sized planets orbiting the ultracool dwarf star TRAPPIST-1, 40 light-years away [1]. This makes TRAPPIST-1 the planetary system with the largest number of Earth-sized planets discovered so far.

    Following up on the discovery, an international team of scientists led by the Swiss astronomer Vincent Bourrier from the Observatoire de l’Université de Genève, used the Space Telescope Imaging Spectrograph (STIS) on the NASA/ESA Hubble Space Telescope to study the amount of ultraviolet radiation received by the individual planets of the system. “Ultraviolet radiation is an important factor in the atmospheric evolution of planets,” explains Bourrier. “As in our own atmosphere, where ultraviolet sunlight breaks molecules apart, ultraviolet starlight can break water vapour in the atmospheres of exoplanets into hydrogen and oxygen.”

    While lower-energy ultraviolet radiation breaks up water molecules — a process called photodissociation — ultraviolet rays with more energy (XUV radiation) and X-rays heat the upper atmosphere of a planet, which allows the products of photodissociation, hydrogen and oxygen, to escape.

    As it is very light, hydrogen gas can escape the exoplanets’ atmospheres and be detected around the exoplanets with Hubble, acting as a possible indicator of atmospheric water vapour [2]. The observed amount of ultraviolet radiation emitted by TRAPPIST-1 indeed suggests that the planets could have lost gigantic amounts of water over the course of their history.

    This is especially true for the innermost two planets of the system, TRAPPIST-1b and TRAPPIST-1c, which receive the largest amount of ultraviolet energy. “Our results indicate that atmospheric escape may play an important role in the evolution of these planets,” summarises Julien de Wit, from MIT, USA, co-author of the study.

    The inner planets could have lost more than 20 Earth-oceans-worth of water during the last eight billion years. However, the outer planets of the system — including the planets e, f and g which are in the habitable zone — should have lost much less water, suggesting that they could have retained some on their surfaces [3]. The calculated water loss rates as well as geophysical water release rates also favour the idea that the outermost, more massive planets retain their water. However, with the currently available data and telescopes no final conclusion can be drawn on the water content of the planets orbiting TRAPPIST-1.

    “While our results suggest that the outer planets are the best candidates to search for water with the upcoming James Webb Space Telescope, they also highlight the need for theoretical studies and complementary observations at all wavelengths to determine the nature of the TRAPPIST-1 planets and their potential habitability,” concludes Bourrier.

    Science paper:
    TEMPORAL EVOLUTION OF THE HIGH-ENERGY IRRADIATION AND WATER CONTENT OF TRAPPIST-1 EXOPLANETS

    See the full article here .

    Please help promote STEM in your local schools.

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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 3:59 pm on August 15, 2017 Permalink | Reply
    Tags: , , , , , Trappist 1 system   

    From Centauri Dreams: “TRAPPIST-1: The Importance of Age” 

    Centauri Dreams

    If life can arise around red dwarf stars, you would think TRAPPIST-1 would be the place to look. Home to seven planets, this ultracool M8V dwarf star about 40 light years away in Aquarius has been around for a long time. The age range in a new study on the matter goes from 5.4 billion years up to almost ten billion years. And we have more than one habitable zone planet to look at.

    Adam Burgasser (UC-San Diego) and Eric Mamajek (JPL) are behind the age calculations, which appear in a paper that has been accepted at The Astrophysical Journal. We have no idea how long it takes life to emerge, having only one example to work with, but it’s encouraging that we find evidence for it very early in Earth’s history, dating back some 3.8 billion years. But we also have much to learn about habitability around red dwarfs in general.

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

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

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

    The good thing about being a somewhat older red dwarf is that flare activity should have slowed over time, a fact that the authors confirm. This doesn’t make it necessarily benign. In fact, as the paper points out, “…despite TRAPPIST-1’s modest emission as compared to other late-M dwarfs, the radiation and particle environment is still extreme as compared to the Earth.”

    Centauri Dreams


    See the full article here .

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    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 8:27 am on July 13, 2017 Permalink | Reply
    Tags: , , , , , Trappist 1 system   

    From CfA: “More to Life Than the Habitable Zone” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    July 13, 2017
    Megan Watzke
    Harvard-Smithsonian Center for Astrophysics
    +1 617-496-7998
    mwatzke@cfa.harvard.edu

    Peter Edmonds
    Harvard-Smithsonian Center for Astrophysics
    +1 617-571-7279
    pedmonds@cfa.harvard.edu

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

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

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

    Two separate teams of scientists have identified major challenges for the development of life in what has recently become one of the most famous exoplanet systems, TRAPPIST-1.

    The teams, both led by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., say the behavior of the star in the TRAPPIST-1 system makes it much less likely than generally thought, that planets there could support life.

    The TRAPPIST-1 star, a red dwarf, is much fainter and less massive than the Sun. It is rapidly spinning and generates energetic flares of ultraviolet (UV) radiation.

    The first team, a pair of CfA theorists, considered many factors that could affect conditions on the surfaces of planets orbiting red dwarfs. For the TRAPPIST-1 system they looked at how temperature could have an impact on ecology and evolution, plus whether ultraviolet radiation from the central star might erode atmospheres around the seven planets surrounding it. These planets are all much closer to the star than the Earth is to the Sun, and three of them are located well within the habitable zone.

    “The concept of a habitable zone is based on planets being in orbits where liquid water could exist,” said Manasvi Lingam, a Harvard researcher who led the study. “This is only one factor, however, in determining whether a planet is hospitable for life.”

    Lingam and his co-author, Harvard professor Avi Loeb, found that planets in the TRAPPIST-1 system would be barraged by UV radiation with an intensity far greater than experienced by Earth.

    “Because of the onslaught by the star’s radiation, our results suggest the atmosphere on planets in the TRAPPIST-1 system would largely be destroyed,” said Loeb. “This would hurt the chances of life forming or persisting.”

    Lingam and Loeb estimate that the chance of complex life existing on any of the three TRAPPIST-1 planets in the habitable zone is less than 1% of that for life existing on Earth.

    In a separate study, another research team from the CfA and the University of Massachusetts in Lowell found that the star in TRAPPIST-1 poses another threat to life on planets surrounding it. Like the Sun, the red dwarf in TRAPPIST-1 is sending a stream of particles outwards into space. However, the pressure applied by the wind from TRAPPIST-1’s star on its planets is 1,000 to 100,000 times greater than what the solar wind exerts on the Earth.

    The authors argue that the star’s magnetic field will connect to the magnetic fields of any planets in orbit around it, allowing particles from the star’s wind to directly flow onto the planet’s atmosphere. If this flow of particles is strong enough, it could strip the planet’s atmosphere and perhaps evaporate it entirely.

    “The Earth’s magnetic field acts like a shield against the potentially damaging effects of the solar wind,” said Cecilia Garraffo of the CfA, who led the new study. “If Earth were much closer to the Sun and subjected to the onslaught of particles like the TRAPPIST-1 star delivers, our planetary shield would fail pretty quickly.”

    While these two studies suggest that the likelihood of life may be lower than previously thought, it does not mean the TRAPPIST-1 system or others with red dwarf stars are devoid of life.

    “We’re definitely not saying people should give up searching for life around red dwarf stars,” said Garraffo’s co-author Jeremy Drake, also from CfA. “But our work and the work of our colleagues shows we should also target as many stars as possible that are more like the Sun.”

    The paper by Lingam and Loeb was published in the International Journal of Astrobiology and is available online. The paper by Garraffo et al, also available online, has been published by The Astrophysical Journal Letters.

    See the full article here .

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    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 3:40 pm on June 30, 2017 Permalink | Reply
    Tags: , , , , , , , Cosmic Modesty’ in a Fecund Universe, , , Trappist 1 system   

    From Centauri Dreams: “‘Cosmic Modesty’ in a Fecund Universe” 

    Centauri Dreams

    8

    June 30, 2017
    Paul Gilster

    I came across the work of Chin-Fei Lee (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan) when I had just read Avi Loeb’s essay Cosmic Modesty. Loeb (Harvard University) is a well known astronomer, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics and a key player in Breakthrough Starshot.

    Breakthrough Starshot Initiative

    Breakthrough Starshot

    ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    SPACEOBS, the San Pedro de Atacama Celestial Explorations Observatory is located at 2450m above sea level, north of the Atacama Desert, in Chile, near to the village of San Pedro de Atacama and close to the border with Bolivia and Argentina

    SNO Sierra Nevada Observatory is a high elevation observatory 2900m above the sea level located in the Sierra Nevada mountain range in Granada Spain and operated maintained and supplied by IAC

    Teide Observatory in Tenerife Spain, home of two 40 cm LCO telescopes

    Observatori Astronòmic del Montsec (OAdM), located in the town of Sant Esteve de la Sarga (Pallars Jussà), 1,570 meters on the sea level

    Bayfordbury Observatory,approximately 6 miles from the main campus of the University of Hertfordshire

    [And, don’t forget Breakthrough Listen

    Breakthrough Listen Project

    1

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA



    GBO radio telescope, Green Bank, West Virginia, USA


    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    His ‘cosmic modesty’ implies we should accept the idea that humans are not intrinsically special. Indeed, given that the only planet we know that hosts life has both intelligent and primitive lifeforms on it, we should search widely, and not just around stars like our Sun.

    More on that in a moment, because I want to intertwine Loeb’s thoughts with recent work by Chin-Fei Lee, whose team has used the Atacama Large Millimeter/submillimeter Array (ALMA) to detect organic molecules in an accretion disk around a young protostar. The star in question is Herbig-Haro (HH) 212, an infant system (about 40,000 years old) in Orion about 1300 light years away. Seen nearly edge-on from our perspective on Earth, the star’s accretion disk is feeding a bipolar jet. This team’s results, to my mind, remind us why cosmic modesty seems like a viable course, while highlighting the magnitude of the question.

    What Lee’s team has found at HH 212 is an atmosphere of complex organic molecules associated with the disk. Methanol (CH3OH) is involved, as is deuterated methanol (CH2DOH), methanethiol (CH3SH), and formamide (NH2CHO), which the researchers see as precursors for producing biomolecules like amino acids and sugars. “They are likely formed on icy grains in the disk and then released into the gas phase because of heating from stellar radiation or some other means, such as shocks,” says co-author Zhi-Yun Li of the University of Virginia.

    1
    Image: Jet, disk, and disk atmosphere in the HH 212 protostellar system. (a) A composite image for the HH 212 jet in different molecules, combining the images from the Very Large Telescope (McCaughrean et al. 2002) and ALMA (Lee et al. 2015).

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

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    Orange image shows the dusty envelope+disk mapped with ALMA. (b) A zoom-in to the central dusty disk. The asterisk marks the position of the protostar. A size scale of our solar system is shown in the lower right corner for comparison. (c) Atmosphere of the accretion disk detected with ALMA. In the disk atmosphere, green is for deuterated methanol, blue for methanethiol, and red for formamide. Credit: ALMA (ESO/NAOJ/NRAO)/Lee et al.

    Every time I read about finds like this, I think about the apparent ubiquity of life’s materials — here we’re seeing organics at the earliest phases of a stellar system’s evolution. The inescapable conclusion is that the building blocks of living things are available from the outset to be incorporated in the planets that emerge from the disk. That certainly doesn’t count as a detection of life, but it does remind us of how frequently the ingredients of life manage to appear.

    In that context, Avi Loeb’s thoughts on cosmic modesty ring true. We’ve been able to extract some statistical conclusions from the Kepler instrument’s deep stare that let us infer there are more Earth-mass planets in the habitable zones of their stars in the observable universe than there are grains of sand on all the Earth’s beaches. Something to think about as you read this on your beach vacation and gaze from the sand beneath your feet to the ocean beyond.

    But are most living planets likely to occur around G-class stars like our Sun? Loeb reminds us that red dwarf stars like Proxima Centauri b and TRAPPIST-1, both of which made headlines in the past year because of their conceivably habitable planets, are long-lived, with lifetimes as long as 10 trillion years. Our Sun’s life, by comparison, is a paltry 10 billion years. Long after the Sun has turned into a white dwarf after its red giant phase, living things could still have a habitat around Proxima Centauri and TRAPPIST-1. Says Loeb:

    “I therefore advise my wealthy friends to buy real estate on Proxima b, because its value will likely go up dramatically in the future. But this also raises an important scientific question: “Is life most likely to emerge at the present cosmic time near a star like the sun?” By surveying the habitability of the universe throughout cosmic history from the birth of the first stars 30 million years after the big bang to the death of the last stars in 10 trillion years, one reaches the conclusion that unless habitability around low-mass stars is suppressed, life is most likely to exist near red dwarf stars like Proxima Centauri or TRAPPIST-1 trillions of years from now.”

    ESO Pale Red Dot project

    ESO Red Dots Campaign

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

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

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

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

    But of course, one of the reasons for missions like TESS (Transiting Exoplanet Survey Satellite),

    NASA/TESS

    is to begin to understand the small rocky worlds around nearby red dwarfs, and to determine whether there are factors like tidal lock or stellar flaring that preclude life there. For that matter, do the planets around Proxima and TRAPPIST-1 have atmospheres? There too the answer will be forthcoming, assuming the James Webb Space Telescope is deployed successfully and can make the needed assessment of these worlds.

    NASA/ESA/CSA Webb Telescope annotated

    ” …very advanced civilizations [Loeb continues] could potentially be detectable out to the edge of the observable universe through their most powerful beacons. The evidence for an alien civilization might not be in the traditional form of radio communication signals. Rather, it could involve detecting artifacts on planets via the spectral edge from solar cells, industrial pollution of atmospheres, artificial lights or bursts of radiation from artificial beams sweeping across the sky.”

    Changes to the traditional view of SETI abound as we explore these new pathways. In any case, our technologies for making such detections have never been as advanced, and work across the exoplanetary spectrum, such as the findings of Chin-Fei Lee and colleagues, urges us on as we try to relate our own civilization to a universe in which it is hardly the center. As Loeb reminds us, we are orbiting a galaxy that itself moves at ~0.001c relative to the cosmic rest frame, one of perhaps 100 billion galaxies in the observable universe.

    Either alternative — we are alone, or we are not — changes everything about our perspective, and encourages us to deepen the search for simple life (perhaps detected in exoplanetary atmospheres through its biosignatures) as well as conceivable alien civilizations. Embracing Loeb’s cosmic modesty, we press on under the assumption that life’s emergence is not uncommon, and that refining the search to learn the answer is a civilizational imperative.

    See the full article here .

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    Tracking Research into Deep Space Exploration

    Alpha Centauri and other nearby stars seem impossible destinations not just for manned missions but even for robotic probes like Cassini or Galileo. Nonetheless, serious work on propulsion, communications, long-life electronics and spacecraft autonomy continues at NASA, ESA and many other venues, some in academia, some in private industry. The goal of reaching the stars is a distant one and the work remains low-key, but fascinating ideas continue to emerge. This site will track current research. I’ll also throw in the occasional musing about the literary and cultural implications of interstellar flight. Ultimately, the challenge may be as much philosophical as technological: to reassert the value of the long haul in a time of jittery short-term thinking.

     
  • richardmitnick 4:15 pm on June 29, 2017 Permalink | Reply
    Tags: , , , , The Case for Cosmic Modesty, Trappist 1 system   

    From SA: “The Case for Cosmic Modesty” 

    Scientific American

    Scientific American

    June 28, 2017
    Abraham Loeb

    1
    The Parkes radio telescope in Australia has been used to search for extraterrestrial intelligence. Credit: Ian Sutton Flickr (CC BY-SA 3.0)

    “There are many reasons to be modest,” my mother used to say when I was a kid. But after three decades as an astronomer, I can add one more reason: the richness of the universe around us.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Prior to the development of modern astronomy, humans tended to think the physical world centered on us. The sun and the stars were thought to revolve around Earth. Although naive in retrospect, this is a natural starting point. When my daughters were infants, they tended to think the world centered on them. Their development portrayed an accelerated miniature of human history. As they grew up, they matured and acquired a more balanced perspective.

    Similarly, observing the sky makes us aware of the big picture and teaches us modesty. We now know we are not at the center of the physical universe, because Earth orbits the sun, which circles around the center of the Milky Way Galaxy, which itself drifts with a peculiar velocity of ~0.001c (c is the speed of light) relative to the cosmic rest frame.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Many people, however, still believe we might be at the center of the biological universe; namely, that life is rare or unique to Earth. In contrast, my working hypothesis, drawn from the above example of the physical universe, is that we are not special in general, not only in terms of our physical coordinates but also as a form of life. Adopting this perspective implies we are not alone. There should be life out there in both primitive and intelligent forms. This conclusion, implied by the principle of “cosmic modesty,” has implications. If life is likely to exist elsewhere, we should search for it in all of its possible forms.

    Breakthrough Listen Project

    1

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA



    GBO radio telescope, Green Bank, West Virginia, USA

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia

    Breakthrough Starshot Initiative

    Breakthrough Starshot

    ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

    SPACEOBS, the San Pedro de Atacama Celestial Explorations Observatory is located at 2450m above sea level, north of the Atacama Desert, in Chile, near to the village of San Pedro de Atacama and close to the border with Bolivia and Argentina

    SNO Sierra Nevada Observatory is a high elevation observatory 2900m above the sea level located in the Sierra Nevada mountain range in Granada Spain and operated maintained and supplied by IAC

    Teide Observatory in Tenerife Spain, home of two 40 cm LCO telescopes

    Observatori Astronòmic del Montsec (OAdM), located in the town of Sant Esteve de la Sarga (Pallars Jussà), 1,570 meters on the sea level

    Bayfordbury Observatory,approximately 6 miles from the main campus of the University of Hertfordshire

    Our civilization has reached an important milestone. We now have access to unprecedented technologies in our search for extraterrestrial life, be it primitive or intelligent. The search for primitive life is currently underway and well funded, but the search for intelligence is out of the mainstream of federal funding agencies. This should not be the case given that the only planet known to host life, Earth, shows both primitive and intelligent life forms of it.

    Our first radio signals have leaked by now out to a distance of more than 100 light-years and we might soon hear back a response. Rather than being guided by Fermi’s paradox: “Where is everybody?” or by philosophical arguments about the rarity of intelligence, we should invest funds in building better observatories and searching for a wide variety of artificial signals in the sky. Civilizations at our technological level might produce mostly weak signals. For example, a nuclear war on the nearest planet outside the solar system would not be visible even with our largest telescopes.

    But very advanced civilizations could potentially be detectable out to the edge of the observable universe through their most powerful beacons. The evidence for an alien civilization might not be in the traditional form of radio communication signals. Rather, it could involve detecting artifacts on planets via the spectral edge from solar cells, industrial pollution of atmospheres, artificial lights or bursts of radiation from artificial beams sweeping across the sky.

    Finding the answer to the important question: “Are we alone?” will change our perspective on our place in the universe and will open new interdisciplinary fields of research, such as astrolinguistics (how to communicate with aliens), astropolitics (how to negotiate with them for information), astrosociology (how to interpret their collective behavior), astroeconomics (how to trade space-based resources) and so on. We could shortcut our own progress by learning from civilizations that benefited from a head start of billions of years.

    There is no doubt that noticing the big picture taught my young daughters modesty. Similarly, the Kepler space telescope survey of nearby stars allowed astronomers to infer there are probably more habitable Earth-mass planets in the observable volume of the universe than there are grains of sand on all beaches on Earth. Emperors or kings who boasted after conquering a piece of land on Earth resemble an ant that hugs with great pride a single grain of sand on the landscape of a huge beach.

    Just over the past year, astronomers discovered a potentially habitable planet, Proxima b, around the nearest star, Proxima Centauri as well as three potentially habitable planets out of seven around another nearby star TRAPPIST-1.

    ESO Pale Red Dot project

    ESO Red Dots Campaign

    Centauris Alpha Beta Proxima 27, February 2012. Skatebiker

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

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

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

    (And if life formed on one of the three, it was likely transferred to the others.) These dwarf stars, whose masses are 12 percent and 8 percent the sun’s mass, respectively, will live for up to 10 trillion years, about a thousand times longer than the sun. Hence, they provide excellent prospects for life in the distant future, long after the sun will die and turn into a cool white dwarf.

    I therefore advise my wealthy friends to buy real estate on Proxima b, because its value will likely go up dramatically in the future. But this also raises an important scientific question: “Is life most likely to emerge at the present cosmic time near a star like the sun?” By surveying the habitability of the universe throughout cosmic history from the birth of the first stars 30 million years after the big bang to the death of the last stars in 10 trillion years, one reaches the conclusion that unless habitability around low-mass stars is suppressed, life is most likely to exist near red dwarf stars like Proxima Centauri or TRAPPIST-1 trillions of years from now.

    The chemistry of “life as we know it” requires liquid water, but being at the right distance from the host star for achieving a comfortable temperature on the planet’s surface is not a sufficient condition for life. The planet also needs to have an atmosphere. In the absence of an external atmospheric pressure, warming by starlight would transform water ice directly into gas rather than a liquid phase.

    The warning sign can be found next door: Mars has a tenth of Earth’s mass and lost its atmosphere. Does Proxima b have an atmosphere? If so, the atmosphere and any surface ocean it sustains will moderate the temperature contrast between its permanent day and night sides. The James Webb Space Telescope, scheduled for launch in October 2018, will be able to distinguish between the temperature contrast expected if Proxima b is bare rock compared with the case where its climate is moderated by an atmosphere, possibly along with an ocean.

    A cosmic perspective about our origins would also contribute to a balanced worldview. The heavy elements that assembled to make Earth were produced in the heart of a nearby massive star that exploded. A speck of this material takes form as our body during our life but then goes back to Earth (with one exception, namely the ashes of Clyde Tombaugh, the discoverer of Pluto, which were put on the New Horizons spacecraft and are making their way back to space).

    What are we then, if not just a transient shape that a speck of material takes for a brief moment in cosmic history on the surface of one planet out of so many? Despite all of this, life is still the most precious phenomenon we treasure on Earth. It would be amazing if we find evidence for “life as we know it” on the surface of another planet, and even more remarkable if our telescopes will trace evidence for an advanced technology on an alien spacecraft roaming through interstellar space.

    References, some with links, some without links.

    Lingam, M. & Loeb, A. 2017, ApJ 837, L23-L28.

    Lingam, M. & Loeb, A. 2017, MNRAS (in the press); preprint available at https://arxiv.org/abs/1702.05500

    Lin, H., Gonzalez, G. A. & Loeb, A., 2014, ApJ 792, L7-L11.

    Loeb, A. & Turner, E. L. 2012, Astrobiology 12, 290-290.

    Guillochon, J. & Loeb, A. ApJ 811, L20-L26.

    Anglada-Escude’, G. et al. 2016, Nature 536, 437-440.

    Gillon, M. et al. 2016, Nature 542, 456-460.

    Lingam, M. & Loeb, A. 2017, PNAS (in the press); preprint available at https://arxiv.org/abs/1703.00878

    Loeb, A., Batista, R. A., & Sloan, D. 2016, JCAP 8, 40-52.

    Kreidberg, L. & Loeb, A. 2016, ApJ, 832, L12-L18.

    See the full article here .

    Please help promote STEM in your local schools.

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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

     
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