HIGGS BOSON

 HIGGS BOSON

Introduction:

‘Higgs boson’ is an elementary particle in standard model of particle physics produced by the quantum excitation of the Higgs field one of the field in particle physics theory. It is named after the physicist Peter Higgs, who in 1984 along with other scientists proposed the mechanism which suggested the existence of such a particle. The existence was confirmed in 2012 by the ATLAS & CMS collaboration based on collisions in the LHC at CERN.

The Brout -Englert –Higgs mechanism:

In the 1970s, physicists realized that there are very close ties between two of the found fundamental forces – the weak force & the electromagnetic force.  The two forces can be described within the same theory, which forms the basis of the Standard Model. This ‘unification ’implies that electricity are all manifestation of a single underlying force known as the electroweak force.

The basic equations of the unified theory correctly describes the electroweak force & its associated force carrying particles, namely the photon & the W & Z bosons, except for major glitch. All of these particles emerge without a mass. While this is true for the photon, we know that the W & Z have mass, nearly 100 times that of a proton. Fortunately, theorists Robert Brout, Francois Englert & Higgs made a proposal that was to solve this problem. What we now call the Brout-Englert –Higgs mechanism gives a mass to the W & Z when they interact with an invisible field, now called the ‘HIGGS FIELD’, which pervades the universe.

At CERN on 4 July, the ATLAS & CMS collaborations present evidence in the LHC data for a particle consistent with a Higgs boson, the particle linked to the mechanism proposed in the 1960s to give mass to the W,Z & other particles.

Just after the big bang, the Higgs field was zero but as the universe cooled and the temperature fell below a critical value the field grew spontaneously so that any particle interacting with it acquired a mass.The more a particles interact with the field, the heavier it is. Particles like the photon that do not interact with it are left with no mass at all. Like all fundamental fields, the Higgs field has an associated particle the Higgs boson. The Higgs boson is the visible manifestation of the Higgs field, rather like a wave at the surface of the sea.

The Elusive Particle:

A problem for the many years has been that no experiment has observed the Higgs boson to confirm the theory. On 4 July 2012, the ATLAS  and CMS experiments at CERN’S Large Hadron collider announced they had each observed a new particle in the mass region around 125 Gev. This particle is consistent with the Higgs boson but it will take further work to determine whether or not it is the Higgs boson, as proposed within the standard model, is the simplest manifestation of the Brout –Englert –Higgs mechanism.

On 8 october 2013 the Nobel prize in physics was awarded jointly to Francois Englert & Peter Higgs for the theoretical discovery of a mechanism that contributes to our understanding of origin of mass confirmed through the discovery of the predicted fundamental particle, by the ATLAS & CMS experiments at CERN’S Large collider.”

SUBMITTED BY:

Likhitha B

Malavika Ajith

Meghana RV

Mithuna P
Namitha D
I M Sc Physics

SUBMITTED DATE:  25-03-2019

REFERENCE:
Internet
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Evolution of a Star

INTRODUCTION:

Stellar evolution is the process by which a star changes over the course of a time. Depending on the mass of the star, its lifetime can range from a few million years for the most massive to trillions of years to least massive which are considerably longer than the age of the universe. All stars are born from collapsing clouds of gas and dust, often called Nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main sequence star. Depending on their mass, they reach the end of their evolution as whitedwarf, neutron star or black hole.

                         

NEBULA:

—  Nebula is a cloud of hydrogen gas and dust. It is a birthplace of stars. A protostar is a very young star that is still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of the stellar evolution. For a low mass star, it lasts about 500000 years. Protostars are usually surrounded by dust, which blocks the light they emit, so they are difficult to observe in the visible spectrum.

                                                    

AVERAGE STAR:

—  After a part of nebula gains sufficient mass, it begins to collapse under its own gravity. As a result, the increased pressure in the core triggers nuclear fusion of hydrogen into helium. This stops further gravitational collapse and the star is officially born. The size of the star at this point will set the course for the rest of its life. The star with the mass between 0.5 to 8 times the mass of our sun is considered as an ‘average star’.

                                                

RED GIANT:

—  A Red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The most common red giant is stars on the red giant branch that are still fusing hydrogen into helium core.

PLANETARY NEBULA:

—   All planetary nebulae form at the end of intermediate massed star's lifetimes. They are a relatively short-lived phenomenon, lasting perhaps a few tens of thousands of years, compared to a considerably longer phases of stellar evolution. Once all of the red giant's atmosphere has been dissipated energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (PNN), ionizes the ejected material. Absorbed ultraviolet light then energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

                                 

WHITE DWARF:

—  A white dwarf is a very dense star that is the end stage of average star life. After the star runs out of helium, the star will try to combine carbon, which the star can’t combine. So the gas spreads apart from the star leaving behind a carbon dense white dwarf. When the white dwarf runs out of its remaining energy it loses its brightness and becomes a brown dwarf.

                           

MASSIVE STARS:

—  Massive stars are born, just like average stars out of clouds of dust called nebula. When a nebula collects enough mass it begins to collapse under its own gravity. The internal pressure created by this collapse is enough to trigger fusion of hydrogen deep in its core. When nuclear fusion begins a star is born. When a star is considered massive if it is at least 8 times more massive than our sun.

RED SUPERGIANT:

—  They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares are the brightest and best known red super giants, indeed the only first magnitude red supergiant stars. They are much cooler than the sun and are observed to rotate slowly or very slowly.

SUPERNOVA:

—  A supernova is an event that occurs upon the death of certain type of stars. A supernova is the explosion of a star. It is the largest explosion that takes place in space. The most recent directly observed supernova in the milky way was Kepler’s supernova in 1604.

NEUTRON STARS:

—  Neutron stars are created when giant stars die in supernovas and their cores collapse, with the proton and electrons essentially melting into each other to form neutrons. Neutron stars rotate extremely rapidly after their formation due to the conservation of angular momentum.

BLACK HOLES:

—  Black holes are incredibly massive but cover only smaller region. Virtually noting can escape from them. Under classical physics even light is trapped by a blackhole. A black hole can be formed by death of a massive star. A black hole is a region of a space-time exhibiting such strong gravitational effects that nothing can escape from it.

HR DIAGRAM:

The Hertzprung-Russell diagram is a graphical tool that astronomers use to classify stars according to their luminosity, special type, color, temperature and evolutionary stage.

Stars are stable phase of hydrogen burning lie along the main sequence  according to their mass. After a star uses up all the hydrogen in its core, it leaves the main sequence and moves towards the red giant branch. The most massive stars may also become red supergiants, in the upper right corner of the diagram.

The lower left corner is reserved for the white dwarfs.

Submitted by:

Ezitha Monteiro

Delvita Veigas

Divyashree

Keerthana

I M Sc Physics

Reference

Internet

Journal

From the southern sky - Phoenix

The southern sky

Phoenix

Phoenix constellation lies in the southern sky. It was named after the phoenix, the mythical bird that rises from its own ashes.

The constellation was originally introduced by the Dutch astronomer and cartographer Petrus Plancius from the observations of the Dutch navigators Frederick Houtman and Pieter Dirkszoon Keyser in the late 16th century. It is a relatively small constellation, but it is the largest among the 12 constellations created and named by Plancius. It was first depicted on his globe in 1598 and later appeared in Johann Bayer’s atlas Uranometria in 1603.

Phoenix constellation is easy to see for anyone in Australia and South Africa during southern hemisphere summer, but generally can’t be observed by anyone living north of the 40th parallel, and lies pretty low in the sky for observers north of the equator.

Phoenix contains several notable deep sky objects, among them the Phoenix Cluster of galaxies, the black hole candidate HLX-1, and Robert’s Quartet, a compact galaxy group.

Phoenix is the 37th constellation in size, occupying an area of 469 square degrees. It is located in the first quadrant of the southern hemisphere (SQ1) and can be seen at latitudes between +32° and -80°. The neighboring constellations are Eridanus, Grus, Fornax, Hydrus, Sculptor and Tucana.

Phoenix belongs to the Johann Bayer family of constellations, along with Apus, Chamaeleon, Dorado, Grus, Hydrus, Indus, Musca, Pavo, Tucana and Volans.

Phoenix contains five stars with known planets and does not have any Messier objects. The brightest star in the constellation is Ankaa (Alpha Phoenicis) with an apparent magnitude of 2.40. There is one meteor shower associated with the constellation -the Phoenicids-which occurs around December 5 every year

French explorer and astronomer Nicolas Louise de Lacatle charted and designated 27 starts with the Bayer designation Alpha through to omega in 1756, of these he labelled two stars close together lambda and assigned omicron, psi and omega to three stars.

MAJOR STARS IN PHOENIX

1. Ankaa – α Phoenicis (Alpha Phoenicis)

2. β Phoenicis (Beta Phoenicis)

3. γ Phoenicis (Gamma Phoenicis)

4. κ Phoenicis (Kappa Phoenicis)

5. ζ Phoenicis (Zeta Phoenicis)

6. ν Phoenicis (Nu Phoenicis)

7. SX Phoenicis

Brightest star - Ankaa or Alpha Phoenicis

Ankaa is the brightest star in the constellation. Its name comes from the Arabic al- ‘anqā’, which means “the phoenix.” It is also sometimes known as Nair al- Zaurak, or “the bright star of the skiff” (an-na’ir az-zawraq in Arabic).

Alpha Phoenicis is a spectroscopic binary star approximately 85 light years distant. The system has the combined stellar classification K0.5 IIIband a combined apparent magnitude of 2.377. The two components in the system orbit each other with a period of 3848.8 days (or 10.5 years). The primary star, as the spectral class indicates, is an orange giant.

Water on Mars

Water on Mars

Introduction

Mars is the fourth planet from the Sun and the second smallest planet in the Solar system after Mercury. Have you heard the big news!?

NASA has reported there is water on Mars. Let’s travel to the Mars now..

Using an imaging spectrometer on NASA’s Mars Reconnaissance Orbiter(MRO), researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet.

These dark, narrow 100 meter-long streaks called ‘recurring slope lineae’(RSL) flowing downhill are inferred to have been formed by contemporary flowing water. Recently, planetary scientists detected hydrated salts on these slopes at Hale crater, corroborating their original hypothesis that the streaks are indeed formed by liquid water.

Another view of ‘recurring slope lineae’ or RLSs, flowing out of a mountainside on Mars.

Almost all water on Mars today exists in small quantities as vapour in the atmosphere and occasionally as low volume liquid brines in shallow Martian soil. The only plane where water ice is visible at the surface is at the north polar ice cap.

Scientists have also travelled deep underground into mines and found microorganisms related to ancient species that once lived in watery environments much close to the surface. Such migrations raise the possibility of the same thing happening on Mars- as the water retreated, life moved deeper underground.

However, while the find is tantalizing for astrobiologists eager to find alien life, it is also a bit of tease. It will be decades before astronauts can visit the surface of Mars and likely much longer before we can drill a mile beneath the dusty surface. So we may not see any expeditions in our lifetime.

Observations of the Red planet indicate that rivers and oceans may have been prominent features in its early history. Billions of years ago, Mars was warm and wet world that could have supported microbial life in small regions. But the planet is smaller than Earth, with thinner atmosphere. Over the time, as liquid water evaporated, more and more of it escaped into space, allowing less to fall back to the surface of the planet.

More than five million cubic kilometres of ice has been identified at or near to cover the whole planet to a depth of 35 meters.

Although there are some extremophile organisms that survive in hostile condition on Earth, including stimulations that approximate Mars, plants and animals generally cannot survive the ambient conditions present on the surface of Mars. Surface gravity of Mars is 38% of Earth. Researches are going on this area.

Submitted by

Students

1^st M.Sc. Physics

Reference

• Internet
• Journal

SPECTRUM

Spectrum

Introduction

A spectrum is a condition that is not limited to a specific set of values but can vary, without steps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colours in visible light after passing through a prism.  As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum.

In the 17th century, the word spectrum was introduced into optics by Isaac Newton, referring to the range of colours observed when white light was dispersed through a prism. Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.

The term spectrum was expanded to apply to other waves, such as sound waves that could also be measured as a function of frequency, frequency spectrum and power spectrum of a signal.

Electromagnetic spectrum

Electromagnetic spectrum refers to the full range of all frequencies of electromagnetic radiation and also to the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object. Devices used to measure an electromagnetic spectrum are called ‘spectrograph’ or ‘spectrometer’. The visible spectrum is the part of the electromagnetic spectrum that can be seen by the human eye. The wavelength of visible light ranges from 390 to 700nm. The absorption spectrum of a chemical element or chemical compound is the spectrum of frequencies or wavelengths of incident radiation that are absorbed by the compound due to electron transitions from a lower to a higher energy state.

Light from many different sources contains various colours, each with its own brightness or intensity. A rainbow, or prism, sends these component colours in different directions, making them individually visible at different angles. A graph of the intensity plotted against the frequency is the frequency spectrum of the light. When all the visible frequencies are present equally, the perceived colour of the light is white, and the spectrum is a flat line.

In radio and telecommunications, the frequency spectrum can be shared among many different broadcasters. The radio spectrum is the part of the electromagnetic spectrum corresponding to frequencies lower below 300 GHz, which corresponds to wavelengths longer than about 1 mm. The microwave spectrum corresponds to frequencies between 300 MHz (0.3 GHz) and 300 GHz and wavelengths between one meter and one millimeter.

Mass spectrum

A plot of ion abundance as a function of mass to charge ratio is called a mass spectrum. It can be produced by a mass spectrometer instrument. The mass spectrum can be used to determine the quantity and mass of atoms and molecules.

Energy spectrum

In physics, the energy spectrum of a particle is the number of particles or intensity of a particle beam as a function of particle energy. Examples of techniques that produce an energy spectrum are alpha particle spectroscopy, electron energy loss spectroscopy, and mass analyzed ion kinetic energy spectrometry.

Discrete spectrum

In physics, particularly in quantum mechanics, some differential operator have discrete spectra, with gaps between values. Common cases include the Hamiltonian and the angular momentum operator.

Spectrogram

In acoustics, a spectrogram is a visual representation of the frequency spectrum of sound as a function of time or another variable.   An apparatus used for recording and measuring spectra, especially as a method of analysis.

Splitting of white light

Light changes speed as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle. The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media. 

Light of different colours to  be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow. This can be used to separate a beam of white light into its constituent spectrum of colours.

Reference

·        Wikipedia

SUBMITTED BY: 

Ahallya K V

Akshatha G

Akhila K

Athira V

Amal George