The nearly circular (mean eccentricity e ≈ 0.06) and coplanar (mean mutual inclination i ≈ 3°) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits ( e ≈ 0.3). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the Large Sky Area MultiObject Fiber Spectroscopic Telescope (LAMOST) observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with e ≈ 0.3, whereas the multiples are on nearly circular ( e = 0.04 +0.03 −0.04 ) and coplanar ( i = 1.4 +0.8 −1.1 degree) orbits similar to those of the solar system planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation [ e ≈ (1-2)× i] between mean eccentricities and mutual inclinations. The prevalence of circular orbits and the common relation may imply that the solar system is not so atypical in the galaxy after all.orbital eccentricities | exoplanets | transit | solar system | planetary dynamics O ur knowledge of orbital shapes (parameterized with eccentricities) of planetary systems has been drastically advanced in the last 2 decades largely thanks to the radial velocity (RV) planet surveys, but there remain some major puzzles. For example, the majority of RV planets are found on eccentric orbits ( e ≈ 0.3) (1) in contrast to the solar system planets, raising a fundamental question: Is the solar system an atypical member of the planetary system population in the galaxy (2)? Furthermore, the RV method has some key limitations. For example, several notable biases and degeneracies can introduce considerable systematical uncertainties into the eccentricity distributions derived from the RV technique (3-5). In addition, the majority of eccentricities measured using the RV method are for giant planets (e.g., Jupiter size), whereas the eccentricity distributions of smaller planets (e.g., Earth to Neptune size) remain poorly understood.Complementary to the RV technique, the Kepler mission has discovered thousands of planet candidates down to about Earth radius using the transit technique (6). About half of the Kepler planets are in systems with multiple transiting planets, and on average, they are on nearly coplanar orbits sim...

Determining the orbital eccentricity of an extrasolar planet is critically important for understanding the system's dynamical environment and history. However, eccentricity is often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought to contain a single, moderateeccentricity planet have been shown, after further monitoring, to host two planets on nearly-circular orbits. We investigate published apparent single-planet systems to see if the available data can be better fit by two lower-eccentricity planets. We identify nine promising candidate systems and perform detailed dynamical tests to confirm the stability of the potential new multiple-planet systems. Finally, we compare the expected orbits of the single-and double-planet scenarios to better inform future observations of these interesting systems.

We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period [Formula: see text] planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more "puffed up" compared with that around metal-poor hosts. In two period-radius regimes, planets preferentially reside around metal-rich stars, while there are hardly any planets around metal-poor stars. One is the well-known hot Jupiters, and the other one is a population of Neptune-size planets ([Formula: see text]), dubbed "Hoptunes." Also like hot Jupiters, Hoptunes occur more frequently in systems with single-transiting planets although the fraction of Hoptunes occurring in multiples is larger than that of hot Jupiters. About [Formula: see text] of solar-type stars host Hoptunes, and the frequencies of Hoptunes and hot Jupiters increase with consistent trends as a function of [Fe/H]. In the planet radius distribution, hot Jupiters and Hoptunes are separated by a "valley" at approximately Saturn size (in the range of [Formula: see text]), and this "hot-Saturn valley" represents approximately an order-of-magnitude decrease in planet frequency compared with hot Jupiters and Hoptunes. The empirical "kinship" between Hoptunes and hot Jupiters suggests likely common processes (migration and/or formation) responsible for their existence.

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The Chinese Small Telescope ARray (CSTAR) is a group of four identical, fully automated, static 14.5 cm telescopes. CSTAR is located at Dome A, Antarctica and covers 20 deg 2 of sky around the South Celestial Pole. The installation is designed to provide high-cadence photometry for the purpose of monitoring the quality of the astronomical observing conditions at Dome A and detecting transiting exoplanets. CSTAR has been operational since 2008, and has taken a rich and high-precision photometric data set of 10,690 stars. In the first observing season, we obtained 291,911 qualified science frames with 20-second integrations in the i-band. Photometric precision reaches ∼ 4 mmag at 20-second cadence

Lung maturation is not limited to proper structural development, but also includes differentiation and functionality of various highly specialized alveolar cell types. Alveolar type 1 cells (AT1s) occupy nearly 95% of the alveolar surface and are critical for establishing efficient gas exchange in the mature lung. AT1 cells arise from progenitors specified during the embryonic stage as well as alveolar epithelial progenitors expressing surfactant protein C (Sftpc pos cells) during postnatal and adult stages. Previously, we found that Wnt5a, a non-canonical Wnt ligand, is required for differentiation of AT1 cells during the saccular phase of lung development. To further investigate the role of Wnt5a in AT1 cell differentiation, we generated and characterized a conditional Wnt5a gain-of-function mouse model. Neonatal Wnt5a gain-of-function disrupted alveologenesis through inhibition of cell proliferation. In this setting Wnt5a downregulated beta-catenin-dependent canonical Wnt signaling, repressed AT2 (anti-AT2) and promoted AT1 (pro-AT1) lineage-specific gene expression. In addition, we identified two subpopulations of Sftpc high and Sftpc low alveolar epithelial cells. In Sftpc low cells, Wnt5a exhibits pro-AT1 and anti-AT2 effects, concurrent with inhibition of canonical Wnt signaling. Interestingly, in the Sftpc high subpopulation, although increasing AT1 lineage-specific gene expression, Wnt5a gain-of-function did not change AT2 gene expression, nor inhibit canonical Wnt signaling. Using primary epithelial cells isolated from human fetal lungs we demonstrate that this property of Wnt5a is evolutionarily conserved. Wnt5a therefore serves as a selective regulator that ensures proper AT1/AT2 balance in the developing lung.

Objective Knee osteoarthritis (KOA) is based on degenerative pathological changes. miR-155 is involved in regulating KOA. This study estimated the mechanism of miR-155 in mouse KOA chondrocytes. Methods Mouse KOA chondrocyte model was established by lipopolysaccharide (LPS) induction and identified through Collagen II immunofluorescence staining and toluidine blue staining. LPS-induced KOA chondrocytes were transfected with miR-155 inhibitor or/and si-SMAD2, followed by the evaluation of miR-155 expression, pyroptosis, the SMAD2/NLRP3/Caspase-1 axis-related protein levels, IL-1β and 1L-18 levels, and cell viability by RT-qPCR, FAM-FLICA Caspase-1 Detection Kit, Western blot, ELISA, and MTT assays, respectively. The binding sites between miR-155 and SMAD2 were predicted online and the binding relationship was verified by dual-luciferase assay. Results miR-155 was highly-expressed in LPS-induced KOA chondrocytes. miR-155 knockdown increased cell viability and decreased pyroptotic chondrocytes, and Caspase-1, 1L-1β and 1L-18 levels. miR-155 targeted SMAD2. SMAD2 knockdown partially annulled the effects of miR-155 silencing on inhibiting KOA chondrocyte pyroptosis. NLRP3 pathway was activated in LPS-induced KOA chondrocytes, inhibited after miR-155 knockdown, and activated again after further SMAD2 knockdown. NLRP3 inhibition suppressed Caspase-1, IL-1β, and IL-18 levels and chondrocyte pyroptosis and increased cell viability. Conclusion miR-155 knockdown inhibited the NLRP3/Caspase-1 pathway by targeting SMAD2, thus inhibiting mouse KOA chondrocyte pyroptosis.