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Just_Charlie
Advanced Member
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8577 Posts
Member since 07/01/2008 |
 Posted - 22/11/2013 : 01:17:52
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Quasars: Brightest Objects in the Universe
Shining so brightly that they eclipse the ancient galaxies that contain them, quasars are distant objects powered by black holes a billion times as massive as our sun. These powerful dynamos have fascinated astronomers since their discovery half a century ago.
In the 1930s, Karl Jansky, a physicist with Bell Telephone Laboratories, discovered that the static interference on transatlantic phone lines was coming from the Milky Way. By the 1950s, astronomers were using radio telescopes to probe the heavens, and pairing their signals with visible examinations of the heavens.
However, some of the smaller point-source objects didn't have a match. Astronomers called them "quasi-stellar radio sources," or "quasars," because the signals came from one place, like a star. Naming them didn't help determine what these objects were. It took years of study to realize that these distant specks, which seemed to indicate stars, are created by particles accelerated at velocities approaching the speed of light.
Scientists now suspect that the tiny, point-like glimmers are actually signals from galactic nuclei outshining their host galaxies. Quasars live only in galaxies with supermassive black holes — black holes that contain billions of times the mass of the sun. Although light cannot escape from the black hole itself, some signals can break free around its edges. While some dust and gas fall into the black hole, other particles are accelerated away from it at near the speed of light. The particles stream away from the black hole in jets above and below it, transported by one of the most powerful particle accelerators in the universe.
Most quasars have been found billions of light-years away. Because it takes light time to travel, studying objects in space functions much like a time machine; we see the object as it was when light left it, billions of years ago. Thus, the farther away scientists look, the farther back in time they can see. Most of the more than 2,000 known quasars existed in the early life of the galaxy. Galaxies like the Milky Way may once have hosted a quasar that has long been silent.
Quasars emit energies of millions, billions, or even trillions of electron volts. This energy exceeds the total of the light of all the stars within a galaxy. The brightest objects in the universe, they shine anywhere from 10 to 100,000 times brighter than the Milky Way.
Quasars are part of a class of objects known as active galactic nuclei (AGN). Other classes include Seyfert galaxies and blazars. All three require supermassive black holes to power them.
Seyfert galaxies are the lowest energy AGN, putting out only about 100 kiloelectronvolts (KeV). Blazars, like their quasar cousins, put out significantly more energy.
Many scientists think that the three types of AGNs are the same objects, but with different perspectives. While the jets of quasars seem to stream at an angle generally in the direction of Earth, blazars may point their jets directly toward the planet. Although no jets are seen in Seyfert galaxies, scientists think this may be because we view them from the side, so all of the emission is pointed away from us and thus goes undetected. |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 29/11/2013 : 11:25:18
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This image depicts bright blue newly formed stars that are blowing a cavity in the centre of a fascinating star-forming region known as N90.
The high energy radiation blazing out from the hot young stars in N90 is eroding the outer portions of the nebula from the inside, as the diffuse outer reaches of the nebula prevent the energetic outflows from streaming away from the cluster directly. Because N90 is located far from the central body of the Small Magellanic Cloud, numerous background galaxies in this picture can be seen, delivering a grand backdrop for the stellar newcomers. The dust in the region gives these distant galaxies a reddish-brown tint. |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 04/12/2013 : 00:43:31
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ESA/Hubble Flashback: The Cygnus Loop, which covers a region on the sky six times the diameter of the full Moon. |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 05/12/2013 : 01:00:07
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This bright cluster of stars is 47 Tucanae (NGC 104)
located around 15 000 light-years away from us and contains millions of stars, some of which are unusual and exotic. |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 05/12/2013 : 01:04:15
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Could launching a mission to Venus help reveal exactly how the moon formed nearly 4.5 billion years ago?
Planetary scientists think the moon coalesced out of material blasted into space when a large object slammed into the proto-Earth in the early days of the solar system. But the details of this mega-collision remain fuzzy, with several different theories competing to explain how it all went down.
The original giant-impact theory, which has been in development since the 1970s, posits that a Mars-size object struck Earth with a slow and glancing blow long ago. In this scenario, the moon formed from a disk
of material ejected largely from the mysterious impactor's mantle
http://www.space.com/23827-moon-formation-mystery-venus-mission.html?cmpid=514630_20131205_15281484
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~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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mladjo
Advanced Member
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Croatia
20013 Posts
Member since 15/04/2007 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 11/12/2013 : 00:49:36
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The Rosette Nebula is a large, circular hydrogen region located near one end of a giant molecular cloud in the Monoceros region of the Milky Way Galaxy. The open cluster, NGC 2244, is closely associated with the nebulosity, the stars having been formed from the nebula's matter. The Nebula is about 100 light-years across and is about 5000 light-years away. |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 11/12/2013 : 00:52:12
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UGC10214 Tadpole Galaxy is a disrupted barred spiral galaxy located 400 million light years from Earth toward the northern constellation Draco. It is hypothesized that a more compact intruder galaxy crossed in front of the Tadpole Galaxy—from left to right from the perspective of Earth—and was slung around behind the Tadpole by their mutual gravitational attraction. During this close encounter, tidal forces drew out the spiral galaxy’s stars, gas, and dust, forming the conspicuous tail. The intruder galaxy itself, estimated to lie about 300 thousand light-years behind the Tadpole, can be seen through foreground spiral arms at the upper left. Following its terrestrial namesake, the Tadpole Galaxy will likely lose its tail as it grows older, the tail’s star clusters forming smaller satellites of the large spiral galaxy.
This Image is produced with the HST data from the Hubble Legacy Archives |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 11/12/2013 : 00:59:26
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How is a star born?
A star is born when atoms of light elements are squeezed under enough pressure for their nuclei to undergo fusion. All stars are the result of a balance of forces: the force of gravity compresses atoms in interstellar gas until the fusion reactions begin. And once the fusion reactions begin, they exert an outward pressure. As long as the inward force of gravity and the outward force generated by the fusion reactions are equal, the star remains stable.
Clouds of gas are common in our galaxy and in other galaxies like ours. These clouds are called nebulae. A typical nebula is many light-years across and contains enough mass to make several thousand stars the size of our sun. The majority of the gas in nebulae consists of molecules of hydrogen and helium--but most nebulae also contain atoms of other elements, as well as some surprisingly complex organic molecules. These heavier atoms are remnants of older stars, which have exploded in an event we call a supernova. The source of the organic molecules is still a mystery.
Irregularities in the density of the gas causes a net gravitational force that pulls the gas molecules closer together. Some astronomers think that a gravitational or magnetic disturbance causes the nebula to collapse. As the gases collect, they lose potential energy, which results in an increase in temperature.
As the collapse continues, the temperature increases. The collapsing cloud separates into many smaller clouds, each of which may eventually become a star. The core of the cloud collapses faster than the outer parts, and the cloud begins to rotate faster and faster to conserve angular momentum. When the core reaches a temperature of about 2,000 degrees Kelvin, the molecules of hydrogen gas break apart into hydrogen atoms. Eventually the core reaches a temperature of 10,000 degrees Kelvin, and it begins to look like a star when fusion reactions begin. When it has collapsed to about 30 times the size of our sun, it becomes a protostar.
When the pressure and temperature in the core become great enough to sustain nuclear fusion, the outward pressure acts against the gravitational force. At this stage the core is about the size of our sun. The remaining dust envelope surrounding the star heats up and glows brightly in the infrared part of the spectrum. At this point the visible light from the new star cannot penetrate the envelope. Eventually, radiation pressure from the star blows away the envelope and the new star begins its evolution. The properties and lifetime of the new star depend on the amount of gas that remains trapped. A star like our sun has a lifetime of about 10 billion years and is just middle-aged, with another five billion years or so left.
Stars form from the gravitational collapse of large clouds of interstellar material. In fact, the space between stars is not empty; it is nearly empty, but not entirely. Interstellar matter, that found lying between the stars, is made from gas and dust. Granted, only about 10 percent of the mass in our Milky Way galaxy is made up of interstellar matter. But this material, as tenuous as it is, exerts a gravitational force, and as a result, it will begin to pull itself together.
As this accretion continues, the gravity becomes increasingly strong because its strength rises as the mass increases and the distance of the individual atoms decreases. Eventually this interstellar matter entirely collapses in on itself. The material at the very center is compressed by the infalling material on the outside, pushing down to get to the center. And this compression heats up the center of the collapsing cloud.
At some point, the temperature gets so extremely high at the center, it triggers a fusion reaction. All the material that has fallen in then evolves into a hot, bright star. The star will continue to shine as long as there is hydrogen gas to fuse through nuclear reactions, and the gravitational pressure pushing inward keeps the atoms very hot and tightly packed at the center. |
~ Prvo suputnik onda put ~
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mladjo
Advanced Member
Croatia
20013 Posts
Member since 15/04/2007 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 15/12/2013 : 01:49:49
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Hydrogen squeezed from stone could be new energy source
Scientists from the University of Lyon have discovered a new way to split hydrogen gas from water, using rocks.
The method promises a new green energy source, providing copious hydrogen from a simple mixture of rock and water.
It speeds up a chemical reaction that takes geological timescales in nature.
In the reaction, the mineral olivine strips one oxygen and hydrogen atom from an H2O molecule to form a mineral called serpentine, releasing the spare hydrogen atom.
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http://www.bbc.co.uk/news/science-environment-25349983 |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
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mladjo
Advanced Member
Croatia
20013 Posts
Member since 15/04/2007 |
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panzer
Advanced Member
12516 Posts
Member since 18/05/2005 |
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 31/12/2013 : 01:32:47
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Orion nebula
"So many colours gathered together, to provoke your smile and touch you soft as a feather, forgive me my love I am not with you when wonders rise and fall, now give this pandemonium your blessed smile, there is heaven for you but forgive me for a while, I must die released now, as I already saw you smile" ... |
~ Prvo suputnik onda put ~
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Just_Charlie
Advanced Member
8577 Posts
Member since 07/01/2008 |
Posted - 31/12/2013 : 01:39:54
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A "Rose" of a Galaxy
In celebration of the 21st anniversary of the Hubble Space Telescope's deployment into space, astronomers at the Space Telescope Science Institute pointed Hubble's eye to an especially photogenic group of interacting galaxies called Arp 273. Pictured here is the larger of the two galaxies, known as UGC 1810. It has a disk that is tidally distorted into a rose-like shape by the gravitational tidal pull of the companion galaxy below it, known as UGC 1813. A swath of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light. A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in color) on one side to clumpy and extremely blue on the other. UGC 1810 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. |
~ Prvo suputnik onda put ~
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panzer
Advanced Member
12516 Posts
Member since 18/05/2005 |
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SHINING LIKE BRIGHT DIAMONDS, THE GALAXIES...
