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1.
There are many rotating spheroids in the universe, and many astronomers and physicists have used theoretical methods to study the characteristics of stellar gravity since Newton's time. This paper derives the solutions of eight scattering states ( ϕ ( 0 ) , χ ( 0 ) , ϕ ( 1 ) , χ ( 1 ) , ϕ ( 2 ) $$ \Big({\phi}^{(0)},{\chi}^{(0)},{\phi}^{(1)},{\chi}^{(1)},{\phi}^{(2)} $$ , χ ( 2 ) , ϕ ( 3 ) $$ {\chi}^{(2)},{\phi}^{(3)} $$ , and χ ( 3 ) ) $$ {\chi}^{(3)}\Big) $$ for the Dirac equation with positive-energy E = im $$ E= im $$ , and establishes the relationship between the differential scattering cross section σ i ( p , θ , φ ) $$ {\sigma}_i\left(p,\theta, \varphi \right) $$ and the stellar density μ $$ \mu $$ . It is found that: (1) For the eight scattering states, their average scattering cross-sections σ i ‾ $$ \overline{\sigma_i} $$ are proportional to μ 2 $$ {\mu}^2 $$ , and depend on the star's radius, and the higher the stellar density μ $$ \mu $$ , the greater the sensitivity of σ i ‾ $$ \overline{\sigma i} $$ to the change of μ $$ \mu $$ ; (2) For the four scattering states χ ( i ) , i = 0 , 1 , 2 , 3 $$ {\chi}^{(i)},i=0,1,2,3 $$ , their average scattering amplitudes f ‾ ( p , θ ) $$ \overline{f}\left(p,\theta \right) $$ and σ ‾ ( p , θ ) $$ \overline{\sigma}\left(p,\theta \right) $$ depend on the mass m $$ m $$ of the particles; while for the other four scattering states ϕ ( i ) $$ {\phi}^{(i)} $$ , i = 0 , 1 , 2 , 3 $$ i=0,1,2,3 $$ , then f ‾ $$ \overline{f} $$ and σ ‾ $$ \overline{\sigma} $$ are independent of m $$ m $$ . This study links the gravitational characteristics of stars with the scattering cross section, creating a new method for studying the gravitational characteristics, which helps to reveal the mystery of the gravity of rotating ellipsoidal stars.  相似文献   

2.
A laboratory study was performed using the Visible Oxford Space Environment Goniometer in which the broadband (350–1250 nm) bidirectional reflectance distribution function (BRDF) of the Winchcombe meteorite was measured, across a range of viewing angles—reflectance: 0°–70°, in steps of 5°; incidence: 15°, 30°, 45°, and 60°; and azimuthal: 0°, 90°, and 180°. The BRDF dataset was fitted using the Hapke BRDF model to (1) provide a method of comparison to other meteorites and asteroids, and (2) to produce Hapke parameter values that can be used to extrapolate the BRDF to all angles. The study deduced the following Hapke parameters for Winchcombe: w = 0.152 ± 0.030, b = 0.633 ± 0.064, and hS = 0.016 ± 0.008, demonstrating that it has a similar w value to Tagish Lake (0.157 ± 0.020) and a similar b value to Orgueil (0.671 ± 0.090). Importantly, the surface profile of the sample was characterized using an Alicona 3D® instrument, allowing two of the free parameters within the Hapke model φ and θ ¯ , which represent porosity and surface roughness, respectively, to be constrained as φ = 0.649 ± 0.023 and θ ¯ = 16.113° (at 500 μm size scale). This work serves as part of the characterization process for Winchcombe and provides a reference photometry dataset for current and future asteroid missions.  相似文献   

3.
High‐temperature solid‐state electrochemistry techniques (EMF method) were used to measure the oxygen fugacity (fO2) of the ordinary chondrites Ochansk (H4), Savtschenskoje (LL4), Elenovka (L5), Vengerovo (H5), and Kharkov (L6). The fO2 results are presented in the form of the following equations: It was found that fO2 regularly increases from H chondrites to LL chondrites. Measured fO2 are ~1.5 higher than those previously calculated from mineral assemblages. Kharkov (L6) is a little more oxidized than Elenovka (L5) in agreement with the progressive oxidation model. At the same time, Ochansk (H4) is more oxidized than Vengerovo (H5) and exhibits a slightly different slope compared to other chondrites and at T > 1200 K, becomes more reduced than Kharkov (L6) or Elenovka (L5). Measured oxygen fugacity values of meteorites fall within (0.1–1.0)·log fO2 of one another. The possible explanation of discrepancies between measured and calculated values is discussed.  相似文献   

4.
Core samples from the Chicxulub impact structure provide insights into the formation processes of a shallow-marine-target, complex crater. Although previous studies investigated the impactites (generally suevitic and polymict breccias) of the Yaxcopoil-1 (YAX-1) drill core in the Chicxulub impact structure, the interpretation of its deposition remains controversial. Here, we analyze planar deformation features (PDFs), grain size, and abundance of shocked quartz throughout the YAX-1 impactite sequence (794–895 m in depth). PDF orientations of most quartz grains in YAX-1 impactites show a distribution of both low angles ({104}, {103}, {102}) and high angles (orientations higher than 55° to c-axis), while the lower part of the impactite sequence contains quartz showing only PDF orientations of low angles. High-abundance, coarse-grained shocked quartz is found from the lower to middle parts of the impactites, whereas it abruptly changes to low-abundance, fine-grained shocked quartz within the upper part. In the uppermost part of the impactites, repeated oscillations in contents of these two components are observed. PDF orientation pattern suggests most of the shocked quartz grains experienced a range of shock pressure, except two samples in the lower part of impactites, which experienced only a high level of shock. We suggest that the base and lower part of the impactite sequence were formed by ejecta curtain and melt surge deposits, respectively. Our results are also consistent with the interpretation that the middle part of the impactite sequence is fallback ejecta from the impact plume. Additionally, we support the contention that massive seawater resurges into the crater occurred during the deposition of the upper and uppermost part of the impactites.  相似文献   

5.
Chondrules probably formed during a small window of time ~1–4 Ma after CAIs, when most solid matter in the asteroid belt was already in the form of km-sized planetesimals. They are unlikely, therefore, to be “building blocks” of planets or abundant on asteroids, but more likely to be a product of energetic events common in the asteroid belt at that epoch. Laboratory experiments indicate that they could have formed when solids of primitive composition were heated to temperatures of ~1600 K and then cooled for minutes to hours. A plausible heat source for this is magma, which is likely to have been abundant in the asteroid belt at that time, and only that time, due to the trapping of 26Al decay energy in planetesimal interiors. Here, we propose that chondrules formed during low-speed ( ≲ 1 km s − 1 ) collisions between large planetesimals when heat from their interiors was released into a stream of primitive debris from their surfaces. Heating would have been essentially instantaneous and cooling would have been on the dynamical time scale, 1 / Gρ ~30 min, where ρ is the mean density of a planetesimal. Many of the heated fragments would have remained gravitationally bound to the merged object and could have suffered additional heating events as they orbited and ultimately accreted to its surface. This is a hybrid of the splash and flyby models: We propose that it was the energy released from a body's molten interior, not its mass, that was responsible for chondrule formation by heating primitive debris that emerged from the collision.  相似文献   

6.
In this research article, we have investigated resonant curves due to the rate of change of earth’s equatorial ellipticity parameter (γ̇), steady-state value of the angular velocity of the moon (θ̇mo), and angular velocity of barycenter (α0̇) in the Earth-Moon system. Equations of motion of the moon are determined in a spherical coordinate system with the help of the gravitational potential of the earth. By using the unperturbed solution, equations of motion of the moon reduced into the second-order differential equation. From the solution it is observed that resonance occurs due to the frequencies γ̇, θ̇m0, and α0̇ at the resonant points θ̇m0=2γ̇, 3θ̇m0=2γ̇, θ̇m0=γ̇, θ̇m0=α̇0. Finally, we have analyzed the phase portrait and phase space by method of Poincaré section when the system is free from forces.  相似文献   

7.
Carbon and nitrogen data from stepped combustion analysis of eight angrites, seven eucrites, and two diogenites, alongside literature data from a further nine eucrites and two diogenites, have been used to assess carbon and nitrogen incorporation and isotope fractionation processes on the angrite parent body (APB), for comparison with volatile behavior on the HED parent body (4 Vesta). A subset of the angrite data has been reported previously (Abernethy et al. 2013 ). Two separate families of volatile components were observed. They were (1) moderately volatile material (MVM), mostly combusting between ~500 and 750 °C and indistinguishable from terrestrial contamination and (2) refractory material (RM), mainly released above 750 °C and thought to be carbon (as ) and nitrogen (as N2 or ) dissolved within the silicate lattice, fitting with the slightly oxidized (~IW to IW+2) angrite fO2 conditions. Isotopic fractionation trends for carbon and nitrogen within the plutonic and basaltic (quenched) angrites suggest that the behavior of the two volatile elements is loosely coupled, but that the fractionation process differs between the two angrite subgroups. Comparison with results from eucrites and diogenites implies similarities between speciation of carbon and nitrogen on 4 Vesta and the APB, with the latter being more enriched in volatiles than the former.  相似文献   

8.
The first JWST observations of hot Jupiters showed an unexpected detection of SO 2 $$ {}_2 $$ in their hydrogen-rich atmospheres. We investigate how much sulfur can be expected in the atmospheres of rocky exoplanets and which sulfur molecules can be expected to be most abundant and detectable by transmission spectroscopy. We run thermochemical equilibrium models at the crust–atmosphere interface, considering surface temperatures 500–5000 K, surface pressures 1–100 bar, and various sets of element abundances based on common rock compositions. Between 1000 and 2000 K, we find gaseous sulfur concentrations of up to 25% above the rock in our models. SO 2 $$ {}_2 $$ , SO, H 2 $$ {}_2 $$ S, and S 2 $$ {}_2 $$ are by far the most abundant sulfur molecules. SO 2 $$ {}_2 $$ shows potentially detectable features in transmission spectra at about 4 μ $$ \mu $$ m, between 7 and 8 μ $$ \mu $$ m, and beyond 15 μ $$ \mu $$ m. In contrast, the sometimes abundant H 2 $$ {}_2 $$ S molecule is difficult to detect in these spectra, which are mostly dominated by H 2 $$ {}_2 $$ O and CO 2 $$ {}_2 $$ . Although the molecule PS only occurs with concentrations < 300 $$ <300 $$ ppm, it can cause a strong absorption feature between 0.3 and 0.65 μ $$ \mu $$ m in some of our models for high surface pressures. The detection of sulfur molecules would enable a better characterization of the planetary surface.  相似文献   

9.
We report a correlated NanoSIMS‐transmission electron microscopy study of the ungrouped carbonaceous chondrite Northwest Africa (NWA) 5958. We identified 10 presolar SiC grains, 2 likely presolar graphite grains, and 20 presolar silicate and/or oxide grains in NWA 5958. We suggest a slight modification of the commonly used classification system for presolar oxides and silicates that better reflects the grains’ likely stellar origins. The matrix‐normalized presolar SiC abundance in NWA 5958 is ppm (2σ) similar to that seen in many classes of unmetamorphosed chondrites. In contrast, the matrix‐normalized abundance of presolar O‐rich phases (silicates and oxides) is ppm (2σ), much lower than seen in interplanetary dust particles and the least‐altered CR, CO, and ungrouped C chondrites, but close to that reported for CM chondrites. NanoSIMS mapping also revealed an unusual 13C‐enriched (δ13C≈100–200‰) carbonaceous rim surrounding a 1.4 μm diameter phyllosilicate grain. Transmission electron microscopy (TEM) analysis of two presolar grains with a likely origin in asymptotic giant branch stars identified one as enstatite and one as Al‐Mg spinel with minor Cr. The enstatite grain amorphized rapidly under the electron beam, suggesting partial hydration. TEM data of NWA 5958 matrix confirm that it has experienced aqueous alteration and support the suggestion of Jacquet et al. (34) that this meteorite has affinities to CM2 chondrites.  相似文献   

10.
We evaluate the feasibility of Bose–Einstein condensate stars (BECS) as models for the interior of neutron stars (NSs). BECS are compact objects composed of bosons, formed through the spin-parallel pairing of neutrons. Here, we utilize the astronomical data from GW170817, XMMU J173203.3-344518 (the lightest NS known), and a novel lower limit on NS core heat capacity to scrutinize the compatibility of BECS with these recent observations of NSs. Our specific focus is to constrain the values of the scattering length a $$ a $$ , parameter determining the strength of particle interactions in the model. Our analysis suggests that if the stars involved in GW170817 were BECSs, the scattering length of their constituent bosons should fall within the 4 $$ 4 $$ to 10 $$ 10 $$ fm range. Additionally, at a scattering length of a ∼ 3.1 − 4 $$ a\sim 3.1-4 $$ fm, stars with mass and radius characteristics akin to XMMU J173203.3-344518 are identified. Moreover, we find that the heat capacity depends on the mass and temperature of BECS, and surpasses the established lower bound for NS cores when a > 2 − 5 $$ a>2-5 $$ fm. In summary, our results endorse BECS models with a ∼ 4 $$ a\sim 4 $$ fm, providing NS observables in agreement with diverse observations and contributing to the understanding of NS interiors.  相似文献   

11.
In this work, we study how to improve well-known techniques for detecting progenitors/descendants of galaxies, such as the NDpredict program, when applied to galaxies in clusters. The improvement of this particular method is based on the use of the red sequence of galaxies in those environments. Objects close to the red sequence in the color and magnitude diagram are more likely to belong to the cluster. This defines a probability scale which is then combined with the one generated by NDpredict. This procedure is optimized for the study of galaxies in clusters over different epochs. Our main result is that, for a sample composed of 120 $$ 120 $$ clusters, with masses greater than 10 13.25 M ⊙ $$ {10}^{13.25}{M}_{\odot } $$ , selected from the IllustrisTNG simulations (namely, the TNG100 runs). In 99 % $$ 99\% $$ of the cases (i.e., 119 $$ 119 $$ systems), we obtain better performance with the red sequence method in comparison to the original NDpredict, and the average gain obtained is 28 % $$ 28\% $$ in the identification of descendants for this sample of cluster galaxies.  相似文献   

12.
This article focuses on the implications of the recently developed commutative formulation based on branch-cutting cosmology, the Wheeler–DeWitt equation, and Hořava–Lifshitz quantum gravity. Assuming a mini-superspace of variables, we explore the impact of an inflaton-type scalar field ϕ ( t ) $$ \phi (t) $$ on the dynamical equations that describe the trajectories evolution of the scale factor of the Universe, characterized by the dimensionless helix-like function ln − 1 [ β ( t ) ] $$ {\ln}^{-1}\left[\beta (t)\right] $$ . This scale factor characterizes a Riemannian foliated spacetime that topologically overcomes the big bang and big crunch singularities. Taking the Hořava–Lifshitz action as our starting point, which depends on the scalar curvature of the branched Universe and its derivatives, with running coupling constants denoted as g i $$ {g}_i $$ , the commutative quantum gravity approach preserves the diffeomorphism property of General Relativity, maintaining compatibility with the Arnowitt–Deser–Misner formalism. We investigate both chaotic and nonchaotic inflationary scenarios, demonstrating the sensitivity of the branch-cut Universe's dynamics to initial conditions and parameterizations of primordial matter content. The results suggest a continuous connection of Riemann surfaces, overcoming primordial singularities and exhibiting diverse evolutionary behaviors, from big crunch to moderate acceleration.  相似文献   

13.
Circumstellar disk (CD) around the first generation of stars have been numerically investigated here to see if the cooling regimes also play a role in the formation and evolution of the disk associated with the most massive protostars (MMPS). Also, an emphasis is given to exploring the effect of the initial turbulent motion of the metal-free gas on the resulting morphology of the CD. For this, a systematic range of Mach number ℳ = 0 . 1 − 1 . 0 $$ \mathcal{M}=0.1-1.0 $$ has been examined. It has been found that the disk-to-star mass ratio M disk $$ {M}_{\mathrm{disk}} $$ / M star $$ {M}_{\mathrm{star}} $$ is larger when the model evolution is based on the first H 2 $$ {}_2 $$ line cooling followed by subsequent cooling via collision-induced emission than in the model where only H 2 $$ {}_2 $$ line cooling remains operative. Also, irrespective of the initial turbulence in the cloud, the former type of model yields a CD as massive as 7.66 M ⊙ $$ {}_{\odot } $$ while the latter type produces a disk as massive as 1.29 M ⊙ $$ {}_{\odot } $$ . Moreover, the inner part of the CD is found dominated by higher subsonic turbulent motions in the case of the former type of models than in the latter type. CDs around MMPS in both types of models show stable disk structures.  相似文献   

14.
Located at less than two pc away, Luhman 16 AB (WISE J104915.57-531906.1) is the closest pair of brown dwarfs and the third closest “stellar” system to Earth. An exoplanet candidate in the Luhman 16 binary system was reported in 2017 based on a weak astrometric signature in the analysis of 12 HST epochs. An additional epoch collected in 2018 and re-analysis of the data with more advanced methods further increased the significance level of the candidate, consistent with a Neptune-mass exoplanet orbiting one of the Luhman 16 brown dwarf components. We report the joint analysis of these previous data together with two new astrometric HST epochs we obtained to confirm or disprove this astrometric signature. Our new analysis rules out the presence of a planet orbiting one component of the Luhman 16 AB system for masses ℳ $$ \mathrm{\mathcal{M}} $$ ≳ $$ \gtrsim $$ 1.5 M♆ (Neptune masses) and periods between 400 and 5000 days. However, the presence of third bodies with masses ℳ $$ \mathrm{\mathcal{M}} $$ ≲ $$ \lesssim $$ 3 M♆ and periods between 2 and 400 days ( ∼ $$ \sim $$ 1.1 years) cannot be excluded. Our measurements make significant improvements to the characterization of this sub-stellar binary, including its mass-ratio 0.8305 ± 0.0006 $$ \pm 0.0006 $$ , individual component masses 35.4 ± $$ \pm $$ 0.2 MꝜ and 29.4 ± $$ \pm $$ 0.2 MꝜ (Jupiter masses), and parallax distance 1.9960 pc ± $$ \pm $$ 50 AU. Comparison of the masses and luminosities of Luhman 16 AB to several evolutionary models shows persistent discrepancies in the ages of the two components, but strengthens the case that this system is a member of the 510 ± $$ \pm $$ 95 Myr Oceanus Moving Group.  相似文献   

15.
Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al. 2014 ), with an apparent diameter of 34 km, centered at 29°35′N, 38°42′E. The structure is formed in Cambrian–Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2‐D reflection seismic profiles and six drilled wells. First‐order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring‐like low, respectively. The wells were drilled within the central uplift, the deepest among them exceed 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {103}, and less frequently along {101} and {104}. Planar fractures (PFs) predominantly occur along (0001) and {101}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1–2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.  相似文献   

16.
The pulsar magnetic inclination angle is a key parameter for pulsar physics. It influences the observable properties of pulsars, such as the pulse beam width, braking index, polarization, and emission geometry. In this study, we give a brief overview of the current state of knowledge and research on this parameter and its implications for the internal physics of pulsars. We use the observed pulsar data of magnetic inclination angle and braking index to constrain the star's number of precession cycles, ξ $$ \xi $$ , which reflects the interaction between superfluid neutrons and other particles inside a neutron star (NS). We apply the method proposed by Cheng et al. (Cheng, Q., Zhang, S. N., Zheng, X. P., & Fan, X. L., 2019, Phys. Rev. D, 99, 083011) to analyze the data of PSR J2013 + 3845 and obtain the constraints for ξ $$ \xi $$ ranging from 2 . 393 × 1 0 5 $$ 2.393\times 1{0}^5 $$ to 1 . 268 × 1 0 6 $$ 1.268\times 1{0}^6 $$ . And further analysis suggests that the internal magnetic field structure of PSR J2013 + 3845 is likely dominated by toroidal components. This study may help us understand the process of internal viscous dissipation and the related evolution of the inclination angles of pulsars, and may have important implications for the study of continuous gravitational wave emissions from NS.  相似文献   

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20.
CCD photometry of the eclipsing binary system V1036 Her was performed using Johnson V filter in Dr. Mojtahedi Observatory of the University of Birjand during July-August 2017 and July 2018. Moreover, the spectroscopy of the system was carried out by TRES during April 2018. A mass ratio of 3.07(27)is obtained and an initial effective temperature of 5500 was suggested. For the first time, the relative and absolute parameters of the system are determined by analyzing the light curve and radial velocity data. The results indicate that V1036 Her is a W-subtype W UMa system with a degree of overcontact of 22%. The analysis of the period change shows that the period of the system changes with the rate of P˙=2.23(4)×10−7day/year. With the assumption of the system mass conservation, a mass transfer rate from the primary to the secondary component of m˙1=1.00(3)×10−7M⊙/year is probable. Additionally, a periodic behavior with a period of about 10 years is observed in the O-C curve, which predicts the possibility of a third body with a minimum mass of 0.14(1)M⊙.  相似文献   

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