How Volcanic Eruption Causes Lightning !!!!

Although the phenomenon is fairly common and has been photographed since the 1940s, when Mount Vesuvius erupted in Italy, it is not found in all types of volcanic eruptions, says Dr Adele Crozier, of Geosciences Australia.

"It's mostly associated with explosive volcanism, so the grey eruptions, like Shinmoedake in Japan, or the one in Iceland in 2010. The ones that actually generate this highly fragmented magma, volcanic ash, in the atmosphere."

While many news organisations report these events as simultaneous volcanic eruptions and electrical storms, Crozier says that's actually not the case.

"A lot of people think it's two extreme events, but the lightning strikes occur inside the eruption column itself and they're actually caused by the charged ash particles that are being ejected into the column by the volcano."

There are, however, a few unknowns in the process.

"Volcanologists are not completely sure exactly what the mechanism is for generating lightning inside a volcanic eruption," Crozier says.

Lightning is usually caused by the flow of electricity between two masses that have opposing positive and negative charges. Volcanic lightning, however, is unusual because, as the photographs show, the bolts start and end within the eruption column and do not connect to a solid mass, she says.

"The first thing is, you have to consider exactly what's inside an eruption column. It's usually a collection of hot glassy ash particles, steam and gas. Together they are erupted into the atmosphere and there are a lot of different sizes of ash particles," Crozier says.

She says that before there can be lightning, the particles need to become ionised.

"When … all that ash is ejected into the atmosphere [in a volcanic eruption] the particles begin as neutral, but by colliding with one another they can actually transfer charges between each other and turn into positive or negative masses."

The ionisation process, however, isn't enough on its own. To create lightning, she says the particles must also separate and create a gap between them.

"By providing that separation between the positive and negative particles, you provide a conduit for electricity to flow. That's when you get lightning," she explains.

How these particles actually separate is unclear.

"A lot of volcanologists believe that it has to do with how quickly different sized particles settle," Crozier says.

"Some people have theorised that larger particles might have positive charges and smaller particles might have more negative charges and as larger particles fall out of the atmosphere faster, that might create the separation needed to generate lightning. It's still a mystery as to exactly what that mechanism is."

Dr Adele Crozier, of Geosciences Australia was interviewed by Carl Holm.

OBLER”S PARADOX !

One of the simplest paradox. Obler’s paradox begins by asking WHY NIGHT SKY IS BLACK ???

Kepler was soo disturbed by this paradox that he simply postulated that the universe was finite, enclosed within a shell, hence only a finite amount of starlight could ever reach over eyes !

BENTLEY”S theory (or paradox)

According to Richard Bentley (in 1692) . If the universe was finite , then the night sky, instead of being eternal and static, should be a scene of incredible carnage , as stars plowed into each other and coalesced into a fiery superstar.

But Bentley, also pointed out that if the universe was infinite, then the force on any object, tugging it to the left or right, would also be infinite and therefore the stars should be ripped to shreds in “fiery” cataclysm.

This paradox  was a disaster for the young theory being proposed by NEWtON

And in some way this paradox, Some how checkmated Newton !

“AGE OF UNIVERSE”

The WMAP satellite today has measured the echo of the big bang itself to give us the most authoritative age of the universe. The WMAP data reveals that the universe was born in a fiery explosion that took place 13.7 billion years ago.

(over the years, one of the most embarrassing facts plaguing cosmology has been that the age of the universe was often computed to be younger than the age of planets and stars, due to faulty data. Previous estimates for the age of the universe were as low as !-2 billion years, which contradicted the age of earth [4.5 billion years] and the oldest stars [12 billion years] !!!!!!!!

{SOURCE – pg 11 of book “parallel universe” by DR. Michio kaku}

Nebulae- their formation and types !

Definition and history of a Nebula

The word "nebula" comes from ancient roman and European times when Latin was the principal language in the western world, and was used to define most sceintific terms. In Latin, the word nebula means "a cloud, or a mist, or a vapor". Nebulae is just the plural of nebula. Nebulae were theorized before the invention of the telescope. In ancient times, the Romans looked up at the skies, and defined all the faint, less glowing stars nebulae. The reason the Romans picked the name "nebula" was mainly for a nebula's property of being a cloud, or mist of gas. After the invention of the telescope in the 17th century, many astronomers defined many of the so-called "nebulous" objects as living, bright stars. But there were still many other nebulae that the astronomers could not define. Even today, many astronomers still can not identified many of the "nebulous" stellar bodies that they have found. These bodies are still called nebulae today.

Properties of Nebulae

Nebulae do not have any concrete properties, but their description is quite simple. Nebulae are stellar bodies that have not completely transformed into a star as well as they are also remnants of a stars. Nebulae are quite gaseous, clouds or mists of gas. They do form in many different ways, and there are many types of nebulae.

Types of Nebulae

There are five types of nebulae:

1. Reflection Nebulae
2. Emission Nebulae
3. Dark Nebulae
4. Planetary Nebulae

Reflection Nebulae

Reflection Nebulae have a very unique property. The dust and gas of this type of nebula does not emit its own light. Instead, it reflects light from nearby stars and/or galaxies. They are usually located near a really bright star in the sky.

Emission Nebulae

This type of star actually emits its own light, because of the radiation from stars within the nebulae. But the radiation emitted from the stars have a unique property. The radiation from the stars in the nebula is so strong that it can "excite" atoms that are within the nebulae, and the excited atoms will move from one energy level to the next. The result of this is the atoms emitting radiation as well.

Dark Nebulae

This type of Nebulae is different from a reflection nebulae and emission nebulae by which it absorbs some light from stars behind it. The light absorbed ends up heating the dust particles up, which results in the particles re-radiating, or emitting, some of the absorbed energy as infrared light.

Planetary Nebulae

Of all the nebulae described in this page, planetary nebulae are probably the most widely known nebula. They are formed when old stars of a size, similar to our Sun's size, have consumed most of their hydrogen fuel after billions of years. The star does not explode, but instead it ejects the gases at much lower speeds and at different times. As the star continues to cool and compress, the inner core of the star becomes very hot and explodes. The very high temperature radiation from the explosion causes the ejected gases to become radioactive. The end result is a star that glows.

ANDREA GHEZ .... first to prove existence of blackhole in centre of our galaxy

                                              (above video is of Andrea Ghez on TED)

Seeing the unseen (from 26,000 light-years away) is a specialty of UCLA astronomer Andrea Ghez. From the highest and coldest mountaintop of Hawaii, home of the Keck Observatory telescopes, using bleeding-edge deep-space-scrying technology, Ghez handily confirmed 30 years of suspicions of what lies at the heart of the Milky Way galaxy -- a supermassive black hole, which sends its satellite stars spinning in orbits approaching the speed of light. 

Ghez received a MacArthur "genius grant" in 2008 for her work in surmounting the limitations of earthbound telescopes. Early in her career, she developed a technique known as speckle imaging, which combined many short exposures from a telescope into one much-crisper image. Lately she's been using adaptive optics to further sharpen our view from here -- and compile evidence of young stars at the center of the universe.

"Few people know the center of the Milky Way -- some 26,000 light-years from Earth -- as intimately as Andrea Ghez." 

What is Speckle imaging ???? here is the answer !!!
 Speckle imaging (also known as video astronomy) describes a range of high-resolution astronomical imaging techniques based either on the shift-and-add ("image stacking") method or on speckle interferometry methods. These techniques can dramatically increase the resolution of ground-based telescopes.

Galactic collisions !!!!!!

Many galaxies are members of groups or clusters. Since groups and clusters contain so many galaxies relatively close together, it should not be surprising that galaxies sometimes collide with each other. In fact, the Milky Way Galaxy is colliding with the Sagittarius Dwarf Galaxy right now (see the SDSS First Discoveries for more information). Although galaxy collisions are common, stars in each galaxy are so far apart that collisions between stars are very rare.
Even if galaxies don't actually collide, though, they can still affect one another. When two galaxies pass close to one another, the force of gravity they exert on one another can cause both galaxies to bend out of shape. Both crashes and near misses between galaxies are referred to as "interactions."

At the right, you can see two galaxies interacting. You can see they are being distorted by the gravitational interaction between them. Can you imagine what they might have looked like before they interacted?
When two galaxies interact, clouds of gas inside each galaxy may become compressed. Compressing the clouds can cause them to collapse under their own gravity, turning into stars. This process can lead to a burst of star formation in interacting galaxies, leaving a new generation of stars in a galaxy where normal star formation may have ceased long ago.
Galaxy collisions take hundreds of millions of years, so we can't watch them happen. Instead, we use computer simulations to show us what would happen if two galaxies collided in a certain way. If you are interested in learning about galaxy collisions, you can use a web-based simulation tool to model them.

What Happens When Supermassive Black Holes Collide?

As galaxies merge together, you might be wondering what happens with the supermassive black holes that lurk at their centres. Just imagine the forces unleashed as two black holes with hundreds of millions of times the mass of the Sun come together. The answer will surprise you. Fortunately, it’s an event that we should be able to detect from here on Earth, if we know what we’re looking for.

Most, if not all, galaxies in the Universe seem to contain supermassive blackholes. Some of the biggest can contain hundreds of millions, or even billions of times the mass of our own Sun. And the environments around them can only be called “extreme”. Researchers think that many could be spinning at the maximum rates predicted by Einstein’s theories of relativity – a significant fraction of the speed of light.

As two galaxies merge, their supermassive black holes have to eventually interact. Either through a direct collision, or by spiraling inward until they eventually merge as well.

And that’s when things get interesting.

According to simulations made by G.A. Shields from the University of Texas, Austin, and E.W. Bonning, from Yale University, the result is often a powerful recoil. Instead of coming together nicely, the forces are so extreme that one black holes is kicked away at a tremendous velocity.

The maximum kick happens with the two black holes are spinning in opposite directions, but they’re on the same orbital plane – imagine two spinning tops coming together. In a fraction of a second, one black hole is given enough of a kick to send it right out of the newly merged galaxy, never to return.

As one black hole is given a kick, the other receives a tremendous amount of energy, injected into the disk of gas and dust surrounding it. The accretion disk will blaze with a soft X-ray flare that should last thousands of years.

So even though mergers between supermassive black holes are extremely rare events, the afterglow lasts long enough that we should be able to detect a large number out there in space right now. The researchers estimate that there could be as many as 100 of these recent recoil events happening within 5 billion light-years of the Earth.

Their recently updated journal article, entitled Powerful Flares from Recoiling Black Holes in Quasars will be published in an upcoming issue of the Astrophysics Journal.

Original Source: Arxiv