The human eye is crucial to astronomy. Without the ability to see, the luminous universe of stars, planets and galaxies would be closed to us, unknown forever. Nevertheless, astronomers cannot shake their fascination with the invisible.
Outside the realm of human vision is an entire electromagnetic spectrum of wonders. Each type of light--from radio waves to gamma-rays--reveals something unique about the universe. Some wavelengths are best for studying black holes; others reveal newborn stars and planets; while others illuminate the earliest years of cosmic history.
NASA has many telescopes "working the wavelengths" up and down the electromagnetic spectrum. One of them, the Fermi Gamma-Ray Telescope orbiting Earth, has just crossed a new electromagnetic frontier.
"Fermi is picking up crazy-energetic photons," says Dave Thompson, an astrophysicist at NASA's Goddard Space Flight Center. "And it's detecting so many of them we've been able to produce the first all-sky map of the very high energy universe."
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This is what the sky looks like near the very edge of the electromagnetic spectrum, between 10 billion and 100 billion electron volts."
The light we see with human eyes consists of photons with energies in the range 2 to 3 electron volts. The gamma-rays Fermi detects are billions of times more energetic, from 20 million to more than 300 billion electron volts. These gamma-ray photons are so energetic, they cannot be guided by the mirrors and lenses found in ordinary telescopes. Instead Fermi uses a sensor that is more like a Geiger counter than a telescope. If we could wear Fermi's gamma ray "glasses," we'd witness powerful bullets of energy - individual gamma rays - from cosmic phenomena such as supermassive black holes and hypernova explosions. The sky would be a frenzy of activity.
Before Fermi was launched in June 2008, there were only four known celestial sources of photons in this energy range. "In 3 years Fermi has found almost 500 more," says Thompson.
What lies within this new realm?
"Mystery, for one thing," says Thompson. "About a third of the new sources can't be clearly linked to any of the known types of objects that produce gamma rays. We have no idea what they are."
The rest have one thing in common: prodigious energy.
© Science@NASAAn artist's concept of giant 'Fermi bubbles' emerging from the heart of the Milky Way.
"Among them are super massive black holes called blazars; the seething remnants of supernova explosions; and rapidly rotating neutron stars called pulsars."
And some of the gamma rays seem to come from the 'Fermi bubbles' - giant structures emanating from the Milky Way's center and spanning some 20,000 light years above and below the galactic plane.
Exactly how these bubbles formed is another mystery.
Now that the first sky map is complete, Fermi is working on another, more sensitive and detailed survey.
"In the next few years, Fermi should reveal something new about all of these phenomena, what makes them tick, and why they generate such 'unearthly' levels of energy," says David Paneque, a leader in this work from the Max Planck Institute in Germany.
For now, though, there are more unknowns than knowns about "Fermi's world."
Says Thompson: "It's pretty exciting!"
.. about 5,000 years ago ...
According to vedic scriptures, Maha Vishnu is the four-handed transcendental form of the Supreme Lord with dark blue skin and a crown on his head who holds symbolical attributes in his hands: a shell, a disc sudarshanu, a rod and a lotus. There is a sacred precious stone kaustubha on his neck. As per vedic cosmology, Vishnu lies on the waters of the Causal Ocean. At the same time he stays in a meditation sleep yoga-nidra. The moment he exhales innumerous numbers of universes come out of the pores of his body as bubbles. They float on the surface of the Causal Ocean like bubbles in foam. All these universes only exist during a single Visnu's exhalation which equals 312 trillion years.
There are further cycles of creation and partial destruction that goes on as per time periods called yugas.
Satya Yuga - 1728 thousand human years
Treta Yuga - 1296 thousand years
Dvapara Yuga - 864 thousand years
Kali Yuga - 432 thousand years
In every Yuga there further decline of religiousness, morals, power, bodily construction and growth and duration of human life and his happiness in comparison with the previous Yugas. We live in the era of Kali Yuga that began 5000 years ago, the most degraded of the 4 yugas prominent with it's quality of quarrel and hipocrisy.
While the whole multitude of universes stays revealed, lord Vishnu watches how the things go in each of them and from time to time he incarnates in various forms entirely or partially to introduce the proper religion, morals and conduct. According to the most spread classification there has been 10 Vishnu's avatars (incarnations) on the Earth.
1. Fish (matsya). When the Earth was under the waters of the Flood, Vishnu assumed the aspect of a fish which was the first to warn Manu (the forefather of the mankind, Brahma's son) of the coming danger. Then it took Manu, his family and seven sages (rishis) out of the Flood on a ship tied to a horn on its head (This story appears as Noah's ark in the bible).
2. Turtle(kurma). Many divine treasures were lost during the flood including ambrosia (amrita) that helped gods to preserve their eternal youth. Vishnu assumed the aspect of a gigantic turtle and went to the bottom of the cosmic ocean. The gods placed mountain Mandara on its back and wrapped the divine serpent Vasuka around the mountain. Then they pulled the serpent and thus untwisted the mountain shaking the ocean up the way an ordinary Indian milkman churns butter. Amrita and many other treasures including goddess Lakshmi came to the surface of the foamed ocean.
3. Wild boar(varaha). Demon Hiranyaksha again immersed the Earth into the depths of the cosmic ocean. Vishnu assumed the image of a gigantic wild boar, killed the demon and put the Earth back in its place by raising it on its fang.
4. Lion Man(narasimha). Another demon Hiranyakashipu received the magic ability to become invulnerable as a gift from Brahma. Neither animal nor man, nor god could kill him neither by day nor by night. Using his safety he started to pursue gods and men and even his pious son Prahlada. Then Prahlada turned to Vishnu for help. At sunset i.e. neither by day nor by night the god suddenly appeared out of a column in the demon's palace and killed the demon in the image of half-man and half-lion.
5. Dwarf (vamana). Demon Bali seized power over the world and after performing a number of ascetic feats he acquired the supernatural might and even started to threaten gods. Vishnu appeared before him in the image of a dwarf and asked to give him as a present as much land as he could measure in three steps. When the present was promised the god turned into a giant and made two steps which covered the earth, the sky and the space between them. But he generously abstained from the third step leaving the underworld in the demon's domain.
6. Parashurama ("Rama with an axe"). Vishnu assumed a human image as a Brahman Jamadagni's son.Rama When wicked tsar Kartavirya robbed his father, Parashurama killed him. Kartavirya's sons in their turn killed Jamadagni, after that angry Parashurama 21 times exterminated all the men from the kshatriy(warriors) estate.
7. Rama, the prince of Ayodhy, a hero of the epic drama "Ramayana". Vishna assumed his image to save the world from the oppressions of demon Ravana. Rama is usually portrayed as a man with dark skin often armed with a bow and arrows. He is followed by his loving spouse Sita, the embodiment of feminine loyalty, his three devoted brothers: Lakshmana, Bharata and Shatrughna, and by Hanuman, the king of monkeys, his loyal friend and companion-in-arms. Rama is revered as the embodiment of an ideal husband, commander and a monarch.
8. Krishna, the most significant of Vishnu's incarnations. The stories from the life of this deity are Krishna most often referred to in dance. The most favorite scenes are his child's roguery as for instance stealing butter from Yashoda (his foster mother) or his divine love with gopis (devotees) among whom the Radha was the most beloved.
The more detailed description of Krishna's life can be found in the most famous epic work Mahabharata.
9. Buddha, the latest Vishnu's incarnation in the past. According to "Gitagovinda" written by the great poet Jayadeva, Vishnu assumed the image of Buddha out of compassion to animals in order to put an end to the bloody animal offerings.
10. Kalki - the future incarnation. Towards the end of our morbid era Vishnu will appear as a man riding on a white horse with a blazing sword in his hand. He will condemn sinners, reward the virtuous ones and revive Satya Yuga ("the golden age").
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