Six of the Solar System planets have 150 confirmed moons (Earth � 1, Mars � 2, Jupiter � 53, Saturn � 53, Uranus � 27, Neptune � 14) and 7 of them (Ganymede, Titan, Callisto, Io, Moon, Europa, Triton) have masses > 0.001M ? . But, no exomoons have been discovered yet despite the successful detection of 5000 exoplanets. We can infer, based on the Solar System planets, that these exoplanets are capable of hosting one or multiple exomoons. In this paper, we study the possible existence of hypothetical Earth-mass and Luna-mass moons orbiting the Jupiter-mass planet, Laligurans (HD 100777b) in the Sagarmatha (HD 100777) star system by means of orbital stability. We apply long-term orbital integrations and MEGNO (Mean Exponential Growth of Nearby Orbits) chaos indicator to study the orbital stability of the moons and predict a phase-space region comprising of periodic, chaotic, and unstable orbits. The phase-spaces primarily constitute the moon�s semimajor axis which extends from host planet�s Roche radius to the Hill radius, and full range of eccentricity. Specific points are picked from three different regions of MEGNO map and run as single-orbit integration for up to 10 billion period of innermost orbit. Furthermore, the lifetime and maximum eccentricity maps are generated from the direct integration to inspect the stable and unstable orbital configurations. The analyses of these maps, with the aid of time series plots, show that both moons maintain stable orbits in the low eccentricity regime and semimajor axis between the Roche limit and 28.4% of Hill radius of the planet.

Classical Cepheids are excellent tracers to estimate the rotation velocity of the galaxies because they provide better distance accuracy with less uncertainty. But, due to the less budget of radial velocity in spectroscopic surveys, still, we could not compile a large catalog of them with 6D phase-space. With stringent radial velocity from OGLE DR3 and proper motion from Gaia EDR3, we estimate the rotation velocity of the Milky Way for number of Classical Cepheids taken from the catalog of Mroz et al: (2019) with precise distance. We present a 3D velocity method to measure rotation velocity up to 20 kpc where we draw 6D phase-space coordinates with high precision even we have fewer samples. We obtain rotation velocity of 243:38 km/s � 0:00 km/s.

We study a sample of compact star-forming dwarf galaxies that are selected from a merging dwarf galaxy catalog. We present a detailed study of their morphological and structural properties. We find that these BCDs-looking galaxies host extended stellar shells and thus are confirmed to be a dwarf-dwarf merger. Their stellar masses range between 8�10^7 M_? and 2�10^9 M_?. Although the extended tail and shell are prominent in the deep optical images, the overall major axis light profile is well modeled with a two-component Sersic function of inner compact and extended outer radii. We calculate the inner and outer component stellar-mass ratio using the two-component modeling. We find an average of merger ratio 1:10 for our sample, indicating these galaxies might have suffered a satellite accretion, which triggers the starburst in the center of the host galaxies. From the measurement of H? equivalent width, we derived the star-formation ages of these galaxies. The derived star-formation ages of these galaxies turn out to be less than 100 M_? yr-1, suggesting the recent ignition of star-formation due to events of satellite interaction. Key Words: Blue Compact Dwarf Galaxy, Galaxy Merger, Star Burst, Sersic Modelling.

During the asymptotic giant branch (AGB) phase, a major fraction of mass is spread by the stars (0.6 - 10 M{$\odot$}) in the interstellar medium (ISM) in the form of dust. In the left phase of Post-Main Sequence evolution, these dust are found to be surrounding the White Dwarfs (WD). Some small fraction of dust is also formed in the circumstellar shells and cavities around WD which is usually a source of infrared (IR) excess. Formation and evolution of such IR dust structures are the results of high pressure events and such structures are crucial in the study of interaction phenomena in ISM. This research project is focused on the study of an isolated dust structure near the white dwarf WD0011-399 located at R.A. (J2000) 00$^h$ 13$^m$ 47.48$^s$ and Dec. (J2000) -39$^{\circ}$ 37$^{'}$ 24.28$^{''}$ using Improved Reprocessing of the IRAS (IRIS), AKARI and Wide-field Infrared Survey Explorer (WISE) surveys from SkyView Virtual Observatory along with SIMBAD Astronomical Database and Gaia Archive of ESA. The size of the cavity under study is 5.42 pc$\times$2.75 pc, 1.87pc$\times$0.87pc and 1.03$\times$0.51pc with inclination angle of 62.32$^{\circ}$, 65.57$^{\circ}$ and 62.27$^{\circ}$ respectively in IRIS, AKARI and WISE data suggesting that the cavity is neither a face-on nor an edge-on. The relative flux density of the region has been studied through pixel extraction of FIR images (0.5$^{\circ}$, 30 pixels) and dust color temperature along with dust mass has been calculated. Using IRIS data the temperature of the whole region is found between a maximum value 36.82$\pm$4.30 K to a minimum 22.59$\pm$2.32 K with an offset 14.23 K. The average temperature of the region is 28.22$\pm$0.18 K. Following similar procedures for AKARI data, the temperature is found between a maximum of 26.37$\pm$3.56 K and a minimum of 16.32$\pm$1.47 K with an offset of 10.06K. The average temperature is 19.25$\pm$0.15 K. Similarly, using WISE data, the temperature is found between a maximum of 353.72$\pm$18.54 K and a minimum of 307.24$\pm$4.69 K with an offset of 46.48K. The average temperature is 316.62$\pm$0.81 K. High value of offset temperature suggests that the cavity might be evolving with disruptions from background radiative sources. Approximately Gaussian distribution of the temperature in all the surveys implies that the region might be tending towards local thermodynamic equilibrium. The total mass of the structure is estimated to be around 0.03M$_\odot$, 1.6$\times$10$^{-3}$M$_\odot$ and 10$^{-7}$M$_\odot$ using IRIS, AKARI and WISE data respectively. The Jean's mass of the structure was calculated assuming the structure as non-degenerate gas, which was estimated around 2001.93M$_\odot$, 178.44M$_\odot$ and 121.47M$_\odot$ using IRIS, AKARI and WISE data. Since Jean's mass is much greater than the mass of the structure there seems no possibility of star formation within the region of interest. The color maps show identical distribution for all wavelengths however, no significant relation was observed between dust color temperature and dust mass.

In this work, dust properties around the White Dwarf PG 1225-079 located at RA (J2000): 12h 27m 47.35s, DEC(J2000): -08o 14' 37.97" is studied extensively using the publicly available data from Improved Reprocessing of IRAS Survey (IRIS), AKARI infrared survey and Wide-field Infrared Survey Explorer (WISE). The bipolar dust structure, hardly resolved in IRIS (60 ?m and 100 ?m), is clearly resolved in AKARI (90 ?m and 140 ?m) and WISE (12 ?m and 22 ?m) image. The dust color temperature and dust mass are calculated from infrared flux density in each bipolar dust structures in all surveys. In IRIS data the average value of dust color temperature in isolated dust structure is 27.57 K. The bipolar isolated upper and lower dust cloud have average temperature; 22.64 K and 22.63 K in AKARI data and 295.34 K and 296.85 K in WISE data respectively. The wide range of temperature suggests the bipolar dust structure is dynamically active. The mass of dust are found to be 6.53�1024 kg in IRIS data, 1.66�1026 kg and 5.60�1026 kg in two bipolar region in AKARI data and 5.48�1025kg and 6.32�1025kg in WISE data. A good correlation is found between the infrared fluxes in all survey with r2value 0.83 in IRIS and more than 0.90 in AKARI and WISE data. SIMBAD database explored few sources including Supernova Remnants nearby the bipolar dust, which might be the progenitor of dust as well as the contributor of energetic radiation. The Gaussian modeling of temperature is found to be distributed Normally. The contour plot of dust color temperature and dust mass shows non-uniform variation among IRIS, AKARI and WISE survey. We have tried to establish the relation between temperature and mass using linear regression. Keywords: White Dwarf, IRIS, AKARI, WISE, PG 1225-079, Temperature-Mass