Posted on by Nancy Atkinson

Astronomers ‘Time Travel’ to 16th Century Supernova

Tycho's Supernova Remnant. Credit: Spitzer, Chandra and Calar Alto Telescopes.

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On November 11, 1572 Danish astronomer Tycho Brahe and other skywatchers observed what they thought was a new star. A bright object appeared in the constellation Cassiopeia, outshining even Venus, and it stayed there for several months until it faded from view. What Brahe actually saw was a supernova, a rare event where the violent death of a star sends out an extremely bright outburst of light and energy. The remains of this event can still be seen today as Tycho’s supernova remnant. Recently, a group of astronomers used the Subaru Telescope to attempt a type of time travel by observing the same light that Brahe saw back in the 16th century. They looked at ‘light echoes’ from the event in an effort to learn more about the ancient supernova.

A ‘light echo’ is light from the original supernova event that bounces off dust particles in surrounding interstellar clouds and reaches Earth many years after the direct light passes by; in this case, 436 years ago. This same team used similar methods to uncover the origin of supernova remnant Cassiopeia A in 2007. Lead project astronomer at Subaru, Dr. Tomonori Usuda, said “using light echoes in supernova remnants is time-traveling in a way, in that it allows us to go back hundreds of years to observe the first light from a supernova event. We got to relive a significant historical moment and see it as famed astronomer Tycho Brahe did hundreds of years ago. More importantly, we get to see how a supernova in our own galaxy behaves from its origin.”

The view of the light echoes from Tycho’s supernova. Credit: Subaru Telescope
The view of the light echoes from Tycho’s supernova. Credit: Subaru Telescope

On September 24, 2008, using the Faint Object Camera and Spectrograph (FOCAS) instrument at Subaru, astronomers looked at the signatures of the light echoes to see the spectra that were present when Supernova 1572 exploded. They were able to obtain information about the nature of the original blast, and determine its origin and exact type, and relate that information to what we see from its remnant today. They also studied the explosion mechanism.

What they discovered is that Supernova 1572 was very typical of a Type Ia supernova. In comparing this supernova with other Type Ia supernovae outside our galaxy, they were able to show that Tycho’s supernova belongs to the majority class of Normal Type Ia, and, therefore, is now the first confirmed and precisely classified supernova in our galaxy.

This finding is significant because Type Ia supernovae are the primary source of heavy elements in the Universe, and play an important role as cosmological distance indicators, serving as ‘standard candles’ because the level of the luminosity is always the same for this type of supernova.

For Type Ia supernovae, a white dwarf star in a close binary system is the typical source, and as the gas of the companion star accumulates onto the white dwarf, the white dwarf is progressively compressed, and eventually sets off a runaway nuclear reaction inside that eventually leads to a cataclysmic supernova outburst. However, as Type Ia supernovae with luminosity brighter/fainter than standard ones have been reported recently, the understanding of the supernova outburst mechanism has come under debate. In order to explain the diversity of the Type Ia supernovae, the Subaru team studied the outburst mechanisms in detail.

This observational study at Subaru established how light echoes can be used in a spectroscopic manner to study supernovae outburst that occurred hundreds of years ago. The light echoes, when observed at different position angles from the source, enabled the team to look at the supernova in a three dimensional view. This study indicated Tycho’s supernova was an aspherical/nonsymmetrical explostion. For the future, this 3D aspect will accelerate the study of the outburst mechanism of supernova based on their spatial structure, which, to date, has been impossible with distant supernovae in galaxies outside the Milky Way.

The results of this study appear in the 4 December 2008 issue of the science journal Nature.

Source: Subaru Telescope

Posted on by Nancy Atkinson

Holiday Glitter With Omega Centauri

Omega Centauri. Credit: ESO

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A new image of Omega Centauri shows the globular cluster glittering away as one of the finest jewels of the southern hemisphere night sky. It contains millions of stars and is located about 17,000 light-years from Earth in the constellation of Centaurus, and sparkles at magnitude 3.7, appearing nearly as large as the full moon on the southern night sky. Visible with the unaided eye from a clear, dark observing site, when seen through even a modest amateur telescope, the Omega Centauri can be seen as incredible, densely packed sphere of glittering stars. But when astronomers use a professional telescopes, they are able to uncover amazing secrets of this beautiful globular cluster.

This new image is based on data collected with the Wide Field Imager (WFI), mounted on the 2.2-metre diameter Max-Planck/ESO telescope, located at ESO’s La Silla observatory, high up in the arid mountains of the southern Atacama Desert in Chile. Omega Centauri is about 150 light-years across and is the most massive of all the Milky Way’s globular clusters. It is thought to contain some ten million stars!

Recent research into this intriguing celestial giant suggests that there is a medium sized black hole sitting at its center. Observations made with the Hubble Space Telescope and the Gemini Observatory showed that stars at the cluster’s center were moving around at an unusual rate — the cause, astronomers concluded, was the gravitational effect of a massive black hole with a mass of roughly 40,000 times that of the Sun.

The presence of this black hole is just one of the reasons why some astronomers suspect Omega Centauri to be an imposter. Some believe that it is in fact the heart of a dwarf galaxy that was largely destroyed in an encounter with the Milky Way. Other evidence (see here and here) points to the several generations of stars present in the cluster — something unexpected in a typical globular cluster, which is thought to contain only stars formed at one time. Whatever the truth, this dazzling celestial object provides professional and amateur astronomers alike with an incredible view on clear dark nights.

Source: ESO

Posted on by Nancy Atkinson

Sources of Earth-Bombarding Cosmic Rays May Have Been Located

The cosmic ray hot spots were identified in the two red-colored regions near the constellation Orion. Courtesy John Pretz, LANL

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Last week’s announcement of a puzzling and unknown source of high energy cosmic rays bombarding the Earth is now joined by another discovery of two sources of unexpected cosmic rays from nearby regions of space. A Los Alamos National Laboratory cosmic-ray observatory has seen for the first time two distinct hot spots that appear to be bombarding Earth with an excess of cosmic rays. “These two results may be due to the same, or different, astrophysical phenomenon, said Jordan Goodman, principal investigator for the Milagro observatory, commenting on last week’s announcement by the ATIC experiment and the new discovery by his team. “However, they both suggest the presence of high-energy particle acceleration in the vicinity of the earth. Our new findings point to general locations for the localized excesses of cosmic-ray protons.” The cosmic rays appear to originate from an area in the sky near the constellation Orion.

Researchers used Los Alamos’ Milagro cosmic-ray observatory to peer into the sky above the northern hemisphere for nearly seven years starting in July 2000. The observatory is unique in that it monitors the entire sky above the northern hemisphere. Because of its design and field of view, Milagro was able to record over 200 billion cosmic-ray collisions with the Earth’s atmosphere.

Cosmic rays are high-energy particles that move through our Galaxy from sources far away. No one knows exactly where cosmic rays come from, but scientists theorize they might originate from supernovae—massive stars that explode— from quasars or perhaps from other exotic, less-understood or yet-to-be-discovered sources within the universe.

“Our observatory is unique in that we can detect events of low enough energies that we were able to record enough cosmic-ray encounters to see a statistically significant fractional excess coming from two distinct regions of the sky,” said collaborator Brenda Dingus.

Because Milagro was able to record so many cosmic-ray events, researchers for the first time were able to see statistical peaks in the number of cosmic-ray events originating from specific regions of the sky near the constellation Orion. The region with the highest hot spot of cosmic rays is a concentrated bulls eye above and to the right visually of Orion, near the constellation Taurus. The other hot spot is a comma-shaped region visually occurring near the constellation Gemini.

But the researchers cannot be sure they have precisely located the sources of the cosmic rays. “Whatever the source of the protons we observed with Milagro, their path to Earth is deflected by the magnetic field of the Milky Way so that we cannot directly tell exactly where they originate,” said Goodman. “And whether the regions of excess seen by Milagro actually point to a source of cosmic rays, or are the result of some other unknown nearby effect is an important question raised by our observations.”

A new, second-generation cosmic ray observatory has been proposed, which may be able to solve the mystery of the origin of cosmic rays. The experiment, named the High Altitude Water Cherenkov experiment (HAWC), would be built at a high-altitude site in Mexico.

Sources: UMD, Science Daily

Posted on by Ian O'Neill

Asteroseismology: Observing Stars Vibrate with CoRoT

Modes of solar oscillation plotted over our Sun. Could the same things be done with other stars? (NASA/TRACE/NCAR)

[/caption]Observing a stars brightness pulsate may reveal its internal structure say researchers using the Convection Rotation and Planetary Transits (CoRoT) observatory. The highly sensitive orbital telescope can detect tiny variations in a distant star’s brightness, leading astronomers into a new field of stellar seismology called “asteroseismology.”

Seismology is more commonly used by scientists on Earth to see how waves travel through the terrestrial crust, thereby revealing the structure of the material below us. Even solar physicists use the method of helioseismology to understand the interior of our Sun by observing its wobble. Now, by observing the slight changes in stellar brightness, it is possible to remotely probe deep into the inner workings of a distant star…

CoRoT is a joint French Space Agency (CNES) and European Space Agency (ESA) mission to detect slight variations in the brightness of stars launched in 2006. As extrasolar planets pass in front of (or “transit”) a star, the brightness will decrease. The highly sensitive 27 cm-diameter telescope and spectroscopic instrumentation has the ability of detecting extrasolar rocky planets a few times the size of Earth and new gas giants (a.k.a. Hot Jupiters).

Another mission objective for the 630 kg satellite is to detect luminosity variations associated with acoustic pulsations passing through the body of the star. A similar method known as helioseismology uses the Solar and Heliospheric Observatory (SOHO) to detect the propagation of pressure waves through the Sun so a better idea of solar internal dynamics and structure can be gained.

CoRoT has been watching three stars, 20-40% more massive than the Sun, vibrate in reaction to the convective processes on the stellar surfaces. Some areas will expand and cool, whilst others with contract and heat up. This creates an oscillation, and a pulsation in brightness, providing information about the inner structure of these distant stars. The three stars brightened and dimmed 1.5 times more dramatically than solar helioseismology observations. However, this is still 25% weaker than expected from theory, so it would seem stellar physics still has a long way to go.

“This really marks the start of a completely new era of space-based asteroseismology,” said Joergen Christensen-Dalsgaard of the University of Aarhus in Denmark. “It shows that CoRoT can do what it set out to do.”

Asteroseismology can also be used to gauge the precise age of a star. Usually, the age of a star is determined by looking at a star cluster where it is assumed the majority of the stars are of a similar age. However, as a star ages, different elements undergo nuclear fusion at different times. This alters the star’s interior structure and therefore alters the vibrational characteristics of the star. This can be detected by CoRoT, hopefully aiding astronomers when deducing the precise ago of a particular star.

“In principle, you can look at one star all on its own and determine how old it is,” adds Michael Montgomery of the University of Texas.

Source: New Scientist

Posted on by Ian O'Neill

Feeding Time at the Stellar Zoo: Infant Stars Generate Lots of Gas

Artist's impression of a young star with surrounding disk of dust (ESO/L. Calçada)

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Understanding how stars form is critical to astronomers. If we can gain a better understanding of how intermediate-size infant stars grow, we can begin to answer some of the most perplexing questions hanging over the evolution of our own Solar System. Unfortunately, the nearest star forming regions are about 500 light years away, meaning that astronomers cannot simply use traditional optical telescopes to peer into star-forming disks of gas and dust. So, researchers working with the European Southern Observatory (ESO) are combining high resolution spectroscopic and interferometry observations to give the most detailed view yet of infant stars eating away at their proto-planetary disk, blasting out violent stellar winds as they do so…

It sounds like baby stars are very much like their human counterparts. They need a conveyor belt of food supplying their development and they blast huge amounts of waste back out in the form of gas. These findings come from researchers using the ESO’s Very Large Telescope Interferometer (VLTI), giving us milli-arcsecond resolution when focusing on these star-forming regions. The detail this provides is equivalent to studying the period (‘full stop’ as I prefer to call it) at the end of this sentence at a distance of 50 km (31 miles).

This high resolution is achieved by combining the light from two or more telescopes separated by a certain distance. This distance is known as the “baseline,” and interferometers such as the VLTI have a large baseline (of up to 200 metres), simulating a telescope diameter equivalent to this distance. However, the VLTI now has another trick up its sleeve. The AMBER spectrometer can be used in conjunction with the interferometer observations to give a more complete view of these feeding stars, probing deep into the spectrum of light being emitted from the region.

“So far interferometry has mostly been used to probe the dust that closely surrounds young stars. But dust is only one percent of the total mass of the discs. Their main component is gas, and its distribution may define the final architecture of planetary systems that are still forming.” – Eric Tatulli, co-leader of the VLTI international collaboration from Grenoble, France.

The Herbig Ae/Be star R Coronae Australis, a young intermediate-size star (2MASS)
The Herbig Ae/Be star R Coronae Australis, a young intermediate-size star (2MASS)
Using the combined power of the VLTI and AMBER instrument, astronomers have been able to map this gas surrounding six stars belonging to the Herbig Ae/Be family. These particular stars are typically less than 10 million years old and a few times the mass of our Sun. They are very active stars in the process of forming, dragging huge amounts of material from a surrounding disk of dust.

Until now, astronomers have not been able to detect gas emission from young stars feeding on their stellar disks, thereby keeping the physical processes acting close to the star a mystery.

“Astronomers had very different ideas about the physical processes that have been traced by the gas. By combining spectroscopy and interferometry, the VLTI has given us the opportunity to distinguish between the physical mechanisms responsible for the observed gas emission,” says co-leader Stefan Kraus from Bonn in Germany. In two of the Herbig Ae/Be stars, there is evidence for a large quantity of dust falling into them, thereby increasing their masses. In four cases, there is evidence for a strong stellar wind, forming an extended stellar gas outflow.

The VLTI observations also reveal dust from the surrounding disk is much closer than one would expect. Usually there is a cut-off distance for dust location as the stars heat will cause it to vaporize. However, it would appear in one case that gas between the star and dusty disk shields the dust from evaporating; the gas acts as a radiation-block, allowing the dust to extend closer to the star.

“Future observations using VLTI spectro-interferometry will allow us to determine both the spatial distribution and motion of the gas, and might reveal whether the observed line emission is caused by a jet launched from the disc or by a stellar wind“, Kraus added.

These phenomenal observations of star-forming dust disks and gas emission, 500 light years away, open up a new kind of high-resolution astronomy. This will help us understand how our Sun fed off its surrounding disk of dust, eventually forming the planets and, ultimately, how life on Earth was possible…

Source: ESO

Posted on by Ian O'Neill

Astrophysicist’s South Pole Death Remains a Mystery After Eight Years

Rodney Marks (1997-1998 winterover) with the SPIREX telescope (D. A. Harper)

[/caption]In May 2000, Australian astrophysicist Dr Rodney David Marks died from acute methanol poisoning whilst stationed at the US Amundsen-Scott South Pole Station. He was a 32 year old “brilliant and witty” scientist, whose death shocked his family and friends. The media jumped on this story, citing the tragedy as the “first South Pole murder,” but there was little evidence to suggest anyone else was involved. Unfortunately it appears that New Zealand investigators have been hampered by a lack of co-operation by the organizations that run the facility, so it remains unclear whether Marks’ death was the result of foul play or tragic accident…

Dr Marks was employed by the Smithsonian Astrophysical Observatory, working on the Antarctic Submillimetre Telescope and Remote Observatory project. The Amundsen-Scott South Pole Station (pictured below) is maintained by the US National Science Foundation (NSF) and US contractor Raytheon Polar Services, and is the southernmost continually inhabited settlement on Earth. With this exotic location comes a high degree of risk; after all, if there’s an accident or emergency, you can’t just find the nearest hospital. Although the facility has good medical support, should something unexpected happen, the scientists living right on top of the South Pole are at the mercy of the extreme weather and isolated location.

Aerial view the South Pole, including the Amundsen-Scott South Pole Station (NOAA)
Aerial view the South Pole, including the Amundsen-Scott South Pole Station (NOAA)

In the month of May 2000, medical staff at Amundsen-Scott were confronted with a baffling problem when a distressed Rodney Marks came to them three times during a 36 hour period. On May 11th, he had felt sick and vomited blood when travelling back from the remote observatory to base. On returning, his condition took a rapid turn for the worse. Baffled by the situation, medical staff sought advice via satellite, but they were too late. On May 12th, the astrophysicist had died.

For six months, officials had to wait until Marks’ body could be flown to New Zealand for an autopsy where it was found that the 32 year old had suffered from acute methanol poisoning. As New Zealand has jurisdiction over the incident, investigators from the nation took on the task of working out how Marks could have become poisoned.

According to a recent article in the New Zealand Herald, the investigators may never get to the bottom of this Antarctic mystery. On September 24th, coroner Richard McElrea released his findings behind the death of Dr Marks, airing his frustrations that the police investigation had been hampered by the lack of co-operation by the NSF and Raytheon Polar Services.

The police officer assigned to investigating the case, Detective Grant Wormald, even remarked, “Despite numerous requests, I am not entirely satisfied that all relevant information and reports have been disclosed to the New Zealand police or the coroner.” Dr Marks’ family have also been disappointed by the lack of communication they have received by the organizations responsible for the safety of their researchers.

“And I don’t think we are going to try to find out any more in regards to how Rodney died. I’d see that as a fruitless exercise […] For heaven’s sake, a man has died in your care. Why wouldn’t you help the police? .” – Paul Marks, Dr Marks’ father.

Originally, suicide was thought to be at the root of this mystery, but it was quickly ruled out as it didn’t fit with Dr Marks’ profile. He was a happy scientist who was engaged to Sonja Wolter, a young maintenance specialist, who had signed up to the station to be with her fiancé. According to the Detective Wormald, “Sonja and Rodney were a great couple. It is so rare to see people that seem so perfectly matched. And they were extremely happy together.”

It was also suggested that Marks may have consumed the methanol deliberately, to get a “recreational high,” even though there was a plentiful supply of genuine liquor and beer at the facility. Dr Marks was a social young man who “always said was that the solution to any problem is to go down to the pub and have a few drinks,” according to one of his friends, Andrew Walsh. Even though he may have enjoyed a few drinks and could be considered to be a binge drinker, it is strange to think he would willingly consume the dangerous substance for fun.

There are some sinister overtones to this mystery however. According to a 1996 report, Dr Robert Thompson, the first doctor to examine Marks when he came to the medical facility for help, said the astrophysicist was “nervous, anxious and upset.” What’s more, he noted two needle marks on his arm, but decided not to ask about them.

Had Marks been murdered by one of the 49 members of staff at the Amundsen-Scott South Pole Station? Unfortunately, we may never know whether Marks’ death was deliberate or by accident. According to the US agencies, an investigation had been carried out, but Detective Wormald has not been privy to the conclusions. “It is impossible to say how far that investigation went or to what end,” he said.

The Herald reporter apparently approached Raytheon, but the company would not comment and an NSF spokesman referred any questions to the NSF offices in Washington DC.

It looks like everyone is remaining tight-lipped about the events on May 11th-12th 2000, ensuring the world may never get to the cause behind the tragic death of this talented and friendly astrophysicist.

Sources: NZ Herald, Ohmynews.com, Wikipedia

Posted on by Nancy Atkinson

The Cepheids Aren’t Falling

Cepheid variable stars have been used for years as a way to determine distance to other galaxies. The correlation between their period of variability and absolute luminosity provides a cosmic yardstick to measure distances out to a few tens of millions of light-years. Additionally, Cepheids closer to home are used as tools to investigate how the Milky Way spins. But the motion of the Cepheids in our galaxy has confused astronomers, as these neighborhood Cepheids appear to fall towards the sun. A debate has raged for decades as to whether this phenomenon was truly related to the actual motion of the Cepheids and, consequently, to a complicated rotating pattern of our galaxy, or if it was the result of effects within the atmospheres of the Cepheids. But new observations with the HARPS (High Accuracy Radio Velocity Planet Searcher) spectograph shows that the Cepheids aren’t falling, and that the much debated, apparent ‘fall’ does in fact stem from properties of the atmospheres around these variable stars.

“The motion of Milky Way Cepheids is confusing and has led to disagreement among researchers,” says astrophysicist Nicolas Nardetto. “If the rotation of the Galaxy is taken into account, the Cepheids appear to ‘fall’ towards the Sun with a mean velocity of about 2 km/s.”

Nardetto and his colleagues observed eight Cepheids with the high precision HARPS spectrograph, attached to the 3.6-m ESO telescope at La Silla, 2400 m up in the mountains of the Chilean Atacama Desert. HARPS, or the High Accuracy Radial Velocity Planetary Searcher, is best known as a very successful planet hunter, but it can also be used to resolve other complicated cases, where its ability to determine radial velocities – the speed with which something is moving towards or away from us – with phenomenally high accuracy is invaluable. “Our observations show that this apparent motion towards us almost certainly stems from an intrinsic property of Cepheids,” says Nardetto.

The astronomers found that the deviations in the measured velocity of Cepheids were linked to the chemical elements in the atmospheres of the Cepheids considered. “This result, if generalized to all Cepheids, implies that the rotation of the Milky Way is simpler than previously thought, and is certainly symmetrical about an axis,” concludes Nardetto.

Source: ESO

Posted on by Tammy Plotner

Australian Telescope Leads the World In Astronomy Research

The AAT - Photograph courtesy of Chris McCowage

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While the Anglo-Australian Telescope is far from being the world’s largest, or even located in the world’s best observing site, it’s still the world’s most productive in terms of astronomy research. According to recently released productivity ratings, the number of scientific papers resulting from observations made with the AAOmega fibre-fed optical spectrograph, SPIRAL Integral Field Unit, IRIS2, University College London Echelle Spectrograph (UCLES), or Ultra High Resolution Facility (UHRF) made the AAT the number one ranked 4-metre-class telescope in the world for more than two years between 2001 and 2003. But what’s going on today is even more important…

When we think of research telescopes, some of the world’s top rated are the Hubble Space Telescope (located in Earth orbit), Keck (more than twice the AAT’s size) in Hawaii, the Very Large Telescope (VLT, which comprises four telescopes twice the size of the AAT) in Chile, the Sloan Digital Sky Survey and the 2MASS telescope. So where does that leave the humble Anglo-Australian? Try number five. “The AAT has a remarkable track record of scientific productivity and impact,” says Prof. Matthew Colless, Director of the Anglo-Australian Observatory. “This is an extraordinary achievement.”

When the Anglo-Australian Observatory opened for business in the early 1970’s, the 4 meter telescope was the standard by which all others were judged. Since that time, research telescope aperture has more than doubled and while the AAT can’t compete in some respects, it has advantages that give it an edge for research. While it isn’t Mauna Kea, Australia still offers up some of the best skies to study our Galaxy and other nearby galaxies and the ability to undertake long-term observations and programs that just won’t work with other observatories. Add to that some very unique instrumentation such as Echidna – a fibre positioner for FMOS, UKidna – A multi-fibre positioner for the UKST, OZPOZ – a fibre positioner for ESO and part of FLAMES, DAZLE – The Dark Age z (redshift) Lyman-alpha Explorer, MOMFOS – Multi-Object Multi-Fibre Optical Spectrograph, ODC – Optical Detector Controllers and AAOmega – next generation optical spectrograph for the AAT and you have a recipe for research. This explains why demand for the telescope remains strong, with 2.5 times as many applications for telescope time as can actually be handled. “The AAO believes that the AAT can maintain this high level of productivity and impact for another decade.” says Prof. Colless.

Over a period of time, the the AAO has produced some of the most inspiring astronomy images ever seen – those taken by David Malin. These are the most extraordinary wide-field astrophotographs made with professional telescopes anywhere and every effort has been made to capture the true colours of distant stars, galaxies and nebulae using innovative photographic techniques and CCD detectors. The images have detailed captions and the full NGC 2000.0 catalogue entry. Galaxy images also carry NASA/IPAC Extragalactic Database (NED) data links. They are a standard of astronomers everywhere. But, progress hasn’t stopped. The AAT’s prime focus has recently been upgraded to accommodate a new generation of highly sensitive CCD detectors. The first colour images made with the new facility are now available, currently only in digital form. Most of the photographic images have recently been digitally re-mastered from the original 3-colour separations. This has allowed the AAO to create new, high resolution versions of many existing images and some new pictures that could not be made photographically.

Just this year a “uniquely ambitious, far-sighted” project won an Australian and UK astronomy team the first Group Achievement Award from the UK’s Royal Astronomical Society. Led by Professor Matthew Colless (Anglo-Australian Observatory) in Australia and Professor John Peacock (University of Edinburgh) in the UK, the thirty-three-member team spent ten years mapping the distribution in space of 220,000 galaxies using the 3.9-m Anglo-Australian Telescope (AAT) in New South Wales — a project called the 2-degree Field Galaxy Redshift Survey (2dFGRS). “The scale of this project made it ground-breaking,” said Matthew Colless. “For the first time we were able to map the positions of a huge number of galaxies and see the subtle effects that reveal the different types of matter in the universe.”

What was needed was for the area of sky surveyed to be much bigger than, rather than the same size as, the “walls” and “strings” of galaxies being detected. Almost ten times larger than any previous survey, the 2dFGRS was the first study to meet this crucial condition. The survey measured patterns in the distribution of galaxies, on scales from 100 million to 1 billion light-years. Two wedge-shaped pieces of sky were surveyed, so when the galaxies within them were mapped out, the result looked like a bow-tie cut from a sponge: a network of voids and dense regions. The size of the 2dF Galaxy Redshift Survey was made possible only by technological advances developed at the Anglo-Australian Observatory (AAO). The 2dF spectrograph used robotic technology to place optical fibres onto the telescope’s focal plane, where each fibre could collect the light from a single galaxy. By using up to 400 optical fibres, this system allowed the light from up to 400 galaxies to be captured simultaneously.

And the AAT is ensuring that it doesn’t fall behind the times with future technological advancement either….

“We are currently investing $4 million in refurbishing the telescope to ensure that it can operate reliably and efficiently for another ten years, and more than $6 million in a major new instrument, the 400-fibre HERMES high-resolution Spectrograph,” says Prof. Colless. “The primary science drivers for HERMES are ‘Galactic archaeology’ surveys to uncover the formation history of the Milky Way,’ he adds. ‘Extragalactic surveys using the AAOmega instrument and galactic surveys using HERMES will be the flagship science carried out on the AAT over the next 5-10 years. AAOmega and HERMES, and other upgrades to existing instruments, will provide astronomers with powerful tools that will enable them to do competitive, high-impact research using the AAT throughout the coming decade.”

Original Source: SpaceInfo.com

Posted on by Nancy Atkinson

‘Laser Comb’ To Measure the Accelerating Universe

Back in April, UT published an article about using a device called a ‘laser comb’ to search for Earth-like planets. But astronomers also hope to use the device to search for dark energy in an ambitious project that would measure the velocities of distant galaxies and quasars over a 20-year period. This would let astronomers test Einstein’s theory of general relativity and the nature of the mysterious dark energy. The device uses femto-second (one millionth of one billionth of a second) pulses of laser light coupled with an atomic clock to provide a precise standard for measuring wavelengths of light. Also known as an “astro-comb,” these devices should give astronomers the ability to use the Doppler shift method with incredible precision to measure spectral lines of starlight up to 60 times greater than any current high-tech method. Astronomers have been testing the device, and hope to use one in conjunction with the new Extremely Large Telescope which is being designed by ESO, the European Southern Observatory.

Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colors, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colors rather than distances, with an extremely accurate and fine grid.

New, extremely precise spectrographs will be needed in experiments planned for the future Extremely Large Telescope.

“We’ll need something beyond what current technology can offer, and that’s where the laser frequency comb comes in. It is worth recalling that the kind of precision required, 1 cm/s, corresponds, on the focal plane of a typical high-resolution spectrograph, to a shift of a few tenths of a nanometre, that is, the size of some molecules,” explains PhD student and team member Constanza Araujo-Hauck from ESO.

The new calibration technique comes from the combination of astronomy and quantum optics, in a collaboration between researchers at ESO and the Max Planck Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a ‘frequency comb’ – light at many frequencies separated by a constant interval – to create just the kind of precise ‘ruler’ needed to calibrate a spectrograph.

The device has been tested on a solar telescope, a new version of the system is now being built for the HARPS planet-finder instrument on ESO’s 3.6-metre telescope at La Silla in Chile, before being considered for future generations of instruments.

More information on laser combs.

Source: ESO

Posted on by Nancy Atkinson

New Eye to the Universe Under Construction

The LSST, or the Large Synoptic Survey Telescope is a large survey telescope being constructed in northern Chile. When operational in 2015, it will be the widest, fastest, deepest eye of the new digital age, providing timelapse digital imaging across the entire night sky every three days, mapping the structure of our dynamic universe in three dimensions and exploring the nature of dark matter and dark energy. LSST hit a major milestone in its construction when the primary mirror blank was recently created. Project astronomers say the single-piece primary and tertiary mirror blank cast for the LSST is “perfect.”

The 51,900 pound (23,540 kg) mirror blank was fired in the oven at the University of Arizona’s Steward Observatory Mirror lab in Tucson, Arizona. It consists of an outer 27.5-foot diameter (8.4-meter) primary mirror and an inner 16.5-foot (5-meter) third mirror cast in one mold. It is the first time a combined primary and tertiary mirror has been produced on such a large scale.

LSST will have three large mirrors to give crisp images over a the largest field of view that will be available. The two largest of these mirrors are concentric and fit neatly onto a single mirror blank.
LSST was recently the recipient of two large gifts: $20 million from the Charles Simonyi Fund for Arts and Sciences, and $10 million from Bill Gates. The finished mirror is scheduled to be delivered in 2012.

More information about LSST.

News Source: LSST press release