Tag Archives: Neutron

First observation of merger of two neutron stars

Neutron stars are the remnants of explosions of supernovae. Neutron stars are most dense in the universe so these are quite small in size. For example the size of London. They are so dense that a spoonful of neutrons weighs as much as 100 000 Eiffel towers.

It so happens that when two neutron stars approach each other, they turn faster and faster generating the gravitational waves by modifying the space-time around them. Ultimately they collide and fuse. After this the eject lots of matter.

How such events in occuring in the universe are detected? Electromagnetic rays emitted during such an event in the form of visible and invisible energy waves can be tracked by the modern telescopes and spectrometry.

Another technique has been added and it measures the gravitational waves which are generated in such violent events involving massive bodies. Such instruments has been installed in US. Called LIGO (Laser interferometer Gravitational-Wave Observatory) can record the gravitational waves.

One such event of fusion of two neutron stars happened 130 million years ago. The gravitational ripples were detected by LIGO on August 17 at 1241 GMT for 100 seconds. Then after 2 seconds a Gamma rays burst was observed. After hours and days following the event, X-rays, UV rays and infrared rays were detected.

This is the first successful observation of fusion of two neutron stars through Gravitational Waves and as well as through different kind of rays that are emitted.

It also confirmed the premise that gravitational waves travel with speed equal to that of light. This event was made possible with the collaboration of 3674 scientists from 953 institutions all around the world.


Creating a mini sun on the earth: ITER

Of all kinds of energies, the heat energy is most disorganised. This is because heat energy is the reflection of speeds and collisions of the atoms. Third law of thermodynamics states that entropy of universe is always increasing. Since entropy of a system is the measure of randomness or chaos, this means all kinds of energies when used for doing useful work waste a part in the form of heat energy.

Most of the stars are made of hydrogen. It is the fuel that they burn everyday to produced light and heat. Hydrogen atoms exist in 3 forms called isotopes namely H, D and T called hydrogen, deturium and tritium. Hydrogen contains 1 proton and 1 electron and is the simplest of all atoms found in the nature. Deturium contain 1 proton and 1 neutron in the nucleus and 1 electron on the orbit. Tritium nucleus contains 1 proton and 2 neutrons and 1 orbiting electron. The abundance of deturium and tritium atoms is very low on the surface if the earth. Also the tritium atoms are radioactive. 

Chemical reactions occur using only the electrons present in the outer shells through exchange. This process of combining atoms into molecules involves very small energies. Since in nature every thing tends to settle down to state of lowest energy, it means when these molecules are formed energy is liberated. We know most of the elements on the earth are found in the form of ores which are stable forms. 

There are other reactions which involve changes in the nucleus. In these reactions the atom of given element transmutes altogether into another   atom and tremendous amount of energy is liberated. The atoms which have very heavy nuclii are prone to disintegration. Such type of reactions are called Fission reactions. 

There is yet another category of reactions in atoms combine to form bigger atoms and release of energies. Such reactions start with lighter elements most prominently Hydrogen and its isotopes. These reactions are called Fusion reactions. Fusion reactions are source of energy liberated by the stars including our own Sun. 

Nucleus of atom is very compact as compared to the size of atom. Protons which reside in the nucleus along with neutrons must overcome the forces of repulsion to be confined into such a tiny space. There is a energy which is called binding energy which results from the continuous exchanges between protons and neutron through other fundamental particles.

Similarly for such atoms to fuse require that repulsion is overcome. Atoms as we know are in constant motion with spread of different speeds which follows Boltzmann distribution. As said earlier, the speeds increase as the temperature is increased. Then they collide with each with more force and a stage is reached when they overcome the repulsion and fuse into a single entity. 

In the Sun’s core temperatures reach  never to 15,000,000° Celsius. Hydrogen atoms are in a constant state of agitation, colliding at very great speeds. The natural electrostatic repulsion that exists between the positive charges of their nuclei is overcome, and the atoms fuse. The fusion of light hydrogen atoms (H-H) produces a heavier element, helium.

Mass and energy are the same identities. Mass can be converted into energy and we see the examples everyday in our lives. Reverse is also true and since lots of energy is condensed to turn it into mass, so lots of energy is liberated by a very small of mass. Einstein gave us a very compact beautiful equation of energy mass equivalence. 


Since c which is speed of light and highest possible speed with a value of 300000000 meters/sec, squaring it results in enormous number. So even if mass is small, energy obtained is phenomenal. This is explained of law of conservation of mass. In any reaction, mass and energy cannot be destroyed or created. This means the mass of all the reactants should be equal to the mass of all the products. 

It so happens that the final mass of products is smaller than the starting mass of the reactants. Take for example the following fusion reaction in which 1 atom of deturium combines with 1 atom of tritium to form 1 atom of Helium and 1 neutron. The reaction is written as follows.

3H1+2H1 = 4He2 + 1n0

Masses of some elements and neutron are given below in kilograms. 

particle {}_0^1 {\rm{n}} {}_{92}^{235} {\rm{U}} {}_{37}^{93} {\rm{Rb}} {}_{55}^{141} {\rm{Cs}} {}_1^3 {\rm{H}} {}_1^2 {\rm{H}} {}_2^4 {\rm{He}}
mass (x 10-27 kg) 1.675 390.173 154.248 233.927 5.007 3.343 6.645

Since 10-27 kg is common to all, let’s keep it out for later use and do the arithmetic with given values. 

Mass of the reactants

= (5.007 + 3.343) =8.350 

Mass of products

=(6.645 + 1.675) =8.320

So the mass lost =(8.350 -8.320)= 0. 030 x 10-27 Kgs 

So this loss of mass results in the creation of equivalent amout of energy. Using the formula of Einstein we get,

E =0. 030 x 10-27 x(3×108)2=0.27×10-11 joules= 17.1 MeV 

This is the energy  which is generated by 1 atom of deturium and 1 atom of tritium. 1 gram of this fuel will yield energy which is sufficient to heat 9.8 cubic meters of water from 0 degree Celsius to 100 degree Celsius.

Our sun produces the light and heat by burning every second 600 million tons of hydrogen into helium, releasing an enormous amount of energy. But without the benefit of gravitational forces at work in our Universe, achieving fusion on Earth has required a different approach.

At such high temperatures as are inside the sun, atoms are ionised and all the matter exists in the form of plasma or the charged ions gas. Due to enormous gravitation pull whole mass remains constrained and does not disintegrate away.

Now scientists of many countries like France, USA, Russia, India and European countries have pooled resources to create a mini sun on the earth and this project is going on in France. It is called ITER (originally an acronym of International Thermonuclear Experimental Reactor and Latin for “the way”) is an international venture. To stimulate the internal conditions existing inside the sun on the earth reactor, temperature has to be 10 times that of sun. Most crucial step is to contain the plasma because of the absence of sun like enormous gravitation force. In this reactor, the plasma will be contained in a container but will not touch the container walls. This container is very high magnetic field which will force the ions to move inside the walls without touching them.

When this project will become successful, it will open the way to provide the world with much needed energy. This energy will be non polluting and clean with no hazardous emissions like fossil fuels.

Higgs Boson: The God Particle

How many fundamental particles make all what exists in the universe? In our days electrons, protons and neutrons were considered the fundamental particles making up the atoms. Atoms combined with each other according to some rules to make molecules which are the building blocks of the universe. As the research to probe into the heart of these fundamental particles advanced with the advent of high speed particle colliders, it has been found that itis after all not as simple as it looks. Only electron withstood the test of being the fundamental particle. It was shown that neutrons and protons are formed from other particles which have been observed in these particle smashers. We now know that protons and neutrons can be formed from two fundamental particles called up and down quarks. So along with electrons, all that is present can be made from up and down quarks.

But till date 12 fundamental particles have been discovered. So what are these needed for. Whether it is finally 12 or any number is also a guess because theories can get shattered by the availability of more powerful smashers.

It is known that energy and mass are the two sides of the same coin. From the mass we can create energy and vice versa. How particles get different masses?

It was proposed that space is filled with a energy field called Higgs field. If we consider it was water in a container for analogy then it is continuous with break. Water is made of molecules of water which is H2O. These molecules fill all the space occupied by water. It means water molecule is smallest unit . By analogy smallest unit of energy or the particles which make the Higgs field are called Higgs Boson. It is this field which gives the particles their different masses which represent the extent of its interaction with the field.

In the particle accelerators, atoms moving almost at 99% or more the speed of light are collided with each other. They get converted into energy field. This energy field then gets converted into numerous sub atomic particles which are recorded. It is hoped that out of these particles, the Higgs Boson will show up. At least CERN which is doing the research with giant colliders having perimeters of almost 22 kilometers announced that they have observed a particle which is most like the Higgs Boson.

Efforts will continue. Since this particle which stands as the central entity in the Standard Model which is currently the most successful system to explain the existence of the sub atomic particles, will be successfully discovered. Since it is so elusive , it has been nicknamed the “God Particle”

Ice hides memories of past climate!!!!

Almost all the elements in the universe are composed of atoms siblings though are chemically equivalent but have slightly different weight. Atom is composed of equal number of electrons and protons to make it electrically neutral and stable. There are also neutrons which are electrically neutral but have weight almost equal to the proton. Protons and neutrons reside in the centre of atom and called jointly nucleus. This is due to the different numbers of neutrons in these atoms. More the neutrons more shall be the weight of the isotope.
Oxygen has two prominent isotopes. The lighter one contains 8 neutrons and the heavier one contains 10 neutrons this is exactly 2 neutron heavier. The ratio of the heavier atoms to the lighter ones is 1:500 or 0.2%. The number and ratio of the oxygen isotopes is constant if water was present at one place only. But the distribution changes due to physical and biological processes. These two phenomena fractionated the distribution. The oxygen atoms are labeled 18O and 16O.
Since heavier oxygen has lower tendency to evaporate than the lighter and higher tendency to precipitate, the distribution changes continuously with the movement and phase changes of the water.
Originally in the sea water there was a given ratio. Now suppose sun heats the sea and evaporation takes place initiating the water cycle. But notice, the ratio of heavier atoms to lighter atoms will change both is the sea water left behind as well as the vapours. Sea water will become richer in heavier isotope and vapours poorer. Now these vapours rise and starts migrating towards the poles. Temperature gradually begins to fall triggering the precipitation but again further fractionation will take place. In the beginning, some of the heavier atoms will precipitate thus further depleting the pole ward moving water vapours in heavier atoms. So when the snow will start falling, it will be containing the least numbers of heavier atoms.
The snow will settle down. Future years will bring more snow, thus snowflakes shall begin to compact at the lower layers. Snowflakes contain roughly 80% air. After compaction, the air will be expelled and firn will form having only about 20% air. Ultimately lowest layers shall become ice containing only 2% air or less. Layer upon layer will build.
The snow precipitated in the relatively warmer climates shall have more heavier oxygen than the snow precipitated in cooler climates. This phenomena is used to measure the temperature at which a particular layer was deposited. This provides a tool for temperature records in the history of the earth.
For this purpose, scientists take out the continuous cylindrical cores of the ice and measure the abundance of heavier oxygen atoms relative to the lighter ones using ratio recording mass spectrometer and plot this against depth. From the calibration curves with temperature, scientists are able to measure the temperature records.
Knowing the past climatic history of the earth can help in understanding the ice ages epochs, chemical and biological reactions and thus the abundance or otherwise of minerals like petroleum.
Thus the ice deposited over millions of years preserves the memories of the climate in the past. They have been able to recreate the 4 million years record of temperatures.

Carbon Dating

There are atoms which have same chemical properties but different atomic weights. They have same atomic mass because number of protons are identical but additional neutrons make then different in weight. Such atoms are called isotopes.

For example carbon which has 6 protons and 6 neutrons have an isotope which have 6 protons but 8 neutrons.  They are presented as C14 and C12. Addition of protons make them less stable and many of them are radioactive. The rate at which a particular atom decays is independent of temperature, light or darkness. During decay the atom is trying to achieve state of minimum energy and produces atoms with lower atomic numbers and energy.

The rate of decay is expressed in terms of half life. For example a given weight of C14 atoms will become half in weight in 5600 years. precisely.  Then the remaining mass will again take 5600 years to become 1/4 th and so on. This property has many uses and one of the most popular one is carbon dating to determine the age of wood.

Vegetation absorbs CO2 and the same C14/C12 proportion is found in wood as in the atmosphere as long as the tree is alive.But, after a tree is felled it no longer absorbs CO2 from the atmosphere. Inside the dead wood, the C14 brothers slowly disappear, and are not replaced. So, a piece of wood from a Pharaoh’s tomb contains a far lower C14/C12 proportion than a tree that has recently been felled. This type of clock is particularly useful to archaeologists, and allows them to date wood between 200 and 20,000 years old.  The ratio of C14/C12 is measured using a ratio recording mass spectrometer.

What is inside an atom?

Atoms are thought to be the smallest entities which take part in the chemical reactions. They join with each other in different ratios to form the molecules which then combine to form macro-molecules. The molecules can exchange atoms with other atoms or molecules to give rise to different molecules.

Atoms are not the fundamental particles of the matter. Even an atom contains protons and neutrons confined in a very small space called nucleus in the core of the atom and electrons occupy rest of the space. Electrons are negatively charged particles and counter balance the positive charges on the protons in the nucleus. Since their charges are equal and opposite, their number are identical. There are neutrons also which are similar to protons in the weight but have no charge.

Now come the puzzling bits. how do the electrons orient themselves inside a atom. If they are really the particles as we think then they must be having a definite volume. Since we say that the space occupied by the electrons is many times bigger than nucleus and size of electrons is very small, then there must be some empty spaces inside the space outside nucleus. The question is if this is so then what is there which occupies that space. Is it a vacuum?

All these observations force us to conclude that reality is much more complicated than we think. It is usual in the science to construct the simplified models which are capable of explaining a certain set of data. That is why the concept of matter and wave duality was propounded. According to this principle, entities behave both as particle and wave simultaneously. This has been proved in famous experiments in which electrons behave as waves. The famous equation governing this wave nature is Schrodinger’s equations.

Similarly, it is fundamental truth that particles with similar charges repel each other. Then how come are many positively charged protons are crammed into such a small volume. Why do not they fly apart? Why is the arrangement quite stable with nucleus remaining unchanged for years. Again the things are not what they are thought to be. It has now been proved that even protons and neutrons are not the fundamental particles but are made of strange type of particles called Quarks. It has been found that mass of the nucleus is not equal to aggregate mass of protons and neutrons it contains. It is lesser than that. Where is the mass that is lost. It is present in the form of energy and amount of energy is according to Einstein’s equation E=mass multiplied by speed of light squared.

That is why we are making atom smashers where we break apart the atoms by bombarding them with particles approaching speeds of light and analyze the particles which are formed during collision.