DARK MATTER AND ENERGY RESEARCH UPDATE
Excess positrons could come from dark matter after all
16 Nov 2017
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Photograph of HAWC
Mountain HAWC: the High Altitude Water Cherenkov Gamma-Ray Observatory
The mysterious excess of high-energy positrons detected by the PAMELA satellite does not come from the two nearby pulsars, according to an international team of physicists using the High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) in Mexico. The finding opens the door to alternative explanations of the origins of the particles – including the possibility that they are created by the annihilation or decay of dark-matter particles.
The mystery started back in 2008, when scientists at PAMELA – the first satellite detector orbiting in space searching for antimatter – reported detecting an unexpectedly high number of high-energy positrons.
Since then, two plausible explanations for these observations have been debated by physicists. One possibility is that the positrons come from nearby pulsar wind nebulae, which are fast-spinning neutron stars that act as cosmic ray accelerators and produce streams of electrons and positrons. The other possibility is that the positrons are produced by hitherto unobserved processes involving nearby dark matter.
The two best pulsars candidates are Geminga and PSR B0656+14, because of their age and proximity. However, by looking at gamma rays from the regions around these two pulsars, the HAWC team concluded that both pulsars are surrounded by extended and murky clouds, which positrons cannot pass through to reach Earth. While this appears to rule out the pulsars, it does not prove that the positrons have dark-matter origins.
“[The new result] constrains the pulsar explanation, which was the best… until now,” says Piergiorgio Picozza of the University of Rome Tor Vergata, who was part of the PAMELA team.
“The simplest explanation has disappeared and dark matter remains on the table, maybe gaining some extra points,” adds Picozza. “The community will now have to enter into a big discussion, which for us, is a good thing.”
Andrés Sandoval of the National Autonomous University of Mexico is HAWC’s Mexico spokesperson, and was involved in the research. He did not expect to rule out the pulsars when HAWC started its measurements. “I was very surprised at first, since we really thought they were [the sources],” he tells Physics World.
However, Sandoval says he would not put his money on the dark matter explanation just yet – even though, admittedly, it would be more exciting. “As a conservative physicist, I’d say the sources have to be pulsars, because that’s what we know more about. There are still so many questions left up in the air,” he says.
Besides the annihilation or decay of dark matter particles, the HAWC team believes the positrons could come from other pulsars, although there are no better candidates than the two just ruled out. Other types of cosmic accelerators, such as micro-quasars and supernova remnants, could be sources, or the positrons could be the result of secondary particle production. [link to physicsworld.com (secure)
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is the ninth form of the Goddess Durga, the meaning of her name is as follows: Siddhi means supernatural power or meditative ability, and Dhatri means giver or awarder. She is worshipped on the ninth day of Navaratri (nine nights of Navadurga); she fulfills all the divine aspirations and completes the mundane.
It is believed that one side of Lord Shiva’s body is that of Goddess Siddhidatri. Therefore, he is also known by the name of Ardhanarishwar. According to Vedic scriptures, Lord Shivaattained all the siddhis by worshiping this Goddess.
Around the time when the universe was just a massive void completely full of darkness, there were no indications of the world anywhere. But then a ray of divine light, which is ever existing, spread everywhere, illuminating each and every nook of the void. This sea of light was formless. Suddenly, it started taking a definite size, and finally looked like a Divine Lady, who was none other than Goddess Mahashakti herself. The Supreme Goddess came forth and gave birth to the Trinity of Gods, Brahma, Vishnu and Mahadev. She advised the three Lords to contemplate to understand their roles of performing their duties for the world. Acting on the words of Goddess Mahashakti, Tridev sat by the bank of an ocean and performed penances for many years. The pleased Goddess appeared before them in the form of Siddhidhatri. She bestowed upon them, their wives in the forms of Saraswati, Lakshmi and Parvati. Goddess Siddhidhatri entrusted Brahma to take up the role as the creator of worlds, Vishnu with the role of preserving the creation and its creatures, and Mahadev with the role of destroying the worlds when it is time. She tells them that their powers are in the forms of their respective wives, who will help them perform their tasks.
The Goddess assured them that she will also provide to them, divine miraculous powers, which will also help them carry out their duties. Saying this, she bestowed to them eight supernatural powers, in which they were named Anima, Mahima, Garima, Laghima, Prapti, Prakambya, Ishitva and Vashitva. Anima means reducing one's body to the size of a crumb, Mahima means expanding one's body to an infinitely large size, Garima means becoming infinitely heavy, Laghima means becoming weightless, Prapti means having omnipresence, Prakambya means achieving whatever one desires, Ishitva means possessing absolute lordship, and Vashitva means having the power to subjugate all.
Apart from the eight supreme siddhis that goddess Siddhidatri had granted Tridev, she is believed to have granted to them, nine treasures and ten other kinds of supernatural powers or potentialities. On the behest of Lord Brahma, Goddess Siddhidhatri converted half of Shiva and Parvati's bodies to become Ardhanarishwar, for the development of creation. The two parts, man and woman, created Gods, demons, monsters, heavenly beings, ogres, trees, damsels, snakes, cows, buffalos, predators, prey, aquatic animals, Aruna and Garuda and many more species of the world were born and thus originated from them. The creation of the entire world was now fully complete, full of innumerable stars, galaxies as well as constellations. The solar system was complete with the nine planets. On Earth, firm landmass was created, surrounded by such vast oceans, lakes, streams, rivers and other bodies of water. All types of flora and fauna had originated and were given their proper habitations. The 14 worlds were created and constructed altogether, giving the above-mentioned creatures places of residences to stay in, as to which they all called home.
In this form Durga is seated on a lotus and is four-armed. She holds a lotus, mace, Sudarshana Chakra and shankha. In this form Durga removes ignorance and she provides the knowledge to realize that or Brahman. She is surrounded by Siddhas, Gandharvas, Yakshas, Devas (Gods) and Asura (Demons) worship her. The Siddhi that she provides is the realization that only she exists.