We report spectroscopic observations of the earthshine reflected from the Moon. By applying our well-developed photometry methodology to spectroscopy, we are able to precisely determine the Earth's ...reflectance and its variation as a function of wavelength through a single night as the Earth rotates. These data imply that planned regular monitoring of earthshine spectra will yield valuable new inputs for climate models, which would be complementary to those from the more standard broadband measurements of satellite platforms. For our single night of reported observations, we find that Earth's albedo decreases sharply with wavelength from 500 to 600 nm, while being almost flat from 600 to 900 nm. The mean spectroscopic albedo over the visible is consistent with simultaneous broadband photometric measurements. Unlike previous reports, we find no evidence for either an appreciable "red" or "vegetation" edge in the Earth's spectral albedo, or for changes in this spectral region (700-740 nm) over the 40 of Earth's rotation covered by our observations. Whether or not the absence of a vegetation signature in disk-integrated observations of the Earth is a common feature awaits the analysis of more earthshine data and simultaneous satellite cloud maps at several seasons. If our result is confirmed, it would limit efforts to use the red edge as a probe for Earth-like extrasolar planets. Water vapor and molecular oxygen signals in the visible earthshine, and carbon dioxide and methane in the near-infrared, are more likely to be powerful probes.
Context. WASP-127b is a planet with one of the lowest densities discovered to date. With a sub-Saturn mass (Mp = 0.18 ± 0.02 MJ) and super-Jupiter radius (Rp = 1.37 ± 0.04 RJ), it orbits a bright G5 ...star that is about to leave the main-sequence. Aims. We aim to explore the atmosphere of WASP-127b in order to retrieve its main atmospheric components, and to find hints for its intriguing inflation and evolutionary history. Methods. We used the ALFOSC spectrograph at the NOT telescope to observe a low-resolution (R ~ 330, seeing limited) long-slit spectroscopic time series during a planetary transit, and present here the first transmission spectrum for WASP-127b. Results. We find a strong Rayleigh slope at blue wavelengths and a hint of Na absorption, although the quality of the data does not allow us to claim a detection. At redder wavelengths the absorption features of TiO and VO are the best explanation to fit the data. Conclusions. Although observations with a higher signal-to-noise ratio are needed to conclusively confirm the absorption features, WASP-127b seems to posses a cloud-free atmosphere and is one of the best targets on which to perform further characterization studies in the near future.
We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V = 9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite ...(TESS) in Sectors 3 and 4. We combine the TESS photometry with archival High Accuracy Radial velocity Planet Searcher spectra to confirm the planetary nature of the transit signals and derive the masses of the two transiting planets. With an orbital period of 4.8 days, a mass of and a radius of 1.64 0.06 R⊕, HD 15337 b joins the growing group of short-period super-Earths known to have a rocky terrestrial composition. The sub-Neptune HD 15337 c has an orbital period of 17.2 days, a mass of , and a radius of 2.39 0.12 R⊕, suggesting that the planet might be surrounded by a thick atmospheric envelope. The two planets have similar masses and lie on opposite sides of the radius gap, and are thus an excellent testbed for planet formation and evolution theories. Assuming that HD 15337 c hosts a hydrogen-dominated envelope, we employ a recently developed planet atmospheric evolution algorithm in a Bayesian framework to estimate the history of the high-energy (extreme ultraviolet and X-ray) emission of the host star. We find that at an age of 150 Myr, the star possessed on average between 3.7 and 127 times the high-energy luminosity of the current Sun.
K2-146 is a cool, 0.358 dwarf that was found to host a mini-Neptune with a 2.67 day period. The planet exhibited strong transit timing variations (TTVs) of greater than 30 minutes, indicative of the ...presence of an additional object in the system. Here we report the discovery of the previously undetected outer planet in the system, K2-146 c, using additional photometric data. K2-146 c was found to have a grazing transit geometry and a 3.97 day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146 b and c were measured using observations spanning a baseline of almost 1200 days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146 b has a radius of 2.25 0.10 and a mass of 5.6 0.7 , whereas K2-146 c has a radius of and a mass of 7.1 0.9 . The inner and outer planets likely have moderate eccentricities of e = 0.14 0.07 and 0.16 0.07, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2 Myr. We show that the resonance angles of the planet pair are librating, which may be an indication that K2-146 b and c are in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin.
It has been posited that lunar eclipse observations may help predict the in-transit signature of Earth-like extrasolar planets. However, a comparative analysis of the two phenomena addressing in ...detail the transport of stellar light through the planet's atmosphere has not yet been presented. Here, we proceed with the investigation of both phenomena by making use of a common formulation. Our starting point is a set of previously unpublished near-infrared spectra collected at various phases during the 2008 August lunar eclipse. We then take the formulation to the limit of an infinitely distant observer in order to investigate the in-transit signature of the Earth-Sun system as being observed from outside our solar system. The refraction bending of sunlight rays that pass through Earth's atmosphere is a critical factor in the illumination of the eclipsed Moon. Likewise, refraction will have an impact on the in-transit transmission spectrum for specific planet-star systems depending on the refractive properties of the planet's atmosphere, the stellar size, and the planet's orbital distance. For the Earth-Sun system, at mid-transit, refraction prevents the remote observer's access to the lower ~12-14 km of the atmosphere and, thus, also to the bulk of the spectroscopically active atmospheric gases. We demonstrate that the effective optical radius of the Earth in-transit is modulated by refraction and varies by ~12 km from mid-transit to internal contact. The refractive nature of atmospheres, a property which is rarely accounted for in published investigations, will pose additional challenges to the characterization of Earth-like extrasolar planets. Refraction may have a lesser impact for Earth-like extrasolar planets within the habitable zone of some M-type stars.
Aims. We announce confirmation of Kepler-418b, one of two proposed planets in this system. This is the first confirmation of an exoplanet based primarily on the transit color signature technique. ...Methods. We used the Kepler public data archive combined with multicolor photometry from the Gran Telescopio de Canarias and radial velocity follow-up using FIES at the Nordic Optical Telescope for confirmation. Results. We report a confident detection of a transit color signature that can only be explained by a compact occulting body, entirely ruling out a contaminating eclipsing binary, a hierarchical triple, or a grazing eclipsing binary. Those findings are corroborated by our radial velocity measurements, which put an upper limit of ~1 MJup on the mass of Kepler-418b. We also report that the host star is significantly blended, confirming the ~10% light contamination suspected from the crowding metric in the Kepler light curve measured by the Kepler team. We report detection of an unresolved light source that contributes an additional ~30% to the target star, which would not have been detected without multicolor photometric analysis. The resulting planet-star radius ratio is 0.110 ± 0.0025, more than 25% more than the 0.087 measured by Kepler leading to a radius of 1.20 ± 0.16 RJup instead of the 0.94 RJup measured by the Kepler team. Conclusions. This is the first confirmation of an exoplanet candidate based primarily on the transit color signature, demonstrating that this technique is viable from ground for giant planets. It is particularly useful for planets with long periods such as Kepler-418b, which tend to have long transit durations. While this technique is limited to candidates with deep transits from the ground, it may be possible to confirm earth-like exoplanet candidates with a few hours of observing time with an instrument like the James Webb Space Telescope. Additionally, multicolor photometric analysis of transits can reveal unknown stellar neighbors and binary companions that do not affect the classification of the transiting object but can have a very significant effect on the perceived planetary radius.
Traditionally the Earth's reflectance has been assumed to be roughly constant, but large decadal variability, not reproduced by current climate models, has been reported lately from a variety of ...sources. We compare here the available data sets related to Earth's reflectance, in order to assess the observational constraints on the models. We find a consistent picture among all data sets of an albedo decreased during 1985–2000 between 2–3 and 6–7 W/m2, which is highly climatically significant. The largest discrepancy among the data sets occurs during 2000–2004, when some present an increasing reflectance trend, while CERES observations show a steady decrease of about 2 W/m2.
We present the discovery of Qatar-7b-a very hot and inflated giant gas planet orbiting close to its parent star. The host star is a relatively massive main-sequence F-star with mass and radius and , ...respectively, at a distance d = 726 26 pc, and an estimated age ∼1 Gyr. With its orbital period of P = 2.032 days, the planet is located less than five stellar radii from its host star and is heated to a high temperature Teq 2100 K. From a global solution to the available photometric and radial velocity observations, we calculate the mass and radius of the planet to be = 1.88 0.25 and = 1.70 0.03 , respectively. The planet radius and equilibrium temperature put Qatar-7b in the top 6% of the hottest and largest known exoplanets. With its large radius and high temperature, Qatar-7b is a valuable addition to the short list of targets that offer the best opportunity for studying their atmospheres through transmission spectroscopy.
Big Bear Solar Observatory is building the world's first global earthshine network to measure Earth's large‐scale reflectance. Our first remote station was deployed in late 2003 at the Crimean ...Astronomical Observatory. Here we compare the data obtained from the two earthshine stations, Crimea and Big Bear. We find that the retrieved quantities from both stations are consistent and that the data may be easily combined into a single data set expanding the temporal and geographical coverage of our Earth reflectance measurements from California. We also detail our plans and the expected coverage with a larger network of stations.
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