Java application for superposition T-matrix code to study the optical properties of cosmic dust aggregates

Abstract

In this paper, we report the development of a java application for Superposition T-matrix code, JaSTA (Java Superposition T-matrix App), to study the light scattering properties of aggregate structures. It has been developed using Netbeans 7.1.2, which is a java integrated development environment (IDE). The JaSTA uses double precession superposition codes for multi-sphere clusters in random orientation developed by Mackowski & Mischenko (1996). It consists of a Graphical User Interface (GUI) in the front hand and a database of related data’s in the back hand. Both the interactive GUI and database package directly enables user to model by self-monitoring respective input parameters (namely, wavelength, complex refractive indices, grain size, etc.) to study the related optical properties of cosmic dust (namely, extinction, polarization, etc.) instantly, i.e., with zero computational time. This increases the efficiency of the user. The database of JaSTA is now created for a few sets of input parameters with a plan to create a large database in future. This application also has an option where users can compile and run the scattering code directly for aggregates in GUI environment. The JaSTA aims to provide convenient and quicker data analysis of the optical properties which can be used in different fields like planetary science, atmospheric science, nano science, etc. The current version of this software is developed for Linux and Windows platform to study the light scattering properties of small aggregates which will be extended for larger aggregates using parallel codes in future.

Authors : Prithish Halder, Arindwam Chakraborty, Parijat Deb Roy, Himadri Sekhar Das

Link to Published Paper : http://www.sciencedirect.com/science/article/pii/S0010465514001532

Link to download JaSTA : http://ausastro.in/jasta.html

Java application for the superposition T-matrix code to study the optical properties of cosmic dust aggrega...

Discrepency in Kepler Mission

The Kepler mission from Nasa is the most modern technique for the hunt of Earth like planets. Till today thousands of planets are discovered and this discovery is still going on. The kepler satellite that was launched 2 years ago, scans a particular portion of the sky with high precision and captures the pixels on a high quality CCD. The pixel data recorded on the CCD is then transfered to Earth in the Nasa Laboratories. The main trick behind finding a planet from the data returned by Kepler is to look for stars that blink periodically on the CCD. From this periodicity we can determine the radial velocity and distance of the planet from the star. Again the blinking of the star provide us the drop of brightness during the blink or the transit. The drop of brightness, radial velocity, planet distance from the star and the star type help us to determine the surface temperature of the planet. 

                             The proper values will yield a planet that is in the habitable zone and also earth like. But these studies are only for the stars whose plane of rotation is perpendicular to the field of view of the Kepler Telescope. It cannot be used for the stars whose plane of rotation is in the field of view of the telescope. I want to know the perfect parameter that can be used to detect a planet for the stars with rotational plane in the field of view. This is the only discrepancy in this mission. I hope sooner or later this will also be erased.

HIGGS BOSON ( The God Particle)

Journey To The Center Of The Milky Way

Can Stars Reside Outside a Galaxy ?

We all know that stars originate and die in Galaxies. The Galactic motion plays a vital role in star formation. But can stars reside outside a Galaxy? This was our question. The fateful answer is YES. There are many stars which reside in the space between the galaxies. Though there number is small but still they exist. We can compare galaxies with parents and stars with the sons or daughters of the respective parents. Thus we can say that the stars which are found outside the galaxies are lost from there parent galaxies. Or they are orphan stars. But how did these stars become Orphan? 

Now there are two possibilities:

1. There might have been collision between galaxies which left the stars alone.

2. The Stars might have come in contact with Black Holes which threw them out   of there parent galaxies.

Now both the possibilities stated above have respective conditions. If we find stars lying alone in the space very far away from a galaxy then this might be due to galactic collisions. Again if we find few stars outside a nearby galaxy then this might be due to Black Hole interaction.

We all basically know what can happen during Galactic Collision. This can be understood if one has basic idea of Physics Of collisions. Simple mechanics. But how can a Black Hole send a star out of the galaxy. This point is puzzling. 

We all know about Binary stars. For nerds its just a system of two stars which are Gravitationally held by there mutual gravitational attraction. When a Binary system come closer to a black hole (Very fast spinning) one of the star of the binary system comes in contact of the accretion disk of the Black Hole and suddenly experiences very high spinning motion and this in turn exerts a very high  force on the other star which is gravitationally held. The Spinning action or force is very very high compared to the mutual gravitational pull of the Binary and as the spinning motion is outward the other star attains a very high momentum and starts to move very fast and hence sometimes there high speed motion takes them out of the galaxy. 

For the first time in the year 1997 Astronomers found intergalactic stars in the Virgo cluster which is thought to be due to galactic collision. 

Again astronomers in the year 2005 found a star HE 0437-5439 which is massive, unbound and moving with a very high velocity (hypervelocity) about 723 km/s. This is thought to be due to the interaction of a binary system or a Triple star system with the huge Black Hole situated in the center of our Milky Way Galaxy. Like this there are many stars whose fate is decided by some accident. 

Every night we look into the sky full of twinkling Stars, dazzling our mind. The wonderful sparkling night sky is due to the formation of discrete set of stars from the intersteller molecular clouds or dusts.The fight between the inward gravitational force and the outward pressure force decides the fate of a star. Gravity brings the particles in the molecular clouds closer while the pressure waves radiated from the random agregation of the particles, tend to oppose the gravity. The balance between the two forces creates a protostar which is said to be in Hydrostatic Equilibrium.

Protostar is fully opaque and hence trasfer of energy via radiation is impossible. Thus energy is trasfered outward via convection and the protostar is said to be in convective equilibrium.

The convective equilibrium time period is fully dependent on the mass of the protostellar object. More the mass, less will be the time spent in convective equilibrium. Gravitaion still continue to contract the protostar. During this contraction a radiative core starts to develop. And as the radiative core grows enough to push the convective layer outward or throw it out of the protostar the protostar is said complete its pre- main sequence evolution. After this stage the star still continue to contract and increase its internal temperature. When the internal temperature becomes high enough to ignite the Hydrogen a thermo nuclear reaction or burning of hydrogen begins. At this stage radiation carries the energy outward and thus balancing the inward pull of the gravity. For the first time the star is said to attain an equilibrium between the two forces. The protostar settles in the Main sequence of the HR diagram and becomes a STAR. This way Stars are formed.

Is Dark Matter Composed Of Neutrinos .....????

People who love Astrophysics are always fantasized by the word "DARK MATTER". During a class on Astrophysics earlier this week, Dr. Asoke K. Sen of Assam University, Department Of Physics was trying to derive the mass of our Galaxy. Where he showed how theoretical and practical values collide with each other. The various Doppler shift observations of different galaxies show a missing mass problem. As if there is an unknown mass in the dark halo of the Galaxies. This mass was unable to interact with electro-magnetic force. He also told that dark matter may be composed of non-baryonic particles. Now the question is what are these non-baryonic particles which do not interact with electromagnetic forces but creating enough gravitational forces to shift the galaxies away from each other?

We who are related with physics, know about the mechanism of Beta Decay. In this a neutron decays to emit a proton and an electron. But in this decay there was an observed difference between energy,momentum and angular momentum of the initial and final particles.In order to balance the equation of beta decay in all respects. Then Enrico Fermi introduced a hypothetical particle called "neutrino" in the year 1933 which must emit along with a proton and an electron in Beta Decay. Then in the year 1970 the first neutrinos were practically detected in a Hydrogen Bubble chamber experiment proving the existence of neutrinos. Physicists obtained various characteristics of neutrino. A neutrino is electrically neutral, weakly interacting sub-atomic particle with half spin, chirality and a disputed but small non-zero mass. It is able to pass through ordinary matter uneffected. Neutrinos do not interact with electromagnetic forces. They are only affected by weak sub-atomic force of very short range and gravity. Our Sun emit 65 billion neutrinos every second in every square centimeter in each direction. Similarly all stars in our galaxies emit such huge amount of neutrinos each second. We have known almost all the properties of neutrinos. We know some properties of Dark Matter which seems to match with those of neutrinos.

So are these Neutrinos the Dark Matter particles? Or they are something else that we still do not know.