Friday, December 28, 2007

Pulsed Heartbeat Star

XMM-Newton has detected periodic X-ray emission, or the pulsed heartbeat of a new type of star. Collecting the X-rays from the so-called rotating radio transient has confirmed the nature of the underlying celestial object and given astronomers a new insight into these exotic objects. The observations were made using XMM-Newton's European Photon Imaging Camera (EPIC), which targeted the celestial object RRAT J1819-1458. Astronomers observed the object for around 12 hours and detected pulsations in the X-ray data that show the source to be rotating once every 4.26 seconds.

Previously, astronomers had only seen radio outbursts from this object. It erupts every three minutes or so with a brief burst of radio emission lasting just 3 milliseconds. Such behaviour defines the object as a rotating radio transient.
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The RRATs were announced in February 2006. Eleven objects were found using the Parkes radio telescope. Astronomers suspected that RRATs were neutron stars, the compact remnants of dead stars made of neutrons and measuring just 10-12 km across yet containing more matter than the Sun. They are therefore extremely dense. Most observed neutron stars are radio pulsars; rotating quickly and sweeping lighthouse beams of radiation across space that make them appear to pulsate. The RRATs, however, were only detected through their radio bursts.

The new XMM-Newton observations show that periodic emission, linked to the object's rotation, can be detected in X-rays. "It is now definite that RRATs are rotating neutron stars as we can see the 4.26-second rotation period of the RRAT in the X-ray data," says Maura McLaughlin, West Virginia University, USA, who took the lead in the research.

In addition to the identification of the underlying celestial object from the discovery of the X-ray pulsations, XMM-Newton also revealed another facet of the RRAT's behaviour. Something appears to be absorbing certain frequencies of the X-rays after they are emitted from the surface of the neutron star.

The absorption could either be happening in an atmosphere of gases surrounding the neutron star or by particles trapped in the neutron star's magnetic field. If the second reason is the cause of the absorption, it would indicate that the magnetic field of this RRAT is strong. "We can't say for sure where the absorption is coming from with these observations," says Nanda Rea, University of Amsterdam, Netherlands. She estimates that an observation twice as long would collect enough data to determine where the absorption is taking place.

She also hopes to follow-up this observation by targeting other RRATs. Before that can happen, however, the team must refine the positions they have for these objects. To do this, they continue to observe the RRATs with radio telescopes across the world, timing the outbursts. From careful measurements of the arrival times of the bursts over the course of the year, their positions in the sky can be determined more accurately. Once these locations are known, X-ray telescopes can be pointed in their direction.

Since the original discovery of 11 RRATs, McLaughlin's team has found an additional 10. This indicates that they may form a substantial population in the Milky Way, with over 100,000 of them dotted around our galaxy.


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Sunday, December 23, 2007

The Cosmic Bird

Credit: ESO Press Photo 54a/07

Using ESO's Very Large Telescope, an international team of astronomers has discovered a stunning rare case of a triple merger of galaxies. This system, which astronomers have dubbed 'The Bird' - composed of two massive spiral galaxies and a third irregular galaxy.

The galaxy ESO 593-IG 008, or IRAS 19115-2124, was previously merely known as an interacting pair of galaxies at a distance of 650 million light-years. But surprises were revealed by observations made with the NACO instrument attached to ESO's VLT, which peered through the all-pervasive dust clouds, using adaptive optics to resolve the finest details.

Underneath the chaotic appearance of the optical Hubble images - retrieved from the Hubble Space Telescope archive - the NACO images show two unmistakable galaxies, one a barred spiral while the other is more irregular.

The surprise lay in the clear identification of a third, clearly separate component, an irregular, yet fairly massive galaxy that seems to be forming stars at a frantic rate.

Because of the resemblance of the system to a bird, the object was dubbed as such, with the 'head' being the third component, and the 'heart' and 'body' making the two major galaxy nuclei in-between of tidal tails, the 'wings'. The latter extend more than 100,000 light-years, or the size of our own Milky Way.

Subsequent optical spectroscopy with the new Southern African Large Telescope, and archive mid-infrared data from the NASA Spitzer space observatory, confirmed the separate nature of the 'head', but also added further surprises. The 'head' and major parts of the 'Bird' are moving apart at more than 400 km/s (1.4 million km/h!). Observing such high velocities is very rare in merging galaxies. Also, the 'head' appears to be the major source of infrared luminosity in the system, though it is the smallest of the three galaxies.

The 'head' is forming stars violently, at a rate of nearly 200 solar masses per year, while the other two galaxies appear to be at a more quiescent epoch of their interaction-induced star formation history.

The 'Bird' belongs to the family of luminous infrared galaxies, with an infrared luminosity nearly one thousand billion times that of the Sun. This family of galaxies has long been thought to signpost important events in galaxy evolution, such as mergers of galaxies, which in turn trigger bursts of star formation, and may eventually lead to the formation of a single elliptical galaxy.
Is it all an illusion or light from a beam
Reality is relative, and always supreme
though for a moment it may not so seem
May the new year fulfill your every dream

Hubblesite presents - Striking Galaxy Encounters


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Thursday, December 20, 2007

Merry Xmas to You All

Early stages of Solar System & Planet formation
When the Solar System Went from Dust to Mountains
Galaxy Has 1,000 Times Our Rate of Star Formation
Supernova Generates Enough Dust for 10,000 Earths from Universe Today

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Monday, December 17, 2007

Death Star Galaxy

Credit: NASA, ESA, and D. Evans (Harvard-Smithsonian Center for Astrophysics)

A powerful jet from a supermassive black hole is blasting a nearby galaxy, according to new data from NASA observatories. This never-before witnessed galactic violence may have a profound effect on planets in the jet's path and trigger a burst of star formation in its destructive wake.

Known as 3C 321, the system contains two galaxies in orbit around each other. Data from NASA's Chandra X-ray Observatory show both galaxies contain supermassive black holes at their centers, but the larger galaxy has a jet emanating from the vicinity of its black hole. The smaller galaxy apparently has swung into the path of this jet.

This "death star galaxy" was discovered through the combined efforts of both space and ground-based telescopes. NASA's Chandra X-ray Observatory, Hubble Space Telescope, and Spitzer Space Telescope were part of the effort. The Very Large Array (VLA) in Socorro, N.M., and the Multi-Element Radio Linked Interferometer Network (MERLIN) telescopes in the United Kingdom also were needed for the finding.

Jets from supermassive black holes produce high amounts of radiation, especially high-energy X-rays and gamma-rays, which can be lethal in large quantities. The combined effects of this radiation and particles traveling at almost the speed of light could severely damage the atmospheres of planets lying in the path of the jet. For example, protective layers of ozone in the upper atmosphere of planets could be destroyed.

Jets produced by supermassive black holes transport enormous amounts of energy far from the black holes and enable them to affect matter on scales vastly larger than the size of the black hole. Learning more about jets is a key goal for astrophysical research.

The effect of the jet on the companion galaxy is likely to be substantial, because the galaxies in 3C 321 are extremely close at a distance of only about 20,000 light-years apart, approximately the same distance as Earth is from the center of the Milky Way galaxy.

A bright spot in the VLA and MERLIN images shows where the jet has struck the side of the galaxy, dissipating some of the jet's energy. The collision disrupted and deflected the jet.

Another unique aspect of the discovery in 3C 321 is how relatively short-lived this event is on a cosmic time scale. Features seen in the VLA and Chandra images indicate that the jet began impacting the galaxy about one million years ago, a small fraction of the system's lifetime. This means that such an alignment is quite rare in the nearby universe, making 3C 321 an important opportunity to study such a phenomenon.

It is possible the event is not all bad news for the galaxy being struck by the jet. The massive influx of energy and radiation from the jet could induce the formation of large numbers of stars and planets after its initial wake of destruction is complete.

For more images and information about 3C 321, visit:

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Saturday, December 15, 2007

Mountains of Creation

Mountains of Creation

This fantastic skyscape lies at the eastern edge of giant stellar nursery W5, about 7,000 light-years away in the constellation Cassiopeia.

An infrared view from the Spitzer Space Telescope, it features interstellar clouds of cold gas and dust sculpted by winds and radiation from a hot, massive star just outside the picture (above and to the right).

Still swaddled within the cosmic clouds, newborn stars are revealed by Spitzer, their formation also triggered by the massive star. Fittingly dubbed "Mountains of Creation", these interstellar clouds are about 10 times the size of the analogous Pillars of Creation in M16, made famous in a 1995 Hubble Space Telescope view.

W5 is also known as IC 1848 and together with IC 1805 it is part of a complex region popularly dubbed the Heart and Soul Nebulae. The Spitzer image spans about 70 light-years.

Credit: Lori Allen (Harvard-Smithsonian CfA) et al., JPL-Caltech, NASA

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Wednesday, December 12, 2007

Celestial Magnetic Ropes

NASA satellites have uncovered giant 'magnetic ropes' linking the Earth's atmosphere to the Sun. These channel solar energy to create the spectacular northern and southern lights.

"The satellites have found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the Sun," said David Sibeck, project scientist at NASA's Goddard Space Flight centre in Maryland.

"We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras," he told the annual meeting of the American Geophysical Union in San Francisco.

Enormous burst of energy
The discovery is among a series of revelations made by the U.S. space agency's Time History of Events and Macroscale Interactions during Substorms mission (THEMIS) launched earlier this year.

A 'magnetic rope' is a twisted bundle of magnetic fields much like a rope made of hemp, and although previous spacecraft have seen glimpses of them, none had been able to map their structure. But the THEMIS's five identical micro-satellites could.

THEMIS encountered its first magnetic rope on May 20. It was very large, about as wide as Earth, and located approximately 65,000 km above Earth's surface in a region called the magnetopause.

This is the region where solar wind hurtles into the Earth's magnetic fields, and magnetic ropes are formed and unfurled in just a few minutes allowing solar wind to be briefly conducted along them.

This enormous burst of energy helps explain the phenomenon of aurora borealis (and its southern hemisphere equivalent, the aurora australis) also known as substorms, said Sibeck.

A substorm, which erupted over Alaska and Canada on March 23, provided a stunning show of auroras for more than two hours. They were photographed from below while satellites measured the particles and fields above, and showed a series of 10-minute outbursts.

Speedy substorms
The mission's principal investigator Vassilis Angelopoulos said the storm behaved very unexpectedly. "The auroras surged westward twice as fast as anyone thought possible, crossing 15 degrees of longitude in less than one minute… The storm traversed an entire polar time zone, or 400 miles, in 60 seconds flat."

The total energy required for such a two-hour show was about five hundred thousand billion Joules, or the equivalent of a 5.5 magnitude earthquake, Angelopoulos said.

The THEMIS mission also witnessed small explosions on the outskirts of the Earth's magnetic field in an area known as the bow shock.

"The bow shock is like the bow wave in front of a boat," said Sibeck. "It is where the solar wind first feels the effects of Earth's magnetic field. Sometimes a burst of electrical current within the solar wind will hit the bow shock and 'Bang!' we get an explosion."

THEMIS is a two-year mission being coordinated by the University of Berkeley in California, with several countries contributing.

Every four days the five THEMIS satellites line up along the Earth's magnetic field to follow disturbances in the magnetopause region. This allows the storms to be observed from five different angles simultaneously, helping scientists to learn about the origins of the storms and their evolutions.
Saturn Ringed by Electric Doughnut by Dave Mosher @ LiveScience
Part of Milky Way rotates in Opposite direction - from SPACEcom
Ultra High Energy Cosmic Rays by Charles Daney @ Science & Reason

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Saturday, December 08, 2007

A Million Light Years

An intergalactic particle beam stretching for more than a million light years is the longest ever seen. According to the team that discovered this record breaker, it could help reveal how such jets of matter bind themselves together.

Jets are seen all over the cosmos emerging out of many different types of object, including stars that are just beginning to form. The most powerful ones come from the cores of active galaxies, where gas falling towards a giant black hole generates a mixture of heat, high-energy particles and magnetic fields. In some cases, these elements combine to spit out narrow columns of hot gas laced with high-energy particles, which drill though the galaxy and on out into space.

The latest discovery emerges from a large elliptical galaxy called CGCG 049-033, which is about 600 million light years away. A team led by Joydeep Bagchi of Pune University in Maharashtra, India, noticed emission from this galaxy during a broad search for radio sources, and then took a closer look using the Giant Metrewave Radio Telescope near Pune and the 100-metre Effelsberg radio dish in Germany.

The jet they saw is nearly 1.5 million light years long, twice the length of the previous record holder. If this jet sprang instead from the centre of the Milky Way, it would loom over us like a skyscraper and would stretch halfway to the Andromeda galaxy.

It is unusual in other ways too. Jets usually come in fairly well-matched pairs, pointing in opposite directions. The new jet's counterpart, however, appears much shorter. That could be because the apparently shorter jet is pointing away from us - so light from its far end might not have had time to reach us yet.

Interestingly, the radio waves emitted by the newly discovered jet are strongly polarised, revealing a powerful magnetic field wrapped around the jet. "I was very surprised to find such a strong and regular magnetic field," said team member Marita Krause from the University of Bonn in Germany.

It may be that the magnetic field acts as a containing sheath, preventing the high-pressure gas in the jet from dispersing. That could explain why this jet is so long. A somewhat weaker version of this magnetic containment field might help hold jets together around other types of astronomical objects.

The team plans to get an even more detailed picture of the jet and its magnetic fields using the Very Large Array radio observatory in New Mexico, US.
The Evolution of Binary Stars from News Account @ Scientific Blogging
When Do Gas Giants Reach The Point Of No Return? from Science Daily
Odd Little Star Has Magnetic Personality from the Gemini Observatory

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Wednesday, December 05, 2007

White Dwarfs Get A Kick

NGC 6397. Click on Image to Enlarge

These images show young and old white dwarf stars — the burned-out relics of normal stars — in the ancient globular star cluster NGC 6397.

The image at left, taken by a ground-based telescope, shows the dense swarm of hundreds of thousands of stars that make up the globular cluster. The white box outlines the location of the observations made by NASA's Hubble Space Telescope.

The image at top, right, taken by Hubble's Advanced Camera for Surveys, reveals young white dwarfs less than 800 million years old and older white dwarfs between 1.4 and 3.5 billion years old. The photo shows 12 of the 84 white dwarfs in the Hubble study. The blue squares pinpoint the young white dwarfs; the red circles outline the older white dwarfs. The Hubble researchers distinguished the younger from the older white dwarfs based on their colour and brightness. The younger white dwarfs are hotter and therefore bluer and brighter than the older ones.

The astronomers were surprised to find young white dwarfs far away from the cluster's core. They had assumed that the youngsters would reside at the center and migrate over time to the cluster's outskirts. The astronomers proposed that the cluster stars that burn out as white dwarfs are given a boost that propels them to the edge of the cluster.

Close-up images of the white dwarfs are shown at bottom, right. The blue boxes represent the young white dwarfs; the red boxes indicate the older white dwarfs.

Read more @ How White Dwarfs Get Their 'Kicks' from Hubble
White Dwarfs Rocket Away When They're Born @ Universe Today
First Findings On Key Astrophysics Problem - from Science Daily
Radiation Flashes May Help Crack Cosmic Mystery from Science Daily

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Monday, December 03, 2007

Dark Stars of Creation (?)

The universe's first stars may have been bloated behemoths powered by dark matter, suggests a speculative, new study. These 'dark stars' might have delayed the creation of heavy elements, which make up everything from planets to people, as well as cosmic reionisation, which made the universe transparent to light billions of years ago.

Theorists believe the first stars formed in cradles of dark matter, condensing from clouds of gas until their cores became so dense that nuclear fusion ignited, preventing the cores from collapsing further.

But previous research did not consider how the dark matter cradles themselves might affect star formation. When they accounted for dark matter, they discovered it could have had a profound influence on the first stars.

Just what that effect is is still unclear, since no one knows what dark matter is – astronomers merely detect its gravitational pull on normal matter. But if it is made of weakly interacting massive particles, or WIMPs, as many scientists believe, Spolyar and his colleagues say it could drastically alter the physics of the earliest stars.

They used a candidate WIMP called a neutralino in their calculations and found that as a primordial gas cloud contracted, it reached a threshold density in which the dark matter particles swaddling it began to interact with each other. They annihilated on contact, producing particles such as electrons as well as photons of light that then deposited energy into the cloud.
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This could heat up the cloud so much that it would stop contracting, so that it was supported by the annihilation of dark matter rather than by nuclear fusion, like normal stars. Such a 'dark star' would be about as massive as the Sun and would glow at infrared wavelengths. But it would be much larger – depending on the mass of the neutralino used, the star could span anywhere from the distance between the Sun and Uranus in our solar system to nearly 60 times that size.

"To call it a dark star is a bit of a misnomer – it simply has a different source of internal energy to support the star against gravity," says Volker Bromm of the University of Texas in Austin, US, an expert on the universe's first stars who is not a member of the study. "It would be a ball of gas that would have a reddish glow."

Could any of these stars still survive today? Possibly, depending on the neutralino mass, say the researchers. "They could be flying around our galaxy, in which case, the very first generation of stars in the universe (population III' stars) would have been very different from that previously thought", the team says.

Nearly all of the elements in the universe aside from hydrogen and helium were forged inside stars, and "the first stars are the first step in that process". If the first stars were dark, "there could be a major delay or even a stopping of this process", says team member Freese.

"It may turn out that the early star formation and consequently the synthesis of elements went differently than we thought," comments Igor Moskalenko of Stanford University in California, US. "If so, we have evidence of the dark matter presence literally in every cell of our body."

Other 'pop III' stars – which formed inside early galaxies rather than isolated dark matter cradles – would thus have been responsible for seeding the universe with its first heavy elements.

That suggests that heavy elements may not be spread evenly throughout space, since the stars in early galaxies would have enriched their surroundings in these elements and left voids of relatively empty space unenriched, says Bromm. If astronomers ever find a truly primordial cloud of gas in the universe, then it might hint that the first stars were dark.

Similarly, the first stars are thought to have helped ionise the universe within a few hundred million years after the big bang, making it transparent to ultraviolet light. (This phenomenon is actually referred to as 'reionisation', since the universe was a scalding soup of charged particles immediately after the big bang. It then cooled down enough for ions to coalesce into neutral atoms after 370,000 years or so.)

If the first stars were dark, then that suggests the stars in early dwarf galaxies would have been responsible for reionising the universe, says Bromm.

"Another thing that's exciting to me is that we may have a new type of star and we can go look for these things," says Freese. Neutrinos produced by the annihilation of dark matter in the stars might turn up in detectors such as AMANDA and IceCube at the South Pole, and gamma-ray photons produced in the same process could be picked up by NASA's GLAST spacecraft, due to launch in mid-2008.

Bromm says the research is quite speculative, since there are "incredibly many degrees of freedom when it comes to the properties of dark matter". But he adds that the work helps to bridge the gap between studies of dark matter on a particle physics scale and its effect on astronomical objects.

This paper is one of the first in this line of convergence between micro and macro physics.

Universe's first stars may have been dark by Maggie Mckee @ NewScientistSpace

Out Among the Dark Stars - by Paul Gilster @ Centauri Dreams
Were The First Stars Dark? - News Account @ Scientific Blogging
Invisible Matter Loses Cosmic Battle by Jeanna Bryner @ LiveScience

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Saturday, December 01, 2007

Million Degree Plasma

A million-degree plasma cloud in the Orion Nebula.

The emission coloured in blue shows X-ray emission from a hot plasma cloud in the extended regions of the Orion Nebula, detected by the XMM-Newton satellite. The background image has been recorded by the Spitzer Space Telescope in the infrared, showing emission from cool dust.

Stars in our galaxy may often pump out waves of million-degree gas that make surrounding nebulas glow with x-rays.

Astrophysicists focused on the Orion Nebula, a cloud of dense and turbulent gas visible to the naked eye in the night sky, right below the belt of the constellation Orion. Four extremely bright and massive stars, called the Trapezium, light up the nebula.

One stretch of the nebula, about 10 light-years wide, glows with x-rays. This glow apparently results from super-heated gas-some 1.7 million to 2.1 million degree Celsius hot-that pervades the cloud.

Often such vast expanses of super-heated gas come from exploded stars called supernovas or from large collections of very massive stars. Now an international research team using the XMM-Newton space observatory finds this gas seems to flow from just one bright, young, massive star in the Trapezium.

It is believed that our sun was born in an Orion-like environment.

Researchers now hope to understand how these x-ray glows might alter the environments in which planetary systems form, possibly even influencing the very chemistry of worlds.
Huge Stars Seen as Source of Glowing Gas from LiveScience
Star forming region Theta1 Orionis C from Scientific Blogging
ESA's XMM-Newton X-ray observatory images of Orion from ESA

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