Does pluto have a substantial atmosphere?

The presence of CH₄ ice on Pluto implies that Pluto may have a substantial atmosphere consisting of heavy gases. Without such an atmosphere, sublimation of the CH₄ ice would be so rapid on a cosmogonic time scale that either such an atmosphere would soon develop through the exposure of gases trapped in the CH₄ ice or else the surface CH₄ ice would soon be all sublimated away as other, more stable, ices became exposed. If such stable ices were present from the beginning, the existence of CH₄ frosts would also imply that Pluto's present atmosphere contains a remnant of its primordial atmosphere.     

Does the Sun have a face?

We analyse the Greenwich sunspot data with methods using kinematic frames, which allow to detect and filter off any systematic motion, such as differential rotation, of the longitudinal activity traces. The aim is to check the recent claim of the existence of century-scale persistent solar active longitudes exhibiting antisolar differential rotation. As a result, we find no evidence for such features. Nevertheless, as is well known, the sunspot distribution is highly clustered in longitude (activity nests); the simple cell-counting statistics allows us to estimate the coherence time of these features, giving roughly10 Carrington rotations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Does ADS 9346 have a low-mass companion?

Based on the photographic and CCD observations of the relative motion of the A and B components of the binary system ADS 9346 obtained with the 26-inch refracto...     

Does the region of flare-energy release work as a vacuum-cleaner?

We aim to explore the unusual flare event which took place in the solar atmosphere on September 22, 2011 and propose its theoretical interpretation. We analyze the process of energy release in the twisted magnetic flux-rope associated with the event, assuming the excitation of anomalous resistivity of turbulent plasma in the rope, and solve numerically nonlinear two-dimensional (2D) magnetohydrodynamic (MHD) equations. The analytical approach to the problem of flare-energy release show that the conditions of excitation of anomalous resistivity can be satisfied in the twisted magnetic flux-rope whose parameters fits well the SDO observational findings. One of the most remarkable properties of the flare phenomenon under the present consideration was the permanent sucking of the coronal/chromospheric gas from the very remote points to the flare filament, i.e. into the low-lying hot region of the flare energy release. This unusual phenomenon has been simulated by numerical methods in terms of ideal MHD. The numerical results reveal that siphon back-flow exhibits characteristic spatial signatures which mimic the observational findings. The flare-energy release region, as a part of strongly twisted magnetic flux-rope, is able to work as a vacuum-cleaner.     

Does your robot need a flamethrower? Automated astronomical instrumentation in Antarctica

The Antarctic Plateau contains sites with the potential to be the best in the world for many astronomical observations. The Plateau has strong advantages in the waveband between thermal‐IR and millimetre‐waves, for time‐based astronomy, and for adaptive optics and interferometry. In such a harsh environment, automation of instrument functions becomes very important. At entirely remote (i.e., uncrewed) locations, automated instruments require robustness above all, especially in their self‐contained logistics functions (power and communications). At crewed stations, with human intervention available, automation should concentrate on increasing functionality and decreasing workload on the winterover scientists, enhancing the scientific return on a significant investment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Can GJ 876 host four planets in resonance?

Prior to the detection of its outermost Uranus-mass object, it had been suggested that GJ 876 could host an Earth-sized planet in a 15-day orbit. Observation, however, did not support this idea, but instead revealed evidence for the existence of a larger body in a ~125-day orbit, near a three-body resonance with the two giant planets of this system. In this paper, we present a detailed analysis of the dynamics of the four-planet system of GJ 876, and examine the possibility of the existence of other planetary objects interior to its outermost body. We have developed a numerical scheme that enables us to search the orbital parameter-space very effectively and, in a short time, identify regions where an object may be stable. We present details of this integration method and discuss its application to the GJ 876 four-planet system. The results of our initial analysis suggested possible stable orbits at regions exterior to the orbit of the outermost planet and also indicated that an island of stability may exist in and around the 15-day orbit. However, examining the long-term stability of an object in that region by direct integration revealed that the 15-day orbit becomes unstable and that the system of GJ 876 is most likely dynamically full. We present the results of our study and discuss their implications for the formation and final orbital architecture of this system.     

Does black hole spin play a key role in the FSRQ/BL Lac dichotomy?

Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The majority of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally,blazars can be divided into two classes: flat spectrum radio quasars(FSRQs) and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in γ-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in γ-ray luminosity between the two classes is significantly reduced. In order to explain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources.     

Does the solar magnetic field increase?

We consider measurements of the general magnetic field (GMF) of the Sun as a star at four world observatories from 1968 until 1999. We show that, within the error limits, the mean strength of the photospheric magnetic field H (of its longitudinal component, in magnitude) has not changed over the last 32 years. This is in conflict with the recent conclusion by Lockwood et al. (1999) that the solar coronal magnetic field increased by 40% from 1964 until 1996 and has almost doubled in the last 100 years. The causes of discrepancies in the results are discussed. At the same time, the GMF exhibits a natural 11-year variation associated with the solar cycle. The strength of the photospheric longitudinal magnetic field (in absolute value) averaged over 32 years is 0.46 G (at an rms GMF strength of 0.57 G). The mean GMF for all years of measurements had a south polarity: $\bar H = - 0.030 \pm 0.018 G$ . The difference from zero is statistically significant at 1.7σ (90%) and may be directly related to the outstanding problem of the solar magnetic “monopole.”     

Does Io have an ammonia atmosphere?

An atmosphere containing 0.5 cm atm of ammonia is assumed on Io. Such an atmosphere will be frozen at the unilluminated pole during the solstices, but will evaporate at the equinoctial seasons. The ammonia atmosphere will explain: (1) the posteclipse brightenings and their observed times of occurrence and nonocurrence; (2) the observed departure from a two-layer model beating curve upon emergence from eclipse; (3) the discordant temperatures obtained at 10 and 20 μm; and (4) discordant temperatures obtained at 10 and 20 μm during the total phase of an eclipse by Jupiter.In order to explain items 3 and 4 above, a proton flux in Jupiter's magnetosphere of 1.1 × 10⁹ cm^?2s^? at an energy of 0.5MeV at io's distance from Jupiter is assumed. This flux is 40 times the flux in Divine's (1972) “upper-limit” model of the Jovian radiation belts, while the proton energy is eight times less. The proton flux, plus the solar ultraviolet and infrared flux absorbed by the ammonia, will heat the atmosphere to 245 ± 10°K. At this temperature the occultation atmospheric upper limit allows the addition of 4 cmatm of nitrogen.     

The heptahydrate of sodium sulfate: Does it have a role in terrestrial and planetary geochemistry?

Sodium sulfate readily forms a metastable heptahydrate from concentrated aqueous solutions on cooling to around 10 °C. It crystallises much more easily than the well recognised and less soluble decahydrate (mirabilite), although the existence of the heptahydrate is almost entirely ignored in the geochemical literature on sodium sulfate. There is strong evidence that the heptahydrate is stable below a triple point temperature of −9.5 °C at low water vapour pressures, conditions which are found in cold dry environments such as the surface of Mars and the icy moons of Jupiter.     

Does the gravitational “constant” increase?

The possibility that the gravitational coupling constantG is an increasing function of the cosmic timet is discussed.In Section 1 the Maximal Power Hypothesis (MPH) stating that no power in Nature can exceed the upper boundc ⁵/G (Gunn's luminosity) is advocated.In Sections 2, 3, and 4 the MPH is employed on the cosmological scale to support the idea of an increasingG. In Section 2 the increasingG is obtained by two assumptions - the MPH and the energy conservation law - and by nothing else.In Section 3 the increasingG follows naturally from the MPH in the Einstein-Cartan theory of gravity. The arguments proposed in Sections 2 and 3 lead todG(t)/dt > 0 but cannot specify the form ofG(t). In Section 4 the MPH is applied to the energy of the vacuum and leads to a relation betweenG and the cosmological term,G S ³, valid in a matter-dominated universe (S =S(t) is the expansion factor). This relation plus the time-dependence law (suggested by many authors) t ² = constant, plustH > 2/3 (suggested by observations on the age of globular clusters;H is the Hubble parameter) implies an increasingG. One finds also GU, whereU is the mass density of the universe, in agreement with other studies.     

Accelerated expansion from?a?modified-quadratic gravity

We investigate the late-time dynamics of a four-dimensional universe based on modified scalar field gravity in which the standard Einstein-Hilbert action R is replaced by f(φ)R+f(R) where f(φ)=φ ² and f(R)=AR ²+BR _μν R ^μν,(A,B)∈ℝ. We discussed two independent cases: in the first model, the scalar field potential is quartic and for this special form it was shown that the universe is dominated by dark energy with equation of state parameter w≈−0.2 and is accelerated in time with a scale factor evolving like a(t)∝t ^5/3 and B+3A≈0.036. When, B+3A→∞ which corresponds for the purely quadratic theory, the scale factor evolves like a(t)∝t ^1/2 whereas when B+3A→0 which corresponds for the purely scalar tensor theory we found when a(t)∝t ^1.98. In the second model, we choose an exponential potential and we conjecture that the scalar curvature and the Hubble parameter vary respectively like R=hH[(f)\dot]/f,h ? \mathbbRR=\eta H\dot{\phi}/\phi,\eta\in\mathbb{R} and H=g[(f)\dot]^c,(g,c) ? \mathbbRH=\gamma\dot{\phi}^{\chi},(\gamma,\chi)\in\mathbb{R}. It was shown that for some special values of  χ, the universe is free from the initial singularity, accelerated in time, dominated by dark or phantom energy whereas the model is independent of the quadratic gravity corrections. Additional consequences are discussed.     

Does the speed of light decrease with time?

Rust (1974) stated that the classical (e.g., Doppler) explanations of the cosmological red shift contradict the results of astronomical observations of the period of changes in the brightness of supernovae. This paper is an attempt at explaining this discrepancy between observations and the theoretical predictions on the grounds of a hypothesis published by the author (Bellert, 1969). That hypothesis explains the cosmological red shift by the geometry of the space of events, which is a static space.We regret to report that, soon after the submission of this paper, Professor Bellert passed away on 27 March, 1976 in Warsaw.     

Does the Hubble redshift flip photons and gravitons?

Due to the Hubble redshift, photon energy, chiefly in the form of CMBR photons, is currently disappearing from the universe at the rate of nearly 10⁵⁵ erg s⁻¹. An ongoing problem in cosmology concerns the fate of this energy. In one interpretation it is irretrievably lost, i.e., energy is not conserved on the cosmic scale. Here we consider a different possibility which retains universal energy conservation. Treating gravitational potential energy conventionally as ‘negative’, it has earlier been proposed that the Hubble shift flips positive energy (photons) to negative energy (gravitons) and vice versa. The lost photon energy would thus be directed towards gravitation, making gravitational energy wells more negative. Conversely, within astrophysical bodies, the flipping of gravitons to photons would give rise to a ‘Hubble luminosity’ of magnitude −UH ₀, where U is the internal gravitational potential energy of the object. Preliminary evidence of such an energy release is presented in bodies ranging from planets, white dwarfs and neutron stars to supermassive black holes and the visible universe.     

Does the principle of special relativity really hold?

We start from a reference frame for which the pseudo-Euclidean geometry holds, i.e., all laws in have the form of special relativity. The geometry of a reference frame , moving with constant velocity with regard to , is received by using the well-known Galilei-transformation for the covariant space-time vector. In the geometry is different from the pseudo-Euclidean one, i.e., the principle of special relativity does not hold. The velocity of light in is direction dependent but the null result of the Michelson-Morley experiment is received. Several useful transformation formulae are given. In particular, we obtain the Marinov-transformation as transformation from the frame to , and conversely. Maxwell's equations and the equations of motion in the reference frame are given. The theory is applied to some examples, e.g., the Doppler effect, the Fizeau experiment, the field of a charged particle, etc. The method can be generalized to an accelerated reference frame .     

Does solar flare activity lag behind sunspot activity?

Recently, Wheatland and Litvinenko (2001) have suggested that over the solar cycle both the flaring rate and the magnetic free energy in the corona lag behind the energy supply to the system. To test this model result, we analyzed the evolution of solar flare occurrence with regard to sunspot numbers (as well as sunspot areas), using H flare data available for the period 1955–2002, and soft X-ray flare data (GOES 1–8 Å) for the period 1976–2002. For solar cycles 19, 21, and 23, we find a characteristic time lag between flare activity and sunspot activity in the range 1015 months, consistent with the model predictions by Wheatland and Litvinenko (2001). The phenomenon turns out to be more prominent for highly energetic flares. The investigation of solar activity separately for the northern and southern hemisphere allows us to exclude any bias due to overlapping effects from the activity of both hemispheres and confirms the dynamic relevance of the delay phenomenon. Yet, no characteristic time lag >0 is found for solar cycles 20 and 22. The finding that in odd-numbered cycles flare activity is statistically delayed with respect to sunspot activity, while in even-numbered cycles it is not, suggests a connection to the 22-year magnetic cycle of the Sun. Further insight into the connection to the 22-year magnetic cycle could possibly be gained when a 22-year variation in the energy supply rate is taken into account in the Wheatland and Litvinenko (2001) model. The existence of a 22-year modulation in the energy supply rate is suggested by the empirical Gnevyshev – Ohl rule, and might be caused by a relic solar field.     

Three-dimensional Separator Reconnection – How Does It Occur?

In two dimensions magnetic energy release takes place at locations where the magnetic field strength becomes zero and has an x-point topology. The x-point topology can collapse into two y-points connected by a current sheet when the advection of magnetic flux into the x-point is larger than the dissipation of magnetic flux at the x-point. In three dimensions magnetic fields may also contain singularities in the form of three-dimensional null points. Three-dimensional nulls are created in pairs and are therefore, at least in the initial stages, always connected by at least one field line – the separator. The separator line is defined by the intersection of the fan planes of the two nulls. In the plane perpendicular to a single separator the field line topology locally has a two dimensional x-point structure. Using a numerical approach we find that the collapse of the separator can be initiated at the two nulls by a velocity shear across the fan plane. It is found that for a current concentration to connect the two nulls along the separator, the current sheet can only obtain two different orientations relative to the field line structure of the nulls. The sheet has to have an orientation midway between the fan plane and the spine axis of each null. As part of this process the spine axes are found to lose their identity by transforming into an integrated part of the separator surfaces that divide space into four magnetically independent regions around the current sheet.     

Does the Babcock-Leighton mechanism operate on the Sun?

The contribution of the Babcock-Leighton mechanism to the generation of the Sun’s poloidal magnetic field is estimated from sunspot data for three solar cycles. Comparison of the derived quantities with the A-index of the large-scale magnetic field suggests a positive answer to the question posed in the title of this paper.