Astronomy Flashcards
The universe
The universe:
The universe is everything. It includes all the existing matter, time, and energy that space contains. It is incomprehensibly large and continually expanding. It contains both physical (atoms, planets, etc.) and non-physical (light, gravitation, space, etc.) components.
It comprises of billions of galaxies, each comprising an average of 100 billion stars. For example, the Milky Way galaxy is believed to possess 100 to 400 billion stars. Our sun is one star among billions in the Milky Way. Our solar system consists of our sun and its orbiting planets, numerous moons, asteroids, comets, rocks, and dust.
The Big Bang theory is the prevailing cosmological model for the universe’s Earth. It refers to a gigantic explosion of matter and energy about 13.6 billion years ago. Initially, all space was contained in a single point of a very high density and high temperature from which the universe has been expanding in all directions since the Big Bang.
In 1920, Edwin Hubble provided evidence that the universe is expanding. It is also called the Expanding Universe Hypothesis.
It is the observation that the expansion of the universe is such that the velocity at which a galaxy is moving away from the observer is continuously increasing with time (Hubble’s law). It implies that the universe will get increasingly colder as matter spreads across space.
Dark matter is an unknown form of energy that is hypothesized to permeate or spread throughout all of space, tending to accelerate the universe’s expansion.
The two discoveries have reaffirmed scientists’ faith in the Big Bang theory:
1) The measured redshift in the light radiated from distant stars. This property of starlight is similar to the lowering in pitch of a departing plane vessel known as Doppler’s effect. The Doppler shift or red effect and blue shift is described as the change in frequency of a light wave depending on whether an object is moving towards or away from us. When an object is moving away from us, the light from the object is known as redshift. When an object is moving towards us, the light from the object is known as blue shift. Astronomers use redshift and blue shift to deduce how far an object is away from Earth. The presence of weak microwave radiation throughout the space.
2) Fragments of matter in space itself have been expanding outward like a display of fireworks.
The Big Crunch, or the death of the universe: At some point, the universe would reach a maximum size and begin collapsing. The universe would become denser and hotter again, ending in a state like that in which it started a single point of very high density.
Cosmic Microwave Background Radiation: Thermal radiations which remained after the Big Bang are known as relic radiation left over from the Big Bang. The cosmic microwave background is fundamental to observational cosmology because it is the oldest light in the universe and can be found in all directions. The space between the stars and galaxies is completely dark and recent sensitive radio telescopes show a faint background glow and the glow is strongest in the microwave region of radio spectrum and hence it is called cosmic microwave background. Discovery of cosmic microwave background is considered as a landmark proof of the concept of accelerating expansion of the universe and the Big Bang theory.
The electromagnetic waves in the electromagnetic spectrum are gamma rays, X-ray, UV, visible, infrared, micro and radio. The gamma rays have the highest energy, the lowest wavelength and the highest penetration capacity. The radio waves have the lowest energy, highest wavelength and the lowest penetration capacity.
Gravitational Lensing:
This occurs where the path of light from a distant object is bent by the gravitational field of a massive object like the galaxy or a black hole. This bending of light can cause distant objects to appear distorted or magnified depending on the alignment of the massive object and the observer. The effect of Gravitational Lensing was first predicted by Albert Einstein in his theory of general relativity and hence been observed and studied by astronomers.
Evidence for Big Bang Theory:
Physical phenomena such as morphological redshift, discovery of cosmic microwave background, radiation and gravitational waves have been added to the Big Bang theory.
The Theory of General Relativity:
In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers and that the speed of light in a vacuum was independent of the motion of all observers. As a result, he found that space and time were interwoven into a single continuum known as space-time. Events that occur at the same time for one observer could occur at different times for another. This was the Theory of General Relativity. In it, he determined that the massive objects distort space-time which is felt as gravity. Gravitational Lensing and Gravitational Waves are strong evidence for Einstein’s Theory of General Relativity.
Galaxies
Galaxies are a huge collection of gas, dust, and billions of stars, and their solar system held together by their gravity.
Our galaxy is the Milky Way galaxy, which is a spiral galaxy estimated to contain 100 to 400 billion stars. Inert stars travel faster than those further out.
A supermassive black hole called Sagittarius A is at the center. Our sun and solar system are located in the Orion arm, 26,000 light-years from the center.
Stars like our sun are rare in the Milky Way, while substantially dimmer and cooler stars known as red dwarfs are common.
The Sun completes one lap of the galaxy about every 220 million years at 285 km per second.
The Saraswati is a supercluster of galaxies. A group of Indian scientists from IUCAA Pune and IISER Pune discovered this supercluster. It is a supercluster of 43 galaxies and is 4 billion light-years away in the direction of the constellation Pisces.
Solar system
The solar system:
The IAU classifies planets and other celestial bodies, except satellites in our solar system, into three distinct categories:
- Planet is a celestial body that is in orbit around the sun and has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium, nearly round-shaped, and has cleared the neighborhood around its orbit.
- Dwarf planet is a celestial body that is in orbit around the sun and has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium, nearly round-shaped, and has not cleared the neighborhood around its orbit and is not a satellite.
- All other objects except satellites orbiting the sun shall be referred to collectively as small solar system bodies.
The International Astronomical Union, IAU, founded in 1919 with mission to promote and safeguard the science of astronomy in all its aspects, including research, communication, education, and development through international communication, has its headquarters in Paris, France, a global authority for naming planetary features in the solar system.
Terrestrial versus Jovian planets:
Terrestrial are inner planets. Jovian are outer planets. They are separated by an asteroid belt in between them. The terrestrial planets are Mercury, Venus, Earth, and Mars. The Jovian planets are Jupiter, Saturn, Uranus, and Neptune. Terrestrial planets are close to sun, closely spaced orbits, small masses, small radius, mainly rocky, solid surface, high density, slow rotation, weak magnetic fields, few moons, and no rings. The Jovian planets are far from the sun, widely spaced orbits, large masses, large radius, mainly gaseous, no solid surface, low density, fast rotation, strong magnetic fields, many moons, and many rings.
The dwarf planets are Ceres (950kms, between Mars and Jupiter), Pluto (2400 km, beyond Neptune), Eris (2300km, close to Pluto), Makemake (1400 km, beyond Neptune), and Haumea (1400 km, beyond Neptune). The biggest of these is Pluto, and the smallest of these is Ceres.
Moons and Natural Satellites:
Bodies that orbit planets and asteroids in our solar system. Most of the major planets, except Mercury and Venus, have moons.
Pluto and some other dwarf planets, as well as many asteroids, also have small moons. Saturn and Jupiter have the most moons, with dozens orbiting each of the two giant planets.
Saturn has 146 moons, Jupiter has 95, Uranus has 27, Neptune has 14, Mars has 2, and Earth has 1. Among the dwarf planets, Pluto has 5 moons, followed by Haumea at 2, Eris at 1, and Makemake at 1, Ceres has 0.
Jupiter’s menagerie of moons includes the largest in the solar system, Ganymede, an ocean moon, Europa, and a volcanic moon, Io. Many of Jupiter’s outer moons have highly elliptical orbits, and orbit backwards, opposite to each other.
Saturn, Uranus, and Neptune also have some irregular moons, which orbit from their respective planets.
Saturn has two ocean moons, Encledus and Titan.
Neptune’s moon, Triton, is as big as Pluto, and orbits backwards compared to Neptune’s direction of rotation.
Pluto’s large moon, Charon, is about half the size of Pluto.
Exoplanet, also called extrasolar planet, is a planet outside of our solar system that usually orbits another star in our galaxy. Milky Way galaxy comprises of 100-400 billion stars and their respective solar systems.
In 1992, the first confirmation of detection of exoplanets was discovered. Most of discovered exoplanets are in relatively small region in our galaxy, the Milky Way. Small means within thousands of light years of our solar system, one light year is equal to 9.46 trillion kilometers. Kepler mission was named in honor of the 17th century German astronomer Johannes Kepler, who discovered the laws of planetary motion. It was launched in 2009, 3.5 years mission to monitor 1,50,000 stars in a patch of sky in the Milky Way, NASA’s first planet hunting mission, which discovered more than 2,600 of around 3,800 exoplanets. Kepler’s formal goal is to measure a number called Eta Earth, that is fraction of sun-like stars that have an Earth-sized object orbiting them in the Goldilocks or habitable zone, where it is warm enough for the surface to retain liquid water. Kepler is succeeded by NASA’s Transiting Exoplanet Survey Satellite, or TESS, which was launched in April 2018. TESS is the new planet hunter for NASA.
Stars:
Any massive self-luminous celestial body of gas that shines by radiation derived from its internal energy sources and held together by self-gravity. Energy is produced in the star using nuclear fusion reaction.
The difference between stars and planets:
Stars are incredibly hot, having high temperatures to them. Planets, on the other hand, are relatively low temperatures. Stars are objects that produce their own light and don’t rely on an external source for the production of light. Planets are incapable of producing their own light. Stars have a unique effect of twinkling in the sky. Planets do not exhibit the twinkling effect unlike stars. The stars change their position but can be only seen after a long time due to substantial distance. Planets in orbits on their own axis change their positions constantly. Stars consist of matters like hydrogen, helium, and other light elements. Planets, on the other hand, contain solids, liquids, gas, and other, or a combination thereof.
Constellations:
Stars forming a group that has a recognizable shape. Few famous constellations are the Great Bear, Big Dipper, Saptarshi, Ursa Major, and Orion, Hunter, Cassiopeia, and Leo Major. Ursa Major moves around the pole star. In fact, all the stars appear to revolve around the pole star. Ursa Major is a northern constellation and may not be visible from some points in the southern hemisphere. Orion can be seen during the winter in the late evening. The star Sirius, the brightest star in the sky, is located close to Orion. Cassiopeia is another prominent constellation in the northern sky. Cassiopeia is visible during the winter in the early part of the night.
Life cycle of a star:
Nebula, a cloud of gas, mostly hydrogen and helium, and dust in space. Gravity causes the nebula to contract and form dense regions. Nebula are the birthplaces of stars.
Proto-stars look like a star, but its core is not yet hot enough for nuclear fusion to take place. The luminosity comes exclusively from the heating of the proto-star as it contracts because of gravity. Proto-stars are usually surrounded by dust, which blocks the light that they emit, so that they are difficult to observe in the visible spectrum.
T-Tauri phase, very young, light-weight star, less than 10 million years old, that is, that it is still undergoing gravitational contraction. It represents an intermediate stage between a proto-star and a low-mass main-sequence star like the Sun.
Main sequence stars are stars that are fusing hydrogen atoms to form helium atoms in their cores. Most stars in the universe, almost 90% are main sequence stars. Our sun is a main sequence star. Towards the end of its life, a star like the sun swells up into a red giant before losing its outer layers as a planetary nebula and finally shrinking to become a white dwarf.
Red giants have diameters between 10 to 100 times that of the sun. They are very bright, although their surface temperature is lower than that of the sun. A red giant is formed during the later stages of evolution as it runs out of hydrogen pools. At its center, it still fuses hydrogen into helium in a shell surrounding a hot, dense, degenerate helium core. As the layer surrounding the core contains a bigger volume of fusion of hydrogen to helium around the core, it releases far more energy and pushes much harder against the gravity and expands the volume of the star.
Red supergiant: As red giant star condenses, it heats up even further, burning the last of its hydrogen, and causing star’s outer layers to expand outwards. At this stage, the star becomes a large red giant, or a red supergiant.
The red dwarf, faintest, less than 1/1000th the brightness of sun. Main sequence stars are called red dwarfs, have low luminosity and not visible to the naked eye. According to some estimates, red dwarfs make up three quarters of stars in the Milky Way galaxy. For example, Proxima Centauri, nearest star to sun, is a red dwarf.
Planetary nebula: The outer layer of gas and dust, no planets involved, that have lost when the star changes from a red giant to a white dwarf. At the end of its lifetime, the sun will swell up into a red giant, expanding out beyond the orbit of Venus, and as it burns through its full, it will eventually collapse under the influence of gravity. The outer layers will be ejected in a shell of gas that will last a few tens of thousands of years before spreading into the vastness of space.
The white dwarf, very small, hot star, the last stage in the life cycle of a star like the sun. White dwarfs are the remains of normal stars whose nuclear energy supplies have been used up. It consists of degenerate matter with very high density. Degenerate matter, fusion in a star’s core produces heat and outward pressure, but this pressure is kept in balance by the inward push of gravity generated by a star’s mass. Gravity is a product of mass. When the hydrogen used as fuel vanishes and fusion slows, gravity causes the star to collapse. This creates a degenerate star. Great densities like a degenerate star are only possible when electrons are displaced from their regular shells and pushed closer to the nucleus, allowing atoms to take up less space. Matter in this state is called degenerate matter.
Black dwarf is the last stage of stellar evolution. A black dwarf is a white dwarf that has sufficiently cooled and no longer emits significant heat or light. Because of the time required for the formation of black dwarf from white dwarf is approximately 13.8 billion years, which is longer than the estimated current age of the universe. No black dwarfs are expected to exist in the universe yet.
Supernova, explosive death of a star that often results in the star obtaining the brightness of 100 million suns for a short time. Extremely luminous burst of radiation expels much or all of a star’s material at a great velocity, driving a shock wave into the surrounding interstellar medium. These shock waves trigger condensation in a nebula, paving the way for the birth of a new star. If a star has to be born, a star has to die. A great proposition of primary cosmic waves comes from supernovae.
Neutron star, composed mainly of neutrons and are produced after a supernova, forcing the protons and electrons to combine to produce a neutron star. These are very dense and if its mass is any greater, its gravity will be so strong that it will shrink further to become a black hole.
The Chandrasekhar limit is the maximum mass at which a star near the end of its life cycle can become a white dwarf and above which the star will collapse to form a neutron star or black hole. Maximum mass approximately 1.44 solar masses.
Black holes are believed to form from massive stars at the end of their lifetimes. The density of matter in a black hole cannot be measured as it is infinite. The gravitational pull is so great that nothing can escape from it, not even light. Black holes distort the space around them and suck neighboring matter into them, including stars. Gravity is so strong that nothing, not even light, can escape from them and it wraps space-time around it. The black hole is created when a star dies and the gravity pull is so strong that even light cannot escape making them invisible. They can only be detected by the effects they have on their surroundings in space.
Types of black holes:
1. Stellar black holes: Formed by the collapse of a single massive star.
- Intermediate black holes, their masses are between 100 to 1 lakh times that of the Sun.
- Supermassive black holes, their masses ranging from millions to billions of times that of the Sun, found at the centers of mass galaxies, including our own Milky Way galaxy.
Black holes are important for understanding the universe and its evolution. They play a role in the formation and evolution of galaxies and the distribution of matter throughout the universe. They help us understand the fundamental properties of space-time and gravity.
Gravitational waves, these are invisible yet incredibly fast ripples in space-time which are produced by the movement of massive celestial bodies like black holes, neutron stars, etc. These ripples propagate outwards. These were first postulated in 1916 by Einstein’s general theory of relativity which explains how gravity works.
Gamma-ray bursts are extremely energetic explosions that have been observed in distant galaxies. These are the brightest electromagnetic events known to occur in the universe.
Long gamma-ray bursts occur when a star much more massive than the sun runs out of fuel, its core suddenly collapses and forms a black hole. As matter swirls towards the black hole, some of it escapes in the form of two powerful jets that rush outwards at almost the speed of light in opposite directions. Each jet drills through the star, producing a pulse of gamma rays, the highest energy form of light that can last up to minutes.
Short gamma-ray bursts occur when pairs of compact objects like neutron stars, which also form during the stellar collapse, spirals inwards over billions of years and collide.
Gamma-ray bursts 200826A, a sharp blast of high energy emission lasting just 0.65 seconds, it is considered to be the shortest gamma-ray burst till now and occur due to the death of a massive star.
Fermi Gamma-ray Space Telescope, formerly GLAST, Gamma-ray Large Area Space Telescope is a space observatory being used to perform gamma-ray astronomy observations from low-Earth orbit launched in 2008 by NASA.
Kuiper Belt:
Kuiper Belt is a region of space. The inner edge begins at the orbit of Neptune at about 30 AU from the Sun. (1AU = or astronomical unit is distance from earth to sun).
Outer edge continues outward to nearly 1000 AU with some bodies on orbit that go even further beyond.
There are bits of rock and ice, comets, and dwarf planets in the Creeper Belt besides Pluto and a bunch of other comets. Other interesting Kuiper Belt objects are Eris, Makemake, and Haumea. They are dwarf planets like Pluto.
It is similar to the Asteroid Belt in that it contains many small bodies or remnants from solar system formation.
Asteroid Belt:
The word asteroid means star-like because when astronomers first discovered them in early 1800s, they thought they looked like stars. Their movement is separate from stars.
Asteroid Belt is a torus-shaped region in the solar system centered around the Sun and roughly spanning the space between the orbits of planets Mars and Jupiter. Belt lies between 2.2 and 3.2 AU from our Sun, so the width of Asteroid Belt is roughly 1 AU or 150 million km. Early in the life of the solar system, dust and rocks circling the Sun were pulled together by gravity into planets, but not all of the ingredients created new worlds. Left ingredients formed Asteroid Belt.
Asteroids vs Meteors vs Meteorites:
Asteroids are large rocky bodies in shape in orbit around the Sun and do not have an atmosphere, but some asteroids have their own moons.
The largest asteroid is Ceres, about 950 km in diameter, and Ceres is so large that it is also categorized as a dwarf planet.
Asteroids are divided into three classes:
- Found in main asteroid belt between Mars and Jupiter.
- Trojans, asteroids that share an orbit with a larger planet.
- Near-earth asteroids, which have orbits that pass close by the Earth.
Meteoroid is a much smaller rocky body in space in orbit around the Sun. A Meteoroid is a piece of interplanetary matter that is smaller than an asteroid in frequency, only millimeters in size.
Meteor: Most meteors that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface. When they burn up during their descent, they create beautiful trails of light known as meteors, sometimes called shooting stars.
Meteorite: If a small asteroid or large meteorite survives its fiery passage through the Earth’s atmosphere and lands on Earth’s surface, it’s then called a meteorite. Meteorites created in India are Lonar Lake, 1.8 km in diameter in Buldhana of Maharashtra, a Ramsar site, Thala Crater, 19 km in diameter in Shivpuri, MP, Ramgarh Crater, 3.5 km in diameter in Kota, Rajasthan.
Comets are like dirty snowballs made mainly of ice and frozen carbon dioxide with some dust and organic molecules left over from the formation of the solar system. Some, like the Halley’s Comet, are regular visitors to our skies, while others have only been seen once in human history and may only return every several hundred years. Origin of Comets. Short-period comets with an orbital period of a few hundred years originate in the Kuiper Belt. Long-period comets with origins of thousands of years come from the more distant Oort cloud. The Oort cloud is a giant shell of icy bodies that encircles the solar system, occupying space at a distance between 5,000 to 1,00,000 AU. When passing close to the sun, comets heat up due to the effects of the solar wind upon the nucleus and begin to outgas, displaying a visible atmosphere or coma, and sometimes also a tail. Orbit of Halley’s Comet brings it close to Earth every 76 years. It last visited in 1986.
Gravitational waves
Gravitational waves are ripples in the fabric of space-time caused by some of the most violent and energetic processes in the universe.
Albert Einstein predicted existence of gravitational waves in 1916 in his Theory of General Relativity.
Massive accelerating objects like neutron stars or black holes orbiting each other would disrupt space-time in such a way that waves of distorted space would radiate from the source, like the movement of waves away from a stone thrown into a pond. These ripples travel at the speed of light through the universe, carrying with them information about their origin.
They can only be detected by specialized devices like LIGO.
The LIGO project is ground-based. It stands for Laser Interferometer Gravitational Wave Observatory, an international network of laboratories that detect gravitational waves from the universe.
LIGOs are designed to measure changes in distance up to magnitudes smaller than the length of the proton.
High-precision instruments are needed because of the extremely low strength of the gravitational waves that make their detection very difficult.
In 2015, LIGO made history by detecting gravitational waves for the first time, which led to the Nobel Prize in Physics in 2017 to Rainer Weiss, Barry C. Barish, Kip S. Thorne.
Black hole mergers are the source of some of the strongest gravitational waves.
Currently, LIGO consists of two identical detectors, or interferometers, separated by 3000 km: LIGO Hanford Observatory and LIGO Livingston Observatory, both in the USA. Also, three sister facilities are in Italy, Japan, and Germany.
LIGO-India project: The Indian government in early 2023 approved the construction of LIGO Observatory in India, whose Hingoli district of Maharashtra.
It will have two perpendicularly shaped, 4 km long vacuum chambers that constitute the most sensitive interferometer.
LIGO-India is an international collaboration between LIGO Laboratory and three lead institutions in the LIGO-India Consortium: Institute of Plasma Research, Gandhinagar, IUCAA, Pune and Raja Ramanna Centre for Advanced Technology, Indore.
The LISA Project (spacebased) (ESA + NASA Mission):
LISA stands for Laser Interferometer Space Antenna.
Large-scale space mission designed to detect one of the most elusive phenomena in astronomic gravitational waves.
With LISA, we will be able to observe the entire universe directly with gravitational waves, learning about the formation and structure of galaxies, stellar evolution, the early universe, and the structure and nature of space time itself.
Due for launch in mid-2030s, it will be the first dedicated space-based observatory.
LISA, a population of three identical spacecraft, arranged to form an equilateral triangle with 2.5 million km distance between them.
LISA will work rather like LIGO, but with arms 6 lakh times longer than LIGO. It will extend our capabilities to listen to new kinds of dark phenomena in the universe. With test mission LISA Pathfinder, launched in 2015, it is the quietest place known to humankind.
The LISA Pathfinder has exceeded performance expectations by a factor of 5.
Evolved LISA (E-LISA): After the success of LISA Pathfinder experiment, E-LISA is the plan of setting into space the three spacecraft, a mother and two daughters spacecraft, which will fly in a triangular formation, trailing the Earth in its orbit around the Sun at a distance of over 50 million km.
Matter and anti matter
Matter and Antimatter:
Matter is any substance that has a mass and a volume. It is composed of particles known as fermions, such as protons, neutrons, and electrons. Matter particles typically have a positive, negative, or neutral electrical charge. For example, protons carry a positive charge, electrons carry a negative charge, and neutrons have no electric charge.
Antimatter consists of antiparticles, which have the same mass as their corresponding matter particles, but possess opposite charges. They save charges opposite to their matter counterparts. Antiprotons have a negative charge, positrons and antielectrons have a positive charge, and antineutrons have no electric charge.
When matter and antimatter come into contact, they annihilate each other. Collision between resulting in conversion of their mass into energy process is called annihilation. This process releases an enormous amount of energy in the form of gamma rays and other particles.
Interaction between them is governed by the Law Of Conservation Of Electric Charge, which states that total electric charge must remain constant in a particle interaction in the annihilation process. If a particle and its antiparticle have opposite electric charges, their combined electric charge is zero, satisfying the conservation of charge.
In our observable universe, matter is much more abundant than antimatter. This is known as matter-antimatter asymmetry problem, which remains an open question in particle physics.
Formation of Antimatter: 3 conditions regularly form antimatter, such as radioactive decay, extremely high temperatures, and high energy particle collisions.
Examples of antimatter are lightning, cosmic rays, potassium decay in bananas, black hole, aurora Borealis, solar flare, PET scan, etc.
Particle colliders have produced positrons, antiprotons, antineutrons, antinucleic, antihydrogen, antihelium.
Dark matter/ dark energy:
Dark matter is a hypothetical form of matter that accounts for approximately 85% of the matter in the universe. Most of the dark matter is composed of same-as-of-yet-undiscovered subatomic particles.
Dark energy + dark matter constitutes approximately 95.1% of the total content of the universe. Rest is normal matter.
Multiple components that make up our universe:
Dark matter (25%), dark energy (69%), atomic matter (5%), neutrinos (0.1%), Photons (0.01%), black holes (0.008%), etc.
Dark matter is referred to as dark because it does not interact with electromagnetic radiation, such as light. It is thus invisible or dark to the entire electromagnetic spectrum, making it extremely difficult to detect. It interacts with the rest of the universe only through gravity, and that’s how we know it exists.
Dark energy is a theoretical repulsive force that counteracts gravity and causes the universe to expand at an accelerating rate opposite of gravity rather than slowing down after the Big Bang. It comprises 68% of the universe, and very little is known about this mystery.
XENON-1T experiment is the world’s most sensitive dark matter experiment, was operated deep underground at INFN Laboratoryi Nationali del Gran Sasso, Italy. It uses dual-phase liquid gas XENON technique.
Other dark matter and energy experiments include LUX-ZEPLIN, a next-generation dark matter experiment located at Stanford, USA, and PANDA X-xT project in Jinping, China, at Jinping Underground Laboratory.
The difference between dark matter and dark energy are:
- DE is the single largest constituent of the universe, DM is the second largest.
- DE tends to drive the universe apart while DM tends to drive the universe together.
- DE does not interact with normal matter, DM does interact with normal matter through gravity (gravitational lensing)
- DE taken as the fifth fundamental force, DM isn’t antimatter or black holes.
Fundamentals of particle physics
Particle physics is a branch of physics associated with the study of elementary constituents of matter, radiation, and the interactions between them.
The study is instrumental in understanding of universe and its phenomenon, and theories such as event horizon, singularity, string theory, dark matter, dark energy, etc.
The standard model of particle physics assumes that everything in this world is made of a set of distinct elementary particles that can’t be divided any further.
In simpler terms, these particles are the building blocks of our universe. It explains how particles called quarks, which make up protons and neutrons, and leptons, which include electrons, make up all the known matter.
It also explains how force-carrying particles, which belong to a broader group of bosons, influence the quarks and leptons.
There are 17 known elementary particles, six leptons or electrons, six quarks, which combine to form hadrons, and five bosons.
There are four fundamental forces that govern the universe:
1. Electromagnetism, carried by protons and involves interaction of electric and magnetic fields.
2. Strong force, carried by gluons, binding together atomic nuclei to make them stable.
3. Weak force, carried by W and Z bosons, causing nuclear reactions that power our sun and other stars for billions of years.
4. Gravity, not adequately explained by the standard model.
Bosons are a combination of particles carrying forces. These were first discovered by the Indian scientist Satyendranath Bose, and later Peter Higgs further analyzed them. Satyendranath Bose, father of God particle, Higgs-Boson particle. These particles are present everywhere along with Higgs field, analogous to electric and magnetic field. These were experimentally proven in the Large Hadron Collider at CERN in 2013.
Large Hadron Collider is the world’s largest and most powerful particle accelerator. First started in 2018 at CERN, the European Council for Nuclear Research, located near Geneva, Swiss-France border. Set up in 1952, LHC is positioned in a channel with circumference of 27 km and the depth of 175 m. 27 km ring with superconducting magnets and accelerating structures. The accelerator is designed to collide opposite particle beams of either protons or lead nuclei, both hadrons, at very high energy. The hadrons are particles consisting of quarks. Other colliders are cyclotron, synchrotron, LHS, etc.
India and CERN: Since 1981, India is collaborating with CERN on LHS experiments and now granted observer status. Indian scientists and Indian made components were crucial in activating LHC much below the sanctioned cost.
Similar lab and experiments: Brookhaven National Lab, NYC, USA; Bell II Experiment, Super KEKB Particle Accelerator, Japan + BNL, USA.
Neutrinos: It’s a family of Leptons. Neutrinos are fermions that interact only via weak interaction in gravity. Fundamental particles that were first formed at the beginning of the early universe, even before atoms could form. Named so because they were electrically neutral and its rest mass is so small that it was thought to be zero. Neutrinos are produced in various neutral processes, nuclear reactions in the sun’s air, radioactive decay, supernova explosions, etc. Also created in particle accelerators and nuclear reactors. Study of neutrinos is crucial in understanding the fundamental properties of matter.
Antineutrinos: Antiparticle of neutrinos. They are also electrically neutral but have opposite Leptons flavors compared to their corresponding neutrinos. Their study provides insights into the nature of antimatter.
The Ice Cube Neutrino Observatory in the South Pole is designed to observe cosmos from deep within the South Pole ice.
The Indian Neutrino Observatory is India’s multi-institutional effort aimed at building a world-class underground lab with a rock cover for approx. 1200 meters for nuclear physics research in India. Especially to study neutrinos to be set up in a sensitive ecological zone in the western Ghats, Tamil Nadu and thus facing strong opposition and public agitation against the project.
