Wednesday, 10 January 2024
Tuesday, 19 December 2023
Monday, 18 July 2022
JAMES WEBB SPACE TELESCOPE
On 25th December 2021 Ariane 5 rocket carried a new space telescope that will replace Hubble. After nearly 25 years the idea which was once known as Next Generation Space Telescope (NGST) has finally set off. NGST is the name given for the successor of Hubble space telescope during 1996. Which was later changed to James Webb space telescope. After a 25-year wait the launch of the James Webb Space Telescope (JWST) is imminent, and the headline event of the year for the Astronomy community.
JWST is a remarkable feat
of engineering, one of the most complex instruments ever built, and will
demonstrate our capacity to operate new Space technologies at more than 1.5
million km from the Earth.
Australia will play a
critical role in tracking the Ariane 5 launch vehicle as it enters space, and
later the routine downloading of the science data eight hours a day from NASA’s
deep-space tracking station at Tidbinbilla, ACT. “The facility, built by NASA, ESA
(European Space Agency) and the Canadian Space Agency, is open to use by all
astronomers, regardless of nationality, and is destined to transform our
understanding of the Universe over the coming decade and beyond”, says Research
Professor Simon Driver.
The James Webb Space
Telescope (JWST) is a space telescope designed primarily to conduct infrared
astronomy. The most powerful telescope ever launched into space, its greatly
improved infrared resolution and sensitivity will allow it to view objects too
old, distant, and faint for the Hubble Space Telescope. This is expected to
enable a broad range of investigations across the fields of astronomy and
cosmology, such as observations of first stars and the formation of the first
galaxies, and detailed atmospheric characterization of potentially habitable
exoplanets. JWST was launched December 25, 2021 on an ESA Ariane 5 rocket from
Kourou, French Guiana, and as of April 2022 is undergoing testing and
alignment. Once operational, expected in May 2022, JWST is intended to succeed
the Hubble as NASA’s flagship mission in astrophysics.
The U.S. National
Aeronautics and Space Administration (NASA) led JWST’s development in
collaboration with the European Space Agency (ESA) and the Canadian Space
Agency (CSA). The NASA Goddard Space Flight Center (GSFC) in Maryland managed
telescope development, the Space Telescope Science Institute in Baltimore
operates JWST, and the prime contractor was Northrop Grumman. The telescope is
named after James E. Webb, who was the administrator of NASA from 1961 to 1968
during the Mercury, Gemini, and Apollo programs.
The Observatory
The Observatory is the
space-based portion of the James Webb Space Telescope system. It is comprised
of the Optical Telescope Element (OTE), the Integrated Science Instrument
Module (ISIM), the sunshield and the spacecraft bus.
The OTE is the eye of the
Observatory. It consists of the mirrors and the backplane. The OTE gathers the
light coming from space and provides it to the science instruments located in
the ISIM. The backplane is like the “spine” of Webb. It supports the mirrors. The
ISIM contains Webb’s cameras and instruments. It integrates four major
instruments and numerous subsystems into one payload. The sunshield separates
the observatory into a warm sun-facing side (spacecraft bus) and a cold
anti-sun side (OTE and ISIM). The sunshield keeps the heat of the Sun, Earth,
and spacecraft bus electronics away from the OTE and ISIM so that these pieces
of the Observatory can be kept very cold (The operating temperature has to be
kept under 50 K or -370 deg F). The spacecraft bus provides the support
functions for the operation of the Observatory. The bus houses the six major subsystems
needed to operate the spacecraft: the Electrical Power Subsystem, the Altitude
Control Subsystem, the Communication Subsystem, the Command and Data Handling
Subsystem, the Propulsion Subsystem, and the Thermal Control Subsystem.
The Predecessor
The Hubble Space
Telescope (often referred to as HST or Hubble) is a space telescope that was
launched into low Earth orbit in 1990 and remains in operation. It was not the
first space telescope, but it is one of the largest and most versatile, renowned
both as a vital research tool and as a public relations boon for astronomy. The
Hubble telescope is named after astronomer Edwin Hubble and is one of NASA’s
Great Observatories.
Space telescopes were
proposed as early as 1923, and the Hubble telescope was funded and built in the
1970s by the United States space agency NASA with contributions from the
European Space Agency. Its intended launch was 1983, but the project was beset
by technical delays, budget problems, and the 1986 Challenger disaster. Hubble
was finally launched in 1990, but its main mirror had been ground incorrectly,
resulting in spherical aberration that compromised the telescope’s capabilities.
The optics were corrected to their intended quality by a servicing mission in
1993.
Hubble is the only
telescope designed to be maintained in space by astronauts. Five Space Shuttle
missions have repaired, upgraded, and replaced systems on the telescope,
including all five of the main instruments. The fifth mission was initially cancelled
on safety grounds following the Columbia disaster (2003), but after NASA
administrator Michael D. Griffin approved it, it was completed in 2009. The
telescope completed 30 years of operation in April 2020 and is predicted to
last until 2030–2040.
Hubble forms the visible
light component of NASA’s Great Observatories program, along with the Compton
Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space
Telescope (which covers the infrared bands). The mid-IR to-visible band
successor to the Hubble telescope is the James Webb Space Telescope (JWST),
which was launched on December 25, 2021
In 1923, Hermann Oberth —
considered a father of modern rocketry, along with Robert H. Goddard and
Konstantin Tsiolkovsky — published Die Rakete zu den Planetenräumen (“The
Rocket into Planetary Space”), which mentioned how a telescope could be
propelled into Earth orbit by a rocket. The history of the Hubble Space
Telescope can be traced back as far as 1946, to astronomer Lyman Spitzer’s
paper entitled “Astronomical advantages of an extraterrestrial observatory”. In
it, he discussed the two main advantages that a space based observatory would
have over ground-based telescopes. First, the angular resolution (the smallest
separation at which objects can be clearly distinguished) would be limited only
by diffraction, rather than by the turbulence in the atmosphere, which causes
stars to twinkle, known to astronomers as seeing. At that time ground-based
telescopes were limited to resolutions of 0.5–1.0 arcseconds, compared to a
theoretical diffraction-limited resolution of about 0.05 arcsec for an optical telescope
with a mirror 2.5 m (8 ft 2 in) in diameter. Second, a space-based telescope
could observe infrared and ultraviolet light, which are strongly absorbed by
the atmosphere of Earth. Hubble has helped resolve some long-standing problems
in astronomy, while also raising new questions. Some results have required new
theories to explain them.
Age of the universe
Among its primary mission
targets was to measure distances to Cepheid variable stars more accurately than
ever before, and thus constrain the value of the Hubble constant, the measure
of the rate at which the universe is expanding, which is also related to its
age. Before the launch of HST, estimates of the Hubble constant typically had
errors of up to 50%, but Hubble measurements of Cepheid variables in the Virgo
Cluster and other distant galaxy clusters provided a measured value with an accuracy
of ±10%, which is consistent with other more accurate measurements made since
Hubble’s launch using other techniques. The estimated age is now about 13.7
billion years, but before the Hubble Telescope, scientists predicted an age ranging
from 10 to 20 billion years.
Expansion of the universe
While Hubble helped to
refine estimates of the age of the universe, it also cast doubt on theories
about its future. Astronomers from the High-z Supernova Search Team and the
Supernova Cosmology Project used ground-based telescopes and HST to observe distant
supernovae and uncovered evidence that, far from decelerating under the
influence of gravity, the expansion of the universe may in fact be
accelerating. Three members of these two groups have subsequently been awarded
Nobel Prizes for their discovery. The cause of this acceleration remains poorly
understood; the term.used for the currently-unknown cause is dark energy,
signifying that it is dark (unable to be directly seen and detected) to our
current scientific instruments
Supernova reappearance
On December 11, 2015,
Hubble captured an image of the first-ever predicted reappearance of a
supernova, dubbed “Refsdal”, which was calculated using different mass models
of a galaxy cluster whose gravity is warping the supernova’s light. The
supernova was previously seen in November 2014 behind galaxy cluster MACS
J1149.5+2223 as part of Hubble’s Frontier Fields program. Astronomers spotted
four separate images of the supernova in an arrangement known as an Einstein
Cross. The light from the cluster has taken about five billion years to reach
Earth, though the supernova exploded some 10 billion years ago. Based on early
lens models, a fifth image was predicted to reappear by the end of 2015. The detection
of Refsdal’s reappearance in December 2015 served as a unique opportunity for
astronomers to test their models of how mass, especially dark matter, is
distributed within this galaxy cluster.
In March 2019,
observations from Hubble and data from the European Space Agency’s Gaia space
observatory were combined to determine that the Milky Way Galaxy weighs
approximately 1.5 trillion solar units within a radius of 129,000 light years.
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| Milky Way Galaxy |
Other discoveries made with Hubble data include proto-planetary disks (proplyds) in the Orion Nebula; evidence for the presence of extrasolar planets around Sun-like stars; and the optical counterparts of the still-mysterious gamma-ray bursts. MACS 2129-1 is an early universe so-called ‘dead’ disk galaxy that lies approximately 10 billion light-years away from Earth. In 2022 Hubble detected the light of the farthest individual star ever seen to date. The star, named temporarily Earendel, existed within the first billion years after the big bang. It will be observed by NASA’s James Webb Space Telescope to confirm Earendel is indeed a star Impact on astronomy. Hubble is still working to capture image of universe below shows recent work of Hubble.
Herbig-Haro object is
located in the nebula NGC 1977, which itself is part of a complex of three
nebulae called The Running Man. NGC 1977 – like its companions NGC 1975 and NGC
1973 – is a reflection nebula, which means that it doesn’t emit light on its
own, but reflects light from nearby stars, like a streetlight illuminating fog.
Hubble observed this region to look for stellar jets and planet-forming disks
around young stars, and examine how their environment affects the evolution of
such disks.
Difference in lens
The lenses of James Webb
and Hubble are based on different theory. In Hubble optically, the HST is a
Cassegrain reflector of Ritchey–Chrétien design, as are most large professional
telescopes. This design, with two hyperbolic mirrors, is known for good imaging
performance over a wide field of view, with the disadvantage that the mirrors
have shapes that are hard to fabricate and test. The mirror and optical systems
of the telescope determine the final performance, and they were designed to
exacting specifications. Optical telescopes typically have mirrors polished to
an accuracy of about a tenth of the wavelength of visible light, but the Space
Telescope was to be used for observations from the visible through the
ultraviolet (shorter wavelengths) and was specified to be diffraction limited
to take full advantage of the space environment. Therefore, its mirror needed
to be polished to an accuracy of 10 nanometres, or about 1/65 of the wavelength
of red light. On the long wavelength end, the OTA was not designed with optimum
IR performance in mind—for example, the mirrors are kept at stable (and warm,
about 15 °C) temperatures by heaters. This limits Hubble’s performance as an
infrared telescope. Within weeks of the launch of the telescope, the returned
images indicated a serious problem with the optical system. Although the first
images appeared to be sharper than those of ground-based telescopes, Hubble
failed to achieve a final sharp focus and the best image quality obtained was
drastically lower than expected. Images of point sources spread out over a
radius of more than one arc second, instead of having a point spread function
(PSF) concentrated within a circle 0.1 arc seconds (485 nrad) in diameter, as
had been specified in the design criteria.
Analysis of the flawed
images revealed that the primary mirror had been polished to the wrong shape.
Although it was believed to be one of the most precisely figured optical
mirrors ever made, smooth to about 10 nanometres, the outer perimeter was too
flat by about 2200 nanometres (about 1⁄450 mm or 1⁄11000 inch). This difference
was catastrophic, introducing severe spherical aberration, a flaw in which
light reflecting off the edge of a mirror focuses on a different point from the
light reflecting off its centre.
The effect of the mirror
flaw on scientific observations depended on the particular observation—the core
of the aberrated PSF was sharp enough to permit high-resolution observations of
bright objects, and spectroscopy of point sources was affected only through a
sensitivity loss. However, the loss of light to the large, out-of-focus halo
severely reduced the usefulness of the telescope for faint objects or
high-contrast imaging. This meant nearly all the cosmological programs were essentially
impossible, since they required observation of exceptionally faint objects.
This led politicians to question NASA’s competence, scientists to rue the cost
which could have gone to more productive endeavors, and comedians to make jokes
about NASA and the telescope. In the 1991 comedy The Naked Gun 2½: The Smell of
Fear, in a scene where historical disasters are displayed, Hubble is pictured
with RMS Titanic and LZ 129 Hindenburg. Nonetheless, during the first three years
of the Hubble mission, before the optical corrections, the telescope still
carried out a large number of productive observations of less demanding
targets. The error was well characterized and stable, enabling astronomers to
partially compensate for the defective mirror by using sophisticated image
processing techniques such as deconvolution. JWST’s primary mirror is a 6.5 m
(21 ft)-diameter gold-coated beryllium reflector with a collecting area of 25.4
m2 (273 sq ft). If it were built as a single large mirror, this would have been
too large for existing launch vehicles. The mirror is therefore composed of 18
hexagonal segments (Guido Horn d’Arturo’s multi-mirror telescope), which
unfolded after the telescope was launched. Image plane wavefront sensing
through phase retrieval is used to position the mirror segments in the correct
location using very precise micromotors. Subsequent to this initial
configuration, they only need occasional updates every few days to retain optimal
focus. This is unlike terrestrial telescopes, for example the Keck telescopes,
which continually adjust their mirror segments using active optics to overcome
the effects of gravitational and wind loading.
The Webb telescope will
use 132 small motors (called actuators) to position and occasionally adjust the
optics as there are few environmental disturbances of a telescope in space.
Each of the 18 primary mirror segments is controlled by 6 positional actuators
with a further ROC (radius of curvature) actuator at the center to adjust
curvature (7 actuators per segment), for a total of 126 primary mirror
actuators, and another 6 actuators for the secondary mirror, giving a total of
132. The actuators can position the mirror with 10 nanometre (10 millionths of
a millimetre) accuracy.
The actuators are
critical in maintaining the alignment of the telescope’s mirrors, and are
designed and manufactured by Ball Aerospace & Technologies. Each of the 132
actuators are driven by a single stepper motor, providing both fine and coarse
adjustmentst. The actuators provide a coarse step size of 58 nanometers for
larger adjustments, and a fine adjustment step size of 7 nanometres.
JWST’s optical design is
a three-mirror anastigmat, which makes use of curved secondary and tertiary mirrors
to deliver images that are free from optical aberrations over a wide field. The
secondary mirror is 0.74 m (2.4 ft) diameter. In addition, there is a fine
steering mirror which can adjust its position many times per second to provide
image stabilization. The primary mirror segments are hollowed at the rear in a honeycomb
pattern, to reduce weight.
Ball Aerospace &
Technologies is the principal optical subcontractor for the JWST project, led
by prime contractor Northrop Grumman Aerospace Systems, under a contract from
the NASA Goddard Space Flight Center, in Greenbelt, Maryland. The mirrors, plus
flight spares, were fabricated and polished by Ball Aerospace &
Technologies based on beryllium segment blanks manufactured by several
companies including Axis’s, Brush Wellman, and Tinsley Laboratories.
Orbit’s of James Webb and Hubble
The Earth is 150 million
km from the Sun and the moon orbits the earth at a distance of approximately 384,500
km. The Hubble Space Telescope orbits around the Earth at an altitude of ~570
km above it. Webb will not actually orbit the Earth - instead it will sit at
the Earth-Sun L2 Lagrange point, 1.5 million km away! Webb will orbit the sun
1.5 million kilometers (1 million miles) away from the Earth at what is called
the second Lagrange point or L2. (Note that these graphics are not to scale.) Because
Hubble is in Earth orbit, it was able to be launched into space by the space
shuttle. Webb will be launched on an Ariane 5 rocket and because it won't be in
Earth orbit, it is not designed to be serviced by the space shuttle.
At the L2 point Webb's
solar shield will block the light from the Sun, Earth, and Moon. This will help
Webb stay cool, which is very important for an infrared telescope. As the Earth
orbits the Sun, Webb will orbit with it - but stay fixed in the same spot with
relation to the Earth and the Sun, as shown in the diagram to the left.
Actually, satellites orbit around the L2 point, as you can see in the diagram -
they don't stay completely motionless at a fixed spot.
 |
| Webb will orbit the sun 1.5 million kilometers (1 million miles) away from the Earth at what is called the second Lagrange point or L2. (Note that these graphics are not to scale.) |
 |
| Lagrange Points. |
Hubble had a mission to
discover the vast universe. Humanity has taken first step to explore the
universe using Hubble now there might be a leap in this because of James Webber.
On the day of launch the James Webb Twitter account tweeted with # unfold the
universe. This shows the ambition and resolution to uncover the universe. Because
of the time it takes light to travel, the farther away an object is, the
farther back in time we are looking.
Essentially, Hubble can see the equivalent of "toddler galaxies" and Webb Telescope will be able to see "baby galaxies". One reason Webb will be able to see the first galaxies is because it is an infrared telescope. The universe (and thus the galaxies in it) is expanding. When we talk about the most distant objects, Einstein's General Relativity actually comes into play. It tells us that the expansion of the universe means it is the space between objects that actually stretches, causing objects (galaxies) to move away from each other. Furthermore, any light in that space will also stretch, shifting that light's wavelength to longer wavelengths. This can make distant objects very dim (or invisible) at visible wavelengths of light, because that light reaches us as infrared light. Infrared telescopes, like Webb, are ideal for observing these early galaxies NASA has announced that it will unveil the first science-quality images from the James Webb Space Telescope on July 12 which will show us the potential of James Webb and the future path astrophysics will take.
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| The James Webb Space Telescope reveals stellar nurseries and individual stars in the Carina Nebula that had not been seen before. |
Submitted by 1st Year M.Sc. Students
Niroop B, Pallavi, Kushmitha AP, Parinith M
Wednesday, 6 April 2022
Touch Screen Technology
Inside cell phone:
A Touch screen is an
electronic visual display capable of detecting and locating a touch over its
display area. This means, touching the display of the device with a finger or
hand. This technology most widely used in computers, user interactive machines,
smartphones, tablets, etc. to replace most functions of the mouse and keyboard.
The three most common touch screen technologies include resistive, capacitive, and SAW (surface acoustic wave). Most low-end touch screen devices contain a standard printed circuit plug-in board and are used on SPI protocol. The system has two parts, namely; hardware and software. The hardware architecture consists of a stand-alone embedded system using an 8-bit microcontroller, several types of interface, and driver circuits. The system software driver is developed using an interactive C programming language.
Touch Screen Technology
A touch screen technology
is the assembly of a touch panel as well as a display device. Generally, a
touch panel is covered on an electronic visual display within a processing
system. Here the display is an LCD otherwise OLED whereas the system is
normally like a smartphone, tablet, or laptop. A consumer can give input
through simple touch gestures by moving the screen using a special stylus
otherwise fingers. In this way touch screen allows the operator to
communicate directly through the displayed information instead of using a
touchpad, mouse, etc.
Who Invented Touch Screen?
The first concept of a touch screen was described & published in the year 1965 by E.A. Johnson. So, the first touch screen was developed in the 1970s by CERN engineers. Bent Stumpe built in 1972, following an idea launched by Frank Beck, a capacitive touchscreen for controlling CERN's Super Proton Synchrotron accelerator. In 1973 Beck and Stumpe published a CERN report, outlining the concept for a prototype touchscreen as well as a multi-function computer-configurable knob. The first resistive touch screen was designed in 1975 by George Samuel Hurst.
How Does Touch Screen Technology Work?
Different types of
touchscreen technology work in different methods. Some can detect simply one
finger at a time & get very confused if you seek to push in two positions
at once. Other types of screens can simply notice and differentiate above one
key push at once.
Operation of Touch Screen Panel
A basic touch screen is
having a touch sensor, a controller, and a software driver as three main
components. The touch screen is needed to be combined with a display and a PC
to make a touch screen system.
Operation of touch screen panel
Touch Sensor
The sensor generally has
an electrical current or signal going through it and touching the screen causes
a change in the signal. This change is used to determine the location of the
touch of the screen.
Controller
A controller will be
connected between the touch sensor and PC. It takes information from the sensor
and translates it for the understanding of PC. The controller determines what
type of connection is needed.
Software Driver
It allows computers and
touch screens to work together. It tells OS how to interact with the touch
event information that is sent from the controller.
Types of Touch Screen Technology
The Touch screen is a
2-dimensional sensing device made of 2 sheets of material separated by spacers.
There are four main touch screen technologies: Resistive, Capacitive, Surface
Acoustical wave (SAW), and infrared (IR).
Resistive
Resistive touchscreens
(currently the most popular technology) work a bit like "transparent
keyboards" overlaid on top of the screen. There's a flexible upper layer
of conducting polyester plastic bonded to a rigid lower layer of conducting
glass and separated by an insulating membrane. When you press on the screen,
you force the polyester to touch the glass and complete a circuit—just like
pressing the key on a keyboard. A chip inside the screen figures out the
coordinates of the place you touched.
These screens are made
from multiple layers of glass. The inner layer conducts electricity and so does
the outer layer, so effectively the screen behaves like two electrical
conductors separated by an insulator—in other words, a capacitor. When you
bring your finger up to the screen, you alter the electrical field by a certain
amount that varies according to where your hand is. Capacitive screens can be
touched in more than one place at once. Unlike most other types of touchscreens,
they don't work if you touch them with a plastic stylus (because the plastic is
an insulator and stops your hand from affecting the electric field).
Infrared
Just like the magic eye
beams in an intruder alarm, an infrared touchscreen uses a grid pattern of LEDs
and light-detector photocells arranged on opposite sides of the screen. The
LEDs shine infrared light in front of the screen—a bit like an invisible
spider's web. If you touch the screen at a certain point, you interrupt two or
more beams. A microchip inside the screen can calculate where you touched by
seeing which beams you interrupted. The touchscreen on Sony Reader ebooks (like
the one pictured in our photo below) works this way. Since you're interrupting
a beam, infrared screens work just as well whether you use your finger or a
stylus.
Surface Acoustic Wave
Surprisingly, this
touchscreen technology detects your fingers using sound instead of light.
Ultrasonic sound waves (too high pitched for humans to hear) are generated at
the edges of the screen and reflected back and forth across its surface. When
you touch the screen, you interrupt the sound beams and absorb some of their
energy. The screen's microchip controller figures out from this where exactly
you touched the screen.
Near field imaging
Have you noticed how an
old-style radio can buzz and whistle if you move your hand toward it? That's
because your body affects the electromagnetic field that incoming radio waves
create in and around the antenna. The closer you get, the more effect you have.
Near field imaging (NFI) touchscreens work a similar way. As you move your
finger up close, you change the electric field on the glass screen, which
instantly registers your touch. Much more robust than some of the other
technologies, NFI screens are suitable for rough-and-tough environments (like
military use). Unlike most of the other technologies, they can also detect
touches from pens, styluses, or hands wearing gloves.
Pratheeksha
Preetham
Sushmitha
Soujanya
Vaishnavi.M
I M Sc. Physics
I M Sc. Physics
Monday, 14 February 2022
FUTURE NUCLEAR REACTOR
Molten Salt Reactor:
A molten salt reactor (MSR) is a class of nuclear fission reactor in
which the primary nuclear reactor
coolant and the fuel is a molten salt mixture. MSR's are considered safer than conventional reactors because they operate
with fuel already in a molten state and in event of an emergency the fuel mixture is designed to drain from the
core where it will solidify, preventing the type of nuclear meltdown and associated hydrogen explosions (
like what happened in the Fukushima nuclear disaster bracket ) that are at risk
in conventional reactors. They
operate at or close to atmospheric pressure, rather than the 75 to 150 times atmospheric pressure of a
typical light water reactor (LWR), hence reducing the need for a large expensive reactor pressure vessels used in light water reactors. A further key characteristic of MSRs is operating temperatures of around 700 °C (1,292 °F), significantly higher than traditional LWRs at around 300 °C (572 °F), providing greater electricity-generation efficiency.
Magnetic Confinement Fusion:
Magnetic confinement fusion is an approach to generate thermonuclear fusion power that uses magnetic fields to confine fusion fuel in the form of a plasma. Magnetic confinement is one of two major branches of fusion energy research along with inertial confinement fusion. Fusion reactions combine light atomic nuclei such as hydrogen to form heavier ones such as helium producing energy. In order to overcome the electrostatic repulsion between the nuclei, they must have a temperature of tens of millions of degrees creating a plasma in addition, the plasma must be contained at a sufficient density for a sufficient time, as specified by the Lawson criterion ( triple product )
Inertial Confinement Fusion:
Inertial confinement fusion (ICF) is a fusion energy research program that initiates nuclear fusion reactions by compressing and heating targets filled with thermonuclear fuel. These are pellets typically containing a mixture of deuterium 2H and tritium 3H. In current experimental reactors, fuel pellets are about the size of a pinhead and contain around 10 milligrams of fuel. Bigger power reactors are envisaged for the future as affordable, safe, clean, carbon-free energy sources of limitless scale that burn deuterium, which is plentiful in the oceans. To compress and heat the fuel, energy is deposited in the outer layer of the target using high-energy beams of photons, electrons or ions, although almost all ICF devices as of 2020 used lasers. The largest operational ICF experiment is the National Ignition Facility (NIF) in the US. In 2021, an experiment reached 70% efficiency.
Small Modular Reactor:
Small modular reactors (SMRs) are nuclear fission reactors that are smaller than conventional nuclear reactors and typically have an electrical power output of less than 300 MWe or a thermal power output of less than 1000 MWth. They are designed to be manufactured at a plant and transported to a site to be installed. Modular reactors will reduce on-site construction and increase containment efficiency and are claimed to enhance safety. The greater safety should come via the use of passive safety features that operate without human intervention, a concept already implemented in some conventional nuclear reactor types. SMRs also reduce staffing versus conventional nuclear reactors. SMRs are claimed to cross financial and safety barriers that inhibit the construction of conventional reactors.
Reference:-
Wikipedia and online sources
SUBMITTED BY:-
First M.Sc. Physics Students: Chaithashree K, Deeksha H, Harshitha K, Krithi A
St. Philomena College, Centre for PG Studies and Research, Puttur
Tuesday, 23 March 2021
Nobel 2020
Introduction: 
Nobel Prizes are awarded in the
fields of Physics, Chemistry, Physiology or Medicine, Literature, and Peace. Nobel Prizes are widely regarded as the most prestigious awards available in
their respective fields.
Alfred
Nobel was a Swedish Chemist, Engineer and Industrialist most famously known
for the invention of dynamite. He died in 1896. In his will, he bequeathed all
of his "remaining realisable assets" to be used to establish five
prizes which became known as "Nobel Prizes". Nobel Prizes were first
awarded in 1901.
The prize ceremonies take place annually. Each recipient receives a gold medal, a diploma, and a monetary award. In 2020, the Nobel Prize monetary award is 10,000,000. A prize may not be shared among more than three individuals.
Three Laureates share this year’s Nobel Prize in Physics for their discoveries about one of the most exotic phenomena in the universe, the black hole. Roger Penrose showed that the general theory of relativity leads to the formation of black holes. Reinhard Genzel and Andrea Ghez discovered that an invisible and extremely heavy object governs the orbits of stars at the centre of our galaxy. A supermassive black hole is the only currently known explanation.
Roger Penrose used ingenious mathematical methods in his proof that
black holes are a direct consequence of Albert Einstein’s general theory of relativity. Einstein did not himself believe
that black holes really exist, these super-heavyweight monsters that capture
everything that enters them. Nothing can escape, not even light.
In January 1965, ten years after Einstein’s death, Roger Penrose proved that black holes really can form and described them in detail; at their heart, black holes hide a singularity in which all the known laws of nature cease. His groundbreaking article is still regarded as the most important contribution to the general theory of relativity since Einstein.
Sir Roger Penrose
Sir Roger Penrose is a British Mathematical Physicist, Mathematician, Philosopher of Science and Nobel Laureate in Physics. He is Emeritus Rouse Ball Professor of Mathematics at the University of Oxford, an emeritus fellow of Wadham College, Oxford and an honorary fellow of St John's College, Cambridge and University College London.
Penrose has
made contributions to the Mathematical Physics of general relativity and
cosmology. He has received several prizes and awards, including the 1988 Wolf
Prize in Physics, which he shared with Stephen Hawking for the Penrose–Hawking
singularity theorems, and one half of the 2020 Nobel Prize in Physics
"for the discovery that black hole formation is a robust prediction of the
general theory of relativity".
Reinhard Genzel and Andrea Ghez each lead a group of astronomers that, since the early 1990s, has focused on a region called Sagittarius A* at the centre of our galaxy. The orbits of the brightest stars closest to the middle of the Milky Way have been mapped with increasing precision. The measurements of these two groups agree, with both finding an extremely heavy, invisible object that pulls on the jumble of stars, causing them to rush around at dizzying speeds. Around four million solar masses are packed together in a region no larger than our solar system.
Using the world’s largest telescopes, Genzel and Ghez developed methods to see through the huge clouds of interstellar gas and dust to the centre of the Milky Way. Stretching the limits of technology, they refined new techniques to compensate for distortions caused by the Earth’s atmosphere, building unique instruments and committing themselves to long-term research. Their pioneering work has given us the most convincing evidence yet of a supermassive black hole at the centre of the Milky Way.
Andrea Mia Ghez
Andrea Mia Ghez is an American Astronomer and Professor in the Department of Physics and Astronomy at the
University of California, Los Angeles. Her research focuses on the center of
the Milky Way galaxy. In 2020, she became the fourth woman to be awarded the
Nobel Prize in Physics, sharing one half of the prize with Reinhard Genzel the
other half of the prize being awarded to Roger Penrose. The Nobel Prize was
awarded to Ghez and Genzel for their discovery of a supermassive compact
object, now generally recognized to be a black hole, in the Milky Way's
galactic center.
Reinhard Genzel
Reinhard Genzel is a German Astrophysicist, Co-director of the Max Planck Institute for Extraterrestrial Physics, a Professor at LMU and an Emeritus Professor at the University of California, Berkeley. He was awarded the 2020 Nobel Prize in Physics "for the discovery of a supermassive compact object at the centre of our galaxy", which he shared with Andrea Ghez and Roger Penrose. Reinhard Genzel studies infrared- and submillimeter astronomy. He and his group are active in developing ground- and space-based instruments for astronomy. They used these to track the motions of stars at the centre of the Milky Way, around Sagittarius A*, and show that they were orbiting a very massive object, now known to be a black hole. Genzel is also active in studies of the formation and evolution of galaxies.
Black Hole
Black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole.
The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, according to general relativity it has no locally detectable features. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe directly.
Albert Einstein
Albert
Einstein was a German-born Theoretical Physicist, widely acknowledged to be
one of the greatest Physicists of all time. Einstein is known widely for
developing the theory of relativity, but he also made important contributions
to the development of the theory of quantum mechanics. Relativity and quantum
mechanics are together the two pillars of modern physics. His mass–energy
equivalence formula,
which arises from relativity theory, has been
dubbed "the world's most famous equation". His work is also known for
its influence on the Philosophy of Science. He received the 1921 Nobel Prize in
Physics "for his services to theoretical physics, and especially for his
discovery of the law of the photoelectric effect" a pivotal step in the
development of quantum theory. His intellectual achievements and originality
resulted in "Einstein" becoming synonymous with "genius".
Amal Kumar Raychaudhuri
Amal Kumar Raychaudhuri was an Indian Physicist, known for his research in general relativity and cosmology. His most significant contribution is the eponymous Raychaudhuri equation, which demonstrates that singularities arise inevitably in general relativity and is a key ingredient in the proofs of the Penrose–Hawking singularity theorems.
Raychaudhuri
was also revered as a teacher during his tenure at Presidency College, Kolkata.
Many of his students have gone on to become established Scientists.
Stephen William Hawking
Stephen William Hawking was an
English Theoretical Physicist, Cosmologist, and author who was director of
research at the Centre for Theoretical Cosmology at the University of Cambridge
at the time of his death. He was the Lucasian Professor of Mathematics at the
University of Cambridge between 1979 and 2009.
Hawking's scientific works included a
collaboration with Roger Penrose on gravitational singularity theorems in the
framework of general relativity and the theoretical prediction that black holes
emit radiation, often called Hawking radiation. Initially, Hawking radiation
was controversial.
General Relativity:
General relativity, also known as the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations.
Some predictions of general relativity differ significantly from those of classical physics, especially concerning the passage of time, the geometry of space, the motion of bodies in free fall, and the propagation of light. Examples of such differences include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the gravitational time delay and singularities/black holes.
Einstein's theory has important astrophysical implications. For example, it implies the existence of black holes—regions of space in which space and time are distorted in such a way that nothing, not even light, can escape—as an end-state for massive stars. There is ample evidence that the intense radiation emitted by certain kinds of astronomical objects is due to black holes. For example, micro quasars and active galactic nuclei result from the presence of stellar black holes and supermassive black holes, respectively.
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