31st October, 2005: Lord of the Fringes

On the 31st of July astronomers used a technique called Very Long Baseline Interferometry (VLBI) to observe and combine the received signals from radio telescopes in north-west New South Wales of Australia and the North island of New Zealand. In VLBI, the longest distance between any two telescopes defines the maximum resolution possible - the longer the distance, the higher the resolution. However, combining the signals from the telescopes is no easy feat as it requires processing huge amounts of data to search for and time a very weak underlying signal - this process is known as correlation. Adam Deller, a PhD student at Swinburne University, wrote some clever software to perform the correlation on the Swinburne University Supercomputer. His software found the radio emission from a quasar 4.5 billion light-years from the Earth with a timing accuracy of 5 billionths of a second!

The experiment with New Zealand is one of the first steps toward participating in one of the largest radio astronomy projects ever - the Square Kilometre Array (SKA). The project includes the possibility of over 100 large radio telescopes being hosted in Australia and across the Tasman in New Zealand.

This collaboration took place between CSIRO's Australia Telescope National Facility (ATNF), the Auckland University of Technology (AUT) and Swinburne University of Technology. It is a glowing example of how the results of collaboration can be far greater than then sum of the individual efforts - congratulations to all those involved!

First "light" from the Australia - New Zealand VLBI experiment, it is an image of the quasar 1921-293 at a distance of approximately 4.5 billion light years. The radio emission is caused by matter flung away from a supermassive black hole speeds approaching the speed of light.

Image Credit: Swinburne University of Technology, CSIRO and AUT.

24th October, 2005: Andromeda in the Red

Andromeda, otherwise known to astronomers as Messier 31 or M31 for short, is the nearest spiral galaxy to our own Milky Way at a distance of about 2.5 million light-years. Its proximity makes it a brilliant specimen from which to learn more about spiral galaxies. In fact, what we learn can at times be almost embarrassing, for example, recently it was discovered that M31 is in fact three times larger than previously thought! So in continuing with the learning process astronomers recently pointed the Spizter telescope towards M31 to see what they could learn from its infrared light. Now when I say point I should be a bit more specific as M31 is pretty big - visually it is about six moon diameters in length. So in order for Spitzer to be able to capture the entire galaxy with its multi-band imaging photometers 24-micro detector it had to record about 11,000 separate snapshots over a period of 18 hours. The end result unveiled M31 in unprecedented levels of detail (see below).

The Spitzer infrared view of Andromeda revealed features not previously observed such as bright aging stars in its nuclear bulge, a spiral arc in the centre of the galaxy, an off-centred ring of star formation and a hole in the galaxy's spiral disk of arms. It is believed that these asymmetric features are as a result of interactions with several satellite galaxies that surround M31. As a smaller galaxy passed through Andromeda it punched a hole through its disk and set off a ripple of star formation. This is but a taste of what is to come, in a few billion years time M31 is expected to collide with our very own Milky Way and it will surely be quite a show - stay tuned for my news report on this event! :-)

A Spizter Space Telescope image of Andromeda.

Image Credit: NASA/JPL-Caltech/K. Gordon (University of Arizona)

17th October, 2005: Solar System plus One and a Bit

Further observations of Xena and Gabrielle with the Hubble Space Telescope are planned for in November and December of this year. It is hoped that these observations will help pin down an exact orbit for the moon and so enable a more accurate determination of its mass. Neither Xena or Gabrielle have been officially named as yet and the status of Xena as a planet is still up in the air. Some believe that the discovery of the moon will give added weight towards recognising Xena as a planet. However, it may also put into question Pluto's status as a planet - either way it is sure to fuel some debate as technical, historical and public views come into the fray. Technically speaking both Pluto and Xena are Kuiper Belt Objects but seventy-plus years of public perception and history may make it difficult to strip the "Planetary" title away from Pluto. Stay tuned to see what decision the International Astronomical Union (IAU) makes with regards to what a planet really is - I'm sure glad I'm not on that panel! :-)

Keck Observatory image showing the so-called tenth planet 2003 UB313 (nicknamed Xena) and its newly discovered moon (nicknamed Gabrielle).

Image Credit: W.M. Keck Observatory

10th October, 2005: Cool Views of the Sun

The image below of sunspot AT 10810 was made by combining 80 individual photographs taken over a period of 3 seconds. The high-resolution images available with the Dunn telescope allow astronomers to observe fine features such as the dark cores of the penumbral fibrils and the bright penumbral grains in the sunspot penumbra (the fluted structures that radiate outward from the spot). It is hoped that the study of these features can provide some insight into the magnetic structure of the sunspots which even today remains a bit of a mystery.

High resolution image of a sunspot imaged with the Dunn Solar Telescope - the image of the Earth is shown for scale. The left half of the image demonstrates normal seeing conditions and the image on the right shows the image taken with adaptive optics to compensate for atmospheric turbulence.

Image Credit: Friedrich Woeger, KIS, and Chris Berst and Mark Komsa, NSO/AURA/NSF

3rd October, 2005: The Bouncing Baby Boomer Galaxy

The galaxy is observed at a time when the Universe was only about 800 million years old. It is so distant that the blue end of its spectrum has been almost totally absorbed as light from the galaxy passes through billions of light years of intervening hydrogen gas. The galaxy could only be observed by Hubble when viewed with its near-infrared camera but even at these wavelengths it is very faint. The Spitzer Space Telescope however is capable of viewing wavelengths that are five to fifteen times longer than those of Hubble. When astronomers gazed at the galaxy with Spitzer they were surprised to find that it was quite bright at these longer infrared wavelengths. This suggests that the galaxy is not only quite massive but also mostly composed of older, redder stars.

Most cosmologists believe that galaxies in the early Universe were built up in a piece-wise manner through mergers with other smaller galaxies, a process that continues today. Yet the newly discovered galaxy is too old and massive to have formed through this process at such an early stage of the Universe. Alternatively, this galaxy may be proof that at least some galaxies form in their entirety in a process described by older theories of monolithic galaxy formation. In such theories a galaxy may form through the collapse of a VERY massive cloud of gas in a tremendously explosive burst of star formation.

This early stage of the Universe is still poorly understood but it is hoped that the James Webb Space Telescope (JWST) will help shed some light on the problem. Planned for launch in 2013, the JWST will be able to probe the early Universe with its highly sensitive infrared instruments.

A distant and surprisingly massive galaxy discovered using the combined capabilities of the Hubble and Spitzer space telescopes.

Image Credit: NASA, ESA, and B. Mobasher (STScI/ESA)

26th September, 2005: The Baby-Boomer Galaxies

To measure the distance of a far-away galaxy requires that we measure its red-shift - and to do this we need to observe its spectrum. However, to do so requires a long exposure even with a large telescope since these galaxies are often extremely faint. To avoid using large amounts of valuable observatory time astronomers had to carefully select candidate high red-shift galaxies. It turns out, however, that they were a bit too selective in the past and this led them to build a rather biased view of the population of galaxies in the early Universe.

Now astronomers have used the VIsible Multi-Object Spectrograph (VIMOS) on one of the 8.2 metre telescopes of the ESO Very Large Telescope Array (VLT) to make an unbiased survey of early epoch galaxies. With VIMOS, astronomers can observe the spectra of 1000 galaxies simultaneously allowing them to perform an observation that would've taken several months in the past in only a few hours.

Equipped with VIMOS, astronomers measured the spectra of about 8000 galaxies which were selected only because of their brightness in red light. When the sample was studied they found almost 1000 bright star forming galaxies at an epoch between 1500 and 4500 million years after the Big Bang. This is two to six times more than found in previous such studies!

This discovery goes against previous observations and models which have consistently indicated that the early Universe had not yet formed many stars. By combining the spectra of galaxies in a given epoch, astronomers found that the galaxies in the young Universe transformed in the order of 10 to 100 solar masses of material into stars each year. This implies that galaxies formed many more stars in the early Universe than was previously thought. It now remains for cosmologists to explain how our Universe created such a large number of high-star-producing galaxies when it was only 1.5 to 3 billion years old.

A colour-composite image indicating some of the newly found galaxies (circled) based on VMMOS/VLT data.

Image Credit: LAM-OAMP/CFHT

19th September, 2005: Big Science on a Shoestring

A few years ago Mr. David Brodrick, at CSIRO's Australian Telescope National Facility (ATNF) and also a masters student at Swinburne University of Technology, built a low-cost (~AU$155), simple, low-frequency radio interferometer which he aptly called "SIMPLE". Using SIMPLE he was able to detect strong radio sources such as the Sun, Jupiter and the galactic centre of the Milky Way as they passed overhead - this made it an interesting display at the Australia Telescope Compact Array (ATCA) Visitor Centre in Narrabri where he continued to record the data observed by SIMPLE. The true power of SIMPLE became evident on November 4 2003 after a sudden release of magnetic energy in the Sun's atmosphere caused the largest x-ray solar flare ever seen from the Sun - so powerful that it effectively blinded x-ray detectors on the National Oceanic and Atmospheric Administrations GEOS-12 satellite for a period of 12 minutes. This left a gaping hole in our records with regards to the actual peak flux and timing of the blast. Now, when a blast of x-rays such as this hits the Earth's atmosphere it ionises atmospheric molecules making them more opaque to low-frequency radio waves. From a SIMPLE point-of-view this meant that the signals it normally received at that time of day would have been partially absorbed by the atmosphere - the level of absorption being related to the incident X-ray flux. Together with his supervisors Dr Steven Tingay (Swinburne University of Technology) and Dr Mark Wieringa (ATNF) they compared the November 4 2003 data with historical data that David had recorded on more "quiet" days in order to measure the the variation of low-frequency radio opacity throughout the flare period. From this they could indirectly determine the x-ray flux at each point in time that would be required to cause this level of opacity and so fill in the missing flux measures for the period during which the GEOS-12 instruments were saturated.

The final results of this research found that the November 4 2003 flare was in fact 70% more powerful and peaked earlier than previous estimates had suggested. To give a sense of scale, the blast released enough energy to supply the entire world for over 300,000 years at our current rate of consumption! Their results are described in the paper X-Ray Magnitude of the November 4 2003 Solar Flare Inferred from the Ionospheric Attenuation of the Galactic Radio Background published in the Journal of Geophysical Research and Space Physics on 9 September, 2005.

So, if you're a budding radio astronomer and are interested in the possibility of one day making your own big discovery then check out the Radio Jove web site and of course the Fringe Dwellers web site to which David has been contributing.

A graph showing the X-ray flux measured by SIMPLE over the duration of the November 4 2003 solar x-ray flare.

Image Credit: ATNF/Swinburne

12th September, 2005: Comet Tempel 1 Update

The initial impact showed that comet Tempel 1, like the possum in my roof, has a fluffy structure and that it is only weakly held together by its feeble gravity. It is believed that the fluffy and porous nature of the comet may act as an effective insulator protecting the comet interior from solar heating and leaving its internal composition as it was when it first formed. Some of these materials would've been released when the impactor hit the comet. Spectral analysis of the resulting debris cloud has shown, coincidentally once again like a possum, that comet Tempel 1 contains a substantial quanitity of organic materials. This adds weight to the theory that materials such as these may have been brought to the Earth by comets soon after its formation. This provided our world with the building blocks required to form primitive life-forms that would in time evolve into humans and roof-dwelling possums.

The big surprise for scientists was the detection of clay and carbonates. These materials are believed to require the presence of water to form - a problem considering that comets were formed in the icy depths of space. This suggests that the primordial solar system may have somehow been "mixed" to allow material formed near the sun and frozen material in the outer solar system to be included in the same body. Another surprise was the detection of iron-bearing compounds and aromatic hydrocarbons, materials not previously observed on comets and more at home in barbecue pits and car exhausts. The presence of these materials will provide a good test for planet formation models which now need to account for these molecules.

Astronomers have also been taking a closer look at comet Tempet 1 images before the impact. A composite picture built from images taken by the impactor probe has helped to highlight a number of interesting features. The first is the presence of impact craters, this is the first time impact craters have been observed on a cometary nucleus. The images also show a terrain that varies widely from smooth features (as pointed to by arrows "a" and "b" below) to the extremely rough terrain around the impact craters.

These are just some of the preliminary results obtained so far and there is still plenty more data to process so stay tuned for more results in future!

Please note that no possums were harmed during the writing of this article and that the R.S.P.C.A. does not condone deep impact tests with any fluffy creatures - regardless of ones scientific motives!

A composite image of comet Tempel 1. Arrows "a" and "b" point to large, smooth regions of the comet. The unmarked large arrow points to the impact site of the deep impact probe. The smaller arrows highlight a scarp in which the smooth area is elevated above the surrounding rough terrain.

Image Credit: NASA/JPL

5th September, 2005: Mars - View from a hill

Spirit rover has now clocked over 4,827 metres on its odometer, whilst it's fellow explorer Opportunity has now clocked in excess of 5,737 metres. Both rovers are running strong and appear to be in excellent shape.

NASA Spirit rover image from on top of Husband Hill.

Image Credit: NASA/JPL

29th August, 2005: SN1987A - The X-Ray show begins!

Since the first detection of SN1987A, astronomers have been using observations at optical, ultraviolet and X-ray wavelengths to build a history of events that led to the explosion of Sanduleak -69º 202 (A.K.A. SK-69), a blue supergiant star believed to be the progenitor star of SN1987A. SK-69 formed about 10 million years ago from a dark and dense cloud of gas and dust. As it aged, it blew off much of its outer layers of gas away in a stellar wind and formed a large cloud of gas around the star. Just before SK-69 went supernova it developed a high-speed wind which blew off its hot surface and swept out a cavity in the cool gas cloud.

When SK-69 went supernova it released an intense flash of ultraviolet light that illuminated the inner edge of the cavity - this was captured by the Hubble Space Telescope (HST) a few years after the supernova event. Since then astronomers have anticipated a spectacular X-ray light show once the shock wave from the initial blast collides with the dense circumstellar gas at the inner edge of the cavity. Recent observations from the Chandra X-ray telescope and the HST indicate that this event has now begun!

Chandra X-ray and HST optical image of SN1987A.

Image Credit: X-ray: NASA/CXC/PSU/S.Park & D.Burrows.; Optical: NASA/STScI/CfA/P.Challis

As an intersting aside, SN1987A was also the first supernova from which a burst of neutrinos (well, actually anti-neutrinos to be precise) was detected. The observation was made by Japans Kamiokande II neutrino observatory three hours before the first sighting of the supernova light. This not only provided conclusive evidence for the correctness of the core collapse mechanism but also helped to provide limits on the mass of the neutrino - it was a win for stellar AND particle physics!

22nd August, 2005: Getting to know our own Milky Way

To peer deep through the layers of gas and dust requires observations at longer wavelengths such as those available with radio or infrared telescopes. Previous radio surveys of our galaxy have helped to identify its spiral structure and the locations of many of its arms. Now, NASA's Spitzer Space Telescope has been used by astronomers to conduct the most comprehensive structural analysis of the galaxy to date by surveying 30 million stars in the plane of the galaxy.

One of the most dramatic findings was the confirmation of a long stellar bar at the centre of our galaxy with a length of approximately 27,000 light years. This is 7,000 light years longer than previously expected and is a feature that distinguishes our galaxy from your typical "run of the mill" spiral galaxy.

An artist's rendering of our Milky Way based on recent observations from the Spitzer Space Telescope.

Image Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

15th August, 2005: Getting to know NGC 300

Well now the Aussies want to get in the act too! A team of Australian and American astronomers have used the Gemini Observatory in Hawaii to discover that NGC 300 is twice as large as previously thought. The team took extremely deep images of the outskirts of NGC 300 and were able to resolve stars 47,000 light years from the galaxy's centre - the first such study for a galaxy outside of the Local Group. These stars are old and faint today but would've shone as brightly as those in the inner suburbs of the galaxy a few billion years ago. This discovery has profound implications for our own galaxy, the Milky Way. Previous estimates of the diameter of the Milky Way are around 100,000 light years - about the same as the newly estimated diameter of NGC 300, yet the Milky Way is more massive. It is quite possible that the Milky Way also has old and faint stars at its outskirts extending its diameter to 200,000 light years.

The finding has also raised an interesting problem. It was believed that when galaxies formed they would produce a stellar disk that cuts off abruptly in density at a certain distance from the centre. However, the stellar disk of NGC 300 drops off smoothly in density and just seems to go on forever. Further investigations will be required to solve this problem.

A wide-field view of NGC 300.

Image Credit: AAO-David Malin/Gemini Observatory

8th August, 2005: Black holes unveiled

For years, astronomers have wondered how many super-massive black holes there are out there. Since quasars outshine everything else in the Unvierse in X-rays, one way to get a feel for their number is to measure the cosmic X-ray background. However, these estimates have resulted in numbers that are far greater than the amount of observed quasars. Astronomers speculated that some quasars were oriented in such a manner that their dusty torus was hiding their light. Some quasars may even be totally hidden behind a dust-filled galaxy.

To detect these hidden quasars, astronomers have made use of NASA's Spitzer Space Telescope to search a small area of the sky with its infrared eyes. Infrared light, unlike visible light and X-rays, can travel through gas and dust and so allows us to probe further into a galaxy. Using this technique they found 21 of these shrouded quasars, which when extrapolated for the entire sky could account for the quasars not previously detected. The quasar nature of these sources was also verified using the Very Large Array (VLA) radio telescope.

A false-colour Spitzer Space Telescope image shows a distant galaxy (yellow) that houses a super-masive black hole.

Image Credit: NASA/JPL-Caltech/A. Martinez-Sansigre (Oxford University)

1st August, 2005: Welcome to SAO Semester 2, 2005

Welcome to SAO semester 2, 2005!

As always the wheels of progress do not grind to a halt during the SAO semester breaks. Over the past few weeks a number of major milestones (approx. 1.609344 kilometre-stones) have been achieved. First and foremost is the launch of the US Space Shuttle Discovery. After an initial two week delay caused by a mysterious fuel sensor glitch, Space Shuttle Discovery lifted off from the Kennedy Space Center at 14:39 UT on the 26th of July. This time around all aspects of the launch were observed with cameras on the ground, on the external fuel tank and on chase planes. Unfortunately, in a haunting echo of events that led to the loss of the Space Shuttle Columbia 2.5 years ago, large sections of foam peeled away from Discovery's external fuel tank during the launch. On the positive side, NASA has learnt from the past and so shuttle astronauts will perform a detailed inspection of the shuttle's nose cap and wing leading edge panels to check for damage - so far the word is that the shuttle is in good shape for a safe return home. If damage is detected then the astronauts are can perform basic DIY repairs using new repair kits that they now carry onboard the shuttle.

Launch of the NASA Space Shuttle Discovery.

Image Credit: NASA/KSC

In other BIG news, on July 4th NASA's Deep Impact mission has left its mark on Comet Tempel 1. A day earlier Deep Impact released a 370kg impactor probe towards the comet travelling at a speed of approximately 10.2 km/s relative to the comet. On impact, the probe delivered about 19 Gigajoules of kinetic energy into the comet creating a larger than expected plume of debris in the process. This plume was observed by the Hubble Space Telescope, ESA's Rosetta spacecraft, the Submillimeter Wave Astronomy Satellite (SWAS), Spitzer, Swift and a plethora of optical and radio telescopes here on Earth in an effort to determine its composition. The Deep Impact spacecraft also gazed at the aftermath of the impact in an effort to determine the size of the impact crater, unfortunately its view was obscured by the resulting plume. NASA has placed the Deep Impact spacecraft in an orbit that preserves options for future use of the spacecraft.

The Deep Impact flyby spacecraft looks back to observe the plume of material ejected fifty minutes after the impactor hit the comet.

Image Credit: NASA/JPL-Caltech/UMD

Meanwhile at Mars it's BOOM-TIME! The European Space Agency's Mars Express spacecraft has successfully deployed all three of its MARSIS radar booms. The deployment was initially delayed because of fears that the booms may swing back after deployment and hit the spacecraft. Mission controllers received an initial fright when the first boom did not appear to lock into position but after some quick and smart thinking on their side they realized that as a result of exposure to the cold temperatures there the boom had contracted slightly. Their solution was to heat up the boom by facing it towards the Sun, this caused the boom to expand and lock into place. Since then the two remaining booms have also been deployed. The MARSIS instrument will act like a RADAR to probe the planets surface and subsurface structure at night and to probe the structure of the upper atmosphere by day. It is hoped that the instrument will help find evidence of subsurface deposits of water.

In other Mars news, Mars rover Opportunity has FINALLY escaped the grip of deep Martian sand on Meridani Planum after almost a month of nervous moments. During this period its wheels turned the equivalent of 192 metres and yet the rover moved forward only a few centimetres. Both Spirit and Opportunity are now continuing their journey of discovery and we can expect to hear a great deal more from them over the next few months.

Mars Exploration Rover Opportunity looks back at the trecherous sands of 'Pergatory Dune'.

Image Credit: NASA/JPL

Last but not least is the announcement by NASA that a tenth planet has been discovered in the outer Solar System. The object designated by the memorable and romantic name of "2003UB313" is 97 times further from the Sun than the Earth (or about 3 times further from the Sun than Pluto) and is estimated to be approximately 1.5 times larger than Pluto. The object is a typical member of the Kuiper belt and is not unlike previously discovered Kuiper objects such as Sedna, Quaoar, Ixion and Varuna - but it is the first found to be larger than Pluto. A new name for the planet has been proposed to the International Astronomical Union and will be announced after it has been approved.

A time-lapse image of "2003UB313" taken 90 minutes apart using the Samuel Oschin Telescope at the Palomar Observatory.

Image Credit: Samuel Oschin Telescope, Palormar Observatory