PRESS RELEASE – Monday 4th October 2004
Astronomers Demonstrate aGlobal Internet Telescope
European and US radio astronomers have demonstrated a new way of observing the Universe – through the Internet!
Using cutting-edge technology, the researchers have managed to observeboth a distant star and the "monster in the middle" of a galaxy faraway from our Milky Way. For this, they have used the world's researchcomputer networks to create a giant virtual telescope. This allowsimaging of the objects with unprecedented detail, and in real-time, which would have been impossible only a few years ago.
The star chosen for this remarkable demonstration, IRC+10420, isone of the most unusual in the sky. Surrounded by clouds of dusty gasand emitting strongly in radio waves, the object is poised at the endof its life, heading toward a cataclysmic explosion known as a'supernova'. In contrast, the active galactic nucleus studied is thatof the galaxy 3C166, situated 3.2 billion light years from the Earth.
These new observations give an exciting glimpse of the future of radio astronomy. Using research networks, astronomers will be ableto see deeper into the distant Universe and captureunpredictable, transient events as they happen.Astronomers always seek to improve the resolving power of theirtelescopes, maximising the detail that can be seen; thebigger the telescope, the better the resolution. VLBI (or Very LongBaseline Interferometry) is used by radio astronomers toimage the sky in supreme detail. Instead of using a single radio dish,arrays of telescopes are linked together across whole countries or evencontinents. When the signals are combined in a specialised computer,the resulting image has a resolution equal to that of a telescope asbig as the maximum antenna separation.
Until now, VLBI has been severely hampered because the data had to berecorded onto tape and then shipped to a central processing facilityfor analysis. Consequently, radio astronomers were unable to judge thesuccess of their endeavours until weeks or months after theobservations were made. The solution, to link the telescopeselectronically in real-time, now enables them to analyse the data as itarrives. This technique, naturally called e-VLBI, is now possible ashigh-bandwidth network connectivity has become a reality.
On 22nd September, 20-hour long observations using the European VLBINetwork (EVN) involved radio telescopes in the UK, Sweden, theNetherlands, Poland and Puerto Rico. The maximum separation of theantennas was 8200 km (Puerto Rico to Poland), giving a resolutionbetter than 20 milliarcseconds (mas), about 5 times better thanthe Hubble Space Telescope (HST). This level of detail is equivalent topicking out a small building on the surface of the Moon! The inclusionof the huge 305-meter diameter antenna at Arecibo †, Puerto Rico, increased the sensitivity of the telescope array by a factor of 10.Even so, the signal from the distant star was more than a billionbillion times weaker than a typical mobile phone handset!
Each telescope was connected to its country's National Research and Education Network , and the data routed at 32 Mbits/second per telescope through GEANT, the pan-European research network, to SURFnet, the Dutch network. The data were then delivered to the Joint Institute for VLBI in Europe (JIVE) in the Netherlands, where the 9 Terabits of data were fed in real-time into a specialised supercomputer, called a 'correlator', and combined. The same research networks were then used to deliver the final data product directly to the astronomers who formed the images. Until the network infrastructure provided by GEANT became available, astronomers could not transfer thehuge amounts of data required for e-VLBI across the Internet. In a sense, the Internet itself acts like a telescope, performing thesame task as the curved surfaces of the individual radio dishes. DaiDavies, General Manager of DANTE who operate GEANT, said, "Research networking is fundamental to this new radioastronomy technique and it is very satisfying to see thebenefits that are now resulting from it".
Although the scientific goals of this experiment were modest, thee-VLBI observations of IRC+10420 open up the possibility of watchingthe structures of astrophysical objects as they change. IRC+10420 is asupergiant star in the constellation of Aquila and is one of the brightest celestial infrared sources. It has a mass about 10times that of the Sun and lies about 15,000 light years from Earth.It is surrounded by athick shell of dust and gas thrown out from the surface of the star ata rate of about 200 times the mass of the Earth every year. Radioastronomers are able to image the dust and gas surrounding IRC+10420because one component molecule, hydroxyl (OH), reveals itself by meansof strong 'maser' emission.Essentially, the astronomers see clumps ofgas where radio emission is strongly amplified by special conditions.With the zoom lens provided by e-VLBI, astronomers can make images withgreat detail and watch the clumps of gas move, see masers being bornand die on timescales of weeks to months, and study the changingmagnetic fields that permeate the shell. The results show that the gasis moving at about 40 km/sec and was ejected from the star some 900years ago.
It is believed that IRC+10420 is rapidly evolving toward the end of itslife. At some point, maybe thousands of years from now, maybetomorrow, the star is expected to blow itself apart in one of the mostenergetic phenomena known in the Universe - a 'supernova'. Theresulting cloud of material will eventually form a new generation ofstars and planetary systems. With the incredible power of e-VLBI,radio astronomers are now poised, to catch the details as they happenand study these physical processes that are so important to thestructure of our Galaxy and to life itself.
More distant, and on a larger scale, the galaxy 3C166 contains anactive nucleus which is feeding material from the center of thegalaxy, through narrow "jets", to huge emission lobes situated faroutside of the galaxy itself. The active nucleus, or "central engine"as it is often known, is believed to contain a super-massive black holeproviding the energy to power the out-flowing jets. In the accompanyingfigure, the very center of the galaxy is imaged, and the majority ofthe radio emission is found to originate in a region that is smaller than 88 light years, emphasising the presence of a highly compact object, believed to be theblack hole.
The emergent technology of e-VLBI is set to revolutionise radioastronomy. As network bandwidths increase, so too will the sensitivityof e-VLBI arrays, allowing clearer views of the furthest and faintestregions of space. Dr Mike Garrett, JIVE Director, commented, "Theseresults provide a glimpse of the enormous potential of e-VLBI. Therapid progress in global communications networks should permit us toconnect together the largest radio telescopes in the world at speedsexceeding tens of Gigabits per second over the next few years. Thedeath throes of the first massive stars in the Universe, the emergingjets of matter from the central black-holes of the first galaxies, willbe revealed in exquisite detail."
†The Arecibo Observatory is part of the National Astronomy and IonosphereCenter, which is operated by CornellUniversity under a cooperative agreement with the National Science Foundation.
Figure 1: (left) A low-resolution image of IRC+10420 taken with the UK’s MERLIN radio telescope array shows the shell of ‘maser’ emission at a frequency of 1612 MHz. The corresponding EVN e-VLBI image (right) shows much finer structure of the masers due to the longer telescope baselines. The expanding shell of gas revealed by these observations has a diameter about 200 times that of our own Solar System. The gas is moving at about 40 km/s and was ejected by the star about 900 years ago. The study of the dynamics and chemistry of these gas shells enable astronomers to investigate the production of chemical elements important for star and planet formation, and ultimately life itself.
Figure 2: The spectrum of IRC+10420 (a plot of signal strength as it changes with frequency of the radio waves), as observed during the EVN e-VLBI observations of 22nd September. The total velocity width of the emission shows that the shell of IRC+10420 is expanding at about 40 km/s.
Figure 3: A transatlantic e-VLBI image of the nuclear region of the radio galaxy 3C166. The distance of this object is 3.2 billion light years, and its size is less than 88 light years. A super massive black hole is believed to reside in the center of this strong radio galaxy.
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