Wednesday, January 23, 2008

Cosmic Interactions

Credit: ESA Cosmic Interactions NGC 7173, 7174 and 7176

ESO's Very Large Telescope (VLT) images triplet of dancing galaxies intertwined in a cosmic dance.

The three galaxies: NGC 7173 (top), 7174 (bottom right) and 7176 (bottom left), are located 106 million light-years away towards the constellation of Piscis Austrinus (the 'Southern Fish').

NGC 7173 and 7176 are elliptical galaxies, while NGC 7174 is a spiral galaxy with quite disturbed dust lanes and a long, twisted tail.

This seems to indicate that the two bottom galaxies are currently interacting, with NGC 7176 providing fresh material to NGC 7174. Matter present in great quantity around the triplet's members also points to the fact that NGC 7176 and NGC 7173 have interacted in the past.

Astronomers have suggested that The three galaxies will finally merge into a giant 'island universe', tens to hundreds of times as massive as our own Milky Way.

The triplet is part of a so-called 'Compact Group', as compiled by Canadian astronomer Paul Hickson in the early 1980s. The group, which is the 90th entry in the catalogue and is therefore known as HCG 90, actually contains four major members. One of them - NGC 7192 - lies above the trio, outside of this image, and is another peculiar spiral galaxy.

Compact groups are small, relatively isolated, systems of typically four to ten galaxies in close proximity to one another. Another striking example is Robert's Quartet. Compact groups are excellent laboratories for the study of galaxy interactions and their effects, in particular the formation of stars.

As the striking image reveals, there are many other galaxies in the field. Some are distant ones, while others seem to be part of the family. Studies made with other telescopes have indeed revealed that the HCG 90 group contains 16 members, most of them much smaller in size than the four members with an entry in the NGC catalogue.

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Saturday, January 19, 2008

Pools of Invisible Matter

Super Clusters Credit: Hubble NASA, ESA, C. Heymans (University of British Columbia), M. Gray (University of Nottingham), and the STAGES Collaboration

NASA's Hubble Space Telescope is helping astronomers to dissect one of the largest structures in the universe, in a quest to understand the violent lives of galaxies, and providing indirect evidence of unseen dark matter tugging on galaxies in the crowded, rough-and-tumble environment of a massive supercluster of hundreds of galaxies.

The images are part of the Space Telescope Abell 901/902 Galaxy Evolution Survey (STAGES), which covers one of the largest patches of sky ever observed by the Hubble telescope.

The area surveyed is so wide that it took 80 Hubble images to cover the entire STAGES field. The new work is led by Meghan Gray of the University of Nottingham in the United Kingdom and Catherine Heymans of the University of British Columbia in Vancouver, along with an international team of scientists.

The Hubble study pinpointed four main areas in the supercluster where dark matter has pooled into dense clumps, totaling 100 trillion times the Sun's mass. These areas match the location of hundreds of old galaxies that have experienced a violent history in their passage from the outskirts of the supercluster into these dense regions. These galaxies make up four separate galaxy clusters.

The dark matter map was constructed by measuring the distorted shapes of over 60,000 faraway galaxies.
[+/-] Click here to expand

To reach Earth, the galaxies' light traveled through the dark matter that surrounds the supercluster galaxies and was bent by the massive gravitational field. Heymans used the observed, subtle distortion of the galaxies' shapes to reconstruct the dark matter distribution in the supercluster using a method called weak gravitational lensing. The dark matter map is 2.5 times sharper than a previous ground-based survey of the supercluster.

On Earth, the pace of quiet country life is vastly different from the hustle of the big city. In the same way, galaxies living lonely isolated lives look very different from those found in the most crowded regions of the universe, like a supercluster. "We've known for a long time that galaxies in crowded environments tend to be older, redder, and rounder than those in the field," Gray said. "Galaxies are continually drawn into larger and larger groups and clusters by the inevitable force of gravity as the universe evolves."

In such busy environments galaxies are subject to a life of violence: high-speed collisions with other galaxies; the stripping away of gas, the fuel supply they use to form new stars; and distortion due to the strong gravitational pull of the underlying invisible dark matter. "Any or all of these effects may play a role in the transformation of galaxies, which is what we're trying to determine," Gray said.

The STAGES survey's simultaneous focus on both the big picture and the details can be likened to studying a big city. "It's as if we're trying to learn everything we can about New York City and New Yorkers," Gray explained. "We're examining large-scale features, like mapping the roads, counting skyscrapers, monitoring traffic. At the same time we're also studying the residents to figure out how the lifestyles of people living downtown differ from those out in the suburbs. But in our case the city is a supercluster, the roads are dark matter, and the people are galaxies."


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Wednesday, January 16, 2008

Spinning Black Holes

Results from NASA's Chandra X-ray Observatory, combined with new theoretical calculations, provide one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly.

The images below show 4 out of the 9 large galaxies included in the Chandra study, each containing a supermassive black hole in its center.

The Chandra images show pairs of huge bubbles, or cavities, in the hot gaseous atmospheres of the galaxies, created in each case by jets produced by a central supermassive black hole. Studying these cavities allows the power output of the jets to be calculated. This sets constraints on the spin of the black holes when combined with theoretical models.

The Chandra images were also used to estimate how much fuel is available for each supermassive black hole, using a simple model for the way matter falls towards such an object. The artist's impression on the right side of the main graphic shows gas within a "sphere of influence" falling straight inwards towards a black hole before joining a rapidly spinning disk of matter near the center.

Most of the material in this disk is swallowed by the black hole, but some of it is swept outwards in jets (coloured blue) by quickly spinning magnetic fields close to the black hole.

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Sunday, January 13, 2008

The Moth

The Moth. Credit: Hubble

The object resembling a giant moth floating in space, with a wingspan of about 22 billion miles, is actually a dust disk encircling the nearby, young star HD 61005. Dubbed "The Moth" - its shape is produced by starlight scattering off dust.

Dust disks around roughly 100-million-year-old stars like HD 61005 are typically flat, pancake-shaped structures where planets can form. But images taken with NASA's Hubble Space Telescope of "The Moth" are showing that some disks sport surprising shapes.

"We think HD 61005 is plowing through a local patch of higher-density gas in the interstellar medium, causing material within HD 61005's disk to be swept behind the star." "What effect this might have on the disk, and any planets forming within it, is unknown," said senior research scientist Dean Hines of the Space Science Institute in Corrales, New Mexico, and a member of the Hubble team that discovered the disk.

Hines called this possible collision "unusual, because we don't expect very much interstellar material to be in the solar neighbourhood. That's because the area through which our Sun is moving was evacuated within the past few million years by at least one supernova, the explosion of a massive star. Yet, here's evidence of dense material that's very close, only 100 light-years away."

Astronomers have found evidence that the environment in which a star forms influences its prospects for planet formation. Hubble has actually seen that young planet-forming disks can be affected directly by their environment.

The harsh stellar radiation from the Trapezium stars in the Orion Nebula has altered some disks. It is unclear, however, what effect passage through a cloud similar to the one in which HD 61005 finds itself would have on planet formation. Researchers have speculated that passage through dense regions of the interstellar medium could impact the atmospheres of evolving planets.
[+/-] Click here to expand

The Moth is part of a survey of Sun-like stars that Hines and collaborators observed with Hubble's Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and NASA's Spitzer Space Telescope to study the formation and evolution of planetary systems. Under the lead of Michael Meyer of the University of Arizona in Tucson, the team initially used Spitzer to look for heat radiation—the tell-tale sign of dust warmed by the star—to identify interesting star systems.

Hines then teamed with Glenn Schneider of the University of Arizona to use Hubble's high- contrast imaging capability of the NICMOS coronagraph to image these disks and reveal where the dust detected by Spitzer resides. The NICMOS coronagraph blocked out the starlight so that astronomers could see details in the surrounding disk.

"These symbiotic capabilities, uniquely implemented in NASA's Great Observatories, provide astronomers with the powerful observational tools to study the circumstellar environments of potentially planet-forming systems," Schneider said.

Added Meyer: "Combining observations from these two spacecraft gives us information about the composition of the dust grains, whether they're icy or sandy, or whether they're like the sooty smoke particles rising from a chimney. The composition and sizes of the dust can tell us a lot about the dynamics and evolution of a solar system. In our solar system, for example, astronomers have evidence of rocks smashing into each other and generating dust, as in the asteroid and Kuiper belts. We're seeing these same processes unfold in other planetary systems."


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Tuesday, January 08, 2008

Orphaned Star Clusters

Hubble: Orphaned Star Clusters - Click on Image to Enlarge

[LEFT] A GALEX ultraviolet image of the interacting galaxies M81 and M82, which lie 12 million light-years away in the constellation Ursa Major. The gravity from each galaxy dramatically affected the other during their last close encounter, 200 million years ago.

Gas density waves rippling around M81 make it a grand design spiral. M82 is undergoing a starburst at its core, creating glowing fingers of hydrogen.

[RIGHT] A Hubble Space Telescope visible light image of bright blue star clusters found along a wispy bridge of gas that was tidally stretched between the two galaxies, and a third companion galaxy not seen in this picture. This is not the place astronomers expect to find star clusters because the density of gas is so low. Turbulence in the gas may have enhanced the density locally to trigger starbirth.

The "blue blobs" are clumped together in a structure called Arp's Loop. Hubble reveals the clusters contain the equivalent of five Orion Nebulae. A Hubble plot of the stellar population in the clusters yields an age of approximately 200 million years, which coincides with the epoch of the collision.

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Sunday, January 06, 2008

The Three Magi

The Three Magi

Till the present, from Ancient Times,
Since Man became Man, there have been stargazers
till the present, from Ancient Times.

Everyday we can see further and further, as we unravel
the inmensity of this Universe and the great beyond.
Everyday we unravel & reveal new secrets of what we see
the beauty of life, and all that in an instant came to be.

So here's many more best wishes from me to thee.
May this year be filled with much joy & many gifts.

35th Carnival of Space from Music of the Spheres

Tuesday, January 01, 2008

The Magic Circle

Magic Circle, by John William Waterhouse (1886)

Ceating a magic circle is known as casting a circle, circle casting. There are many different techniques for casting a circle.

The common feature of these practices is that a barrier of energy is traced in a circle around the working area. Some traditions say that one must go around the circle deosil three times. There are also various starting points based on cardinal directions. A typical size for a circle is nine feet and an individual's circle is five feet in diameter, though the size can vary depending on the purpose of the circle, and the preference of the caster.

Some practitioners choose to mark the physical boundary of their circle, either before or prior to the actual casting. This can be done using a cord, a chalk line, a line drawn in the soil, or small objects such as stones.

Some practitioners mark the four cardinal points with candles, either white, or of colours representative of the elements: North: green for the element of Earth; East: yellow for the element of Air; South: red for the element of Fire; West: blue for the element of Water.

Though some practitioners, associate North with Air and East with Earth. Generally, as with most magical practices, an incantation is recited stating the purpose and nature of the circle.

Traditionally, circles were used by ritual magicians to form a protective barrier between themselves and what they summoned. Nowadays, the circle has taken the more benign function of containing the energy raised during the ritual that follows.

As more and more energy is raised from chanting and dancing the energy becomes more concentrated. After the circle has been cast it is believed that it forms a sphere of energy, which intersects the ground at its equator. This shouldn't be confused with the cone of power, a method of raising energy.

Circles can also be used as barriers for non-magical work such as meditation. The barrier is fragile and sensitive to things passing through it. Leaving or passing through the circle often weakens or dispels the barrier. This is referred to as "breaking the circle". It is generally advised that practitioners don't leave the circle unless absolutely necessary.

The Magic Circle is a British organisation dedicated to magic. Its headquarters are in London, and professional magicians who want to join need to first demonstrate their skills to existing members. There are currently approximately 1500 members (including Charles, Prince of Wales) in 41 countries.

The Magic Circle was founded in 1905 after a meeting of 23 amateur and professional magicians at London's Pinoli's Restaurant. The first official meeting was held at The Green Man public house in Soho, but meetings were later held in a room at St. George's Hall in Langham Place. The current president (2007) is Alan Shaxon whose term of office will end in September 2008.

The motto of the society is the Latin indocilis privata loqui, which may be roughly translated as "not apt to disclose secrets"; Members give their word not to wilfully disclose magic secrets other than to bona fide students of magic. Anyone breaking this or any other rule may be subject to expulsion from the society.

Since 1998, The Magic Circle Headquarters building in central London has also been available for use as a venue for meetings and corporate entertainment. It has been voted best unusual venue by the hospitality industry. A virtual tour of the building and information are available online.

Happy New Year!