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 observe a distant
star by using the world’s research networks to create a giant virtual telescope.
The process has allowed them to image the object with unprecedented detail, in
real-time; something which only a few years ago would have been impossible. The
star chosen for this remarkable demonstration, called IRC+10420, is one of the
most unusual in the sky. Surrounded by clouds of dusty gas and emitting strongly
in radio waves, the object is poised at the end of its life, heading toward a
cataclysmic explosion known as a ‘supernova’.

These new observations give an exciting glimpse of the future of radio
astronomy. Using research networks, not only will radio astronomers be able to
see deeper into the distant Universe, they’ll be able to capture unpredictable,
transient events as they happen, reliably and quickly.

Astronomers are always seeking to maximise the resolution of their telescopes.
Resolution is a measure of the amount of detail it can pick out. The bigger the
telescope, the better the resolution. VLBI (or Very Long Baseline
Interferometry) is a technique used by radio astronomers to image the sky in
supreme detail. Instead of using a single radio dish, arrays of telescopes are
linked together across whole countries or even continents. When the signals are
combined in a specialised computer, the resulting image has a resolution equal
to that of a telescope as large as the maximum antenna separation.

In the past, the VLBI technique was severely hampered because the data had to be
recorded onto tape and then shipped to a central processing facility for
analysis. Consequently, radio astronomers were unable to judge the success of
their endeavours until many weeks, even months, after the observations were
made. The solution, to link the telescopes electronically in real-time, enables
astronomers to analyse the data as it happens. The technique, naturally called
e-VLBI, is only possible now that high-bandwidth network connectivity is a reality.

The recent 20-hour long observations, performed on 22nd September using the
European VLBI Network (EVN), involved radio telescopes in the UK, Sweden, the
Netherlands, Poland and Puerto Rico. The maximum separation of the antennas was
8200 km, giving a resolution of at least 20 milliarcseconds (mas); this is about
5 times better than the Hubble Space Telescope (HST). This level of detail is
equivalent to picking out a small building on the surface of the moon! The
inclusion of the antenna at Arecibo, in Puerto Rico, also increased the
sensitivity of the telescope array by a factor of 10. Even so, observing at a
frequency of 1612 MHz, the signal from the distant star was more than a billion
billion times weaker than a typical mobile phone handset!

Each telescope was connected to its country’s National Research and Education
Network (NREN), 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), the
central processing facility for the EVN in the Netherlands. There, 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 image.
Until the network infrastructure provided GEANT became available, astronomers
were unable to transfer the huge amounts of data required for e-VLBI across the
Internet. In a very real sense, the Internet itself acts like a telescope,
performing the same job as the curved surfaces of the individual radio dishes.
Dai Davies, General Manager of DANTE who operate GEANT, said: “e-VLBI performed
successfully on an intercontinental basis demonstrates in the clearest possible
terms the importance of data communications networks to modern science. Research
networking is fundamental to this new radio astronomy technique and it is very
satisfying indeed to see the benefits that are now resulting from it”.

Although the scientific goals of the experiment were modest, these e-VLBI
observations of IRC+10420 open up the possibility of watching the structures of
astrophysical objects as they change. IRC+10420 is a supergiant star in the
constellation of Aquila. It has a mass about 10 times that of our own Sun and
lies about 15,000 light years from Earth. One of the brightest infrared sources
in the sky, it is surrounded by a thick shell of dust and gas thrown out from
the surface of the star at a rate of about 200 times the mass of the Earth every
year. Radio astronomers are able to image the dust and gas surrounding IRC+10420
because one of the component molecules, hydroxyl (OH), reveals itself by means
of strong ‘maser’ emission. Essentially, the astronomers see clumps of gas where
radio emission is strongly amplified by special conditions. With the zoom lens
provided by e-VLBI, astronomers can make images with great detail and watch the
clumps of gas move, watch masers being born and die on timescales of weeks to
months, and study the changing magnetic fields that permeate the shell. The
results show that the gas is moving at about 40 km/s and was ejected from the
star about 900 years ago. As Prof. Phil Diamond, one of the research team at
Jodrell Bank Observatory (UK), explained, “the material we’re seeing in this
image left the surface of the star at around the time of the Norman Conquest of
England”.

It is believed IRC+10420 is rapidly evolving toward the end of its life. At some
point, maybe thousands of years from now, maybe tomorrow, the star is expected
to blow itself apart in one of the most energetic phenomena known in the
Universe — a ‘supernova’. The resulting cloud of material will eventually form
a new generation of stars and planetary systems. Radio astronomers are now
poised, with the incredible power of e-VLBI, to catch the details as they happen
and study the physical processes that are so important to the structure of our
Galaxy and to life itself.

The emergent technology of e-VLBI is set to revolutionise radio astronomy. As
network bandwidths increase, so too will the sensitivity of e-VLBI arrays,
allowing clearer views of the furthest and faintest regions of space. Dr Mike
Garrett, JIVE Director, commented, “These results provide a glimpse of the
enormous potential of e-VLBI. The rapid progress in global communications
networks should permit us to connect together the largest radio telescopes in
the world at speeds exceeding tens of Gigabits per second over the next few
years. The death throes of the first massive stars in the Universe, the emerging
jets of matter from the central black-holes of the first galaxies, will be
revealed in exquisite detail.”

Related Websites

* DANTE http://www.dante.net/

* GEANT http://www.dante.net/server/show/nav.007

* European VLBI Network (EVN) http://www.evlbi.org/

* Joint Institute for VLBI in Europe (JIVE) http://www.jive.nl/

* Particle Physics and Astronomy Research Council (PPARC) http://www.pparc.ac.uk/

[NOTE: Images supporting this release are available at http://www.jb.man.ac.uk/news/evlbi/]