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Post Info TOPIC: TRAPPIST-1


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Astronomers Confirm Orbital Details of TRAPPIST-1's Least Understood Planet

Scientists using NASA's Kepler Space Telescope identified a regular pattern in the orbits of the planets in the TRAPPIST-1 system that confirmed suspected details about the orbit of its outermost and least understood planet, TRAPPIST-1h.
TRAPPIST-1 is only eight percent the mass of our sun, making it a cooler and less luminous star. It's home to seven Earth-size planets, three of which orbit in their star's habitable zone - the range of distances from a star where liquid water could pool on the surface of a rocky planet. The system is located about 40 light-years away in the constellation of Aquarius and is estimated to be between 3 and 8 billion years old.
Scientists announced that the system has seven Earth-sized planets at a NASA press conference on Feb. 22. NASA's Spitzer Space Telescope, the TRAPPIST (Transiting Planets and Planetesimals Small Telescope) in Chile and other ground-based telescopes were used to detect and characterize the planets. But the collaboration only had an estimate for the period of TRAPPIST-1h.

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Recently discovered solar system could seed life between adjacent exoplanets

In research recently published in Astrophysical Journal Letters, Krijt and fellow UChicago scientists conclude that life forms, such as bacteria or single-cell organisms, could travel through the newly discovered TRAPPIST-1 - an unusual solar system that presents an exciting new place in the Milky Way to search for extraterrestrial life.
"Frequent material exchange between adjacent planets in the tightly packed TRAPPIST-1 system appears likely," said Krijt, the study's lead author. "If any of those materials contained life, it's possible they could inoculate another planet with life."

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Title: Updated Masses for the TRAPPIST-1 Planets
Author: Songhu Wang, Dong-Hong Wu, Thomas Barclay, Gregory P. Laughlin

The newly detected TRAPPIST-1 system, with seven low-mass, roughly Earth-sized planets transiting a nearby ultra-cool dwarf, is one of the most important exoplanet discoveries to date. The short baseline of the available discovery observations, however, means that the planetary masses (obtained through measurement of transit timing variations of the planets of the system) are not yet well constrained. The masses reported in the discovery paper were derived using a combination of photometric timing measurements obtained from the ground and from the Spitzer spacecraft, and have uncertainties ranging from 30% to nearly 100%, with the mass of the outermost, P=18.8d, planet h remaining unmeasured. Here, we present an analysis that supplements the timing measurements of the discovery paper with 73.6 days of photometry obtained by the K2 Mission. Our analysis refines the orbital parameters for all of the planets in the system. We substantially improve the upper bounds on eccentricity for inner six planets (finding e<0.02 for inner six known members of the system), and we derive masses of 0.790.27 Earth masses, 1.630.63 Earth masses, 0.330.15 Earth masses, 0.24^{+0.56}_{-0.24} Earth masses, 0.360.12 Earth masses, 0.5660.038 Earth masses, and 0.0860.084 Earth masses for planets b, c, d, e, f, g, and h, respectively.

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Title: Assessing the Habitability of the TRAPPIST-1 System Using a 3D Climate Model
Author: Eric T. Wolf

The TRAPPIST-1 system provides an extraordinary opportunity to study multiple terrestrial extrasolar planets and their atmospheres. Here we use the National Center for Atmospheric Research Community Atmosphere Model version 4 to study the possible climate and habitability of the planets in the TRAPPIST-1 system. We assume ocean-covered worlds, with atmospheres comprised of N2, CO2, and H2O, and with orbital and geophysical properties defined from observation. Model results indicate that the inner three planets (b, c, and d) presently reside interior to the inner edge of the traditional liquid water habitable zone. Thus if water ever existed on the inner planets, they would have undergone a runaway greenhouse and lost their water to space, leaving them dry today. Conversely the outer 3 planets (f, g, and h) fall beyond the maximum CO2 greenhouse outer edge of the habitable zone. Model results indicate that the outer planets cannot be warmed despite as much as 30 bar CO2 atmospheres, instead entering a snowball state. The middle planet (e) represents the best chance for a presently habitable ocean-covered world in the TRAPPIST-1 system. Planet e can maintain at least some habitable surface area with 0 - 2 bar CO2, depending on the background N2 content. Near present day Earth surface temperatures can be maintained for an ocean-covered planet e with either 1 bar N2 and 0.4 bar CO2, or a 1.3 bar pure CO2 atmosphere.

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Title: Exponential Distance Relation and Near Resonances in the Trappist-1 Planetary System
Author: Vladimir Pletser, Lorenzo Basano

We report in this paper a new exponential relation distance of planets in the newly discovered exoplanetary system of the Trappist-1 star, and we comment on near orbital mean motion resonances among the seven planets. We predict that possible smaller planets could be found inside the orbit of the innermost discovered Planet b.

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NASA's Kepler Provides Another Peek At Ultra-cool Neighbour

On Feb. 22, astronomers announced that the ultra-cool dwarf star, TRAPPIST-1, hosts a total of seven Earth-size planets that are likely rocky, a discovery made by NASA's Spitzer Space Telescope in combination with ground-based telescopes. NASA's planet-hunting Kepler space telescope also has been observing this star since December 2016. Today these additional data about TRAPPIST-1 from Kepler are available to the scientific community.
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Title: Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
Author: Michael Gillon, Amaury H. M. J. Triaud, Brice-Olivier Demory, Emmanuel Jehin, Eric Agol, Katherine M. Deck, Susan M. Lederer, Julien de Wit, Artem Burdanov, James G. Ingalls, Emeline Bolmont, Jeremy Leconte, Sean N. Raymond, Franck Selsis, Martin Turbet, Khalid Barkaoui, Adam Burgasser, Matthew R. Burleigh, Sean J. Carey, Aleksander Chaushev, Chris M. Copperwheat, Laetitia Delrez, Catarina S. Fernandes, Daniel L. Holdsworth, Enrico J. Kotze, Valerie Van Grootel, Yaseen Almleaky, Zouhair Benkhaldoun, Pierre Magain, Didier Queloz

One focus of modern astronomy is to detect temperate terrestrial exoplanets well-suited for atmospheric characterisation. A milestone was recently achieved with the detection of three Earth-sized planets transiting (i.e. passing in front of) a star just 8% the mass of the Sun 12 parsecs away. Indeed, the transiting configuration of these planets with the Jupiter-like size of their host star - named TRAPPIST-1 - makes possible in-depth studies of their atmospheric properties with current and future astronomical facilities. Here we report the results of an intensive photometric monitoring campaign of that star from the ground and with the Spitzer Space Telescope. Our observations reveal that at least seven planets with sizes and masses similar to the Earth revolve around TRAPPIST-1. The six inner planets form a near-resonant chain such that their orbital periods (1.51, 2.42, 4.04, 6.06, 9.21, 12.35 days) are near ratios of small integers. This architecture suggests that the planets formed farther from the star and migrated inward. The seven planets have equilibrium temperatures low enough to make possible liquid water on their surfaces.

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Title: Enhanced interplanetary panspermia in the TRAPPIST-1 system
Author: Manasvi Lingam, Abraham Loeb

We present a simple model for estimating the probability of interplanetary panspermia in the recently discovered system of seven planets orbiting the ultracool dwarf star TRAPPIST-1, and find that panspermia is potentially orders of magnitude more likely to occur in the TRAPPIST-1 system compared to the Earth-to-Mars case. As a consequence, we argue that the probability of abiogenesis is greatly enhanced on the TRAPPIST-1 planets compared to the Solar system. By adopting models from theoretical ecology, we show that the number of species transferred and the number of life-bearing planets is also likely to be higher, because of the increased rates of immigration. We propose observational metrics for evaluating whether life was initiated by panspermia on multiple planets in the TRAPPIST-1 system. These results are also applicable to habitable exoplanets and exomoons in other planetary systems.

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Title: Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-alpha line
Author: V.Bourrier, D.Ehrenreich, P.J.Wheatley, E.Bolmont, M.Gillon, J.de Wit, A.J.Burgasser, E.Jehin, D.Queloz, A.H.M.J.Triaud

The TRAPPIST-1 system offers the opportunity to characterize terrestrial, potentially habitable planets orbiting a nearby ultracool dwarf star. We performed a four-orbit reconnaissance with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope to study the stellar emission at Lyman-alpha, to assess the presence of hydrogen exospheres around the two inner planets, and to determine their UV irradiation. We detect the Lyman-alpha line of TRAPPIST-1, making it the coldest exoplanet host star for which this line has been measured. We reconstruct the intrinsic line profile, showing that it lacks broad wings and is much fainter than expected from the stellar X-ray emission. TRAPPIST-1 has a similar X-ray emission as Proxima Cen but a much lower Ly-alpha emission. This suggests that TRAPPIST-1 chromosphere is only moderately active compared to its transition region and corona. We estimated the atmospheric mass loss rates for all planets, and found that despite a moderate extreme UV emission the total XUV irradiation could be strong enough to strip the atmospheres of the inner planets in a few billions years. We detect marginal flux decreases at the times of TRAPPIST-1b and c transits, which might originate from stellar activity, but could also hint at the presence of extended hydrogen exospheres. Understanding the origin of these Lyman-alpha variations will be crucial in assessing the atmospheric stability and potential habitability of the TRAPPIST-1 planets.

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UC San Diego Astrophysicists Contribute to Major Planet Discovery

Physics professor Adam Burgasser and his team at UC San Diego's Center for Astrophysics and Space Sciences played a contributing role in the discovery, which was detailed in a scientific paper published today in the journal Nature.
The UC San Diego team has been studying the tiny star around which the seven Earth-sized planets orbit to determine its temperature, surface gravity (a measure of mass and radius) and elemental composition. The team also obtained measurements of radio emission of the star to determine its magnetic activity, important for assessing the habitability of its seven planets.

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