Studies of the atmospheres of hot Jupiters reveal a diversity of atmospheric composition and haze properties. Similar studies on individual smaller, temperate planets are rare owing to the inherent ...difficulty of the observations and also to the average faintness of their host stars. To investigate their ensemble atmospheric properties, we construct a sample of 28 similar planets, all of which possess equilibrium temperature within 300-500 K, have similar size (1-3 R⊕), and orbit early M dwarfs and late K dwarfs with effective temperatures within a few hundred kelvin of one another. In addition, NASA's Kepler/K2 and Spitzer missions gathered transit observations of each planet, producing a uniform transit data set in both wavelength and coarse planetary type. With the transits measured in Kepler's broad optical bandpass and Spitzer's 4.5 m wavelength bandpass, we measure the transmission spectral slope, Δz/H, for the entire sample. While this measurement is too uncertain in nearly all cases to infer the properties of any individual planet, the distribution of Δz/H among several dozen similar planets encodes a key trend. We find that the distribution of Δz/H is not well described by a single Gaussian distribution. Rather, a ratio of the Bayesian evidences between the likeliest one-component and two-component Gaussian models favors the latter by a ratio of 100:3. In the best-fit two-component Gaussian model, one Gaussian is centered around an average Δz/H = −0.1 with a standard deviation of 8.2, while a smaller but significant second population (20% 10% of all) is located at significantly higher Δz/H center values with higher uncertainty. Although the exact shape and locations of the Gaussian models are sensitive to our assumptions in mean molecular weight, we can conclude that (1) there exist two populations of small and temperate planets regarding their effective radius variations between the Kepler bandpass and Spitzer bandpass and (2) atmospheres of this kind of planets are far from uniformly flat, and a fraction of them may be particularly favorable for follow-up observations from space-based platforms like the Hubble Space Telescope and the James Webb Space Telescope.
ABSTRACT GJ 3470b is a warm Neptune-size planet transiting an M dwarf star. Like the handful of other small exoplanets for which transmission spectroscopy has been obtained, GJ 3470b exhibits a flat ...spectrum in the near- and mid-infrared. Recently, a tentative detection of Rayleigh scattering in its atmosphere has been reported. This signal manifests itself as an observed increase of the planetary radius as a function of decreasing wavelength in the visible. We set out to verify this detection and observed several transits of this planet with the LCOGT network and the Kuiper telescope in four different bands (Sloan g, Sloan i, Harris B, and Harris V). Our analysis reveals a strong Rayleigh scattering slope, thus confirming previous results. This makes GJ 3470b the smallest known exoplanet with a detection of Rayleigh scattering. We find that the most plausible scenario is a hydrogen/helium-dominated atmosphere covered by clouds which obscure absorption features in the infrared and hazes which give rise to scattering in the visible. Our results demonstrate the feasibility of exoplanet atmospheric characterization from the ground, even with meter-class telescopes.
Addressing the global threat of climate change is one of the present priorities of both companies and their customers. Societal trends demand a significant change in consumer behavior in the ...foreseeable future to contribute to the reduction in carbon emissions reaching the atmosphere, and national and international governments are committing their resources and efforts to this complex endeavor. The current paper addresses the other side of this conundrum, which is how firms can propose carbon-smart alternatives for their products on the market, in order to match the growing interest and the changing behaviors of the consumers. For this purpose, a research and innovation methodology is proposed to expand the design for concept X, namely, the design for sustainability set of guidelines in the area of developing products with a reduced carbon footprint under conditions of timeliness and economic viability. The research is based on refining practical experience and the use of consecrated management techniques and is validated through the employment of a Delphi-based forecasting process. The authors conclude that the large-scale adoption of such recommendations for the various domains of the manufacturing sector has the potential to contribute to climate change mitigation significantly.
Abstract
In recent years, the discovery of increasing numbers of rocky, terrestrial exoplanets orbiting nearby stars has drawn increased attention to the possibility of studying these planets’ ...atmospheric and surface properties. This is especially true for planets orbiting M dwarfs, whose properties can best be studied with existing observatories. In particular, the minerological composition of these planets and the extent to which they can retain their atmospheres in the face of intense stellar irradiation both remain unresolved. Here, we report the detection of the secondary eclipse of the terrestrial exoplanet GJ 1252b, obtained via 10 eclipse observations using the Spitzer Space Telescope’s IRAC2 4.5
μ
m channel. We measure an eclipse depth of
149
−
32
+
25
ppm, corresponding to a dayside brightness temperature of
1410
−
125
+
91
K. This measurement is consistent with the prediction for a bare rock surface. Comparing the eclipse measurement to a large suite of simulated planetary spectra indicates that GJ 1252b has a surface pressure of ≲10 bar, i.e., substantially thinner than the atmosphere of Venus. Assuming energy-limited escape, even a 100 bar atmosphere would be lost in <1 Myr, far shorter than our gyrochronological age estimate of 3.9 ± 0.4 Gyr. The expected mass loss could be overcome by mantle outgassing, but only if the mantle’s carbon content were >7% by mass—over two orders of magnitude greater than that found in Earth. We therefore conclude that GJ 1252b has no significant atmosphere. Model spectra with granitoid or feldspathic surface composition, but with no atmosphere, are disfavored at >2
σ
. The eclipse occurs just +1.4
−
1.0
+
2.8
minutes after orbital phase 0.5, indicating
e
cos
ω
= +0.0025
−
0.0018
+
0.0049
, consistent with a circular orbit. Tidal heating is therefore likely to be negligible with regard to GJ 1252b’s global energy budget. Finally, we also analyze additional, unpublished TESS transit photometry of GJ 1252b, which improves the precision of the transit ephemeris by a factor of 10, provides a more precise planetary radius of 1.180 ± 0.078
R
⊕
, and rules out any transit-timing variations with amplitudes ≳1 minute.
A SUPER-EARTH TRANSITING A NAKED-EYE STAR Winn, Joshua N.; Matthews, Jaymie M.; Dawson, Rebekah I. ...
Astrophysical journal. Letters,
08/2011, Letnik:
737, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We have detected transits of the innermost planet 'e' orbiting 55 Cnc (V = 6.0), based on two weeks of nearly continuous photometric monitoring with the MOST space telescope. The transits occur with ...the period (0.74 days) and phase that had been predicted by Dawson & Fabrycky, and with the expected duration and depth for the crossing of a Sun-like star by a hot super-Earth. Assuming the star's mass and radius to be 0.963+0.051 -- 0.029 M and 0.943 ? 0.010 R , the planet's mass, radius, and mean density are 8.63 ? 0.35 M {circled plus}, 2.00 ? 0.14 R {circled plus}, and 5.9+1.5 -- 1.1 g cm--3, respectively. The mean density is comparable to that of Earth, despite the greater mass and consequently greater compression of the interior of 55 Cnc e. This suggests a rock-iron composition supplemented by a significant mass of water, gas, or other light elements. Outside of transits, we detected a sinusoidal signal resembling the expected signal due to the changing illuminated phase of the planet, but with a full range (168 ? 70 ppm) too large to be reflected light or thermal emission. This signal has no straightforward interpretation and should be checked with further observations. The host star of 55 Cnc e is brighter than that of any other known transiting planet, which will facilitate future investigations.
The present paper approaches the timely topic of sustainable production with low carbon emissions, investigating the link between existing strategies and policies and the reality that manufacturers ...must deal with, with the appraisal going from high-level national and international plans to specific firm needs. This is in line with the preoccupations of manufacturers in Europe to retain and regain their market shares under strict environmental excellence, one of the defining features of the continent’s economy. The existing strategies, specialized plans and mechanisms for the reduction of emissions were analyzed to discern their structural relationships and the clarity and palpability of their content when passing through the successive levels of interest. The research methodology employs the MEAL Plan for determining the state of the art, and based on the findings, two specific tools were used for policy analysis and informing a brainstorming and discussion session aimed at future improvements. The instruments used are SWOT-Radar Screen methodology and latent semantic analysis as implemented by the Tropes Zoom software. Structural connections were revealed, together with an improved understanding of the interventions proposed in 5 European-level strategies, 14 national-level strategies (with a focus on Romania) and a case analysis for a generic manufacturing company. Among the main findings, the authors propose improved awareness development for all the stakeholders, strengthened and correlated monitoring of sustainability results and a better implementation of an institutional ecosystem for providing support to companies. The results obtained are intended for the use of policy makers to improve their future planning cycles in a way that supports the companies in achieving these societal goals.
Phase-curve measurements provide a global view of the composition, thermal structure, and dynamics of exoplanet atmospheres. Although most of the dozens of phase-curve measurements made to date are ...of large, massive hot Jupiters, there is considerable interest in probing the atmospheres of the smaller planets that are the more typical endproduct of the planet formation process. One such planet that is favorable for these studies is the ultrahot Neptune LTT 9779b, a rare denizen of the Neptune desert. A companion paper presents the planet's secondary eclipses and dayside thermal emission spectrum; in this work we describe the planet's optical and infrared phase curves, characterized using a combination of Spitzer and Transiting Exoplanet Survey Satellite (TESS) photometry. We detect LTT 9779b's thermal phase variations at 4.5 m, finding a phase amplitude of 358 106 ppm and no significant phase offset, with a longitude of peak emission occurring −10° 21° east of the substellar point. Combined with our secondary eclipse observations, these phase-curve measurements imply a 4.5 m dayside brightness temperature of 1800 120 K, a nightside brightness temperature of 700 430 K (<1350 K at 2 confidence), and a day-night brightness temperature contrast of 1110 460 K. We compare our data to the predictions of 3D general circulation models calculated at multiple metallicity levels and to similar observations of hot Jupiters experiencing similar levels of stellar irradiation. Though not conclusive, our measurement of its small 4.5 m phase offset, the relatively large amplitude of the phase variation, and the qualitative differences between our target's dayside emission spectrum and those of hot Jupiters of similar temperatures all suggest a supersolar atmospheric metallicity for LTT 9779b, as might be expected given its size and mass. Finally, we measure the planet's transits at both 3.6 m and 4.5 m, providing a refined ephemeris (P = 0.79207022 0.00000069 days, T0 = 2458783.51636 0.00027, BJDTDB) that will enable efficient scheduling of future observations to further characterize the atmosphere of this intriguing planet.
The James Webb Space Telescope (JWST) will likely revolutionize transiting exoplanet atmospheric science, due to a combination of its capability for continuous, long duration observations and its ...larger collecting area, spectral coverage, and spectral resolution compared to existing space-based facilities. However, it is unclear precisely how well JWST will perform and which of its myriad instruments and observing modes will be best suited for transiting exoplanet studies. In this article, we describe a prefatory JWST Early Release Science (ERS) Cycle 1 program that focuses on testing specific observing modes to quickly give the community the data and experience it needs to plan more efficient and successful transiting exoplanet characterization programs in later cycles. We propose a multi-pronged approach wherein one aspect of the program focuses on observing transits of a single target with all of the recommended observing modes to identify and understand potential systematics, compare transmission spectra at overlapping and neighboring wavelength regions, confirm throughputs, and determine overall performances. In our search for transiting exoplanets that are well suited to achieving these goals, we identify 12 objects (dubbed "community targets") that meet our defined criteria. Currently, the most favorable target is WASP-62b because of its large predicted signal size, relatively bright host star, and location in JWST's continuous viewing zone. Since most of the community targets do not have well-characterized atmospheres, we recommend initiating preparatory observing programs to determine the presence of obscuring clouds/hazes within their atmospheres. Measurable spectroscopic features are needed to establish the optimal resolution and wavelength regions for exoplanet characterization. Other initiatives from our proposed ERS program include testing the instrument brightness limits and performing phase-curve observations. The latter are a unique challenge compared to transit observations because of their significantly longer durations. Using only a single mode, we propose to observe a full-orbit phase curve of one of the previously characterized, short-orbital-period planets to evaluate the facility-level aspects of long, uninterrupted time-series observations.
It is important to explore the diversity of characteristics of low-mass, low-density planets to understand the nature and evolution of this class of planets. We present a homogeneous analysis of 12 ...new and 9 previously published broad-band photometric observations of the Uranus-sized extrasolar planet GJ 3470b, which belongs to the growing sample of sub-Jovian bodies orbiting M dwarfs. The consistency of our analysis explains some of the discrepancies between previously published results and provides updated constraints on the planetary parameters. Our data are also consistent with previous transit observations of this system. The physical properties of the transiting system can only be constrained as well as the host star is characterized, so we provide new spectroscopic measurements of GJ 3470 from 0.33 to 2.42 μm to aid our analysis. We find R
* = 0.48 ± 0.04 R⊙, M
* = 0.51 ± 0.06 M⊙, and T
eff = 3652 ± 50K for GJ 3470, along with a rotation period of 20.70 ± 0.15 d and an R-band amplitude of 0.01 mag, which is small enough that current transit measurements should not be strongly affected by stellar variability. However, to report definitively whether stellar activity has a significant effect on the light curves, this requires future multiwavelength, multi-epoch studies of GJ 3470. We also present the most precise orbital ephemeris for this system: T
o
= 2455983.70472 ± 0.00021BJDTDB, P = 3.336 6487
$^{+0.000\,0043}_{-0.000\,0033}$
d, and we see no evidence for transit timing variations greater than 1 min. Our reported planet to star radius ratio is 0.076 42 ± 0.000 37. The physical parameters of this planet are R
p = 3.88 ± 0.32 R⊕ and M
p = 13.73 ± 1.61 M⊕. Because of our revised stellar parameters, the planetary radius we present is smaller than previously reported values. We also perform a second analysis of the transmission spectrum of the entire ensemble of transit observations to date, supporting the existence of an H2-dominated atmosphere exhibiting a strong Rayleigh scattering slope.
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