Posted on by VirtualAstro

Did The Draconids Perform?

Draconid Meteor Over Somerset UK Credit: Will Gater www.willgater.com

[/caption]

After weeks of speculation of its intensity, the Draconid/Giacobond meteor shower finally arrived. Some astronomers predicted that this normally quiet meteor shower would deliver up to 1000 meteors per hour at its peak – Were they right?

At approximately 20:00 BST (21:00 UT) on October 8th 2011 the shower started in earnest and many in the UK and Europe looked forward to an evening of meteor watching.

Unfortunately, many people were under thick clouds and missed the display, but there were a few places where the clouds cleared and observers were treated to a memorable spectacle.

I have done many meteorwatch evenings in the past, but this one got exciting very quickly and the uncertainty of the amount of meteors was soon doused.

Many people including myself were popping outside and trying to glimpse meteors through the clouds, but most of the time the Meteorwatch Meteor Live View was being used.

Everything was fairly sedate apart from us all moaning about the weather, but then all of a sudden at approximately 20:30 BST (19:30 UT) The Meteor Live View app on the Meteorwatch website went crazy!

Meteor Live View Credit: meteorwatch.org/ Norman Lockyer Observatory UK

Many people started to get good breaks in the clouds including myself and there were reports of dozens of meteors in just a few short minutes, much to the envy and disappointment of those still clouded over.

At this time the International Meteor Organisation (IMO) reported observations of just over 300 meteors per hour (319 ZHR).

The evening continued and to everybody’s delight (to those who could see meteors), there were many. I saw 3 within a couple of seconds and this continued for about an hour.

Eventually rates started to decline, people saw less and the Meteor Live View started to show less activity.

At approximately 22:00 BST (21:00 UT) meteor activity dropped substantially – The show was over!

The IMO results were posted on their website with rates of just under 350 meteors per hour at the peak of the shower, reported by their observing stations.

Credit: IMO

Did the Dracondids/ Giacobonids live up to expectations in the end? I would say yes, a fairly heavy meteor shower, maybe it could be called a mini storm!

Posted on by Ray Sanders

Even the Early Universe Had the Ingredients for Life

The optical image of TN J0924-2201, a very distant radio galaxy at (redshift) z = 5.19, obtained with the Hubble Space Telescope. (c) NASA/STScI/NAOJ.

[/caption]

For us carbon-based life forms, carbon is a fairly important part of the chemical makeup of the Universe. However, carbon and oxygen were not created in the Big Bang, but rather much later in stars. How much later? In a surprising find, scientists have detected carbon much earlier in the Universe’s history than previously thought.

Researchers from Ehime University and Kyoto University have reported the detection of carbon emission lines in the most distant radio galaxy known. The research team used the Faint Object Camera and Spectrograph (FOCAS) on the Subaru Telescope to observe the radio galaxy TN J0924-2201. When the research team investigated the detected carbon line, they determined that significant amounts of carbon existed less than a billion years after the Big Bang.

How does this finding contribute to our understanding of the chemical evolution of the universe and the possibilities for life?

To understand the chemical evolution of our universe, we can start with the Big Bang. According to the Big Bang theory, our universe sprang into existence about 13.7 billion years ago. For the most part, only Hydrogen and Helium ( and a sprinkle of Lithium) existed.

So how do we end up with everything past the first three elements on the periodic table?

Simply put, we can thank previous generations of stars. Two methods of nucleosythesis (element creation) in the universe are via nuclear fusion inside stellar cores, and the supernovae that marked the end of many stars in our universe.

Over time, through the birth and death of several generations of stars, our universe became less “metal-poor” (Note: many astronomers refer to anything past Hydrogen and Helium as metals”). As previous generations of stars died out, they “enriched” other areas of space, allowing future star-forming regions to have conditions necessary to form non-star objects such as planets, asteroids, and comets. It is believed that by understanding how the universe created heavier elements, researchers will have a better understanding of how the universe evolved, as well as the sources of our carbon-based chemistry.

So how do astronomers study the chemical evolution of our universe?

By measuring the metallicity (abundance of elements past Hydrogen on the periodic table) of astronomical objects at various redshifts, researchers can essentially peer back into the history of our universe. When studied, redshifted galaxies show wavelengths that have been stretched (and reddened, hence the term redshift) due to the expansion of our universe. Galaxies with a higher redshift value (known as “z”) are more distant in time and space and provide researchers information about the metallicity of the early universe. Many early galaxies are studied in the radio portion of the electromagnetic spectrum, as well as infra-red and visual.

The research team from Kyoto University set out to study the metallicity of a radio galaxy at higher redshift than previous studies. In their previous studies, their findings suggested that the main era of increased metallicity occurred at higher redshifts, thus indicating the universe was “enriched” much earlier than previous believed. Based on the previous findings, the team then decided to focus their studies on galaxy TN J0924-2201 – the most distant radio galaxy known with a redshift of z = 5.19.

The deep optical spectrum of TN J0924-2201 obtained with FOCAS on the Subaru Telescope. The red arrows point to the carbon emission line.

The research team used the FOCAS instrument on the Subaru Telescope to obtain an optical spectrum of galaxy TN J0924-2201. While studying TN J0924-2201, the team detected, for the first time, a carbon emission line (See above). Based on the detection of the carbon emission line, the team discovered that TN J0924-2201 had already experienced significant chemical evolution at z > 5, thus an abundance of metals was already present in the ancient universe as far back as 12.5 billion years ago.

If you’d like to read the team’s findings you can access the paper Chemical properties in the most distant radio galaxy – Matsuoka, et al at: http://arxiv.org/abs/1107.5116

Source: NAOJ Press Release

Posted on by Tammy Plotner

First Look At Interstellar Turbulence

Regions of gas where the density and magnetic field are changing rapidly as a result of turbulence. [Technical note: the image shows the gradient of linear polarisation over an 18-square-degree region of the Southern Galactic Plane.] Image credit – B. Gaensler et al. Data: CSIRO/ATCA

[/caption]

All of the space that surrounds us isn’t empty. We’ve always known the Milky Way was filled with great areas of turbulent gas, but we’ve never been able to see them… Until now. Professor Bryan Gaensler of the University of Sydney, Australia, and his team used a CSIRO radio telescope in eastern Australia to create this first-ever look which was published in Nature today.

“This is the first time anyone has been able to make a picture of this interstellar turbulence,” said Professor Gaensler. “People have been trying to do this for 30 years.”

So what’s the point behind the motion? Turbulence distributes magnetism, disperses heat from supernova events and even plays a role in star formation.

“We now plan to study turbulence throughout the Milky Way. Ultimately this will help us understand why some parts of the galaxy are hotter than others, and why stars form at particular times in particular places,” Professor Gaensler said.

Employing CSIRO’s Australia Telescope Compact Array because “it is one of the world’s best telescopes for this kind of work,” as Dr. Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science, explained, the team set their sights about 10,000 light years away in the constellation of Norma. Their goal was to document the radio signals which emanate from that section of the Milky Way. As the radio waves pass through the swirling gas, they become polarized. This changes the direction in which the light waves can “vibrate” and the sensitive equipment can pick up on these small differentiations.

By measuring the polarization changes, the team was able to paint a radio portrait of the gaseous regions where the turbulence causes the density and magnetic fields to fluctuate wildly. The tendrils in the image are also important, too. They show just how fast changes are occurring – critical for their description. Team member Blakesley Burkhart, a PhD student from the University of Wisconsin, made several computer simulations of turbulent gas moving at different speeds. By matching the simulations with the actual image, the team concluded “the speed of the swirling in the turbulent interstellar gas is around 70,000 kilometers per hour — relatively slow by cosmic standards.”

Original Story Source: CSIRO Astronomy and Space Science News Release. For Further Reading: Low Mach number turbulence in interstellar gas revealed by radio polarization gradients.

Posted on by Tammy Plotner

Rare New Galaxy Reveals Black Hole Jet Secrets

Composite image of Speca: Optical SDSS image of the galaxies in yellow, low resolution radio image from NVSS in blue, high resolution radio image from GMRT in red. CREDIT: Hota et al., SDSS, NCRA-TIFR, NRAO/AUI/NSF.

[/caption]

A newly discovered galaxy is aiding astronomers in the research into the early evolution of individual galaxies and galaxy clusters. Named Speca, this unique finding is only the second spiral galaxy known to produce “jets” – streams of subatomic particles emitted from the nucleus. What’s more, it’s also one of two which shows this activity happened in separate intervals.

As astronomers know, galaxy jets are formed at the heart of activity where a supermassive black hole is present. While both elliptical and spiral galaxies have known supermassive black holes, only one had been known to produce copious amounts of material from its poles – Messier 87. Now Speca is changing the way researchers look for recurring activity.

“This is probably the most exotic galaxy with a black hole ever seen. It has the potential to teach us new lessons about how galaxies and clusters of galaxies formed and developed into what we see today,” said Ananda Hota, of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), in Taiwan.

Located in a galaxy cluster about 1.7 billion light-years, Speca (an acronym for Spiral-host Episodic radio galaxy tracing Cluster Accretion) made its presence known to Ananda’s researches via an image which joined data from the visible-light Sloan Digital Sky Survey and the FIRST survey done with the National Science Foundation’s Very Large Array (VLA) radio telescope. Subsequent observations with the Lulin optical telescope in Taiwan and ultraviolet data from NASA’s GALEX satellite verified the lobes of material were part of an active, star-forming galaxy. Ananda’s team further refined their studies with information from the NRAO VLA Sky Survey (NVSS), then made new observations with the Giant Meterwave Radio Telescope (GMRT) in India. Each telescope set provided more and more clues to solving the puzzle.

“By using these multiple sets of data, we found clear evidence for three distinct epochs of jet activity,” Ananda explained. But the real excitement began when the low-frequency nature of the oldest, outermost lobes was examined. It was an artifact which should have disappeared with time.

“We think these old, relic lobes have been ‘re-lighted’ by shock waves from rapidly moving material falling into the cluster of galaxies as the cluster continues to accrete matter,” said Ananda. “All these phenomena combined in one galaxy make Speca and its neighbors a valuable laboratory for studying how galaxies and clusters evolved billions of years ago.”

Sandeep K. Sirothia of India’s National Centre for Radio Astrophysics, Tata Institute of Fundamental Research (NCRA-TIFR) said, “The ongoing low-frequency TIFR GMRT Sky Survey will find many more relic radio lobes of past black hole activity and energetic phenomena in clusters of galaxies like those we found in Speca.” Also, Govind Swarup of NCRA-TIFR, who is not part of the team, described the finding as “an outstanding discovery that is very important for cluster formation models and highlights the importance of sensitive observations at meter wavelengths provided by the GMRT.”

Stay close to your radio, folks… Who knows what we’ll hear in the future!

Original Story Source: National Radio Astronomy Observatory News.

Posted on by Tammy Plotner

Star Transforms Into A Diamond Planet

Schematic view of the Pulsar-Planet system PSR J1719-1438 showing the pulsar with 5.7 ms rotation period in the centre, and the orbit of the planet in comparison to the size of the sun (marked in yellow). Credit: Swinburne Astronomy Productions, Swinburne University of Technology

[/caption]

“Remember when you were young… You shone like the sun.” Four thousand light years away in the constellation of Serpens, a millisecond pulsar binary is pounding out its heartbeat. Meanwhile an international research team of scientists from Australia, Germany, Italy, the UK and the USA, including Prof. Michael Kramer from Max Planck Institute for Radio Astronomy in Bonn, German are listening in. Utilizing the 64-m radio telescope in Parkes, Australia, the team made a rather amazing discovery. The companion star could very well be an ultra-low mass carbon white dwarf… one that’s transformed itself into a planet made of pure diamond.

“The density of the planet is at least that of platinum and provides a clue to its origin”, said the research team leader, Prof. Matthew Bailes of Swinburne University of Technology in Australia. Bailes leads the “Dynamic Universe” theme in a new wide-field astronomy initiative, the Centre of Excellence in All-sky Astrophysics (CAASTRO). He is presently on scientific leave at Max Planck Institute for Radio Astronomy.

Like a lighthouse, PSR J1719-1438 emits radio signals which sweep around methodically. When researchers noticed a specific modulation every 130 minutes, they realized they were picking up a signature of planetary proportions. Given the distance of its orbit, the companion could very well be the core of a once massive star whose material was consumed by pulsar’s gravity.

“We know of a few other systems, called ultra-compact low-mass X-ray binaries, that are likely to be evolving according to the scenario above and may likely represent the progenitors of a pulsar like J1719-1438” said Dr. Andrea Possenti, of INAF-Osservatorio Astronomicodi Cagliari.

With almost all of its original mass gone, very little of the companion could be left save for carbon and oxygen… and stars still rich in lighter elements like hydrogen and helium won’t fit the equation. This leaves a density which could very well be crystalline – and a composition which closely resembles diamond.

“The ultimate fate of the binary is determined by the mass and orbital period of the donor star at the time of mass transfer. The rarity of millisecond pulsars with planet-mass companions means that producing such ‘exotic planets’ is the exception and not the rule, and requires special circumstances”, said Dr. Benjamin Stappers from the University of Manchester.

“The new discovery came as a surprise for us. But there is certainly a lot more we’ll find out about pulsars and fundamental physics in the following years”, concludes Michael Kramer.

Shine on, you crazy diamond…

Original Story Source: Max Planck Institut for Radio Astronomy and Transformation of a Star into a Planet in a Millisecond Pulsar Binary.

Posted on by Tammy Plotner

HARPS Tunes In On “Noisy” Planets

Montage of the HARPS spectrograph and the 3.6m telescope at La Silla. The upper left shows the dome of the telescope, while the upper right illustrates the telescope itself. The HARPS spectrograph is shown in the lower image during laboratory tests. The vacuum tank is open so that some of the high-precision components inside can be seen. Credit: European Southern Observatory

[/caption]

Able to achieve an astounding precision of 0.97 m/s (3.5 km/h), with an effective precision of the order of 30 cms-1, the High Accuracy Radial velocity Planet Searcher (HARPS) echelle spectrograph has already discovered 16 planetary objects in the southern hemisphere and has now logged four more. And that’s only the beginning…

“A long-period companion, probably a second planet, is also found orbiting HD7449. Planets around HD137388, HD204941, and HD7199 have rather low eccentricities (less than 0.4) relative to the 0.82 eccentricity of HD7449b. All these planets were discovered even though their hosting stars have clear signs of activity.” says X. Dumusque (et al). “Solar-like magnetic cycles, characterized by long-term activity variations, can be seen for HD137388, HD204941 and HD7199, whereas the measurements of HD7449 reveal a short-term activity variation, most probably induced by magnetic features on the stellar surface.”

Using radial velocity is currently the preferred method for detecting new planets. But, despite the quality of the equipment, low mass planets placed at a great distance from the host star become problematic because of the star’s own “noise”. RV is an indirect method which utilizes the presence of star wobble to spot orbiting bodies. Unfortunately, normal star activity such as magnetic cycles, spots and plagues can produce similar signals, but now long term variables like these are being fine tuned into the equation.

“The planets announced in this paper for the first time have been discovered even though their host stars display clear signs of activity. We have found that HD7449 exhibits signs of short term activity, whereas HD7199, HD137388, and HD204941 have solar-like magnetic cycles.” says Dumusque. “When examining the RVs and the fitted planets for HD7199, HD137388, and HD204941, it is clear that magnetic cycles induce RV variations that could be misinterpreted as long-period planetary signature. Therefore, the long-term variations in the activity index have to be studied properly to distinguish between the real signature of a planet and long-term activity noise.”

The paper then goes on to explain our Sun should show RV variations of 10ms?1 over its cycle and that it is typical behavior for solar-like stars. Perhaps all stars which display magnetic cycles also have long-term RV variations? “The high precision HARPS sample, composed of 451 stars, provides a good set of measurements to search for this activity-RV correlation.” says Lovis (et al). “A more complete study is in progress and will be soon published.”

Factual Information Courtesy of Wikipedia. Further Reading: The HARPS search for southern extra-solar planets. XXX. Planetary systems around stars with solar-like magnetic cycles and short-term activity variation.

Posted on by Tammy Plotner

Searching For Gravitational Waves

Two-dimensional representation of gravitational waves generated by two neutron stars surrounding each other. Credit: NASA

[/caption]Colliding neutron stars and black holes, supernova events, rotating neutron stars and other cataclysmic cosmic events… Einstein predicted they would all have something in common – oscillations in the fabric of space-time. This summer European scientists have joined forces to prove Einstein was right and capture evidence of the existence of gravitational waves.

Europe’s two ground-based gravitational wave detectors GEO600 (a German/UK collaboration) and Virgo (a collaboration between Italy, France, the Netherlands, Poland and Hungary) are underway with a joint observation program which will continue over the summer, ending in September 2011. The detectors consist of a pair of joined arms placed in a horizontal L-shaped configuration. Laser beams are then passed down the arms. Suspended under vacuum at the ends of the arms is a mirror which returns the beam to a central photodetector. The detectors work by measuring tiny changes (less than the diameter of a proton), caused by a passing gravitational wave, in the lengths (hundreds or thousands of meters). The periodic stretching and shrinking of the arms is then recorded as interference patterns.

Much like our human ears are able to distinguish the direction of sound from being spaced apart, so having interferometers placed at different locations benefits the chances of picking up a gravitational wave signal. By placing receivers at a distance, this also helps to eliminate the chances of picking up a mimicking terrestrial signal, since it would be unlikely for it to have the same characteristics at two locations while a genuine signal would remain the same.

“If you compare GEO600 and Virgo, you can see that both detectors have similar sensitivities at high frequencies, at around 600Hz and above”, says Dr Hartmut Grote, a scientist at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) and the Leibniz University in Hannover, Germany. “That makes it very interesting for us to search this band for possible gravitational waves associated with supernovae or gamma-ray bursts that are observed with conventional telescopes.”

Of all phenomena, gamma-ray bursts are expected to be one of the strongest sources of gravitational waves. As the most luminous transient event in the known Universe, this collapse of a supermassive star core into a neutron star or black hole may be the most perfect starting point for the search. As of now, the frequencies will depend on the mass and may extend up to the kHz band. But don’t get too excited, because the nature of gravitational wave signals is weak and chances of picking up on it is low. However, thanks to Virgo’s excellent sensitivity at low frequencies (below 100 Hz), it is a prime candidate for gathering signals from isolated pulsars where the gravitational wave signal frequency should be at around 22Hz.

And we’ll be listening for the results…

Original Story Source: Albert Einstein Institute News.

Posted on by Steve Nerlich

The Russian Hubble?

The Spektr-R spacecraft. If you are thinking it looks nothing like the Hubble Space telescope, you'd be right.

[/caption]

This is hardly breaking news, but there’s a new Russian space telescope in town. With a name like an anime character, Spektr R was launched on 18 July 2011 and its 10 metre carbon fibre dish was deployed a week later. It’s a radio telescope and – via a very large baseline array project known as RadioAstron – it will become arguably the world’s biggest radio telescope – and by a very long shot.

Following so closely after the Space Shuttle fleet’s retirement, the media has latched onto the idea that this represents a major step up from the Hubble Space Telescope and a further indication of the USA’s decline from space. But, nah…

Don’t get me wrong, when fully operational RadioAstron will be the biggest ever interferometer and is likely to deliver some great science when it gets up to speed. Well done, Roscosmos. But the various comparisons made between it and Hubble are a little spurious.

RadioAstron’s angular resolution is reported as 7 microarc seconds (or 0.000007 arcseconds) while Hubble’s resolution is generally reported as 0.05 arc seconds – so RadioAstron is reported as having over a thousand times more resolution. Well, sort of – but not really.

Firstly, the 10 metre radio mirror of Spektr R is designed to detect centimetre range wavelength light, while Hubble’s 2.4 metre mirror, is capable of detecting wavelengths in the visible light range of 350-790 nanometre range (and some non-visible infrared light too).

Angular resolution arises from the relationship between the wavelength of light you are observing and the size of your aperture. So, at the single instrument level Hubble rules supreme in the resolution stakes.

The image detail you can gain from arraying radio telescopes. Blobby false colour becomes more detailed blobby false colour (but there's useful science data there). Credit: VSOP.

The resolution assigned to RadioAstron (the telescope array) arises from the ‘virtual’ dish diameter created by Spektr R’s orbit, when arrayed with ground-based radio telescopes – which may eventually include Earth’s largest dish, the 300 metre Arecibo dish and Earth’s largest steerable dish, the 110 metre Greenbank radio telescope.

Spektr R will orbit the Earth via a highly elliptical orbit with a perigee of 10,000 kilometres and an apogee of 390,000 kilometres – so giving an elliptical orbit with a semi-major axis of 200,000 kilometres. That sounds like one big dish, huh… although it isn’t, really – just virtually.

Don’t get me wrong, there is a huge increase in information to be gained from arraying Spektr R’s one data point with other ground based observatories’ data points. But nonetheless, it is just radio light conveyed information – which just can’t deliver the level of detail that nanometre wavelength visible light can carry.

That’s why you can usefully create radio telescope arrays, but you can’t gain much value from arraying visible light telescopes (at least not yet). The information conveyed by radio light is spread widely enough so that you can estimate the information it is carrying from just detecting it at two widely spread detectors – and then superimposing that data. The fine detailed information contained in visible light is just too complex to allow this.

So putting up RadioAstron up as a contender to the beloved Hubble Space Telescope makes no sense. It is a totally different scientific project that will deliver totally different – and hopefully awesome – scientific data. Ad astra. If we want a step up from Hubble, we need to get the James Webb Space Telescope back into production.

Posted on by Steve Nerlich

Astronomy Without A Telescope – Oh-My-God Particles

Centaurus A - the closest galaxy with an active galactic nucleus - a mere 10-16 million light years away. Now I wonder where all those ultra high energy cosmic rays are coming from. Hmmm...

[/caption]

Cosmic rays are really sub-atomic particles, being mainly protons (hydrogen nuclei) and occasionally helium or heavier atomic nuclei and very occasionally electrons. Cosmic ray particles are very energetic as a result of them having a substantial velocity and hence a substantial momentum.

The Oh-My-God particle detected over Utah in 1991 was probably a proton traveling at 0.999 (and add another 20 x 9s after that) of the speed of light and it allegedly carried the same kinetic energy as a baseball traveling at 90 kilometers an hour.

Its kinetic energy was estimated at 3 x 1020 electron volts (eV) and it would have had the collision energy of 7.5 x 1014 eV when it hit an atmospheric particle – since it can’t give up all its kinetic energy in the collision. Fast moving debris carries some of it away and there’s some heat loss too. In any case, this is still about 50 times the collision energy we expect the Large Hadron Collider (LHC) will be able to generate at full power. So, this gives you a sound basis to scoff at doomsayers who are still convinced that the LHC will destroy the Earth.

Now, most cosmic ray particles are low energy, up to 1010 eV – and arise locally from solar flares. Another more energetic class, up to 1015 eV, are thought originate from elsewhere in the galaxy. It’s difficult to determine their exact source as the magnetic fields of the galaxy and the solar system alter their trajectories so that they end up having a uniform distribution in the sky – as though they come from everywhere.

But in reality, these galactic cosmic rays probably come from supernovae – quite possibly in a delayed release process as particles bounce back and forth in the persisting magnetic field of a supernova remnant, before being catapulted out into the wider galaxy.

And then there are extragalactic cosmic rays, which are of the Oh-My-God variety, with energy levels exceeding 1015 eV, even rarely exceeding 1020 eV – which are more formally titled ultra-high-energy cosmic rays. These particles travel very close to the speed of light and must have had a heck of kick to attain such speeds.

Left image: The energy spectrum of cosmic rays approaching Earth. Cosmic rays with low energies come in large numbers from solar flares (yellow range). Less common, but higher energy cosmic rays originating from elsewhere in the galaxy are in the blue range. The least common but most energetic extragalactic cosmic rays are in the purple range. Right image: The output of the active galactic nucleus of Centaurus A dominates the sky in radio light - this is its apparent size relative to the full Moon. It is likely that nearly all extragalactic cosmic rays that reach Earth originate from Centaurus A.

However, a perhaps over-exaggerated aura of mystery has traditionally surrounded the origin of extragalactic cosmic rays – as exemplified in the Oh-My-God title.

In reality, there are limits to just how far away an ultra-high-energy particle can originate from – since, if they don’t collide with anything else, they will eventually come up against the Greisen–Zatsepin–Kuzmin (GZK) limit. This represents the likelihood of a fast moving particle eventually colliding with a cosmic microwave background photon, losing momentum energy and velocity in the process. It works out that extragalactic cosmic rays retaining energies of over 1019 eV cannot have originated from a source further than 163 million light years from Earth – a distance known as the GZK horizon.

Recent observations by the Pierre Auger Observatory have found a strong correlation between extragalactic cosmic rays patterns and the distribution of nearby galaxies with active galactic nuclei. Biermann and Souza have now come up with an evidence-based model for the origin of galactic and extragalactic cosmic rays – which has a number of testable predictions.

They propose that extragalactic cosmic rays are spun up in supermassive black hole accretion disks, which are the basis of active galactic nuclei. Furthermore, they estimate that nearly all extragalactic cosmic rays that reach Earth come from Centaurus A. So, no huge mystery – indeed a rich area for further research. Particles from an active supermassive black hole accretion disk in another galaxy are being delivered to our doorstep.

Further reading: Biermann and Souza On a common origin of galactic and extragalactic cosmic rays.

Posted on by Tammy Plotner

LOFAR So Far… Digging Deep Into Our Universe

A very small part of the raw LOFAR image of the field centered on the bright quasar 3C196. It shows tens of discrete sources, the faintest having a flux density of only a few mJy at 150 MHz.The image has an angular resolution of 8 arcseconds. The image still needs to be deconvolved. The data was processed by Dr. Panos Labropoulos on the EoR-cluster at the University of Groningen.

[/caption]

The International LOFAR telescope is a Pan-European collaborative project led by ASTRON Netherlands Institute for Radio Astronomy. The radio telescope integrates thousands of simple dipole receivers with effective digital signal processing and high-performance computing. LOFAR can rapidly take in wide areas of the sky, aiming in multiple directions simultaneously. It also utilizes unexplored low frequencies, around around 150 MHz, which allows astronomers new insights. What has LOFAR done so far? Try capturing faint radio sources never revealed before.

An international team led by astronomers at ASTRON and the Kapteyn Institute of the University of Groningen have used the LOFAR telescope, designed and constructed by ASTRON, to make the deepest wide-field images of the sky to date. At the conference, the trouble of dealing with foreground noise was the topic – foreground noise that makes it nearly impossible to get a good radio view of the distant Universe. What researchers are looking for is the Epoch of Reionization (EoR) – a time which is postulated to have occurred in the period between about 400 and 800 million years after the Big Bang. Says the team, “During the EoR the neutral hydrogen was slowly disappearing, probably as a result of the strong ‘ionizing’ power of the first stars and quasars. Detecting the EoR is one of the hottest projects in astronomy today.”

Detecting a signal from a 13.8 billion year old event would be akin to the Holy Grail of radio astronomy, but the team of astronomers based at ASTRON and the Kapteyn Institute of the University of Groningen, headed by Prof. Ger de Bruyn, Dr. Michiel Brentjens, Prof. Leon Koopmans and Prof. Saleem Zaroubi, are willing to sift through the noise to diclose new findings. The LOFAR data images were obtained in a 6-hour synthesis on the night of 29/30 January 2011 and the evening of 1 April 2011 using 18 core stations and 7 remote stations. Signals were recorded with the High Band Antennas blanketing the frequency range from 115 – 163 MHz and then further refined.

One of the fields covered by the radio imaging is centered at the celestial North Pole since it is available year round from LOFAR’s central position. The second field is dedicated to bright, compact quasar 3C196 in the constellation of Lynx. The high resolution images already match – or even surpass – the best published images taken with the Giant Meter Wavelength Radio telescope (GMRT) in India. The images reveal a significant number of both very bright and very faint sources, spanning a so-called dynamic range of more than 200,000:1 in brightness between sources.

“This is an important record for the time being for LOFAR. The image quality, however, is still not perfect and significant improvements can be expected in the months ahead using improved knowledge of the effects of the LOFAR station beams.” says the team. “Continued efforts are also needed to improve the software to deal with imaging artifacts and the ionosphere. These two fields and several others will be observed for about 100 nights to conclusively detect signals from the EoR.”

Sounds like LOFAR is doing great so far!

Original Story Source: ASTRON.