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Just in time for July 4, astronomers say they have found a new type of stellar firecracker.
Stars that die an explosive death generally fall into two categories: young, massive stars that collapse under their own weight and hurl their outer layers into space, and older, sunlike stars that undergo a thermonuclear explosion. But the stellar explosion recorded in January 2005 and known as SN 2005E doesn’t fit either class, according to a new analysis reported online June 11 at arXiv.org.
The explosion ejected only a small amount of material — the equivalent of 0.3 solar masses — and erupted in the halo of an isolated galaxy, a region devoid of any star formation. These findings suggest that the explosion, or supernova, did not arise from the collapse of a massive star, report study coauthors Hagai-Binyamin Perets and Avishay Gal-Yam of the Weizmann Institute of Science in Rehovot, Israel, and their colleagues. A massive star would have cast off much more material and would have erupted in a star-forming region. Since stellar heavyweights are so short-lived, they can’t move far from their birth site.
On the other hand, the researchers note, the explosion’s dimness and the abundance of elements forged in the eruption indicate it was not a typical thermonuclear explosion. Spectra show that the debris from the outburst contains five to 10 times more calcium than observed in any other known stellar explosion and probably contains a high abundance of radioactive titanium-44.
“In my experience, there’s lots of strange supernovas out there … but it really does look like this one might be something different,” comments theorist Andrew MacFadyen of New York University.
The authors of the paper declined to be interviewed because they had submitted the report to Nature. In their article, they report that the erupting oddball matches a model in which a compact star called a white dwarf nabs a thick layer of helium from a companion star. The star would then undergo a thermonuclear explosion that would destroy the helium but leave the rest of the white dwarf intact. By contrast, in a common type of supernova known as a type 1a supernova, a white dwarf made up mostly of carbon and oxygen blows itself to smithereens after stealing matter from a companion.
Perets, Gal-Yam and their collaborators report that SN 2005E resembles a few other peculiar supernova, notably an explosion found last year and known as SN 2008ha.
“Both of these objects have very low luminosity, low velocity [of debris] and strong calcium lines,” says Rober Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Kirshner, along with some of the collaborators on the SN 2005e study, is a coauthor of a study on SN 2008ha set to appear in an upcoming issue of The Astronomical Journal.
The conclusions of both papers suggest a weak thermonuclear explosion, although the study of SN 2005E is more far-reaching, Kirshner says. “My guess is that the same interpretation would probably work for both,” he says.
Because both SN 2005E and SN 2008ha are so faint, telescopes may have failed to detect other similar explosions, comments MacFadyen. Supernovas are known to seed galaxies with an assortment of heavy elements. If the number of explosions in the new class is large enough, they may be an important contributor to this process. It’s a well-known story how supernovas produce these elements, “but there’s always room for adding new players to the team,” says MacFadyen.
Found in: Astronomy and Atom & Cosmos
- A new type of stellar explosion. Perets, HB et al. Available online at [Go to]
- SN 2008ha: An extremely low luminosity and extremely low energy supernova. Ryan J. Foley et al. In press, The Astronomical Journal
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Authors_;
*Mr. Rupak Bhattacharya-Bsc(cal) Msc(JU) 7/51 purbapalli,po-sodepur dist 24 parganas(north) Kol-110,West Bengal, India
**Professor Pranab kumar Bhattacharya MD(cal) FIC Path(ind) Professor of pathology, institute of post graduate medical education & research,244 a AJC Bose Road, Kolkata-20, west Bengal, India
***Mr.Ritwik Bhattacharya B.com(cal) 7/51 purbapalli, Po-sodepur Dist 24 parganas(north) , Kolkata-110,WestBengal, India
****Miss Upasana Bhattacharya- Student, Mahamyatala, Garia, kol-86
**** Mrs. Dalia Mukherjee BA(hons) Cal Swamiji Road, south Habra, 24 Parganas(north) West Bengal, India
Dr Avisnata Das MBBS(cal) Ex House physician, Medical college, Kolkata, West Bengal, India
****Dr. Srabani Chakraborty MD(cal); Asst. Professor Pathology, IPGME&R, Kolkata-20
Stars last too long in the universe. For an astronomers to see any evolution of a star or death of a star, in the course of his/their life time, unless he/they is/are lucky enough to see one star destroying itself in a supernova or in a nova explosion or turning towards a Red giant . My old and recently diseased father , late Mr. Bholanath Bhattacharjee of 7/51 purbapali, po-sodepur,24 parganas(north) kol-110, West Bengal, India ,used to teach our brothers and sister in our young ages, with his built up notion like this”….. Stars are long lived objects with ages, they are as old as our galaxy is, as old as our universe is and they are symbol of eternity they may be 2.5 billion years – 3 billion years old from a first generation stars explosions and are almost perfect cosmic mile markers even very close to Big Bang. Today we know that looking at a supernova of a very distant star almost at horizon of the universe, or of a Nebula, we can understand the mystery of creation of the Universe, the Big Bang it self. They are really the symbol of the eternity. Edington suspected, that the nuclear reactions in the interior of the stars are primary sources of energy for it’s luminosity and fusion of hydrogen to make Helium and that can take place in it, in time bound scale for this ranges, from millions to millions years. Our sun has lost it’s brightness by more then 1% from it’s birth, due to change in it’s internal structure for past 107 years. But the question remains how these supernovas explode? What is the mechanism behind it? No physics probably answered it. Here may be some explanations by my brothers Rupak Bhattacharya and Ritwik Bhattacharya the authors
If we consider the mode of generation of energy in the star, nuclear process provide the only source of energy adequate to keep the stars ongoing luminous. The nuclear fusion in which Hydrogen is built up into Helium, can function sufficient fast at temperature, like those at central core of star (12-25 million degrees). The Helium burning process are important 1) Carbon Nitrogen cycle at which a carbon-12 nucleus (12C) capture proton and is converted into 13C, Nitrogen-4 and nitrogen –15. At a final temperature, a proton leads to a fusion yielding original 12C nucleus to a Helium nucleus .2) The Proton- Proton process, in which protons are built direct Helium nuclei through steps, involving first in production of a deuterium and helium3 nuclei to form Helium4 nucleus and two protons. 3) Carbon burning process where 12C nucleus undergoes fusion reaction in the interior of a star producing neutron, proton, and Alfa particles with huge temperature. The first reaction probably dominates into the star, applicable to more massive stars then Sun. The second and third reaction is applicable for Sun and in less massive stars then Sun respectively. Thermonuclear reactions like those in a hydrogen bomb are powering the Sun in a contained and continuous explosions converting some four hundred millions tons (4x1014 grams) of hydrogen into helium. When we look up in the sky in night and see the stars we see them shining because of distant nuclear fusion in them .But hydrogen fusion can not continue for ever. Our Sun is ~ 4.7109 years old star. The energy produced in our ordinary star Sun in each second, is equivalent to the destruction of 41/2 millions tons of hydrogen mass in every second, a mere fleabite compared with the mass of the Sun which is two thousand billion and billion tones. In the Sun or in any other stars, there is limited so much hydrogen in it’s hot interior. Although Helium is predominating as net fusing of Hydrogen, other elements like “carbon”, “Iron”, “L element” “Manganese” “Chromium”, EU, yttrium, Magnesium, SR, Nickel, Osmium are also built up in the interior of the stars. Arnett and Truran [Arnett W.D and Truran. JW –Astrophysics.J-Vol157;P339,1969] showed that nuclear reaction net work in the sun when 12C nuclei began to under go the fusion reaction in the interior of sun many elements are produced such as
12C+12C---- 23Na+P+2.238mev----23Mg+ n+2.623mev------20Ne+ 27Al +4.616mev and the reaction goes on endlessly. A large number of computed reactions are possible as the liberated neutron and gamma particles begin reaction with all the nuclear species generated within the hydrogen fusion. In fact Arnett and Truran produced 99 different reactions only in 12C carbon burning net work and 23Na,20Ne, 24Mg,27Al,29Si, and some31P elements are also produced. Beside these Li, Be, B ( Known as leptons)are also produced in the stars due to hydrogen burning. Another more most elementary particles are produced in huge quantities. They are Neutrinos or ghost particles due to hydrogen burning procedure ( Professor Pranab Bhattacharya & Mr. Rupak Bhattacharyya). Conversion of hydrogen into helium in the center of the stars or of the Sun, not only accounts for Sun’s brightness in photons of visible light. It also produces a radiance of a more ghostly kind. The sun glows faintly in neutrinos , which like photons, weight nothing and travel at speed of light. Neutrinos emitted from Sun carry an intrinsic angular momentum or spin while photons has no spin. Matter is transparent to neutrinos which can pass effortlessly through the earth and through the Sun. Only a tiny fraction of them is stopped by intervening matter. As you look up our sun, a billions neutrinos pass through your eye ball. They are not stopped by Retina as ordinary photons do ,but continue unmolested through the back of your head. The curious part is that if at night if I look down at ground, towards the place where sun would be, almost exactly same numbers of solar neutrinos pass through my eye ball, pouring through an interposed earth which is as transparent to neutrinos as a plane of clear glass is to visible light. Neutrinos on very rare occasion convert chlorine atoms into argon atoms with the same number of protons and neutrons. Davis first used a beautiful technique of Pontecours and Alvarez based on the reaction 37C1(V,e-)37Ar to place an upper limit on the solar neutrinos flux on earth
The previous view regarding the “L atoms elements” was that each star makes it’s own share of these “L atoms elements”i.e (autogenously origin). But the concept of autogenic view has been now abandoned, because highest abundance values for stellar Li & Be have shown to be not larger than interstellar upper limit. The formation of each “L atoms” requires the acceleration of about 1erg fast proton. To account auto genetically for lithium abundance in T. Tauri stars (L1/H=109), the time integrated amount production of energy into particle acceleration must be comparable with gravitational release, implying an unlikely high efficiency for acceleration mechanism. So nuclear mechanism is responsible for generation of “L atoms” in the star. It involves high-energy process (Thermonuclear reactions). These L atoms” can be formed in two different ways within the stellar interiors. By the collision of incident light particles on the heavier atoms of interstellar gas (For instance fast protons on stationary C, N, O) or the reverse (for instance fast C, N, O on hydrogen at rest). In the first case the Products “ L atoms are to remain in rest, while in the second case, the products are moving at a velocity comparable with that of cosmic rays. The fate of “ L atoms” generated by fast protons on stationary C, N, O stationary atoms and are all rapidly thermalised and become part of ISM.
“L atoms” generated by reverse process have a fate which depends on the initial energy of “L atoms”. L atoms with energy E 0.3Gev neucleon-1 will suffer nuclear transformation of various elements in the stellar interior.
Analysis of Old stars can give us some idea that heavy elements are produced in the interior of the stars and are subsequently ejected into the ISM either through the supernova explosion or through stellar winds or through cosmic rays. The total mass loss, from all stars in a galaxy will be roughly 1MO per year. A fraction of these accumulate in the galactic nuclei, which are center of the gravitational attraction. The halo of our galaxy is nearly spherical region containing very old stars, which have a smaller content of heavy elements than our sun has. It is usually assumed that some how cloud of gas condensed to form our galaxy and that the halo stars were formed during the collapse process and left with a nearly spherical distribution. These stars are ultra high velocity stars. These stars show weak spectral lines corresponding to abundance of carbon and heavier elements [relative to hydrogen] that are lower than our Sun. Because these stars are oldest in our galaxy quite distinct type of nuclear process have been postulated for different groups of elements. The most abundant nuclei are 32S and 58Fe those can be formed by silicon burning process while 16O, 20Ne,23Na 24Mg,28S may be produced by explosive carbon burning process. When heavier elements notably Sr, Y, Zr, Ba etc require neutron capture on slow time scale, by iron group nucleotide already present in the star. A peculiar type of star 73 DRA has been investigated for many a time. It is full of chromium with europium and strontium. The star showed the presence of Cr, Eu, Sr and also Mn, Fe, Ni, in gaseous form while osmium (z=76) is present in both neutral and ionized form. The importance of these heavy elements is that, some of them such as Iridium, gold, uranium are also produced in the stars in the gamma process of nucleus synthesis [Neutron capture slow process]
So Helium, L atoms, Carbon, Iron, gold, chromium, nickel, silicon and many other elements are built up in the stellar interior. Although the net fusing of hydrogen into helium dominates however at this stage. Helium builds up in the core. The supply of hydrogen fuel diminishes and eventually becomes in sufficient to provide energy to hold up the strain position. As the energy production decreases, the core of the star contracts and heats up through release of gravitational energy. With a hotter center there is a greater outward pressure and the outer layer of the star expands, so that the star now becomes a RED GIANT. The red giant has a radius hundred times that of a sun. Mean while in the hotter core a new series of fusion reactions begins and with the helium as the fuel many elements like carbon oxygen, neon, magnesium. When helium will exhaust as a fuel, the carbon burning process will start as 12C as a fuel in the star. In any star the internal temperature and density and therefore the rate at which the energy is generated depend sensitively on the opacity of the stellar material or in other words, on the ease with which the photons can escape from the stellar core. In simple terms you can say greater the opacity harder it is for heat to get out making core hotter. Opacities in normal star can be calculated reliably from knowledge for the abundance of the constituent elements and their ionization site
Suernova-: Another important thing in our universe are the supernovas or novas. The supernovas are the explosion of the central core or outer core of a giant massive star. These supernovas are found in the biniary star system. A star may end its life cycle either in the form of a RED GIANT or in the form of a white dwarf or in the form of a “ black Dwarf” or in the form of “ neutron Star” or in Black Hole” or in the form of Supernova Explotion”. When the explosion of a star occurs in small scale, we call it Nova. In Big bang concept, apart from hydrogen, a little helium was produced. Every atom of every element had been built up by the nuclear fusion reaction in the stellar pressure cooker. The elements only could arrive in the interstellar space to mingle in the clouds of forminig protostars is through this supernovas Novas are however quite different from supernovas. Novas occur in biniary star system and are powered by silicon or carbon fusion. Supernovas occur in single associated with old population II stellar system such as elliptic galaxies and in globular clusters. The classical supernovas are therefore a subset of the cataclysmic variable class of objects, which undergoes out bursts with peak luminiocity ~ 5x1037 to 5x 1038 ergs S-1 in every 104 to 105 years. Around 10-5 to 10-4 MO material are ejected at velocity typically 1000 Kms-1 at each outburst of supernova. The central system is a semi detached binary stars, containing a white dwarf . Classical supernova out burst was observed in 1901, where as dwarf nova out burst was first observed in 1986.
Supernovas are two types Type-1(SN-I) and Type 2(SN_II) supernovas. Most astronomers agree that a type 1a supernova starts with a white dwarf — an aging star that crams as much mass as the sun into a volume no bigger than Earth. Most white dwarfs are cold and inert. But if the star has a companion, it will siphon mass off the neighbor star until tipping the scales at about 1.4 solar masses. At that mass, the white dwarf becomes dense and hot enough to initiate an explosion.mass accreting white dwarfs,
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in close binary system of stars are Type-1 supernovas, while low mass (M70t
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