Huge Explosion Reveals the Most Massive Star Known

All supernova explosions are violent affairs, but this one takes the cake. Astronomers have spotted a new type of extremely bright cosmic explosion they think originates from an exceptionally massive star.

This breed of explosion has been long predicted, but never before seen. Like all supernovas, the blast is thought to have marked the end of a star's life. But in this case, that star may have started out with 200 times the mass of the sun.

The supernova in question, SN2007bi, was observed in 2007 in a nearby dwarf galaxy. Scientists knew at once it was something different because it was about 50 to 100 times brighter than a typical supernova.

"It was much brighter, and it was bright for a very long time," said researcher Paolo Mazzali of the Max-Planck Institute for Astrophysics in Germany. "We could observe this thing almost two years after it was discovered, where you normally don't see anything anymore."

After analyzing its signature, astronomers published a paper in the Dec. 3 issue of the journal Nature confirming that it matches theoretical predictions of a so-called pair-instability supernova.

"There were some doubts that they existed," said astronomer Norbert Langer of the University of Bonn in Germany, who did not work on the project. Langer wrote an opinion essay on the finding in the same issue of Nature. "There were severe doubts that stars that massive could ever form in the universe. Now we seem to be very sure that there was a star with 200 solar masses."

In a pair-instability supernova, the star has neared the end of its life and exhausted its main supplies of hydrogen and helium, leaving it a core of mostly oxygen. In smaller stars, the core continues to burn until eventually it is all iron, then collapses in a Type II supernova, leaving behind a remnant black hole or neutron star.

But in the case of an extremely massive star, while its core is still made of oxygen, it releases photons that are so energetic, they create pairs of electrons and their anti-matter opposites, positrons. When the matter and antimatter meet, they annihilate each other. This reaction reduces the star's pressure, and it collapses, igniting the oxygen core in a runaway nuclear explosion that eats up the whole star, leaving no remnant at all.

The discovery of this rare type of supernova suggests that a few stars actually can grow into such large behemoths — which has long been a topic of debate.

"I was never a believer in very massive stars," Mazzali told SPACE.com. "Seeing something like this explode means these things exist. This is a fairly new development in the formation of stars."

INTERESTING POST FROM THE WORLD OF BIOCHEM

The RNA World

by Sidney Altman
1989 Nobel Laureate in Chemistry

The phrase "The RNA World" was coined by Walter Gilbert in 1986 in a commentary on the then recent observations of the catalytic properties of various RNAs. The RNA World referred to an hypothetical stage in the origin of life on Earth. During this stage, proteins were not yet engaged in biochemical reactions and RNA carried out both the information storage task of genetic information and the full range of catalytic roles necessary in a very primitive self-replicating system. Gilbert pointed out that neither DNA nor protein were required in such a primitive system if RNA could perform as a catalyst. At that time, it had only been demonstrated that RNA could cleave or ligate phosphodiester bonds. Nevertheless, as is a frequent occurrence in science, a general hypothesis was constructed from a few specific instances of a phenomenon. This hypothesis proved to be very effective in stimulating thought about the origin of life on Earth. Ensuing discoveries of other natural catalytic RNAs that could cleave and ligate phosphodiester bonds, and the very recent observation that the region surrounding the peptidyl transferase center of a bacterial 50S ribosomal subunit contains RNA and no protein, further buttress the hypothesis. Finally, the so-called "evolution in vitro" methodology, which is able to scan an enormous number of nucleic acid sequences in vitro for any given function, has revealed that RNA, indeed, can have many different catalytic functions as so can, presumably, DNA.

On further reflection, many doubts have been raised about whether or not the original genetic/catalytic material could have been RNA as we know it today because extreme conditions on the primitive Earth might have led to the rapid chemical degradation of RNA. Nevertheless, even if the precise chemical nature of the early genetic/catalytic material differed from present-day RNA, it seems reasonable to conclude that the RNA World did exist at some time. If very primitive life on Earth did not arise until about 3.5

billion years ago, there was, perhaps, a period of 0.5 billion years in which to sample many polymer sequences that originally arose through non-biochemical mechanisms and that ultimately evolved directed the first self-replicating systems.

My involvement in the discovery of the first catalytic RNA began in innocence during a study of tRNA biosynthesis in Escherichia coli. I was fortunate enough to isolate and characterize a precursor tRNA, one of the intermediates in the metabolic pathway leading to the synthesis of mature tRNA. As in all biochemical pathways, if one has an intermediate compound, there must be an intra-cellular enzyme that acts on this intermediate to take it to the next step in the pathway. This enzyme, ribonuclease P (RNase P), was readily identifiable. Its function was to cleave a phosphodiester bond at the start of the mature tRNA nucleotide sequence, thereby releasing the upstream extra or "precursor" nucleotides.

The total purification of RNase P proved to be a very difficult task. However, a perceptive and hard-working graduate student, Ben Stark, noticed that an RNA copurified with the protein in the enzyme preparation. He then devised a test to see if the RNA molecule was essential for the function of the enzyme. This test used the same strategy that Avery, MacLeod and McCarty had used to prove that DNA was the essential ingredient in bacterial transformation. In Stark's experiment, the test showed that the RNA was essential for RNase P function. This result explained why the purification, which had been designed to isolate a proteinaceous complex, was so difficult. It also led to much disbelief in the community of enzymologists.

We soon suggested that the RNA subunit of RNase P was part of the active center of the enzyme, by analogy to the then current picture of the ribosome. A few years later, however, Cecilia Guerrier-Takada, a postdoctoral fellow, demonstrated that this RNA, itself, was a true enzyme in vitro. At that time, Tom Cech had recently and independently observed phosphoester bond cleavage and ligation by a different RNA molecule. Cech's observation and ours, while still greeted skeptically by some members of the enzymological community, were soon universally accepted and within a few years other catalytic RNAs derived from plant pathogens and the human delta RNA were also found.

The chemical details of catalysis by RNase P remain to be fully worked out although a rough picture of this reaction is now available. A fascinating aspect of the RNase P "problem" is the vast difference in chemical make-up of subunits and catalytic mechanism of this enzyme as it is found in eukaryotes (e.g., the RNA subunit is not active in vitro) compared to these properties in prokaryotes. Evolution has presented us with contemporary versions of this enzyme that undoubtedly will someday tell us an interesting story of its progression from an RNA to various complexes of RNA and protein.

Launching Bhuvan: ISRO’s answer to Google Earth, zoom into states, districts

Google Earth’s got some competition now — from the Indian Space Research Organisation (ISRO), which today unveiled its beta version of Bhuvan (meaning earth in Sanskrit).

A web-based tool like Google Earth, Bhuvan promises to give better 3-D satellite imagery of India than is currently being offered by the US-based software giant plus a host of India-specific features like weather information and even administrative boundaries of all states and districts.

The application can be downloaded from http://bhuvan.nrsc.gov.in/

The tool would offer pictures of the globe, just like Google Earth, and navigable in the same way but currently has the best resolutions over the Indian sub-continent. It allows users to fly from space to street level, grab, spin and zoom down to any place.

It also provides tools for measuring, drawing, saving, printing and visualizing thematic information. The resolutions currently on offer are good enough to view a vehicle moving on a road quite clearly.

Bhuvan currently only offers images taken between one and three years ago even over India. It combines satellite imagery from various sensors onboard IRS (Indian Remote Sensing) satellites and transposes them on a 3-D globe. As it keeps updating its database with more recent and higher resolution images, Bhuvan eventually promises to offer real-time data and images.

Incidentally, Indian authorities have had some problems in the past with Google Earth’s depiction of certain parts of the country. Recently, Google Earth admitted that it had mistakenly shown some areas in Arunachal Pradesh as part of Chinese territory and promised to correct the maps soon. The Indian government had earlier pulled up Google Earth for showing some sensitive and strategic defence locations on its maps.

GOOGLE MAPS - Satellite Images of HEM SHEELA MODEL SCHOOL

ISNT THIS EXCITING???

Photos of our beloved MOHANTY SIR

SIR WE MISS U A LOTTTTT!             - CLASS 12/B(HSMS)

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hsms photos

                                                           

Hem Sheel Model school founders day photos

Hem Sheela Model School - 13th Founders Day Prog

Some photos..........