The movies promise to give astronomers a better understanding of how active black holes shape galaxy evolution. While matter drawn completely into a black hole cannot escape its enormous gravitational pull, most infalling material drawn toward it first joins an orbiting region known as an accretion disk encircling the black hole. Magnetic fields surrounding the black hole are thought to entrain some of this ionized gas, ejecting it as very high-velocity jets.

"Central supermassive black holes are a key component in all big galaxies," said Eileen T. Meyer of the Space Telescope Science Institute (STScI) in Baltimore, Md., the Hubble study's lead author. "Most of these black holes are believed to have gone through an active phase, and black-hole-powered jets from this active phase play a key role in the evolution of galaxies. By studying the details of this process in the nearest galaxy with an optical jet, we can hope to learn more about galaxy formation and black hole physics in general."

The Hubble movies reveal for the first time that the jet's river of plasma travels in a spiral motion. This motion is considered strong evidence that the plasma may be traveling along a magnetic field, which the team thinks is coiled like a helix. The magnetic field is believed to arise from a spinning accretion disk of material around a black hole. Although the magnetic field cannot be seen, its presence is inferred by the confinement of the jet along a narrow cone emanating from the black hole.

"We analyzed several years' worth of Hubble data of a relatively nearby jet, which allowed us to see lots of details," Meyer said. "The only reason you see the distant jet in motion at all over just a few years is because it is traveling very fast."

Meyer found evidence for the magnetic field's suspected helical structure in several locations along the jet. In the outer part of the M87 jet, for example, one bright gas clump, called knot B, appears to zigzag, as if it were moving along a spiral path. Several other gas clumps along the jet also appear to loop around an invisible structure. "Past observations of black hole jets couldn't distinguish between radial motion and side-to-side motion, so they didn't provide us with detailed information of the jet's behavior," Meyer explained.

M87 resides at the center of the neighboring Virgo cluster of roughly 2,000 galaxies, located 50 million light-years away. The galaxy's monster black hole is several billion times more massive than our Sun.

In addition, the Hubble data provided information on why the jet is composed of a long string of gas blobs, which appear to brighten and dim over time.

"The jet structure is very clumpy. Is this a ballistic effect, like cannonballs fired sequentially from a cannon?" Meyer asked. "Or, is there some particularly interesting physics going on, such as a shock that is magnetically driven?"

Meyer's team found evidence for both scenarios. "We found things that move quickly," Meyer said. "We found things that move slowly. And, we found things that are stationary. This study shows us that the clumps are very dynamic sources."

The research team spent eight months analyzing 400 observations from Hubble's Wide Field Planetary Camera 2 and Advanced Camera for Surveys. The observations were taken from 1995 to 2008. Several team members, however, have been observing M87 for 20 years. Only Hubble's sharp vision allowed the research team to measure the jet's slight motion in the sky over 13 years. Meyer's team also measured features in the hot plasma as small as 20 light-years wide.

It's too soon to tell whether all black-hole-powered jets behave like the one in M87. That's why Meyer plans to use Hubble to study three more jets. "It's always dangerous to have exactly one example because it could be a strange outlier," Meyer said. "The M87 black hole is justification for looking at more jets."

Functional MRI scanners have been used in cognition research primarily to determine which brain areas are active while test subjects perform a specific task. The question is simple: is a particular brain region on or off? A research group at the Donders Institute for Brain, Cognition and Behaviour at Radboud University has gone a step further: they have used data from the scanner to determine what a test subject is looking at.
The researchers 'taught' a model how small volumes of 2x2x2 mm from the brain scans -- known as voxels -- respond to individual pixels. By combining all the information about the pixels from the voxels, it became possible to reconstruct the image viewed by the subject. The result was not a clear image, but a somewhat fuzzy speckle pattern. In this study, the researchers used hand-written letters.

Prior knowledge improves model performance

'After this we did something new', says lead researcher Marcel van Gerven. 'We gave the model prior knowledge: we taught it what letters look like. This improved the recognition of the letters enormously. The model compares the letters to determine which one corresponds most exactly with the speckle image, and then pushes the results of the image towards that letter. The result was the actual letter, a true reconstruction.'

'Our approach is similar to how we believe the brain itself combines prior knowledge with sensory information. For example, you can recognise the lines and curves in this article as letters only after you have learned to read. And this is exactly what we are looking for: models that show what is happening in the brain in a realistic fashion. We hope to improve the models to such an extent that we can also apply them to the working memory or to subjective experiences such as dreams or visualisations. Reconstructions indicate whether the model you have created approaches reality.'

Improved resolution; more possibilities
'In our further research we will be working with a more powerful MRI scanner,' explains Sanne Schoenmakers, who is working on a thesis about decoding thoughts. 'Due to the higher resolution of the scanner, we hope to be able to link the model to more detailed images. We are currently linking images of letters to 1200 voxels in the brain; with the more powerful scanner we will link images of faces to 15,000 voxels.'

Researchers at MIT have discovered an Earth-sized exoplanet named Kepler 78b that whips around its host star in a mere 8.5 hours -- one of the shortest orbital periods ever detected. The planet is extremely close to its star -- its orbital radius is only about three times the radius of the star -- and the scientists have estimated that its surface temperatures may be as high as 3,000 degrees Kelvin, or more than 5,000 degrees Fahrenheit. In such a scorching environment, the top layer of the planet is likely completely melted, creating a massive, roiling ocean of lava.

What's most exciting to scientists is that they were able to detect light emitted by the planet -- the first time that researchers have been able to do so for an exoplanet as small as Kepler 78b. This light, once analyzed with larger telescopes, may give scientists detailed information about the planet's surface composition and reflective properties.

Kepler 78b is so close to its star that scientists hope to measure its gravitational influence on the star. Such information may be used to measure the planet's mass, which could make Kepler 78b the first Earth-sized planet outside our own solar system whose mass is known.

The researchers reported their discovery of Kepler 78b in The Astrophysical Journal.In a separate paper, published in Astrophysical Journal Letters, members of that same group, along with others at MIT and elsewhere, observed KOI 1843.03, a previously discovered exoplanet with an even shorter orbital period: just 4 1/4 hours. The group, led by physics professor emeritus Saul Rappaport, determined that in order for the planet to maintain its extremely tight orbit around its star, it would have to be incredibly dense, made almost entirely of iron -- otherwise, the immense tidal forces from the nearby star would rip the planet to pieces.

"Just the fact that it's able to survive there implies that it's very dense," says Josh Winn, an associate professor of physics at MIT, and co-author on both papers. "Whether nature actually makes planets that are dense enough to survive even closer in, that's an open question, and would be even more amazing."

In their discovery of Kepler 78b, the team that wrote the Astrophysical Journal paper looked through more than 150,000 stars that were monitored by the Kepler Telescope, a NASA space observatory that surveys a slice of the galaxy. Scientists are analyzing data from Kepler in hopes of identifying habitable, Earth-sized planets.The goal for Winn and his colleagues was to look for Earth-sized planets with very short orbital periods.

"We've gotten used to planets having orbits of a few days," Winn says. "But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there."

To find them, the team analyzed light data from thousands of stars, looking for telltale dips indicating that a planet may periodically pass in front of a star.

Picking out these tiny dips among tens of thousands of light curves is typically a time-intensive ordeal. To speed the process along, the group devised a more automated approach, applying a basic mathematical method known as the Fourier transform to the large dataset. The method essentially whittles the field to those light curves that are periodic, or that exhibit a repetitive pattern.

Stars that host orbiting planets may display periodic dips of light each time a planet crosses, or transits, the star. But there are other periodic stellar phenomena that can affect light emission, such as a star eclipsing another star. To pick out those signals associated with actual planets, physics graduate student Roberto Sanchis-Ojeda searched through the set of periodic light curves, looking for frequent smaller dips in the data midway between the planetary transits.

The group was able to detect the light given off by the planet by measuring the amount by which the overall light dimmed each time the planet passed behind the star. The researchers posit that the planet's light is possibly a combination of radiation from its heated surface and light reflected by surface materials, such as lava and atmospheric vapor.

"I was just looking by eye, and all of a sudden I see this extra drop of light right when it was expected, and it was really beautiful," Sanchis-Ojeda recalls. "I thought, we're actually seeing the light from the planet. It was a really exciting moment."

From their measurements of Kepler 78b, the team determined that the planet is about 40 times closer to its star than Mercury is to our sun. The star around which Kepler 78b orbits is likely relatively young, as it rotates more than twice as fast as the sun -- a sign that the star has not had as much time to slow down.
While it is about the size of Earth, Kepler 78b is most certainly not habitable, due to its extreme proximity to its host star."You'd have to really stretch your imagination to imagine living on a lava world," Winn says. "We certainly wouldn't survive there."But this doesn't entirely rule out the possibility of other habitable, short-period planets. Winn's group is now looking for exoplanets that orbit brown dwarfs -- cold, almost-dead stars that somehow failed to ignite.

"If you're around one of those brown dwarfs, then you can get as close in as just a few days," Winn says. "It would still be habitable, at the right temperature."

This fossil find -- the oldest ancestor in the multituberculate family tree -- represents a newly discovered species known as Rugosodon eurasiaticus. The nearly complete skeleton provides critical insights into the traits that helped such multituberculates thrive in their day. For example, the fossil reveals teeth that were adapted to gnawing plants and animals alike, as well as ankle joints that were highly adept at rotation.

In light of these findings, researchers suggest that R. eurasiaticus paved the way for later plant-eating and tree-dwelling mammals.Chong-Xi Yuan from the Chinese Academy of Geological Sciences in Beijing, China, along with Chinese and American colleagues, report their analysis of the fossil in the 16 August issue of Science.

The multituberculates flourished during the Cretaceous era, which ended over 60 million years ago. Much like today's rodents, they filled an extremely wide variety of niches -- below the ground, on the ground and in the trees -- and this new fossil, which resembles a small rat or a chipmunk, possessed many of the adaptations that subsequent species came to rely upon, the researchers say.

"The later multituberculates of the Cretaceous [era] and the Paleocene [epoch] are extremely functionally diverse: Some could jump, some could burrow, others could climb trees and many more lived on the ground," explained Zhe-Xi Luo, a co-author of the Science report. "The tree-climbing multituberculates and the jumping multituberculates had the most interesting ankle bones, capable of 'hyper-back-rotation' of the hind feet."

"What is surprising about this discovery is that these ankle features were already present in Rugosodon -- a land-dwelling mammal," he said. (Such highly mobile ankle joints are normally associated with the foot functions of animals that are exclusively tree-dwellers -- those that navigate uneven surfaces.)

Additionally, R. eurasiaticus could eat many different types of food, according to the researchers. The fossil -- particularly its dentition, which reveals teeth designed for shearing plant matter -- confirms a 2012 analysis of tooth types that suggested multituberculates consumed an animal-dominated diet for much of their existence, later diversifying to a plant-dominated one.

Multituberculates arose in the Jurassic period and went extinct in the Oligocene epoch, occupying a diverse range of habitats for more than 100 million years before they were out-competed by more modern rodents. By the end of their run on the planet, multituberculates had evolved complex teeth that allowed them to enjoy vegetarian diets and unique locomotive skills that enabled them to traverse treetops. Both adaptations helped them to become dominant among their contemporaries.

The fossilized R. eurasiaticus that Yuan and his team unearthed was preserved in lake sediments, suggesting that the creature may have lived on the shores. However, the researchers say that the ankle joints of this early multituberculate were already highly mobile and its teeth were already oriented for an omnivorous diet. Based on their findings, the researchers suggest that such adaptations must have arisen very early in the evolution of the order, setting the stage for the major diversification of rodent-like mammals that ensued.

The discovery of R. eurasiaticus also extends the distribution of certain multituberculates from Europe to Asia during the Late Jurassic period, the researchers say.

"This new fossil from eastern China is very similar to the Late Jurassic fossil teeth of multituberculates from Portugal in western Europe," explained Dr. Luo. "This suggests thatRugosodon and its closely related multituberculates had a broad paleogreographic distribution and dispersals back-and-forth across the entire Eurasian continent."

Carrying Earthly greetings on a gold plated phonograph record and still-operational scientific instruments -- including the Low Energy Charged Particle detector designed, built and overseen, in part, by UMD's Space Physics Group -- NASA's Voyager 1 has traveled farther from Earth than any other human-made object. And now, these researchers say, it has begun the first exploration of our galaxy beyond the Sun's influence.

"It's a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way," says UMD research scientist Marc Swisdak, lead author of a new paper published online this week in The Astrophysical Journal Letters. Swisdak and fellow plasma physicists James F. Drake, also of the University of Maryland, and Merav Opher of Boston University have constructed a model of the outer edge of the Solar System that fits recent observations, both expected and unexpected.

Their model indicates Voyager 1 actually entered interstellar space a little more than a year ago, a finding directly counter to recent papers by NASA and other scientists suggesting the spacecraft was still in a fuzzily-defined transition zone between the Sun's sphere of influence and the rest of the galaxy.

But why the controversy?

At issue is what the boundary-crossing should look like to Earth-bound observers 11 billion miles (18 billion kilometers) away. The Sun's envelope, known as the heliosphere, is relatively well-understood as the region of space dominated by the magnetic field and charged particles emanating from our star. The heliopause transition zone is both of unknown structure and location. According to conventional wisdom, we'll know we've passed through this mysterious boundary when we stop seeing solar particles and start seeing galactic particles, and we also detect a change in the prevailing direction of the local magnetic field.

NASA scientists recently reported that last summer, after eight years of travel through the outermost layer of the heliosphere, Voyager 1 recorded "multiple crossings of a boundary unlike anything previously observed." Successive dips in, and subsequent recovery of, solar particle counts caught researchers' attention. The dips in solar particle counts corresponded with abrupt increases in galactic electrons and protons. Within a month, solar particle counts disappeared, and only galactic particle counts remained. Yet Voyager 1 observed no change in the direction of the magnetic field.

To explain this unexpected observation, many scientists theorize that Voyager 1 has entered a "heliosheath depletion region," but that the probe is still within the confines of the heliosphere. Swisdak and colleagues, who are not part of the Voyager 1 mission science teams, say there is another explanation.

In previous work, Swisdak and Drake have focused on magnetic reconnection, or the breaking and reconfiguring of close and oppositely-directed magnetic field lines. It's the phenomenon suspected to lurk at the heart of solar flares, coronal mass ejections and many of the sun's other dramatic, high-energy events. The UMD researchers argue that magnetic reconnection is also key to understanding NASA's surprising data.

Though often depicted as a bubble encasing the heliosphere and its contents, the heliopause is not a surface neatly separating "outside" and "inside." In fact, Swisdak, Drake and Opher assert that the heliopause is both porous to certain particles and layered with complex magnetic structure. Here, magnetic reconnection produces a complex set of nested magnetic "islands," self-contained loops which spontaneously arise in a magnetic field due to a fundamental instability. Interstellar plasma can penetrate into the heliosphere along reconnected field lines, and galactic cosmic rays and solar particles mix vigorously.

Most interestingly, drops in solar particle counts and surges in galactic particle counts can occur across "slopes" in the magnetic field, which emanate from reconnection sites, while the magnetic field direction itself remains unchanged. This model explains observed phenomena from last summer, and Swisdak and his colleagues suggest that Voyager 1 actually crossed the heliopause on July 27, 2012.

On occasion of India's Independence Day......

Here are some facts...

Fact 1: There were 562 princely states in India at the time of independence. 560 of these states joined India and the remaining two (Junagadh and Hyderabad) were annexed by the military.

Fact 2: After India’s independence from Britain, Portugal amended its constitution and declared Goa as a Portuguese state. Indian troops invaded Goa on December 19, 1961. The former USSR vetoed a resolution submitted by the United States of America and the United Kingdom condemning this invasion.

Fact 3: One of the founders of the Indian National Congress (one of the parties primarily responsible for India’s independence) was Allan Octavian Hume (a British citizen). He is also considered to be the “father of Indian Ornithology”. The other founding members are Dadabhai Naoroji, Dinshaw Wacha, Womesh Chandra Bonnerjee, Surendranath Banerjee, Monomohun Ghose and William Wedderburn.

Fact 4: A drafting committee was set up on 29th August, 1947 to draft the Indian constitution. The final version of the constitution came into effect on January 26, 1950 (Republic Day of India). During the emergency imposed by Indira Gandhi in 1976, our constitution was amended and the word “socialist” added to the preamble to the constitution. Our founding fathers never intended India to be a socialist country.

The new approach to manipulating light, conducted by a group from France's Université de Nice-Sophia Antipolis and China's Xiamen University, uses little power, does not require an external electrical field, and operates at room temperature, making it more practical than many other slow light experiments. Putting the brakes on light can help scientists compare the characteristics of different light pulses more easily, which in turn can help them build highly sensitive instruments to measure extremely slow speeds and small movements, says Umberto Bortolozzo, one of the authors on the Optics Express paper. In a second paper, also published today and appearing in OSA's journal Optics Letters, Bortolozzo and colleagues from the Université de Nice-Sophia Antipolis and the University of Rochester describe an instrument that uses slow light to measure speeds less than one trillionth of a meter per second.

Scientists have known for a long time that a wave packet of light becomes more sluggish when it travels through matter, but the magnitude of this slow-down in typical materials such as glass or water is less than a factor of two. "The question is: can we do something to the matter in order to make light slow down much more considerably?" says Bortolozzo.

The key to achieving a significant drop-off in speed is to take advantage of the fact that when light travels as a pulse it is really a collection of waves, each having a slightly different frequency, says Bortolozzo. However, all the waves in the pulse must travel together. Scientists can design materials to be like obstacles courses that "trip up" some of the waves more than others. In order to exit the material together, the pulse must wait until it can reconstitute itself.

Other research groups have manipulated the properties of atomic vapors or crystal lattices to significantly slow light and, under certain circumstances, to temporarily "stop" it inside the medium. Bortolozzo's team instead used a liquid crystal similar to the materials used in LCD television and computer displays that could operate in a simple setup, does not require external voltages or magnetic fields, and works at room temperature and with very low optical power. They added a chemical component that twisted the liquid crystal molecules into a helical shape and then added dye molecules that nestled in the helical structures. The dye molecules change their shape when irradiated by light, altering the optical properties of the material and hence changing the relative velocities of the different wave components of the light pulse as it travelled through. In addition, the helical structure of the liquid crystal matrix ensures a long lifetime of the shape-shifted dyes, which makes it possible to "store" a light pulse in the medium and later release it on demand.

Although one of the ultimate goals of slow light research is to find a way to slow and store light pulses for optical communications, the long length of the light pulses used by Bortolozzo's team make such an application impractical. However, Bortolozzo says the team's technique is well suited to sensing and interferometry applications. In the Optics Letters,paper Bortolozzo and colleagues demonstrate how slow light can be used to build a highly sensitive instrument that works on a principle similar to the concept behind a police officer's radar gun. Radar guns catch speeders by detecting a shift in the frequency of radio waves (called a Doppler shift) that can be used to determine a car's velocity. Bortolozzo's team used slow light to detect a very slight Doppler shift in a pair of light beams.

The approach "allows us to measure extremely low speeds in only one second of measurement time," explains Bortolozzo. He says a next step will be for the team to test their dye and liquid crystal slow light approach in similar phase sensing applications. The team will also endeavor to extend the work to other molecular arrangements and different types of dye. "Realizing slow and stopped light in these media is very exciting both for the fundamental research that discovers such new effects in soft matter systems, and for the new possibilities that these investigations could open in the fields of remote sensing and optical storage," says Bortolozzo. Papers:

Tsar Bomba is the nickname for the AN602 hydrogen bomb, the most powerful nuclear weapon ever detonated. Its October 30, 1961 test remains the most powerful artificial explosion in human history. It was also referred to as Kuz'kina Mat' ,referring to Nikita Khrushchev's promise to show the United States a "Kuz'kina Mat'" at the 1960 United Nations General Assembly.

The famous Russian idiom, which has been problematic for translators, literally meaning “to show somebody Kuzka's mother”, equates roughly with the English “We’ll show you!” Developed by the Soviet Union, the bomb had the yield of 50 to 58 megatons of TNT (210 to 240 PJ). Only one bomb of this type was ever officially built and it was tested on October 30, 1961, in the Novaya Zemlya archipelago, atSukhoy Nos.

The remaining bomb casings are located at the Russian Atomic Weapon Museum, Sarov (Arzamas-16), and the Museum of Nuclear Weapons, All-Russian Research Institute of Technical Physics, Snezhinsk (Chelyabinsk-70). Neither of these casings has the same antenna configuration as the device that was tested.

Many names are attributed to the Tsar Bomba in the literature: Project 7000; product code 202 ;article designations RDS-220 , RDS-202, RN202 (PH202), AN602 (AH602); codename Vanya; nicknames Big Ivan, Tsar Bomba, Kuz'kina Mat'.

 The term "Tsar Bomba" was coined in an analogy with two other massive Russian objects: the Tsar Kolokol (Tsar Bell) and the Tsar Pushka (Tsar Cannon). The CIA denoted the test as "JOE 111".

Researchers at the University of Rochester have measured for the first time light emitted by photoluminescence from a nano diamond levitating in free space. In a paper published this week in Optics Letters, they describe how they used a laser to trap nano diamonds in space, and -- using another laser -- caused the diamonds to emit light at given frequencies.

The experiment, led by Nick Vamivakas, an assistant professor of optics, demonstrates that it is possible to levitate diamonds as small as 100 nanometers (approximately one-thousandth the diameter of a human hair) in free space, by using a technique known as laser trapping.

"Now that we have shown we can levitate nanodiamonds and measure photoluminescence from defects inside the diamonds, we can start considering systems that could have applications in the field of quantum information and computing," said Vamivakas. He said an example of such a system would be an optomechanical resonator.

Vamivakas explained that optomechanical resonators are structures in which the vibrations of the system, in this case the trapped nanodiamond, can be controlled by light. "We are yet to explore this, but in theory we could encode information in the vibrations of the diamonds and extract it using the light they emit."

Possible avenues of interest in the long-term with these nano-optomechanical resonators include the creation of what are known as Schrödinger Cat states (macroscopic, or large-scale, systems that are in two quantum states at once). These resonators could also be used as extremely sensitive sensors of forces -- for example, to measure tiny displacements in the positions of metal plates or mirrors in configurations used in microchips and understand friction better on the nanoscale.

"Levitating particles such as these could have advantages over other optomechanical oscillators that exist, as they are not attached to any large structures," Vamivakas explained. "This would mean they are easier to keep cool and it is expected that fragile quantum coherence, essential for these systems to work, will last sufficiently long for experiments to be performed."

The future experiments that Vamivakas and his team are planning build on previous work at Rochester by Lukas Novotny, a co-author of the paper and now at ETH in Zurich, Switzerland. Novotny and his group showed previously that by tweaking the trapping laser's properties, a particle can be pushed towards its quantum ground state. By linking the laser cooling of the crystal resonator with the spin of the internal defect it should be possible to monitor the changes in spin configuration of the internal defect -- these changes are called Bohr spin quantum jumps -- via the mechanical resonator's vibrations. Vamivakas explained that experiments like this would expand what we know about the classical-quantum boundary and address fundamental physics questions.

The light emitted by the nanodiamonds is due to photoluminescence. The defects inside the nanodiamonds absorb photons from the second laser -- not the one that is trapping the diamonds -- which excites the system and changes the spin. The system then relaxes and other photons are emitted. This process is also known as optical pumping.

The defects come about because of nitrogen vacancies, which occur when one or more of the carbon atoms in diamond is replaced by a nitrogen atom. The chemical structure is such that at the nitrogen site it is possible to excite electrons, using a laser, between different available energy levels. Previous experiments have shown that these nitrogen vacancy centers in diamonds are good, stable sources of single photons, which is why the researchers were keen to levitate these particles.

Using lasers to trap ions, atoms and more recently larger particles is a well-established field of physics. Nanodiamonds, however, had never been levitated. To position these 100 nanometers diamonds in the correct spot an aerosol containing dissolved nanodiamonds sprays into a chamber about 10 inches in diameter, where the laser's focus point is located. The diamonds are attracted to this focus point and when they drift into this spot they are trapped by the laser. Graduate student Levi Neukirch explains that sometimes "it takes a couple of squirts and in a few minutes we have a trapped nanodiamond; other times I can be here for half an hour before any diamond gets caught. Once a diamond wanders into the trap we can hold it for hours."

The Rochester researchers collaborated on this paper with Lukas Novotny, formerly at the University of Rochester and now at ETH Zurich, Switzerland, and with Jan Gieseler and Romain Quidant, at ICFO in Barcelona, Spain.

The researchers acknowledge the support from the University of Rochester, the European Community's Seventh Framework Program, Fundació privada CELLEX and from the U.S. Department of Energy.

India on Saturday took a major leap towards completing its nuclear triad – the ability to launch strategic weapons from land, air and sea with the miniature reactor on board the country’s first indigenous nuclear-powered submarine “attaining criticality”. It means the reactor is in stable configuration producing constant power.

The 6,000 tonne Arihant, which means destroyer of enemies, will head for sea trials later this year. The submarine will kick off deterrent patrols, armed with nuclear warheads, in early 2014.The submarine will complete the sea-leg of India’s nuclear triad, giving it enduring nuclear strike and counter-strike capabilities.
It will be equipped with the K-15 missile, a closely guarded DRDO secret, capable of delivering a nuclear warhead up to 750 km away.

India already has the capability to carry out nuclear strikes with fighter planes and land-launched missiles. The Agni series of ballistic missiles and fighters planes such as Sukhoi-30MKIs and French-origin Mirage-2000s can deliver nuclear warheads. The Rafale fighters being acquired from France are also nuclear capable.India has 90-110 nuclear warheads, compared to 250 in the Chinese arsenal.

The United States, Russia, the UK, France and China are the only countries that can deliver nuclear warheads from a submarine.Experts say India’s submarine fleet should have at least 5 nuclear-powered ballistic missile submarines.Two more nuclear-powered submarines are in the works to reinforce India’s strategic deterrent force at sea.The INS Chakra, leased from Russia in January 2012, cannot deliver nuclear warheads in its current configuration. It only carries torpedoes, land-attack cruise missiles and anti-ship missiles.