Solar Motion Research Articles

Thermally induced dynamics of deployable solar panels of nanosatellite

PurposeThis study aims to predict the types of thermally induced dynamics (TID) that can occur on deployable solar panels of a small form factor satellite, CubeSat which flies in low Earth orbit (LEO). The TID effect on the CubeSat body is examined.Design/methodology/approachA 3U CubeSat with four short-edge deployable solar panels is considered. Time historic temperature of the solar panels throughout the orbit is obtained using a thermal analysis software. The results are used in numerical simulation to find the structural response of the solar panel. Subsequently, the effect of solar panel motion on pointing the direction of the satellite is examined using inertia relief method.FindingsThe thermal snap motion could occur during eclipse transitions due to rapid temperature changes in solar panels’ cross-sections. In the case of asymmetric solar panel configuration, noticeable displacement in the pointing direction can be observed during the eclipse transitions.Research limitations/implicationsThis work only examines an LEO mission where the solar cells of the solar panels point to the Sun throughout the daylight period and point to the Earth while in shadow. Simplification is made to the CubeSat structure and some parameters in the space environment.Practical implicationsThe results from this work reveal several practical applications worthy of simplifying the study of TID on satellite appendages.Originality/valueThis work presents a computational method that fully uses finite element software to analyze TID phenomenon that can occur in LEO on a CubeSat which has commonly used deployable solar panels structure.

The kinematics of Galactic disc white dwarfs inGaiaDR2

We present an analysis of the kinematics of Galactic disc white dwarf stars in the Solar neighbourhood using data from Gaia Data Release 2. Selection of white dwarfs based on parallax provides the first large, kinematically unbiased sample of Solar neighbourhood white dwarfs to date. Various classical properties of the Solar neighbourhood kinematics have been detected for the first time in the WD population. The disc white dwarf population exhibits a correlation between absolute magnitude and mean age, which we exploit to obtain an independent estimate of the Solar motion with respect to the Local Standard of Rest. This is found to be $(U,V,W)_{\odot} = (9.5\pm1.2, 7.5\pm1.2, 8.2\pm1.2)$ kms$^{-1}$. The $UW$ components agree with studies based on main sequence stars, however the $V$ component differs and may be affected by systematics arising from metallicity gradients in the disc. The velocity ellipsoid is shown to vary strongly with magnitude, and exhibits a significant vertex deviation in the $UV$ plane of around 15 degrees, due to the non-axisymmetric Galactic potential. The results of this study provide an important input to proper motion surveys for white dwarfs, which require knowledge of the velocity distribution in order to correct for missing low velocity stars that are culled from the sample to reduce subdwarf contamination.

Climatological analysis of the seeing at Fuxian Solar Observatory

There is a significant seasonal variation in the seeing of Fuxian Solar Observatory (FSO). The seeing in summer and autumn is better than that in winter and spring. The overall seeing is divided into the boundary layer seeing and free atmosphere seeing to investigate the climatic phenomena or meteorological events that might lead to seasonal variation in the seeing. The overall seeing was measured by the solar difference image motion monitor (SDIMM). The boundary layer seeing is calculated from the temperature difference between air and water. The analysis results show that the seasonal variation in seeing is caused by the alternation of subtropical high and westerly jet. The decrease of seeing in winter and spring at FSO is probably related to the westerly jet. A complete analysis of the seeing at FSO is given in this paper. It is also the first time to describe FSO’s boundary layer seeing and its measurement method.

Development of Software that Supports Learning Solar Diurnal Motion from a Ground-level Perspective and its Effects

Development of Software that Supports Learning Solar Diurnal Motion from a Ground-level Perspective and its Effects

Probabilistic galactic dynamics – I. The Sun and GJ 710 with Monte Carlo, linearized, and unscented treatments

Deterministic galactic dynamics is impossible due to the space-time randomness caused by gravitational waves. Instead of treating stellar orbits deterministically, we integrate not only the mean but also the covariance of a stellar orbit in the Galaxy. As a test case we study the probabilistic dynamics of the Sun and the star GJ 710 which is expected to cross the Oort Cloud in 1.3 Myr. We find that the uncertainty in the galactic model and the Sun's initial conditions are important for understanding such stellar close encounters. Our study indicates significant uncertainty in the solar motion within 1 Gyr and casts doubt on claims of a strict periodic orbit. In order to make such calculations more practical we investigate the utility of the linearised and unscented transformations as two efficient schemes relative to a baseline of Monte Carlo calculations. We find that the linearised transformation predicts the uncertainty propagation as precisely as the Monte Carlo method for a few million years at least 700 times faster. Around an order of magnitude slower, the unscented transformation provides relative uncertainty propagation to a very high precision for tens of millions of years. There exist a variety of problems in galactic dynamics which require the propagation of the orbital uncertainty for more than one or two objects and the first order linearised transformation provides an efficient method which works to Gyr time scales for small initial uncertainty problems and for propagation over hundreds of million years for larger initial uncertainty problems.

Solar Tracker on Solar Home System to Optimize Sunlight Absorption

This study presents solar tracker in resolving optimization of solar panel to capture the sunlight on solar home system. The concept of this solar tracker development utilizing a parabolic actuator drive as a mechanical driver of solar panels. The mechanical solar panels adjusted to the needs of solar panel motion in order to obtain optimal sunlight. The mechanical motion of the solar tracker covering east to west to optimize sunrise to sunset and from north to south or vice versa as an opmization of the annual sun shifts. The study phase begins by designing the solar tracker, controller system design, development, testing, and analysis. Measurement data obtained by testing the results of development according by the performance of the system. After testing phase, the mounting of solar panel can follow the sunlight from all angles overall from sunrise to sunset and sun shift too. The result of the angle change of solar tracker for five days in average generate 507 watts per day while those not using solar tracker produces 403 watts per day and the use of the actuator for five days in average is 12.54 watts. The data usage of the solar tracker can optimize the capture of sunlight while the power consumption of the motor is quite small. The use of solar tracker can increase the optimal use of solar panels as a source of renewable energy.

Thermal Analysis of Satellite Libertad 2: a Guide to CubeSat Temperature Prediction

We present a model for predicting the temperature of three-unit CubeSat on a low Earth orbit, which supposes a single temperature common to all satellite components. Our exposition includes a detailed, to a large extent analytical, computation of the external heat fluxes for a particular orbit and spacecraft assumptions based on the features foreseen for satellite Libertad 2 under development at Universidad Sergio Arboleda. Moreover, supported by specialized thermal analysis software, we compute the heat fluxes and their associated temperature for all possible orbital orientations, and combine these results with a description of the satellite orbital plane rotation (nodal regression) and the solar motion on the ecliptic, to determine the minima and maxima of the orbital temperature oscillation for a mission lifetime of a year. We find that, for feasible model parameters, the temperature extremes are mostly within the operating temperature range of the most sensitive satellite component, 0 °C ≤ T ≤ 60 °C, suggesting mission viability. Finally, we discuss possible model improvements which would allow testing of satellite design upgrades. In this regard, it is worth noting that the calculation of the external heat fluxes here described can be carried over, almost unchanged, to a more accurate model describing heat transfer between satellite parts with different temperatures.

The spiral potential of the Milky Way

Context. The location of young sources in the Galaxy suggests a four-armed spiral structure, whereas tangential points of spiral arms observed in the integrated light at infrared and radio wavelengths indicate that only two arms are massive. Aims. Variable extinction in the Galactic plane and high light-to-mass ratios of young sources make it difficult to judge the total mass associated with the arms outlined by such tracers. The current objective is to estimate the mass associated with the Sagittarius arm by means of the kinematics of the stars across it. Methods. Spectra of 1726 candidate B- and A-type stars within 3◦ of the Galactic center (GC) were obtained with the FLAMES instrument at the VLT with a resolution of ≈6000 in the spectral range of 396–457 nm. Radial velocities were derived by least-squares fits of the spectra to synthetic ones. The final sample was limited to 1507 stars with either Gaia DR2 parallaxes or main-sequence B-type stars having reliable spectroscopic distances. Results. The solar peculiar motion in the direction of the GC relative to the local standard of rest (LSR) was estimated to U⊙ = 10.7 ± 1.3kms−1. The variation in the median radial velocity relative to the LSR as a function of distance from the sun shows a gradual increase from slightly negative values near the sun to almost 5 km s−1 at a distance of around 4 kpc. A sinusoidal function with an amplitude of 3.4 ± 1.3kms−1 and a maximum at 4.0 ± 0.6 kpc inside the sun is the best fit to the data. A positive median radial velocity relative to the LSR around 1.8 kpc, the expected distance to the Sagittarius arm, can be excluded at a 99% level of confidence. A marginal peak detected at this distance may be associated with stellar streams in the star-forming regions, but it is too narrow to be associated with a major arm feature. Conclusions. A comparison with test-particle simulations in a fixed galactic potential with an imposed spiral pattern shows the best agreement with a two-armed spiral potential having the Scutum–Crux arm as the next major inner arm. A relative radial forcing dFr ≈ 1.5% and a pattern speed in the range of 20–30 km s−1 kpc−1 yield the best fit. The lack of a positive velocity perturbation in the region around the Sagittarius arm excludes it from being a major arm. Thus, the main spiral potential of the Galaxy is two-armed, while the Sagittarius arm is an inter-arm feature with only a small mass perturbation associated with it.

Constraining the Solar Galactic Reflex Velocity using Gaia Observations of the Sagittarius Stream

Abstract Because of its particular orientation around the Galaxy—i.e., in a plane nearly perpendicular to the Galactic plane and containing both the Sun and Galactic center—the Sagittarius (Sgr) stream provides a powerful means by which to measure the solar reflex velocity, and thereby infer the velocity of the Local Standard of Rest (LSR), in a way that is independent of assumptions about the solar Galactocentric distance. Moreover, the solar reflex velocity with respect to the stream is projected almost entirely into the proper motion component of Sgr stream stars perpendicular to the Sgr plane, which makes the inferred velocity relatively immune to most Sgr model assumptions. Using Gaia Data Release 2 proper motions of ∼2000 stars identified to be Sgr stream candidates in concert with the Law & Majewski Sgr N-body models (which provide a good match to the Gaia observations), we constrain the solar reflex velocity induced by its orbital motion around the Galaxy to be Θ⊙ = 253 ± 6 km s−1. Assuming a solar peculiar motion in the direction of orbital rotation of 12 km s−1, and an LSR velocity of 12 km s−1 with respect to the local circular speed, the implied circular speed of the Milky Way at the solar circle is 229 ± 6 km s−1.

The Nearest Extreme-velocity Stars among Gaia DR2 High-proper-motion Stars

Among about 1.8 million Gaia DR2 high proper motion stars with $\mu>60$ mas/yr and moderately significant parallaxes ($\varpi>3\sigma_{\varpi}$), we have selected 109 high-speed star candidates with Galactic rest frame tangential velocities (corrected for solar motion) $v_{t,g}$$>$700 km/s, well above the local Galactic escape velocity. After applying various Gaia DR2 astrometric quality criteria, only 39 candidates remained, including all three hypervelocity runaway white dwarfs (HVR WDs) found by Shen et al. (2018) but no additional such candidates (falling in the same region of the colour-magnitude diagram). Considering only candidates with highly significant parallaxes ($\varpi>5\sigma_{\varpi}$) as reliable extreme tangential velocity candidates (cf. Bromley et al. 2018), our final list consists of six objects with parallaxes of 0.17 mas $\lesssim \varpi \lesssim$ 1.05 mas and tangential velocities of 730 km/s $\lesssim v_{t,g} \lesssim$ 1600 km/s, including two candidates of Bromley et al. (2018). Only one of the three HVR WDs of Shen et al. (2018), D6-2 (= NLTT 51732), falls in that list but can be considered a doubtful high-speed candidate because of its relatively large astrometric quality parameters. One of the three new extreme velocity candidates in our list, Gaia DR2 6097052289696317952, is relatively bright ($G\approx$13.5 mag) and blue $BP$$-$$RP$$\approx$0.6 mag and has the smallest parallax and highest tangential velocity. Radial velocity measurements are needed to clarify whether these high-speed candidates are unbound to the Galaxy.

Origami system for efficient solar driven distillation in emergency water supply

Facing lack of infrastructure and no access of electricity, insuring drinking water for people during an emergency in remote area is becoming a great challenge. Here, we develop an origami as photothermal material based on daily pencil and paper for solar driven water purification in emergency. The drawn process destroyed the Van der Waals’ force between graphite layers, making pencil cartridge exfoliated into thin graphite sheets. The paper fibers combined with graphite sheets were demonstrated with broadband absorption for solar energy harvesting and excellent hydrophilicity for water transportation. The origami structure effectively promoted the utilization of solar energy attributing to the increased solar absorption area and decreased solar reflection loss compared with planar system. In particular, the solar vapor efficiency and vapor evaporation rate of as-prepared origami system were reached to 80% and 1.16 kg m−2 h−1, respectively. In addition, the analog calculation results of COMSOL Multiphysics indicated that the origami structure was free from the dynamic solar motion. Herein, this nearly free cost, facile fabricated and high efficiency design would unlock a new generation of efficient water purification for water supply in emergency.

Models of solar and lunar motions in the Chinese Chongxiu-Daming calendar

The Chongxiu-Damingli (Revised Great Enlightenment Calendar) of the Jin dynasty (A.D. 1115–1234) was developed in 1171 and used until 1280 in China. It had also been used since the reign of King Sejong (A.D. 1418–1450) in Korea to supplement calculations of the eclipse times. In this study, we investigate solar and lunar motions in this calendar. Referring to the Garyeong (Example Supplement for the Calculations of Solar and Lunar Eclipses Occurred in 1447) preserved in Korea, we first investigate sunrise and sunset times by the Chongxiu-Damingli to estimate the observation sites of these times. We then analyze the calculation methods of solar and lunar motions and of the maximum eclipse time using the calendar. We find that a cubic equation was utilized to calculate sunrise and sunset times. Compared with the results of modern calculations, we also find that the sunrise and sunset times are more suitable at Kaifeng (capital of the Northern Song dynasty) than Beijing (capital of the Jin dynasty). This finding confirms the record of the Jinshi (History of the Jin Dynasty) that the Chongxiu-Damingli was made based on the calendar of the Northern Song dynasty. Regarding solar and lunar motions, we find that the mean absolute difference values between the Chongxiu-Damingli and modern calculations are ∼0.005 and ∼0.145 degrees, respectively. Lastly, we find that the difference in the time of maximum solar eclipse that occurred on 1447 September 10 in Seoul (capital of the Joseon dynasty) is approximately 1 min between the calendar and modern calculation. We believe that this study will contribute to understanding the Chongxiu-Damingli and comparing the accuracy with other Chinese calendars such as the Shoushili.

A kinematical age for the interstellar object 1I/’Oumuamua

1I/'Oumuamua is the first interstellar object observed passing through the Solar System. Understanding the nature of these objects will provide crucial information about the formation and evolution of planetary systems, and the chemodynamical evolution of the Galaxy as a whole. We obtained the galactic orbital parameters of this object, considering 8 different models for the Galaxy, and compared it to those of stars of different ages from the Geneva-Copenhagen Survey (GCS). Assuming that the galactic orbital evolution of this object is similar to that of stars, we applied a Bayesian analyses and used the distribution of stellar velocities, as a function of age, to obtain a probability density function for the age of 'Oumuamua. We considered two models for the age-velocity dispersion relation (AVR): the traditional power law, fitted using data from the GCS; and a model that implements a second power law for younger ages, which we fitted using a sample of 153 Open Clusters (OCs). We find that the slope of the AVR is smaller for OCs than it is for field stars. Using these AVRs, we constrained an age range of 0.01-1.87 Gyr for 'Oumuamua and characterized a most likely age ranging between 0.20-0.45 Gyr, depending on the model used for the AVR. We also estimated the intrinsic uncertainties of the method due to not knowing the exact value of the Solar motion and the particularities of 1I/'Oumuamua's ejection.

A VLBI Distance and Transverse Velocity for PSR B1913+16

Abstract Using the Very Long Baseline Array, we have made astrometric observations of the binary pulsar B1913+16 spanning an 18-month period in 2014–2015. From these observations we make the first determination of the annual geometric parallax of B1913+16, measuring mas (68% confidence interval). The inferred parallax probability distribution differs significantly from a Gaussian. Using our parallax measurement and prior information on the spatial and luminosity distributions of the millisecond pulsar population, we infer a distance of kpc, which is significantly closer than the 9.8 ± 3.1 kpc suggested by the pulsar’s dispersion measure (DM) and analyses of the ionized interstellar medium. While the relatively low significance of the parallax detection (∼3σ) currently precludes an improved test of general relativity using the orbital decay of PSR B1913+16, ongoing observations with improved control of systematic astrometric errors could reach the 10% distance uncertainty required for this goal. The proper motion measured by our Very Long Baseline Interferometry astrometry differs substantially from that obtained by pulsar timing, a discrepancy that has also been found between the proper motion measurements made by interferometers and pulsar timing for some other pulsars, which we speculate is the result of timing noise or DM variations in the timing data set. Our parallax and proper motion measurements yield a transverse velocity of km s−1 in the solar reference frame. Analysis incorporating galactic rotation and solar motion finds that the space velocity of the pulsar relative to its standard of rest has a component km s−1 perpendicular to the galactic plane and components on the order of 100 km s−1 parallel to the galactic plane.

The local rotation curve of the Milky Way based on SEGUE and RAVE data

Aims. We construct the rotation curve of the Milky Way in the extended solar neighbourhood using a sample of Sloan Extension for Galactic Understanding and Exploration (SEGUE) G-dwarfs. We investigate the rotation curve shape for the presence of any peculiarities just outside the solar radius as has been reported by some authors. Methods. Using the modified Strömberg relation and the most recent data from the RAdial Velocity Experiment (RAVE), we determine the solar peculiar velocity and the radial scale lengths for the three populations of different metallicities representing the Galactic thin disc. Subsequently, with the same binning in metallicity for the SEGUE G-dwarfs, we construct the rotation curve for a range of Galactocentric distances from 7 to 10 kpc. We approach this problem in a framework of classical Jeans analysis and derive the circular velocity by correcting the mean tangential velocity for the asymmetric drift in each distance bin. With SEGUE data we also calculate the radial scale length of the thick disc taking as known the derived peculiar motion of the Sun and the slope of the rotation curve. Results. The tangential component of the solar peculiar velocity is found to be V ⊙ = 4.47 ± 0.8 km s−1 and the corresponding scale lengths from the RAVE data are Rd(0 < [Fe/H] < 0.2) = 2.07 ± 0.2 kpc, Rd(−0.2 < [Fe/H] < 0) = 2.28 ± 0.26 kpc and Rd(−0.5 < [Fe/H] <−0.2) = 3.05 ± 0.43 kpc. In terms of the asymmetric drift, the thin disc SEGUE stars are demonstrated to have dynamics similar to the thin disc RAVE stars, therefore the scale lengths calculated from the SEGUE sample have close values: Rd(0 < [Fe/H] < 0.2) = 1.91 ± 0.23 kpc, Rd(−0.2 < [Fe/H] < 0) = 2.51 ± 0.25 kpc and Rd(−0.5 < [Fe/H] <−0.2) = 3.55 ± 0.42 kpc. The rotation curve constructed through SEGUE G-dwarfs appears to be smooth in the selected radial range 7 kpc < R < 10 kpc. The inferred power law index of the rotation curve is 0.033 ± 0.034, which corresponds to a local slope of dV c∕dR = 0.98 ± 1 km s−1 kpc−1. The radial scale length of the thick disc is 2.05 kpc with no essential dependence on metallicity. Conclusions. The local kinematics of the thin disc rotation as determined in the framework of our new careful analysis does not favour the presence of a massive overdensity ring just outside the solar radius. We also find values for solar peculiar motion, radial scale lengths of thick disc, and three thin disc populations of different metallicities as a side result of this work.

A Focus on L Dwarfs with Trigonometric Parallaxes

We report new parallax measurements for 10 L- and early T-type dwarfs, five of which have no previous published values, using observations over 3 years at the robotic Liverpool Telescope. The resulting parallaxes and proper motions have median errors of 2 mas and 1.5 mas/year, respectively. Their space motions indicate they are all Galactic disk members. We combined this sample with other objects with astrometry from the Liverpool Telescope and with the published literature astrometry to construct a sample of 260 L- and early T type dwarfs with measured parallaxes, designated the Astrometry Sample. We study the kinematics of the Astrometry Sample, and derived a solar motion of (U, V, W)⊙ = (7.9 ± 1.7, 13.2 ± 1.2, 7.2 ± 1.0) km s−1, with respect to the local standard of rest, in agreement with the recent literature. We derive a kinematic age of 1.5–1.7 Gyr for the Astrometry Sample assuming the age increases monotonically with the total velocity for a given disk sample. This kinematic age is less than half of the literature values for which used the same methods and similar but different low-mass dwarf samples. We believe this difference arises for two reasons: (1) the sample is mainly composed of mid to late L dwarfs, which are expected to be relatively young, and (2) the requirement that objects have a measured parallax biases the sample to the brighter examples, which tend to be younger.

Dark Matter Directional Detection with MIMAC

The MIMAC (MIcro-tpc MAtrix of Chambers) experiment is a micro-TPC matrix for directional dark matter search. Directional detection is a strategy based on the measurement of the WIMP flux anisotropy due to the solar system motion with respect to the dark matter halo. The main purpose of MIMAC project is the measurement of nuclear recoils energy and their 3D track direction from the WIMP elastic scattering on target nuclei. The first ionization energy and 3D track observations of nuclear recoils produced by the radon progeny recently reported being shown. This measurement shows the capability of the MIMAC detector and opens the possibility to explore the low energy recoil directionality signature. The measurement of the drift velocity from an implementation of the cathode signal is also mentioned.

Stability and self-organization of planetary systems.

We show that stability of planetary systems is intimately connected with their internal order. An arbitrary initial distribution of planets is susceptible to catastrophic events in which planets either collide or are ejected from the planetary system. These instabilities are a fundamental consequence of chaotic dynamics and of Arnold diffusion characteristic of many body gravitational interactions. To ensure stability over astronomical time scale of a realistic planetary system-in which planets have masses comparable to those of planets in the solar system-the motion must be quasiperiodic. A dynamical mechanism is proposed which naturally evolves a planetary system to a quasiperiodic state from an arbitrary initial condition. A planetary self-organization predicted by the theory is similar to the one found in our solar system.

Method of composing two-dimensional scanned spectra observed by the New Vacuum Solar Telescope

In this paper we illustrate the technique used by the New Vacuum Solar Telescope (NVST) to increase the spatial resolution of two-dimensional (2D) solar spectroscopy observations involving two dimensions of space and one of wavelength. Without an image stabilizer at the NVST, large scale wobble motion is present during the spatial scanning, whose instantaneous amplitude can reach 1.3″ due to the Earth’s atmosphere and the precision of the telescope guiding system, and seriously decreases the spatial resolution of 2D spatial maps composed with scanned spectra. We make the following effort to resolve this problem: the imaging system (e.g., the TiO-band) is used to record and detect the displacement vectors of solar image motion during the raster scan, in both the slit and scanning directions. The spectral data (e.g., the Hα line) which are originally obtained in time sequence are corrected and re-arranged in space according to those displacement vectors. Raster scans are carried out in several active regions with different seeing conditions (two rasters are illustrated in this paper). Given a certain spatial sampling and temporal resolution, the spatial resolution of the composed 2D map could be close to that of the slit-jaw image. The resulting quality after correction is quantitatively evaluated with two methods. A physical quantity, such as the line-of-sight velocities in multiple layers of the solar atmosphere, is also inferred from the re-arranged spectrum, demonstrating the advantage of this technique.

Long-term cyclicities in Phanerozoic sea-level sedimentary record and their potential drivers

Abstract Cyclic sedimentation has varied at several timescales and this variability has been geologically well documented at Milankovitch timescales, controlled in part by climatically (insolation) driven sea-level changes. At the longer (tens of Myr) timescales connection between astronomical parameters and sedimentation via cyclic solar-system motions within the Milky Way has also been proposed, but this hypothesis remains controversial because of the lack of long geological records. In addition, the absence of a meaningful physical mechanism that could explain the connection between climate and astronomy at these longer timescales led to the more plausible explanation of plate motions as the main driver of climate and sedimentation through changes in ocean and continent mass distribution on Earth. Here we statistically show a prominent and persistent ~36 Myr sedimentary cyclicity superimposed on two megacycles (~250 Myr) in a relatively well-constrained sea-level (SL) record of the past 542 Myr (Phanerozoic eon). We also show two other significant ~9.3 and ~91 Myr periodicities, but with lower amplitudes. The ~9.3 Myr cyclicity was previously attributed to long-period Milankovitch band based on the Cenozoic record. However, the ~91 Myr cyclicity has never been observed before in the geologic record. The ~250 Myr cyclicity was attributed to the Wilson tectonic (supercontinent) cycle. The ~36 Myr periodicity, also detected for the first time in SL record, has previously been ascribed either to tectonics or to astronomical cyclicity. Given the possible link between amplitudes of the ~36 and ~250 Myr cyclicities in SL record and the potential that these periodicities fall into the frequency band of solar system motions, we suggest an astronomical origin, and model these periodicities as originating from the path of the solar system in the Milky Way as vertical and radial periods that modulate the flux of cosmic rays on Earth. Our finding of the ~36 Myr SL cyclicity lends credibility to the existing hypothesis about the imprint of solar-system vertical period on the geological record. The ~250 Myr megacycles are tentatively attributed to a radial period. However, tectonic causal mechanisms remain equally plausible. The potential existence of a correlation between the modeled astronomical signal and the geological record may offer an indirect proxy to understand the structure and history of the Milky Way by providing a 542 Myr long record of the path of the Sun in our Galaxy.