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In the News this month... and finally
Astronauts Michael Good (left) and Mike Massimino, both STS-125 mission specialists, participate in the missions fourth session of extravehicular activity (EVA) as work continues to refurbish and upgrade the Hubble Space Telescope. During the eight-hour, two-minute spacewalk, Massimino and Good continued repairs and improvements to the Space Telescope Imaging Spectrograph (STIS) that will extend the Hubbles life into the next decade. CREDIT:
May was a busy month in space with the successful launch of two space telescopes and a servicing mission to Hubble. On the 11th of May, the space shuttle Atlantis took off on the fifth and final flight
to service the Hubble Space Telescope
. During the 13-day flight, the crew carried out five spacewalks totalling 36 hours and 56 minutes, successfully installed the Wide Field Camera 3 and the Cosmic Origins Spectrograph
, and repaired both the Advanced Camera for Surveys
and the Space Telescope Imaging Spectrograph
. The astronauts also replaced all six of Hubble's batteries launched with the telescope in 1990 and now losing capacity as they age. Other tasks included replacing the fine guidance sensors and all six rate sensor units - the gyroscopes essential to keep the telescope pointing in the right direction. The upgrades will hopefully allow the telescope to keep functioning until 2014 when the James Webb Space Telescope
is scheduled to launch.
Herschel and Planck launch on board an Ariane 5 CREDIT:
May 14th saw the successful launch of the Herschel
satellites, lifting off together on board an Ariane 5 rocket from the European Space Agency's launch site in French Guiana. Planck is a telescope designed to map the tiny fluctuations in the Cosmic Microwave Background in unprecedented detail, while Herschel is an infrared telescope which will study some of the coldest objects in the Universe. Once in space, the two satellites separated from each other in order to travel independently out to a point known as L2 - a gravitationally stable orbit one and a half million kilometres on the opposite side of the Earth from the Sun. Both satellites are undergoing in-flight tests and are so far functioning perfectly.
Posted by Megan on Saturday 30th May 2009 (13:56 UTC
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In the News this month... Fermi sheds light on high energy cosmic rays
The Fermi satellite CREDIT:
There has been much speculation over the cause of an excess of cosmic-ray electrons and positrons recently detected by the ATIC
experiments. Suggested sources of this excess not only include Galactic pulsars and supernova remnants, but also more exotic explanations such as dark matter annihilations. Now, new results from the Large Area Telescope, or LAT, on board the Fermi satellite
have added new information to the puzzle.
Models of cosmic ray electrons and positrons interacting with the interstellar medium predict a featureless distribution in the number of particles with energies between 10 and a few hundred giga electron volts
. However, last year the European satellite PAMELA detected surprisingly large quantities of high-energy positrons, while the balloon-borne ATIC experiment found a significant peak in the total electron plus positron count at high energies. Like ATIC, the LAT on Fermi is sensitive to the total electron plus positron flux. The new results from Fermi, published in the journal Physical Review Letters
on the 4th of May, do show a larger number of particles with energies of around 500 giga electron volts, but the excess is no where near as large as that measured by the ATIC experiment. The new results are, however, consistent with the excess of positrons seen by PAMELA.
While these Fermi observations are the most precise yet at these energies, they are still not enough to either confirm or rule out a particular origin for these high energy particles. The LAT team are planning further observations to reduce the uncertainties and hopefully determine whether the particles are caused by dark matter annihilations or known local sources of electrons such as pulsars and supernova remnants.
Posted by Megan on Saturday 30th May 2009 (13:21 UTC
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In the News this month... the puzzle of crystalline silicates in comets
The image shows a young sun-like star encircled by its planet-forming disk of gas and dust. The silicate that makes up most of the dust would have begun as non-crystallized, amorphous particles. CREDIT:
Models of solar system formation
show that comets form at large distances from their parent star. This makes sense as they are made up largely of frozen material, but a long-standing mystery is how they end up containing tiny silicate crystals which need very high temperatures to form. These crystals start out in an amorphous
form where their atoms are arranged randomly. At high temperatures, the atoms in these crystals become more ordered, forming what is known as a crystalline lattice
. Because they need high temperatures to form, these crystalline silicates were not expected to be found in comets, so how they come to be there is a puzzle. In the May 14th issue of Nature
, a team led by Peter Abraham of the Hungarian Academy of Sciences, published the first evidence of the formation of crystalline silicates in the disk around a young sun-like star. Together with colleagues from Leiden Observatory and the Max Planck Institute for Astronomy in Heidelberg, Abraham used the Spitzer Space Telescope
to observe the eruptive star EX Lupi in April 2008 during one of its outbursts. When they examined the spectra from these observations, the researchers discovered the infrared signature of silicate crystals in the disk of dust and gas around the star.
When they compared their results to similar spectra of EX Lupi taken between outbursts, they found that the older observatories only showed the presence of amorphous silicates rather than the crystalline form. In the newer observations taken during the star's outburst, a broad peak corresponding to amorphous silicates was present, but an additional narrow peakat a wavelength of 10 microns was also visible. This narrow feature is likely caused by the presence of forsterite
, the magnesium-rich crystalline form of the mineral olivine
The appearance of this additional feature in the spectrum during the star's outburst suggests that crystal formation was happening in the star's disk during the outburst. The researchers think that this is the first time ongoing crystal formation has been observed. They say that the crystals were probably formed on the surface layer of the star's inner disk by heat from the outburst, in a process known as thermal annealing
where a substance is heated to a temperature where some some of its bonds break and then re-form altering the material's structure and physical properties. The forsterite crystals detected are just like those found in comets in the solar system which could have been produced by similar outbursts from out own Sun when it was much younger.
Posted by Megan on Saturday 30th May 2009 (13:06 UTC
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In the News this month... evidence for the origins of millisecond pulsars
Artists impression of a neutron star with accretion disk (left) drawing material from companion star (right). CREDIT:
Bill Saxton, NRAO/AUI/NSF
Fast-spinning radio pulsars
with millisecond rotation periods are thought to be the result of a process involving the transfer of material from a companion low-mass star onto a normal pulsar. This accretion process adds mass and angular momentum to the pulsar resulting in its rotation rate speeding up and the emission of X-rays. Using telescopes around the world, a team of astronomers has for the first time discovered evidence of this process taking place.
Pulsars are extremely dense neutron stars
, left over after massive stars explode as supernovae. They have strong magnetic fields which generate beams of light and radio waves which sweep across the sky as the pulsar spins. Most pulsars rotate a few times a second, but some, known as millisecond pulsars, rotate hundreds of times a second. Ordinary pulsars in a binary system with a low-mass companion can start to accumulate material in an accretion disk
- a flat spinning ring of material around the pulsar. While this disk exists, it is thought that the radio waves characteristic of a pulsar would be quenched and the object would not appear as a pulsar. When the rate of infalling material slows down and stops, the pulsar's emission would be able to disrupt the accretion disk, blowing material out of the system and allowing the radio emission to resume. Now, a team led by Anne Archibald at McGill University in Montreal, Canada, have found evidence of this process taking place in a binary star system 4000 light years away.
A millisecond pulsar was discovered in the system in 2007, so the team looked back through archive data from several telescopes. What they discovered was a dramatic change in the system over the last decade. Optical observations in 1999 showed a Sun-like star, while observations a year later showed evidence of an accretion disk around the neutron star. By 2002, the evidence for this disk had disappeared. The observations in 2007, made with the Green Bank Telescope
in West Virginia, found a millisecond pulsar spinning 592 times per second. The researchers say that this system appears to be the missing link between millisecond pulsars and accreting binary systems known as Low Mass X-ray Binaries
. The results were published in the journal Science
Posted by Megan on Saturday 30th May 2009 (12:27 UTC
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Interplanetary packet loss
I missed this one, but New Scientist picked it up. It seems that there was a glitch with NASA's Deep Space Network last month that resulted in the loss of data from Cassini's latest flyby of Titan. The Deep Space Network (DSN) is a collection of radio telescopes at facilities spaced approximately 120 degrees apart around the world: at Goldstone, in California's Mojave Desert; at Robledo near Madrid, Spain; and at Tidbinbilla near Canberra, Australia. They are spaced at intervals of 120-degrees so that they can provide continuous coverage when needed. Each complex consists of at least four antennas: a 70-m, two 34-m and a 26-m. As well as handling scientific data from probes, these stations are also responsible for receiving telemetry and transmitting control commands back to the spacecraft. They operate at either S-band (2.3 GHz) or X-band (8.4 GHz) and also take part in scientific observations from time to time - the 70-m Tidbinbilla antenna for example regularly takes part in Australian Long Baseline Array (LBA) observations.
Some of these antennas have been operating for a long time and are showing their age a bit. On April 20th the 70-m antenna at Goldstone was moving into position to pick up data from Cassini's flyby when it got stuck, apparently on a gouge in the circular guide rail. The problem has since been fixed (having watched track repairs on the Lovell telescope, I can imagine that this was a big job), but unfortunately that data has been lost forever.
NASA is currently refurbishing and upgrading the DSN antennas, fixing structural problems and replacing some of the electronics. One upgrade is to add receivers that operate at higher frequencies. This is to increase the data capacity of the network to accommodate not only the increasing number of spacecraft, but the increasing amount of data per mission. When the JWST begins operations in 2014, on its own it will transmit 125 Mbits/second. Higher frequencies mean higher data rates, so this will hopefully enable the network to continue operating for many years to come.
Don't forget, you can build your own DSN antenna!
Posted by Megan on Sunday 17th May 2009 (14:20 UTC
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Australian SKA developments
Late yesterday the Australian Federal government announced a $160.5 million investment plan in astronomy and space science. It's budget time here in Australia, so there is a lot of discussion about large funding plans and national debt. In a $22 billion Nation Building Infrastructure plan, funding has been promised for roads, metro rail, ports, the Clean Energy Initiative, universities, research, hospitals and broadband. In total, more than $900 million has been set aside for funding science infrastructure around the country.
Announced by the Innovation Minister, Kim Carr, this funding is part of the Federal Government's Super Science Initiative and will fund a diverse range of projects such as upgrading the Australian National University's Climate High Performing Computing facilities, replacing CSIRO's Marine National Facility, and building a new Australian National Centre of SKA Science right here in Perth.
Western Australia is one of two potential sites for the Square Kilometre Array (SKA), the next generation radio telescope under development by a large international collaborations of astronomers, engineers and industry partners. The telescope is being designed to help answer some of the fundamental "big" questions about our Universe and its evolution and will require immensely powerful computing facilities to process the enormous amount of data which the telescope will collect. The decision on whether the SKA will be located either in WA or South Africa is likely to be made sometime in 2011/12, but Australia is already building the Australian SKA Pathfinder (ASKAP) radio telescope at the heart of the candidate site in the Murchison. ASKAP will be a demonstrator telescope testing some of the new technologies which the SKA will require and will amass more information in the first six hours of operation than has been recorded by all the world's radio telescopes to date.
While this is very exciting for Australian astronomy, and Perth in particular, it is not the only bit of good astronomy-specific news to come out of the budget. Also in the pipeline are:
- $20.9 million for Australia to take sole responsibility for the Anglo-Australian Observatory, home of the world's top ranked four-metre optical telescope;
- $10.0 million to construct state-of-the-art instruments and data acquisition infrastructure to store, process and analyse information captured from different next-generation telescopes;
- $40.0 million for a new Australian Space Research Program to support space research, innovation and skills development in areas of national significance; and
- $8.6 million to establish a Space Policy Unit, which will provide whole-of-Government advice on space and industry development.
All in all, a pretty positive day for Australian astronomy, and how this all develops over the next few months will certainly be interesting to watch.
Posted by Megan on Wednesday 13th May 2009 (03:30 UTC
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We really do have the technology!
Technologically speaking, there's a huge amount going on in astronomy right now. The space shuttle Atlantis is due to launch on May 11th on the fifth and final servicing mission to the Hubble Space Telescope, ESA will launch not one but two telescopes, Planck and Herchel, abord an Ariane 5 on Thursday 14 May, and the first fringes have been detected between two completed ALMA antennas high in the Atacama desert.
The two ALMA antennas used in the project's successful test observation of "first astronomical fringes", at the Operations Support Facility at an altitude of 2900 metres. CREDIT:
First up, ALMA. The Atacama Large Millimetre Array
(ALMA) is going to be one impressive telescope when it is complete (not quite as good as the SKA of course, but I'm sure you've worked out that my opinion is slightly biased here!). The finished instrument will consist of more than 60 individual dishes spread out across the Atacama desert high in the Chilean Andes where the atmosphere is incredibly dry. ALMA is an interferometer like MERLIN
, the VLA
, but it will operate in the millimetre and submillimetre regimes at much higher frequencies. So what? Well, this will be great for astrochemistry - there are huge numbers of spectral lines from all sorts of different molecules which are in this region of the spectrum, so ALMA will help our understanding of star formation and galaxy evolution by providing a detailed spatial and spectral view of the mm/sub-mm sky. Telescopes are under construction at the moment and some have recently been delivered to the site. First fringes
(for an interferometer, this is the equivalent of first light) were obtained on 30th April between two of the 12-m antennas which have been constructed at the ALMA Operations Support Facility (OSF), high in Chile’s Atacama region, at an altitude of 2900 metres. This is an important milesone in the construction of the array - it is the first time that antennas and the other systems required to record data have been joined together to make an observation. "We're very proud and excited to have made this crucial observation, as it proves that the various hardware components work smoothly together. This brings us another step closer to full operations for ALMA as an astronomical observatory
," says Wolfgang Wild, the European ALMA Project Manager. The two dishes were pointed at Mars for the test observation, an object in the sky which is bright in the sub-mm and is a useful calibrator. The final telescopes will be situated at an altitude of 5000 metres where the atmosphere is thinner and drier, so there is very little of the atmospheric water vapour which causes huge problems in this part of the spectrum. “We are on target to do the first interferometry tests at the 5000-metre high-altitude site by the end of this year, and by the end of 2011 we plan to have at least 16 antennas working together as a single giant telescope
,” said Thijs de Graauw, ALMA Director.
The Hubble Space Telescope CREDIT:
Next on the horizon is the launch of Atlantis on the fifth and final Hubble servicing mission
. On 11th May, the shuttle will launch with a crew of seven to carry out the replacement and repair of several instruments which will (hopefully) see the telescope continue to function for several more years. Launched in 1990, the telescope has been used by many astronomers, helped make numerous ground-breaking discoveries and produced some of the most well-known astronomical images of the last two decades. Astronauts from both NASA
have visited Hubble
in 1993, 1997, 1999 and 2002 to carry out maintenance and repairs, most recently replacing the Faint Object Camera with the Advanced Camera for Surveys, fixing NICMOS, and replacing the solar panels. Following the loss of Columbia in 2003, plans for a fifth servicing mission were cancelled, but later reinstated. Originally scheduled to fly in September 2008, the mission was again postponed to allow the replacement of another critical system which had failed. The primary objective of the mission is to deliver two new instruments: the Cosmic Origins Spectrograph (COS) will sit in the slot currently occupied by the now redundant Corrective Optics Space Telescope Axial Replacement (COSTAR) package, and the enhanced Wide Field Camera 3 (WFC3) will replace the current Wide Field Planetary Camera 2 (WFPC2). After this mission, every major component on the spacecraft, apart from the mirrors, will have undergone at least one upgrade since Hubble's launch. With any luck, the upgrades will allow the telescope to continue functioning through to at least 2013.
Artists impression of the Herschel and Planck satellites CREDIT:
Last, but not least, is the upcoming launch
of not one but two telescopes by ESA. Scheduled for 13:12 GMT
on May 14th, Planck and Herschel will lift off together on an Ariane 5 from ESA's launch site in French Guiana. Herschel
is a large far-infrared space telescope designed to study some of the coldest objects in space, in a part of the electromagnetic spectrum still mostly unexplored. Its mirror is almost 1.5 times larger than Hubble's and six times larger than that of its predecessor, ISO. Planck
, on the other hand, is a microwave telescope that will map the fossil light of the Universe - light from the Big Bang - with unprecedented sensitivity and accuracy. It is designed to map the tiny fluctuations in the CMB previously mapped by COBE and WMAP in much greater detail. The two satellites will launch together and then separate once in space to travel independently out to a point known as L2, a gravitationally stable orbit 1.5 million kilometres on the opposite side of the Earth from the Sun.
All in all (despite the problems of the STFC), it's an exciting time for astronomy.
Posted by Megan on Thursday 07th May 2009 (14:02 UTC
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In the News this month... and finally
Artists impression of the Gliese 581 system. Gliese 581 e (foreground) is only about twice the mass of our Earth. The Gliese 581 planetary system now has four known planets, with masses of about 1.9 (planet e, left in the foreground), 16 (planet b, nearest to the star), 5 (planet c, centre), and 7 Earth-masses (planet d, with the bluish colour). The planet furthest out, Gliese 581 d, orbits its host star in 66.8 days, while Gliese 581 e completes its orbit in 3.15 days. CREDIT:
The discovery of the lightest exoplanet found so far was announced at the Joint European and National Astronomy Meeting
at the University of Hertfordshire on the 21st of April. This is the fourth planet discovered in the Gliese 581 system
, orbiting a star located 20.5 light years away in the constellation Libra. The planet, known as Gliese 581 e
, has a mass just 1.9 times that of Earth and orbits its parent star in just 3.15 days. The team, led by Michel Mayor of Geneva Observatory, have been searching for planets
using the HARPS spectrograph
on ESO's 3.6-metre telescope at La Silla in Chile for more than four years.
By refining the orbit of the planet Gliese 581 d, first discovered in 2007, a team of astronomers has shown that it lies well within the habitable zone, where liquid water oceans could exist. This diagram shows the distances of the planets in the Solar System (upper row) and in the Gliese 581 system (lower row), from their respective stars (left). The habitable zone is indicated as the blue area, showing that Gliese 581 d is located inside the habitable zone around its low-mass red star. CREDIT:
The same study found that one of their previous planetary discoveries is located within the habitable zone of Gliese 581, a low mass red dwarf star. While the mass of this planet means it is unlikely to be a rocky, Earth-like planet, its location in the habitable zone means there could be liquid water on its surface. The results of the study have been submitted for publication in the journal Astronomy and Astrophysics
Posted by Megan on Saturday 02nd May 2009 (04:05 UTC
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In the News this month... how asteroids get a sun tan
When two asteroids collide, they create a family of fragments with newly exposed surfaces. As these fragments age, they become redder in colour, but the actual process, and the timescales over which they act, have been heavily debated. A team of researchers, led by Pierre Vernazza of the European Space Agency, have observed asteroids from different groups with various ages and compositions, and concluded that the ageing process is far more rapid than thought. The research, published in Nature (PDF) during April, not only shows that asteroid surfaces age and redden in less than one million years, but that the solar wind is the most likely cause of this weathering.
Artist’s impression of how the solar wind makes young asteroids look old. After undergoing a catastrophic collision, the colour of an asteroid gets modified rapidly by the solar wind so that it resembles the mean colour of extremely old asteroids. After the first million years, the surface “tans” much more slowly. At that stage, the colour depends more on composition than on age. CREDIT:
While human skin is damaged over time by repeated exposure to the Sun's ultraviolet light, it is the highly energetic particles in the solar wind which damages the outer layers of an asteroid, destroying the molecules and crystals on the surface and forming a thin crust of material with distinctive properties. By studying different families of asteroids
, the team found that the composition of an asteroid is an important factor in determining how red its surface becomes. After the initial rapid reddening during the first million years, the surface ages more slowly with the colour determined more by composition than by age.
Their research also showed that collisions alone cannot account for the high proportion of fresh-looking surfaces seen on near-Earth asteroids: roughly 10% of 1-km size near Earth objects appear to have unreddened surfaces. Instead, they suggest that these may be the result of planetary encounters where tidal shaking could expose fresh, unaltered material. The authors point out that, if this is the case, then a comparison of the colours of near-Earth asteroids with similar asteroids in the main asteroid belt should show a greater abundance of redder objects away from the Earth in the main belt.
Posted by Megan on Saturday 02nd May 2009 (03:55 UTC
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In the News this month... complex organic molecules spotted near the galactic centre
Astronomers using a telescope in Spain have detected two of the most complex molecules ever found in interstellar space in a region known as Sagittarius B2, close to the Galactic centre. While hydrogen accounts for approximately three quarters of the visible matter in the Universe, many heavier elements are also present. Under the right conditions, these elements can form bonds creating a variety of different molecules. Like atoms, molecules emit electromagnetic radiation at very specific frequencies, resulting in a characteristic fingerprint of lines in the spectrum of an astronomical object. Detecting complex molecules in space involves searching for these fingerprints and trying to disentangle overlapping lines from different molecules. So far, more than 150 different molecules have been detected either in the interstellar medium or around stars. These include various organic molecules, those containing carbon atoms, although those found to date are much simpler than the amino acids which are the building blocks of all life here on Earth. Astronomers studying the chemistry of the Sagittarius B2 region have previously found numerous different large molecules including alcohols, aldehydes and acids. The cloud itself is a hot, dense ball of gas around a luminous young star in a known star forming region located approximately 100 parsecs from the Galactic centre.
Two new highly complex organic molecules detected in space. Left: Ethyl formate (C2
OCHO), Right: n-Propyl cyanide (C3
CN). Colour code of the atomic constituents of both molecules: hydrogen (H): white, carbon (C): grey, oxygen (O): red and nitrogen (N): blue. CREDIT:
Oliver Baum, University of Cologne
The new study, led by Arnaud Belloche at the Max Planck Institute for Radio Astronomy
in Germany and published in the journal Astronomy and Astrophysics, used the IRAM 30m telescope
on Pico Veleta in Spain to obtain sensitive spectra of the region. When the team analysed their data, they discovered the spectral signatures of ethyl formate and n-propyl cyanide, two of the most complex molecules discovered in space so far. Some chemicals form by the collision of particles in a gas cloud, but astrochemical models suggest that more complex molecules form on small dust grains from individual atoms and simple molecules reacting together. Larger, more complex molecules are then formed by the addition of further simple molecules to the chain.
While the simplest amino acids, glycine, has not yet been detected in space, its size and complexity is similar to ethyl formate and n-propyl cyanide, suggesting that future surveys with more sensitive instruments could detect amino acids.
Posted by Megan on Saturday 02nd May 2009 (03:41 UTC
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In the News this month... Mystery object spotted at the dawn of galaxy formation
The Lyman alpha blob known as Himiko CREDIT:
M. Ouchi et al.
A team of astronomers have discovered
a mysterious object in the early universe
which could be one of the earliest ancestors of a forming galaxy ever detected. The object is almost 13 billion light years away when the Universe was only 6% of its current age, and is a type of object known as a +>Lyman alpha emitter.
As the Universe expanded after the Big Bang, it slowly cooled, eventually allowing gas to form as the protons and electrons in the hot primordial plasma combined to form hydrogen atoms. Galaxies started to form when this neutral, opaque gas began to collapse under gravity, forming stars which ionised the surrounding gas making the Universe transparent in what is known as the Epoch of Reionisation. This occurred between about 150 million and one billion years after the Big Bang.
This mysterious object, dubbed "Himiko" by its discoverers, is a giant blob of hydrogen gas 55 thousand light years across, roughly the radius of the Milky Way, and formed when the Universe was a mere 800 million years old. Finding such a large object so far back in time was unexpected since it is thought that small objects formed first and then merged to create larger objects over time. Named after particular spectral signature of hydrogen, many smaller examples of these Lyman alpha emitters are known, although most exist at a time when the Universe was between two and three billion years old.
This image shows the spectrum of the Himiko object. The top panel shows the two dimensional view of the Keck/DEIMOS data, while the bottom shows the same data in one dimension. CREDIT:
M. Ouchi et al.
Himiko is unique in other ways too. It is both the brightest and largest Lyman alpha object yet discovered. Its character is something of a mystery however. In a paper accepted for publication in the Astrophysical Journal, the authors make several suggestions based on their observations so far, including gas ionised by a hidden supermassive black hole, clouds of ionised hydrogen in very early galaxy, gas falling onto a massive dark halo object generating a massive starburst, a merger of giant gas clouds, or outflowing gas from a starburst or merger. With the data available, it is not clear which of these suggestions is correct, but the researchers point out that observations with the Atacama Large Millimetre Array
when it is complete should narrow down the possibilities by characterising the dust and molecular gas properties of the object.
Posted by Megan on Saturday 02nd May 2009 (03:19 UTC
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