Wednesday, October 31, 2007

The Ghost Head Nebula

NGC 2080. Credit: Mohammad Heydari-Malayeri (Observatoire de Paris) et al

This image from NASA's Hubble Space Telescope reveals a vibrant green and red nebula far from Earth, where nature seems to have put on the traditional colours of the season. These colours, produced by the light emitted by oxygen and hydrogen, help astronomers investigate the star-forming processes in nebulas such as NGC 2080.

The light from the nebula captured in this image is emitted by two elements, hydrogen and oxygen. The red and the blue light are from regions of hydrogen gas heated by nearby stars. The green light on the left comes from glowing oxygen. The energy to illuminate the green light is supplied by a powerful stellar wind (a stream of high-speed particles) coming from a massive star just outside the image.

The white region in the center is a combination of all three emissions and indicates a core of hot, massive stars in this star-formation region. The intense emission from these stars has carved a bowl-shaped cavity in the surrounding gas.

In the white region, the two bright areas (the "eyes of the ghost") - named A1 (left) and A2 (right) - are very hot, glowing "blobs" of hydrogen and oxygen. The bubble in A1 is produced by the hot, intense radiation and powerful stellar wind from a single massive star. A2 has a more complex appearance due to the presence of more dust, and it contains several hidden, massive stars. The massive stars in A1 and A2 must have formed within the last 10,000 years, since their natal gas shrouds are not yet disrupted by the powerful radiation of the newly born stars.

This "enhanced colour" picture spanning 55 light years in the above image is composed of three narrow-band-filter images obtained with Hubble's Wide Field Planetary Camera 2. The colours are red (ionized hydrogen, H-alpha, 1040 seconds), green (ionized oxygen, 1200 seconds) and blue (ionized hydrogen, H-beta, 1040 seconds).

The Ghost Head Nebula NGC 2080 is a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way.

Halloween's ancient & astronomical origins date back to the ancient Celtic festival of Samhain (pronounced sow-in).
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The Celts, who lived 2,000 years ago in the area that is now Ireland, the United Kingdom, and northern France, celebrated their new year on November 1. This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31, they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth. In addition to causing trouble and damaging crops, Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. For a people entirely dependent on the volatile natural world, these prophecies were an important source of comfort and direction during the long, dark winter.

To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities.

During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other's fortunes. When the celebration was over, they re-lit their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.

By A.D. 43, Romans had conquered the majority of Celtic territory. In the course of the four hundred years that they ruled the Celtic lands, two festivals of Roman origin were combined with the traditional Celtic celebration of Samhain.

The first was Feralia, a day in late October when the Romans traditionally commemorated the passing of the dead. The second was a day to honor Pomona, the Roman goddess of fruit and trees. The symbol of Pomona is the apple and the incorporation of this celebration into Samhain probably explains the tradition of "bobbing" for apples that is practiced today on Halloween.

By the 800s, the influence of Christianity had spread into Celtic lands. In the seventh century, Pope Boniface IV designated November 1 All Saints' Day, a time to honor saints and martyrs. It is widely believed today that the pope was attempting to replace the Celtic festival of the dead with a related, but church-sanctioned holiday. The celebration was also called All-hallows or All-hallowmas (from Middle English Alholowmesse meaning All Saints' Day) and the night before it, the night of Samhain, began to be called All-hallows Eve and, eventually, Halloween. Even later, in A.D. 1000, the church would make November 2 All Souls' Day, a day to honor the dead. It was celebrated similarly to Samhain, with big bonfires, parades, and dressing up in costumes as saints, angels, and devils. Together, the three celebrations, the eve of All Saints', All Saints', and All Souls', were called Hallowmas.

Seeing Colour in Nebulae from A Quantum Diaries Survivor
Celestial Mandrill Is A Cosmic Ghost from Scientific Blogging
Astronomers simulate life & death in the Universe from Science Daily

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Tuesday, October 30, 2007

Dancing With The Stars

Arp 87. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Two galaxies perform an intricate dance in this new Hubble Space Telescope image. The galaxies, containing a vast number of stars, swing past each other in a graceful performance choreographed by gravity.

The pair, known collectively as Arp 87, is one of hundreds of interacting and merging galaxies known in our nearby universe.
Arp 87 was originally cataloged by astronomer Halton Arp in the mid 1960s. Arp's Atlas of Peculiar Galaxies is a compilation of astronomical photographs using the Palomar 200-inch Hale and the 48-inch Samuel Oschin telescopes.

The resolution in the Hubble image shows exquisite detail and fine structure that was not observable when Arp 87 was first cataloged in the 1960s.

The two main players comprising Arp 87 are NGC 3808 on the right (the larger of the two galaxies) and its companion NGC 3808A on the left. NGC 3808 is a nearly face-on spiral galaxy with a bright ring of star formation and several prominent dust arms. Stars, gas, and dust flow from NGC 3808, forming an enveloping arm around its companion. NGC 3808A is a spiral galaxy seen edge-on and is surrounded by a rotating ring that contains stars and interstellar gas clouds. The ring is situated perpendicular to the plane of the host galaxy disk and is called a "polar ring."

As seen in other mergers similar to Arp 87, the corkscrew shape of the tidal material or bridge of shared matter between the two galaxies suggests that some stars and gas drawn from the larger galaxy have been caught in the gravitational pull of the smaller one. The shapes of both galaxies have been distorted by their gravitational interaction with one another.

Interacting galaxies often exhibit high rates of star formation. Many lines of evidence - colours of their starlight, intensity of emission lines from interstellar gas, far-infrared output from heated interstellar dust - support this fact. Some merging galaxies have the highest levels of star formation we can find anywhere in the nearby universe.

A major aspect of this excess star formation could be properly revealed only when Hubble turned its imaging capabilities toward colliding galaxies. Among the observatory's first discoveries was that galaxies with very active star formation contain large numbers of super star clusters - clusters more compact and richer in young stars than astronomers were accustomed to seeing in our galactic neighbourhood.

Arp 87 is in the constellation Leo, the Lion, approximately 300 million light-years away from Earth. These observations were taken in February 2007 with the Wide Field Planetary Camera 2. Light from four isolated wavelength ranges (centred around 450, 555, 656 and 814 nm) blue, green, red, and infrared ranges was composited together to form this colour image.

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Sunday, October 28, 2007

Essence of Living

Horse - courtesy of Katie @ Katie's Poetry Corner

Doesn't take a horse long to learn
that into four legs a horse is born

Doesn't take a horse long to learn
that head and tail a horse can turn

Doesn't take a horse long to learn
a horse full of energy to run & burn

Doesn't take a horse long to learn
that to run & gallop a horse is born

But can the horse remember who or what the horse has been
Side by Side from Anna-lys @ Anna-lys blogspot
Being Present - from Pandabonium @ Pacific Islander
Other universes may be detectable from World of Science

Friday, October 26, 2007

Distant Ancient Black Holes

Hundreds of "missing" black holes have been found lurking in dusty galaxies located 9 billion to 11 billion light-years away and existed at a time when the universe was between 2.5 and 4.5 billion years old.

"Active, supermassive black holes were everywhere in the early universe," said study team member Mark Dickinson of the National Optical Astronomy Observatory in Tuscon, Ariz. "We had seen the tip of the iceberg before in our search for these objects. Now, we can see the iceberg itself."

The finding, detailed in two studies published in the Nov. 10 issue of Astrophysical Journal, is the first direct evidence that most, if not all, massive galaxies in the distant universe spent their youths constructing supermassive black holes at their cores.

It could also help answer fundamental questions about how massive galaxies such as our Milky Way evolved.

Using NASA's Chandra X-ray and Spitzer Space Telescopes, the team detected unusually high levels of infrared light emitted by 200 galaxies in the distant universe. They think the infrared light was created by material falling into "quasars"-supermassive black holes surrounded by doughnut-shaped clouds of gas and dust-at the center of the galaxies.

The new quasar-containing galaxies are all about the same mass as our Milky Way, but are irregular in shape. For decades, scientists have predicted that a large population of quasars should be found at those distances but had only spotted a few of them.

The newfound quasars confirm what scientists have suspected for years now: that supermassive black holes play a major role in star formation in massive galaxies. The observations suggest massive galaxies steadily build up their stars and black holes simultaneously until they get too big and the black holes suppress star formation.

The new quasars also suggest that collisions between galaxies might not be as important for galaxy evolution as once thought. "Theorists thought mergers between galaxies were required to initiate this quasar activity, but now we see that quasars can be active in unharassed galaxies," said study team member David Alexander of Durham University in the UK.
The improbable Universe by Pamela Star Stryder
Hubble Spies Shells of Sparkling Stars around Quasars
Texture discovered in Fabric of Space-Time from Scientific Blogging

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Thursday, October 25, 2007

A Glowing Pool of Light

Planetary Nebula NGC 3132 - Click on Image to Enlarge

NGC 3132 is a striking example of a planetary nebula. This expanding cloud of gas, surrounding a dying star, is known in the southern hemisphere as the "Eight-Burst" or the "Southern Ring" Nebula.

The name "planetary nebula" refers only to the round shape that many of these objects show when examined through a small visual telescope. In reality, these nebulae have little or nothing to do with planets, but are instead huge shells of gas ejected by stars as they near the ends of their lifetimes.

NGC 3132 is nearly half a light year in diameter, and at a distance of about 2000 light years is one of the nearer known planetary nebulae. The gases are expanding away from the central star at a speed of 9 miles per second.

This image, captured by NASA's Hubble Space Telescope, clearly shows two stars near the center of the nebula, a bright white one, and an adjacent, fainter companion to its upper right. (A third, unrelated star lies near the edge of the nebula.) The faint partner is actually the star that has ejected the nebula. This star is now smaller than our own Sun, but extremely hot. The flood of ultraviolet radiation from its surface makes the surrounding gases glow through fluorescence. The brighter star is in an earlier stage of stellar evolution, but in the future it will probably eject its own planetary nebula.

In the Heritage Team's rendition of the Hubble image, the colours were chosen to represent the temperature of the gases. Blue represents the hottest gas, which is confined to the inner region of the nebula. Red represents the coolest gas, at the outer edge. The Hubble image also reveals a host of filaments, including one long one that resembles a waistband, made out of dust particles which have condensed out of the expanding gases. The dust particles are rich in elements such as carbon. Eons from now, these particles may be incorporated into new stars and planets when they form from interstellar gas and dust. Our own Sun may eject a similar planetary nebula some 6 billion years from now.

Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)
Acknowledgment: R. Sahai (Jet Propulsion Lab)

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Tuesday, October 23, 2007


Credit: X-ray: NASA/CXC/Penn State/S.Park et al.; Optical: Pal.Obs. DSS

When a massive star explodes, it creates a shell of hot gas that glows brightly in X-rays. Chandra is able to observe the stellar debris, revealing the dynamics of the explosion.

Located about 20,000 light years away in the constellation of Centaurus, G292.0+1.8 is shown in beautiful detail in this new composite image. In colour is the Chandra X-ray Observatory image - easily the deepest X-ray image ever obtained of this supernova remnant - and in white is optical data from the Digitized Sky Survey.

Although considered a "textbook" case of a supernova remnant, the intricate structure shown here reveals a few surprises.

Near the center of G292.0+1.8 is the so-called pulsar wind nebula, most easily seen in high energy X-rays. This is the magnetized bubble of high-energy particles that surrounds the "pulsar", a rapidly rotating neutron star that remained behind after the original, massive star exploded. The narrow, jet-like feature running from north to south in the image is likely parallel to the spin axis of the pulsar.
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The pulsar is located slightly below and to the left of the center of G292.0+1.8. Assuming that the pulsar was born at the center of the remnant, it is thought that recoil from the lopsided explosion may have kicked the pulsar in this direction. However, the kick direction and the pulsar spin direction do not appear to be aligned, in contrast to apparent spin-kick alignments seen in some other supernova remnants.

Another key feature of this remnant is the long white line running from left to right across the center called the equatorial belt. This structure is thought to be created when the star - before it died - expelled material from around its equator via winds. The orientation of the equatorial belt suggests the parent star maintained the same spin axis both before and after it exploded.

One puzzling aspect of the image is the lack of evidence for thin filaments of high energy X-ray emission, thought to be an important site for cosmic ray acceleration in supernova remnants. These filaments are seen in other supernova remnants such as Cassiopeia A, Tycho and Kepler.

One explanation may be that efficient acceleration occurs primarily in very early stages of supernova remnant evolution, and G292.0+1.8, with an estimated age of several thousand years, is too old to show these effects. Casseiopeia A, Tycho and Kepler, with ages of several hundred years, are much younger.


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Monday, October 22, 2007

The Unseen & The Unknown

The enigmatic neutrinos are among the most abundant of the tiny particles that make up our universe. They are a billion times more abundant than the particles of which the earth and we humans are made.

Thus, to understand the universe, we must understand the neutrinos. Moving ghostlike, almost invisibly, through matter, these particles are very hard to pin down and study. However, dramatic progress has recently been made. Fermilab's Boris Kayser SLAC 2005 lecture.

Neutrinos are elementary particles that travel close to the speed of light, lack an electric charge, are able to pass through ordinary matter almost undisturbed, and are thus extremely difficult to detect. Neutrinos have a minuscule, but non-zero, mass too small to be measured as of 2007. Usually denoted by the Greek letter ν (nu).

Neutrinos are created as a result of certain types of radioactive decay or nuclear reactions such as those in the sun, in nuclear reactors, or when cosmic rays hit atoms. There are three types, or “flavours”, of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos; each type also has an antimatter partner, called an antineutrino. Electron neutrinos are generated whenever protons change into neutrons, while electron antineutrinos are generated whenever neutrons change into protons. These are the two forms of beta decay. Interactions involving neutrinos are generally mediated by the weak nuclear force.

Most neutrinos passing through the Earth emanate from the sun, and more than 50 trillion solar electron neutrinos pass through the human body every second.

But even if and when we can detect every elementary particle, component or 'strings' in the universe, will we be able to categorically state that nothing survives death, or that heaven is not sitting safely cocooned on some far off distant galaxy of the observable universe.

Perhaps this universe is not the best of all possible universes, but simply the universe we ‘observe’ while we are in it - and there are other universes, in One of which, neither time ageing or decay exist or are of any consequence.

After all, have we given a name to that which is beyond the cosmic event horizon or beyond the ‘observable’ universe, and what proof do we have that what is beyond is an empty ‘nothingness’ or vacuum. Even a Torus is surrounded by ’something’ on all sides.

Since with current technology, science & knowledge we are unable to travel the length of our solar system in a lifetime, should we therefore conclude that interstellar & intergalactic travel is ‘beyond’ the human race’s capability. Or should we be prepared to admit that there is much we do not know, and there are advances we hope to make. But even when we think we know everything, or at least everything about the observable universe (including visible matter and dark matter) will we ever be any closer to the great Unknown.
Magnetic Cocoons power energetic Cosmic Rays @ NewScientistSpace
Genesis - Clues to the Origins of the Solar System @ The Daily Galaxy
Enormous Bubbles of Plasma - trapped - within Earth's Magnetic Field

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Saturday, October 20, 2007

Scorpius - Sky Spectacular

Credit & Copyright: Stéphane Guisard. - Click Image to Enlarge

Scorpius more typically appears as a few bright stars in a well known but rarely pointed out zodiacal constellation.

To get a spectacular image like this, though, one needs a good camera, colour filters, and a digital image processor. To bring out detail, the above image not only involved long duration exposures taken in several colours, but one exposure in a very specific red colour emitted by hydrogen that brings out great detail.

The resulting image shows many breathtaking features. Vertically across the image left is part of the plane of our Milky Way Galaxy. Visible there are vast clouds of bright stars and long filaments of dark dust. Jutting out diagonally from the Milky Way in the image center are dark dust bands known as the Dark River.

This river connects to several bright stars on the right that are part of Scorpius' head and claws, and include the bright star Antares.

Above and right of Antares is an even brighter planet Jupiter. Numerous red emission nebulas and blue reflection nebulas are visible throughout the image. Scorpius appears prominently in southern skies after sunset during the middle of the year.

Friday, October 19, 2007

ESA's Candidate Missions

Credits: Khosroshahi, Maughan, Ponman, Jones, ESA, ING.

XMM-Newton observations of the fossil galaxy cluster RX J1416.5+2315, show a cloud of hot gas emitting X-rays (in blue). The cloud, reaching temperatures of about 50 million degrees, extend over 3.5 million light years and surround a giant elliptical galaxy believed to have grown to its present size by cannibalising its neighbours.

XEUS, X-ray Evolving Universe Spectroscopy
XEUS is a next-generation X-ray space observatory to study the fundamental laws of the Universe and the origins of the universe. With unprecedented sensitivity to the hot, million-degree universe, XEUS would explore key areas of contemporary astrophysics: growth of supermassive black holes, cosmic feedback and galaxy evolution, evolution of large-scale structures, extreme gravity and matter under extreme conditions, the dynamical evolution of cosmic plasmas and cosmic chemistry. XEUS would be stationed in a halo orbit at L2, the second Lagrange point, with two satellites (one mirror satellite and the other a detector satellite) that would fly in formation.

ESA announces candidate missions for 2015-2025 Cosmic Vision
Including space walking, spacecraft docking and the setting up of a space laboratory before 2010, China is also planning to land a human on the moon and to make a series of robotic missions with a view to building a base there after 2020.
China reveals space plans from Space Daily
NASA terminates Kistler Rocketplane contract from Cosmic Log
ESA's Integral Project ends its five year journey from Goldenship9

Wednesday, October 17, 2007

Extreme Stellar Black Hole

Credit: NASA/CXC/M. Weiss

An artist's representation of M33 X-7: a binary system in the nearby galaxy M33, containing a massive blue star feeding material to a black hole surrounded by a small accretion disk.

Stellar black holes form when stars with masses around 20 times that of the sun collapse under the weight of their own gravity at the ends of their lives. Most stellar black holes weigh in at around 10 solar masses when the smoke blows away.

The black hole in M33 X-7 located 2.7 million light-years from Earth, is also the most distant stellar black hole ever observed.

The findings, detailed in the Oct. 17 issue of the journal Nature, could help improve formation models of "binary" systems containing a black hole and a star. It could also help explain one of the brightest star explosions ever observed.

The blackhole orbits a companion star in the spiral galaxy Messier 33. The companion star of M33 X-7 passes directly in front of the black hole as seen from Earth once every three days, completely eclipsing its X-ray emissions. It is the only known binary system in which this occurs, and it was this unusual arrangement that allowed astronomers to calculate the pair's masses very precisely.

The tight orbits of the black hole and star suggests the system underwent a violent stage of star evolution called the common-envelope phase, in which a dying star swells so much it sucks the companion inside its gas envelope.

The result is either a merger between the two stars or the formation of a tight binary in which one star is stripped of its outer layers. The latter scenario may be what happens in the case of M33 X-7, and the stripped star explodes as a supernova before imploding to form a black hole.

However, something unusual must have happened to M33 X-7 during this phase to create such a massive black hole. The black hole must have lost a large amount of mass for the two objects to be so close, but on the other hand, it must have retained enough mass to form such a heavy black hole.

M33 X-7 might thus provide both the upper and lower limits on the amount of mass loss and orbital tightening that can occur in the common envelope.

While the estimated 16 solar masses of the black hole in M33 X-7 is hefty for a stellar black hole, it is miniscule compared with the black holes thought to lie in the heart of many large galaxies.

Such "supermassive" black holes have masses millions to billions times that of our sun, but they are thought to form by mechanisms different from the stellar variety.

M33 X-7: Heaviest Stellar Black Hole Discovered in Nearby Galaxy from Chandra
The fantastic skies of Orphan Stars from NASA Science
Hubble finds Youthful-looking galaxy conceals ancient stars

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Tuesday, October 16, 2007

The Universe Is All History

It took 300 years of experiment and calculation to pin down the speed at which light travels in a vacuum: 186,282 miles per second.

Light will travel slightly slower than this through air, and some wild experiments have actually slowed light to a crawl and seemingly made it go backward, but at the scales encountered in our everyday lives, light is so fast that we perceive our surroundings in real time.

Look up into the night sky and this illusion begins to falter. Because light takes time to get here from there, the farther away 'there' is the further in the past light left there and so we see all objects at some time in the past.

We see the relatively close moon as it was 1.2 seconds ago and the more distant sun as it was about 8 minutes ago. The measurements — 1.2 light-seconds and 8 light-minutes — can be thought to describe both time and distance.

The distance to more remote objects such as other stars is so great it is measured in light-years—the distance light will travel in a year, or about 6 trillion miles (10 trillion kilometers). Even the nearest star system, Proxima Centauri, lies more than four light-years away, so it appears to us on Earth as it was just over four years ago when the light began its journey.
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In this way, light's finite speed gives us a valuable view into the past, and as we strain our gaze deeper into the universe we look further back in time. In the case of distant galaxies, we see them as they were billions of years ago when the universe was relatively young.

Glittering star cluster is galactic heavyweight This cluster of thousands of stars lies 20,000 light years from Earth in the Carina spiral arm of our galaxy. It is embedded in a star-forming nebula called NGC 3603, a cloud of gas and dust with enough material to form 400,000 stars like the Sun. Most of the bright stars in the image are very hot and massive. Their radiation and stellar winds have blown out a large cavity in the nebula around them.

Some galaxies are so remote that their light hasn't had sufficient time to reach us yet, despite about 13.7 billion years of travel.

There could also be more distant objects that will forever remain unknown to us. Because the universe may be expanding and the expansion appears to be accelerating, there may be distant galaxies which if we can't see them now because their light has not had time to reach us, we will never see.

So we can never see the universe as it is, only as it was at various stages of its development. To interact with remote parts of the universe — to see them as they are now — would require some exotic means of travel, such as to travel faster than light which, according to Einstein's special theory of relativity, is impossible as it would require an infinite amount of energy.

The fantastic skies of Orphan Stars from NASA Science
Hubble finds Youthful-looking galaxy conceals ancient stars

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Monday, October 15, 2007

Future Space Craft

The risks from radiation in space, and the need to keep the crew safe on long flights, may influence the shape of future spaceships.

The major radiation sources are galactic cosmic rays, charged particles: from electrons up to the heavy metal elements and 'solar particle events', which throw out protons and helium nuclei.

Exposure from the hazards of severe space radiation in long-duration deep space missions is 'the show stopper'. Protection from the hazards of severe space radiation is of paramount importance to NASA's new vision to reach the Moon, Mars and beyond.

The electrons, protons & heavy-metal ions such as iron and uranium whiz through the void and can all cause cancers. But aluminium shielding capable of staving the radiation off on extended journeys would be prohibitively heavy, burning too much fuel.

The ideal form, according to Ram Tripathi, a spaceflight engineer at NASA, is a grapefruit spiked with cherries on sticks. With positively and negatively charged metal spheres be arranged on struts jutting out of the crew capsule, in carefully controlled directions, to give the crew a high degree of electrostatic radiation cover.

Tripathi calculates the "cherries" would need to be between 10 and 20 metres in diameter and would be stationed about 50 metres from the crew capsule – the "grapefruit". These spheres would protect the crew by deflecting charged particles away from the central habitat. Spheres give you more volume and less mass, and evenly distribute the deflecting charges over their surface.

The charged spheres would be made of lightweight hollow aluminium, the material shielding the crew capsule would incorporate carbon nanotubes – in a novel composite with aluminium. The nanotubes are light, they can take a pounding from heavy incoming ions.

Or we could have spaceships with a more conventional shape like a submarine, the starship enterprise, the space shuttle or nerva, with a false skin filled with smaller spheres (or even tubes) having the same desired effect, deflecting radiation and adding volume, without overwhelmingly increasing the mass.

Laser power stations, drawing energy from the local environment, might one day propel spacecraft throughout the solar system. NASA studies of advanced planetary missions have ranged from small robotic probes to multiple-spacecraft human exploration missions.
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The completed International Space Station will have a mass of about 1,040,000 pounds. It will measure 356 feet across and 290 feet in length, with almost an acre of solar panels to provide electrical power to six laboratories.

The assembled space station will provide the first laboratory complex where gravity, a fundamental force on Earth, can be controlled for extended periods. This control of gravity opens up an unimaginable world where almost everything grows differently than on Earth. For example, purer protein crystals can be grown in space than on Earth. By analyzing crystals grown on the ISS, scientists may be able to develop medicines that target particular disease-causing proteins.

Such crystals for research into cancer, diabetes, emphysema and immune disorders grown on the space station have already shown promise. New drugs to fight influenza and post-surgery inflammation are already in clinical trials, and future research will benefit from the extended exposure to weightlessness available on the station.

Many of the changes in the human body that result from space flight mimic those seen on Earth as a result of aging. Understanding of the causes of these changes may lead to the development of countermeasures against bone loss, muscle atrophy, balance disorders and other symptoms common in an aging population.

The Johnson Space Centre, together with scientists and researchers at NASA's other field centers, is working on the technologies that will be required for further exploration of the universe in the next years. For example, a new rocket team at Marshall is developing revolutionary technologies that will make space transportation as safe, reliable and affordable as today's airline transportation.

Hospitals, business parks and solar electric power stations that beam clean, inexpensive energy back to Earth are likely to dot the "space-scape" 40 years from now. Space adventure tourism and travel, orbiting movie studios, and worldwide, two-hour express package delivery also appear just over the horizon.

By 2040, it's expected to cost only tens of dollars per pound to launch humans or cargo to space; today, it costs as much as $10,000 per pound. Bridging that gap requires intense research and technology development focused on accelerating breakthroughs that will serve as keys to open the space frontier for business and pleasure.

Space transportation technology breakthroughs will launch a new age of space exploration, just as the silicon chip revolutionized the computer industry and made desktop computers commonplace.

The New Space Race by Brian Appleyard @ The Sunday Times
The first Sino-European Satellite completes four year mission ESA
The Johnson Space Centre Celebrates 40 Years of Human Space Flight

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Saturday, October 13, 2007

Solar Power from Space

Illustration: Mafic Studios

A report released by the National Security Space Office recommends that the US government sponsor projects to demonstrate solar-power-generating satellites and provide financial incentives for further private development of the technology.

Space-based solar power would use kilometre-sized solar panel arrays to gather sunlight in orbit. It would then beam power down to Earth in the form of microwaves or a laser, which would be collected in antennas on the ground and then converted to electricity. Unlike solar panels based on the ground, satellites placed in geostationary orbit above the Earth can operate at night and during cloudy conditions.

The NSSO report (pdf) recommends that the US government spend $10 billion over the next 10 years to build a test satellite capable of beaming 10 megawatts of electric power down to Earth.
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At the same press conference, over a dozen space advocacy groups announced a new alliance to promote space solar power – the Space Solar Alliance for Future Energy. These supporters of space-based solar power say the technology has the potential to provide more energy than fossil fuels, wind and nuclear power combined.

The NSSO report says that solar-power-generating satellites could also solve supply problems in distant places such as Iraq, where fuel is currently trucked along in dangerous convoys and the cost of electricity for some bases can exceed $1 per kilowatt-hour. The report also touts the technology's potential to provide a clean, abundant energy source and reduce global competition for oil.

The US abandoned the idea as economically unfeasible in the 1970s. Advances in photovoltaics, electronics and robotics will bring the size and cost down to a fraction of the original schemes, and eliminate the need for humans to assemble the equipment in space.

Several technical challenges remain to be overcome, including the development of lower-cost space launches. A satellite capable of supplying the same amount of electric power as a modern fossil-fuel plant would have a mass of about 3000 tonnes – more than 10 times that of the International Space Station. Sending that material into orbit would require more than a hundred rocket launches. The US currently launches fewer than 15 rockets each year.

In spite of these challenges, the NSSO say no fundamental scientific breakthroughs are necessary to proceed with the idea and that space-based solar power will be practical in the next few decades.

Beaming Power from Space by Astroprof @ Astroprof's Page
Harnessing The Sun interview with Feng Hsu @ Scientic Blogging
Internet 2 Speeds Jump 10-fold -To Debut at CERN - The Daily Galaxy

Friday, October 12, 2007

The Dandelion Universe

So we don't all live on a yellow submarine.
We live in a universe which rapidly inflated from a 'nothingness' and expanded into the universe we observe today, a place filled with the visible matter and a lot of dark matter (and dark energy) contained within the cosmic event horizon.

And though for a while we may have thought the expansion of the universe was contained by gravity and/or a sort of surface tension of the outer rim (skin) or cosmic event horizon, it now seems that the universe may still be expanding and even accelerating - perhaps taking the shape of the spiral galaxies we observe, including our own home the Milky Way

And yes it is possible that anything on the outer limits may accelerate and reach the speed of light, or even fall outside (escape) the cosmic event horizon. Of course this may already have happened to some of the original universe. We would be unable to tell, since we cannot see beyond the event horizon.

These things occur on a cosmological time-scale, so it is not easy for us to see in a human life-time. In the mean time we amuse ourselves trying to speculate, theorize and debate what may have occurred billions of years ago, and what may be the consequences now & today billions of light years away.
Testing Einstein: Is Dark Energy Constant? - CfA Press Release
Major Step Toward Knowing Origin of Cosmic Rays - from NASA
Stellar Explosion Outshines Sun 100 Billion Times @ Live Science
Orion Measurements Change Stellar Distances - Centauri Dreams

Thursday, October 11, 2007

Nuclear Space Travel

Image Credit: Project Orion

Compared with the best chemical rockets, nuclear propulsion systems (NPS's) are more reliable and flexible for long-distance missions, and can achieve a desired space mission at a lower cost. The reason for these advantages in a nutshell is that NPS's can get "more miles per gallon" than chemical rockets.

For any space mission, basic questions must be answered:

1 - What is the destination?
2 - What is the trip time?
3 - Do we want to return?
4 - the mass of the payload we want to send there & bring back?

In chemical rocket engines such as the Space Shuttle Main Engine (SSME), the chemical reaction between the hydrogen and oxygen releases heat which raises the combustion gases (steam and excess hydrogen gas) up to high temperatures (3000-4000 K). These hot gases are then accelerated through a thermodynamic nozzle, which converts thermal energy into kinetic energy, and hence provides thrust. The propellant and the heat source are one in the same.
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Because there is a limited energy release in chemical reactions and because a thermodynamic nozzle is being used to accelerate the combustion gases that do not have the minimum possible molecular weight, there is a limit on the exhaust velocity that can be achieved.

The maximum specific impulse Isp that can be achieved with chemical engines is in the range of 400 to 500 s. So, for example, if we have an Isp of 450 s, and a mission delta-V of 10 km/s (typical for launching into low earth orbit (LEO)), then the mass ratio will be 9.63. The problem here is that most of the vehicle mass is propellant, and due to limitations of the strength of materials, it may be impossible to build such a vehicle, just to ascend into orbit.

Early rocket scientists got around this problem by building a rocket in stages, throwing away the structural mass of the lower stages once the propellant was consumed. This effectively allowed higher mass ratios to be achieved, and hence a space mission could be achieved with low-Isp engines. This is what all rockets do today, even the Space Shuttle. In spite of the relatively low Isp, chemical engines do have a relatively high thrust-to-weight ratio (T/W).

A high T/W (50-75) is necessary for a rocket vehicle to overcome the force of gravity on Earth and accelerate into space. The thrust of the rocket engines must compensate for the weight of the rocket engines, the propellant, the structural mass, and the payload. Although it is not always necessary, a high T/W engine will allow orbital and interplanetary space vehicles to accelerate quickly and reach their destinations in shorter time periods.

Nuclear propulsion systems have the ability to overcome the Isp limitations of chemical rockets because the source of energy and the propellant are independent of each other. The energy comes from a critical nuclear reactor in which neutrons split fissile isotopes, such as 92-U-235 (Uranium) or 94-Pu-239 (Plutonium), and release energetic fission products, gamma rays, and enough extra neutrons to keep the reactor operating.

The energy density of nuclear fuel is enormous. The heat energy released from the reactor can then be used to heat up a low-molecular weight propellant (such as hydrogen) and then accelerate it through a thermodynamic nozzle in same way that chemical rockets do. This is how nuclear thermal rockets (NTR's) work.

Solid-core NTR's (See Figure 2) have a solid reactor core with cooling channels through which the propellant is heated up to high temperatures (2500-3000 K). Although solid NTR's don't operate at temperatures as high as some chemical engines (due to material limitations), they can use pure hydrogen propellant which allows higher Isp's to be achieved (up to 1000 s).

In gas-core NTR's, the nuclear fuel is in gaseous form and is inter-mixed with the hydrogen propellant. Gas core nuclear rockets (GCNR) can operate at much higher temperatures (5000 - 20000 K), and thus achieve much higher Isp's (up to 6000 s).

Of course, there is a problem in that some radioactive fission products will end up in the exhaust, but other concepts such as the nuclear light bulb (NLB) can contain the uranium plasma within a fused silica vessel that easily transfers heat to a surrounding blanket of propellant. At such high temperatures, whether an open-cycle GCNR, or a closed-cycle NLB, the propellants will dissociate and become partially ionized.

In this situation, a standard thermodynamic nozzle must be replaced by a magnetic nozzle which uses magnetic fields to insulate the solid wall from the partially-ionized gaseous exhaust.

NTR's give a significant performance improvement over chemical engines, and are desirable for interplanetary missions. It may also be possible that solid core NTR's could be used in a future launch vehicle to supplement or replace chemical engines altogether4. Advances in metallurgy and material science would be required to improve the durability and T/W ratio of NTR's for launch vehicle applications.

An alternative approach to NTR's is to use the heat from nuclear reactor to generate electrical power through a converter, and then use the electrical power to operate various types of electrical thrusters (ion, hall-type, or magneto-plasma-dynamic (MPD)) that operate on a wide variety of propellants (hydrogen, hydrazine, ammonia, argon, xenon, fullerenes) This is how nuclear-electric propulsion (NEP) systems work.

To convert the reactor heat into electricity, thermoelectric or thermionic devices could be used, but these have low efficiencies and low power to weight ratios. The alternative is to use a thermodynamic cycle with either a liquid metal (sodium, potassium), or a gaseous (helium) working fluid. These thermodynamic cycles can achieve higher efficiencies and power to weight ratios.

No matter what type of power converter is used, a heat rejection system is needed, meaning that simple radiators, heat pipes, or liquid-droplet radiators would be required to get rid of the waste heat. Unlike ground-based reactors, space reactors cannot dump the waste heat into a lake or into the air with cooling towers.

The electricity from the space nuclear reactor can be used to operate a variety of thrusters. Ion thrusters use electric fields to accelerate ions to high velocities. In principle, the only limit on the Isp that can be achieved with ion thrusters is the operating voltage and the power supply. Hall thrusters use a combination of magnetic fields to ionize the propellant gas and create a net axial electric field which accelerates ions in the thrust direction. MPD thrusters use either steady-state or pulsed electromagnetic fields to accelerate plasma (a mixture of ions and electrons) in the thrust direction. To get a high thrust density, ion thrusters typically use xenon, while Hall thrusters and MPD thrusters can operate quite well with argon or hydrogen.

Compared with NTR's, NEP systems can achieve much higher Isp's. Their main problem is that they have a low power to weight ratio, a low thrust density, and hence a very low T/W ratio. This is due to the mass of the reactor, the heat rejection system, and the low-pressure operating regime of electrical thrusters.

This makes NEP systems unfeasible for launch vehicle applications and mission scenarios where high accelerations are required; however, they can operate successfully in low-gravity environments such as LEO and interplanetary space.

In contrast to a chemical rocket or an NTR which may operate only for several minutes to less than an hour at a time, an NEP system might operate continuously for days, weeks, perhaps even months, as the space vehicle slowly accelerates to meet its mission delta-V. An NEP system is well suited for unmanned cargo missions between the Earth, Moon and other planets.

For manned missions to the outer planets, there would be a close competition between gas-core NTR's and high-thrust NEP systems.

The performance gain of nuclear propulsion systems over chemical propulsion systems is overwhelming. Nuclear systems can achieve space missions at a significantly lower cost due to the reduction in propellant requirements.

When humanity gains the will to explore and develop space more ambitiously, nuclear propulsion will be an attractive choice.

Source: Nuclear Propulsion from Astro Digital.

Innovative Nuclear Space Power and Propulsion Institute University of Florida
Kazakhstan Wants Russia To Pay 60 Million $US In Damages For Proton Crash
The Next Space Age by Alan Boyle @ Cosmic Log

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Wednesday, October 10, 2007

Swarm of Mirrors

Illustration: M Vasile et al, University of Glasgow

Focusing sunlight onto an asteroid with space-based mirrors is the best way to deflect Earth-bound space rocks, a new study finds. The mirrors beat out nuclear blasts and "gravity tractors" in the study, which compared nine different deflection methods.

The spacecraft would be launched from Earth to hover near the asteroid and concentrate sunlight onto a point on the asteroid's surface. In this way, they would heat the asteroid's surface to more than 2100° C, enough to start vaporising it. As the gases spewed from the asteroid, they would create a small thrust in the opposite direction, altering the asteroid's orbit.

The scientists found that 10 of these spacecraft, each bearing a 20-metre-wide inflatable mirror, could deflect a 150-metre asteroid in about six months. With 100 spacecraft, it would take just a few days, once the spacecraft are in position.

To deflect a 20-kilometre asteroid, about the size of the one that wiped out the dinosaurs, it would take the combined work of 5000 mirror spacecraft focusing sunlight on the asteroid for three or more years. Launching and controlling 5000 spacecraft is a daunting prospect, but launching a few dozen spacecraft to deflect a smaller asteroid is within our capabilities.

Read more Are mirrors the best way to deflect asteroids

Tuesday, October 09, 2007

Quasars & Cosmic Gems

Star Ruby - Credit: treasuremountainmining

A new study finds vast amounts of gemstones and dusts could be created in the outer regions of supermassive blackholes. Rubies and sapphires could be produced in chaotic environments around some supermassive black holes known as quasars, just like an enormous jewel factories in the sky.

The breakdown of these materials into simpler components may account for much of the space dust in the universe. Dust that is recycled to make stars, planets, and life.

Traces of these minerals, as well as sand and marble, were recently found by scientists analyzing light from the region around a nearby supermassive black hole using NASA's Spitzer Space Telescope. The black hole was embedded in a quasar, a highly active and incredibly bright galaxy under construction.

"We were surprised to find what appears to be freshly made dust entrained in the winds that blow away from supermassive black holes," said study team member Ciska Markwick-Kemper of the University of Manchester in the U.K.

Image Credit: NASA/JPL-Caltech
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The finding, to be detailed in an upcoming issue of Astrophysical Journal, could also help solve the mystery of where dust used to build the first generation of stars in the universe came from.
The space dust in our corner of the universe is thought to have been created when ancient stars resembling massive versions of our sun exploded as supernovas at the ends of their lives. But when the universe was new, sun-like stars hadn't been around long enough to die and make dust. So where did the dust needed to make those stars come from?

One idea is that the dust came from quasars, which are supermassive black holes surrounded by dusty, doughnut-shaped clouds and lots of radiation. They are the most active, budding galaxies known, where gravity lures material in but the resulting pressure blows material away on a constant cosmic tug-of-war that results in high rates of star formation and the creation of new elements.

"Quasars can consume less matter than they can spit out in the form of winds" said study team member Sarah Gallagher of the University of California, Los Angeles.

To test this theory, Gallagher and her team used Spitzer to investigate PG2112+059, a quasar located in the center of a galaxy about 8 billion light-years away. They found evidence of sand and minerals such as rubies that do not last long in the harsh environment of space, suggesting they were freshly made.

The researchers plan to look for evidence of dust around other quasars to strengthen their case. It's also possible, they say, that quasars were not the only source of dust in the early universe.

"Supernovas might have been more important for creating dust in some environments, while quasars were more important in others," Markwick-Kemper said.

Cosmic Factories Produce Rubies and Sapphires from LiveScience


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Monday, October 08, 2007

NGC 474's Shells

Galaxy NGC 474 - Credit & Copyright: Mischa Schirmer

The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years.

Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy to the right of NGC 474 is causing density waves to ripple though the galactic giant.

Whatever the possible cause, this image dramatically highlights the increasing consensus that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with - and accretions of - smaller nearby galaxies.

NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish Pisces.

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Friday, October 05, 2007

Einstein Ring

This photo illustration shows the foreground lensing source removed. The tiny reconstruceted galaxy 6 billion light-years away SDSS J0737+3216, is smaller than any galaxy ever seen at that distance.

Astronomers discovered this distant galaxy through a phenomenon called gravitational lensing. This phenomenon occurs when a massive galaxy in the foreground bends the light rays from a distant galaxy behind it in much the same way as a magnifying glass does. When both galaxies are exactly lined up, the light forms a bull's-eye pattern, called an "Einstein ring," around the foreground galaxy.

This ring can be seen in the hubblesite illustration. Einstein rings are named for physicist Albert Einstein, who predicted the phenomenon. By focusing the light rays, this gravitational lensing effect increases the observed brightness and size of the background galaxy by more than 10 times.

The illustration is based on images taken in infrared light from the W. M. Keck Telescope and visible-light images from NASA's Hubble Space Telescope. The Hubble and Keck data reveal information about the early years of the infant galaxy, namely that it is seen just after it formed most of its stars.

This galaxy is about half the size, and approximately one-tenth the "weight" of the smallest distant galaxies typically observed. Weighing only 1/100 as much as our Milky Way Galaxy, the dwarf is much smaller than anything studied before in any detail at this distance.

"Even though this galaxy is more than six billion light years away, the reconstructed image is as sharp as the ordinary ground-based images of the nearest structure of galaxies, the Virgo cluster, which is 100 times closer to us," said lead author Phil Marshall, a postdoctoral fellow at UCSB.
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"If the galaxy is representative of a larger population, it could be one of the building blocks of today's spiral galaxies, or a progenitor of modern dwarf galaxies," said Tommaso Treu from UC Santa Barbara. "It does look remarkably similar to the smallest galaxies in the Virgo cluster, but is almost half the way across the universe."

"We believe we may have identified the progenitors of local dwarf galaxies," says Tommaso Treu. "We see them as clearly as we would see dwarfs in the Virgo cluster using ground-based telescopes."

The mass estimate for the galaxy, and the inference that many of its stars have only recently formed, is made possible by the combination of optical and near infrared images from the Hubble Space Telescope with longer wavelength images obtained with the Keck Telescope.

The sharp view of NASA's Hubble Space Telescope, and the laser guide stars adaptive optics system on the W.M. Keck Telescope, were aimed at a natural lens in space, called a gravitational lens, to study the dwarf.

Adaptive optics systems use bright stars in the field of view to measure the Earth's atmospheric blurring and correct for it in real time. This technique relies on having a bright star in the image as well, so it is limited to a small fraction of the night sky.

The Keck Telescope uses a powerful laser to illuminate the layer of sodium atoms that exist in the Earth's atmosphere, explained Jason Melbourne, a team member from the Center for Adaptive Optics at the University of California, Santa Cruz.

The laser image acts as an artificial star, bright enough to perform adaptive optics correction at an arbitrary position in the sky, thus enabling much sharper imaging over most of the sky.

Scientists 'Weigh' Tiny Galaxy Halfway Across Universe UCSB Press Release
Seeing the Universe with Einstein's glasses from Space dotcom

New Image of the Central Region of the Active Galaxy M87
Fifty Times sharper than Hubble from the Max Planck Institute

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Wednesday, October 03, 2007

Invisible Dark Matter

Photo by Chandra X-ray telescope team.

The Dark Matter Of The Universe Has A Long Lifetime

The two clusters of galaxies, called Bullet Cluster, are in the process of moving through each other. The red curves show gravitational measurements of the combined mass that consists of partly the visible matter of the galaxies and partly the invisible dark matter.

X-ray measurements of the two clusters of galaxies show that the clouds of gas have been pushed out at the collision between the two clusters of galaxies. In the cluster of galaxies to the right there is a lot of dark matter, but very little x-ray, so the dark matter decays very slowly and thus has a very, very long lifetime.

The universe consists not just of visible celestial bodies, stars, planets and galaxies. It also has a mystical fellow player - dark matter. New research from the Niels Bohr Institute presents new information that adds another piece of knowledge to the jigsaw puzzle of the dark mystery of the universe - dark matter.

The research has just been published in the Physical Review Letters: Searching for Decaying Axionlike Dark Matter from Clusters of Galaxies

Astronomers can measure that dark matter exists in big quantities but no one knows what it is, nobody has seen it. It does not emit light and it does not reflect light. It is invisible. It is a mystery and the researchers have many theories.

The dark matter has caused the researchers headaches for decades since it was detected in the 1970s, and there is intense research into the phenomena. It is invisible but it has got mass, and thus it has got gravitation that can be measured.

By analysing the galaxies it is possible to weigh them, and it turns out that by far the greatest matter of the collective mass of the galaxy is dark matter.

Just like stars get together in galaxies, the galaxies get together in clusters of galaxies of up to several thousand galaxies. Signe Riemer-Sorensen, astrophysicist at the Niels Bohr Institute, has analysed two clusters of galaxies that collide.
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When the two clusters of galaxies meet neither the galaxies nor the dark matter collide. However, about 12 per cent of the mass of the cluster of galaxies consists of huge clouds of gas and dust and these clouds collide.

The gas clouds are hot and emit x-ray that can be observed, and it is possible to see how the clouds are actually pushed out of the two clusters of galaxies at the collision. When the clouds of gas collide they become even hotter and emit more x-ray so that a whole shock front of warn gas is generated.

Observations indicate that the dark matter can be a new and still undetected type of particle. Among the suggestions for the dark matter, are particles that when they decay they emit x-ray.

One is the so called axions that are particles which is explained in theories with extra dimensions. So to be able to look for x-ray from dark matter the researchers are looking in places where there is a big concentration of dark matter, but no gas.

Such places are found in the two colliding clusters of galaxies where the gas clouds have been pushed out at the collision. Sorensen has analysed the one of the two clusters of galaxies that are in the process of colliding.

The analyses show that it is a very heavy cluster with many galaxies, and measurement of the gravitation show that there is a very big amount of dark matter, up to 85 per cent of the collective mass. However, no x-ray of any consequence was measured.

When the dark matter does not emit significant x-ray it is possible to calculate an upper limit to how quickly the particles decay and thus calculate their lifetime.

The result is that if axions are to be the dark matter they must have a life span that is longer that 3.000.000 billion years. In that case there is not very much dark matter that has decayed yet if it was formed 13.7 billion years ago. The conclusion is that dark matter has a very, very long lifetime.


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Tuesday, October 02, 2007

Stellar Jewel Box

Star Cluster Bursts into Life in New Hubble Image. Click Image to Enlarge

Thousands of sparkling young stars are nestled within the giant nebula NGC 3603. This stellar "jewel box" is one of the most massive young star clusters in the Milky Way Galaxy.

NGC 3603 is a prominent star-forming region in the Carina spiral arm of the Milky Way, about 20,000 light-years away. This latest image from NASA's Hubble Space Telescope shows a young star cluster surrounded by a vast region of dust and gas. The image reveals stages in the life cycle of stars.

The nebula was first discovered by Sir John Herschel in 1834.
Extreme star cluster in new Hubble images ESA Zoom-in animation.

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Monday, October 01, 2007

Beta Pictoris

NASA's Hubble Space Telescope revealed two dust disks circling the nearby star Beta Pictoris. The images confirm a decade of scientific speculation that a warp in the young star's dust disk may actually be a second inclined disk, which is evidence for the possibility of a planet that is at least as big as Neptune. Credit: NASA

Puffy debris disks around three nearby stars could harbour Pluto-sized planets-to-be, a new computer model suggests.

The "planet embryos" are predicted to orbit three young, nearby stars, located within about 60 light years or less of our solar system. Beta Pictoris & AU Microscopii are both about 12 million years old, while a third star, Fomalhaut, is aged at 200 million years old.

If confirmed, the objects would represent the first evidence of a never-before-observed stage of early planet formation. Another team recently spotted "space lint" around a nearby star that pointed to an even earlier phase of planet building, when baseball-sized clumps of interstellar dust grains are colliding together.

The thickness of a dust ring or debris disk depends on the size of objects orbiting inside it. The ring of dust thins as the star system ages, but if enough dust has clumped together to form an embryonic planet, it knocks the other dust grains into eccentric orbits. Over time, this can puff up what was a razor-thin disk.

The new finding will be detailed in an upcoming issue of the Monthly Notices of the Royal Astronomical Society.
Solar Storm rips tail of Comet - from NASA. See short movie
Circumstellar Debris Disks resemble our Kuiper Belt from Hubble
Dawn's early light, Ceres & Vesta by Amara @ Scientific Blogging

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